- Email: [email protected]
Novel probiotics for the management of allergic inflammation
DIGEST 1lYEA OIS 2002:34ISUPPl.2~:S25-8
ovel probiotics
for the management
T. von der Weid N. Ibnou-Zekri A. Pfeifer
Several pathologies of the gastrointestinal tract, particularly food allergy are due to an exaggerated and imbalanced response of the gut mucosal immune system. The intestinal microflora is an important constituent of the gut mucosal barrier against food allergens and there is increasing evidence that one important acquired factor predisposing to food allergy in infants is the gut microflora. Indeed, the balance of bifidobacteria versus Clostridia in the neonatal flora appears to determine the allergic status in infants. In earlier studies, it was shown that the higher prevalence of allergies in infants fed standard formulas, compared to breast-fed infants, correlated with lower frequencies of bifidobacteria in their faeces. Certain Lactobacillus probiotic strains can have an inhibitory impact on allergic inflammation. The mechanisms implicated are still unclear: but it seems that they can involve both proteolytic and/or immunomodulatory functions. One challenge will be to find a probiotic strain that elicits all these functions and that fulfills all safety criteria.
Digest
Liver
Key words:
From
Nest/& Research Center, Leusanne 26, Switzerland. Address hr cem~dence Dr. T. von der Weid, Ne&l@ Research Center, P.O. Box 44, 1000 Lausanne 26, Switzerland. Fax +4 1-2 I- 7858549. E-mail: thierry. [email protected] Achnowhvd~ents
Critical reading of manuscript by Drs. E.J. SchifhYn,R. Fritschti and P. Guesry is grateMy acknowledged.
of allergic inflammation
Dis 2002;341SuppL21:S25-8 food allergy;
intestinal
microflora;
probiotics
It has been shown in a number of studies that a certain category of lactic acid bacteria displaying probiotic properties had the capacity to stimulate discrete functions of the immune system and, thus, offered the potential to increase the capacity of the host to fight against a number of gastrointestinal (GI) infections at revealed in recent reviews ’ l. However, several pathologies of the GI tract are not due to a lack of stimulation of the mucosal immune system, but rather to its exaggerated and imbalanced response. Indeed, the gut-associated lymphoid tissue (GALT) is a very complex and compartmentalised tissue that is designed to fight against intestinal pathogens, while remaining tolerant to innocuous antigens from food components or from the commensal bacterial flora. This homeostasis can be disrupted by a number of factors and can lead to immunopathological situations, such as food allergy. The factors that may predispose subjects to food allergy can be quite diverse, but it is clear that they can be both genetically inherited and environmentally acquired 3. The recent rise in the incidence of atopy in “westernised” communities 4-7, along with evidence from studies on migrant populations *, emphasises the importance of environmental factors for the development of atopy. There is increasing evidence that one important acquired factor predisposing to food allergy in infants is the gut microflora. Indeed, the balance of bifidobacteria versus Clostridia in the neonatal flora appears to determine the allergic status in infants 9. In earlier studies, it was shown that the higher prevalence of allergies in infants fed standard formulas, compared to breast-fed infants, correlated with lower frequencies of bifidobacteria in their faeces ‘O-12.In addition to bifidobacteria, several epidemiological studies clearly support the beneficial effects of lactobacilli against food allergy. For example, one study performed in Estonia, where prevalence of allergy is low, and in Sweden, where prevalence is high, has
s25
Probiotics and allergy
demonstrated that allergic children in both countries were less often colonized with lactobacilli. In contrast, allergic children harboured higher counts of aerobes, particularly coliforms and Staphylococcus aureus 13. Thus, the intestinal microflora is an important constituent of the gut mucosal barrier against food allergens. In the absence of intestinal microflora, antigen transport is increased I4 and the induction of oral tolerance may be abrogated 15-17 . Intact, rather than intestinally processed cow’s milk proteins have been shown to stimulate peripheral blood mononuclear cells to release proinflammatory cytokines in patients with cow’s milk allergy ‘* . In line with this, it has been shown that cow’s milk proteins degraded by lactobacilli may generate non-allergenic peptides from the native protein I’). These findings suggested that one mechanism by which specific strains of lactobacilli may aid in host protection against allergic sensitisation was by degradation of potentially allergenic epitopes in the intestinal lumen. However, only proteolysis of allergenic epitopes is not sufficient to explain the clear anti-allergic effects of certain strains of lactic acid bacteria that have been demonstrated in several clinical trials on atopic dermatitis. Indeed, supplementation of extensively hydrolysed formulas (EHF) with Luctobacillus rhamnosus GG increased the therapeutic 2” and preventive 2’ anti-allergic effects of these formulas. Because the average molecular weight of cow’s milk peptides in EHFs is already extremely small (400 Dalton), it is unlikely that the anti-allergic effects of Lactobacillus rhamnosus GG were mediated through proteolytic activity in the intestinal lumen. Furthermore, another important consequence of these clinical trials was the realization that probiotics may counteract inflammatory responses beyond the intestinal milieu and dispense their anti-allergic effect in the skin. This further supported the notion that the major impact of probiotics was elicited at the systemic level on the allergic inflammatory status of the patient, probably via an immunological mechanism. The cellular mechanisms underlying the disruption of immunological homeostasis that eventually leads to allergic inflammatory responses against environmental antigens are becoming well documented as shown in a recent review ?*. The development of acquired immune responses is orchestrated by CD4’ T cells and allergic reactions result from a dysfunction of these cells Z3. CD4’ T lymphocytes can be classified into several subsets depending on the type of cytokines they produce. Originally, two major subsets of effector CD4’ T cells were described as belonging to the Thl and Th2 subset. These subsets carry out distinct essential regulatory functions in an immune response. Thl-derived cytokines mediate principally cell mediated immune functions, such as killing of intracellular bacteria by S26
macrophages. In contrast, Th2 cytokines mostly favour the generation of humoral responses dominated by TgE that are required for elimination of helminth infections as demonstrated in a recent review 11. These two types of responses are by and large mutually exclusive and regulate each other through feed-back loops mediated by antagonistic cytokines 2526. The balance between the two types of responses is considered important to maintain homeostasis of the host, since a number of immunopathologies have been associated with an exaggerated Thl or Th2 response. Allergy has been associated with an excessive Th2 response 27. The Thl/Th2 balance is thought to be maintained by specialized subsets of regulatory cells that produce suppressive cytokines such as IL-10 and TGF-P 2xI’). These regulatory cells have been described in the gut and probably play a key role in oral tolerance and gut homeostasis 2X3n. In the light of this antagonism between Thl and Th2 responses, proof of an inverse association between microbial infections early in life and atopy has led to renewed interest in the hygiene hypothesis ?I. It has been proposed that the recent rapid rise in atopy might be the result of improved hygiene and reduced family size. Recent epidemiological studies have yielded results both in favour 32-34and against 35such a hypothesis. Likewise, it has been proposed that these microbes may not necessarily be pathogens, since colonising intestinal microbes are also important for programming the developing immune system through the GALT 3h. Thus, components of the gut microflora may modulate allergic inflammatory processes by inducing a local and transient Th I immunity during intestinal colonization at birth j7 38. Postnatal colonization and probiotics may, therefore, act as an antagonist against the default Th2 environment that prevails in the neonatal intestinal environment j9 jg. This mechanism has been substantiated in vitro and in mouse studies performed with Lactobacillus cusei strain shirota, showing a decrease of Th2 cytokines and IgE with a concomitant increase of Thl cytokines ‘I ‘I. A novel probiotic strain of Lactobacillus paracasei (strain NCC246 1) isolated at the Nestle Research Center from faeces of a healthy baby has displayed similar properties in vitro U and in mice (Ibnou-Zekri et al., submitted). Indeed, L. parucasei (NCC2461) induced strong and transient Thl cytokines in macrophages and, consequently, inhibited the generation of Th2 cytokines in long-term cultures of CD4’ T cells. Furthermore, this probiotic also markedly decreased the production of P-lactoglobulin-specific IgE in cultures of splenocytes from mice sensitised to this allergen (von der Weid, unpublished). Thus, a potentially pathogenic Th2 reaction could be deviated towards a more innocuous response. Experimentally, this process has been called “immune deviation” 44 and has been proposed as ~-l__.._-l_rrm_
1. uon der Weid et al
a tool for immune therapy in allergic diseases 45. However, one concern about immune deviation by probiotics is that a switch from Th2 towards Thl cytokines may lead to cellular infiltration of Thl cells and release of pro-inflammatory cytokines in the intestinal mucosa. Therefore, it is important to demonstrate that those probiotics also induce anti-inflammatory cytokines and, thus, promote a feedback loop in order to prevent the onset of intestinal inflammation. Accordingly, we have shown in vitro that Luctobacillus pamcasei strain NCC2461 induced a regulatory population of CD4’ T cells that produced high amounts of IL- 10 and TGF-P and that could suppress bystander Thl and Th2 cytokines 13. Similarly, earlier studies have demonstrated that Lactobacillus johnsonii strain La1 induces the secretion of TGF-B in cocultures of intestinal epithelial CACO-2 cells with human mononuclear cells 4h. Along with these experimental data, clinical trials where L. rhamnosus GG was administered to atopic infants have shown that there was an increase of circulating TGF-P 47 and IL- 10 48 in the serum of patient receiving the probiotic. Because of their capacity to induce anti-inflammatory cytokines in vitro, we are currently performing clinical trials comparing the antiallergic properties of L. johnsonii strain La1 and L. paracasei strain NCC2461 in adult allergic patients and in atopic infants with cow’s milk allergies. In conclusion, it is becoming clear that certain Luctobacillus probiotic strains can have an inhibitory impact on allergic inflammation. The mechanisms implicated are still unclear, but it seems that they can involve both proteolytic and/or immunomodulatory functions. One challenge will be to find a probiotic strain that elicits all these functions and that fulfills all safety criteria 49. List of abbreviations EHF: extensively hydrolysed formulas: phoid tissue; GI: gastrointestinal
GALT:
gut-associated
lym-
h Whincup PH, Cook DG, Strachan DP, Papacosta 0. Time trends in respiratory symptoms in childhood over a 24 year period. Arch Dis Child 1993;68:729-34. ’ Aberg N, Hesselmar B, Aberg B, Eriksson B. Increase of asthma, allergic rhinitis and eczema in Swedish schoolchildren between 1979 and 1991. Clin Exp Allergy 1995;25:815-9. ’ Crane J, O’Donnell TV, Prior IA, Waite DA. Symptoms of asthma, methacholine airway responsiveness and atopy in migrant Tokelauan children. N Z Med J 1989;102:36-8. ‘) Kalliomaki M, Kirjavainen P, Eerola E, Kero P, Salminen S, Isolauri E. Distinct patterns of neonatal gut microflora in infants in whom atopy was and was not developing. J Allergy Clin Immunol 2001;107: 129-34, ‘” Rubaltelli FF, Biadaioli R, Pecile P, Nicoletti breast- and bottle-fed infants. J Perinat Med
l? Intestinal flora in 1998;26: 186-9 1.
” Wharton BA, Balmer SE, Scott fecal flora in the newborn. Acta
studies of diet and 1994;36:579-84.
PH. Sorrento Paediatr Jpn
I2 Balmer SE, Wharton BA. Diet and faecal flora in the newborn: breast milk and infant formula. Arch Dis Child 1989;64: 1672-7. ” B’orksten B, Naaber P, Sepp E, Mikelsaar M. The intestinal miJ croflora in allergic Estonian and Swedish 2-year-old children. Clin Exp Allergy 1999;29:342-6. I4 Heyman M, Corthier G, JF. Intestinal absorption an experimental study germ-free mice. Pediatr
Petit A, Meslin JC, Moreau C, Desjeux of macromolecules during viral enteritis: on rotavirus-infected conventional and Res 1987;22:72-8.
I5 Moreau MC, Corthier G. Effect of the gastrointestinal microflora on induction and maintenance of oral tolerance to ovalbumin C3H/HeJ mice. Infect Immun 1988;56:2766-8.
in
I6 Gaboriau-Routhiau V, Moreau MC. Gut flora allows recovery of oral tolerance to ovalbumin in mice after transient breakdown mediated by cholera toxin or Escherichia coli heat-labile enterotoxin. Pediatr Res I996;39:625-9. ” Sudo N, Sawamura S, Tanaka K, AibaY, Kubo C, KogaY. quirement of intestinal bacteria1 flora for the development IgE production system fully susceptible to oral tolerance tion. J Immunol 1997; 159: 1739-45.
The reof an induc-
I8 Heyman M, Benlounes M, Candalh C, Blaton MA, Desjeux JF, DuPont C. Threshold for immune cells reactivity to milk antigens is highly decreased in cow’s milk allergic infants. J Pediatr Gastroenterol Nutr 1995;20:447-52. ” Sutas Y, Soppi E, Korhonen H, Syvaoja EL, Saxelin M, Rokka T, et al. Suppression of lymphocyte proliferation in vitro by bovine caseins hydrolyzed with Lactobacillus casei GG-derived enzymes. J Allergy Clin Immunol 1996;98:2 16-24. ‘” Majamaa H, Isolauri E. Probiotics: management of food allergy. 1997;99: 179-85.
a novel Allergy
J
approach in the Clin Immunol
” Kalliomaki M, Salminen S, Arvilommi H, Kero P, Koskinen Isolauri E. Probiotics in primary prevention of atopic disease: randomised placebo-controlled trial. Lancet 2001;357: 1076-9.
References ’ Meydani SN, Ha WK. Nutr 2000;71:861-72.
Immunologic
effects
of yogurt.
Am J Clin
” Coffman RL, von der Weid T. Multiple of T helper 2 (Th2) responses. J Exp
P, a
pathways for the initiation Med 1997; 185:373-5.
2 Pfeifer A, Rosat JP. Probiotics in alimentation: clinical evidence for their enhancement of the natural immunity of the gut. Probiotics, other nutritional factors and intestinal microflora. Philadelphia: Lippincott-Raven Publishers; 2000. p. 243-57. ’ Hopkin JM. Genetics of atopy. Pediatr Allergy Immunol I995;6: 139-44.
” Holt PG. Development halant allergens during pl):6-7.
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” Fiorentino DF, Zlotnik A, Vieira P, Mosmann TR, Howard M, Moore KW, et al. IL-10 acts on the antigen-presenting cell to inhibit cytokine production by Thl cells. J lmmunol 1991;146:3444-51.
AJ, Peat JK. Evidence for Ciba Found Symp 1997;206:
’ Peat JK, van den Berg RH, Green Woolcock AJ. Changing prevalence dren. Br Med J 1994;308:1591-6.
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CM, Leeder in Australian
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” Mosmann TR, Coffman RL. THl and TH2 terns of lymphokine secretion lead to different ties. Annu Rev Immunol 1989;7:145-73.
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JD, Secrist
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12 inhibits the production human CD4+ T lymphocytes. ” Maggi E. The THI/TH2 1998;3:233-44.
of IL-4 and IL- 10 in allergen-specific J Immunol 1995;155:111-7. paradigm
in allergy.
3y Lin H, Mosmann TR, Guilbert L, Tuntipopipat S, Wegmann Synthesis of T helper 2-type cytokines at the maternal-fetal face. J Immunol 1993; 15 1:4562-73.
Immunotechnology
2X Groux H, O’Garra A, Bigler M, Rouleau M, Antonenko S, de Vries JE, et al. A CD4+ T-cell subset inhibits antigen-specific Tcell responses and prevents colitis. Nature 1997;389:737-42. ” Chen Y, Kuchroo VK, Inobe J, Hafler DA, Weiner HL. Regulatory T cell clones induced by oral tolerance: suppression of autoimmune encephalomyelitis. Science 1994;265: 1237-40. ‘” Miller A, Lider 0, Roberts AB, Spom MB, Weiner HL. Suppressor T cells generated by oral tolerization to myelin basic protein suppress both in vitro and in vivo immune responses by the release of transforming growth factor beta after antigen-specific triggering. Proc Nat1 Acad Sci USA 1992;89:42 l-5. ” Strachan 1989;299:
DP. Hay 1259-60.
fever,
hygiene,
and household
” Shaheen SO, Aaby P, Hall AJ, Barker al. Measles and atopy in Guinea-Bissau.
DJ, Heyes Lancet
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CB, Shiell AW, 1996;347:1792-6.
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33 Shirakawa T, Enomoto T, Shimazu S, Hopkin JM. The inverse association between tuberculin responses and atopic disorder. Science 1997;275:77-9. ” Matricardi PM, Rapicetta M, et versus airborne epidemiological
Rosmini F, Riondino S, Fortini M, Ferrigno L, al. Exposure to foodborne and orofecal microbes viruses in relation to atopy and allergic asthma: study. Br Med J 2000;320:4 12-7.
” Paunio M, Heinonen OP. Virtanen M, Leinikki P, Patja A, Peltola H. Measles history and atopic diseases: a population-based cross-sectional study. J Am Med Ass 2000;283:343-6. jb Cebra JJ. Influences of microbiota on intestinal development. Am J Clin Nutr 1999;69:S 1046-5 j7 Holt PG, Sly in childhood: 1997;8:53-8. lx Martinez allergy
PD, Bjorksten B. Atopic a question of balance?
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PG. Role of microbial Lancet 1999;354(Suppl
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“’ Wegmann TG, Lin H, Guilbert L, Mosmann TR. Bidirectional cytokine interactions in the maternal-fetal relationship: is successful pregnancy a TH2 phenomenon? Immunol Today 1993; 14:353-6. ” Shida K, Makino K, Morishita A, Takamizawa K, Hachimura S, Ametani A, et al. Lactobacillus casei inhibits antigen-induced IgE secretion through regulation of cytokine production in murine splenocyte cultures. Int Arch Allergy Immunol 1998;115:278-87. ” Matsuzaki T, Yamazaki R, Hashimoto S, Yokokura T. The effect of oral feeding of Lactobacillus casei strain Shirota on immunoglobulin E production in mice. J Dairy Sci 1998;8 I :48-53. ” von der Weid T, Bulliard C, Schiffrin EJ. Induction by a lactic acid bacterium of a population of CD4(+) T cells with low proliferative capacity that produce transforming growth factor beta and interleukin-10. Clin Diagn Lab Immunol 2001;8:695-701. Aa Rocken dimension 1996;149: Q Parronchi in allergy.
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-Ih Haller D, Bode S. Non-pathogenic by intestinal 2000;47:79-87. 47 Isolauri in the 2000;30:
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C, Hammes bacteria epithelial
E, Arvola T, Sutas management of 1604-10.
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Schiffrin EJ, Blum cytokine response co-cultures. Gut
Y, Moilanen E, Salminen atopic eczema. Clin
1x Pessi T, Sutas Y, Hurme M, Isolauri E. Interleukinin atopic children following oral Lactobacillus Clin Exp Allergy 2000;30: 1804-g.
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Jy Salminen S, von Wright A, Morelli L, Marteau P, Brassart D, de Vos WM, et al. Demonstration of safety of probiotics - a review. Int J Food Microbial 1998;44:93-106.
ovel probiotics
for the management
T. von der Weid N. Ibnou-Zekri A. Pfeifer
Several pathologies of the gastrointestinal tract, particularly food allergy are due to an exaggerated and imbalanced response of the gut mucosal immune system. The intestinal microflora is an important constituent of the gut mucosal barrier against food allergens and there is increasing evidence that one important acquired factor predisposing to food allergy in infants is the gut microflora. Indeed, the balance of bifidobacteria versus Clostridia in the neonatal flora appears to determine the allergic status in infants. In earlier studies, it was shown that the higher prevalence of allergies in infants fed standard formulas, compared to breast-fed infants, correlated with lower frequencies of bifidobacteria in their faeces. Certain Lactobacillus probiotic strains can have an inhibitory impact on allergic inflammation. The mechanisms implicated are still unclear: but it seems that they can involve both proteolytic and/or immunomodulatory functions. One challenge will be to find a probiotic strain that elicits all these functions and that fulfills all safety criteria.
Digest
Liver
Key words:
From
Nest/& Research Center, Leusanne 26, Switzerland. Address hr cem~dence Dr. T. von der Weid, Ne&l@ Research Center, P.O. Box 44, 1000 Lausanne 26, Switzerland. Fax +4 1-2 I- 7858549. E-mail: thierry. [email protected] Achnowhvd~ents
Critical reading of manuscript by Drs. E.J. SchifhYn,R. Fritschti and P. Guesry is grateMy acknowledged.
of allergic inflammation
Dis 2002;341SuppL21:S25-8 food allergy;
intestinal
microflora;
probiotics
It has been shown in a number of studies that a certain category of lactic acid bacteria displaying probiotic properties had the capacity to stimulate discrete functions of the immune system and, thus, offered the potential to increase the capacity of the host to fight against a number of gastrointestinal (GI) infections at revealed in recent reviews ’ l. However, several pathologies of the GI tract are not due to a lack of stimulation of the mucosal immune system, but rather to its exaggerated and imbalanced response. Indeed, the gut-associated lymphoid tissue (GALT) is a very complex and compartmentalised tissue that is designed to fight against intestinal pathogens, while remaining tolerant to innocuous antigens from food components or from the commensal bacterial flora. This homeostasis can be disrupted by a number of factors and can lead to immunopathological situations, such as food allergy. The factors that may predispose subjects to food allergy can be quite diverse, but it is clear that they can be both genetically inherited and environmentally acquired 3. The recent rise in the incidence of atopy in “westernised” communities 4-7, along with evidence from studies on migrant populations *, emphasises the importance of environmental factors for the development of atopy. There is increasing evidence that one important acquired factor predisposing to food allergy in infants is the gut microflora. Indeed, the balance of bifidobacteria versus Clostridia in the neonatal flora appears to determine the allergic status in infants 9. In earlier studies, it was shown that the higher prevalence of allergies in infants fed standard formulas, compared to breast-fed infants, correlated with lower frequencies of bifidobacteria in their faeces ‘O-12.In addition to bifidobacteria, several epidemiological studies clearly support the beneficial effects of lactobacilli against food allergy. For example, one study performed in Estonia, where prevalence of allergy is low, and in Sweden, where prevalence is high, has
s25
Probiotics and allergy
demonstrated that allergic children in both countries were less often colonized with lactobacilli. In contrast, allergic children harboured higher counts of aerobes, particularly coliforms and Staphylococcus aureus 13. Thus, the intestinal microflora is an important constituent of the gut mucosal barrier against food allergens. In the absence of intestinal microflora, antigen transport is increased I4 and the induction of oral tolerance may be abrogated 15-17 . Intact, rather than intestinally processed cow’s milk proteins have been shown to stimulate peripheral blood mononuclear cells to release proinflammatory cytokines in patients with cow’s milk allergy ‘* . In line with this, it has been shown that cow’s milk proteins degraded by lactobacilli may generate non-allergenic peptides from the native protein I’). These findings suggested that one mechanism by which specific strains of lactobacilli may aid in host protection against allergic sensitisation was by degradation of potentially allergenic epitopes in the intestinal lumen. However, only proteolysis of allergenic epitopes is not sufficient to explain the clear anti-allergic effects of certain strains of lactic acid bacteria that have been demonstrated in several clinical trials on atopic dermatitis. Indeed, supplementation of extensively hydrolysed formulas (EHF) with Luctobacillus rhamnosus GG increased the therapeutic 2” and preventive 2’ anti-allergic effects of these formulas. Because the average molecular weight of cow’s milk peptides in EHFs is already extremely small (400 Dalton), it is unlikely that the anti-allergic effects of Lactobacillus rhamnosus GG were mediated through proteolytic activity in the intestinal lumen. Furthermore, another important consequence of these clinical trials was the realization that probiotics may counteract inflammatory responses beyond the intestinal milieu and dispense their anti-allergic effect in the skin. This further supported the notion that the major impact of probiotics was elicited at the systemic level on the allergic inflammatory status of the patient, probably via an immunological mechanism. The cellular mechanisms underlying the disruption of immunological homeostasis that eventually leads to allergic inflammatory responses against environmental antigens are becoming well documented as shown in a recent review ?*. The development of acquired immune responses is orchestrated by CD4’ T cells and allergic reactions result from a dysfunction of these cells Z3. CD4’ T lymphocytes can be classified into several subsets depending on the type of cytokines they produce. Originally, two major subsets of effector CD4’ T cells were described as belonging to the Thl and Th2 subset. These subsets carry out distinct essential regulatory functions in an immune response. Thl-derived cytokines mediate principally cell mediated immune functions, such as killing of intracellular bacteria by S26
macrophages. In contrast, Th2 cytokines mostly favour the generation of humoral responses dominated by TgE that are required for elimination of helminth infections as demonstrated in a recent review 11. These two types of responses are by and large mutually exclusive and regulate each other through feed-back loops mediated by antagonistic cytokines 2526. The balance between the two types of responses is considered important to maintain homeostasis of the host, since a number of immunopathologies have been associated with an exaggerated Thl or Th2 response. Allergy has been associated with an excessive Th2 response 27. The Thl/Th2 balance is thought to be maintained by specialized subsets of regulatory cells that produce suppressive cytokines such as IL-10 and TGF-P 2xI’). These regulatory cells have been described in the gut and probably play a key role in oral tolerance and gut homeostasis 2X3n. In the light of this antagonism between Thl and Th2 responses, proof of an inverse association between microbial infections early in life and atopy has led to renewed interest in the hygiene hypothesis ?I. It has been proposed that the recent rapid rise in atopy might be the result of improved hygiene and reduced family size. Recent epidemiological studies have yielded results both in favour 32-34and against 35such a hypothesis. Likewise, it has been proposed that these microbes may not necessarily be pathogens, since colonising intestinal microbes are also important for programming the developing immune system through the GALT 3h. Thus, components of the gut microflora may modulate allergic inflammatory processes by inducing a local and transient Th I immunity during intestinal colonization at birth j7 38. Postnatal colonization and probiotics may, therefore, act as an antagonist against the default Th2 environment that prevails in the neonatal intestinal environment j9 jg. This mechanism has been substantiated in vitro and in mouse studies performed with Lactobacillus cusei strain shirota, showing a decrease of Th2 cytokines and IgE with a concomitant increase of Thl cytokines ‘I ‘I. A novel probiotic strain of Lactobacillus paracasei (strain NCC246 1) isolated at the Nestle Research Center from faeces of a healthy baby has displayed similar properties in vitro U and in mice (Ibnou-Zekri et al., submitted). Indeed, L. parucasei (NCC2461) induced strong and transient Thl cytokines in macrophages and, consequently, inhibited the generation of Th2 cytokines in long-term cultures of CD4’ T cells. Furthermore, this probiotic also markedly decreased the production of P-lactoglobulin-specific IgE in cultures of splenocytes from mice sensitised to this allergen (von der Weid, unpublished). Thus, a potentially pathogenic Th2 reaction could be deviated towards a more innocuous response. Experimentally, this process has been called “immune deviation” 44 and has been proposed as ~-l__.._-l_rrm_
1. uon der Weid et al
a tool for immune therapy in allergic diseases 45. However, one concern about immune deviation by probiotics is that a switch from Th2 towards Thl cytokines may lead to cellular infiltration of Thl cells and release of pro-inflammatory cytokines in the intestinal mucosa. Therefore, it is important to demonstrate that those probiotics also induce anti-inflammatory cytokines and, thus, promote a feedback loop in order to prevent the onset of intestinal inflammation. Accordingly, we have shown in vitro that Luctobacillus pamcasei strain NCC2461 induced a regulatory population of CD4’ T cells that produced high amounts of IL- 10 and TGF-P and that could suppress bystander Thl and Th2 cytokines 13. Similarly, earlier studies have demonstrated that Lactobacillus johnsonii strain La1 induces the secretion of TGF-B in cocultures of intestinal epithelial CACO-2 cells with human mononuclear cells 4h. Along with these experimental data, clinical trials where L. rhamnosus GG was administered to atopic infants have shown that there was an increase of circulating TGF-P 47 and IL- 10 48 in the serum of patient receiving the probiotic. Because of their capacity to induce anti-inflammatory cytokines in vitro, we are currently performing clinical trials comparing the antiallergic properties of L. johnsonii strain La1 and L. paracasei strain NCC2461 in adult allergic patients and in atopic infants with cow’s milk allergies. In conclusion, it is becoming clear that certain Luctobacillus probiotic strains can have an inhibitory impact on allergic inflammation. The mechanisms implicated are still unclear, but it seems that they can involve both proteolytic and/or immunomodulatory functions. One challenge will be to find a probiotic strain that elicits all these functions and that fulfills all safety criteria 49. List of abbreviations EHF: extensively hydrolysed formulas: phoid tissue; GI: gastrointestinal
GALT:
gut-associated
lym-
h Whincup PH, Cook DG, Strachan DP, Papacosta 0. Time trends in respiratory symptoms in childhood over a 24 year period. Arch Dis Child 1993;68:729-34. ’ Aberg N, Hesselmar B, Aberg B, Eriksson B. Increase of asthma, allergic rhinitis and eczema in Swedish schoolchildren between 1979 and 1991. Clin Exp Allergy 1995;25:815-9. ’ Crane J, O’Donnell TV, Prior IA, Waite DA. Symptoms of asthma, methacholine airway responsiveness and atopy in migrant Tokelauan children. N Z Med J 1989;102:36-8. ‘) Kalliomaki M, Kirjavainen P, Eerola E, Kero P, Salminen S, Isolauri E. Distinct patterns of neonatal gut microflora in infants in whom atopy was and was not developing. J Allergy Clin Immunol 2001;107: 129-34, ‘” Rubaltelli FF, Biadaioli R, Pecile P, Nicoletti breast- and bottle-fed infants. J Perinat Med
l? Intestinal flora in 1998;26: 186-9 1.
” Wharton BA, Balmer SE, Scott fecal flora in the newborn. Acta
studies of diet and 1994;36:579-84.
PH. Sorrento Paediatr Jpn
I2 Balmer SE, Wharton BA. Diet and faecal flora in the newborn: breast milk and infant formula. Arch Dis Child 1989;64: 1672-7. ” B’orksten B, Naaber P, Sepp E, Mikelsaar M. The intestinal miJ croflora in allergic Estonian and Swedish 2-year-old children. Clin Exp Allergy 1999;29:342-6. I4 Heyman M, Corthier G, JF. Intestinal absorption an experimental study germ-free mice. Pediatr
Petit A, Meslin JC, Moreau C, Desjeux of macromolecules during viral enteritis: on rotavirus-infected conventional and Res 1987;22:72-8.
I5 Moreau MC, Corthier G. Effect of the gastrointestinal microflora on induction and maintenance of oral tolerance to ovalbumin C3H/HeJ mice. Infect Immun 1988;56:2766-8.
in
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