- Email: [email protected]
Immunomodulation in the pathogenesis of Bordetella pertussis infection and disease
Immunomodulation in the pathogenesis of Bordetella pertussis infection and disease Nicholas H Carbonetti Bordetella pertussis infection of the airways causes the disease pertussis (or whooping cough). The infection can be fatal in infants, but in older children, adolescents and adults usually results in a chronic cough of varying severity that persists long after clearance of the infection. The cause of the cough is unknown, but is presumably a result of the pathogenic effects of one or more of the various virulence factors produced by this bacterium. Accumulating recent evidence indicates that the majority of the virulence-associated effects of these factors is devoted to suppression and modulation of the host immune response, which can be skewed towards the recently described Th17 profile. Although the interplay between virulence factors and immune mechanisms might have evolved to benefit both partners in the host–pathogen interaction, it could also contribute to the severe disease pathology associated with this infection. Addresses Department of Microbiology & Immunology, University of Maryland School of Medicine, 660 W Redwood St, HH 324 Baltimore, MD 21201, USA Corresponding author: Carbonetti, Nicholas H ([email protected])
Current Opinion in Pharmacology 2007, 7:272–278 This review comes from a themed issue on Respiratory pharmacology Edited by Brendan Canning and Stephen Farmer Available online 5th April 2007 1471-4892/$ – see front matter # 2006 Elsevier Ltd. All rights reserved. DOI 10.1016/j.coph.2006.12.004
Introduction Bordetella pertussis is a Gram-negative bacterial pathogen that infects the human respiratory tract and causes the disease pertussis (or whooping cough). A comprehensive review on B. pertussis [1] and other useful reviews on the organism and disease have been published recently [2,3]. Although pertussis was traditionally considered a childhood disease, recent surveys and investigations have revealed that large numbers of older children, adolescents and adults are also infected and suffer from cough disease, causing serious public health issues. The classical disease symptom is a paroxysmal cough with whooping and vomiting, which is most frequently observed in unvaccinated infants. Whooping is less common in older individuals, in which the severity of cough varies widely. Apnea is another frequent problem of the disease in infants, and other Current Opinion in Pharmacology 2007, 7:272–278
complications include pneumonia, hypoxia, seizures, encephalopathy and secondary respiratory infections. Another hallmark of pertussis cough disease is its longevity, typically lasting several weeks (the Chinese term for pertussis is ‘the cough of a hundred days’) with gradually decreasing frequency and severity. The pathology of the airways in non-fatal cases is poorly characterized, although mucus hypersecretion is common. Pathological findings from postmortem observations, experimental animal infections and organ culture experiments include epithelial and ciliary damage, bronchopneumonia, pulmonary edema and focal hemorrhage. What causes the cough pathology of pertussis? In truth, we have little or no evidence to answer this question. Furthermore, despite detailed molecular knowledge of several virulence-associated factors of B. pertussis, there remain significant gaps in our understanding of the pathogenesis of this infection and disease. Contributing to this problem is the lack of either experimental human challenge studies or small animal models of the cough disease after B. pertussis infection. The most frequently used animal model for this infection is the mouse intranasal or aerosol inoculation model. Although overt symptomatic disease is not observed (mice cannot cough), several characteristics of the human infection are reproduced in this model, including multiplication and clearance of bacteria, limitation of infection to the respiratory tract, increased severity of infection in young animals, and various systemic physiological and neurological changes; the model can also be useful for the preclinical assessment of acellular pertussis vaccine efficacy [4]. This model has been particularly informative on the nature of protective immune responses elicited by B. pertussis infection and pertussis vaccination [4], and the availability of immunodeficient mice, developed either by genetic mutation or by chemical treatment, has facilitated further understanding of the interplay between the bacterial pathogen and host immunity. This review focuses on the pathogenesis of B. pertussis infection, with a particular emphasis on the immune suppression, evasion and subversion mechanisms employed by this pathogen, as revealed by recent literature. It appears that much of the activity of B. pertussis virulence factors is dedicated to this ‘anti-immunology’ aspect of pathogenesis, in common with other bacterial and viral pathogens as outlined in a recent review [5]. In addition, there is speculation that these immunomodulatory virulence mechanisms may not only aid B. pertussis infection www.sciencedirect.com
Immunomodulation in the pathogenesis of Bordetella pertussis infection and disease Carbonetti 273
Figure 1
Summary of infection of the respiratory tract by B. pertussis and its immunomodulatory effects.
but might also be crucially involved in pertussis disease pathogenesis.
B. pertussis virulence factors and immunomodulation This section provides a brief overview of several B. pertussis virulence factors, along with some of their immunomodulatory properties (Figure 1). Filamentous hemagglutinin (FHA) is considered to be the major surface structure mediating adherence to host cells, primarily to cilia on the airway ciliated epithelium. However, a recent study of the adherence of B. bronchiseptica (the closely related animal pathogen) to rabbit tracheal epithelial tissue, which measured real-time bacterial binding to cilia over the first four minutes after exposure, showed that loss of any one of several surface or secreted factors resulted in only partial loss of adherence, suggesting that multiple factors might contribute to the binding process [6]. This binding might be indirectly controlled through FHA, however, as another study suggested that secreted adenylate cyclase toxin (ACT) modifies a heparin-inhibitable carbohydrate binding domain of FHA to enhance www.sciencedirect.com
its ability to mediate adherence to cultured lung epithelial cells [7], presumably through a direct interaction between the two factors (previously described in [8]). In addition to its role in adherence, FHA has previously been shown to have immunosuppressive and immunomodulatory activities. B. pertussis infection of mice generated FHA-specific T regulatory lymphocytes that secreted interleukin (IL)-10 and suppressed protective T helper lymphocyte type I (Th1) responses against the pathogen [9]. In addition, antibodies to FHA in convalescent human serum were found to reduce the phagocytosis of B. pertussis by human neutrophils [10]. ACT is a secreted toxin that targets host phagocytic cells by binding complement receptor 3 (CR3; CD11b/CD18), forming membrane pores and raising intracellular cAMP levels through its adenylate cyclase domain [11,12]. ACTdeficient mutants of B. pertussis were more efficiently phagocytosed by human neutrophils [13] and achieved lower bacterial loads in the respiratory tract of a mouse intranasal infection model than did a wild-type strain [14]. Recent findings have shown that ACT can upregulate major histocompatibility complex class II and Current Opinion in Pharmacology 2007, 7:272–278
274 Respiratory
costimulatory molecules on dendritic cells (DCs), inducing a semi-mature state that decreases proinflammatory cytokine production [15–17]. Interestingly, these effects were caused by the adenylate cyclase activity of the toxin, whereas cytotoxic effects of ACT were also associated with its pore-forming activity [12,15,18]. Tracheal cytotoxin (TCT) is a disaccharide-tetrapeptide fragment of peptidoglycan released by B. pertussis at relatively high levels. Purified TCT, in synergy with lipopolysaccharide (LPS), damages ciliated airway epithelial cells through production of IL-1a and nitric oxide [19] and has deleterious effects on neutrophils [20]. Recent studies have shown that TCT stimulates responses in immune cells through microbial pattern-recognition molecules that interact with peptidoglycan and its derivatives. In mice, these responses were dependent upon the intracellular receptor Nod1; however, human Nod1 detected TCT poorly [21]. Instead, TCT binds human and Drosophila peptidoglycan recognition proteins, which (at least in Drosophila cells) potently activates an immune response pathway [22,23,24]. Therefore, TCT might also contribute to overall immunomodulation during B. pertussis infection. B. bronchiseptica expresses a type III secretion system (TTSS) that directly injects effector proteins (which are toxic for macrophage and epithelial cells in culture) into host cells, and that contributes to persistent respiratory infection in animal models [25,26]. The TTSS also possesses several immunosuppressive properties, resulting in modulation of DC maturation (in synergy with ACT) and migration to lymph nodes [17,27], macrophage activation [28], interferon-g production [27,29] and airway b-defensin production [30]. However, whether this is relevant to B. pertussis infection is unknown, as it is unclear whether B. pertussis expresses a TTSS.
Immunosuppression by pertussis toxin Pertussis toxin (PT) is another secreted toxin uniquely produced by B. pertussis which ADP-ribosylates several heterotrimeric G proteins in mammalian cells, disrupting signaling pathways with a wide range of downstream effects [31]. PT is perhaps the most enigmatic virulence factor of B. pertussis: although considered to be crucial for virulence, its role in promoting respiratory infection and disease has remained elusive. PT has long been known to cause systemic symptoms associated with pertussis disease, such as lymphocytosis, insulinemia/hypoglycemia and histamine sensitivity [32], but it was unclear from previous studies whether PT contributed to local events of respiratory infection and disease. However, recent studies using the mouse intranasal infection model indicate that PT is important in the very early stages after inoculation of bacteria. PT-deficient mutant strains showed reduced levels of airway infection 24 h postinoculation and, whereas co-administration of purified PT enhanced infection by the mutant strain, PT administration 24 h after inoculation had no enhancing effect [33]. One possible mechanism of action for PT is the Current Opinion in Pharmacology 2007, 7:272–278
delay of neutrophil recruitment and influx to the airways, as two groups have found that this response occurs earlier after infection with a PT-deficient strain than with a wildtype strain [14,33,34]. PT also reduced the ability of anti-B. pertussis antibodies to clear infection, an inhibitory effect that was lost after neutrophil depletion [34]. However, in our studies, neutrophil depletion only enhanced B. pertussis infection in immune (i.e. previously infected) mice, and not in naı¨ve mice (Andreasen C et al., unpublished), suggesting that PT might play an alternative role in a naı¨ve individual. Recently, we have found that depletion of airway macrophages by intranasal administration of clodronate liposomes [35] not only enhances infection by wild-type B. pertussis, but also by the PT-deficient strain (up to the level of infection seen with wild-type) [36], suggesting that resident airway macrophages may be the primary target cells for PT in its ability to promote infection. Interestingly, ADP ribosylation of airway macrophage G proteins after intranasal treatment of mice with PT lasted longer than two weeks (correlating with the longevity of its infection-promoting activity [33]), suggesting that the effects of PT on host cells in the airways may be particularly long-lived. Furthermore, PT exerts multiple suppressive effects on the immune system beyond those observed on innate immune cells; for example, other studies have shown PTmediated suppression of serum antibody responses to B. pertussis antigens after infection [37,38], reduction of major histocompatibility complex class II molecules on the surface of human monocytes [39], and modulation of surface markers on DCs [40]. Therefore, PT might promote B. pertussis infection by multiple mechanisms: through effects on innate immunity in the initial stages in a naı¨ve individual; by reducing adaptive immune responses generated by the infection; and by promoting re-infection in a partially immune individual.
Immunomodulation through TLR4 signaling Recent studies have revealed that much of the immune response to B. pertussis is initiated and controlled through Toll-like receptor (TLR)-4 signaling. TLR4, one of the TLRs on mammalian cells that recognize conserved microbial molecules and allow the innate immune system to respond to infection [41], is involved in recognition of LPS from many Gram-negative bacteria, including that of B. pertussis [42,43]. These investigators found that B. pertussis infection was more severe in TLR4-defective mice [42,43] and that TLR4 signaling induced IL-10 production in response to B. pertussis infection, which could inhibit inflammatory responses and limit pathology in the airways [42]. The same group showed that LPS could also act synergistically with ACT to induce IL-10 production and modulate other responses by DCs [16]. A similar protective effect of TLR4 signaling was observed in response to B. bronchiseptica infection of mice. TLR4defective mice had a significantly greater bacterial load in the respiratory tract, suffered severe airway pathology and www.sciencedirect.com
Immunomodulation in the pathogenesis of Bordetella pertussis infection and disease Carbonetti 275
rapidly succumbed to B. bronchiseptica infection [44], which might all result from a lack of early tumour necrosis factor-a production in these mice [45]. However, the same group also showed that a different pattern of TLR4-dependent responses is induced by B. pertussis infection, with lower levels of inflammatory cytokines produced and no apparent protective role for tumour necrosis factor-a, perhaps owing to the less endotoxic nature of B. pertussis LPS compared with that of B. bronchiseptica and/or to PT production by, or the lack of TTSS expression in, B. pertussis [46]. In adaptation of B. pertussis to the human host, reduced TLR4 signaling might therefore benefit both host and pathogen by limiting immune clearance mechanisms as well as immune-mediated pathology. Furthermore, TLR4 signaling was recently found to be necessary for pertussis vaccine-induced protective immunity in the mouse aerosol inoculation model [47], potentially through induction of IL-17-producing T cells, a phenomenon discussed in further detail below.
Immunomodulation towards a Th17 response An intriguing recent finding from studies investigating immunomodulation by B. pertussis is that the host immune response might be skewed towards expansion of a novel subset of T lymphocytes termed Th17 cells, which are induced by production of the cytokine IL-23 [48]. Several earlier studies had indicated that B. pertussis infection promotes a Th1 immune response, based largely on interferon-g production [4,49]. However, in a recent study, incubation of human DCs with B. pertussis induced expression of IL-23, but not that of the Th1-inducing cytokine IL-12 [50]. The same group then showed that induction of IL-23 and inhibition of IL-12 was caused by the enzymatic action of ACT raising cAMP levels, as the reverse pattern of expression was observed in DCs incubated with an ACT-deficient mutant of B. pertussis; in this case, addition of cAMP restored IL-23 production [51]. Furthermore, B. bronchiseptica-infected murine macrophages induced IL-17 production by T cells in vitro and a strong IL-17 response by re-stimulated lung tissue from B. bronchiseptica-infected mice was detected, whereas interferon-g production was negligible in comparison [52]. Pertussis vaccination of mice also induced a Th17 response, dependent upon TLR4 signaling and IL-1, that contributed to protection against B. pertussis challenge, possibly via IL-17 enhancement of macrophage killing [47]. Collectively, these data suggest that Bordetella infection may induce a Th17-polarized immune response, which can subsequently be protective against certain infections, including other Gram-negative bacterial respiratory pathogens [53], but which has also been associated with chronic autoimmune inflammation [54]. Therefore, we speculate that the major pathology associated with B. pertussis infection — the cough — may be caused by a chronic autoimmune reaction in the airways as a result of this skewed immune response towards a Th17 profile. www.sciencedirect.com
Pertussis impact on other airway pathologies: a link with asthma? Given the immunomodulatory effects of various B. pertussis virulence factors, the question arises as to whether B. pertussis infection could modulate other airway pathologies. An interesting recent study demonstrated that B. pertussis infection exacerbated airway symptoms in a mouse model of allergic asthma [55]. Contrary to the hypothesis of the investigators (that the Th1 response induced by B. pertussis infection would protect against allergic asthma, a known Th2-promoted pathology), they found that B. pertussis infection, before sensitization with antigen (ovalbumin), resulted in both increased bronchial hyperreactivity (to methacholine) and exacerbated airway pathology (i.e. inflammation, epithelial hyperplasia and mucous metaplasia) compared with that seen in mice treated with ovalbumin alone. This occurred despite an increase in levels of the regulatory cytokine IL-10. A recent survey of adult asthmatics found evidence of B. pertussis infection (as measured by PCR from sputum samples) in almost 30% of mild, and 20% of moderate, asthmatics (versus 16% of healthy control subjects); B. pertussis-positive subjects also had lower forced expiratory volumes and more symptoms of asthma than did B. pertussis-negative individuals [56]. Furthermore, in accordance with the role that IL-17 plays in murine asthma models [57], IL-17 mRNA levels were found to be elevated in sputum samples from human asthmatic patients, along with higher neutrophil counts [58]. Therefore, B. pertussis infection, possibly through induction of a Th17 response, might impinge adversely on other airway pathologies.
Conclusions Protective immunity to B. pertussis is complex and involves a diversity of immune cells and responses [4]. The current literature supports the idea that B. pertussis virulence factors collectively promote infection caused by this pathogen through modulation and suppression of the host immune response. Could this immunomodulation, through induction of a Th17 response and the chronic autoimmune inflammation that might occur in the airways as a result, also be responsible for the cough pathology of pertussis? Currently, this is mere speculation, as there is no direct evidence for the cause of the cough. Another hypothesis is that PT contributes to the cough pathology indirectly through long-lived effects on airway muscle and nerve cells that produce the cough response. Several receptors on neurons that control airway responses signal through PT-sensitive G proteins [59], and recent studies have shown that PT is able to affect airway muscle and nerve cells [60–63]. Therefore, if G protein modification by PT in these cells is long-lived, these PT modulatory effects could account for the paroxysmal nature of coughing and the long-lived hyperreactivity of the airways in pertussis disease. If these speculations are borne out by further studies, treatments to reduce airway pathology will need to be aimed at reducing the harmful effects of Current Opinion in Pharmacology 2007, 7:272–278
276 Respiratory
IL-17 and the Th17-mediated autoimmune response, or at increasing G protein turnover in affected cells to remove the inhibitory effects of PT, treatments that are far from reaching development. Certainly, conventional anti-tussive medications have no benefit for pertussis patients [64], and so, in addition to novel ideas on pertussis vaccine development [65], new thinking and approaches are surely necessary for the development of effective therapies for this disease.
Acknowledgements I would like to thank Dr Ina Stephens for helpful discussions on pertussis disease and contributions towards this review, and Dr Brendan Canning for guidance in preparation of the review. Work in the author’s laboratory was funded by National Institutes of Health grants AI063080, AI060863 and AI050022.
References and recommended reading Papers of particular interest, published within the period of review, have been highlighted as: of special interest of outstanding interest 1.
cyclase toxin synergize in promoting lysis of monocytes. Infect Immun 2006, 74:2207-2214. 13. Mobberley-Schuman PS, Weiss AA: Influence of CR3 (CD11b/ CD18) expression on phagocytosis of Bordetella pertussis by human neutrophils. Infect Immun 2005, 73:7317-7323. 14. Carbonetti NH, Artamonova GV, Andreasen C, Bushar N: Pertussis toxin and adenylate cyclase toxin provide a one-two punch for establishment of Bordetella pertussis infection of the respiratory tract. Infect Immun 2005, 73:2698-2703. In this study, we show that PT plays an earlier role than ACT in promoting airway infection in the mouse model, possibly by inhibiting early neutrophil influx into the airways. 15. Bagley KC, Abdelwahab SF, Tuskan RG, Fouts TR, Lewis GK: Pertussis toxin and the adenylate cyclase toxin from Bordetella pertussis activate human monocyte-derived dendritic cells and dominantly inhibit cytokine production through a cAMP-dependent pathway. J Leukoc Biol 2002, 72:962-969. 16. Ross PJ, Lavelle EC, Mills KH, Boyd AP: Adenylate cyclase toxin from Bordetella pertussis synergizes with lipopolysaccharide to promote innate interleukin-10 production and enhances the induction of Th2 and regulatory T cells. Infect Immun 2004, 72:1568-1579. 17. Skinner JA, Reissinger A, Shen H, Yuk MH: Bordetella type III secretion and adenylate cyclase toxin synergize to drive dendritic cells into a semimature state. J Immunol 2004, 173:1934-1940.
Mattoo S, Cherry JD: Molecular pathogenesis, epidemiology, and clinical manifestations of respiratory infections due to Bordetella pertussis and other Bordetella subspecies. Clin Microbiol Rev 2005, 18:326-382. Comprehensive review of all aspects of B. pertussis biology, infection and disease.
18. Boyd AP, Ross PJ, Conroy H, Mahon N, Lavelle EC, Mills KH: Bordetella pertussis adenylate cyclase toxin modulates innate and adaptive immune responses: distinct roles for acylation and enzymatic activity in immunomodulation and cell death. J Immunol 2005, 175:730-738.
2.
Crowcroft NS, Pebody RG: Recent developments in pertussis. Lancet 2006, 367:1926-1936.
19. Flak TA, Heiss LN, Engle JT, Goldman WE: Synergistic epithelial responses to endotoxin and a naturally occurring muramyl peptide. Infect Immun 2000, 68:1235-1242.
3.
Preston A: Bordetella pertussis: the intersection of genomics and pathobiology. CMAJ 2005, 173:55-62.
4.
Mills KH: Immunity to Bordetella pertussis. Microbes Infect 2001, 3:655-677.
5.
Finlay BB, McFadden G: Anti-immunology: evasion of the host immune system by bacterial and viral pathogens. Cell 2006, 124:767-782.
6.
Edwards JA, Groathouse NA, Boitano S: Bordetella bronchiseptica adherence to cilia is mediated by multiple adhesin factors and blocked by surfactant protein A. Infect Immun 2005, 73:3618-3626.
7.
Perez Vidakovics ML, Lamberti Y, van der Pol WL, Yantorno O, Rodriguez ME: Adenylate cyclase influences filamentous haemagglutinin-mediated attachment of Bordetella pertussis to epithelial alveolar cells. FEMS Immunol Med Microbiol 2006, 48:140-147.
8.
Zaretzky FR, Gray MC, Hewlett EL: Mechanism of association of adenylate cyclase toxin with the surface of Bordetella pertussis: a role for toxin-filamentous haemagglutinin interaction. Mol Microbiol 2002, 45:1589-1598.
9.
McGuirk P, McCann C, Mills KH: Pathogen-specific T regulatory 1 cells induced in the respiratory tract by a bacterial molecule that stimulates interleukin 10 production by dendritic cells: a novel strategy for evasion of protective T helper type 1 responses by Bordetella pertussis. J Exp Med 2002, 195:221-231.
10. Mobberley-Schuman PS, Connelly B, Weiss AA: Phagocytosis of Bordetella pertussis incubated with convalescent serum. J Infect Dis 2003, 187:1646-1653.
20. Cundell DR, Kanthakumar K, Taylor GW, Goldman WE, Flak T, Cole PJ, Wilson R: Effect of tracheal cytotoxin from Bordetella pertussis on human neutrophil function in vitro. Infect Immun 1994, 62:639-643. 21. Magalhaes JG, Philpott DJ, Nahori MA, Jehanno M, Fritz J, Bourhis LL, Viala J, Hugot JP, Giovannini M, Bertin J et al.: Murine Nod1 but not its human orthologue mediates innate immune detection of tracheal cytotoxin. EMBO Rep 2005, 6:1201-1207. 22. Swaminathan CP, Brown PH, Roychowdhury A, Wang Q, Guan R, Silverman N, Goldman WE, Boons GJ, Mariuzza RA: Dual strategies for peptidoglycan discrimination by peptidoglycan recognition proteins (PGRPs). Proc Natl Acad Sci USA 2006, 103:684-689. 23. Chang CI, Chelliah Y, Borek D, Mengin-Lecreulx D, Deisenhofer J: Structure of tracheal cytotoxin in complex with a heterodimeric pattern-recognition receptor. Science 2006, 311:1761-1764. 24. Kaneko T, Yano T, Aggarwal K, Lim JH, Ueda K, Oshima Y, Peach C, Erturk-Hasdemir D, Goldman WE, Oh BH et al.: PGRPLC and PGRP-LE have essential yet distinct functions in the drosophila immune response to monomeric DAP-type peptidoglycan. Nat Immunol 2006, 7:715-723. This study demonstrates that TCT binds to peptidoglycan-recognition proteins and potently stimulates an immune response signaling pathway. 25. Yuk MH, Harvill ET, Cotter PA, Miller JF: Modulation of host immune responses, induction of apoptosis and inhibition of NF-kappaB activation by the Bordetella type III secretion system. Mol Microbiol 2000, 35:991-1004.
11. Vojtova J, Kamanova J, Sebo P: Bordetella adenylate cyclase toxin: a swift saboteur of host defense. Curr Opin Microbiol 2006, 9:69-75. Excellent recent review of ACT, including its immunomodulatory effects.
26. Kuwae A, Matsuzawa T, Ishikawa N, Abe H, Nonaka T, Fukuda H, Imajoh-Ohmi S, Abe A: BopC is a novel type III effector secreted by Bordetella bronchiseptica and has a critical role in type III-dependent necrotic cell death. J Biol Chem 2006, 281:6589-6600.
12. Basler M, Masin J, Osicka R, Sebo P: Pore-forming and enzymatic activities of Bordetella pertussis adenylate
27. Skinner JA, Pilione MR, Shen H, Harvill ET, Yuk MH: Bordetella type III secretion modulates dendritic cell migration resulting
Current Opinion in Pharmacology 2007, 7:272–278
www.sciencedirect.com
Immunomodulation in the pathogenesis of Bordetella pertussis infection and disease Carbonetti 277
in immunosuppression and bacterial persistence. J Immunol 2005, 175:4647-4652. 28. Reissinger A, Skinner JA, Yuk MH: Downregulation of mitogenactivated protein kinases by the Bordetella bronchiseptica type III secretion system leads to attenuated nonclassical macrophage activation. Infect Immun 2005, 73:308-316. 29. Pilione MR, Harvill ET: The Bordetella bronchiseptica type III secretion system inhibits gamma interferon production that is required for efficient antibody-mediated bacterial clearance. Infect Immun 2006, 74:1043-1049. 30. Legarda D, Klein-Patel ME, Yim S, Yuk MH, Diamond G: Suppression of NF-kappaB-mediated beta-defensin gene expression in the mammalian airway by the Bordetella type III secretion system. Cell Microbiol 2005, 7:489-497. 31. Reisine T: Pertussis toxin in the analysis of receptor mechanisms. Biochem Pharmacol 1990, 39:1499-1504. 32. Munoz JJ, Arai H, Bergman RK, Sadowski PL: Biological activities of crystalline pertussigen from Bordetella pertussis. Infect Immun 1981, 33:820-826. 33. Carbonetti NH, Artamonova GV, Mays RM, Worthington ZE: Pertussis toxin plays an early role in respiratory tract colonization by Bordetella pertussis. Infect Immun 2003, 71:6358-6366. 34. Kirimanjeswara GS, Agosto LM, Kennett MJ, Bjornstad ON, Harvill ET: Pertussis toxin inhibits neutrophil recruitment to delay antibody-mediated clearance of Bordetella pertussis. J Clin Invest 2005, 115:3594-3601. In this study, PT is shown to inhibit antibody-mediated clearance of B. pertussis from the lower respiratory tract through a mechanism involving the inhibition of neutrophil recruitment to the airways. 35. Van Rooijen N, Sanders A: Liposome mediated depletion of macrophages: mechanism of action, preparation of liposomes and applications. J Immunol Methods 1994, 174:83-93. 36. Carbonetti NH, Artamonova GV, van Rooijen N, Ayala VI: Pertussis toxin targets airway macrophages to promote Bordetella pertussis infection of the respiratory tract. Infect Immun 2007, 75, in press. This report demonstrates that a primary role for PT in promoting early B. pertussis infection is to combat the protective activities of resident airway macrophages, and that PT modification of airway macrophage G proteins is a long-lived effect. 37. Mielcarek N, Riveau G, Remoue F, Antoine R, Capron A, Locht C: Homologous and heterologous protection after single intranasal administration of live attenuated recombinant Bordetella pertussis. Nat Biotechnol 1998, 16:454-457. 38. Carbonetti NH, Artamonova GV, Andreasen C, Dudley E, Mays RM, Worthington ZE: Suppression of serum antibody responses by pertussis toxin after respiratory tract colonization by Bordetella pertussis and identification of an immunodominant lipoprotein. Infect Immun 2004, 72:3350-3358. 39. Shumilla JA, Lacaille V, Hornell TM, Huang J, Narasimhan S, Relman DA, Mellins ED: Bordetella pertussis infection of primary human monocytes alters HLA-DR expression. Infect Immun 2004, 72:1450-1462. 40. Martino A, Volpe E, Auricchio G, Colizzi V, Baldini PM: Influence of pertussis toxin on CD1a isoform expression in human dendritic cells. J Clin Immunol 2006, 26:153-159. 41. Akira S: TLR signaling. Curr Top Microbiol Immunol 2006, 311:1-16. 42. Higgins SC, Lavelle EC, McCann C, Keogh B, McNeela E, Byrne P, O’Gorman B, Jarnicki A, McGuirk P, Mills KH: Toll-like receptor 4-mediated innate IL-10 activates antigen-specific regulatory T cells and confers resistance to Bordetella pertussis by inhibiting inflammatory pathology. J Immunol 2003, 171:3119-3127. 43. Banus HA, Vandebriel RJ, de Ruiter H, Dormans JA, Nagelkerke NJ, Mooi FR, Hoebee B, van Kranen HJ, Kimman TG: Host genetics of Bordetella pertussis infection in mice: www.sciencedirect.com
significance of Toll-like receptor 4 in genetic susceptibility and pathobiology. Infect Immun 2006, 74:2596-2605. 44. Mann PB, Kennett MJ, Harvill ET: Toll-like receptor 4 is critical to innate host defense in a murine model of bordetellosis. J Infect Dis 2004, 189:833-836. 45. Mann PB, Elder KD, Kennett MJ, Harvill ET: Toll-like receptor 4-dependent early elicited tumor necrosis factor alpha expression is critical for innate host defense against Bordetella bronchiseptica. Infect Immun 2004, 72:6650-6658. 46. Mann PB, Wolfe D, Latz E, Golenbock D, Preston A, Harvill ET: Comparative toll-like receptor 4-mediated innate host defense to Bordetella infection. Infect Immun 2005, 73:8144-8152. This study shows that B. pertussis LPS signals through TLR4 to elicit milder responses than those elicited by B. bronchiseptica LPS, contributing to different outcomes in these two infections. 47. Higgins SC, Jarnicki AG, Lavelle EC, Mills KH: TLR4 mediates vaccine-induced protective cellular immunity to bordetella pertussis: role of il-17-producing T cells. J Immunol 2006, 177:7980-7989. This study demonstrates the importance of TLR4 signaling and IL-17 production to pertussis vaccine-mediated protective cellular immunity to B. pertussis infection, including a possible role for IL-17 in the activation of macrophage killing of B. pertussis. 48. Harrington LE, Mangan PR, Weaver CT: Expanding the effector CD4 T-cell repertoire: the Th17 lineage. Curr Opin Immunol 2006, 18:349-356. 49. Mascart F, Verscheure V, Malfroot A, Hainaut M, Pierard D, Temerman S, Peltier A, Debrie AS, Levy J, Del Giudice G, Locht C: Bordetella pertussis infection in 2-month-old infants promotes type 1 T cell responses. J Immunol 2003, 170:1504-1509. 50. Fedele G, Stefanelli P, Spensieri F, Fazio C, Mastrantonio P, Ausiello CM: Bordetella pertussis-infected human monocytederived dendritic cells undergo maturation and induce Th1 polarization and interleukin-23 expression. Infect Immun 2005, 73:1590-1597. 51. Spensieri F, Fedele G, Fazio C, Nasso M, Stefanelli P, Mastrantonio P, Ausiello CM: Bordetella pertussis inhibition of interleukin-12 (IL-12) p70 in human monocyte-derived dendritic cells blocks IL-12 p35 through adenylate cyclase toxin-dependent cyclic AMP induction. Infect Immun 2006, 74:2831-2838. Here, the authors show that ACT can inhibit IL-12 while inducing IL-23 production from DCs exposed to B. pertussis. 52. Siciliano NA, Skinner JA, Yuk MH: Bordetella bronchiseptica modulates macrophage phenotype leading to the inhibition of CD4+ T cell proliferation and the initiation of a Th17 immune response. J Immunol 2006, 177:7131-7138. These authors demonstrate that B. bronchiseptica, through ACT and TTSS activities, modulates macrophages to produce prostaglandin, which inhibits antigen-driven T cell proliferation, and to induce a Th17 phenotype in response to infection. 53. Happel KI, Dubin PJ, Zheng M, Ghilardi N, Lockhart C, Quinton LJ, Odden AR, Shellito JE, Bagby GJ, Nelson S, Kolls JK: Divergent roles of IL-23 and IL-12 in host defense against Klebsiella pneumoniae. J Exp Med 2005, 202:761-769. 54. Langrish CL, Chen Y, Blumenschein WM, Mattson J, Basham B, Sedgwick JD, McClanahan T, Kastelein RA, Cua DJ: IL-23 drives a pathogenic T cell population that induces autoimmune inflammation. J Exp Med 2005, 201:233-240. 55. Ennis DP, Cassidy JP, Mahon BP: Prior Bordetella pertussis infection modulates allergen priming and the severity of airway pathology in a murine model of allergic asthma. Clin Exp Allergy 2004, 34:1488-1497. 56. Harju TH, Leinonen M, Nokso-Koivisto J, Korhonen T, Raty R, He Q, Hovi T, Mertsola J, Bloigu A, Rytila P, Saikku P: Pathogenic bacteria and viruses in induced sputum or pharyngeal secretions of adults with stable asthma. Thorax 2006, 61:579-584. 57. Hellings PW, Kasran A, Liu Z, Vandekerckhove P, Wuyts A, Overbergh L, Mathieu C, Ceuppens JL: Interleukin-17 Current Opinion in Pharmacology 2007, 7:272–278
278 Respiratory
orchestrates the granulocyte influx into airways after allergen challenge inhalation in a mouse model of allergic asthma. Am J Respir Cell Mol Biol 2003, 28:42-50. 58. Bullens DM, Truyen E, Coteur L, Dilissen E, Hellings PW, Dupont LJ, Ceuppens JL: IL-17 mRNA in sputum of asthmatic patients: linking T cell driven inflammation and granulocytic influx? Respir Res 2006, 7:135. 59. Mazzone SB, Canning BJ: Central nervous system control of the airways: pharmacological implications. Curr Opin Pharmacol 2002, 2:220-228. 60. Yoshihara S, Morimoto H, Ohori M, Yamada Y, Abe T, Arisaka O: A neuroactive steroid inhibits guinea pig airway sensory nerves via Maxi-K channel activation. Int Arch Allergy Immunol 2006, 141:31-36. 61. Rong Zhou J, Shirasaki T, Soeda F, Takahama K: Potentiation of nicotinic currents by bradykinin in the paratracheal ganglia neurons of rats. Eur J Pharmacol 2006, 531:96-102.
Current Opinion in Pharmacology 2007, 7:272–278
62. Osawa Y, Xu D, Sternberg D, Sonett JR, D’Armiento J, Panettieri RA, Emala CW: Functional expression of the GABAB receptor in human airway smooth muscle. Am J Physiol Lung Cell Mol Physiol 2006, 291:L923-L931. 63. Ethier MF, Madison JM: Adenosine A1 receptors mediate mobilization of calcium in human bronchial smooth muscle cells. Am J Respir Cell Mol Biol 2006, 35:496-502. 64. Pillay V, Swingler G: Symptomatic treatment of the cough in whooping cough. Cochrane Database Syst Rev 2003, issue 4:CD003257. 65. Mielcarek N, Debrie AS, Raze D, Bertout J, Rouanet C, Younes AB, Creusy C, Engle J, Goldman WE, Locht C: Live attenuated B. pertussis as a single-dose nasal vaccine against whooping cough. PLoS Pathog 2006, 2:e65. The authors describe an attenuated B. pertussis strain (deficient in PT and TCT production) that induces strong protective immunity after intranasal infection of mice as a potential novel vaccine approach for pertussis.
www.sciencedirect.com
Current Opinion in Pharmacology 2007, 7:272–278 This review comes from a themed issue on Respiratory pharmacology Edited by Brendan Canning and Stephen Farmer Available online 5th April 2007 1471-4892/$ – see front matter # 2006 Elsevier Ltd. All rights reserved. DOI 10.1016/j.coph.2006.12.004
Introduction Bordetella pertussis is a Gram-negative bacterial pathogen that infects the human respiratory tract and causes the disease pertussis (or whooping cough). A comprehensive review on B. pertussis [1] and other useful reviews on the organism and disease have been published recently [2,3]. Although pertussis was traditionally considered a childhood disease, recent surveys and investigations have revealed that large numbers of older children, adolescents and adults are also infected and suffer from cough disease, causing serious public health issues. The classical disease symptom is a paroxysmal cough with whooping and vomiting, which is most frequently observed in unvaccinated infants. Whooping is less common in older individuals, in which the severity of cough varies widely. Apnea is another frequent problem of the disease in infants, and other Current Opinion in Pharmacology 2007, 7:272–278
complications include pneumonia, hypoxia, seizures, encephalopathy and secondary respiratory infections. Another hallmark of pertussis cough disease is its longevity, typically lasting several weeks (the Chinese term for pertussis is ‘the cough of a hundred days’) with gradually decreasing frequency and severity. The pathology of the airways in non-fatal cases is poorly characterized, although mucus hypersecretion is common. Pathological findings from postmortem observations, experimental animal infections and organ culture experiments include epithelial and ciliary damage, bronchopneumonia, pulmonary edema and focal hemorrhage. What causes the cough pathology of pertussis? In truth, we have little or no evidence to answer this question. Furthermore, despite detailed molecular knowledge of several virulence-associated factors of B. pertussis, there remain significant gaps in our understanding of the pathogenesis of this infection and disease. Contributing to this problem is the lack of either experimental human challenge studies or small animal models of the cough disease after B. pertussis infection. The most frequently used animal model for this infection is the mouse intranasal or aerosol inoculation model. Although overt symptomatic disease is not observed (mice cannot cough), several characteristics of the human infection are reproduced in this model, including multiplication and clearance of bacteria, limitation of infection to the respiratory tract, increased severity of infection in young animals, and various systemic physiological and neurological changes; the model can also be useful for the preclinical assessment of acellular pertussis vaccine efficacy [4]. This model has been particularly informative on the nature of protective immune responses elicited by B. pertussis infection and pertussis vaccination [4], and the availability of immunodeficient mice, developed either by genetic mutation or by chemical treatment, has facilitated further understanding of the interplay between the bacterial pathogen and host immunity. This review focuses on the pathogenesis of B. pertussis infection, with a particular emphasis on the immune suppression, evasion and subversion mechanisms employed by this pathogen, as revealed by recent literature. It appears that much of the activity of B. pertussis virulence factors is dedicated to this ‘anti-immunology’ aspect of pathogenesis, in common with other bacterial and viral pathogens as outlined in a recent review [5]. In addition, there is speculation that these immunomodulatory virulence mechanisms may not only aid B. pertussis infection www.sciencedirect.com
Immunomodulation in the pathogenesis of Bordetella pertussis infection and disease Carbonetti 273
Figure 1
Summary of infection of the respiratory tract by B. pertussis and its immunomodulatory effects.
but might also be crucially involved in pertussis disease pathogenesis.
B. pertussis virulence factors and immunomodulation This section provides a brief overview of several B. pertussis virulence factors, along with some of their immunomodulatory properties (Figure 1). Filamentous hemagglutinin (FHA) is considered to be the major surface structure mediating adherence to host cells, primarily to cilia on the airway ciliated epithelium. However, a recent study of the adherence of B. bronchiseptica (the closely related animal pathogen) to rabbit tracheal epithelial tissue, which measured real-time bacterial binding to cilia over the first four minutes after exposure, showed that loss of any one of several surface or secreted factors resulted in only partial loss of adherence, suggesting that multiple factors might contribute to the binding process [6]. This binding might be indirectly controlled through FHA, however, as another study suggested that secreted adenylate cyclase toxin (ACT) modifies a heparin-inhibitable carbohydrate binding domain of FHA to enhance www.sciencedirect.com
its ability to mediate adherence to cultured lung epithelial cells [7], presumably through a direct interaction between the two factors (previously described in [8]). In addition to its role in adherence, FHA has previously been shown to have immunosuppressive and immunomodulatory activities. B. pertussis infection of mice generated FHA-specific T regulatory lymphocytes that secreted interleukin (IL)-10 and suppressed protective T helper lymphocyte type I (Th1) responses against the pathogen [9]. In addition, antibodies to FHA in convalescent human serum were found to reduce the phagocytosis of B. pertussis by human neutrophils [10]. ACT is a secreted toxin that targets host phagocytic cells by binding complement receptor 3 (CR3; CD11b/CD18), forming membrane pores and raising intracellular cAMP levels through its adenylate cyclase domain [11,12]. ACTdeficient mutants of B. pertussis were more efficiently phagocytosed by human neutrophils [13] and achieved lower bacterial loads in the respiratory tract of a mouse intranasal infection model than did a wild-type strain [14]. Recent findings have shown that ACT can upregulate major histocompatibility complex class II and Current Opinion in Pharmacology 2007, 7:272–278
274 Respiratory
costimulatory molecules on dendritic cells (DCs), inducing a semi-mature state that decreases proinflammatory cytokine production [15–17]. Interestingly, these effects were caused by the adenylate cyclase activity of the toxin, whereas cytotoxic effects of ACT were also associated with its pore-forming activity [12,15,18]. Tracheal cytotoxin (TCT) is a disaccharide-tetrapeptide fragment of peptidoglycan released by B. pertussis at relatively high levels. Purified TCT, in synergy with lipopolysaccharide (LPS), damages ciliated airway epithelial cells through production of IL-1a and nitric oxide [19] and has deleterious effects on neutrophils [20]. Recent studies have shown that TCT stimulates responses in immune cells through microbial pattern-recognition molecules that interact with peptidoglycan and its derivatives. In mice, these responses were dependent upon the intracellular receptor Nod1; however, human Nod1 detected TCT poorly [21]. Instead, TCT binds human and Drosophila peptidoglycan recognition proteins, which (at least in Drosophila cells) potently activates an immune response pathway [22,23,24]. Therefore, TCT might also contribute to overall immunomodulation during B. pertussis infection. B. bronchiseptica expresses a type III secretion system (TTSS) that directly injects effector proteins (which are toxic for macrophage and epithelial cells in culture) into host cells, and that contributes to persistent respiratory infection in animal models [25,26]. The TTSS also possesses several immunosuppressive properties, resulting in modulation of DC maturation (in synergy with ACT) and migration to lymph nodes [17,27], macrophage activation [28], interferon-g production [27,29] and airway b-defensin production [30]. However, whether this is relevant to B. pertussis infection is unknown, as it is unclear whether B. pertussis expresses a TTSS.
Immunosuppression by pertussis toxin Pertussis toxin (PT) is another secreted toxin uniquely produced by B. pertussis which ADP-ribosylates several heterotrimeric G proteins in mammalian cells, disrupting signaling pathways with a wide range of downstream effects [31]. PT is perhaps the most enigmatic virulence factor of B. pertussis: although considered to be crucial for virulence, its role in promoting respiratory infection and disease has remained elusive. PT has long been known to cause systemic symptoms associated with pertussis disease, such as lymphocytosis, insulinemia/hypoglycemia and histamine sensitivity [32], but it was unclear from previous studies whether PT contributed to local events of respiratory infection and disease. However, recent studies using the mouse intranasal infection model indicate that PT is important in the very early stages after inoculation of bacteria. PT-deficient mutant strains showed reduced levels of airway infection 24 h postinoculation and, whereas co-administration of purified PT enhanced infection by the mutant strain, PT administration 24 h after inoculation had no enhancing effect [33]. One possible mechanism of action for PT is the Current Opinion in Pharmacology 2007, 7:272–278
delay of neutrophil recruitment and influx to the airways, as two groups have found that this response occurs earlier after infection with a PT-deficient strain than with a wildtype strain [14,33,34]. PT also reduced the ability of anti-B. pertussis antibodies to clear infection, an inhibitory effect that was lost after neutrophil depletion [34]. However, in our studies, neutrophil depletion only enhanced B. pertussis infection in immune (i.e. previously infected) mice, and not in naı¨ve mice (Andreasen C et al., unpublished), suggesting that PT might play an alternative role in a naı¨ve individual. Recently, we have found that depletion of airway macrophages by intranasal administration of clodronate liposomes [35] not only enhances infection by wild-type B. pertussis, but also by the PT-deficient strain (up to the level of infection seen with wild-type) [36], suggesting that resident airway macrophages may be the primary target cells for PT in its ability to promote infection. Interestingly, ADP ribosylation of airway macrophage G proteins after intranasal treatment of mice with PT lasted longer than two weeks (correlating with the longevity of its infection-promoting activity [33]), suggesting that the effects of PT on host cells in the airways may be particularly long-lived. Furthermore, PT exerts multiple suppressive effects on the immune system beyond those observed on innate immune cells; for example, other studies have shown PTmediated suppression of serum antibody responses to B. pertussis antigens after infection [37,38], reduction of major histocompatibility complex class II molecules on the surface of human monocytes [39], and modulation of surface markers on DCs [40]. Therefore, PT might promote B. pertussis infection by multiple mechanisms: through effects on innate immunity in the initial stages in a naı¨ve individual; by reducing adaptive immune responses generated by the infection; and by promoting re-infection in a partially immune individual.
Immunomodulation through TLR4 signaling Recent studies have revealed that much of the immune response to B. pertussis is initiated and controlled through Toll-like receptor (TLR)-4 signaling. TLR4, one of the TLRs on mammalian cells that recognize conserved microbial molecules and allow the innate immune system to respond to infection [41], is involved in recognition of LPS from many Gram-negative bacteria, including that of B. pertussis [42,43]. These investigators found that B. pertussis infection was more severe in TLR4-defective mice [42,43] and that TLR4 signaling induced IL-10 production in response to B. pertussis infection, which could inhibit inflammatory responses and limit pathology in the airways [42]. The same group showed that LPS could also act synergistically with ACT to induce IL-10 production and modulate other responses by DCs [16]. A similar protective effect of TLR4 signaling was observed in response to B. bronchiseptica infection of mice. TLR4defective mice had a significantly greater bacterial load in the respiratory tract, suffered severe airway pathology and www.sciencedirect.com
Immunomodulation in the pathogenesis of Bordetella pertussis infection and disease Carbonetti 275
rapidly succumbed to B. bronchiseptica infection [44], which might all result from a lack of early tumour necrosis factor-a production in these mice [45]. However, the same group also showed that a different pattern of TLR4-dependent responses is induced by B. pertussis infection, with lower levels of inflammatory cytokines produced and no apparent protective role for tumour necrosis factor-a, perhaps owing to the less endotoxic nature of B. pertussis LPS compared with that of B. bronchiseptica and/or to PT production by, or the lack of TTSS expression in, B. pertussis [46]. In adaptation of B. pertussis to the human host, reduced TLR4 signaling might therefore benefit both host and pathogen by limiting immune clearance mechanisms as well as immune-mediated pathology. Furthermore, TLR4 signaling was recently found to be necessary for pertussis vaccine-induced protective immunity in the mouse aerosol inoculation model [47], potentially through induction of IL-17-producing T cells, a phenomenon discussed in further detail below.
Immunomodulation towards a Th17 response An intriguing recent finding from studies investigating immunomodulation by B. pertussis is that the host immune response might be skewed towards expansion of a novel subset of T lymphocytes termed Th17 cells, which are induced by production of the cytokine IL-23 [48]. Several earlier studies had indicated that B. pertussis infection promotes a Th1 immune response, based largely on interferon-g production [4,49]. However, in a recent study, incubation of human DCs with B. pertussis induced expression of IL-23, but not that of the Th1-inducing cytokine IL-12 [50]. The same group then showed that induction of IL-23 and inhibition of IL-12 was caused by the enzymatic action of ACT raising cAMP levels, as the reverse pattern of expression was observed in DCs incubated with an ACT-deficient mutant of B. pertussis; in this case, addition of cAMP restored IL-23 production [51]. Furthermore, B. bronchiseptica-infected murine macrophages induced IL-17 production by T cells in vitro and a strong IL-17 response by re-stimulated lung tissue from B. bronchiseptica-infected mice was detected, whereas interferon-g production was negligible in comparison [52]. Pertussis vaccination of mice also induced a Th17 response, dependent upon TLR4 signaling and IL-1, that contributed to protection against B. pertussis challenge, possibly via IL-17 enhancement of macrophage killing [47]. Collectively, these data suggest that Bordetella infection may induce a Th17-polarized immune response, which can subsequently be protective against certain infections, including other Gram-negative bacterial respiratory pathogens [53], but which has also been associated with chronic autoimmune inflammation [54]. Therefore, we speculate that the major pathology associated with B. pertussis infection — the cough — may be caused by a chronic autoimmune reaction in the airways as a result of this skewed immune response towards a Th17 profile. www.sciencedirect.com
Pertussis impact on other airway pathologies: a link with asthma? Given the immunomodulatory effects of various B. pertussis virulence factors, the question arises as to whether B. pertussis infection could modulate other airway pathologies. An interesting recent study demonstrated that B. pertussis infection exacerbated airway symptoms in a mouse model of allergic asthma [55]. Contrary to the hypothesis of the investigators (that the Th1 response induced by B. pertussis infection would protect against allergic asthma, a known Th2-promoted pathology), they found that B. pertussis infection, before sensitization with antigen (ovalbumin), resulted in both increased bronchial hyperreactivity (to methacholine) and exacerbated airway pathology (i.e. inflammation, epithelial hyperplasia and mucous metaplasia) compared with that seen in mice treated with ovalbumin alone. This occurred despite an increase in levels of the regulatory cytokine IL-10. A recent survey of adult asthmatics found evidence of B. pertussis infection (as measured by PCR from sputum samples) in almost 30% of mild, and 20% of moderate, asthmatics (versus 16% of healthy control subjects); B. pertussis-positive subjects also had lower forced expiratory volumes and more symptoms of asthma than did B. pertussis-negative individuals [56]. Furthermore, in accordance with the role that IL-17 plays in murine asthma models [57], IL-17 mRNA levels were found to be elevated in sputum samples from human asthmatic patients, along with higher neutrophil counts [58]. Therefore, B. pertussis infection, possibly through induction of a Th17 response, might impinge adversely on other airway pathologies.
Conclusions Protective immunity to B. pertussis is complex and involves a diversity of immune cells and responses [4]. The current literature supports the idea that B. pertussis virulence factors collectively promote infection caused by this pathogen through modulation and suppression of the host immune response. Could this immunomodulation, through induction of a Th17 response and the chronic autoimmune inflammation that might occur in the airways as a result, also be responsible for the cough pathology of pertussis? Currently, this is mere speculation, as there is no direct evidence for the cause of the cough. Another hypothesis is that PT contributes to the cough pathology indirectly through long-lived effects on airway muscle and nerve cells that produce the cough response. Several receptors on neurons that control airway responses signal through PT-sensitive G proteins [59], and recent studies have shown that PT is able to affect airway muscle and nerve cells [60–63]. Therefore, if G protein modification by PT in these cells is long-lived, these PT modulatory effects could account for the paroxysmal nature of coughing and the long-lived hyperreactivity of the airways in pertussis disease. If these speculations are borne out by further studies, treatments to reduce airway pathology will need to be aimed at reducing the harmful effects of Current Opinion in Pharmacology 2007, 7:272–278
276 Respiratory
IL-17 and the Th17-mediated autoimmune response, or at increasing G protein turnover in affected cells to remove the inhibitory effects of PT, treatments that are far from reaching development. Certainly, conventional anti-tussive medications have no benefit for pertussis patients [64], and so, in addition to novel ideas on pertussis vaccine development [65], new thinking and approaches are surely necessary for the development of effective therapies for this disease.
Acknowledgements I would like to thank Dr Ina Stephens for helpful discussions on pertussis disease and contributions towards this review, and Dr Brendan Canning for guidance in preparation of the review. Work in the author’s laboratory was funded by National Institutes of Health grants AI063080, AI060863 and AI050022.
References and recommended reading Papers of particular interest, published within the period of review, have been highlighted as: of special interest of outstanding interest 1.
cyclase toxin synergize in promoting lysis of monocytes. Infect Immun 2006, 74:2207-2214. 13. Mobberley-Schuman PS, Weiss AA: Influence of CR3 (CD11b/ CD18) expression on phagocytosis of Bordetella pertussis by human neutrophils. Infect Immun 2005, 73:7317-7323. 14. Carbonetti NH, Artamonova GV, Andreasen C, Bushar N: Pertussis toxin and adenylate cyclase toxin provide a one-two punch for establishment of Bordetella pertussis infection of the respiratory tract. Infect Immun 2005, 73:2698-2703. In this study, we show that PT plays an earlier role than ACT in promoting airway infection in the mouse model, possibly by inhibiting early neutrophil influx into the airways. 15. Bagley KC, Abdelwahab SF, Tuskan RG, Fouts TR, Lewis GK: Pertussis toxin and the adenylate cyclase toxin from Bordetella pertussis activate human monocyte-derived dendritic cells and dominantly inhibit cytokine production through a cAMP-dependent pathway. J Leukoc Biol 2002, 72:962-969. 16. Ross PJ, Lavelle EC, Mills KH, Boyd AP: Adenylate cyclase toxin from Bordetella pertussis synergizes with lipopolysaccharide to promote innate interleukin-10 production and enhances the induction of Th2 and regulatory T cells. Infect Immun 2004, 72:1568-1579. 17. Skinner JA, Reissinger A, Shen H, Yuk MH: Bordetella type III secretion and adenylate cyclase toxin synergize to drive dendritic cells into a semimature state. J Immunol 2004, 173:1934-1940.
Mattoo S, Cherry JD: Molecular pathogenesis, epidemiology, and clinical manifestations of respiratory infections due to Bordetella pertussis and other Bordetella subspecies. Clin Microbiol Rev 2005, 18:326-382. Comprehensive review of all aspects of B. pertussis biology, infection and disease.
18. Boyd AP, Ross PJ, Conroy H, Mahon N, Lavelle EC, Mills KH: Bordetella pertussis adenylate cyclase toxin modulates innate and adaptive immune responses: distinct roles for acylation and enzymatic activity in immunomodulation and cell death. J Immunol 2005, 175:730-738.
2.
Crowcroft NS, Pebody RG: Recent developments in pertussis. Lancet 2006, 367:1926-1936.
19. Flak TA, Heiss LN, Engle JT, Goldman WE: Synergistic epithelial responses to endotoxin and a naturally occurring muramyl peptide. Infect Immun 2000, 68:1235-1242.
3.
Preston A: Bordetella pertussis: the intersection of genomics and pathobiology. CMAJ 2005, 173:55-62.
4.
Mills KH: Immunity to Bordetella pertussis. Microbes Infect 2001, 3:655-677.
5.
Finlay BB, McFadden G: Anti-immunology: evasion of the host immune system by bacterial and viral pathogens. Cell 2006, 124:767-782.
6.
Edwards JA, Groathouse NA, Boitano S: Bordetella bronchiseptica adherence to cilia is mediated by multiple adhesin factors and blocked by surfactant protein A. Infect Immun 2005, 73:3618-3626.
7.
Perez Vidakovics ML, Lamberti Y, van der Pol WL, Yantorno O, Rodriguez ME: Adenylate cyclase influences filamentous haemagglutinin-mediated attachment of Bordetella pertussis to epithelial alveolar cells. FEMS Immunol Med Microbiol 2006, 48:140-147.
8.
Zaretzky FR, Gray MC, Hewlett EL: Mechanism of association of adenylate cyclase toxin with the surface of Bordetella pertussis: a role for toxin-filamentous haemagglutinin interaction. Mol Microbiol 2002, 45:1589-1598.
9.
McGuirk P, McCann C, Mills KH: Pathogen-specific T regulatory 1 cells induced in the respiratory tract by a bacterial molecule that stimulates interleukin 10 production by dendritic cells: a novel strategy for evasion of protective T helper type 1 responses by Bordetella pertussis. J Exp Med 2002, 195:221-231.
10. Mobberley-Schuman PS, Connelly B, Weiss AA: Phagocytosis of Bordetella pertussis incubated with convalescent serum. J Infect Dis 2003, 187:1646-1653.
20. Cundell DR, Kanthakumar K, Taylor GW, Goldman WE, Flak T, Cole PJ, Wilson R: Effect of tracheal cytotoxin from Bordetella pertussis on human neutrophil function in vitro. Infect Immun 1994, 62:639-643. 21. Magalhaes JG, Philpott DJ, Nahori MA, Jehanno M, Fritz J, Bourhis LL, Viala J, Hugot JP, Giovannini M, Bertin J et al.: Murine Nod1 but not its human orthologue mediates innate immune detection of tracheal cytotoxin. EMBO Rep 2005, 6:1201-1207. 22. Swaminathan CP, Brown PH, Roychowdhury A, Wang Q, Guan R, Silverman N, Goldman WE, Boons GJ, Mariuzza RA: Dual strategies for peptidoglycan discrimination by peptidoglycan recognition proteins (PGRPs). Proc Natl Acad Sci USA 2006, 103:684-689. 23. Chang CI, Chelliah Y, Borek D, Mengin-Lecreulx D, Deisenhofer J: Structure of tracheal cytotoxin in complex with a heterodimeric pattern-recognition receptor. Science 2006, 311:1761-1764. 24. Kaneko T, Yano T, Aggarwal K, Lim JH, Ueda K, Oshima Y, Peach C, Erturk-Hasdemir D, Goldman WE, Oh BH et al.: PGRPLC and PGRP-LE have essential yet distinct functions in the drosophila immune response to monomeric DAP-type peptidoglycan. Nat Immunol 2006, 7:715-723. This study demonstrates that TCT binds to peptidoglycan-recognition proteins and potently stimulates an immune response signaling pathway. 25. Yuk MH, Harvill ET, Cotter PA, Miller JF: Modulation of host immune responses, induction of apoptosis and inhibition of NF-kappaB activation by the Bordetella type III secretion system. Mol Microbiol 2000, 35:991-1004.
11. Vojtova J, Kamanova J, Sebo P: Bordetella adenylate cyclase toxin: a swift saboteur of host defense. Curr Opin Microbiol 2006, 9:69-75. Excellent recent review of ACT, including its immunomodulatory effects.
26. Kuwae A, Matsuzawa T, Ishikawa N, Abe H, Nonaka T, Fukuda H, Imajoh-Ohmi S, Abe A: BopC is a novel type III effector secreted by Bordetella bronchiseptica and has a critical role in type III-dependent necrotic cell death. J Biol Chem 2006, 281:6589-6600.
12. Basler M, Masin J, Osicka R, Sebo P: Pore-forming and enzymatic activities of Bordetella pertussis adenylate
27. Skinner JA, Pilione MR, Shen H, Harvill ET, Yuk MH: Bordetella type III secretion modulates dendritic cell migration resulting
Current Opinion in Pharmacology 2007, 7:272–278
www.sciencedirect.com
Immunomodulation in the pathogenesis of Bordetella pertussis infection and disease Carbonetti 277
in immunosuppression and bacterial persistence. J Immunol 2005, 175:4647-4652. 28. Reissinger A, Skinner JA, Yuk MH: Downregulation of mitogenactivated protein kinases by the Bordetella bronchiseptica type III secretion system leads to attenuated nonclassical macrophage activation. Infect Immun 2005, 73:308-316. 29. Pilione MR, Harvill ET: The Bordetella bronchiseptica type III secretion system inhibits gamma interferon production that is required for efficient antibody-mediated bacterial clearance. Infect Immun 2006, 74:1043-1049. 30. Legarda D, Klein-Patel ME, Yim S, Yuk MH, Diamond G: Suppression of NF-kappaB-mediated beta-defensin gene expression in the mammalian airway by the Bordetella type III secretion system. Cell Microbiol 2005, 7:489-497. 31. Reisine T: Pertussis toxin in the analysis of receptor mechanisms. Biochem Pharmacol 1990, 39:1499-1504. 32. Munoz JJ, Arai H, Bergman RK, Sadowski PL: Biological activities of crystalline pertussigen from Bordetella pertussis. Infect Immun 1981, 33:820-826. 33. Carbonetti NH, Artamonova GV, Mays RM, Worthington ZE: Pertussis toxin plays an early role in respiratory tract colonization by Bordetella pertussis. Infect Immun 2003, 71:6358-6366. 34. Kirimanjeswara GS, Agosto LM, Kennett MJ, Bjornstad ON, Harvill ET: Pertussis toxin inhibits neutrophil recruitment to delay antibody-mediated clearance of Bordetella pertussis. J Clin Invest 2005, 115:3594-3601. In this study, PT is shown to inhibit antibody-mediated clearance of B. pertussis from the lower respiratory tract through a mechanism involving the inhibition of neutrophil recruitment to the airways. 35. Van Rooijen N, Sanders A: Liposome mediated depletion of macrophages: mechanism of action, preparation of liposomes and applications. J Immunol Methods 1994, 174:83-93. 36. Carbonetti NH, Artamonova GV, van Rooijen N, Ayala VI: Pertussis toxin targets airway macrophages to promote Bordetella pertussis infection of the respiratory tract. Infect Immun 2007, 75, in press. This report demonstrates that a primary role for PT in promoting early B. pertussis infection is to combat the protective activities of resident airway macrophages, and that PT modification of airway macrophage G proteins is a long-lived effect. 37. Mielcarek N, Riveau G, Remoue F, Antoine R, Capron A, Locht C: Homologous and heterologous protection after single intranasal administration of live attenuated recombinant Bordetella pertussis. Nat Biotechnol 1998, 16:454-457. 38. Carbonetti NH, Artamonova GV, Andreasen C, Dudley E, Mays RM, Worthington ZE: Suppression of serum antibody responses by pertussis toxin after respiratory tract colonization by Bordetella pertussis and identification of an immunodominant lipoprotein. Infect Immun 2004, 72:3350-3358. 39. Shumilla JA, Lacaille V, Hornell TM, Huang J, Narasimhan S, Relman DA, Mellins ED: Bordetella pertussis infection of primary human monocytes alters HLA-DR expression. Infect Immun 2004, 72:1450-1462. 40. Martino A, Volpe E, Auricchio G, Colizzi V, Baldini PM: Influence of pertussis toxin on CD1a isoform expression in human dendritic cells. J Clin Immunol 2006, 26:153-159. 41. Akira S: TLR signaling. Curr Top Microbiol Immunol 2006, 311:1-16. 42. Higgins SC, Lavelle EC, McCann C, Keogh B, McNeela E, Byrne P, O’Gorman B, Jarnicki A, McGuirk P, Mills KH: Toll-like receptor 4-mediated innate IL-10 activates antigen-specific regulatory T cells and confers resistance to Bordetella pertussis by inhibiting inflammatory pathology. J Immunol 2003, 171:3119-3127. 43. Banus HA, Vandebriel RJ, de Ruiter H, Dormans JA, Nagelkerke NJ, Mooi FR, Hoebee B, van Kranen HJ, Kimman TG: Host genetics of Bordetella pertussis infection in mice: www.sciencedirect.com
significance of Toll-like receptor 4 in genetic susceptibility and pathobiology. Infect Immun 2006, 74:2596-2605. 44. Mann PB, Kennett MJ, Harvill ET: Toll-like receptor 4 is critical to innate host defense in a murine model of bordetellosis. J Infect Dis 2004, 189:833-836. 45. Mann PB, Elder KD, Kennett MJ, Harvill ET: Toll-like receptor 4-dependent early elicited tumor necrosis factor alpha expression is critical for innate host defense against Bordetella bronchiseptica. Infect Immun 2004, 72:6650-6658. 46. Mann PB, Wolfe D, Latz E, Golenbock D, Preston A, Harvill ET: Comparative toll-like receptor 4-mediated innate host defense to Bordetella infection. Infect Immun 2005, 73:8144-8152. This study shows that B. pertussis LPS signals through TLR4 to elicit milder responses than those elicited by B. bronchiseptica LPS, contributing to different outcomes in these two infections. 47. Higgins SC, Jarnicki AG, Lavelle EC, Mills KH: TLR4 mediates vaccine-induced protective cellular immunity to bordetella pertussis: role of il-17-producing T cells. J Immunol 2006, 177:7980-7989. This study demonstrates the importance of TLR4 signaling and IL-17 production to pertussis vaccine-mediated protective cellular immunity to B. pertussis infection, including a possible role for IL-17 in the activation of macrophage killing of B. pertussis. 48. Harrington LE, Mangan PR, Weaver CT: Expanding the effector CD4 T-cell repertoire: the Th17 lineage. Curr Opin Immunol 2006, 18:349-356. 49. Mascart F, Verscheure V, Malfroot A, Hainaut M, Pierard D, Temerman S, Peltier A, Debrie AS, Levy J, Del Giudice G, Locht C: Bordetella pertussis infection in 2-month-old infants promotes type 1 T cell responses. J Immunol 2003, 170:1504-1509. 50. Fedele G, Stefanelli P, Spensieri F, Fazio C, Mastrantonio P, Ausiello CM: Bordetella pertussis-infected human monocytederived dendritic cells undergo maturation and induce Th1 polarization and interleukin-23 expression. Infect Immun 2005, 73:1590-1597. 51. Spensieri F, Fedele G, Fazio C, Nasso M, Stefanelli P, Mastrantonio P, Ausiello CM: Bordetella pertussis inhibition of interleukin-12 (IL-12) p70 in human monocyte-derived dendritic cells blocks IL-12 p35 through adenylate cyclase toxin-dependent cyclic AMP induction. Infect Immun 2006, 74:2831-2838. Here, the authors show that ACT can inhibit IL-12 while inducing IL-23 production from DCs exposed to B. pertussis. 52. Siciliano NA, Skinner JA, Yuk MH: Bordetella bronchiseptica modulates macrophage phenotype leading to the inhibition of CD4+ T cell proliferation and the initiation of a Th17 immune response. J Immunol 2006, 177:7131-7138. These authors demonstrate that B. bronchiseptica, through ACT and TTSS activities, modulates macrophages to produce prostaglandin, which inhibits antigen-driven T cell proliferation, and to induce a Th17 phenotype in response to infection. 53. Happel KI, Dubin PJ, Zheng M, Ghilardi N, Lockhart C, Quinton LJ, Odden AR, Shellito JE, Bagby GJ, Nelson S, Kolls JK: Divergent roles of IL-23 and IL-12 in host defense against Klebsiella pneumoniae. J Exp Med 2005, 202:761-769. 54. Langrish CL, Chen Y, Blumenschein WM, Mattson J, Basham B, Sedgwick JD, McClanahan T, Kastelein RA, Cua DJ: IL-23 drives a pathogenic T cell population that induces autoimmune inflammation. J Exp Med 2005, 201:233-240. 55. Ennis DP, Cassidy JP, Mahon BP: Prior Bordetella pertussis infection modulates allergen priming and the severity of airway pathology in a murine model of allergic asthma. Clin Exp Allergy 2004, 34:1488-1497. 56. Harju TH, Leinonen M, Nokso-Koivisto J, Korhonen T, Raty R, He Q, Hovi T, Mertsola J, Bloigu A, Rytila P, Saikku P: Pathogenic bacteria and viruses in induced sputum or pharyngeal secretions of adults with stable asthma. Thorax 2006, 61:579-584. 57. Hellings PW, Kasran A, Liu Z, Vandekerckhove P, Wuyts A, Overbergh L, Mathieu C, Ceuppens JL: Interleukin-17 Current Opinion in Pharmacology 2007, 7:272–278
278 Respiratory
orchestrates the granulocyte influx into airways after allergen challenge inhalation in a mouse model of allergic asthma. Am J Respir Cell Mol Biol 2003, 28:42-50. 58. Bullens DM, Truyen E, Coteur L, Dilissen E, Hellings PW, Dupont LJ, Ceuppens JL: IL-17 mRNA in sputum of asthmatic patients: linking T cell driven inflammation and granulocytic influx? Respir Res 2006, 7:135. 59. Mazzone SB, Canning BJ: Central nervous system control of the airways: pharmacological implications. Curr Opin Pharmacol 2002, 2:220-228. 60. Yoshihara S, Morimoto H, Ohori M, Yamada Y, Abe T, Arisaka O: A neuroactive steroid inhibits guinea pig airway sensory nerves via Maxi-K channel activation. Int Arch Allergy Immunol 2006, 141:31-36. 61. Rong Zhou J, Shirasaki T, Soeda F, Takahama K: Potentiation of nicotinic currents by bradykinin in the paratracheal ganglia neurons of rats. Eur J Pharmacol 2006, 531:96-102.
Current Opinion in Pharmacology 2007, 7:272–278
62. Osawa Y, Xu D, Sternberg D, Sonett JR, D’Armiento J, Panettieri RA, Emala CW: Functional expression of the GABAB receptor in human airway smooth muscle. Am J Physiol Lung Cell Mol Physiol 2006, 291:L923-L931. 63. Ethier MF, Madison JM: Adenosine A1 receptors mediate mobilization of calcium in human bronchial smooth muscle cells. Am J Respir Cell Mol Biol 2006, 35:496-502. 64. Pillay V, Swingler G: Symptomatic treatment of the cough in whooping cough. Cochrane Database Syst Rev 2003, issue 4:CD003257. 65. Mielcarek N, Debrie AS, Raze D, Bertout J, Rouanet C, Younes AB, Creusy C, Engle J, Goldman WE, Locht C: Live attenuated B. pertussis as a single-dose nasal vaccine against whooping cough. PLoS Pathog 2006, 2:e65. The authors describe an attenuated B. pertussis strain (deficient in PT and TCT production) that induces strong protective immunity after intranasal infection of mice as a potential novel vaccine approach for pertussis.
www.sciencedirect.com