An enteric helminth infection protects against an allergic response to dietary antigen

Cestode regulation of inflammation and inflammatory diseases

Helminth parasites are masters of immune regulation; a likely prerequisite for long-term survival by circumventing their hosts' attempt to eradicate them. From a translational perspective, knowledge of immune events as a response to infection with a helminth parasite could be used to reduce the intensity of unwanted inflammatory reactions. Substantial data have accumulated showing that inflammatory reactions that promote a variety of auto-inflammatory diseases are dampened as a consequence of infection with helminth parasites, via either the mobilization of an anti-worm spectrum of immune events or by the direct effect of secretory/excretory bioactive immunomodulatory molecules released from the parasite. However, many issues are outstanding in the definition of the mechanism(s) by which infection with helminth parasites can affect the outcome, positively or negatively, of concomitant disease. We focus on a subgroup of this complex group of metazoan parasites, the cestodes, summarizing studies from rodent models that illustrate if, and by what mechanisms, infection with tapeworms ameliorate or exaggerate disease in their host. The ability of infection with cestodes, or other classes of helminth, to worsen a disease course or confer susceptibility to intracellular pathogens should be carefully considered in the context of 'helminth therapy'. In addition, poorly characterised cestode extracts can regulate murine and human immunocyte function, yet the impact of these in the context of autoimmune or allergic diseases is poorly understood. Thus, studies with cestodes, as representative helminths, have helped cement the concept that infection with parasitic helminths can inhibit concomitant disease; however, issues relating to long-term effects, potential side-effects, mixed pathogen infections and purification of immunomodulatory molecules from the parasite remain as challenges that need to be addressed in order to achieve the use of helminths as anti-inflammatory agents for human diseases.

Suppression of type 2 immunity and allergic airway inflammation by secreted products of the helminth Heligmosomoides polygyrus

Allergic asthma is less prevalent in countries with parasitic helminth infections, and mice infected with parasites such as Heligmosomoides polygyrus are protected from allergic airway inflammation. To establish whether suppression of allergy could be mediated by soluble products of this helminth, we tested H. polygyrus excretory-secretory (HES) material for its ability to impair allergic inflammation. When HES was added to sensitising doses of ovalbumin, the subsequent allergic airway response was suppressed, with ablated cell infiltration, a lower ratio of effector (CD4(+) CD25(+) Foxp3(-) ) to regulatory (CD4(+) Foxp3(+) ) T (Treg) cells, and reduced Th1, Th2 and Th17 cytokine production. HES exposure reduced IL-5 responses and eosinophilia, abolished IgE production and inhibited the type 2 innate molecules arginase-1 and RELM-α (resistin-like molecule-α). Although HES contains a TGF-β-like activity, similar effects in modulating allergy were not observed when administering mammalian TGF-β alone. HES also protected previously sensitised mice, suppressing recruitment of eosinophils to the airways when given at challenge, but no change in Th or Treg cell populations was apparent. Because heat-treatment of HES did not impair suppression at sensitisation, but compromised its ability to suppress at challenge, we propose that HES contains distinct heat-stable and heat-labile immunomodulatory molecules, which modulate pro-allergic adaptive and innate cell populations.

Helminth infections and host immune regulation

Helminth parasites infect almost one-third of the world's population, primarily in tropical regions. However, regions where helminth parasites are endemic record much lower prevalences of allergies and autoimmune diseases, suggesting that parasites may protect against immunopathological syndromes. Most helminth diseases are spectral in nature, with a large proportion of relatively asymptomatic cases and a subset of patients who develop severe pathologies. The maintenance of the asymptomatic state is now recognized as reflecting an immunoregulatory environment, which may be promoted by parasites, and involves multiple levels of host regulatory cells and cytokines; a breakdown of this regulation is observed in pathological disease. Currently, there is much interest in whether helminth-associated immune regulation may ameliorate allergy and autoimmunity, with investigations in both laboratory models and human trials. Understanding and exploiting the interactions between these parasites and the host regulatory network are therefore likely to highlight new strategies to control both infectious and immunological diseases.

Microbial regulation of allergic responses to food

The incidence of food allergy in developed countries is rising at a rate that cannot be attributed to genetic variation alone. In this review, we discuss the environmental factors that may contribute to the increasing prevalence of potentially fatal anaphylactic responses to food. Decreased exposure to enteric infections due to advances in vaccination and sanitation, along with the adoption of high-fat (Western) diets, antibiotic use, Cesarean birth, and formula feeding of infants, have all been implicated in altering the enteric microbiome away from its ancestral state. This collection of resident commensal microbes performs many important physiological functions and plays a central role in the development of the immune system. We hypothesize that alterations in the microbiome interfere with immune system maturation, resulting in impairment of IgA production, reduced abundance of regulatory T cells, and Th2-skewing of baseline immune responses which drive aberrant responses to innocuous (food) antigens.

Immune modulation and modulators in Heligmosomoides polygyrus infection

The intestinal nematode parasite Heligmosomoides polygyrus bakeri exerts widespread immunomodulatory effects on both the innate and adaptive immune system of the host. Infected mice adopt an immunoregulated phenotype, with abated allergic and autoimmune reactions. At the cellular level, infection is accompanied by expanded regulatory T cell populations, skewed dendritic cell and macrophage phenotypes, B cell hyperstimulation and multiple localised changes within the intestinal environment. In most mouse strains, these act to block protective Th2 immunity. The molecular basis of parasite interactions with the host immune system centres upon secreted products termed HES (H. polygyrus excretory-secretory antigen), which include a TGF-β-like ligand that induces de novo regulatory T cells, factors that modify innate inflammatory responses, and molecules that block allergy in vivo. Proteomic and transcriptomic definition of parasite proteins, combined with biochemical identification of immunogenic molecules in resistant mice, will provide new candidate immunomodulators and vaccine antigens for future research.

Nonallergen-specific treatments for food allergy

PURPOSE OF REVIEW

This review summarizes recent reports on nonallergen-specific therapies for food allergy. These therapies are especially appealing for food allergy because unlike allergen-specific immunotherapy, they would allow the treatment of multiple food allergies in a single patient with one therapy.

RECENT FINDINGS

Chinese herbal therapy, anti-IgE, probiotics, engineered lactic acid bacteria, and helminth therapy are all examples of allergen nonspecific therapies that have been investigated in recent years. Although some have only been studied in animal models of food allergy, some are undergoing rigorous, human clinical trials.

SUMMARY

Increasing amounts of research are examining the efficacy and safety of nonallergen-specific therapies for food allergy. There is hope that clinicians will have effective treatments either as an alternative or as an adjunct to immunotherapy.

The future of food allergy therapeutics

Food allergy is increasing in prevalence in westernized countries, leading to significant morbidity including nutritional deficiencies and growth delay as well as psychosocial burdens and the potential for fatal anaphylaxis. There is currently no effective form of therapy, and the mainstay of treatment remains strict avoidance. However, there are a number of promising therapeutic strategies currently being investigated for the treatment of food allergies. Allergen-specific approaches, such as various forms of immunotherapy, have been a major focus of investigation and appear to be promising methods of desensitization. More recently, the addition of anti-IgE monoclonal antibodies (mAbs) to immunotherapy regimens has been studied. Early work with antigen-fixed leukocytes in a murine model has shown promise in inducing tolerance, as have vaccines containing modified recombinant food proteins coadministered with heat-killed Escherichia coli. Nonspecific approaches include a Chinese herbal formulation, anti-IgE mAbs, and Trichuris suis ova therapy. The array of treatment modalities currently being investigated increases the likelihood of finding one or more effective therapies for the treatment of food allergy.

Efficacy and immunological actions of FAHF-2 in a murine model of multiple food allergies

BACKGROUND

Food Allergy Herbal Formula-2 (FAHF-2) prevents anaphylaxis in a murine model of peanut allergy. Multiple food allergies (MFA) are common and associated with a higher risk of anaphylaxis. No well-characterized murine model of sensitization to multiple food allergens exists, and no satisfactory therapy for MFA is currently available.

OBJECTIVE

To determine the effect of FAHF-2 in a murine model of MFA.

METHODS

C3H/HeJ mice were orally sensitized to peanut, codfish, and egg concurrently. Oral FAHF-2 treatment commenced 1 day after completing sensitization and continued daily for 7 weeks. Mice were subsequently orally challenged with each allergen.

RESULTS

Antibodies in sera from mice simultaneously sensitized with peanut, codfish, and egg recognized major allergens of all 3 foods, demonstrating sensitization to multiple unrelated food allergens (MFA mice). Sham-treated MFA mice exhibited anaphylactic symptoms accompanied by elevation of plasma histamine and hypothermia. In contrast, FAHF-2-treated MFA mice showed no anaphylactic symptoms, normal body temperature, and histamine levels after challenge with each allergen. Protection was accompanied by reduction in allergen-specific immunoglobulin E levels. Allergen-stimulated Th2 cytokine interleukin-4 and interleukin-13 production levels decreased, whereas the Th1 cytokine interferon-γ levels were elevated in cultured splenocytes and mesenteric lymph node cells in FAHF-2-treated mice.

CONCLUSION

We established the first murine model of MFA. FAHF-2 prevents peanut, egg, and fish-induced anaphylactic reactions in this model, suggesting that FAHF-2 may have potential for treating human MFA.

Environment and T regulatory cells in allergy

The central role of T regulatory cells in the responses against harmless environmental antigens has been confirmed by many studies. Impaired T regulatory cell function is implicated in many pathological conditions, particularly allergic diseases. The "hygiene hypothesis" suggests that infections and infestations may play a protective role for allergy, whereas environmental pollutants favor the development of allergic diseases. Developing countries suffer from a variety of infections and are also facing an increasing diffusion of environmental pollutants. In these countries allergies increase in relation to the spreading use of xenobiotics (pesticides, herbicides, pollution, etc.) with a rate similar to those of developed countries, overcoming the protective effects of infections. We review here the main mechanisms of non-self tolerance, with particular regard to relations between T regulatory cell activity, infections and infestations such as helminthiasis, and exposure to environmental xenobiotics with relevant diffusion in developing countries.

Chronic helminth infection reduces basophil responsiveness in an IL-10-dependent manner

Basophils play a key role in the development and effector phases of type 2 immune responses in both allergic diseases and helminth infections. This study shows that basophils become less responsive to IgE-mediated stimulation when mice are chronically infected with Litomosoides sigmodontis, a filarial nematode, and Schistosoma mansoni, a blood fluke. Although excretory/secretory products from microfilariae of L. sigmodontis suppressed basophils in vitro, transfer of microfilariae into mice did not result in basophil suppression. Rather, reduced basophil responsiveness, which required the presence of live helminths, was found to be dependent on host IL-10 and was accompanied by decreases in key IgE signaling molecules known to be downregulated by IL-10. Given the importance of basophils in the development of type 2 immune responses, these findings help explain the mechanism by which helminths protect against allergy and may have broad implications for understanding how helminth infections alter other disease states in people.

Induction of mud crab (Scylla paramamosain) tropomyosin and arginine kinase specific hypersensitivity in BALB/c mice

BACKGROUND

Shellfish hypersensitivity is among the most common food allergies. The allergens tropomyosin (TM) and arginine kinase (AK) from mud crab (Scylla paramamosain) were purified to homogeneity. BALB/c female mice were sensitized with TM and AK by intragastric administration. Mice treated with normal saline served as the negative control (NC) group.

RESULTS

Compared with NC group, mice that were treated with TM and AK developed reduced activity; meanwhile, their scratching behavior and specific-IgE level were increased. Specific-CD4 + T cells were significantly elevated in the splenocyte cultures of the mice upon TM and AK stimulation. However, compared with the positive control group (ovalbumin, OVA), there was no significant difference. The expression of IL-4 in culture cells stimulated by TM, AK, and OVA group showed significant differences from the NC group, respectively.

CONCLUSION

These results indicated that a BALB/c mouse model for sensitization to TM and AK from mud crab was successfully established, and the Th2 response was observed, displaying increased immunoglobulin E levels, together with the production of interleukin 4 and allergic symptoms.

Modulation of specific and allergy-related immune responses by helminths

Helminths are master regulators of host immune responses utilising complex mechanisms to dampen host protective Th2-type responses and favour long-term persistence. Such evasion mechanisms ensure mutual survival of both the parasite and the host. In this paper, we present recent findings on the cells that are targeted by helminths and the molecules and mechanisms that are induced during infection. We discuss the impact of these factors on the host response as well as their effect in preventing the development of aberrant allergic inflammation. We also examine recent findings on helminth-derived molecules that can be used as tools to pinpoint the underlying mechanisms of immune regulation or to determine new anti-inflammatory therapeutics.

Proteomic analysis of secretory products from the model gastrointestinal nematode Heligmosomoides polygyrus reveals dominance of venom allergen-like (VAL) proteins

The intestinal helminth parasite, Heligmosomoides polygyrus bakeri offers a tractable experimental model for human hookworm infections such as Ancylostoma duodenale and veterinary parasites such as Haemonchus contortus. Parasite excretory-secretory (ES) products represent the major focus for immunological and biochemical analyses, and contain immunomodulatory molecules responsible for nematode immune evasion. In a proteomic analysis of adult H. polygyrus secretions (termed HES) matched to an extensive transcriptomic dataset, we identified 374 HES proteins by LC-MS/MS, which were distinct from those in somatic extract HEx, comprising 446 identified proteins, confirming selective export of ES proteins. The predominant secreted protein families were proteases (astacins and other metalloproteases, aspartic, cysteine and serine-type proteases), lysozymes, apyrases and acetylcholinesterases. The most abundant products were members of the highly divergent venom allergen-like (VAL) family, related to Ancylostoma secreted protein (ASP); 25 homologues were identified, with VAL-1 and -2 also shown to be associated with the parasite surface. The dominance of VAL proteins is similar to profiles reported for Ancylostoma and Haemonchus ES products. Overall, this study shows that the secretions of H. polygyrus closely parallel those of clinically important GI nematodes, confirming the value of this parasite as a model of helminth infection.

Worm therapy: for or against?

This article succinctly reviews the weight of evidence supporting worm therapy, and asks the question whether the evidence is sufficient to support the use of parasitic worms as investigational medicinal products.

Future therapies for food allergies

Food allergy is an increasingly prevalent problem in westernized countries, and there is an unmet medical need for an effective form of therapy. A number of therapeutic strategies are under investigation targeting foods that most frequently provoke severe IgE-mediated anaphylactic reactions (peanut, tree nuts, and shellfish) or are most common in children, such as cow's milk and hen's egg. Approaches being pursued are both food allergen specific and nonspecific. Allergen-specific approaches include oral, sublingual, and epicutaneous immunotherapy (desensitization) with native food allergens and mutated recombinant proteins, which have decreased IgE-binding activity, coadministered within heat-killed Escherichia coli to generate maximum immune response. Diets containing extensively heated (baked) milk and egg represent an alternative approach to food oral immunotherapy and are already changing the paradigm of strict dietary avoidance for patients with food allergy. Nonspecific approaches include monoclonal anti-IgE antibodies, which might increase the threshold dose for food allergen in patients with food allergy, and a Chinese herbal formulation, which prevented peanut-induced anaphylaxis in a murine model and is currently being investigated in clinical trials. The variety of strategies for treating food allergy increases the likelihood of success and gives hope that accomplishing an effective therapy for food allergy is within reach.

Role of dendritic cells: a step forward for the hygiene hypothesis

The hygiene hypothesis was proposed more than two decades ago, but its mechanism remains unclear. This review focuses on recent advances in the field, especially on the role played by dendritic cells (DCs) and their modulating effects on various infections and allergic diseases, including allergic asthma. DCs isolated from mice long after the resolution of an infection were reported to have a significant modulating effect on allergen-specific Th2 responses in both in vitro and in vivo systems. These DCs showed DC1-like and/or tolerogenic DC capacity, which allowed for the inhibition of allergic responses by immune deviation (enhancing Th1 response) and immune regulation (through regulatory T-cell and Th2 hyporesponsiveness) mechanisms. These findings represented a significant advance in the elucidation of the mechanisms underlying the hygiene hypothesis. Further investigation on the mechanisms by which DCs are 'educated' by infectious agents and the influence of the type, time, and extent of infections on this 'education' process will help us understand immune regulation in disease settings and in the rational design of preventive/therapeutic approaches to allergy/asthma and infections.

Oral tolerance to food-induced systemic anaphylaxis mediated by the C-type lectin SIGNR1

We propose that a C-type lectin receptor, SIGNR-1, plays a role in conditioning gastrointestinal lamina propria (LP) DC subset for the induction of oral tolerance in a model of food-induced anaphylaxis. Oral delivery of bovine serum albumin (BSA) bearing 51 mols of mannosides (Man₅₁-BSA) significantly reduced the levels of BSA-induced anaphylactic response. Man₅₁-BSA was found to, selectively, target the LPDC subset expressing a member of the CLRs, SIGNR1, and induce the expression of IL-10, but not IL-6 and IL-12p70. This was noted also in Man₅₁-BSA-treated IL-10-GFPknockin (tiger) mice. The Man₅₁-BSA–SIGNR1 axis in LPDCs, both in vitro and in vivo, promoted the generation of CD4⁺ Tr1-like cells expressing IL-10 and IFN-γ, in a SIGNR-1- and IL-10-dependent manner, but not of CD4⁺CD25⁺Foxp3⁺ Tregs. The in vivo-generated Tr1-like cells were capable of transferring tolerance. These results suggest the potential utility of sugar-modified antigen in oral tolerance through targeting of SIGNR1 and LPDCs.

Chronic helminth infections protect against allergic diseases by active regulatory processes

Developed countries are suffering from an epidemic rise in immunologic disorders, such as allergy-related diseases and certain autoimmunities. Several studies have demonstrated a negative association between helminth infections and inflammatory diseases (eg, allergy), providing a strong case for the involvement of helminth infections in this respect. However, some studies point in the opposite direction. The discrepancy may be explained by differences in frequency, dose, time, and type of helminth. In this review, new studies are discussed that may support the concept that chronic helminth infections in particular—but not acute infections—are associated with the expression of regulatory networks necessary for downmodulating allergic immune responses to harmless antigens. Furthermore, different components of regulatory networks are highlighted, such as the role of regulatory T and B cells, modulation of dendritic cells, early innate signals from structural cells (eg, epithelial cells), and their individual contributions to protection against allergic diseases. It is of great interest to define and characterize specific helminth molecules that have profound immunomodulatory capacities as targets for therapeutic application in the treatment or prophylaxis of allergic manifestations.

99th Dahlem conference on infection, inflammation and chronic inflammatory disorders: induction and control of regulatory T cells in the gastrointestinal tract: consequences for local and peripheral immune responses

Regulatory T cells play a crucial role in normal gut homeostasis, as well as during infection with microbial or parasitic pathogens. Prior to infection, interactions with the commensal microflora are essential to differentiation of a healthy steady-state level of immunoregulation, mediated through both Toll-like receptor-dependent and -independent pathways. The ingress of pathogenic organisms may, according to the context, promote or reverse the regulatory environment, with onward consequences for inflammation in both the intestinal and extra-intestinal settings. Appropriate regulation of gut immunity thus depends upon a complex three-way interplay between host cells, commensals and pathogens, and can exert a major impact on systemic responses including allergy and autoimmunity.

Helminth infection inhibits airway allergic reaction and dendritic cells are involved in the modulation process

Several previous studies have demonstrated that some helminth infections can inhibit allergic reactions, but the examination on the effect of live Schistosoma japonicum (SJ) infection on allergic inflammation remains limited. The aim of this study was to examine the effect and mechanism of chronic SJ infection on airway allergic inflammation in a murine model. The data showed that chronic SJ infection suppressed airway eosinophilia, mucus production and antigen-specific IgE responses induced by ovalbumin (OVA) sensitization and challenge. Cytokine production analysis showed that chronic SJ infection reduced allergen-driven interleukin (IL)-4 and IL-5 production, but had no significant effect on IFN-gamma production. More importantly, we found that the adoptive transfer of dendritic cells (DCs) from SJ-infected mice dramatically decreased airway allergic inflammation in the recipients, which was associated with significant decrease of IL-4/IL-5 production and increase of IL-10 production. The results suggest that SJ infection may inhibit the development of allergy and that DCs may be involved in the process of helminth infection-mediated modulation of allergic inflammation.

Harnessing regulatory T cells to suppress asthma: from potential to therapy

Regulatory T cells (Tregs) play an essential role in maintaining the homeostatic balance of immune responses. Asthma is an inflammatory condition of the airways that is driven by dysregulated immune responses toward normally innocuous antigens. Individuals with asthma have fewer and less functional Tregs, which may lead to uncontrolled effector cell responses and promote proasthmatic responses of T helper type 2, T helper 17, natural killer T, antigen-presenting, and B cells. Tregs have the capacity to either directly or indirectly suppress these responses. Hence, the induced expansion of functional Tregs in predisposed or individuals with asthma is a potential approach for the prevention and treatment of asthma. Infection by a number of micro-organisms has been associated with reduced prevalence of asthma, and many infectious agents have been shown to induce Tregs and reduce allergic airways disease in mouse models. The translation of the regulatory and therapeutic properties of infectious agents for use in asthma requires the identification of key modulatory components and the development and trial of effective immunoregulatory therapies. Further translational and clinical research is required for the induction of Tregs to be harnessed as a therapeutic strategy for asthma.

The therapeutic potential of the filarial nematode-derived immunodulator, ES-62 in inflammatory disease

The dramatic recent rise in the incidence of allergic or autoimmune inflammatory diseases in the West has been proposed to reflect the lack of appropriate priming of the immune response by infectious agents such as parasitic worms during childhood. Consistent with this, there is increasing evidence supporting an inverse relationship between worm infection and T helper type 1/17 (Th1/17)-based inflammatory disorders such as rheumatoid arthritis, inflammatory bowel disease, type 1 diabetes and multiple sclerosis. Perhaps more surprisingly, given that such worms often induce strong Th2-type immune responses, there also appears to be an inverse correlation between parasite load and atopy. These findings therefore suggest that the co-evolution of helminths with hosts, which has resulted in the ability of worms to modulate inflammatory responses to promote parasite survival, has also produced the benefit of protecting the host from pathological lesions arising from aggressive proinflammatory responses to infection or, indeed, aberrant inflammatory responses underlying autoimmune and allergic disorders. By focusing upon the properties of the filarial nematode-derived immunomodulatory molecule, ES-62, in this review we shall discuss the potential of exploiting the immunomodulatory products of parasitic worms to identify and develop novel therapeutics for inflammation.

Maternal peanut exposure during pregnancy and lactation reduces peanut allergy risk in offspring

BACKGROUND

Maternal allergy is believed to be a risk factor for peanut allergy (PNA) in children. However, there is no direct evidence of maternal transmission of PNA susceptibility, and it is unknown whether maternal peanut exposure affects the development of PNA in offspring.

OBJECTIVE

To investigate the influence of maternal PNA on offspring reactions to the first peanut exposure, and whether maternal low-dose peanut exposure during pregnancy and lactation influences these reactions and peanut sensitization in a murine model.

METHODS

Five-week-old offspring of PNA C3H/HeJ mothers (PNA-Ms) were challenged intragastrically with peanut (first exposure), and reactions were determined. In a subset of the experiment, PNA-Ms were fed a low dose of peanut (PNA-M/PN) or not fed peanut (PNA-M/none) during pregnancy and lactation. Their 5-week-old offspring were challenged intragastrically with peanut, and reactions were determined. In another subset of the experiment, offspring of PNA-M/PN or PNA-M/none were sensitized with peanut intragastrically for 6 weeks, and serum peanut-specific antibodies were determined.

RESULTS

PNA-M offspring exhibited anaphylactic reactions at first exposure to peanut that were associated with peanut-specific IgG(1) levels and prevented by a platelet activation factor antagonist. In a subset experiment, PNA-M/PN offspring showed significantly reduced first-exposure peanut reactions, increased IgG(2a), and reduced mitogen-stimulated splenocyte cytokine production compared with PNA-M/none offspring. In an additional experiment, PNA-M/PN offspring showed reduction of peanut-specific IgE to active peanut sensitization.

CONCLUSION

We show for the first time maternal transmission of susceptibility to first-exposure peanut reactions and active peanut sensitization. Low-dose peanut exposure during pregnancy and lactation reduced this risk.

Trichuris suis ova therapy for allergic rhinitis: a randomized, double-blind, placebo-controlled clinical trial

BACKGROUND

Parasitic helminth infections can protect against allergic airway inflammation in experimental models and have been associated with a reduced risk of atopy and a reduced course of asthma in some observational studies. Although no clinical evidence exists to support the use of helminth therapy for allergic disease, the helminth Trichuris suis has demonstrated efficacy in treatment of inflammatory bowel disease.

OBJECTIVE

To determine efficacy of helminth therapy for allergic rhinitis.

METHODS

We conducted a double-blind, placebo-controlled, parallel group trial in which 100 subjects age 18 to 65 years with grass pollen-induced allergic rhinitis were randomly assigned to ingest a total of 8 doses with 2500 live T suis ova or placebo with an interval of 21 days. The primary outcome was a change in mean daily total symptom score for runny, itchy, sneezing nose (maximum change, 9.0) or in percentage of well days during the grass pollen season.

RESULTS

Treatment with T suis ova (N = 49) compared with placebo (N = 47) caused transient diarrhea peaking at day 41 in 33% of participants (placebo, 2%), and increased eosinophil counts (P < .001) and T suis-specific IgE (P < .05), IgG (P < .001), IgG(4) (P < .003), and IgA (P < .001), whereas there was no significant change in symptom scores (0.0; 95% CI, -0.5 to 0.4; P = .87), well days (3%; 95% CI, -9% to 14%; P = .63), total histamine (P = .44), grass-specific IgE (P = .76), or diameter of wheal reaction on skin prick testing with grass (P = .85) or 9 other allergens.

CONCLUSION

Repeated treatment with the helminth T suis induced a substantial clinical and immunologic response as evidence of infection, but had no therapeutic effect on allergic rhinitis.

Allergen-specific antibody and cytokine responses, mast cell reactivity and intestinal permeability upon oral challenge of sensitized and tolerized mice

BACKGROUND

Food allergy has reached an epidemic level in westernized countries and although central mechanisms have been described, the variability associated with genetic diversity underscores the still unresolved complexity of these disorders.

OBJECTIVE

To develop models of food allergy and oral tolerance, both strictly induced by the intestinal route, and to compare antigen-specific responses.

METHODS

BALB/c mice were mucosally sensitized to ovalbumin (OVA) in the presence of the mucosal adjuvant cholera toxin, or tolerized by intra-gastric administrations of OVA alone. Antibody titres and cytokines were determined by ELISA, and allergic status was determined through several physiologic parameters including decline in temperature, diarrhoea, mast cell degranulation and intestinal permeability.

RESULTS

OVA-specific antibodies (IgE, IgGs and IgA in serum and feces) were produced in sensitized mice exclusively. Upon intra-gastric challenge with OVA, sensitized mice developed anaphylactic reactions associated with a decline of temperature, diarrhoea, degranulation of mast cells, which were only moderately recruited in the small intestine, and increased intestinal permeability. Cytokines produced by immune cells from sensitized mice included T-helper type 2 cytokines (IL-5, IL-13), but also IL-10, IFN-gamma and IL-17. In contrast, all markers of allergy were totally absent in tolerized animals, and yet the latter were protected from subsequent sensitization, demonstrating that oral tolerance took place efficiently.

CONCLUSION

This work allows for the first time an appropriate comparison between sensitized and tolerized BALB/c mice towards OVA. It highlights important differences from other models of allergy, and thus questions some of the generally accepted notions of allergic reactions, such as the protective role of IFN-gamma, the importance of antigen-specific secretory IgA and the role of mucosal mast cells in intestinal anaphylaxis. In addition, it suggests that IL-17 might be an effector cytokine in food allergy. Finally, it demonstrates that intestinal permeability towards the allergen is increased during challenge.

Boosting the suppressive effects of Ascaris suum components in IFN-γ-deficient mice

High molecular weight components from Ascaris suum extract suppress ovalbumin-specific immunity in mice. In IFN-γ-deficient mice, ovalbumin-specific delayed-type hypersensitivity reactions are more strongly downregulated by these suppressive components. Here, the cellularity of the delayed-type hypersensitivity reaction in IFN-γ-deficient mice and the increased downregulation induced by Ascaris suum components were analyzed. IL-12p40-dependent neutrophilic influx was predominant. Suboptimal doses of the suppressive fraction from this nematode completely inhibited the hypersensitivity reaction, thus indicating intensification of the immunosuppression under conditions of intense recruitment of IFN-γ-independent neutrophils.

Mechanisms of food allergy

Allergy type sensitization occurring in the gut results from a break in oral tolerance, mostly occurring in early childhood. In these patients, a minute amount of the large load of potential food allergens not only will result in immunoglobulin E (IgE) type sensitization mostly, but also in food allergies resulting from other mechanisms including eosinophil-driven disease or resulting from T-cell-mediated inflammation. Symptoms elicited by subsequent exposure to foods in these patients will be mostly in relation to the mechanism of the disease. In this educational review series, we described three cases of food allergy, first, a child with typical IgE-mediated food allergy, second, a child with eosinophilic proctocolitis and in the third patient, we will address tolerance acquisition mechanisms. These cases are discussed with regards to their specific immune events.

Immunophysiology of experimental food allergy

Animal models of food allergy have been used to identify mechanisms involved in the development of sensitization to food proteins as well as immunologic mechanisms of adverse reactions to allergen reexposure. To counteract the normal tolerant responses to antigen generated in the gastrointestinal tract, investigators have used mucosal adjuvants or manipulated the mucosal barrier, taken advantage of endogenous adjuvanticity of some food allergens, or bypassed the oral route and sensitized through the skin. Site of antigen uptake in the gastrointestinal tract is a critical factor in both sensitization and anaphylaxis, and antigen uptake can be facilitated by immunoglobulin-E (IgE)-antigen complexes binding to CD23 on the epithelial cell surface. Studies on systemic anaphylaxis or local gastrointestinal manifestations of food allergy in mice have highlighted the contribution of IgE, mast cells, and pathogenic Th2 lymphocytes in experimental food allergy.

Helminths and the IBD hygiene hypothesis

Helminths are parasitic animals that have evolved over 100,000,000 years to live in the intestinal track or other locations of their hosts. Colonization of humans with these organisms was nearly universal until the early 20th century. More than 1,000,000,000 people in less developed countries carry helminths even today. Helminths must quell their host's immune system to successfully colonize. It is likely that helminths sense hostile changes in the local host environment and take action to control such responses. Inflammatory bowel disease (IBD) probably results from an inappropriately vigorous immune response to contents of the intestinal lumen. Environmental factors strongly affect the risk for IBD. People living in less developed countries are protected from IBD. The "IBD hygiene hypothesis" states that raising children in extremely hygienic environments negatively affects immune development, which predisposes them to immunological diseases like IBD later in life. Modern day absence of exposure to intestinal helminths appears to be an important environmental factor contributing to development of these illnesses. Helminths interact with both host innate and adoptive immunity to stimulate immune regulatory circuitry and to dampen effector pathways that drive aberrant inflammation. The first prototype worm therapies directed against immunological diseases are now under study in the United States and various countries around the world. Additional studies are in the advanced planning stage.

Parasitic nematode modulation of allergic disease

Incidence of allergic diseases such as asthma has increased at an alarming rate in Western countries in the past few decades. However, in parts of the world in which parasitic nematode infections are highly prevalent, allergy remains uncommon. Hence, it has been postulated that nematodes offer humans protection against this type of disease. This article reviews the evidence to support this idea, considering data from human studies and results from investigations into the protective effects of nematodes in animal models of allergic disease. The evidence strongly favors a protective role for nematodes; thus, the search is on to find the molecules involved, with a view toward using them for therapeutic purposes. The article also describes the nature and mode of action of recently characterized nematode-derived molecules with antiallergic properties and highlights their therapeutic efficacy in allergy models.

Mechanisms of action of probiotics

At birth, the newborn leaves the germ-free intrauterine environment and enters a highly contaminated extrauterine world, which requires potent host defenses to prevent disease. Intestinal defenses develop during gestation and have the capacity to respond but first must be exposed to colonizing bacteria. I review the importance of bacterial colonization for the appearance of normal mucosal immune function and the clinical consequences of inadequate colonization with regard to development of disease. For example, we now know that an imbalance in T-helper (Th) cells (e.g., Th2 levels greater than Th1 levels) can predispose to autoimmune disease and gut inflammation or disease, such as necrotizing enterocolitis. As we determine the role of bacterial colonization in the gut (bacterial-epithelial "cross talk"), we should have more-appropriate ways to modulate the gut immune responses-for example, by use of probiotics to prevent the expression of these gastrointestinal diseases.

Adjuvant Effect of Lemnan, Pectic Polysaccharide of Callus Culture ofLemna minorL. at Oral Administration

A pectic polysaccharide, lemnan LMC, was extracted from the callus of duckweed Lemna minor L. and was tested for adjuvant properties at oral administration with protein antigen. Mice were orally immunized thrice with weekly interval with free hen's egg lysozyme or lysozyme with LMC. Lemnan LMC was shown to increase delayed type hypersensitivity and serum antilysozyme IgG responses. LMC was established to increase levels of both serum IgG1 and IgG2a subclasses. The concentration of malondialdehyde and myeloperoxidase activity were found to be higher in the tissue samples obtained from small intestine of mice immunized with mixture of lysozyme/LMC than those immunized with lysozyme only. Thus, lemnan appeared to be useful as the adjuvant for oral immunization.

T(H)2 adjuvants: implications for food allergy

A persistent question for immunologists studying allergic disease has been to define the characteristics of a molecule that make it allergenic. There has been substantial progress elucidating mechanisms of innate priming of T(H)2 immunity in the past several years. These accumulating data demonstrate that T(H)2 immunity is actively induced by an array of molecules, many of which were first discovered in the context of antihelminthic immune responses. Similar intrinsic or associated activities are now known to account for the T(H)2 immunogenicity of some allergens, and may prove to play a role for many more. In this review, we discuss what has been discovered regarding molecules that induce innate immune activation and the pathways that promote T(H)2-polarized immune responses generally, and specifically what role these mechanisms may play in food allergy from models of food allergy and the study of T(H)2 gastrointestinal adjuvants.

Do you have a probiotic in your future?

The possibility of using microbes to maintain health, and to prevent or treat disease is a topic as old as microbiology. However, one factor impeding the introduction of effective probiotics has been our very limited understanding of the composition of the human microbiome, as well as the biological requirements for these organisms. With advances in understanding the microbiome and its metagenome in humans and other mammals, we now can build a more robust scientific basis to develop probiotic strategies. Increasing knowledge of intramicrobial competition and cooperation, as well as host-microbe cross-signaling, will facilitate design of new probiotics and the modeling of their deployment, leading to eventual clinical trials.

Therapeutic immunomodulators from nematode parasites

There has been an alarming increase in the incidence of autoimmune and allergic diseases in Western countries in the past few decades. However, in countries endemic for parasitic helminth infections, such diseases remain relatively rare. Hence, it has been hypothesised that helminths may protect against the development of autoimmunity and allergy. This article reviews the evidence supporting this idea with respect to helminths of the phylum Nematoda (nematodes), considering data from human studies and animal models of inflammatory disease. The nature and mode of action of nematode-derived molecules with immunomodulatory properties are considered, and their therapeutic efficacy in models of autoimmunity and allergy described. The recent and future use of nematodes and their products in treating human disease are also discussed.

Hookworm-induced persistent changes to the immunological environment of the lung

A number of important helminth parasites of humans have incorporated short-term residence in the lungs as an obligate phase of their life cycles. The significance of this transient pulmonary exposure to the infection and immunity is not clear. Employing a rodent model of infection with hookworm (Nippostrongylus brasiliensis), we characterized the long-term changes in the immunological status of the lungs induced by parasite infection. At 36 days after infection, alterations included a sustained increase in the transcription of both Th2 and Th1 cytokines as well as a significant increase in the number and frequency of alveolar macrophages displaying an alternatively activated phenotype. While N. brasiliensis did not induce alternate activation of lung macrophages in STAT6(-/-) animals, the parasite did induce a robust Th17 response in the pulmonary environment, suggesting that STAT6 signaling plays a role in modulating Th17 immunity and pathology in the lungs. In the context of the cellular and molecular changes induced by N. brasiliensis infection, there was a significant reduction in overall airway responsiveness and lung inflammation in response to allergen. In addition, the N. brasiliensis-altered pulmonary environment showed dramatic alterations in the nature and number of genes that were up- and downregulated in the lung in response to allergen challenge. The results demonstrate that even a transient exposure to a helminth parasite can effect significant and protracted changes in the immunological environment of the lung and that these complex molecular and cellular changes are likely to play a role in modulating a subsequent allergen-induced inflammatory response.

Coinfection with Heligmosomoides polygyrus fails to establish CD8+ T-cell immunity against Toxoplasma gondii

CD8+ T-cell immunity is important for long-term protection against Toxoplasma gondii infection. However, a Th1 cytokine environment, especially the presence of gamma interferon (IFN-), is essential for the development of primary CD8+ T-cell immunity against this obligate intracellular pathogen. Earlier studies from our laboratory have demonstrated that mice lacking optimal IFN- levels fail to develop robust CD8+ T-cell immunity against T. gondii. In the present study, induction of primary CD8+ T-cell immune response against T. gondii infection was evaluated in mice infected earlier with Heligmosomoides polygyrus, a gastrointestinal worm known to evoke a polarized Th2 response in the host. In the early stage of T. gondii infection, both CD4 and CD8+ T-cell responses against the parasite were suppressed in the dually infected mice. At the later stages, however, T. gondii-specific CD4+ T-cell immunity recovered, while CD8+ T-cell responses remained low. Unlike in mice infected with T. gondii alone, depletion of CD4+ T cells in the dually infected mice led to reactivation of chronic infection, leading to Toxoplasma-related encephalitis. Our observations strongly suggest that prior infection with a Th2 cytokine-polarizing pathogen can inhibit the development of CD8+ T-cell immune response against T. gondii, thus compromising long-term protection against a protozoan parasite. This is the first study to examine the generation of CD8+ T-cell immune response in a parasitic nematode and protozoan coinfection model that has important implications for infections where a CD8+ T-cell response is critical for host protection and reduced infection pathology.

Avirulant Salmonella typhimurium strains prevent food allergy in mice

Oral tolerance to foods can be regulated by microorganisms in the gut lumen. We hypothesized that pretreatment with avirulent Salmonella typhimurium strains could prevent food allergy in mice. Mice were administered S. typhimurium PhoPc (STPhoPc) or S. typhimurium AroA prior to oral sensitization to beta-lactoglobulin in the presence of cholera toxin. An oral antigen challenge after sensitization assessed antigen-induced anaphylaxis. Antigen-specific antibody titres were measured by enzyme-linked immunosorbent assay in the serum and enzyme-linked immunospot (ELISPOT) in the spleen, and cytokine-secreting cells were measured by ELISPOT in the Peyer's patches, lamina propria and epithelium cells. We showed first that S. typhimurium could up-regulate interleukin (IL)-12 and IL-10 secretion by gut T cells. Mice pretreated with STPhoPc had decreased anaphylaxis upon challenge, along with decreased immumoglobulin G1 (IgG1) and IgE antibody titres. Mice having received S. typhimurium AroA had partly decreased anaphylaxis as well as decreased serum IgG1 antibody titres in the serum, and increased serum IgA antibody titres. Antibody titres could be correlated with increased numbers of spleen and Peyer's patches antibody-producing cells. STPhoPc-treated mice showed significantly decreased anaphylaxis when compared with the control mice, while S. typhimurium AroA-pretreated mice had a similar immune response together with increased secretory IgA titres. Our experiments have proved a potential immunomodulatory protective effect by two avirulent S. typhimurium strains.

Infection with parasitic nematodes confounds vaccination efficacy

T helper (Th) cells produce signature cytokine patterns, induced largely by intracellular versus extracellular pathogens that provide the cellular and molecular basis for counter regulatory expression of protective immunity during concurrent infections. The production of IL-12 and IFN-gamma, for example, resulting from exposure to many bacterial, viral, and protozoan pathogens is responsible for Th1-derived protective responses that also can inhibit development of Th2-cells expressing IL-4-dependent immunity to extracellular helminth parasites and vice versa. In a similar manner, concurrent helminth infection alters optimal vaccine-induced responses in humans and livestock; however, the consequences of this condition have not been adequately studied especially in the context of a challenge infection following vaccination. Demands for new and effective vaccines to control chronic and emerging diseases, and the need for rapid deployment of vaccines for bio security concerns requires a systematic evaluation of confounding factors that limit vaccine efficacy. One common albeit overlooked confounder is the presence of gastrointestinal nematode parasites in populations of humans and livestock targeted for vaccination. This is particularly important in areas of the world were helminth infections are prevalent, but the interplay between parasites and emerging diseases that can be transmitted worldwide make this a global issue. In addition, it is not clear if the epidemic in allergic disease in industrialized countries substitutes for geohelminth infection to interfere with effective vaccination regimens. This presentation will focus on recent vaccination studies in mice experimentally infected with Heligmosomoides polygyrus to model the condition of gastrointestinal parasite infestation in mammalian populations targeted for vaccination. In addition, a large animal vaccination and challenge model against Mycoplasma hyopneumonia in swine exposed to Ascaris suum will provide a specific example of the need for further work in this area, and for controlled field studies to assess the impact of other similar scenarios.

Helminths, allergic disorders and IgE-mediated immune responses: where do we stand?

Th2 responses induced by allergens or helminths share many common features. However, allergen-specific IgE can almost always be detected in atopic patients, whereas helminth-specific IgE is often not detectable and anaphylaxis often occurs in atopy but not helminth infections. This may be due to T regulatory responses induced by the helminths or the lack of helminth-specific IgE. Alternatively non-specific IgE induced by the helminths may protect from mast cell or basophil degranulation by saturating IgE binding sites. Both of these mechanisms have been implicated to be involved in helminth-induced protection from allergic responses. An article in the current issue of the European Journal of Immunology describes the generation of an anti-Nippostrongylus brasiliensis-specific IgE antibody which was used to identify a novel N. brasiliensis antigen (Nb-Ag1). The authors demonstrated that Nb-Ag1 specific IgE could only be detected for a short period of time during infection, and that these levels were sufficient to prime mast cells thereby leading to active cutaneous anaphylaxis after the application of Nb-Ag1. This is the first report clearly showing that a low level of helminth-specific IgE, transiently produced, is able to induce mast cell degranulation in the presence of large amounts of polyclonal IgE.