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The Protective Role of Helminths in Autoimmunity
CHAPTER 12
The Protective Role of Helminths in Autoimmunity Tomer Bashi, Tom Konikoff, Miri Blank, Yehuda Shoenfeld,1 *
Zabludowicz Center For Autoimmune Diseases; Sheba Medical Center; Tel-Aviv University; Ramat Gan, Israel Corresponding Author: [email protected]
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1 INTRODUCTION For the past several decades, Western industrialized countries are facing a high rate of autoinflammatory disorders, which are being expressed by higher prevalence of autoimmune diseases and allergies.1,2 The lifestyle in industrialized countries had led to a decrease of infectious burden; however, a reverse correlation has been seen with the prevalence of autoimmune diseases.3 Limited exposure to microorganisms such as helminths and microbes during childhood eventually leads to an off-balanced immune system. This theory, known as the Hygiene Theory or the Hygiene Hypothesis, was first proposed by Strachan, who observed an inverse correlation between hay fever and the number of older siblings while following more than 17,000 British children born in 1958.4–6 In addition to the eradication of worms in the Western world, eradication of helminths increased atopic skin sensitization in Venezuela,7 in Gabon,8 and in Vietnam.9 For example, the prevalence of malaria is in reverse correlation to autoimmune diseases; several sources of epidemiological and immunogenetic evidence link the disappearance of malaria because of societies’ eradication programs with the increase of multiple sclerosis (MS) in Sardinia, due to the high genetic susceptibility of human leukocyte antigen DR3 within the island.10–13 Moreover, the contribution of helminths to the development of autoimmune diseases also was demonstrated in the Karelian region. Finland’s Karelian maintains have one of the highest prevalences of autoimmune and allergic diseases, whereas the prevalence in the Russian Karelian region is far lower. The fact that the Russian section is rife with infections and the Finnish part is dramatically cleaner has a large impact on the difference in prevalence.14,15 Infection and Autoimmunity http://dx.doi.org/10.1016/B978-0-444-63269-2.00012-X
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Helminths aim is to survive in the host; therefore they try to induce a tolerance scenario. Yet it is important to keep in mind that immunomodulation is affected by several key elements such as the burden of the infection and the host’s immune system. In most cases helminths induce tolerance, but in some scenarios they may cause an inflammatory response. The spectrum of affliction in chronic helminthic tissue infection contains low pathology with high parasite burden and chronic disease with low parasite burden. For example, in areas where schistosomiasis and filarial diseases are endemic, some individuals develop chronic debilitating pathologies and others show a tolerant phenotype. The tolerant phenotype is characterized by the production of anti-inflammatory cytokines such as transforming growth factor (TGF)-b and interleukin (IL)-10 and increased number of FoxP3+ T regulatory cells (Tregs). These cytokines lead to suppressed parasitespecific T-cell proliferation in peripheral blood mononuclear cells, reduced levels of T helper (Th) 2 cytokines, and ablated Th1 cytokines. Thus, the parasite survives productively in the host with minimal collateral damage.16,17
2 THE PROTECTIVE ROLE OF HELMINTHS IN AUTOIMMUNE DISEASES 2.1 Helminths and Inflammatory Bowel Disease Ulcerative colitis (UC) and Crohn’s disease (CD) are two medical conditions collectively called inflammatory bowel disease (IBD). They involve an excess Th1 immune response towards the intestinal cells.18,19 UC and CD are classified as separate diseases because each exhibits several distinguishing clinical and pathological features. UC has higher incidence of rectal involvement and the lesions are continuous, whereas CD contains skipped regions of lesions, terminal ileal ulceration, fistulization and/or anal fissuring and longitudinal ulcerations. In the late 1990s, Elliott et al.20 raised the IBD ‘hygiene hypothesis’ based on the increasing prevalence of IBDs in the United States and the fact it is in contrast to the prevalence of helminths in the USA. They proposed that exposure to helminths might protect against IBDs. In sub-Saharan Africa, low incidence and prevalence of IBD was observed and cannot be explained by genetic factors because in black populations in the USA and the UK, the incidence of IBDs is approaching that of white populations.21 Researchers attribute this fact to the ability of helminths to influence the composition of the microbiome, downmodulate
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the secretion of proinflammatory cytokines, upregulate Tregs and switch the immune response from Th1 to Th2, thus reducing inflammation in IBDs.22–29 Helminths, their ova and their antigens have been used in many studies that tried to treat IBDs in murine models and in human cases. Colonization of Heligmosomoides polygyrus in IL-10 knockout mice with piroxicam-induced colitis suppressed the production of IL-17 by lamina propria mononuclear cells and improved colitis.30–32 Schistosome ova exposure attenuated 2,4,6-trinitrobenzene sulfonic acid colitis and protected mice from lethal inflammation. Interferon (IFN)-g levels were reduced, whereas IL-4 and IL-10 messenger RNA levels were enhanced because of production by aCD3-stimulated spleen and mesenteric lymph node.33–36 Murine studies have led to human therapy trials with helminth ova: (1) A study conducted in the early 2000s suggested that Trichuris suis (pig whipworm) seemed to be safe and possibly effective in the treatment of IBD. T. suis met safety requirements. The pig is a natural host for T. suis; it can colonize people but only for a short length of time.37 A single dose of T. suis ova (TSO; up to 7500 ova) was well tolerated and did not result in short- or long-term treatment-related side effects.38 (2) Summers et al.39 studied four patients with active CD and three with UC. In an initial treatment and observation period, a single dose of 2500 live TSO was given orally, and patients were followed every 2 weeks for 12 weeks. To assess safety and efficacy with subsequent doses, two patients with CD and two with UC were given 2500 ova at 3-week intervals as maintenance. Patients with UC experienced a reduction of the Clinical Colitis Activity Index to 57% of baseline. According to the IBD Quality of Life Index, 6 of 7 patients (86%) achieved remission. The benefit was temporary in some patients with a single dose, but it could be prolonged with maintenance therapy every 3 weeks. (3) Another study using TSO also conducted by Summers et al.,40 involved 29 patients with active CD. All patients ingested 2500 live TSO every 3 weeks for 24 weeks, and disease activity was monitored using the Crohn’s Disease Activity Index (CDAI). The results were impressive: At week 24, 23 patients (79.3%) responded (decrease in CDAI by >100 points or a CDAI <150) and 21 of 29 patients (72.4%) remitted (CDAI <150). (4) In a randomized, double blind, placebo-controlled trial including 54 patients with active colitis, defined by Disease Activity Index (DAI)
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of 4, patients received 2500 TSO or placebo orally at 2-week intervals for 12 weeks. The primary efficacy variable was improvement of the DAI to 4. After 12 weeks of therapy, improvement according to the intent-to-treat principle occurred in 13 of 30 patients (43.3%) receiving ova treatment compared with 4 of 24 patients (16.7%) given placebo (P ¼ .04). Improvement also occurred with the Simple Index, which was significant by week 6.41,42 It is important to mention one case report regarding iatrogenic infection by T. suis in a 16-year-old adolescent with CD who was treated with TSO. He received 5 oral doses of 2500 TSO off protocol. When admitted to the hospital, pathologic evaluation showed several round helminthic forms directly beneath attenuated ileocecal mucosal epithelium—the helminths from the TSO had evolved in his intestine.43 As for antigens, treatment with Trichinella spiralis frozen skeletal muscle larvae before inducing colitis with dinitrobenzene sulfonic acid significantly reduced the severity of colitis; downregulated myeloperoxidase activity, IL-1b production, and inducible nitric oxide synthase expression; and an upregulated IL-13 and TGF-b production in the colon in a mouse model.44 Furthermore, the use of antagonists of Toll-like receptor (TLR) signaling and agonists of their negative regulators from helminths or helminth products should be considered for the treatment of IBD because TLR signaling may contribute to destructive host responses and chronic inflammation, whereas helminths may play an important role in the downregulation of gene activation in controlling overwhelming inflammation and proinflammatory cytokine production.45
2.2 Helminths and Multiple Sclerosis MS is an inflammatory, demyelinating, neurodegenerative disorder of the central nervous system (CNS) of unknown etiology. The most common clinical signs and symptoms, occurring in isolation or in combination, include sensory disturbance of the limbs (30%), partial or complete visual loss (15%), acute and subacute motor dysfunction of the limbs (13%), diplopia (7%) and gait dysfunction (5%). The impact of MS on an individual is variable, but one constant feature is the uncertainty of this disease.46,47 The incidence of MS has significantly increased during the second half of the 20th century. Caucasian individuals from Northern Europe are more
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prone to have the disease, while it is rare among Asians and Africans, with a low prevalence in tropical regions, indicating the importance of environmental factors such as helminths. The incidence increases as distance north of the equator lengthens.48,49 It was mentioned earlier that the eradication of malaria in Sardinia was preceded by the increase in the prevalence of MS on the island because of the high genetic susceptibility of human leukocyte antigen DR3 there.10,11 The most frequently studied animal model of MS is experimental autoimmune encephalitis (EAE), which mimics several of the key clinical and pathological features of the human disease, such as paralysis and demyelination.50 Percutaneously infection of Schistosoma mansoni cercariae in mice significantly reduced the incidence and delayed the onset of EAE in a mouse model. Production of IFN-g, nitric oxide, and tumor necrosis factor (TNF)-a by splenocytes was significantly reduced.51 Taenia crassiceps cysticerci (a 40 metacestodes infection load) also was able to reduce the severity of EAE. Only 50% of T. crassiceps-infected mice displayed EAE symptoms, which were significantly (P < 0.05) less severe than in uninfected mice. This effect was associated with both decreased myelin oligodendrocyte glycoprotein–specific splenocyte proliferation and IL-17 production and limited leukocyte infiltration into the spinal cord. Infection with T. crassiceps induced an anti-inflammatory cytokine microenvironment, including decreased TNF-a production and high myelin oligodendrocyte glycoprotein–specific production of IL-4 and IL-10.52 To prove the beneficial effect of helminths on patients with MS, Correale and Farez performed several studies. In a prospective doublecohort study, 12 patients (8 female and 4 male patients) with a clinical diagnosis of MS were assessed. The 12 patients with MS were infected with several helminth species (Hymenolepis nanan, Trichiuris trichura, Ascaris lumbricoides, Strongyloides stercoralis and Enterobius vermicularis); each patient was infected with one species. A control group containing healthy subjects was also infected with helminths, and another 12 uninfected patients with MS in remission matched for age, sex, and disease duration served as control subjects. It was shown that parasite-infected patients with MS had significantly fewer exacerbations, minimal variation in disability scores, as well as fewer magnetic resonance imaging (MRI) changes when compared with uninfected patients with MS.53,54 Moreover, responses to myelin basic protein peptide–specific T-cell clones were tested for cytokine secretion in peripheral blood and showed a significant increase (P < 0.0001) in the anti-inflammatory cytokines
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IL-10 and TGF-b and a decrease in cells secreting proinflammatory cytokines IL-12 and IFN-g in infected patients with MS compared with noninfected patients. Myelin basic protein–specific T-cells cloned from infected subjects were characterized by the absence of IL-2 and IL-4 production but high IL-10 and/or TGF-b secretion. In addition, the cloning frequency of CD4 + CD25+ FoxP3+ Tregs from those patients was increased (P < 0.0001) in infected patients compared with uninfected subjects with MS.53,54 Investigation of B-cell-mediated control mechanisms occurring during parasite infections in patients with MS demonstrated that helminthic infections (H. nanan, T. trichura, A. lumbricoides, S. stercoralis and E. vermicularis) cause a B-cell population producing high levels of IL-10, thus inhibiting harmful autoinflammatory immune responses. Moreover, B cells isolated from patients with MS infected with helminths also produced greater amounts of brain-derived neurotrophic factor and nerve growth factor, which is a type of protein that is important for the growth, maintenance, and survival of nerve cells, compared with healthy subjects and uninfected individuals with MS, raising the possibility that these cells may exert certain neuroprotective functions on the CNS. Hence, in addition to their immune-modulatory effect, helminths possess other beneficial aspects, such as promoting the growth of nerve cells.55 A latter study by this group using the same patients with MS with helminthic infection compared with noninfected patients showed that surface expression of TLR2 on both B cells and dendritic cells (DCs) was significantly higher in infected patients with MS. Stimulation of myelin-specific T-cell lines with a TLR2 agonist induced inhibition of T-cell proliferation; suppressed IFN-g, IL-12, and IL-17 secretion; as well as increased IL-10 production, suggesting the functional responses observed correlate with TLR2 expression patterns.56 Helminths’ ova were introduced to mice with EAE and were found to reduce disease severity. Mice treated with S. mansoni ova 2 weeks before EAE induction underwent disease assessment, and the severity of EAE was reduced when measured by decreased clinical scores and CNS cellular infiltrates.57 TSO is a preliminary therapy in MS (phase 1 helminth-induced immunomodulatory therapy), a Th1/Th17-associated autoimmune disease. Slight downregulation of the Th1-associated cytokine pattern occurred and was especially relevant in IL-2 (P < 0.05 after 2 months of therapy), with a temporary increase of Th2-associated cytokines such as IL-4.58,59 In addition,
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the mean number of new gadolinium-enhanced MRI lesions decreased from 6.6 at baseline to 2.0 at the end of TSO administration, and 2 months after TSO was discontinued the mean number of new gadolinium-enhanced MRI lesions increased to 5.8, and no significant adverse effects were observed. Furthermore, mild eosinophilia and changes in the amounts of CD4 + and CD8+ T cells and natural killer CD56 bright cells were observed. The findings observed in this group of patients suggest that TSO therapy has a moderate immunomodulatory impact in MS.58,59 Nevertheless, it is important to take into account the potential for unrelated gastrointestinal events. Excretory-secretory muscle larvae (ES L1) products of the parasite T. spiralis successfully ameliorate EAE in Dark Agouti rats. Prophylactic application of ES L1 caused significant (P < 0.05) amelioration of EAE by a shift to the Th2-type response in the periphery and the CNS, as well as activation of regulatory mechanisms. Unconventional CD4+CD25-Foxp3 + regulatory cells were identified in increased proportion (P < 0.001) both in the periphery and the CNS of rats treated with ES L1 before the induction of EAE, and a possible role for these cells in amelioration of the disease was suggested.60 Treatment with soluble egg product homogenate from the nematodes T. suis, S. mansoni and T. spiralis was demonstrated to suppress TNF-a and IL-12 secretion by TLR-activated human DCs and induced significant suppression of symptoms in a murine EAE model.61 Parasite antigens such as omega-1, a glycoprotein derived from S. mansoni eggs, helminth cystatins from Acanthocheilonema viteae, Brugia malayi, Nippostrongylus braisliensis and Onchocerca volvolus were able to induce TLR2 expression on both B cells and DCs.56 It is important to remember the requirement for early treatment to gain therapeutic effect. This is mostly because the symptomatic phase of EAE is characterized by extensive tissue damage, much of which may be irreversible. Also, the treatment must be continuous.62
2.3 Helminths and Lupus Systemic lupus erythematosus (SLE) is a multiorgan chronic autoimmune disease. Most patients have skin lesions (the most common is a butterfly rash) and over 90 % of patients suffer from joint involvement such as inflammatory arthritis. SLE may, however, affect the kidneys, lungs, nervous system and other organs as well. It is a multifactorial disease that depends on genetic and environmental factors (including exposure to ultraviolet light and infections).63,64
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Similarity between parasitic infections and autoimmune disorders was found.65 Autoantibodies such as antinuclear antibodies, double-stranded DNA, and anti-Smith antibodies, which are present in SLE, have been identified in the serum of patients infected with Schistosoma.66 Furthermore, antiribosomal P protein antibodies present in chronic Chagas heart disease, caused by Trypanosoma cruzi, were shown to cross-react with anti-Smith antibodies, which are present in early SLE.67 Genetic polymorphisms conferring susceptibility to SLE, more specifically the inhibitory receptor FcgRIIb, has been identified in African and Asian populations living in areas considered to be endemic to malaria (Plasmodium falciparum). This lupus-associated FcgRIIb polymorphism enhances phagocytosis of the parasite-infected erythrocytes. This suggests that a polymorphism predisposing to SLE may be gained through reduced susceptibility to malaria.68 Moreover, one study using a experimental lupus model of NZB/NZWXF1 mice showed that female mice infected with Toxoplasma gondii developed milder renal involvement and had a longer life span than noninfected mice. Lower amounts of IL-10 and IFN-g were found in spleen cells of the infected mice.69
2.4 Helminths and Type 1 Diabetes Type 1 diabetes (T1D) is considered a Th1-mediated autoimmune disease and is influenced by both genetic and environmental factors. These factors lead to the development of autoantibodies directed at various islet cell components including glutamic acid decarboxylase antibodies (GAD65), islet cell antibodies (ICA512/IA-2) and insulin antibodies, which eventually leads to the destruction of pancreatic insulin-secreting b-cells. The subsequent lack of insulin leads to increased blood and urine glucose. Classical symptoms are polyuria, polydipsia, polyphagia and weight loss.70 The incidence of T1D has dramatically increased in the developed world over the past several decades. A linkage between the high prevalence of T1D and improved sanitation was proposed and was discussed previously in the hygiene theory.1 During the past two decades the potential use of helminths and helminth-derived products in the prevention of T1D has gained attention. Following the discovery of the role of Tregs in maintaining self-tolerance,71,72 the correlation between Th1 cells (IL-2 and IFN-g) and the pathogenesis of T1D was established. The role of Th2 cells (IL-4 and IL-10) and Tregs (IL-10 and TGF-b) in protection against T1D was demonstrated as well.73
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The elevated number of Tregs in helminthic infection attenuates inflammatory response and subsequent tissue damage. Based on the hypothesis that the pathomechanism of T1D is related to the impaired immunoregulatory activity of diabetogenic T cells, leading to the development of autoimmunity, early work in the field showed helminthic infections can prevent T1D. This is based on the assumption that the Th2 immune bias would ultimately attenuate the Th1-mediated response that triggers diseases such as T1D.74 Infection by the gastrointestinal helminths T. spiralis and Heligmosomoides polygyrus among 4- to 6-week-old nonobese diabetic (NOD) mice, which is a model of T1D, elicited a Th2 response, demonstrated by increased IL-4 and immunoglobulin (Ig) E levels. This is in contrast to the Th1 response that accompanies the development of diabetes in NOD mice and suggests that the Th2 response induced by T. spiralis and H. polygyrus infection might protect the mice from the effects of Th1-mediated b-cell destruction. NOD mice infected with H. polygyrus remained free of diabetes over the entire experimental time course (36 to 37 weeks).75 Litomosoides sigmodontis filarial worms prevent the onset of diabetes in infected NOD mice. Six-week-old female NOD mice were infected with either 40 L3-stage larvae, adult female worms or adult male worms, and glucose concentrations were monitored over time. The onset of diabetes (glucose concentration >230 mg/dL) was prevented in all mice tested until the end of the experiment, when they were 25 weeks old. Protection against diabetes was associated with a Th2 shift, as IL-4 and IL-5 released from a-CD3/a-CD28-stimulated splenocytes was greater in mice infected with L. sigmodontis than in uninfected mice.76 A subsequent study tested whether infection with L. sigmodontis prevents diabetes onset in IL-4-deficient NOD mice and whether depletion or absence of Tregs, IL-10, or TGF-b alters helminth-mediated protection.77 The study demonstrated that L. sigmodontis–mediated protection against diabetes in NOD mice is not dependent on the induction of a type 2 immune shift but does require TGF-b. Helminthic infection prevented the development of diabetes in NOD mice, even in the absence of IL-4 (P < 0.01). S. mansoni eggs have been shown to prevent T1D when administered to 4- to 6-week-old NOD mice. None of the injected mice developed diabetes, whereas the control mice developed diabetes with a 70% incidence by 27 weeks of age (p < 0.005).78 Insulin autoantibodies spontaneously develop in NOD mice and prediabetic humans. Infected mice had insulin autoantibodies that were predominantly of the IgM isotype. Infection with S. mansoni prevented the class switch of anti-insulin antibody, which
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is normally seen in most NOD mice as they approach overt diabetes.79 The live eggs of S. mansoni actively secrete the glycoprotein omega-1, which has been shown to be capable of conditioning human monocyte-derived DCs in vitro to induce a Th2 response,80 thus regulating (shifting) the host immune response and aiding in the parasite’s survival as well as migration.79 The glycoprotein omega-1 alone has been shown to directly elicit human DCs to induce Th2 development from naı¨ve CD4+ T cells and, furthermore, inhibit the release of IL-12, therefore reducing the differentiation of Th1 cells.80 Omega-1 also has been shown to induce IL-4 production as well as to prime Foxp3+ Tregs in NOD mice CD4 + cells.81 Antigen-nonspecific IgE was purified from the roundworm Dirofilaria immitis, which induces IgE in mice and rats. Recombinant D. immitis antigen treatment of 6-week-old NOD female mice completely prevented insulitis and diabetes. It was also associated with a switching of the response from a Th1 to a Th2 profile,82 as was shown in the previously presented studies.
2.5 Helminths and Rheumatoid Arthritis Rheumatoid arthritis (RA) is a chronic inflammatory arthritis with an autoimmune mechanism. It is the most common inflammatory arthritis, affecting about 1 % of the population.83 Like other autoimmune diseases, it comprises genetic as well as environmental factors, of which smoking is the most prominent.84 The disease is typically polyarticular and manifests as stiffness, pain and swelling. Extra-articular involvement includes anemia, subcutaneous nodules (rheumatoid nodules), neuropathy, Sjo¨gren’s syndrome, vasculitis, renal disease and other extra-articular features. An immunological hallmark of the disease is the development of anticitrullinated protein antibodies.85 Moreover, there is a predominance of Th1 cells, mostly CD4 +, and a deficiency of Th2 and Tregs. The T cells, and consequently the anticitrullinated protein antibodies, target the deaminated areas within rheumatoid joints.86,87 The first study associating helminthic infection and joint disease, dating back to 1975, was a surprising observation that rats infected with the nematode Syphacia obvelata developed milder complete Freund’s adjuvant– induced arthritis.88 Since then, studies have used various helminth models for investigating joint inflammation. The most commonly used model of arthritis is the type II collagen (Col II) model, which provokes multijoint inflammation. One such study demonstrated that infection with S. mansoni reduces the severity of Col
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II–induced arthritis in male DBA/1 mice. S. mansoni infection suppresses systemic and local proinflammatory mediators, thus leading to significantly less synovial hyperplasia, inflammatory cell recruitment and bone/cartilage destruction. Levels of IgG2a, which is involved in the pathology of Col II–induced arthritis, were decreased and polyclonal-stimulated splenic T cells expressed lower amounts of IFN-g, IL-17A and TNF-a. Higher amounts of IL-4 and IL-10 also were measured in comparison with naı¨ve mice immunized with Col II.89 C57BL/6 mice prophylactically infected with the rat intestinal tapeworm Hymenolepis diminuta (10 cysticercoids in 100 mm of phosphatebuffered saline) showed significantly (P < 0.05) attenuated complete Freund’s adjuvant–induced arthritis. Treatment with helminthic infection was as effective as treatment with dexamethasone or indomethacin (P < 0.05), the mainstay of treatment for arthritis. The infected mice showed reduced knee swelling, and, in addition, activated splenic T cells showed the expression of higher levels of IL-4 and IL-10.90 RA is associated with a Th1 response and a general increase in proinflammatory cytokines such as IL-6, IFN-g and TNF-a. Moreover, H. polygyrus excretory-secretory antigen induces the de novo expression of Foxp3 Tregs91,92 and induces the activity of alternatively activated macrophages.93 Early studies showed that the rodent filarial nematode A. viteae secretes ES-62, an immunomodulatory glycoprotein surrounded by a phosphorylcholine moiety attached to the protein by glycans.94 ES-62 induced a shift from a Th1 to a Th2 response and attenuated an RA-like disease in collageninduced arthritis (CIA). It elevated the production of the anti-inflammatory cytokine IL-10 and reduced levels of IFN-g and IL-12, which are proinflammatory cytokines.95–97 Cultures of human patients with RA synovial fluid showed reduced levels (P < 0.05) of TNF-a and IFN-g secretion in the presence of ES-62, whereas peripheral blood smears from the patients exhibited mononuclear cells with low IFN-g secretion after treatment with ES-62.98,99 Use of recombinant ES-62, the whole ES-62 molecule and a synthetic phosphorylcholine–ovalbumin conjugate showed that the clinical score of CIA was affected only PC-OVA or ES-62 but not recombinant ES-62. This fact led to the idea that the common denominator inducing tolerance is phosphorylcholine.100 Furthermore, Al-Riyami et al.101 designed a small-molecule analogue—a sulfone-containing phosphorylcholine analogue (11a)—and provided proof of concept in a murine CIA model. 11a Was as effective as ES-62 in protecting DBA/1 mice from developing CIA and mirrored its mechanism of action as an anti-inflammatory antigen.
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2.6 Helminths and Graves’ Disease Graves’ disease is considered an autoimmune syndrome in which hyperthyroidism is present in almost all patients. This thyroid disease is characterized by the presence of thyroid-stimulating hormone receptor (TSHR) antibodies,102 leading to follicular dysplasia, lymphocytic infiltration and, in most cases, diffuse enlargement of the gland. TSHR antibodies are detectable in almost all patients with Graves’ disease.103 A murine model of Graves’ disease has been described by the immunization of mice with thyrotropin receptor complementary DNA.104 From reviewing the literature, we found only one study that examined the association between helminthic infection and Graves’ disease. Graves’ disease was once thought to be a Th2-type immune response, but recent studies have described an Th1-type as well as a Th2-type response.105,106 Based on the ability of helminthic infection to polarize the immune response towards a Th2 type, a soluble homogenate of S. mansoni worm product and a-galactosylceramide (a-GalCer) has been used prophylactically in a murine model. a-GalCer is one of many glycoconjugates expressed by S. mansoni worms and live eggs.107 a-GalCer stimulates natural killer T cells to rapidly produce both Th1 and Th2 cytokines, but at a later time point and with repeated doses, a-GalCer promotes the development of a Th2 immune response, thus protecting against various autoimmune diseases. The results showed that both S. mansoni products and a-GalCer protected from Grave’s disease, mainly by suppressing a Th1-type anti-TSHR immune response at the time of antigen priming. This occurred by increasing the levels of the anti-inflammatory cytokine IL-10.108
3 CONCLUSION In Western countries a strong correlation exists between improved sanitation and hygiene and the significant increase in the prevalence of autoimmune and autoinflammatory diseases. Moreover, a reverse correlation was reported between the high prevalence of helminths and autoimmune diseases in certain geographic areas. Different helminths were proven to secrete different molecules that enhance tolerance in the human immune system to survive. Therefore, many researchers harness helminth secretory molecules to develop novel therapeutic compounds to treat autoimmune diseases.
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REFERENCES 1. Moroni L, Bianchi I, Lleo A. Geoepidemiology, gender and autoimmune disease. Autoimmun Rev 2012;11:A386–92. 2. Okada H, Kuhn C, Feillet H, Bach JF. The ‘hygiene hypothesis’ for autoimmune and allergic diseases: an update. Clin Exp Immunol 2010;160:1–9. 3. van Panhuis WG, Grefenstette J, Jung SY, Chok NS, Cross A, Eng H, et al. Contagious diseases in the united states from 1888 to the present. N Engl J Med 2013;369:2152–8. 4. von Mutius E. Allergies, infections and the hygiene hypothesis—the epidemiological evidence. Immunobiology 2007;212:433–9. 5. Strachan DP. Hay fever, hygiene, and household size. BMJ 1989;299:1259–60. 6. Carpenter L, Beral V, Strachan D, Ebi-Kryston KL, Inskip H. Respiratory symptoms as predictors of 27 year mortality in a representative sample of British adults. BMJ 1989;299:357–61. 7. Lynch NR, Hagel I, Perez M, Di Prisco MC, Lopez R, Alvarez N. Effect of anthelmintic treatment on the allergic reactivity of children in a tropical slum. J Allergy Clin Immunol 1993;92:404–11. 8. van den Biggelaar AH, Rodrigues LC, van Ree R, van der Zee JS, HoeksmaKruize YC, Souverijn JH, et al. Long-term treatment of intestinal helminths increases mite skin-test reactivity in Gabonese schoolchildren. J Infect Dis 2004;189:892–900. 9. Flohr C, Tuyen LN, Lewis S, Quinnell R, Minh TT, Liem HT, et al. Poor sanitation and helminth infection protect against skin sensitization in Vietnamese children: a crosssectional study. J Allergy Clin Immunol 2006;118:1305–11. 10. Bitti PP, Murgia BS, Ticca A, Ferrai R, Musu L, Piras ML, et al. Association between the ancestral haplotype hla a30b18dr3 and multiple sclerosis in central Sardinia. Genet Epidemiol 2001;20:271–83. 11. Sotgiu S, Angius A, Embry A, Rosati G, Musumeci S. Hygiene hypothesis: innate immunity, malaria and multiple sclerosis. Med Hypotheses 2008;70:819–25. 12. Francis L, Perl A. Infection in systemic lupus erythematosus: friend or foe? Int J Clin Rheumtol 2010;5:59–74. 13. Butcher GA, Clark IA. Sle and malaria: another look at an old idea. Parasitol Today 1990;6:259–61. 14. Kondrashova A, Seiskari T, Ilonen J, Knip M, Hyoty H. The ‘hygiene hypothesis’ and the sharp gradient in the incidence of autoimmune and allergic diseases between Russian karelia and Finland. APMIS 2013;121:478–93. 15. Seiskari T, Kondrashova A, Viskari H, Kaila M, Haapala AM, Aittoniemi J, et al. Allergic sensitization and microbial load—a comparison between Finland and Russian karelia. Clin Exp Immunol 2007;148:47–52. 16. McSorley HJ, Maizels RM. Helminth infections and host immune regulation. Clin Microbiol Rev 2012;25:585–608. 17. Ben-Ami Shor D, Harel M, Eliakim R, Shoenfeld Y. The hygiene theory harnessing helminths and their ova to treat autoimmunity. Clin Rev Allergy Immunol 2013;45:211–16. 18. Assadsangabi A, Lobo AJ. Diagnosing and managing inflammatory bowel disease. Practitioner 2013;257:13–82. 19. Mayer L. Evolving paradigms in the pathogenesis of ibd. J Gastroenterol 2010;45:9–16. 20. Elliott DE, Urban JJ, Argo CK, Weinstock JV. Does the failure to acquire helminthic parasites predispose to Crohn’s disease? FASEB J 2000;14:1848–55. 21. Fiasse R, Latinne D. Intestinal helminths: a clue explaining the low incidence of inflammatory bowel diseases in subsaharan Africa? Potential benefits and hazards of helminth therapy. Acta Gastroenterol Belg 2006;69:418–22.
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22. Walk ST, Blum AM, Ewing SA, Weinstock JV, Young VB. Alteration of the murine gut microbiota during infection with the parasitic helminth heligmosomoides polygyrus. Inflamm Bowel Dis 2010;16:1841–9. 23. Weinstock JV. Autoimmunity: the worm returns. Nature 2012;491:183–5. 24. Hang L, Setiawan T, Blum AM, Urban J, Stoyanoff K, Arihiro S, et al. Heligmosomoides polygyrus infection can inhibit colitis through direct interaction with innate immunity. J Immunol 2010;185:3184–9. 25. Elliott DE, Setiawan T, Metwali A, Blum A, Urban Jr. JF, Weinstock JV. Heligmosomoides polygyrus inhibits established colitis in il-10-deficient mice. Eur J Immunol 2004;34:2690–8. 26. Wang LJ, Cao Y, Shi HN. Helminth infections and intestinal inflammation. World J Gastroenterol 2008;14:5125–32. 27. Cassinotti A, Sarzi-Puttini P, Fichera M, Shoenfeld Y, de Franchis R, Ardizzone S. Immunity, autoimmunity and inflammatory bowel disease. Autoimmun Rev 2014;13:1–2. 28. Weinstock JV, Summers RW, Elliott DE. Role of helminths in regulating mucosal inflammation. Springer Semin Immunopathol 2005;27:249–71. 29. Scholmerich J. Trichuris suis ova in inflammatory bowel disease. Dig Dis 2013;31:391–5. 30. Elliott DE, Metwali A, Leung J, Setiawan T, Blum AM, Ince MN, et al. Colonization with heligmosomoides polygyrus suppresses mucosal il-17 production. J Immunol 2008;181:2414–9. 31. Fitzpatrick LR. Inhibition of il-17 as a pharmacological approach for ibd. Int Rev Immunol 2013;32:544–55. 32. Mohammadi M, Zahedi MJ, Nikpoor AR, Baneshi MR, Hayatbakhsh MM. Interleukin-17 serum levels and tlr4 polymorphisms in ulcerative colitis. Iran J Immunol 2013;10:83–92. 33. Elliott DE, Li J, Blum A, Metwali A, Qadir K, Urban Jr. JF, et al. Exposure to schistosome eggs protects mice from TNBS-induced colitis. Am J Physiol Gastrointest Liver Physiol 2003;284:G385–91. 34. Moreels TG, Nieuwendijk RJ, De Man JG, De Winter BY, Herman AG, Van Marck EA, et al. Concurrent infection with schistosoma mansoni attenuates inflammation induced changes in colonic morphology, cytokine levels, and smooth muscle contractility of trinitrobenzene sulphonic acid induced colitis in rats. Gut 2004;53:99–107. 35. Ruyssers NE, De Winter BY, De Man JG, Loukas A, Pearson MS, Weinstock JV, et al. Therapeutic potential of helminth soluble proteins in TNBS-induced colitis in mice. Inflamm Bowel Dis 2009;15:491–500. 36. Ruyssers NE, De Winter BY, De Man JG, Ruyssers ND, Van Gils AJ, Loukas A, et al. Schistosoma mansoni proteins attenuate gastrointestinal motility disturbances during experimental colitis in mice. World J Gastroenterol 2010;16:703–12. 37. Beer RJ. The relationship between trichuris trichiura (linnaeus 1758) of man and trichuris suis (schrank 1788) of the pig. Res Vet Sci 1976;20:47–54. 38. Sandborn WJ, Elliott DE, Weinstock J, Summers RW, Landry-Wheeler A, Silver N, et al. Randomised clinical trial: the safety and tolerability of trichuris suis ova in patients with Crohn’s disease. Aliment Pharmacol Ther 2013;38:255–63. 39. Summers RW, Elliott DE, Qadir K, Urban Jr. JF, Thompson R, Weinstock JV. Trichuris suis seems to be safe and possibly effective in the treatment of inflammatory bowel disease. Am J Gastroenterol 2003;98:2034–41. 40. Summers RW, Elliott DE, Urban Jr. JF, Thompson R, Weinstock JV. Trichuris suis therapy in Crohn’s disease. Gut 2005;54:87–90. 41. Summers RW, Elliott DE, Urban Jr. JF, Thompson RA, Weinstock JV. Trichuris suis therapy for active ulcerative colitis: a randomized controlled trial. Gastroenterology 2005;128:825–32.
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42. Summers RW, Elliott DE, Weinstock JV. Is there a role for helminths in the therapy of inflammatory bowel disease? Nat Clin Pract Gastroenterol Hepatol 2005;2:62–3. 43. Kradin RL, Badizadegan K, Auluck P, Korzenik J, Lauwers GY. Iatrogenic trichuris suis infection in a patient with Crohn disease. Arch Pathol Lab Med 2006;130: 718–20. 44. Motomura Y, Wang H, Deng Y, El-Sharkawy RT, Verdu EF, Khan WI. Helminth antigen-based strategy to ameliorate inflammation in an experimental model of colitis. Clin Exp Immunol 2009;155:88–95. 45. Sun S, Wang X, Wu X, Zhao Y, Wang F, Liu X, et al. Toll-like receptor activation by helminths or helminth products to alleviate inflammatory bowel disease. Parasit Vectors 2011;4:186. 46. Multiple sclerosis: national clinical guideline for diagnosis and management in primary and secondary care. NICE Clinical Guidelines, No. 8. London: National Collaborating Centre for Chronic Conditions (UK); 2004. 47. Stuve O, Oksenberg J. Multiple sclerosis overview. In: Pagon RA, Adam MP, Bird TD, Dolan CR, Fong CT, Stephens K, editors. Genereviews; 1993, GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993–2014. Available from: http:// www.ncbi.nlm.nih.gov/books/NBK1316/. 48. Correale J, Farez MF. The impact of environmental infections (parasites) on ms activity. Mult Scler 2011;17:1162–9. 49. Rosati G. The prevalence of multiple sclerosis in the world: an update. Neurol Sci 2001;22:117–39. 50. Rangachari M, Kuchroo VK. Using eae to better understand principles of immune function and autoimmune pathology. J Autoimmun 2013;45:31–9. 51. La Flamme AC, Ruddenklau K, Backstrom BT. Schistosomiasis decreases central nervous system inflammation and alters the progression of experimental autoimmune encephalomyelitis. Infect Immun 2003;71:4996–5004. 52. Reyes JL, Espinoza-Jimenez AF, Gonzalez MI, Verdin L, Terrazas LI. Taenia crassiceps infection abrogates experimental autoimmune encephalomyelitis. Cell Immunol 2011;267:77–87. 53. Correale J, Farez M. Association between parasite infection and immune responses in multiple sclerosis. Ann Neurol 2007;61:97–108. 54. Correale J, Farez MF. The impact of parasite infections on the course of multiple sclerosis. J Neuroimmunol 2011;233:6–11. 55. Correale J, Farez M, Razzitte G. Helminth infections associated with multiple sclerosis induce regulatory b cells. Ann Neurol 2008;64:187–99. 56. Correale J, Farez MF. Does helminth activation of toll-like receptors modulate immune response in multiple sclerosis patients? Front Cell Infect Microbiol 2012;2:112. 57. Sewell D, Qing Z, Reinke E, Elliot D, Weinstock J, Sandor M, et al. Immunomodulation of experimental autoimmune encephalomyelitis by helminth ova immunization. Int Immunol 2003;15:59–69. 58. Benzel F, Erdur H, Kohler S, Frentsch M, Thiel A, Harms L, et al. Immune monitoring of trichuris suis egg therapy in multiple sclerosis patients. J Helminthol 2012;86:339–47. 59. Fleming JO, Isaak A, Lee JE, Luzzio CC, Carrithers MD, Cook TD, et al. Probiotic helminth administration in relapsing-remitting multiple sclerosis: a phase 1 study. Mult Scler 2011;17:743–54. 60. Sofronic-Milosavljevic LJ, Radovic I, Ilic N, Majstorovic I, Cvetkovic J, GrudenMovsesijan A. Application of dendritic cells stimulated with trichinella spiralis excretory-secretory antigens alleviates experimental autoimmune encephalomyelitis. Med Microbiol Immunol 2013;202:239–49. 61. Kuijk LM, Klaver EJ, Kooij G, van der Pol SM, Heijnen P, Bruijns SC, et al. Soluble helminth products suppress clinical signs in murine experimental autoimmune
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62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80.
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encephalomyelitis and differentially modulate human dendritic cell activation. Mol Immunol 2012;51:210–18. Fleming JO. Helminth therapy and multiple sclerosis. Int J Parasitol 2013;43:259–74. Shoenfeld Y, Zandman-Goddard G, Stojanovich L, Cutolo M, Amital H, Levy Y, et al. The mosaic of autoimmunity: hormonal and environmental factors involved in autoimmune diseases—2008. Isr Med Assoc J 2008;10:8–12. Sherer Y, Gorstein A, Fritzler MJ, Shoenfeld Y. Autoantibody explosion in systemic lupus erythematosus: more than 100 different antibodies found in sle patients. Semin Arthritis Rheum 2004;34:501–37. Zandman-Goddard G, Shoenfeld Y. Parasitic infection and autoimmunity. Lupus 2009;18:1144–8. Rahima D, Tarrab-Hazdai R, Blank M, Arnon R, Shoenfeld Y. Anti-nuclear antibodies associated with schistosomiasis and anti-schistosomal antibodies associated with sle. Autoimmunity 1994;17:127–41. Levitus G, Hontebeyrie-Joskowicz M, Van Regenmortel MH, Levin MJ. Humoral autoimmune response to ribosomal p proteins in chronic chagas heart disease. Clin Exp Immunol 1991;85:413–7. Clatworthy MR, Willcocks L, Urban B, Langhorne J, Williams TN, Peshu N, et al. Systemic lupus erythematosus-associated defects in the inhibitory receptor fcgriib reduce susceptibility to malaria. Proc Natl Acad Sci USA 2007;104:7169–74. Chen M, Aosai F, Norose K, Mun HS, Ishikura H, Hirose S, et al. Toxoplasma gondii infection inhibits the development of lupus-like syndrome in autoimmune (New Zealand black x New Zealand white) f1 mice. Int Immunol 2004;16:937–46. Donath MY, Hess C, Palmer E. What is the role of autoimmunity in type 1 diabetes? A clinical perspective. Diabetologia 2014;57:653–5. Hori I, Kishida Y. Quantitative changes in nuclear pores and chromatoid bodies induced by neuropeptides during cell differentiation in the planarian dugesia japonica. J Submicrosc Cytol Pathol 2003;35:439–44. Wing K, Sakaguchi S. Regulatory t cells exert checks and balances on self tolerance and autoimmunity. Nat Immunol 2010;11:7–13. Kikodze N, Pantsulaia I, Rekhviashvili K, Iobadze M, Jakhutashvili N, Pantsulaia N, et al. Cytokines and t regulatory cells in the pathogenesis of type 1 diabetes. Georgian Med News 2013;222:29–35. Taylor MD, van der Werf N, Maizels RM. T cells in helminth infection: the regulators and the regulated. Trends Immunol 2012;33:181–9. Saunders KA, Raine T, Cooke A, Lawrence CE. Inhibition of autoimmune type 1 diabetes by gastrointestinal helminth infection. Infect Immun 2007;75:397–407. Hubner MP, Stocker JT, Mitre E. Inhibition of type 1 diabetes in filaria-infected nonobese diabetic mice is associated with a t helper type 2 shift and induction of foxp3+ regulatory t cells. Immunology 2009;127:512–22. Hubner MP, Shi Y, Torrero MN, Mueller E, Larson D, Soloviova K, et al. Helminth protection against autoimmune diabetes in nonobese diabetic mice is independent of a type 2 immune shift and requires tgf-beta. J Immunol 2012;188:559–68. Zaccone P, Fehervari Z, Jones FM, Sidobre S, Kronenberg M, Dunne DW, et al. Schistosoma mansoni antigens modulate the activity of the innate immune response and prevent onset of type 1 diabetes. Eur J Immunol 2003;33:1439–49. Cooke A, Tonks P, Jones FM, O’Shea H, Hutchings P, Fulford AJ, et al. Infection with schistosoma mansoni prevents insulin dependent diabetes mellitus in non-obese diabetic mice. Parasite Immunol 1999;21:169–76. Everts B, Perona-Wright G, Smits HH, Hokke CH, van der Ham AJ, Fitzsimmons CM, et al. Omega-1, a glycoprotein secreted by schistosoma mansoni eggs, drives th2 responses. J Exp Med 2009;206:1673–80.
The protective role of helminths in autoimmunity
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81. Zaccone P, Burton OT, Gibbs SE, Miller N, Jones FM, Schramm G, et al. The s. Mansoni glycoprotein omega-1 induces foxp3 expression in nod mouse cd4(+) t cells. Eur J Immunol 2011;41:2709–18. 82. Imai S, Tezuka H, Fujita K. A factor of inducing ige from a filarial parasite prevents insulin-dependent diabetes mellitus in nonobese diabetic mice. Biochem Biophys Res Commun 2001;286:1051–8. 83. Rothschild BM, Turner KR, DeLuca MA. Symmetrical erosive peripheral polyarthritis in the late archaic period of Alabama. Science 1988;241:1498–501. 84. Lundstrom E, Kallberg H, Alfredsson L, Klareskog L, Padyukov L. Gene-environment interaction between the drb1 shared epitope and smoking in the risk of anti-citrullinated protein antibody-positive rheumatoid arthritis: all alleles are important. Arthritis Rheum 2009;60:1597–603. 85. Wegner N, Lundberg K, Kinloch A, Fisher B, Malmstrom V, Feldmann M, et al. Autoimmunity to specific citrullinated proteins gives the first clues to the etiology of rheumatoid arthritis. Immunol Rev 2010;233:34–54. 86. De Rycke L, Nicholas AP, Cantaert T, Kruithof E, Echols JD, Vandekerckhove B, et al. Synovial intracellular citrullinated proteins colocalizing with peptidyl arginine deiminase as pathophysiologically relevant antigenic determinants of rheumatoid arthritis-specific humoral autoimmunity. Arthritis Rheum 2005;52:2323–30. 87. Takizawa Y, Suzuki A, Sawada T, Ohsaka M, Inoue T, Yamada R, et al. Citrullinated fibrinogen detected as a soluble citrullinated autoantigen in rheumatoid arthritis synovial fluids. Ann Rheum Dis 2006;65:1013–20. 88. Pearson DJ, Taylor G. The influence of the nematode syphacia oblevata on adjuvant arthritis in the rat. Immunology 1975;29:391–6. 89. Osada Y, Shimizu S, Kumagai T, Yamada S, Kanazawa T. Schistosoma mansoni infection reduces severity of collagen-induced arthritis via down-regulation of proinflammatory mediators. Int J Parasitol 2009;39:457–64. 90. Shi M, Wang A, Prescott D, Waterhouse CC, Zhang S, McDougall JJ, et al. Infection with an intestinal helminth parasite reduces Freund’s complete adjuvant-induced monoarthritis in mice. Arthritis Rheum 2011;63:434–44. 91. Grainger JR, Smith KA, Hewitson JP, McSorley HJ, Harcus Y, Filbey KJ, et al. Helminth secretions induce de novo t cell foxp3 expression and regulatory function through the tgf-beta pathway. J Exp Med 2010;207:2331–41. 92. Carranza F, Falcon CR, Nunez N, Knubel C, Correa SG, Bianco I, et al. Helminth antigens enable cpg-activated dendritic cells to inhibit the symptoms of collagen-induced arthritis through foxp3 + regulatory t cells. PLoS One 2012;7:e40356. 93. Espinoza-Jimenez A, Rivera-Montoya I, Cardenas-Arreola R, Moran L, Terrazas LI. Taenia crassiceps infection attenuates multiple low-dose streptozotocin-induced diabetes. J Biomed Biotechnol 2010;2010:850541. 94. Harnett W, Harnett MM, Leung BP, Gracie JA, McInnes IB. The anti-inflammatory potential of the filarial nematode secreted product, es-62. Curr Top Med Chem 2004;4:553–9. 95. Marshall FA, Grierson AM, Garside P, Harnett W, Harnett MM. Es-62, an immunomodulator secreted by filarial nematodes, suppresses clonal expansion and modifies effector function of heterologous antigen-specific t cells in vivo. J Immunol 2005;175:5817–26. 96. Stepek G, Auchie M, Tate R, Watson K, Russell DG, Devaney E, et al. Expression of the filarial nematode phosphorylcholine-containing glycoprotein, es62, is stage specific. Parasitology 2002;125:155–64. 97. Harnett W, Harnett MM. Filarial nematode secreted product es-62 is an anti-inflammatory agent: therapeutic potential of small molecule derivatives and es-62 peptide mimetics. Clin Exp Pharmacol Physiol 2006;33:511–18.
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Infection and autoimmunity
98. McInnes IB, Leung BP, Harnett M, Gracie JA, Liew FY, Harnett W. A novel therapeutic approach targeting articular inflammation using the filarial nematode-derived phosphorylcholine-containing glycoprotein es-62. J Immunol 2003;171:2127–33. 99. McInnes IB, Schett G. Cytokines in the pathogenesis of rheumatoid arthritis. Nat Rev Immunol 2007;7:429–42. 100. Harnett MM, Kean DE, Boitelle A, McGuiness S, Thalhamer T, Steiger CN, et al. The phosphorycholine moiety of the filarial nematode immunomodulator es-62 is responsible for its anti-inflammatory action in arthritis. Ann Rheum Dis 2008;67:518–23. 101. Al-Riyami L, Pineda MA, Rzepecka J, Huggan JK, Khalaf AI, Suckling CJ, et al. Designing anti-inflammatory drugs from parasitic worms: a synthetic small molecule analogue of the acanthocheilonema viteae product es-62 prevents development of collagen-induced arthritis. J Med Chem 2013;56:9982–10002. 102. Latif R, Morshed SA, Zaidi M, Davies TF. The thyroid-stimulating hormone receptor: impact of thyroid-stimulating hormone and thyroid-stimulating hormone receptor antibodies on multimerization, cleavage, and signaling. Endocrinol Metab Clin North Am 2009;38:319–41, viii. 103. Lytton SD, Kahaly GJ. Bioassays for tsh-receptor autoantibodies: an update. Autoimmun Rev 2010;10:116–22. 104. Costagliola S, Many MC, Denef JF, Pohlenz J, Refetoff S, Vassart G. Genetic immunization of outbred mice with thyrotropin receptor cdna provides a model of Graves’ disease. J Clin Invest 2000;105:803–11. 105. Dogan RN, Vasu C, Holterman MJ, Prabhakar BS. Absence of il-4, and not suppression of the th2 response, prevents development of experimental autoimmune Graves’ disease. J Immunol 2003;170:2195–204. 106. Nagayama Y, Mizuguchi H, Hayakawa T, Niwa M, McLachlan SM, Rapoport B. Prevention of autoantibody-mediated graves’-like hyperthyroidism in mice with il-4, a th2 cytokine. J Immunol 2003;170:3522–7. 107. Makaaru CK, Damian RT, Smith DF, Cummings RD. The human blood fluke schistosoma mansoni synthesizes a novel type of glycosphingolipid. J Biol Chem 1992;267:2251–7. 108. Nagayama Y, Watanabe K, Niwa M, McLachlan SM, Rapoport B. Schistosoma mansoni and alpha-galactosylceramide: prophylactic effect of th1 immune suppression in a mouse model of Graves’ hyperthyroidism. J Immunol 2004;173:2167–73.
The Protective Role of Helminths in Autoimmunity Tomer Bashi, Tom Konikoff, Miri Blank, Yehuda Shoenfeld,1 *
Zabludowicz Center For Autoimmune Diseases; Sheba Medical Center; Tel-Aviv University; Ramat Gan, Israel Corresponding Author: [email protected]
1
1 INTRODUCTION For the past several decades, Western industrialized countries are facing a high rate of autoinflammatory disorders, which are being expressed by higher prevalence of autoimmune diseases and allergies.1,2 The lifestyle in industrialized countries had led to a decrease of infectious burden; however, a reverse correlation has been seen with the prevalence of autoimmune diseases.3 Limited exposure to microorganisms such as helminths and microbes during childhood eventually leads to an off-balanced immune system. This theory, known as the Hygiene Theory or the Hygiene Hypothesis, was first proposed by Strachan, who observed an inverse correlation between hay fever and the number of older siblings while following more than 17,000 British children born in 1958.4–6 In addition to the eradication of worms in the Western world, eradication of helminths increased atopic skin sensitization in Venezuela,7 in Gabon,8 and in Vietnam.9 For example, the prevalence of malaria is in reverse correlation to autoimmune diseases; several sources of epidemiological and immunogenetic evidence link the disappearance of malaria because of societies’ eradication programs with the increase of multiple sclerosis (MS) in Sardinia, due to the high genetic susceptibility of human leukocyte antigen DR3 within the island.10–13 Moreover, the contribution of helminths to the development of autoimmune diseases also was demonstrated in the Karelian region. Finland’s Karelian maintains have one of the highest prevalences of autoimmune and allergic diseases, whereas the prevalence in the Russian Karelian region is far lower. The fact that the Russian section is rife with infections and the Finnish part is dramatically cleaner has a large impact on the difference in prevalence.14,15 Infection and Autoimmunity http://dx.doi.org/10.1016/B978-0-444-63269-2.00012-X
© 2015 Elsevier B.V. All rights reserved.
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Helminths aim is to survive in the host; therefore they try to induce a tolerance scenario. Yet it is important to keep in mind that immunomodulation is affected by several key elements such as the burden of the infection and the host’s immune system. In most cases helminths induce tolerance, but in some scenarios they may cause an inflammatory response. The spectrum of affliction in chronic helminthic tissue infection contains low pathology with high parasite burden and chronic disease with low parasite burden. For example, in areas where schistosomiasis and filarial diseases are endemic, some individuals develop chronic debilitating pathologies and others show a tolerant phenotype. The tolerant phenotype is characterized by the production of anti-inflammatory cytokines such as transforming growth factor (TGF)-b and interleukin (IL)-10 and increased number of FoxP3+ T regulatory cells (Tregs). These cytokines lead to suppressed parasitespecific T-cell proliferation in peripheral blood mononuclear cells, reduced levels of T helper (Th) 2 cytokines, and ablated Th1 cytokines. Thus, the parasite survives productively in the host with minimal collateral damage.16,17
2 THE PROTECTIVE ROLE OF HELMINTHS IN AUTOIMMUNE DISEASES 2.1 Helminths and Inflammatory Bowel Disease Ulcerative colitis (UC) and Crohn’s disease (CD) are two medical conditions collectively called inflammatory bowel disease (IBD). They involve an excess Th1 immune response towards the intestinal cells.18,19 UC and CD are classified as separate diseases because each exhibits several distinguishing clinical and pathological features. UC has higher incidence of rectal involvement and the lesions are continuous, whereas CD contains skipped regions of lesions, terminal ileal ulceration, fistulization and/or anal fissuring and longitudinal ulcerations. In the late 1990s, Elliott et al.20 raised the IBD ‘hygiene hypothesis’ based on the increasing prevalence of IBDs in the United States and the fact it is in contrast to the prevalence of helminths in the USA. They proposed that exposure to helminths might protect against IBDs. In sub-Saharan Africa, low incidence and prevalence of IBD was observed and cannot be explained by genetic factors because in black populations in the USA and the UK, the incidence of IBDs is approaching that of white populations.21 Researchers attribute this fact to the ability of helminths to influence the composition of the microbiome, downmodulate
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the secretion of proinflammatory cytokines, upregulate Tregs and switch the immune response from Th1 to Th2, thus reducing inflammation in IBDs.22–29 Helminths, their ova and their antigens have been used in many studies that tried to treat IBDs in murine models and in human cases. Colonization of Heligmosomoides polygyrus in IL-10 knockout mice with piroxicam-induced colitis suppressed the production of IL-17 by lamina propria mononuclear cells and improved colitis.30–32 Schistosome ova exposure attenuated 2,4,6-trinitrobenzene sulfonic acid colitis and protected mice from lethal inflammation. Interferon (IFN)-g levels were reduced, whereas IL-4 and IL-10 messenger RNA levels were enhanced because of production by aCD3-stimulated spleen and mesenteric lymph node.33–36 Murine studies have led to human therapy trials with helminth ova: (1) A study conducted in the early 2000s suggested that Trichuris suis (pig whipworm) seemed to be safe and possibly effective in the treatment of IBD. T. suis met safety requirements. The pig is a natural host for T. suis; it can colonize people but only for a short length of time.37 A single dose of T. suis ova (TSO; up to 7500 ova) was well tolerated and did not result in short- or long-term treatment-related side effects.38 (2) Summers et al.39 studied four patients with active CD and three with UC. In an initial treatment and observation period, a single dose of 2500 live TSO was given orally, and patients were followed every 2 weeks for 12 weeks. To assess safety and efficacy with subsequent doses, two patients with CD and two with UC were given 2500 ova at 3-week intervals as maintenance. Patients with UC experienced a reduction of the Clinical Colitis Activity Index to 57% of baseline. According to the IBD Quality of Life Index, 6 of 7 patients (86%) achieved remission. The benefit was temporary in some patients with a single dose, but it could be prolonged with maintenance therapy every 3 weeks. (3) Another study using TSO also conducted by Summers et al.,40 involved 29 patients with active CD. All patients ingested 2500 live TSO every 3 weeks for 24 weeks, and disease activity was monitored using the Crohn’s Disease Activity Index (CDAI). The results were impressive: At week 24, 23 patients (79.3%) responded (decrease in CDAI by >100 points or a CDAI <150) and 21 of 29 patients (72.4%) remitted (CDAI <150). (4) In a randomized, double blind, placebo-controlled trial including 54 patients with active colitis, defined by Disease Activity Index (DAI)
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of 4, patients received 2500 TSO or placebo orally at 2-week intervals for 12 weeks. The primary efficacy variable was improvement of the DAI to 4. After 12 weeks of therapy, improvement according to the intent-to-treat principle occurred in 13 of 30 patients (43.3%) receiving ova treatment compared with 4 of 24 patients (16.7%) given placebo (P ¼ .04). Improvement also occurred with the Simple Index, which was significant by week 6.41,42 It is important to mention one case report regarding iatrogenic infection by T. suis in a 16-year-old adolescent with CD who was treated with TSO. He received 5 oral doses of 2500 TSO off protocol. When admitted to the hospital, pathologic evaluation showed several round helminthic forms directly beneath attenuated ileocecal mucosal epithelium—the helminths from the TSO had evolved in his intestine.43 As for antigens, treatment with Trichinella spiralis frozen skeletal muscle larvae before inducing colitis with dinitrobenzene sulfonic acid significantly reduced the severity of colitis; downregulated myeloperoxidase activity, IL-1b production, and inducible nitric oxide synthase expression; and an upregulated IL-13 and TGF-b production in the colon in a mouse model.44 Furthermore, the use of antagonists of Toll-like receptor (TLR) signaling and agonists of their negative regulators from helminths or helminth products should be considered for the treatment of IBD because TLR signaling may contribute to destructive host responses and chronic inflammation, whereas helminths may play an important role in the downregulation of gene activation in controlling overwhelming inflammation and proinflammatory cytokine production.45
2.2 Helminths and Multiple Sclerosis MS is an inflammatory, demyelinating, neurodegenerative disorder of the central nervous system (CNS) of unknown etiology. The most common clinical signs and symptoms, occurring in isolation or in combination, include sensory disturbance of the limbs (30%), partial or complete visual loss (15%), acute and subacute motor dysfunction of the limbs (13%), diplopia (7%) and gait dysfunction (5%). The impact of MS on an individual is variable, but one constant feature is the uncertainty of this disease.46,47 The incidence of MS has significantly increased during the second half of the 20th century. Caucasian individuals from Northern Europe are more
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prone to have the disease, while it is rare among Asians and Africans, with a low prevalence in tropical regions, indicating the importance of environmental factors such as helminths. The incidence increases as distance north of the equator lengthens.48,49 It was mentioned earlier that the eradication of malaria in Sardinia was preceded by the increase in the prevalence of MS on the island because of the high genetic susceptibility of human leukocyte antigen DR3 there.10,11 The most frequently studied animal model of MS is experimental autoimmune encephalitis (EAE), which mimics several of the key clinical and pathological features of the human disease, such as paralysis and demyelination.50 Percutaneously infection of Schistosoma mansoni cercariae in mice significantly reduced the incidence and delayed the onset of EAE in a mouse model. Production of IFN-g, nitric oxide, and tumor necrosis factor (TNF)-a by splenocytes was significantly reduced.51 Taenia crassiceps cysticerci (a 40 metacestodes infection load) also was able to reduce the severity of EAE. Only 50% of T. crassiceps-infected mice displayed EAE symptoms, which were significantly (P < 0.05) less severe than in uninfected mice. This effect was associated with both decreased myelin oligodendrocyte glycoprotein–specific splenocyte proliferation and IL-17 production and limited leukocyte infiltration into the spinal cord. Infection with T. crassiceps induced an anti-inflammatory cytokine microenvironment, including decreased TNF-a production and high myelin oligodendrocyte glycoprotein–specific production of IL-4 and IL-10.52 To prove the beneficial effect of helminths on patients with MS, Correale and Farez performed several studies. In a prospective doublecohort study, 12 patients (8 female and 4 male patients) with a clinical diagnosis of MS were assessed. The 12 patients with MS were infected with several helminth species (Hymenolepis nanan, Trichiuris trichura, Ascaris lumbricoides, Strongyloides stercoralis and Enterobius vermicularis); each patient was infected with one species. A control group containing healthy subjects was also infected with helminths, and another 12 uninfected patients with MS in remission matched for age, sex, and disease duration served as control subjects. It was shown that parasite-infected patients with MS had significantly fewer exacerbations, minimal variation in disability scores, as well as fewer magnetic resonance imaging (MRI) changes when compared with uninfected patients with MS.53,54 Moreover, responses to myelin basic protein peptide–specific T-cell clones were tested for cytokine secretion in peripheral blood and showed a significant increase (P < 0.0001) in the anti-inflammatory cytokines
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IL-10 and TGF-b and a decrease in cells secreting proinflammatory cytokines IL-12 and IFN-g in infected patients with MS compared with noninfected patients. Myelin basic protein–specific T-cells cloned from infected subjects were characterized by the absence of IL-2 and IL-4 production but high IL-10 and/or TGF-b secretion. In addition, the cloning frequency of CD4 + CD25+ FoxP3+ Tregs from those patients was increased (P < 0.0001) in infected patients compared with uninfected subjects with MS.53,54 Investigation of B-cell-mediated control mechanisms occurring during parasite infections in patients with MS demonstrated that helminthic infections (H. nanan, T. trichura, A. lumbricoides, S. stercoralis and E. vermicularis) cause a B-cell population producing high levels of IL-10, thus inhibiting harmful autoinflammatory immune responses. Moreover, B cells isolated from patients with MS infected with helminths also produced greater amounts of brain-derived neurotrophic factor and nerve growth factor, which is a type of protein that is important for the growth, maintenance, and survival of nerve cells, compared with healthy subjects and uninfected individuals with MS, raising the possibility that these cells may exert certain neuroprotective functions on the CNS. Hence, in addition to their immune-modulatory effect, helminths possess other beneficial aspects, such as promoting the growth of nerve cells.55 A latter study by this group using the same patients with MS with helminthic infection compared with noninfected patients showed that surface expression of TLR2 on both B cells and dendritic cells (DCs) was significantly higher in infected patients with MS. Stimulation of myelin-specific T-cell lines with a TLR2 agonist induced inhibition of T-cell proliferation; suppressed IFN-g, IL-12, and IL-17 secretion; as well as increased IL-10 production, suggesting the functional responses observed correlate with TLR2 expression patterns.56 Helminths’ ova were introduced to mice with EAE and were found to reduce disease severity. Mice treated with S. mansoni ova 2 weeks before EAE induction underwent disease assessment, and the severity of EAE was reduced when measured by decreased clinical scores and CNS cellular infiltrates.57 TSO is a preliminary therapy in MS (phase 1 helminth-induced immunomodulatory therapy), a Th1/Th17-associated autoimmune disease. Slight downregulation of the Th1-associated cytokine pattern occurred and was especially relevant in IL-2 (P < 0.05 after 2 months of therapy), with a temporary increase of Th2-associated cytokines such as IL-4.58,59 In addition,
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the mean number of new gadolinium-enhanced MRI lesions decreased from 6.6 at baseline to 2.0 at the end of TSO administration, and 2 months after TSO was discontinued the mean number of new gadolinium-enhanced MRI lesions increased to 5.8, and no significant adverse effects were observed. Furthermore, mild eosinophilia and changes in the amounts of CD4 + and CD8+ T cells and natural killer CD56 bright cells were observed. The findings observed in this group of patients suggest that TSO therapy has a moderate immunomodulatory impact in MS.58,59 Nevertheless, it is important to take into account the potential for unrelated gastrointestinal events. Excretory-secretory muscle larvae (ES L1) products of the parasite T. spiralis successfully ameliorate EAE in Dark Agouti rats. Prophylactic application of ES L1 caused significant (P < 0.05) amelioration of EAE by a shift to the Th2-type response in the periphery and the CNS, as well as activation of regulatory mechanisms. Unconventional CD4+CD25-Foxp3 + regulatory cells were identified in increased proportion (P < 0.001) both in the periphery and the CNS of rats treated with ES L1 before the induction of EAE, and a possible role for these cells in amelioration of the disease was suggested.60 Treatment with soluble egg product homogenate from the nematodes T. suis, S. mansoni and T. spiralis was demonstrated to suppress TNF-a and IL-12 secretion by TLR-activated human DCs and induced significant suppression of symptoms in a murine EAE model.61 Parasite antigens such as omega-1, a glycoprotein derived from S. mansoni eggs, helminth cystatins from Acanthocheilonema viteae, Brugia malayi, Nippostrongylus braisliensis and Onchocerca volvolus were able to induce TLR2 expression on both B cells and DCs.56 It is important to remember the requirement for early treatment to gain therapeutic effect. This is mostly because the symptomatic phase of EAE is characterized by extensive tissue damage, much of which may be irreversible. Also, the treatment must be continuous.62
2.3 Helminths and Lupus Systemic lupus erythematosus (SLE) is a multiorgan chronic autoimmune disease. Most patients have skin lesions (the most common is a butterfly rash) and over 90 % of patients suffer from joint involvement such as inflammatory arthritis. SLE may, however, affect the kidneys, lungs, nervous system and other organs as well. It is a multifactorial disease that depends on genetic and environmental factors (including exposure to ultraviolet light and infections).63,64
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Similarity between parasitic infections and autoimmune disorders was found.65 Autoantibodies such as antinuclear antibodies, double-stranded DNA, and anti-Smith antibodies, which are present in SLE, have been identified in the serum of patients infected with Schistosoma.66 Furthermore, antiribosomal P protein antibodies present in chronic Chagas heart disease, caused by Trypanosoma cruzi, were shown to cross-react with anti-Smith antibodies, which are present in early SLE.67 Genetic polymorphisms conferring susceptibility to SLE, more specifically the inhibitory receptor FcgRIIb, has been identified in African and Asian populations living in areas considered to be endemic to malaria (Plasmodium falciparum). This lupus-associated FcgRIIb polymorphism enhances phagocytosis of the parasite-infected erythrocytes. This suggests that a polymorphism predisposing to SLE may be gained through reduced susceptibility to malaria.68 Moreover, one study using a experimental lupus model of NZB/NZWXF1 mice showed that female mice infected with Toxoplasma gondii developed milder renal involvement and had a longer life span than noninfected mice. Lower amounts of IL-10 and IFN-g were found in spleen cells of the infected mice.69
2.4 Helminths and Type 1 Diabetes Type 1 diabetes (T1D) is considered a Th1-mediated autoimmune disease and is influenced by both genetic and environmental factors. These factors lead to the development of autoantibodies directed at various islet cell components including glutamic acid decarboxylase antibodies (GAD65), islet cell antibodies (ICA512/IA-2) and insulin antibodies, which eventually leads to the destruction of pancreatic insulin-secreting b-cells. The subsequent lack of insulin leads to increased blood and urine glucose. Classical symptoms are polyuria, polydipsia, polyphagia and weight loss.70 The incidence of T1D has dramatically increased in the developed world over the past several decades. A linkage between the high prevalence of T1D and improved sanitation was proposed and was discussed previously in the hygiene theory.1 During the past two decades the potential use of helminths and helminth-derived products in the prevention of T1D has gained attention. Following the discovery of the role of Tregs in maintaining self-tolerance,71,72 the correlation between Th1 cells (IL-2 and IFN-g) and the pathogenesis of T1D was established. The role of Th2 cells (IL-4 and IL-10) and Tregs (IL-10 and TGF-b) in protection against T1D was demonstrated as well.73
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The elevated number of Tregs in helminthic infection attenuates inflammatory response and subsequent tissue damage. Based on the hypothesis that the pathomechanism of T1D is related to the impaired immunoregulatory activity of diabetogenic T cells, leading to the development of autoimmunity, early work in the field showed helminthic infections can prevent T1D. This is based on the assumption that the Th2 immune bias would ultimately attenuate the Th1-mediated response that triggers diseases such as T1D.74 Infection by the gastrointestinal helminths T. spiralis and Heligmosomoides polygyrus among 4- to 6-week-old nonobese diabetic (NOD) mice, which is a model of T1D, elicited a Th2 response, demonstrated by increased IL-4 and immunoglobulin (Ig) E levels. This is in contrast to the Th1 response that accompanies the development of diabetes in NOD mice and suggests that the Th2 response induced by T. spiralis and H. polygyrus infection might protect the mice from the effects of Th1-mediated b-cell destruction. NOD mice infected with H. polygyrus remained free of diabetes over the entire experimental time course (36 to 37 weeks).75 Litomosoides sigmodontis filarial worms prevent the onset of diabetes in infected NOD mice. Six-week-old female NOD mice were infected with either 40 L3-stage larvae, adult female worms or adult male worms, and glucose concentrations were monitored over time. The onset of diabetes (glucose concentration >230 mg/dL) was prevented in all mice tested until the end of the experiment, when they were 25 weeks old. Protection against diabetes was associated with a Th2 shift, as IL-4 and IL-5 released from a-CD3/a-CD28-stimulated splenocytes was greater in mice infected with L. sigmodontis than in uninfected mice.76 A subsequent study tested whether infection with L. sigmodontis prevents diabetes onset in IL-4-deficient NOD mice and whether depletion or absence of Tregs, IL-10, or TGF-b alters helminth-mediated protection.77 The study demonstrated that L. sigmodontis–mediated protection against diabetes in NOD mice is not dependent on the induction of a type 2 immune shift but does require TGF-b. Helminthic infection prevented the development of diabetes in NOD mice, even in the absence of IL-4 (P < 0.01). S. mansoni eggs have been shown to prevent T1D when administered to 4- to 6-week-old NOD mice. None of the injected mice developed diabetes, whereas the control mice developed diabetes with a 70% incidence by 27 weeks of age (p < 0.005).78 Insulin autoantibodies spontaneously develop in NOD mice and prediabetic humans. Infected mice had insulin autoantibodies that were predominantly of the IgM isotype. Infection with S. mansoni prevented the class switch of anti-insulin antibody, which
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is normally seen in most NOD mice as they approach overt diabetes.79 The live eggs of S. mansoni actively secrete the glycoprotein omega-1, which has been shown to be capable of conditioning human monocyte-derived DCs in vitro to induce a Th2 response,80 thus regulating (shifting) the host immune response and aiding in the parasite’s survival as well as migration.79 The glycoprotein omega-1 alone has been shown to directly elicit human DCs to induce Th2 development from naı¨ve CD4+ T cells and, furthermore, inhibit the release of IL-12, therefore reducing the differentiation of Th1 cells.80 Omega-1 also has been shown to induce IL-4 production as well as to prime Foxp3+ Tregs in NOD mice CD4 + cells.81 Antigen-nonspecific IgE was purified from the roundworm Dirofilaria immitis, which induces IgE in mice and rats. Recombinant D. immitis antigen treatment of 6-week-old NOD female mice completely prevented insulitis and diabetes. It was also associated with a switching of the response from a Th1 to a Th2 profile,82 as was shown in the previously presented studies.
2.5 Helminths and Rheumatoid Arthritis Rheumatoid arthritis (RA) is a chronic inflammatory arthritis with an autoimmune mechanism. It is the most common inflammatory arthritis, affecting about 1 % of the population.83 Like other autoimmune diseases, it comprises genetic as well as environmental factors, of which smoking is the most prominent.84 The disease is typically polyarticular and manifests as stiffness, pain and swelling. Extra-articular involvement includes anemia, subcutaneous nodules (rheumatoid nodules), neuropathy, Sjo¨gren’s syndrome, vasculitis, renal disease and other extra-articular features. An immunological hallmark of the disease is the development of anticitrullinated protein antibodies.85 Moreover, there is a predominance of Th1 cells, mostly CD4 +, and a deficiency of Th2 and Tregs. The T cells, and consequently the anticitrullinated protein antibodies, target the deaminated areas within rheumatoid joints.86,87 The first study associating helminthic infection and joint disease, dating back to 1975, was a surprising observation that rats infected with the nematode Syphacia obvelata developed milder complete Freund’s adjuvant– induced arthritis.88 Since then, studies have used various helminth models for investigating joint inflammation. The most commonly used model of arthritis is the type II collagen (Col II) model, which provokes multijoint inflammation. One such study demonstrated that infection with S. mansoni reduces the severity of Col
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II–induced arthritis in male DBA/1 mice. S. mansoni infection suppresses systemic and local proinflammatory mediators, thus leading to significantly less synovial hyperplasia, inflammatory cell recruitment and bone/cartilage destruction. Levels of IgG2a, which is involved in the pathology of Col II–induced arthritis, were decreased and polyclonal-stimulated splenic T cells expressed lower amounts of IFN-g, IL-17A and TNF-a. Higher amounts of IL-4 and IL-10 also were measured in comparison with naı¨ve mice immunized with Col II.89 C57BL/6 mice prophylactically infected with the rat intestinal tapeworm Hymenolepis diminuta (10 cysticercoids in 100 mm of phosphatebuffered saline) showed significantly (P < 0.05) attenuated complete Freund’s adjuvant–induced arthritis. Treatment with helminthic infection was as effective as treatment with dexamethasone or indomethacin (P < 0.05), the mainstay of treatment for arthritis. The infected mice showed reduced knee swelling, and, in addition, activated splenic T cells showed the expression of higher levels of IL-4 and IL-10.90 RA is associated with a Th1 response and a general increase in proinflammatory cytokines such as IL-6, IFN-g and TNF-a. Moreover, H. polygyrus excretory-secretory antigen induces the de novo expression of Foxp3 Tregs91,92 and induces the activity of alternatively activated macrophages.93 Early studies showed that the rodent filarial nematode A. viteae secretes ES-62, an immunomodulatory glycoprotein surrounded by a phosphorylcholine moiety attached to the protein by glycans.94 ES-62 induced a shift from a Th1 to a Th2 response and attenuated an RA-like disease in collageninduced arthritis (CIA). It elevated the production of the anti-inflammatory cytokine IL-10 and reduced levels of IFN-g and IL-12, which are proinflammatory cytokines.95–97 Cultures of human patients with RA synovial fluid showed reduced levels (P < 0.05) of TNF-a and IFN-g secretion in the presence of ES-62, whereas peripheral blood smears from the patients exhibited mononuclear cells with low IFN-g secretion after treatment with ES-62.98,99 Use of recombinant ES-62, the whole ES-62 molecule and a synthetic phosphorylcholine–ovalbumin conjugate showed that the clinical score of CIA was affected only PC-OVA or ES-62 but not recombinant ES-62. This fact led to the idea that the common denominator inducing tolerance is phosphorylcholine.100 Furthermore, Al-Riyami et al.101 designed a small-molecule analogue—a sulfone-containing phosphorylcholine analogue (11a)—and provided proof of concept in a murine CIA model. 11a Was as effective as ES-62 in protecting DBA/1 mice from developing CIA and mirrored its mechanism of action as an anti-inflammatory antigen.
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2.6 Helminths and Graves’ Disease Graves’ disease is considered an autoimmune syndrome in which hyperthyroidism is present in almost all patients. This thyroid disease is characterized by the presence of thyroid-stimulating hormone receptor (TSHR) antibodies,102 leading to follicular dysplasia, lymphocytic infiltration and, in most cases, diffuse enlargement of the gland. TSHR antibodies are detectable in almost all patients with Graves’ disease.103 A murine model of Graves’ disease has been described by the immunization of mice with thyrotropin receptor complementary DNA.104 From reviewing the literature, we found only one study that examined the association between helminthic infection and Graves’ disease. Graves’ disease was once thought to be a Th2-type immune response, but recent studies have described an Th1-type as well as a Th2-type response.105,106 Based on the ability of helminthic infection to polarize the immune response towards a Th2 type, a soluble homogenate of S. mansoni worm product and a-galactosylceramide (a-GalCer) has been used prophylactically in a murine model. a-GalCer is one of many glycoconjugates expressed by S. mansoni worms and live eggs.107 a-GalCer stimulates natural killer T cells to rapidly produce both Th1 and Th2 cytokines, but at a later time point and with repeated doses, a-GalCer promotes the development of a Th2 immune response, thus protecting against various autoimmune diseases. The results showed that both S. mansoni products and a-GalCer protected from Grave’s disease, mainly by suppressing a Th1-type anti-TSHR immune response at the time of antigen priming. This occurred by increasing the levels of the anti-inflammatory cytokine IL-10.108
3 CONCLUSION In Western countries a strong correlation exists between improved sanitation and hygiene and the significant increase in the prevalence of autoimmune and autoinflammatory diseases. Moreover, a reverse correlation was reported between the high prevalence of helminths and autoimmune diseases in certain geographic areas. Different helminths were proven to secrete different molecules that enhance tolerance in the human immune system to survive. Therefore, many researchers harness helminth secretory molecules to develop novel therapeutic compounds to treat autoimmune diseases.
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REFERENCES 1. Moroni L, Bianchi I, Lleo A. Geoepidemiology, gender and autoimmune disease. Autoimmun Rev 2012;11:A386–92. 2. Okada H, Kuhn C, Feillet H, Bach JF. The ‘hygiene hypothesis’ for autoimmune and allergic diseases: an update. Clin Exp Immunol 2010;160:1–9. 3. van Panhuis WG, Grefenstette J, Jung SY, Chok NS, Cross A, Eng H, et al. Contagious diseases in the united states from 1888 to the present. N Engl J Med 2013;369:2152–8. 4. von Mutius E. Allergies, infections and the hygiene hypothesis—the epidemiological evidence. Immunobiology 2007;212:433–9. 5. Strachan DP. Hay fever, hygiene, and household size. BMJ 1989;299:1259–60. 6. Carpenter L, Beral V, Strachan D, Ebi-Kryston KL, Inskip H. Respiratory symptoms as predictors of 27 year mortality in a representative sample of British adults. BMJ 1989;299:357–61. 7. Lynch NR, Hagel I, Perez M, Di Prisco MC, Lopez R, Alvarez N. Effect of anthelmintic treatment on the allergic reactivity of children in a tropical slum. J Allergy Clin Immunol 1993;92:404–11. 8. van den Biggelaar AH, Rodrigues LC, van Ree R, van der Zee JS, HoeksmaKruize YC, Souverijn JH, et al. Long-term treatment of intestinal helminths increases mite skin-test reactivity in Gabonese schoolchildren. J Infect Dis 2004;189:892–900. 9. Flohr C, Tuyen LN, Lewis S, Quinnell R, Minh TT, Liem HT, et al. Poor sanitation and helminth infection protect against skin sensitization in Vietnamese children: a crosssectional study. J Allergy Clin Immunol 2006;118:1305–11. 10. Bitti PP, Murgia BS, Ticca A, Ferrai R, Musu L, Piras ML, et al. Association between the ancestral haplotype hla a30b18dr3 and multiple sclerosis in central Sardinia. Genet Epidemiol 2001;20:271–83. 11. Sotgiu S, Angius A, Embry A, Rosati G, Musumeci S. Hygiene hypothesis: innate immunity, malaria and multiple sclerosis. Med Hypotheses 2008;70:819–25. 12. Francis L, Perl A. Infection in systemic lupus erythematosus: friend or foe? Int J Clin Rheumtol 2010;5:59–74. 13. Butcher GA, Clark IA. Sle and malaria: another look at an old idea. Parasitol Today 1990;6:259–61. 14. Kondrashova A, Seiskari T, Ilonen J, Knip M, Hyoty H. The ‘hygiene hypothesis’ and the sharp gradient in the incidence of autoimmune and allergic diseases between Russian karelia and Finland. APMIS 2013;121:478–93. 15. Seiskari T, Kondrashova A, Viskari H, Kaila M, Haapala AM, Aittoniemi J, et al. Allergic sensitization and microbial load—a comparison between Finland and Russian karelia. Clin Exp Immunol 2007;148:47–52. 16. McSorley HJ, Maizels RM. Helminth infections and host immune regulation. Clin Microbiol Rev 2012;25:585–608. 17. Ben-Ami Shor D, Harel M, Eliakim R, Shoenfeld Y. The hygiene theory harnessing helminths and their ova to treat autoimmunity. Clin Rev Allergy Immunol 2013;45:211–16. 18. Assadsangabi A, Lobo AJ. Diagnosing and managing inflammatory bowel disease. Practitioner 2013;257:13–82. 19. Mayer L. Evolving paradigms in the pathogenesis of ibd. J Gastroenterol 2010;45:9–16. 20. Elliott DE, Urban JJ, Argo CK, Weinstock JV. Does the failure to acquire helminthic parasites predispose to Crohn’s disease? FASEB J 2000;14:1848–55. 21. Fiasse R, Latinne D. Intestinal helminths: a clue explaining the low incidence of inflammatory bowel diseases in subsaharan Africa? Potential benefits and hazards of helminth therapy. Acta Gastroenterol Belg 2006;69:418–22.
212
Infection and autoimmunity
22. Walk ST, Blum AM, Ewing SA, Weinstock JV, Young VB. Alteration of the murine gut microbiota during infection with the parasitic helminth heligmosomoides polygyrus. Inflamm Bowel Dis 2010;16:1841–9. 23. Weinstock JV. Autoimmunity: the worm returns. Nature 2012;491:183–5. 24. Hang L, Setiawan T, Blum AM, Urban J, Stoyanoff K, Arihiro S, et al. Heligmosomoides polygyrus infection can inhibit colitis through direct interaction with innate immunity. J Immunol 2010;185:3184–9. 25. Elliott DE, Setiawan T, Metwali A, Blum A, Urban Jr. JF, Weinstock JV. Heligmosomoides polygyrus inhibits established colitis in il-10-deficient mice. Eur J Immunol 2004;34:2690–8. 26. Wang LJ, Cao Y, Shi HN. Helminth infections and intestinal inflammation. World J Gastroenterol 2008;14:5125–32. 27. Cassinotti A, Sarzi-Puttini P, Fichera M, Shoenfeld Y, de Franchis R, Ardizzone S. Immunity, autoimmunity and inflammatory bowel disease. Autoimmun Rev 2014;13:1–2. 28. Weinstock JV, Summers RW, Elliott DE. Role of helminths in regulating mucosal inflammation. Springer Semin Immunopathol 2005;27:249–71. 29. Scholmerich J. Trichuris suis ova in inflammatory bowel disease. Dig Dis 2013;31:391–5. 30. Elliott DE, Metwali A, Leung J, Setiawan T, Blum AM, Ince MN, et al. Colonization with heligmosomoides polygyrus suppresses mucosal il-17 production. J Immunol 2008;181:2414–9. 31. Fitzpatrick LR. Inhibition of il-17 as a pharmacological approach for ibd. Int Rev Immunol 2013;32:544–55. 32. Mohammadi M, Zahedi MJ, Nikpoor AR, Baneshi MR, Hayatbakhsh MM. Interleukin-17 serum levels and tlr4 polymorphisms in ulcerative colitis. Iran J Immunol 2013;10:83–92. 33. Elliott DE, Li J, Blum A, Metwali A, Qadir K, Urban Jr. JF, et al. Exposure to schistosome eggs protects mice from TNBS-induced colitis. Am J Physiol Gastrointest Liver Physiol 2003;284:G385–91. 34. Moreels TG, Nieuwendijk RJ, De Man JG, De Winter BY, Herman AG, Van Marck EA, et al. Concurrent infection with schistosoma mansoni attenuates inflammation induced changes in colonic morphology, cytokine levels, and smooth muscle contractility of trinitrobenzene sulphonic acid induced colitis in rats. Gut 2004;53:99–107. 35. Ruyssers NE, De Winter BY, De Man JG, Loukas A, Pearson MS, Weinstock JV, et al. Therapeutic potential of helminth soluble proteins in TNBS-induced colitis in mice. Inflamm Bowel Dis 2009;15:491–500. 36. Ruyssers NE, De Winter BY, De Man JG, Ruyssers ND, Van Gils AJ, Loukas A, et al. Schistosoma mansoni proteins attenuate gastrointestinal motility disturbances during experimental colitis in mice. World J Gastroenterol 2010;16:703–12. 37. Beer RJ. The relationship between trichuris trichiura (linnaeus 1758) of man and trichuris suis (schrank 1788) of the pig. Res Vet Sci 1976;20:47–54. 38. Sandborn WJ, Elliott DE, Weinstock J, Summers RW, Landry-Wheeler A, Silver N, et al. Randomised clinical trial: the safety and tolerability of trichuris suis ova in patients with Crohn’s disease. Aliment Pharmacol Ther 2013;38:255–63. 39. Summers RW, Elliott DE, Qadir K, Urban Jr. JF, Thompson R, Weinstock JV. Trichuris suis seems to be safe and possibly effective in the treatment of inflammatory bowel disease. Am J Gastroenterol 2003;98:2034–41. 40. Summers RW, Elliott DE, Urban Jr. JF, Thompson R, Weinstock JV. Trichuris suis therapy in Crohn’s disease. Gut 2005;54:87–90. 41. Summers RW, Elliott DE, Urban Jr. JF, Thompson RA, Weinstock JV. Trichuris suis therapy for active ulcerative colitis: a randomized controlled trial. Gastroenterology 2005;128:825–32.
The protective role of helminths in autoimmunity
213
42. Summers RW, Elliott DE, Weinstock JV. Is there a role for helminths in the therapy of inflammatory bowel disease? Nat Clin Pract Gastroenterol Hepatol 2005;2:62–3. 43. Kradin RL, Badizadegan K, Auluck P, Korzenik J, Lauwers GY. Iatrogenic trichuris suis infection in a patient with Crohn disease. Arch Pathol Lab Med 2006;130: 718–20. 44. Motomura Y, Wang H, Deng Y, El-Sharkawy RT, Verdu EF, Khan WI. Helminth antigen-based strategy to ameliorate inflammation in an experimental model of colitis. Clin Exp Immunol 2009;155:88–95. 45. Sun S, Wang X, Wu X, Zhao Y, Wang F, Liu X, et al. Toll-like receptor activation by helminths or helminth products to alleviate inflammatory bowel disease. Parasit Vectors 2011;4:186. 46. Multiple sclerosis: national clinical guideline for diagnosis and management in primary and secondary care. NICE Clinical Guidelines, No. 8. London: National Collaborating Centre for Chronic Conditions (UK); 2004. 47. Stuve O, Oksenberg J. Multiple sclerosis overview. In: Pagon RA, Adam MP, Bird TD, Dolan CR, Fong CT, Stephens K, editors. Genereviews; 1993, GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993–2014. Available from: http:// www.ncbi.nlm.nih.gov/books/NBK1316/. 48. Correale J, Farez MF. The impact of environmental infections (parasites) on ms activity. Mult Scler 2011;17:1162–9. 49. Rosati G. The prevalence of multiple sclerosis in the world: an update. Neurol Sci 2001;22:117–39. 50. Rangachari M, Kuchroo VK. Using eae to better understand principles of immune function and autoimmune pathology. J Autoimmun 2013;45:31–9. 51. La Flamme AC, Ruddenklau K, Backstrom BT. Schistosomiasis decreases central nervous system inflammation and alters the progression of experimental autoimmune encephalomyelitis. Infect Immun 2003;71:4996–5004. 52. Reyes JL, Espinoza-Jimenez AF, Gonzalez MI, Verdin L, Terrazas LI. Taenia crassiceps infection abrogates experimental autoimmune encephalomyelitis. Cell Immunol 2011;267:77–87. 53. Correale J, Farez M. Association between parasite infection and immune responses in multiple sclerosis. Ann Neurol 2007;61:97–108. 54. Correale J, Farez MF. The impact of parasite infections on the course of multiple sclerosis. J Neuroimmunol 2011;233:6–11. 55. Correale J, Farez M, Razzitte G. Helminth infections associated with multiple sclerosis induce regulatory b cells. Ann Neurol 2008;64:187–99. 56. Correale J, Farez MF. Does helminth activation of toll-like receptors modulate immune response in multiple sclerosis patients? Front Cell Infect Microbiol 2012;2:112. 57. Sewell D, Qing Z, Reinke E, Elliot D, Weinstock J, Sandor M, et al. Immunomodulation of experimental autoimmune encephalomyelitis by helminth ova immunization. Int Immunol 2003;15:59–69. 58. Benzel F, Erdur H, Kohler S, Frentsch M, Thiel A, Harms L, et al. Immune monitoring of trichuris suis egg therapy in multiple sclerosis patients. J Helminthol 2012;86:339–47. 59. Fleming JO, Isaak A, Lee JE, Luzzio CC, Carrithers MD, Cook TD, et al. Probiotic helminth administration in relapsing-remitting multiple sclerosis: a phase 1 study. Mult Scler 2011;17:743–54. 60. Sofronic-Milosavljevic LJ, Radovic I, Ilic N, Majstorovic I, Cvetkovic J, GrudenMovsesijan A. Application of dendritic cells stimulated with trichinella spiralis excretory-secretory antigens alleviates experimental autoimmune encephalomyelitis. Med Microbiol Immunol 2013;202:239–49. 61. Kuijk LM, Klaver EJ, Kooij G, van der Pol SM, Heijnen P, Bruijns SC, et al. Soluble helminth products suppress clinical signs in murine experimental autoimmune
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62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80.
Infection and autoimmunity
encephalomyelitis and differentially modulate human dendritic cell activation. Mol Immunol 2012;51:210–18. Fleming JO. Helminth therapy and multiple sclerosis. Int J Parasitol 2013;43:259–74. Shoenfeld Y, Zandman-Goddard G, Stojanovich L, Cutolo M, Amital H, Levy Y, et al. The mosaic of autoimmunity: hormonal and environmental factors involved in autoimmune diseases—2008. Isr Med Assoc J 2008;10:8–12. Sherer Y, Gorstein A, Fritzler MJ, Shoenfeld Y. Autoantibody explosion in systemic lupus erythematosus: more than 100 different antibodies found in sle patients. Semin Arthritis Rheum 2004;34:501–37. Zandman-Goddard G, Shoenfeld Y. Parasitic infection and autoimmunity. Lupus 2009;18:1144–8. Rahima D, Tarrab-Hazdai R, Blank M, Arnon R, Shoenfeld Y. Anti-nuclear antibodies associated with schistosomiasis and anti-schistosomal antibodies associated with sle. Autoimmunity 1994;17:127–41. Levitus G, Hontebeyrie-Joskowicz M, Van Regenmortel MH, Levin MJ. Humoral autoimmune response to ribosomal p proteins in chronic chagas heart disease. Clin Exp Immunol 1991;85:413–7. Clatworthy MR, Willcocks L, Urban B, Langhorne J, Williams TN, Peshu N, et al. Systemic lupus erythematosus-associated defects in the inhibitory receptor fcgriib reduce susceptibility to malaria. Proc Natl Acad Sci USA 2007;104:7169–74. Chen M, Aosai F, Norose K, Mun HS, Ishikura H, Hirose S, et al. Toxoplasma gondii infection inhibits the development of lupus-like syndrome in autoimmune (New Zealand black x New Zealand white) f1 mice. Int Immunol 2004;16:937–46. Donath MY, Hess C, Palmer E. What is the role of autoimmunity in type 1 diabetes? A clinical perspective. Diabetologia 2014;57:653–5. Hori I, Kishida Y. Quantitative changes in nuclear pores and chromatoid bodies induced by neuropeptides during cell differentiation in the planarian dugesia japonica. J Submicrosc Cytol Pathol 2003;35:439–44. Wing K, Sakaguchi S. Regulatory t cells exert checks and balances on self tolerance and autoimmunity. Nat Immunol 2010;11:7–13. Kikodze N, Pantsulaia I, Rekhviashvili K, Iobadze M, Jakhutashvili N, Pantsulaia N, et al. Cytokines and t regulatory cells in the pathogenesis of type 1 diabetes. Georgian Med News 2013;222:29–35. Taylor MD, van der Werf N, Maizels RM. T cells in helminth infection: the regulators and the regulated. Trends Immunol 2012;33:181–9. Saunders KA, Raine T, Cooke A, Lawrence CE. Inhibition of autoimmune type 1 diabetes by gastrointestinal helminth infection. Infect Immun 2007;75:397–407. Hubner MP, Stocker JT, Mitre E. Inhibition of type 1 diabetes in filaria-infected nonobese diabetic mice is associated with a t helper type 2 shift and induction of foxp3+ regulatory t cells. Immunology 2009;127:512–22. Hubner MP, Shi Y, Torrero MN, Mueller E, Larson D, Soloviova K, et al. Helminth protection against autoimmune diabetes in nonobese diabetic mice is independent of a type 2 immune shift and requires tgf-beta. J Immunol 2012;188:559–68. Zaccone P, Fehervari Z, Jones FM, Sidobre S, Kronenberg M, Dunne DW, et al. Schistosoma mansoni antigens modulate the activity of the innate immune response and prevent onset of type 1 diabetes. Eur J Immunol 2003;33:1439–49. Cooke A, Tonks P, Jones FM, O’Shea H, Hutchings P, Fulford AJ, et al. Infection with schistosoma mansoni prevents insulin dependent diabetes mellitus in non-obese diabetic mice. Parasite Immunol 1999;21:169–76. Everts B, Perona-Wright G, Smits HH, Hokke CH, van der Ham AJ, Fitzsimmons CM, et al. Omega-1, a glycoprotein secreted by schistosoma mansoni eggs, drives th2 responses. J Exp Med 2009;206:1673–80.
The protective role of helminths in autoimmunity
215
81. Zaccone P, Burton OT, Gibbs SE, Miller N, Jones FM, Schramm G, et al. The s. Mansoni glycoprotein omega-1 induces foxp3 expression in nod mouse cd4(+) t cells. Eur J Immunol 2011;41:2709–18. 82. Imai S, Tezuka H, Fujita K. A factor of inducing ige from a filarial parasite prevents insulin-dependent diabetes mellitus in nonobese diabetic mice. Biochem Biophys Res Commun 2001;286:1051–8. 83. Rothschild BM, Turner KR, DeLuca MA. Symmetrical erosive peripheral polyarthritis in the late archaic period of Alabama. Science 1988;241:1498–501. 84. Lundstrom E, Kallberg H, Alfredsson L, Klareskog L, Padyukov L. Gene-environment interaction between the drb1 shared epitope and smoking in the risk of anti-citrullinated protein antibody-positive rheumatoid arthritis: all alleles are important. Arthritis Rheum 2009;60:1597–603. 85. Wegner N, Lundberg K, Kinloch A, Fisher B, Malmstrom V, Feldmann M, et al. Autoimmunity to specific citrullinated proteins gives the first clues to the etiology of rheumatoid arthritis. Immunol Rev 2010;233:34–54. 86. De Rycke L, Nicholas AP, Cantaert T, Kruithof E, Echols JD, Vandekerckhove B, et al. Synovial intracellular citrullinated proteins colocalizing with peptidyl arginine deiminase as pathophysiologically relevant antigenic determinants of rheumatoid arthritis-specific humoral autoimmunity. Arthritis Rheum 2005;52:2323–30. 87. Takizawa Y, Suzuki A, Sawada T, Ohsaka M, Inoue T, Yamada R, et al. Citrullinated fibrinogen detected as a soluble citrullinated autoantigen in rheumatoid arthritis synovial fluids. Ann Rheum Dis 2006;65:1013–20. 88. Pearson DJ, Taylor G. The influence of the nematode syphacia oblevata on adjuvant arthritis in the rat. Immunology 1975;29:391–6. 89. Osada Y, Shimizu S, Kumagai T, Yamada S, Kanazawa T. Schistosoma mansoni infection reduces severity of collagen-induced arthritis via down-regulation of proinflammatory mediators. Int J Parasitol 2009;39:457–64. 90. Shi M, Wang A, Prescott D, Waterhouse CC, Zhang S, McDougall JJ, et al. Infection with an intestinal helminth parasite reduces Freund’s complete adjuvant-induced monoarthritis in mice. Arthritis Rheum 2011;63:434–44. 91. Grainger JR, Smith KA, Hewitson JP, McSorley HJ, Harcus Y, Filbey KJ, et al. Helminth secretions induce de novo t cell foxp3 expression and regulatory function through the tgf-beta pathway. J Exp Med 2010;207:2331–41. 92. Carranza F, Falcon CR, Nunez N, Knubel C, Correa SG, Bianco I, et al. Helminth antigens enable cpg-activated dendritic cells to inhibit the symptoms of collagen-induced arthritis through foxp3 + regulatory t cells. PLoS One 2012;7:e40356. 93. Espinoza-Jimenez A, Rivera-Montoya I, Cardenas-Arreola R, Moran L, Terrazas LI. Taenia crassiceps infection attenuates multiple low-dose streptozotocin-induced diabetes. J Biomed Biotechnol 2010;2010:850541. 94. Harnett W, Harnett MM, Leung BP, Gracie JA, McInnes IB. The anti-inflammatory potential of the filarial nematode secreted product, es-62. Curr Top Med Chem 2004;4:553–9. 95. Marshall FA, Grierson AM, Garside P, Harnett W, Harnett MM. Es-62, an immunomodulator secreted by filarial nematodes, suppresses clonal expansion and modifies effector function of heterologous antigen-specific t cells in vivo. J Immunol 2005;175:5817–26. 96. Stepek G, Auchie M, Tate R, Watson K, Russell DG, Devaney E, et al. Expression of the filarial nematode phosphorylcholine-containing glycoprotein, es62, is stage specific. Parasitology 2002;125:155–64. 97. Harnett W, Harnett MM. Filarial nematode secreted product es-62 is an anti-inflammatory agent: therapeutic potential of small molecule derivatives and es-62 peptide mimetics. Clin Exp Pharmacol Physiol 2006;33:511–18.
216
Infection and autoimmunity
98. McInnes IB, Leung BP, Harnett M, Gracie JA, Liew FY, Harnett W. A novel therapeutic approach targeting articular inflammation using the filarial nematode-derived phosphorylcholine-containing glycoprotein es-62. J Immunol 2003;171:2127–33. 99. McInnes IB, Schett G. Cytokines in the pathogenesis of rheumatoid arthritis. Nat Rev Immunol 2007;7:429–42. 100. Harnett MM, Kean DE, Boitelle A, McGuiness S, Thalhamer T, Steiger CN, et al. The phosphorycholine moiety of the filarial nematode immunomodulator es-62 is responsible for its anti-inflammatory action in arthritis. Ann Rheum Dis 2008;67:518–23. 101. Al-Riyami L, Pineda MA, Rzepecka J, Huggan JK, Khalaf AI, Suckling CJ, et al. Designing anti-inflammatory drugs from parasitic worms: a synthetic small molecule analogue of the acanthocheilonema viteae product es-62 prevents development of collagen-induced arthritis. J Med Chem 2013;56:9982–10002. 102. Latif R, Morshed SA, Zaidi M, Davies TF. The thyroid-stimulating hormone receptor: impact of thyroid-stimulating hormone and thyroid-stimulating hormone receptor antibodies on multimerization, cleavage, and signaling. Endocrinol Metab Clin North Am 2009;38:319–41, viii. 103. Lytton SD, Kahaly GJ. Bioassays for tsh-receptor autoantibodies: an update. Autoimmun Rev 2010;10:116–22. 104. Costagliola S, Many MC, Denef JF, Pohlenz J, Refetoff S, Vassart G. Genetic immunization of outbred mice with thyrotropin receptor cdna provides a model of Graves’ disease. J Clin Invest 2000;105:803–11. 105. Dogan RN, Vasu C, Holterman MJ, Prabhakar BS. Absence of il-4, and not suppression of the th2 response, prevents development of experimental autoimmune Graves’ disease. J Immunol 2003;170:2195–204. 106. Nagayama Y, Mizuguchi H, Hayakawa T, Niwa M, McLachlan SM, Rapoport B. Prevention of autoantibody-mediated graves’-like hyperthyroidism in mice with il-4, a th2 cytokine. J Immunol 2003;170:3522–7. 107. Makaaru CK, Damian RT, Smith DF, Cummings RD. The human blood fluke schistosoma mansoni synthesizes a novel type of glycosphingolipid. J Biol Chem 1992;267:2251–7. 108. Nagayama Y, Watanabe K, Niwa M, McLachlan SM, Rapoport B. Schistosoma mansoni and alpha-galactosylceramide: prophylactic effect of th1 immune suppression in a mouse model of Graves’ hyperthyroidism. J Immunol 2004;173:2167–73.