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

Impairment of dendritic cell function by excretory-secretory products: A potential mechanism for nematode-induced immunosuppression

To determine whether helminth-derived products modulate dendritic cell (DC) function, we investigated the effects of excretory-secretory products (ES) and adult worm homogenate (AWH) derived from the gastrointestinal nematode Heligmosomoides polygyrus (Hp) on murine bone marrow-derived DC (BMDC). Compared to the TLR9 ligand CpG, Hp-derived products alone failed to induce DC activation. ES, but not AWH, inhibited BMDC cytokine and chemokine production and co-stimulatory molecule expression (CD40, CD86 and MHC class II) induced by TLR ligation. TLR ligand-independent, PMA-induced DC activation was unaffected by ES. Recipients of ES-treated BMDC pulsed with OVA had suppressed Ab responses in vivo, irrespective of the Th1 or Th2 isotype affiliation, compared to recipients of control OVA-pulsed BMDC. Importantly, suppression occurred even in the presence of the potent type 1 adjuvant CpG. In contrast to untreated OVA-pulsed BMDC, ES-treated BMDC pulsed with OVA had reduced co-stimulatory molecule and cytokine expression. CD4(+)CD25(+)Foxp3(-) T cells, which secreted high IL-10 levels, were generated in co-cultures of OT-II OVA-specific TCR-transgenic CD4(+) T cells and ES-treated BMDC. These IL-10-secreting T cells suppressed effector CD4(+) T cell proliferation and IFN-gamma production, the latter effect mediated by an IL-10-dependent mechanism. Together, these results demonstrate that nematode ES impaired DC function and suppressed both Th1 and Th2 adaptive immune responses possibly by inducing regulatory T cells.

Induction of tolerance after establishment of peanut allergy by the food allergy herbal formula-2 is associated with up-regulation of interferon-?

BACKGROUND

Peanut (PN)-anaphylaxis is potentially life threatening. We previously reported that a Chinese herbal medicine preparation, food allergy herbal formula-2 (FAHF-2), prevented peanut allergy (PNA) in mice when administered during sensitization.

OBJECTIVE

To investigate whether FAHF-2 also can prevent anaphylactic reactions when administered to mice with established PNA and, if so, whether protection would persist after cessation of therapy.

METHODS

C3H/HeJ mice sensitized and boosted over 8 weeks with a standard protocol known to establish PN hypersensitivity received seven weeks of FAHF-2 treatment or water as a sham treatment. Mice were subsequently challenged with PN at week 14 (1-day post-therapy) and week 18 (4-week post-therapy) to evaluate the efficacy and persistence of FAHF-2 treatment by assessing anaphylactic scores, core body temperatures and plasma histamine levels. Serum PN-specific antibody levels and cytokine profiles from splenocytes and mesenteric lymph node (MLN) cells were also determined.

RESULTS

All sham-treated mice challenged at weeks 14 and 18 showed anaphylactic symptoms. In contrast, FAHF-2-treated mice showed no sign of anaphylactic reactions. PN-specific IgE levels in FAHF-2-treated mice also were reduced whereas IgG2a levels were increased. Furthermore, MLN cells from FAHF-2-treated mice produced markedly less IL-4 and IL-5, but more IFN-gamma, and contained increased numbers of IFN-gamma-producing CD8+ cells as compared with sham-treated mice.

CONCLUSION

FAHF-2 treatment established PN tolerance in this model, which persisted for at least 4-week post-treatment. This result was associated with modulation of intestinal T helper type 1 cell (Th1) and Th2 cytokine production, and with increased numbers of mesenteric IFN-gamma-producing CD8+ cells.

Modulation of anaphylaxis by helminth-derived products in animal models

Helminths have a profound immunomodulatory effect upon the inductive and effector phases of inflammatory responses, including allergy. Several animal models of anaphylaxis have been established to investigate the mechanisms by which helminth infections or helminth-derived products interfere with the onset of allergic reactions. The focus of our studies was the immunosuppression induced by the intestinal roundworm Ascaris suum in the production of anaphylactic antibodies and the development of lung eosinophilic inflammation and hyperreactivity to its own allergens and to unrelated antigens. Thus, we identified a single protein affinity purified from the A. suum body extract, named PAS-1, which maintains all its immunosuppressive properties and promotes a significant increase in interleukin-10 production, an essential cytokine for the effectiveness of the suppressive mechanism. In addition, PAS-1 primes for regulatory T cells, which also mediate this mechanism. Therefore, this helminth molecule may be a promising target for therapeutic applications in allergic disorders.

Immunology of anaphylaxis: lessons from murine models

The use of animal models is increasing, and mice are suitable animals to use in exploring systemic anaphylaxis based on the similarity between human and mouse immune systems. Two anaphylaxis pathways have been characterized in mice, which may help in understanding some of the discrepancies found in humans. In addition, cytokine studies are raising new concepts that may put together some of the puzzling mechanisms described in this disease. Finally, the study of the mechanisms that parasitic infections use to evade the human immune system and the scene in which a parasite induces clinical anaphylaxis are opening new insights in the immunology pathways and new strategies to fight against this exclusive disease.

Chronic helminth infections induce immunomodulation: consequences and mechanisms

Worldwide, more than a billion people are infected with helminths. These worm infections generally do not lead to mortality, however, they are chronic in nature and can lead to considerable morbidity. Immunologically these infections are interesting; chronic helminth infections are characterized by skewing towards a T helper 2 type response as well as regulatory responses. The regulatory network is associated with chronic helminth infections and is thought to prevent strong immune responses against parasitic worms, allowing their long-term survival and restricting pathology. This regulatory network is thought to also temper responses to non-helminth antigens, like allergens or self-antigens, possibly leading to lower prevalence of allergies and autoimmune diseases in subjects that are chronically infected with helminths. This raises the interesting idea that helminths may bear molecules that have potential therapeutic action against allergies and possibly other inflammatory diseases. However, on the other side of the coin, this would predict that helminth infected subjects might not respond strongly to third party antigens like vaccines. This is an important issue, since most vaccines that are being developed against diseases such as HIV, tuberculosis or malaria will be introduced in areas where helminth infections are highly prevalent. Moreover, these vaccines are proving difficult to develop and are often weak, thus any confounder that would affect their efficacy needs to be taken into consideration. Helminth derived molecules have been identified that induce T helper 2 and regulatory responses via modulation of dendritic cells and some appear to do so via Toll like receptor (TLR) signaling. New insights into these pathways could be useful to antagonize suppression and hence boost vaccine efficacy or to optimize suppression induced by helminth derived molecules and control inflammatory diseases.

Suppression of TH2-type allergic reactions by helminth infection

There is no immunological mechanism to adequately explain the sudden epidemic in allergies noted in the last 30 years in developed countries. The reduction in the development of allergic disorders observed in individuals infected with parasitic helminths, however, supports a possible role for worms in suppressing allergies. Helminths regulate the immunity of the host to ensure a mutually beneficial environment for the survival of both the parasite and the host. This interplay between helminths and allergic responses raises fundamental questions in immunobiology. Harnessing current mechanistic studies for translational research into helminth infections and atopy might have potential for the identification of novel biomarkers, and even therapeutics, in allergic diseases.

Helminth infection enhances disease in a murine TH2 model of colitis

BACKGROUND & AIMS

There is convincing evidence from animal and human studies that infection with parasitic helminths can alleviate the histopathology and symptoms of colitis. Here the ability of the rat tapeworm Hymenolepis diminuta to affect the course of oxazolone-induced colitis (a TH2 model) was assessed.

METHODS

Mice were infected with H diminuta and 8 days later they received oxazolone (3 mg in 50% EtOH, intrarectal). On autopsy (3 or 7 days postoxazolone), disease severity was assessed by macroscopic clinical scores, histologic damage scores, myeloperoxidase and eosinophil peroxidase activity, and cytokine synthesis.

RESULTS

As gauged by all markers of gut function, infection with H diminuta caused a significant exacerbation of oxazolone-induced colitis. Indeed, while mice receiving oxazolone only began to recover approximately 3-4 days posttreatment, the cotreated group continued to deteriorate. Helminth infection, independent of oxazolone administration, enhanced IL-4, IL-5, IL-10, and IL-13 production from in vitro stimulated immune cells and evoked increases in colonic eosinophil peroxidase of cotreated mice. Finally, while knockout of natural killer (NK) and NK-T cells by administration of a neutralizing NK1.1 antibody reduced the inflammation in oxazolone and oxazolone + H diminuta-treated animals, mice in the latter group still displayed significant colitis.

CONCLUSIONS

We have shown that H diminuta infection is beneficial in other models of colitis. The current data is presented as a caveat to the position that parasitic helminths in general can be considered as a therapy for heterogeneous inflammatory disorders without careful analysis of the immunologic basis of the condition.

Chronic helminth infections modulate allergen-specific immune responses: Protection against development of allergic disorders?

Inflammatory diseases are on the rise in westernized countries, but also in urbanized areas of developing countries. A number of studies have now demonstrated a negative association between helminth infections and inflammatory diseases, such as allergy, suggesting a potential role for helminth-induced immune responses. However, this is not the case for all studies. In this review both supporting and opposing literature on the role of helminth infections, particularly in allergy, are discussed. Furthermore, the concept is put forward that chronic helminth infections, but not acute infections, may be associated with the expression of regulatory networks necessary for downmodulating allergic immune responses to harmless antigens. Lastly, different components of helminth-induced regulatory networks are detailed, such as the role of regulatory T and B cells, modulation of dendritic cells, the presence of suppressory alternatively activated macrophages, and their individual contributions to protection against allergic diseases. Advantage should be taken from this knowledge to identify and select individual helminth-derived molecules that may harbor therapeutic potential against inflammatory diseases.

The importance of dietary control in the development of a peanut allergy model in Brown Norway rats

This report describes the further development of a peanut allergy model in Brown Norway (BN) rats and in particular the importance of allergen-free breeding of the laboratory animals for the allergen to be used. For this purpose BN rats were bred for 3 generations on soy- and peanut-free feed since it is known that the legumes peanut and soy are cross-reactive. In addition, the effect of cholera toxin (CT), an oral adjuvant often used to increase the sensitivity of food allergy models, was investigated in the BN rat model. BN rats that were bred on both soy- and peanut-free feed could be sensitized orally to peanut (all exposed rats developed peanut-specific IgE, IgG2a and IgG1) and the adjuvant CT could only enhance this sensitization to a limited extent. We also found different protein recognition patterns against purified peanut allergens (Ara h1, Ara h2 and Ara h3) between intraperitoneally (i.p.) and orally sensitized BN rats. Orally sensitized rats recognized all tested allergens whereas i.p. sensitized rats only recognized Ara h1 and Ara h2. Our conclusion is that a model for food allergy should preferably be (A) oral and (B) if possible without the use of adjuvantia. Our model in BN rats unites these preferred characteristics. In addition, we show the importance of dietary control when conducting oral sensitization studies. Special attention must be paid to unscheduled dietary pre-exposure of the animals to the protein under investigation to obtain optimal oral sensitization.

Immune privilege in the gut: the establishment and maintenance of non-responsiveness to dietary antigens and commensal flora

Immune privilege in the gut is the result of a complex interplay between the gut microbiome, gut luminal antigens, and the intestinal epithelial barrier. Composed of both physical and immunochemical components, the intestinal barrier secretes immunoregulatory mediators that promote the generation of tolerogenic antigen-presenting cells, phagocytic innate immune cells characterized by 'inflammatory anergy', and regulatory cells of the adaptive immune system. Innate immune cells mediate controlled transepithelial transport of luminal antigens as far as the mesenteric lymph nodes, where the intestinal and peripheral immune systems intersect. This promotes the generation of adaptive regulatory lymphocytes that actively suppress effector cell responses against gut luminal antigens and flora. The net result is the generation of tolerance to dietary antigens and the maintenance of gut homeostasis. Dysregulation of this complex immunoregulatory network leads to diseases such as food allergy and inflammatory bowel disease. Future therapies for these diseases will likely involve the functional restoration of the barrier and regulatory cell functions at the epithelial/luminal interface.

Immunosuppressive components ofAscaris suumdown-regulate expression of costimulatory molecules and function of antigen-presenting cellsvia an IL-10-mediated mechanism

High-molecular-weight components (PI) of Ascaris suum suppress both cell-mediated and humoral responses against ovalbumin (OVA) via an IL-4/IL-10-dependent mechanism. The aim of this work was to investigate the effect of PI on the ability of APC to activate T cells and the role of IL-10 in this process. Flow cytometry analyses of MHC class II, CD80, CD86 and CD40 molecules on LN cells from mice immunized with OVA or OVA+PI showed that PI inhibits expression of these molecules on unfractionated cells and on purified CD11c(+) cells. A low proliferative response was obtained when OVA-specific TCR-Tg T cells were incubated with CD11c(+) cells from OVA+PI-immunized mice pulsed with OVA, when compared to those incubated with cells from OVA-immunized mice. Similar results were obtained using as APC CD11c(+) cells from OVA-immunized mice pulsed with OVA+PI, which also expressed less of the four markers. The inhibitory effect of PI on both the expression of costimulatory molecules and the induction of T cell proliferation was abolished in IL-10-deficient mice. Our data indicate that the potent immunosuppressive effect of A. suum extract components on the host immune system is primarily related to their property of down-regulating the Ag-presenting ability of DC via an IL-10-mediated mechanism.

Helminth-derived products inhibit the development of allergic responses in mice

RATIONALE

Epidemiological studies suggest that infections with helminths protect from the development of asthma. Supporting this view is our published finding that infection with Nippostrongylus brasiliensis decreased ovalbumin-induced Th2 responses in the lung of mice.

OBJECTIVES

To evaluate if N. brasiliensis excretory-secretory products also prevent the development of asthma.

METHODS

Mice were immunized with ovalbumin/alum intraperitoneally in the absence or presence of helminthic products and then challenged intranasally with ovalbumin. Six days later, we analyzed if the mice developed Th2 responses in the lung.

MAIN RESULTS

The application of the helminthic products together with ovalbumin/alum during the sensitization period totally inhibited the development of eosinophilia and goblet cell metaplasia in the airways and also strongly reduced the development of airway hyperreactivity. Allergen-specific IgG1 and IgE serum levels were also strongly reduced. These findings correlated with decreased levels of IL-4 and IL-5 in the airways in product-treated animals. The suppressive effects on the development of allergic responses were independent of the presence of Toll-like receptors 2 and 4, IFN-gamma, and most important, IL-10. Interestingly, suppression was still observed when the helminthic products were heated or treated with proteinase K. Paradoxically, we found that strong helminth product-specific Th2 responses were induced in parallel with the inhibition of ovalbumin-specific responses.

CONCLUSION

Our results suggest that helminths suppress the development of asthma by secreting substances that modulate allergic responses without affecting the generation of helminth-specific Th2 immunity. The identification of these products may lead to the design of novel therapeutic intervention strategies for the treatment of asthma.

Helminths and mucosal immune modulation

Geographic and ethnic variations in ulcerative colitis and Crohn's disease frequency suggest that environmental factors affect disease risk. Prevention of parasitic worms (helminths) through improved hygiene may be one factor leading to the increased disease prevalence. Helminths alter host mucosal and systemic immunity. Animals exposed to helminths are protected from experimental colitis and other immunological diseases, and helminthic colonization can be used to treat ongoing murine and human disease. Helminths induce mucosal T cells to make Th2 and regulatory cytokines. Helminth-induced mucosal IL4, TGFbeta, and IL10 likely are part of the protective process. Helminths affect pathways of innate immunity like TLR4 expression and function. Worms also induce various regulatory-type T-cell subsets in the gut that limit effector T-cell growth and function. These effects of once ever-present helminths may have protected people from immune-mediated illnesses like inflammatory bowel disease.

Screening for immunomodulatory proteins of the intestinal parasitic nematode Heligmosomoides polygyrus

Parasitic nematodes are constantly exposed to the immune effector mechanisms of their hosts. One strategy of the worms to cope with these defence reactions is the secretion of modulatory proteins that down-regulate cell-mediated immune responses. We analysed the proliferation of mesenteric lymph node cells of mice infected with Heligmosomoides polygyrus and showed that cellular proliferation was strongly suppressed in the chronic phase of infection. To identify proteins of H. polygyrus that are involved in parasite-induced immunomodulation, worm extract and culture supernatant of adult H. polygyrus were fractionated by gel chromatography and activity of each fraction was determined. One of the fractions (fraction 9) of worm extract as well as worm secretory products inhibited the antigen-specific cellular proliferation by about 40%. This reduced cellular reactivity coincided with a down-regulation of inducible nitric oxide production of mouse macrophages by 57%. Furthermore, fraction 9 contained antigens that were recognized by IgE antibodies of H. polygyrus-infected mice and induced degranulation of an IgE-sensitized basophil cell line. Single proteins of fraction 9 were analysed by mass spectrometry. These data suggest that antigens that are recognised by IgE antibodies might play an important role in immunomodulation exerted by nematode infections.

Induction of CD8+ regulatory T cells in the intestine by Heligmosomoides polygyrus infection

This study determined whether Heligmosomoides polygyrus induces intestinal regulatory T cells. Splenic T cells proliferate strongly when cultured with anti-CD3 and antigen-presenting cells (APC). Lamina propria T cells from mice with H. polygyrus mixed with normal splenic T cells from uninfected mice inhibited proliferation over 90%. Lamina propria T cells from mice without H. polygyrus only modestly affected T cell proliferation. The worm-induced regulatory T cell was CD8+ and required splenic T cell contact to inhibit proliferation. The regulation also was IL-10 independent, but TAP-dependent, suggesting that it requires major histocompatibility complex (MHC) class I interaction. Additional studies employed mice with transgenic T cells that did not express functional TGF-beta receptors. The lamina propria T regulator inhibited proliferation of these transgenic T cells nearly 100%, suggesting that TGF-beta signaling via the T cell was not required. CD8+ T cells were needed for worms to reverse piroxicam-induced colitis in Rag mice (T and B cell deficient) reconstituted with IL-10-/- T cells. Thus H. polygyrus induces a regulatory CD8+ lamina propria T cell that inhibits T cell proliferation and that appears to have a role in control of colitis.

Atopische Dermatitis: Hygiene-Hypothese

The prevalence of atopic diseases has steadily increased over the past decades. While genetic predisposition remains an important risk factor, environmental conditions appear to be additional relevant trigger factors, leading to the development of the "hygiene hypothesis". Current data indicates that atopic respiratory diseases seem to occur less frequently following helminth infections. This effect may be due to the induction of anti-inflammatory cytokines during the helminth infection. In contrast, atopic dermatitis seems to represent a separate entity influenced by more than "allergic sensitization". Recent data demonstrate a reduced risk for the development of atopic dermatitis following helminth infections. Further studies are needed to more closely examine the connections between helminth infections and this chronic skin disease, as well as to identify immunologic pathways.

Intestinal and pulmonary mucosal T cells: local heroes fight to maintain the status quo

Mucosal immunity in the lung and intestine is controlled by complex multifaceted systems. While mucosal T cells are essential for protection against invading pathogens owing to their proximity to the outside world, powerful systems must also be in place to harness ongoing inflammatory processes. In each site, distinct anatomical structures play key roles in mounting and executing both protective and deleterious mucosal T cell responses. Although analogies can be drawn regarding the immune systems of these two organs, there are substantial dissimilarities necessitated by unique physiologic constraints. Here, we discuss how T cell activation and effector function are generated in the mucosae.

Characterisation of the oral adjuvant effect of lemnan, a pectic polysaccharide of Lemna minor L

Lemnan LM, apiogalacturonanic pectin of duckweed Lemna minor L. was tested for adjuvant properties following oral administration with protein antigen. Male Swiss mice were orally immunized thrice with weekly intervals with free OVA or OVA with lemnan (LM). Lemnan LM was shown to increase delayed type hypersensitivity (DTH) and serum anti OVA IgG responses. LM was established to increase levels of both serum IgG1 and IgG2a subclasses, intestinal IgA and failed to elevate levels of serum IgE. Lemnan was found to increase the adhesion of macrophages and to enhance the generation of oxygen radicals by macrophages in response to phorbol 12-myristate 13-acetate. Serum OVA levels were four-fold higher in mice immunized with the mixture of OVA and LM in comparison with those in mice immunized with OVA only. Thus, substantial systemic and local mucosal immune responses were attained by oral immunization with the mixture of OVA and lemnan. Lemnan appeared to elicit adjuvant activity via induction of both Th1- and Th2-type responses. The immunopotentiating effect of lemnan may result from enhanced antigen ingestion and stimulation of macrophage activity.

Toll-like receptor function and signaling

Mammals sense pathogen invasion through pattern-recognition receptors. A group of transmembrane proteins, Toll-like receptors (TLRs), play critical roles as pattern-recognition receptors. They are mainly expressed on antigen-presenting cells, such as macrophages or dendritic cells, and their signaling activates antigen-presenting cells to provoke innate immunity and to establish adaptive immunity. Each TLR has common effects, such as inflammatory cytokine induction or upregulation of costimulatory molecule expression, but also has its specific function, exemplified by type I IFN-inducing ability. These immunoadjuvant effects are not only critical in antimicrobial immunity but are also involved in manifestations of autoimmunity. Furthermore, some TLR agonists are now promising therapeutic tools for various immune disorders, including allergy. Therefore understanding molecular mechanisms on TLRs should be quite useful in the development of therapeutic maneuvers against allergy and autoimmune diseases.

Exposure to the fish parasite Anisakis causes allergic airway hyperreactivity and dermatitis

BACKGROUND

Several case reports show allergy and anaphylactic reactions to the fish parasite Anisakis in the domestic and occupational setting. Further research is needed on the prevalence and mechanisms of disease.

OBJECTIVE

To determine the prevalence of Anisakis sensitization and related symptoms among workers in 2 fish-processing factories, and to use gene-deficient mice to determine the working mechanisms of Anisakis allergy.

METHODS

A modified version of the European Community Respiratory Health Survey was used to interview 578 South African fish-processing workers. Sensitization to Anisakis, seafood, and common aeroallergens was determined by skin prick test. Lung function was measured by spirometry and methacholine challenge. Serum eicosapentaenoic acid levels were used as an index of seafood consumption. Sensitized wild-type, IL-4, or IL-4 receptor alpha-deficient mice were challenged orally with Anisakis extract. Allergic reactions, lung pathology, antibodies, cytokines, mast cell proteases, and histamine were evaluated.

RESULTS

The prevalence of sensitization to Anisakis was higher than the prevalence of sensitization to fish (8% vs 6%). Anisakis-specific IgE reactivity was associated with bronchial hyperreactivity and dermatitis, and significantly increased with fish consumption. In mice, Anisakis infective larvae (L3) induced a striking T(H)2/type 2 response. Food-allergic-type reactions induced by oral challenge with Anisakis extract were absent in IL-4 receptor alpha knockout mice.

CONCLUSION

Anisakis sensitization in fish-processing workers is associated with allergic symptoms and correlates with high levels of fish consumption. Anisakis proteins induce allergic reactions in sensitized mice by IL-4/IL-13-mediated mechanisms.

CLINICAL IMPLICATIONS

Anisakis allergy should be considered in fish-processing workers with allergic symptoms.

The role of helminth infections in protection from atopic disorders

PURPOSE OF REVIEW

The observation that allergies are less prevalent in developing countries, especially in rural areas, has stimulated considerable research to identify environmental factors associated with protection against allergic disorders. Here, we review recent studies conducted in developing countries.

RECENT FINDINGS

Epidemiological studies conducted in South America, Asia and Africa have attempted to identify factors associated with differences in prevalence of atopy, asthma and atopic dermatitis. Particular attention is given to the complex relationship between helminth infections and allergies. In answer to the question of whether helminth infections are associated with protection against allergic disorders, conflicting data have been generated. In addition to epidemiological studies, animal models have been utilized to gain insight into the immunological mechanisms involved in the interaction between helminth infections and allergies. These animal studies are discussed. The possible explanations for discrepancies found within both human and murine studies have been considered, highlighting the need for further research.

SUMMARY

An in-depth understanding of the relevant protective mechanisms against allergic disorders will open the possibility of developing novel therapeutics to prevent the allergic march worldwide.

Oral and nasal sensitization promote distinct immune responses and lung reactivity in a mouse model of peanut allergy

Despite structural and functional differences between the initial sites of contact with allergens in the gastrointestinal and nasal tracts, few animal models have examined the influence of the mucosal routes of sensitization on host reactivity to food or environmental antigens. We compared the oral and nasal routes of peanut sensitization for the development of a mouse model of allergy. Mice were sensitized by administration of peanut proteins in the presence of cholera toxin as adjuvant. Antibody and cytokine responses were characterized, as well as airway reactivity to nasal challenge with peanut or unrelated antigens. Oral sensitization promoted higher levels of IgE, but lower IgG responses, than nasal sensitization. Both orally and nasally sensitized mice experienced airway hyperreactivity on nasal peanut challenge. The peanut challenge also induced lung eosinophilia and type 2 helper T-cell-type cytokines in orally sensitized mice. In contrast, peanut challenge in nasally sensitized mice promoted neutrophilia and higher levels of lung MAC-1(+) I-A(b low) cells and inflammatory cytokines. In addition, nasal but not oral, sensitization promoted lung inflammatory responses to unrelated antigens. In summary, both oral and nasal peanut sensitization prime mice for airway hyperreactivity, but the initial mucosal route of sensitization influences the nature of lung inflammatory responses to peanut and unrelated allergens.

Toxocara infection seroprevalence and its relationship with atopic features in a general adult population

BACKGROUND

The relationship of helminth infection with atopy is controversial. Toxocariasis is the most common helminth infection in industrialized countries. The study aimed to investigate the association between Toxocara exposure and atopic features.

METHODS

The study is based on a cross-sectional survey of 463 subjects, randomly selected (stratified by decades of age) from a general adult population. Toxocara exposure was defined by the presence of serum Toxocara antibodies. Main outcome measures included total serum IgE levels, skin prick tests (SPT) to a panel of 13 relevant aeroallergens, specific IgE to aeroallergens (Phadiatop test), and respiratory symptoms evaluated by means of a questionnaire.

RESULTS

A total of 134 subjects (weighted proportion 28.6%, 95% CI 26.5-30.7%) showed Toxocara exposure. Pet ownership, rural habitat, farming, and low educational level were associated with Toxocara exposure. Toxocara exposure was associated with both positive SPT (particularly to mites) and positive specific IgE (Phadiatop test) after adjusting for potential confounders. The effect of Toxocara exposure on total serum IgE levels and blood eosinophil count was different in SPT-positive subjects and SPT-negative individuals. In SPT-negative individuals, Toxocara exposure was associated with an increase in both serum IgE levels and eosinophil counts, whereas an opposite trend was observed in SPT-positive individuals. Toxocara exposure was not associated with respiratory symptoms.

CONCLUSIONS

In this adult population, Toxocara exposure is associated with allergic sensitization, particularly to mites. There is evidence of an intriguing interaction between Toxocara exposure and allergic sensitization for both total serum IgE levels and blood eosinophil counts.

Helminth-modified pulmonary immune response protects mice from allergen-induced airway hyperresponsiveness

It has been shown that the presence of certain helminth infections in humans, including schistosomes, may reduce the propensity to develop allergies in infected populations. Using a mouse model of schistosome worm vs worm + egg infection, our objective was to dissect the mechanisms underlying the inverse relationship between helminth infections and allergies. We have demonstrated that conventional Schistosoma mansoni egg-laying male and female worm infection of mice exacerbates airway hyperresponsiveness. In contrast, mice infected with only schistosome male worms, precluding egg production, were protected from OVA-induced airway hyperresponsiveness. Worm-infected mice developed a novel modified type 2 cytokine response in the lungs, with elevated allergen-specific IL-4 and IL-13 but reduced IL-5, and increased IL-10. Although schistosome worm-only infection is a laboratory model, these data illustrate the complexity of schistosome modulation of host immunity by the worm vs egg stages of this helminth, with the potential of infections to aggravate or suppress allergic pulmonary inflammation. Thus, infection of mice with a human parasitic worm can result in reduced airway inflammation in response to a model allergen.

Anisakis simplex allergy: a murine model of anaphylaxis induced by parasitic proteins displays a mixed Th1/Th2 pattern

The study of the singular hypersensitivity reactions to Anisakis simplex (A.s) proteins, may help us to undestand many of the unknown immune interactions between helmiths infections and allergy. We have developed a murine model of allergy to A. simplex, that mimics human A. simplex allergy to study the specific aspects of anaphylaxis induced by parasites. Male C3H/HeJ mice were intraperitoneally sensitized to A. simplex. Mice were then intravenous or orally challenged with A. simplex. Antigen-specific immunoglobulins, polyclonal IgE, anaphylactic symptoms, plasma histamine levels and cytokine profiles were determined. Comparative IgE immunoblot analyses were also performed. Specific IgE, IgG(1) and IgG(2a) were detected in sensitized mice since week 3. Polyclonal IgE raised and peaked with different kinetics. Intravenous A. simplex challenge produced anaphylaxis in mice, accompanied by plasma histamine release. Oral A. simplex challenge in similarly sensitized mice did not caused symptoms nor histamine release. Numerous A. simplex allergens were recognized by sensitized mouse sera, some of them similar to human serum. The A. simplex stimulated splenocytes released IL-10, IFN-gamma, IL-4, IL-13 and IL-5. We describe a new animal model of anaphylaxis. It exhibits characteristics of type I hypersensitivity reactions to Anisakis simplex similar to those observed in allergic humans. Different responses to i.v. or oral A. simplex challenges emerged, which did not reflect a window tolerization period. The cytokine profile developed (mixed Th(1)/Th(2) pattern) differed from the observed in classical models of anaphylaxis or allergy to food antigens. This model may permit to investigate the peculiar allergic reactions to parasitic proteins.

Suppression of allergic airway inflammation by helminth-induced regulatory T cells

Allergic diseases mediated by T helper type (Th) 2 cell immune responses are rising dramatically in most developed countries. Exaggerated Th2 cell reactivity could result, for example, from diminished exposure to Th1 cell–inducing microbial infections. Epidemiological studies, however, indicate that Th2 cell–stimulating helminth parasites may also counteract allergies, possibly by generating regulatory T cells which suppress both Th1 and Th2 arms of immunity. We therefore tested the ability of the Th2 cell–inducing gastrointestinal nematode Heligmosomoides polygyrus to influence experimentally induced airway allergy to ovalbumin and the house dust mite allergen Der p 1. Inflammatory cell infiltrates in the lung were suppressed in infected mice compared with uninfected controls. Suppression was reversed in mice treated with antibodies to CD25. Most notably, suppression was transferable with mesenteric lymph node cells (MLNC) from infected animals to uninfected sensitized mice, demonstrating that the effector phase was targeted. MLNC from infected animals contained elevated numbers of CD4⁺CD25⁺Foxp3⁺ T cells, higher TGF-β expression, and produced strong interleukin (IL)-10 responses to parasite antigen. However, MLNC from IL-10–deficient animals transferred suppression to sensitized hosts, indicating that IL-10 is not the primary modulator of the allergic response. Suppression was associated with CD4⁺ T cells from MLNC, with the CD4⁺CD25⁺ marker defining the most active population. These data support the contention that helminth infections elicit a regulatory T cell population able to down-regulate allergen induced lung pathology in vivo.

Cytokine and chemokine responses in patients co-infected with Entamoeba histolytica/dispar, Necator americanus and Mansonella perstans and changes after anti-parasite treatment

This study examined the impact of concurrent parasite infections (amoebiasis, filariasis, necatoriasis) and the effect of anti-parasite treatment on cytokine and chemokine responses in singly and poly-parasitized patients. Cellular reactivity and parasite-specific Th1- and Th2-type cytokine and chemokine profiles were investigated before and six weeks after treatment. In those patients infected with three parasite species, cellular secretion of interleukin 5 (IL-5) and IL-12p40 by PBMC was strongly diminished (p<0.005) but IL-10 was elevated in parasite-infected patients (p<0.0001) in response to protozoa- and helminth-specific as well as bacteria-specific antigens. Macrophage inflammatory chemokines (MIP-1alpha/CCL3 and MIP-1beta/CCL4), macrophage-derived chemokine (MDC/CCL22) and neutrophil activating chemokine (IL-8/CXCL8) were produced by PBMC in similar amounts in endemic controls and singly and poly-parasitized patients, but thymus and activation-regulated chemokine (TARC/CCL17) was produced the highest by PBMC from patients with triple parasite infections (p<0.0001). Following anti-parasite therapy, secretion of IL-12p40 and IL-5 augmented significantly in treated patients while IL-10, MDC, MIP-1alpha, TARC and IL-8 substantially diminished (all p<10(-5)) when their PBMC were activated with parasite- and bacteria-specific antigens. In summary, PBMC from poly-parasitized patients responded to protozoa- and helminth-specific antigens with a compromised IL-5 and IL-12p40 but high IL-10 and a substantial chemokine release. Chemokines may attract and activate effector cells in peri-parasitic tissues to limit parasite proliferation and dissemination, while depressed IL-5 and IL-12p40 but prominent IL-10 may prevent eosinophil and cytotoxic cell-mediated inflammatory processes and pathogenesis to the host. The changes in this profile following anti-parasite therapy disclosed the dynamics of an immune adaptation associated with parasite accumulation and also with clearance of parasite infections.

Chemokines in onchocerciasis patients after a single dose of ivermectin

Ivermectin treatment will effectively diminish microfilariae (Mf) of Onchocerca volvulus in the skin of patients, but therapy is associated with adverse host inflammatory responses. To investigate the association of proinflammatory chemokines with the intensity of infection and clinical adverse reactions, chemokine serum levels were measured in patients following ivermectin treatment (100 microg/kg, 150 microg/kg or 200 microg/kg) or placebo. The density of O. volvulus Mf per mg skin decreased by 85%, 97%, 97% and 90% at day 3, at month 3, month 6 and at 1 year post-ivermectin. The cutaneous T cell-attracting chemokine (CTACK/CCL27) was found highly elevated in onchocerciasis patients compared to infection-free European controls (P = 0.0004) and it did not change following ivermectin or placebo to 1 year post-therapy. The chemokine RANTES/CCL5 (regulated on activated and normally T cell-expressed) was similarly high in onchocerciasis patients and infection-free European controls; the RANTES/CCL5 levels did not change following treatment until 6 months post-therapy but were slightly elevated at 1 year post-therapy (P < 0.02). In contrast, the Th2-type chemoattractants, thymus and activation regulated chemokine (TARC/CCL17) and macrophage-derived chemokine (MDC/CCL22), were activated at 3 days post-ivermectin (P < 0.0001) to return to pretreatment or lower levels thereafter. The Th1-type chemoattractants, macrophage inflammatory protein (MIP)-1alpha/CCL3 and MIP-1beta/CCL4 were low before ivermectin treatment, but following clearance of microfilariae of O. volvulus their levels increased from 6 months post-therapy onwards (for both at 12 months post-therapy, P < 0.0001). The adverse reaction scores (RS) in treated patients increased significantly on day 3 (P < 0.02) while it remained unchanged in those who received placebo (P = 0.22); RS interacted with the microfilarial density (P = 0.01), but not with the dose of ivermectin or with the serum levels of MIP-1alpha/CCL3, MIP-1beta/CCL4, TARC/CCL17, MDC/CCL22 and CTACK/CCL27. Our observations suggest that following ivermectin, macrophages as well as memory Th2-type lymphocytes and B cells, attracted and activated by MDC/CCL22, TARC/CCL17 and CTACK/CCL27, may contribute to dermal immune responses and O. volvulus Mf killing and clearance. The transient changes of TARC/CCL17 and MDC/CCL22 were not associated with clinical adverse responses, and the later rise of MIP-1alpha/CCL3 and MIP-1beta/CCL4 showed a reactivation of Type 1 immune responses associated with persistent low levels of O. volvulus microfilariae and an expiring O. volvulus infection.

IL-4 and IL-10 are essential for immunosuppression induced by high molecular weight proteins from Ascaris suum

The extract from Ascaris suum worms (Asc) impairs Th1 and Th2 responses to a non-related antigen, i.e. ovalbumin (OVA). Its suppressive capacity is due to high molecular weight components present in a gel filtration fraction (PI). This fraction is able to elicit IL-4 and IL-10 secretion. Interestingly enough, it induces anti-PI non-anaphylactic IgG1 synthesis through the action of IL-12/IFN-gamma. Here, we investigated the down-regulation of the immune response to OVA by PI in IL-12, IFN-gamma, IL-4 or IL-10 C57BL/6 knockout mice immunized with OVA+PI in adjuvant. OVA-induced delayed-type hypersensitivity (DTH) reactions, secretion of IL-2 and IFN-gamma, and IgG1, IgG2c and IgE antibody production were suppressed by PI in wild-type mice, as well as in IL-12- or IFN-gamma-deficient mice. In contrast, PI had no effect on anti-OVA IgE production and DTH, and induced only a partial suppression of IgG1 and IFN-gamma in IL-10(-/-) mice. The experiments also showed that IL-4 was involved in the PI-induced suppression of IgG2c antibodies and IL-2 secretion. Finally, down-regulation of IFN-gamma was not seen in mice lacking both IL-4 and IL-10, i.e. IL-4(-/-) mice treated with anti-IL-10 antibodies before immunization. These results exclude the participation of IL-12 and IFN-gamma in PI-induced immunosuppression, and highlight the essential role of IL-10 in the suppression of OVA-specific Th2-related parameters, as well as the cooperation between IL-10 and IL-4 in the suppression of Th1-related parameters.

Concurrent infection with an intestinal helminth parasite impairs host resistance to enteric Citrobacter rodentium and enhances Citrobacter-induced colitis in mice

Infections with intestinal helminth and bacterial pathogens, such as enteropathogenic Escherichia coli, continue to be a major global health threat for children. To test the hypothesis that intestinal helminth infection may be a risk factor for enteric bacterial infection, a murine model was established by using the intestinal helminth Heligomosomoides polygyrus. To analyze the modulatory effect of a Th2-inducing helminth on the outcome of enteric bacterium Citrobacter rodentium infection, BALB/c and STAT 6 knockout (KO) mice were infected with H. polygyrus, C. rodentium, or both. We found that only BALB/c mice coinfected with H. polygyrus and C. rodentium displayed a marked morbidity and mortality. The enhanced susceptibility to C. rodentium and intestinal injury of coinfected BALB/c mice were shown to be associated with a significant increase in helminth-driven Th2 responses, mucosally and systemically, and correlated with a significant downregulation of protective gamma interferon and with a dramatic upregulation of the proinflammatory tumor necrosis factor alpha response. In addition, C. rodentium-associated colonic pathology in coinfected BALB/c mice was significantly enhanced, whereas bacterial burden was increased and clearance was delayed. In contrast, coinfection in STAT 6 KO mice failed to promote C. rodentium infection or to induce a more severe intestinal inflammation and tissue injury, demonstrating a mechanism by which helminth influences the development of host protective immunity and susceptibility to bacterial infections. We conclude that H. polygyrus coinfection can promote C. rodentium-associated disease and colitis through a STAT 6-mediated immune mechanism.

Infections and allergy - helminths, hygiene and host immune regulation

There is increasing evidence that helminth infections can protect the host against Th2-mediated allergic pathologies, even though helminths themselves are strong Th2 inducers. In murine model systems, alleviation of allergy is not achieved through immune deviation to Th1, but is linked to expansion of regulatory T cell activity. Parasite infection does not prevent allergen sensitisation, but restricts the Th2 effector phase responsible for inflammation. Suppression of allergic inflammation can be transferred by Treg phenotype cells from an infected, allergen-naïve animal to an uninfected, sensitized recipient. Patent allergy in humans is also known to be modulated by helminth infections, suggesting that a similar regulatory network may be controlling immunopathologic disease in man.

The beneficial helminth parasite?

There is unequivocal evidence that parasites influence the immune activity of their hosts, and many of the classical examples of this are drawn from assessment of helminth infections of their mammalian hosts. Thus, helminth infections can impact on the induction or course of other diseases that the host might be subjected to. Epidemiological studies demonstrate that world regions with high rates of helminth infections consistently have reduced incidences of autoimmune and other allergic/inflammatory-type conditions. Here I review and assess the possible ways by which helminth infections can block or modulate concomitant disease processes. There is much to be learned from careful analysis of immuno-regulation in helminth-infected rodents and from an understanding of the immune status of acutely and chronically infected humans. The ultimate reward from this type of investigation will likely be a more comprehensive knowledge of immunity, novel ways to intervene in the immune response to alleviate autoimmune and allergic diseases (growing concerns in economically developed areas), and perhaps the development of helminth therapy for patients suffering from specific inflammatory, autoimmune or allergic disorders.

Comparative dynamics and phenotype of the murine immune response to Trichinella spiralis and Trichinella pseudospiralis

Infection of NIH mice with Trichinella spiralis and Trichinella pseudospiralis results in qualitatively comparable immune responses. Antigen-specific proliferation by mesenteric lymph node cells was transient and temporally associated with intestinal infection, but in contrast was sustained throughout infection by splenocytes. Early cytokine production by mesenteric lymph node cells was dominated by interleukin 10, but also IL-5 and IL-4, with rapid resolution following parasite expulsion from the gut. Splenocytes showed a mixed profile of cytokine production, although again dominated by IL-10 and sustained over 60 days of infection. All antibody classes were evident, with early production of IgA and IgG1, and subsequent secretion of other subclasses including IgG2a. Granulocytic infiltration of the spleen was significantly greater in T. spiralis infection. The concentration of serum corticosterone generally remained within normal boundaries, although was raised by day 60 in T. spiralis-infected mice. We conclude that the systemic suppression of inflammation reported for T. pseudospiralis does not result from selective induction of regulatory cytokines, or a major difference in the immune response to infection with T. spiralis.

Neutralizing anti-IL-10 antibody blocks the protective effect of tapeworm infection in a murine model of chemically induced colitis

There is increasing evidence that parasitic helminth infection has the ability to ameliorate other disease conditions. In this study the ability of the rat tapeworm, Hymenolepis diminuta, to modulate dinitrobenzene sulfonic acid (DNBS)-induced colitis in mice is assessed. Mice receiving DNBS (3 mg intrarectally) developed colitis by 72 h after treatment. Mice infected 8 days before DNBS with five H. diminuta larvae were significantly protected from the colitis, as gauged by reduced clinical disease, histological damage scores, and myeloperoxidase levels. This anticolitic effect was dependent on a viable infection and helminth rejection, because no benefit was observed in mice given killed larvae or in infected STAT6 knockout mice or rats, neither of which eliminate H. diminuta. The anticolitic effect of H. diminuta was associated with increased colonic IL-10 mRNA and stimulated splenocytes from H. diminuta- plus DNBS-treated mice produced more IL-10 than splenocytes from DNBS-only treated mice. Coadministration of an anti-IL-10 Ab blocked the anticolitic effect of prophylactic H. diminuta infection. Also, mice infected 48 h after DNBS treatment showed an enhanced recovery response. Finally, using a model of OVA hypersensitivity, we found no evidence of concomitant H. diminuta infection enhancing enteric responsiveness to subsequent ex vivo OVA challenge. The data show that a viable infection of H. diminuta in a nonpermissive system exerts a profound anticolitic effect (both prophylactically and as a treatment) that is mediated at least in part via IL-10 and does not predispose to enhanced sensitivity to bystander proteins.

Mucosal immunity and allergic responses: lack of regulation and/or lack of microbial stimulation?

Allergic hyperreactivity is defined as an exaggerated immune response [typically immunoglobulin E (IgE) but also non-IgE mediated] toward harmless antigenic stimuli. The prevalence of allergic disease has increased dramatically during the last 20 years, especially in developed countries. Both genetic and environmental factors contribute to susceptibility to allergy. Evidence has emerged supporting the hypothesis that a reduction in antigenic stimulation brought about by widespread vaccination, improvements in standards of hygiene, and extensive use of antibiotics has contributed to the dysregulation of T-helper 2 cell (Th2) type responsiveness that typifies allergy. Regulation of the inherently Th2-biased mucosal immune response is crucial both to the maintenance of homeostasis at this strategic defensive barrier and to the prevention of allergic disease. The ability of Th1 responses to counter-regulate Th2 reactivity is well characterized. More recently, interest has centered on regulatory T cells, which can suppress both Th1 and Th2 cells through the secretion of immunosuppressive cytokines such as interleukin-10 and transforming growth factor-beta. In this review, we discuss the basic cellular mechanisms of allergic diseases at mucosal surfaces, focusing on allergic responses to food, before examining newer work that suggests the induction of allergic hyperreactivity is due to a deficient immunoregulatory network, a lack of microbial stimulation, or both.

The gut: beyond immunology

The immune system is characterized by the ability to distinguish self from non-self. The intestinal immune system bears this latter property but, furthermore, it must discriminate among nutritious and beneficial substances from toxic or harmful ones. Considering that the gut has to be colonized by commensal bacteria participating in digestion as well as in the control of pathogen microorganisms, it is not surprising that mucosal surfaces are the largest and probably the most exquisitely specialized immune system's compartment. This means that not only innate and adaptive immunity are present, but further, particular structures, cells, and mechanisms such as physical barrriers, epithelia, Peyer's patches, M cells among others, which together are involved in the dynamic control of the homeostasis between gut and its flora. The present review deals with some popular conceptions about the digestive system with particular emphasis on the gut's immunology.

Regulation of allergy and autoimmunity in helminth infection

Parasitic infections are a major theme in the "hygiene hypothesis", as allergies and autoimmune diseases are less prevalent in countries with higher burdens of helminths and other parasitic organisms. Helminths"-the grouping of multicellular worm parasites including nematodes, cestodes and trematodes-tend to establish long-lived, chronic infections indicating successful down-modulation of the host immune system. In this review, we describe the intricate immunology of host-helminth interactions and how parasites manipulate immune responses to enhance their survival. In so doing, they often minimise immunopathology and, it is suggested, reduce host susceptibility to, and severity of allergic and autoimmune diseases. Studies on helminth-infected communities and individuals support the hypothesis that an immuno-regulatory network promoted by parasites extends its influence to limiting allergies. Experimental models are now probing more deeply into the area of immune modulation by helminths, and we discuss the likely mechanisms by which helminths could be establishing a strongly regulatory environment. Understanding and harnessing the modulatory capacity of helminths may uncover novel therapeutic interventions, mimicking and exploiting their evolution for our benefit. Parasitic infections are a major theme in the "hygiene hypothesis", as allergies and autoimmune diseases are less prevalent in countries with higher burdens of helminths and other parasitic organisms. Helminths"-the grouping of multicellular worm parasites including nematodes, cestodes and trematodes-tend to establish long-lived, chronic infections indicating successful down-modulation of the host immune system. In this review, we describe the intricate immunology of host-helminth interactions and how parasites manipulate immune responses to enhance their survival. In so doing, they often minimise immunopathology and, it is suggested, reduce host susceptibility to, and severity of allergic and autoimmune diseases. Studies on helminth-infected communities and individuals support the hypothesis that an immuno-regulatory network promoted by parasites extends its influence to limiting allergies. Experimental models are now probing more deeply into the area of immune modulation by helminths, and we discuss the likely mechanisms by which helminths could be establishing a strongly regulatory environment. Understanding and harnessing the modulatory capacity of helminths may uncover novel therapeutic interventions, mimicking and exploiting their evolution for our benefit.

Role of helminths in regulating mucosal inflammation

The rapid rise in prevalence of ulcerative colitis (UC) and Crohn's disease (CD) in highly developed countries suggests that environmental change engenders risk for inflammatory bowel disease (IBD). Eradication of parasitic worms (helminths) through increased hygiene may be one such change that has led to increased prevalence of these diseases. Helminths alter host mucosal and systemic immunity, inhibiting dysregulated inflammatory responses. Animals exposed to helminths are protected from experimental colitis, encephalitis, and diabetes. Patients with CD or UC improve when exposed to whipworm. Lamina propria (LP) mononuclear cells from helminth-colonized mice make less interleukin (IL)-12 p40 and IFN-gamma, but more IL-4, IL-13, IL-10, TGF-beta, and PGE(2) compared to LP mononuclear cells from naive mice. Systemic immune responses show similar skewing toward Th2 and regulatory cytokine production in worm-colonized animal models and humans. Recent reports suggest that helminths induce regulatory T cell activity. These effects by once ubiquitous organisms may have protected individuals from many of the emerging immune-mediated illnesses like IBD, multiple sclerosis, type I diabetes, and asthma.

Beyond allergen avoidance: update on developing therapies for peanut allergy

PURPOSE OF REVIEW

Food allergy has emerged as a significant health problem. Peanut allergy is a major cause of food-induced fatal and near fatal anaphylactic reactions, and the incidence in children is increasing. Attempts to manage peanut allergy by strict avoidance are often unsuccessful. The purpose of this review is to highlight the most promising novel approaches for treating peanut allergy beyond allergen avoidance.

RECENT FINDINGS

In the past 5 years much effort has been devoted to developing a treatment for peanut allergy. A recent clinical trial showed that monthly injections of humanized recombinant anti-IgE antibodies increased the threshold for allergic responses of peanut-sensitive individuals, at least to small amounts of peanut protein. However, this treatment cannot cure peanut allergy, and continuous monthly injections are necessary to maintain protection. Developing new therapies for the treatment of peanut allergy is essential. In reviewing publications between 2003 and 2005, several novel therapeutic approaches, tested in the murine model of peanut anaphylaxis appeared promising. Immunotherapy with engineered recombinant peanut protein and bacterial adjuvant significantly protected peanut allergic mice from anaphylaxis. It was also found that a Chinese herbal medicine formula called Food Allergy Herbal Formula-2 completely blocked anaphylaxis up to 5 weeks following therapy. These potent therapeutic effects are associated with immunoregulation of Th1 and Th2 responses.

SUMMARY

Although there is no effective and safe therapy for food allergy, many novel approaches are under investigation. Some of these approaches may provide allergists with effective treatments in the near future.

Parasite role reversal: worms on trial

Asthma has reached epidemic proportions globally. This has been attributed by many to improved hygiene. The frequent failure of conventional pharmaceuticals to manage the disease has led to the introduction of parasites as a potential alternative therapy for asthma and other immunological diseases. In this article, we briefly review the immunological rationale underpinning therapeutic parasitic infection, describe recently initiated trials, and highlight potential risks and benefits of introducing parasites into patient cohorts.

Helminth infections: protection from atopic disorders

Westernized countries are suffering from an epidemic rise in immunologic disorders, such as childhood allergy. A popular explanation is that the increased prevalence in allergy is due to a diminished or altered exposure to gut-dwelling microbes, resulting in a disordered immunoregulation. Various population studies have provided a strong case for the involvement of helminth infections in this respect. Detailed analysis of helminth-induced immune responses showed that helminths not only prime for polarized Th2 responses but also potently induce T-cell hyporesponsiveness. Recently, it has been demonstrated that helminths induce suppressed host immune responses by the priming for regulatory T cells. It is proposed that this regulatory T cell-inducing activity accounts for the protection observed in the development of allergic disorders. It would be interesting to define and characterize particular helminth molecules that have profound immunomodulatory capacities as a target for therapeutic application in the treatment or prophylaxis of allergic manifestations.

Helminth parasites--masters of regulation

Immune regulation by parasites is a global concept that includes suppression, diversion, and conversion of the host immune response to the benefit of the pathogen. While many microparasites escape immune attack by antigenic variation or sequestration in specialized niches, helminths appear to thrive in exposed extracellular locations, such as the lymphatics, bloodstream, or gastrointestinal tract. We review here the multiple layers of immunoregulation that have now been discovered in helminth infection and discuss both the cellular and the molecular interactions involved. Key events among the host cell population are dominance of the T-helper 2 cell (Th2) phenotype and the selective loss of effector activity, against a background of regulatory T cells, alternatively activated macrophages, and Th2-inducing dendritic cells. Increasingly, there is evidence of important effects on other innate cell types, particularly mast cells and eosinophils. The sum effect of these changes to host reactivity is to create an anti-inflammatory environment, which is most favorable to parasite survival. We hypothesize therefore that parasites have evolved specific molecular strategies to induce this conducive landscape, and we review the foremost candidate immunomodulators released by helminths, including cytokine homologs, protease inhibitors, and an intriguing set of novel products implicated in immune suppression.

Probiotics and down-regulation of the allergic response

The first clinical trials with probiotics, especially in the treatment of atopic eczema, have yielded encouraging results. Experimental studies have found that probiotics exert strain-specific effects in the intestinal lumen and on epithelial cells and immune cells with anti-allergic potential. These effects include enhancement in antigen degradation and gut barrier function and induction of regulatory and proinflammatory immune responses, the latter of which occurs more likely beyond the intestinal epithelium. Future studies should address more accurately how these and other possible mechanisms operate in the complex gastrointestinal macroenvironment in vivo and how these mechanisms are related to the clinical effects in a dose-dependent manner.

Helminth infection protects mice from anaphylaxis via IL-10-producing B cells

Modulation of the immune system by infection with helminth parasites, including schistosomes, is proposed to reduce the levels of allergic responses in infected individuals. In this study we investigated whether experimental infection with Schistosoma mansoni could alter the susceptibility of mice to an extreme allergic response, anaphylaxis. We formally demonstrate that S. mansoni infection protects mice from an experimental model of systemic fatal anaphylaxis. The worm stage of infection is shown to mediate this protective effect. In vivo depletion studies demonstrated an imperative role for B cells and IL-10 in worm-mediated protection. Furthermore, worm infection of mice increases the frequency of IL-10-producing B cells compared with that in uninfected mice. However, transfer of B cells from worm-infected mice or in vitro worm-modulated B cells to sensitized recipients exacerbated anaphylaxis, which was attributed to the presence of elevated levels of IL-4-producing B cells. Worm-modulated, IL-10-producing B cells from IL-4-deficient, but not IL-5-, IL-9- or IL-13-deficient, mice conferred complete resistance to anaphylaxis when transferred to naive mice. Therefore, we have dissected a novel immunomodulatory mechanism induced by S. mansoni worms that is dependent on an IL-10-producing B cell population that can protect against allergic hypersensitivity. These data support a role for helminth immune modulation in the hygiene hypothesis and further illustrate the delicate balance between parasite induction of protective regulatory (IL-10) responses and detrimental (IL-4) allergic responses.

Interleukin (IL) 5 levels and eosinophilia in patients with intestinal parasitic diseases

AIM

Intestinal parasitic diseases are commonly accompanied with diarrhoeal symptoms and allergic reactions. Eosinophilia occurs as a result of IL-5 synthesized from Th2 cells during allergic reactions. IL-5 acts as a factor activating eosinophils. The aim of this study was to compare the IL-5 cytokine measurements in serum samples and cell cultures. And also to compare eosinophilia observed in helminth infections and protozoon infections accompanied with allergy.

METHODS

Twenty-three patients who presented with diarrhoeal symptoms and allergic complaints were tested positive for intestinal parasites, as well as 21 controls with allergic complaints who did not have any intestinal parasites were included in this study. IL-5 production in in vitro cell cultures prepared by using phytohemaglutinin (PHA) to stimulate peripheral blood mononuclear cells (PBMC) obtained from the blood samples taken from these patients were compared with the IL-5 level in serum. Furthermore, the IL-5 production in protozoon and helminth infections was also compared. Absolute eosinophil values in 1 mm(3) of blood were calculated by means of peripheral smear in both groups within the scope of the study.

RESULTS

Parasites such as helminth detected in 15 (65.2%) and protozoon in 8 (34.8%) of the patients were included in this study. As regards the values of the sera in both patients with parasite infection and controls, the IL-5 production was found to be higher in the cell culture supernatant (P<0.001 and P<0.05). When the IL-5 level of the patients with helminth parasites was compared with that of those with protozoon, it was determined that the IL-5 level in serum was more significant in the patients with protozoon than in those with helminth (P<0.05). In the study group, the patients were found to have parasites, the percentage of eosinophil was 7.0% compared to 6.5% in the control group. Thus, there was no significant difference between the eosinophil values (P>0.05).

CONCLUSION

It was found that IL-5 cytokine levels in serum samples from the patients with helminth and protozoon displayed more measurable values as compared to the IL-5 levels after stimulation with mitogen. It is concluded that IL-5 acts as a triggering factor in the toxiallergic complaints commonly seen in helminth and protozoon infections.

Energetic and nutritional regulation of the adaptive immune response and trade-offs in ecological immunology

Ecological Immunology views immunocompetence as a costly process involving trade-off decisions among competing nutrient demands by different life-history traits. This review examines immunocompetence fitness costs in light of recent work on the role the energetic and nutritional status of the host plays in the regulation of the adaptive T-helper lymphocyte response. Three phenotypically distinct T-lymphocyte populations have been identified: the Th1 response, important in protecting against intracellular infections; the Th2 response, important in protecting against noninvasive infections such as helminthes; and the Th3 or Treg population, which downregulates polarized Th1 or Th2 responses. A strong Th1 response is protective against intracellular infections, while a Th2 response is protective against noninvasive infections. Adequate zinc and energy intake leads to a dominant Th1 response and a downregulated Th2 response, while deficiencies of either of these results in activation of the Th2 response and downregulation of the Th1 response. In contrast, adequate vitamin A intake leads to an activated Th2 response and downregulation of the Th1 response, while vitamin A deficiency reverses these patterns. These differential immune regulatory effects of energy and nutrient intake will have distinct effects on specific stages of the natural history of different pathogen infections where the protective roles of the Th1-Th2 responses are distinct. Accordingly, fitness costs of immunocompetence are more complex than currently proposed since trade-offs in energetic and nutritional resources produce cross-regulatory effects on immune system subcomponents.

Intradermal exposure of BALB/c strain mice to peanut protein elicits a type 2 cytokine response

There is a growing need for the development of methods to characterize the allergenic properties of novel proteins, particularly those expressed by transgenic crop plants. Hence, there is considerable interest in the development of suitable animal models for this purpose. The production of specific IgE antibody has been reported following sensitization with food allergen via oral or systemic (intraperitoneal) routes of exposure. We have characterized cytokine profiles induced by intradermal treatment of BALB/c strain mice with a purified peanut allergen, Arachis hypogea lectin. Mice were exposed to peanut lectin by intradermal administration and the cytokine responses in the lymph node draining the site of exposure analyzed at the secreted protein level by enyzme-linked immunosorbent assay (ELISA) and cytokine mRNA level by ribonuclease protection assay (RPA). Exposure to peanut lectin, under conditions that induced robust IgE antibody titers, was found to be associated with a T helper 2 (Th2)-type cytokine expression profile at both the mRNA and secreted protein levels. Culture of naïve lymph node cells with peanut lectin failed to stimulate marked proliferation or cytokine production, confirming this protein is not mitogenic for mouse lymphocytes. Furthermore, the expression of Th2 cytokines was associated with the effector/memory CD62L- cell population. Similar treatment with a non-allergenic protein, potato acid phosphatase, failed to induce Th2 cytokine expression. These data demonstrate that exposure of mice to peanut allergen results in the selective stimulation of a Th2-type response.

Hookworm infection: new developments and prospects for control

PURPOSE OF REVIEW

Hookworm infection remains a major health burden in developing countries. Successful control will likely be achieved through continued advances in our understanding of the epidemiology, molecular biology and immunopathogenesis of hookworm infection. This review summarizes recent advances in each of these fields, and discusses ongoing efforts to develop vaccines against hookworm anemia and growth delay.

RECENT DEVELOPMENTS

Revised estimates indicate that hookworms afflict over 700 million persons in tropical and subtropical regions. Prevalence and intensity often vary considerably at both the regional and local levels, and may be influenced by climate, soil composition, education, and socioeconomic status. Immunoepidemiological studies suggest that hookworm infection likely induces a complex mixture of host-protective and pathological immune responses. There has been substantial progress in elucidating the molecular pathogenesis of hookworm disease, primarily through the identification of a number of parasite virulence factors. Mass chemotherapy remains a mainstay of hookworm control strategies although continued use of benzimidazole anthelminthics is perhaps contributing to the development of anthelminthic resistance. Consequently, there remains a need for innovative approaches, including the development of vaccines and new chemotherapeutic agents, in order to provide effective global control of hookworm disease.

SUMMARY

Hookworm infection and disease is a significant threat to global health. Recent advances, particularly those at the molecular level, have provided a wealth of opportunities to better understand pathogenesis. This will likely allow for the development of novel measures such as vaccines to complement existing control methods.