Interactions between helminth parasites and allergy

The second generation and asthma: Prevalence of asthma among Israeli born children of Ethiopian origin

BACKGROUND

Immigrant populations moving from undeveloped countries with low asthma prevalence have shown increased asthma prevalence in their new Westernized environment. We compared the prevalence of asthma among Israeli born children of Ethiopian origin to that in non-Ethiopian children.

METHODS

Cross sectional study. Data was retrieved for children aged 6-18 years in four clinics with a large proportion of patients of Ethiopian origin. For each Israeli born child from Ethiopian origin we matched an Israeli born child of any other origin of the same age and gender, receiving primary care from the same physician at the same clinic. Asthma was defined as any visit to a primary care physician, emergency room or hospitalization related to asthma symptoms or subsequent purchasing of any asthma medication during 2008.

RESULTS

1217 children of Ethiopian origin and 1217 matched controls were studied. More Ethiopian children came from families with a low socioeconomic status (23.9% vs. 17%, p < 0.001), and with significantly lower parental smoking (5.1% vs. 40.1%, p < 0.001). The prevalence of asthma was 92/1217 (7.5%) among children of Ethiopian origin, compared to 122/1217 (10.0%) among the control group (OR = 0.74, 95% CI: 0.56-0.98, p = 0.032). When adjusted for tobacco exposure, the OR for risk of asthma in the Ethiopian children was 0.80 (95% CI: 0.59-1.09, p = 0.16).

CONCLUSION

Asthma prevalence in the second generation of Israeli born children of Ethiopian origin does not seem to differ from other children in their community. This observation supports the theory that environmental exposures, rather than genetic factors, dictated the increase in asthma in this immigrant population.

Helminths: Immunoregulation and Inflammatory Diseases-Which Side Are Trichinella spp. and Toxocara spp. on?

Macropathogens, such as multicellular helminths, are considered masters of immunoregulation due to their ability to escape host defense and establish chronic infections. Molecular crosstalk between the host and the parasite starts immediately after their encounter, which influences the course and development of both the innate and adaptive arms of the immune response. Helminths can modulate dendritic cells (DCs) function and induce immunosuppression which is mediated by a regulatory network that includes regulatory T (Treg) cells, regulatory B (Breg) cells, and alternatively activated macrophages (AAMs). In this way, helminths suppress and control both parasite-specific and unrelated immunopathology in the host such as Th1-mediated autoimmune and Th2-mediated allergic diseases. However, certain helminths favour the development or exacerbation of allergic responses. In this paper, the cell types that play an essential role in helminth-induced immunoregulation, the consequences for inflammatory diseases, and the contrasting effects of Toxocara and Trichinella infection on allergic manifestations are discussed.

Specific IgE Anti-Ascaris in Brazilian Children and Adolescents

From an article published by our group by Medeiros et al, we discuss and review the literature on the role of serum specific anti-ascaris IgE in patients with respiratory allergies living in countries where helminthic infestations are common. Medeiros et al conducted a study using 101 patients aged 12 to 21 years with respiratory allergy. Median IgE level was 660 IU/mL. Serum specific anti-ascaris IgE was positive in 73% (74/101) of the individuals, but parasitological stool examination yielded positive results in only 33.7% (34/101). The correlation coefficient between serum total IgE level and serum specific anti-ascaris IgE was 0.52 (P < 0.001) and this effect occurred regardless of eosinophil count and of the presence of intestinal helminthic infection. In patients with respiratory allergy with very high serum total IgE levels, in whom the past or present history of parasitic infection is a possible explanation, the presence of serum specific anti-ascaris IgE was common and should be better evaluated in allergic patients from Ascaris lumbricoides endemic areas.

Prerequisites for the pharmaceutical industry to develop and commercialise helminths and helminth-derived product therapy

During the past 10 years, immunologists, epidemiologists and parasitologists have made many new exciting discoveries in the field of helminth-mediated immune regulation. In addition, many animal experiments have shown that certain helminths or products derived from helminths can protect mice from developing allergic or autoimmune disease. Some clinical trials utilising Trichuris suis or Necator americanus for the treatment of allergic disorders and inflammatory bowel disease have been conducted. The outcomes of these trials suggest that they may be used to treat these disorders. However, to date no helminth therapy is routinely being applied to patients and no helminth-derived product therapy has been developed. In order to bring new drugs to the market and shoulder the enormous costs involved in developing such therapies, pharmaceutical companies need to be involved. However, currently the resources from the pharmaceutical industry devoted to this concept are relatively small and there are good reasons why the industry may have been reluctant to invest in developing these types of therapies. In this review article, the hurdles that must be overcome before the pharmaceutical industry might invest in these novel therapies are outlined.

Conference scene: Parasites to treat immune-mediated diseases?

A growing number of childhood diseases, such as allergic disorders (e.g., allergic rhinitis, atopic dermatitis and asthma) and other immune-mediated diseases (e.g., Type 1 diabetes), have been linked to environmental exposures during prenatal and early postnatal life, along with genetic determinants. Immunological mechanisms, diagnosis, treatment, prevention and management of allergies and other immune-mediated diseases were discussed at the 2012 Annual Meeting of the American Academy of Allergy, Asthma & Immunology in Orlando, FL, USA, 2-6 March 2012.

Toxocara seropositivity, atopy and wheezing in children living in poor neighbourhoods in urban Latin American

Background

Toxocara canis and T. cati are parasites of dogs and cats, respectively, that infect humans and cause human toxocariasis. Infection may cause asthma-like symptoms but is often asymptomatic and is associated with a marked eosinophilia. Previous epidemiological studies indicate that T. canis infection may be associated with the development of atopy and asthma.

Objectives

To investigate possible associations between Toxocara spp. seropositivity and atopy and childhood wheezing in a population of children living in non-affluent areas of a large Latin American city.

Methods

The study was conducted in the city of Salvador, Brazil. Data on wheezing symptoms were collected by questionnaire, and atopy was measured by the presence of aeroallergen-specific IgE (sIgE). Skin prick test (SPT), total IgE and peripheral eosinophilia were measured. Toxocara seropositivity was determined by the presence of anti-Toxocara IgG antibodies, and intestinal helminth infections were determined by stool microscopy.

Findings

Children aged 4 to 11 years were studied, of whom 47% were seropositive for anti-Toxocara IgG; eosinophilia >4% occurred in 74.2% and >10% in 25.4%; 59.6% had elevated levels of total IgE; 36.8% had sIgE≥0.70 kU/L and 30.4% had SPT for at least one aeroallergen; 22.4% had current wheezing symptoms. Anti-Toxocara IgG was positively associated with elevated eosinophils counts, total IgE and the presence of specific IgE to aeroallergens but was inversely associated with skin prick test reactivity.

Conclusion

The prevalence of Toxocara seropositivity was high in the studied population of children living in conditions of poverty in urban Brazil. Toxocara infection, although associated with total IgE, sIgE and eosinophilia, may prevent the development of skin hypersensitivity to aeroallergens, possibly through increased polyclonal IgE and the induction of a modified Th2 immune reaction.

Toxocara canis and T. cati are roundworms found in dogs and cats, respectively, that can also infect humans and cause several clinical features, including asthma-like symptoms. Human infections with T. canis have been associated with an increased prevalence of atopy and asthma. In the present study, we investigated the associations between Toxocara seropositivity with eosinophilia, total IgE, specific IgE and skin prick test reactivity to aeroallergens, as well as atopic and non-atopic wheezing. Toxocara seropositivity was associated with elevated eosinophil counts and total and aeroallergen-specific IgE but was also associated with a decreased prevalence of skin prick test. Toxocara seropositivity was not associated with atopic wheezing. In conclusion, our data show that human toxocariasis, although associated with eosinophilia and raised levels of total and allergen-specific IgE, may play a role in the modulation of allergic effector responses in the skin.

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.

Prevalence of asthma symptoms and associated factors in schoolchildren from Brazilian Amazon islands

OBJECTIVES

To determine the prevalence of asthma symptoms among schoolchildren living on two different Brazilian Amazon islands and to identify the risk factors related to this condition.

METHODS

A cross-sectional study of 400 schoolchildren (5-8 years old) using written questionnaires produced by the International Study of Asthma and Allergies in Childhood, a skin prick test (allergic sensitization), and a stool examination (for helminthic infection). Nonparametric tests were carried out, and the risk factors were identified by logistic regression.

RESULTS

The prevalence of active asthma symptoms was markedly higher in children living on Outeiro Island (OI) than those living on Combú Island (CBI) (30.5% and 16.5%, respectively). The logistic regression identified several risk factors of asthma symptoms on CBI: parental history of asthma, night coughing in the past year, and "currently have a cat". On OI, the major risk factors were parental history of asthma, personal history of eczema, having two or more older siblings, and night coughing in the past year. The risk factors in common on both the islands were night coughing in the past year and parental history of asthma.

CONCLUSIONS

The prevalence of asthma symptoms was higher in those with a lifestyle closer to that observed in urban areas (i.e., better sanitation and hygiene), reinforcing the protective effect of a rural environment. Different risk factors were associated with asthma symptoms in schoolchildren living on OI and on CBI. This fact may reflect the environmental individuality and particularities of each island.

Analysis of the course and treatment of toxocariasis in children-a long-term observation

Toxocariasis is a helminthozoonotic disease caused by ascarid larvae of Toxocara genus: Toxocara canis and Toxocara cati. In the reported study, the clinical course of toxocariasis and administered therapy were evaluated in 103 children. The majority of the children (68.9%) were from the rural environment, with a prevalence of boys (62.1%). At diagnosis of infection, 36 (35%) children reported recurrent abdominal pain, 19 (18.4%) headache, 6 (5.8%) loss of appetite, 2 subfebrile conditions, and 2 arthralgia, Moreover, 23 (22.3%) children demonstrated symptoms of atopic diseases; in 30 (29.1%) children, moderate enlargement of lymphatic nodes was noted. In five children (4.9%), ophthalmic examination revealed unilateral changes in the eye: in two cases retinitis; in one case fibrotic lesions in the vitreous body, complicated 1 year from diagnosis by retinal detachment; and in other children parafoveal lesions and cataract. Only two children with ocular changes at diagnosis reported visual disorders. In 64.3% of children, eosinophilia was observed. A covert form of the disease was diagnosed in 95.1% of the children and an ocular form in 4.9%. In all the children, antiparasitic treatment was implemented, repeated several times in some of them. After therapy, the mean titer of specific antibodies, the number of children with abdominal pains and enlarged lymphatic nodes were decreased, while headaches maintained at unchanged levels. In approximately one fourth of the children with negative results of antibodies after the therapy, the symptoms of the disease were still reported. Evaluation of the efficacy of treatment is not easy due to non-characteristic symptoms and low kinetics of specific anti Toxocara IgG decrease; however, high IgG titers suggest non-effective treatment of concomitant infection requiring subsequent therapy. Due to risk of ocular form, which may develop in any stage of the disease, irrespectively of specific antibodies concentrations, it seems justified to implement antiparasitic treatment in all children infected with T. canis.

Schistosoma haematobium infection levels determine the effect of praziquantel treatment on anti-schistosome and anti-mite antibodies

Field studies show an association between schistosome infection and atopy, but the effects of anti-helminthic treatment on this association have not yet been investigated in human populations with different schistosome endemicity levels. This study aimed to compare the effects of anti-helminthic treatment on responses directed against the house dust mite Dermatophagoides pteronyssinus (Derp1) and Schistosoma haematobium in Zimbabwean populations living in high and low schistosome infection areas. Derp1- and schistosome-specific IgE and IgG4 antibodies were quantified by ELISA before and 6 weeks after anti-helminthic treatment. Following treatment, there were changes in the immune responses, which varied with place of residence. After allowing for the effects of sex, age and baseline infection intensity, there was no significant treatment effect on the change in anti-schistosome IgE and IgG4 in the high infection area. However, the anti-schistosome IgE/IgG4 ratio increased significantly, while anti-Derp1 IgE responses decreased as a result of treatment. In the low infection area, treatment resulted in a significant increase in anti-worm IgE levels, but there was no significant treatment effect on anti-schistosome or anti-Derp1 IgE/IgG4 ratios. Thus, the study shows that the level of schistosome endemicity affects the host responses to schistosome and mite antigens following anti-helminthic treatment.

Associations between atopic markers in asthma and intestinal helminth infections in Cuban schoolchildren

Total serum IgE (tIgE), allergen-specific IgE (sIgE), and skin prick test (SPT) are commonly used markers for atopy and atopic disease. The association between these measures and their relationship to clinical symptoms differs in affluent and non-affluent countries. We investigated the role of intestinal helminth infections in observed variations in atopic markers and asthma, and possible diagnostic and epidemiological consequences. A cross-sectional study was conducted in Cuban schoolchildren (n = 1285; 4-14 yrs). Atopy was determined by SPT, sIgE, and tIgE; asthma by International Study of Asthma and Allergies in Childhood questionnaire; and intestinal helminth infections by stool examination. Percentages of tIgE, sIgE, and SPT positives were 88.9%, 25.5%, and 16.5%, respectively. Asthma was found in 20.8%, and helminth infections in 20.9% of the children. All three atopic markers were significantly associated with each other and with asthma. Median tIgE levels were higher in helminth-infected than in uninfected children, irrespective of their status of atopy/asthma. Discordant results between SPT and sIgE were observed in 22.6% of the children. Among SPT positives, 41% were sIgE negative. The proportion of SPT negatives among sIgE positives was 74% in helminth-infected and 58.4% in uninfected children (p < 0.05). Helminth infections affected tIgE levels, reconfirming the limited value of tIgE for diagnosis of atopy and asthma in tropical areas. Higher frequencies of sIgE than positive SPTs were observed, especially in helminth-infected children. This corresponds with current hypothesis on the role of helminths in atopy. However, the observed proportion of sIgE negatives among children with positive SPT suggests that other mechanisms may also be involved.

Influence of poverty and infection on asthma in Latin America

PURPOSE OF REVIEW

Asthma in Latin America is a growing public health problem and seems to be most prevalent and cause most morbidity among poor urban populations. This article will review the findings of recent human studies of the associations of asthma prevalence in Latin America with factors associated with poverty and inequality including childhood infections, stress, environment, nutrition and diet.

RECENT FINDINGS

Most asthma in childhood in Latin America is nonatopic and has been associated with exposures related to environmental dirt, diet and psychosocial distress. These factors are strongly linked to poverty and inequality. Interestingly, infections with bacterial, viral and parasitic pathogens in childhood appear to attenuate atopy in childhood but have no effect on asthma symptoms. There are biologically plausible mechanisms by which dirt exposures (e.g. endotoxin and other microbial products and nonmicrobial irritants), diet and obesity and psychosocial stress may cause airways inflammation.

SUMMARY

Most childhood asthma in Latin America is nonatopic for which important risk factors are those of poverty including poor hygiene (i.e. dirt), poor diet and obesity and psychosocial stress. There is evidence that exposures to infections in early childhood reduce atopy but not asthma. Research is needed to identify causes of nonatopic asthma that may be suitable for primary prevention or other public health intervention strategies for asthma in Latin America.

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.

A Single Dose of Oral BCG Moreau Fails to Boost Systemic IFN-γ Responses to Tuberculin in Children in the Rural Tropics: Evidence for a Barrier to Mucosal Immunization

Immune responses to oral vaccines are impaired in populations living in conditions of poverty in developing countries, and there is evidence that concurrent geohelminth infections may contribute to this effect. We vaccinated 48 children living in rural communities in Ecuador with a single oral dose of 100 mg of BCG Moreau RDJ and measured the frequencies of tuberculin-stimulated peripheral blood mononuclear cells expressing IFN-γ before and after vaccination. Vaccinated children had active ascariasis (n = 20) or had been infected but received short- (n = 13) or long-term (n = 15) repeated treatments with albendazole prior to vaccination to treat ascariasis. All children had a BCG scar from neonatal vaccination. There was no evidence of a boosting of postvaccination IFN-γ responses in any of the 3 study groups. Our data provide support for the presence of a barrier to oral vaccination among children from the rural tropics that appeared to be independent of concurrent ascariasis.

Do regulatory antibodies offer an alternative mechanism to explain the hygiene hypothesis?

The 'hygiene hypothesis', or lack of microbial and parasite exposure during early life, is postulated as an explanation for the recent increase in autoimmune and allergic diseases in developed countries. The favored mechanism is that microbial and parasite-derived products interact directly with pathogen recognition receptors to subvert proinflammatory signaling via T regulatory cells, thereby inducing anti-inflammatory effects and control of autoimmune disease. Parasites, such as helminths, are considered to have a major role in the induction of immune regulatory mechanisms among children living in developing countries. Invoking Occam's razor, we believe we can select an alternative mechanism to explain the hygiene hypothesis, based on antibody-mediated inhibition of immune responses that may more simply explain the available evidence.

IgE cross-reactivity between Ascaris lumbricoides and mite allergens: possible influences on allergic sensitization and asthma

Nematode infections such as Ascariasis are important health problems in underdeveloped countries, most of them located in the tropics where environmental conditions also promote the perennial co-exposure to high concentrations of domestic mite allergens. Allergic diseases are common, and most of patients with asthma exhibit a predominant and strong IgE sensitization to mites. It is unknown whether co-exposure to Ascaris lumbricoides and the domestic mites Blomia tropicalis and Dermatophagoides pteronyssinus potentiates Th2 responses and IgE sensitization, thereby modifying the natural history of allergy. Recently, we obtained experimental evidence of a high cross-reactivity between the allergenic extracts of these invertebrates, involving well-known allergens such as tropomyosin and glutathione transferases. There is indirect evidence suggesting that the clinical impact of these findings may be important. In this review, we discuss the potential role of this cross-reactivity on several aspects of allergy in the tropics that have been a focus of a number of investigations, some of them with controversial results.

Immune monitoring of Trichuris suis egg therapy in multiple sclerosis patients

Initial clinical trials using Trichuris suis eggs (TSO) in autoimmune diseases such as inflammatory bowel disease, revealed a striking suppressive effect on the autoimmune response. Here, we analysed the effect of TSO therapy on the course of multiple sclerosis (MS), as a Th1/Th17-associated autoimmune disease. Different immunological parameters in four patients with secondary progressive MS were surveyed during a 6-month therapy with TSO, focusing on the modulation of T-cell Th1-Th2 balance as well as on the innate immune response. We are able to show a slight downregulation of the Th1-associated cytokine pattern, especially relevant in interleukin (IL)-2 (P < 0.05 after 2 months of therapy), with a temporary increase of Th2-associated cytokines such as IL-4. Furthermore, mild eosinophily and changes in CD4+ and CD8+T cells and natural killer (NK) CD56 bright cell numbers were observed. The findings observed in this group of patients suggest that TSO therapy has a moderate immunomodulatory impact in MS.

Differences in both prevalence and titre of specific immunoglobulin E among children with asthma in affluent and poor communities within a large town in Ghana

BACKGROUND

Reports from several African countries have noted an increasing prevalence of asthma in areas of extensive urbanization.

OBJECTIVE

To investigate the relevance of allergen-specific sensitization and body mass index (BMI) to asthma/wheezing and exercise-induced bronchospasm (EIB) among children from affluent and poorer communities within a large town in Ghana.

METHODS

Children with physician-diagnosed asthma and/or current wheezing aged 9-16 years (n=99; cases) from three schools with differing socio-economic backgrounds [urban affluent (UA), urban poor (UP) or suburban/rural (SR)] were recruited from a cross-sectional study (n=1848) in Kumasi, Ghana, and matched according to age, sex and area of residence with non-asthmatic/non-wheezy controls. We assayed sera for IgE antibodies to mite, cat, dog, cockroach, Ascaris and galactose-α-1,3-galactose.

RESULTS

Children from the UA school had the lowest total serum IgE. However, cases from the UA school had a higher prevalence and mean titre of sIgE to mite (71.4%, 21.2 IU/mL) when compared with controls (14.3%, 0.8 IU/mL) or cases from UP (30%, 0.8 IU/mL) and SR community (47.8%, 1.6 IU/mL). While similar findings were observed with EIB in the whole population, among cases there was no difference in IgE antibody prevalence or titre between children with or without EIB. BMI was higher among UA children with and without asthma; in UP and SR communities, children with EIB (n=14) had a significantly higher BMI compared with children with asthma/wheezing without EIB (n=38) (18.2 vs. 16.4, respectively, P<0.01).

CONCLUSIONS AND CLINICAL RELEVANCE

In the relatively affluent school, asthma/wheezing and EIB were associated with high titre IgE antibodies to mite, decreased total IgE, and increased BMI. This contrasted with children in the urban poor school and suggests that changes relevant to a Western model of childhood asthma can occur within a short geographical distance within a large city in Africa.

Impact of early life exposures to geohelminth infections on the development of vaccine immunity, allergic sensitization, and allergic inflammatory diseases in children living in tropical Ecuador: the ECUAVIDA birth cohort study

Background

Geohelminth infections are highly prevalent infectious diseases of childhood in many regions of the Tropics, and are associated with significant morbidity especially among pre-school and school-age children. There is growing concern that geohelminth infections, particularly exposures occurring during early life in utero through maternal infections or during infancy, may affect vaccine immunogenicity in populations among whom these infections are endemic. Further, the low prevalence of allergic disease in the rural Tropics has been attributed to the immune modulatory effects of these infections and there is concern that widespread use of anthelmintic treatment in high-risk groups may be associated with an increase in the prevalence of allergic diseases. Because the most widely used vaccines are administered during the first year of life and the antecedents of allergic disease are considered to occur in early childhood, the present study has been designed to investigate the impact of early exposures to geohelminths on the development of protective immunity to vaccines, allergic sensitization, and allergic disease.

Methods/Design

A cohort of 2,403 neonates followed up to 8 years of age. Primary exposures are infections with geohelminth parasites during the last trimester of pregnancy and the first 2 years of life. Primary study outcomes are the development of protective immunity to common childhood vaccines (i.e. rotavirus, Haemophilus influenzae type B, Hepatitis B, tetanus toxoid, and oral poliovirus type 3) during the first 5 years of life, the development of eczema by 3 years of age, the development of allergen skin test reactivity at 5 years of age, and the development of asthma at 5 and 8 years of age. Potential immunological mechanisms by which geohelminth infections may affect the study outcomes will be investigated also.

Discussion

The study will provide information on the potential effects of early exposures to geohelminths (during pregnancy and the first 2 years of life) on the development of vaccine immunity and allergy. The data will inform an ongoing debate of potential effects of geohelminths on child health and will contribute to policy decisions on new interventions designed to improve vaccine immunogenicity and protect against the development of allergic diseases.

Trial registration

Current Controlled Trials ISRCTN41239086.

Effects of chronic ascariasis and trichuriasis on cytokine production and gene expression in human blood: a cross-sectional study

Background

Chronic soil-transmitted helminth (STH) infections are associated with effects on systemic immune responses that could be caused by alterations in immune homeostasis. To investigate this, we measured the impact in children of STH infections on cytokine responses and gene expression in unstimulated blood.

Methodology/Principal Findings

Sixty children were classified as having chronic, light, or no STH infections. Peripheral blood mononuclear cells were cultured in medium for 5 days to measure cytokine accumulation. RNA was isolated from peripheral blood and gene expression analysed using microarrays. Different infection groups were compared for the purpose of analysis: STH infection (combined chronic and light vs. uninfected groups) and chronic STH infection (chronic vs. combined light and uninfected groups). The chronic STH infection effect was associated with elevated production of GM-CSF (P = 0.007), IL-2 (P = 0.03), IL-5 (P = 0.01), and IL-10 (P = 0.01). Data reduction suggested that chronic infections were primarily associated with an immune phenotype characterized by elevated IL-5 and IL-10, typical of a modified Th2-like response. Chronic STH infections were associated with the up-regulation of genes associated with immune homeostasis (IDO, P = 0.03; CCL23, P = 0.008, HRK, P = 0.005), down-regulation of microRNA hsa-let-7d (P = 0.01) and differential regulation of several genes associated with granulocyte-mediated inflammation (IL-8, down-regulated, P = 0.0002; RNASE2, up-regulated, P = 0.009; RNASE3, up-regulated, p = 0.03).

Conclusions/Significance

Chronic STH infections were associated with a cytokine response indicative of a modified Th2 response. There was evidence that STH infections were associated with a pattern of gene expression suggestive of the induction of homeostatic mechanisms, the differential expression of several inflammatory genes and the down-regulation of microRNA has-let-7d. Effects on immune homeostasis and the development of a modified Th2 immune response during chronic STH infections could explain the systemic immunologic effects that have been associated with these infections such as impaired immune responses to vaccines and the suppression of inflammatory diseases.

Soil-transmitted helminth (STH or intestinal worm) infections are extremely common infectious diseases of childhood in developing countries. Infections tend be chronic and may last for many years. Chronic STH infections are associated with modulation of the immune response, a consequence of which may be a reduced prevalence of allergic inflammatory diseases such as asthma. The mechanisms by which STH infections suppress inflammatory responses are poorly understood. In this study, we hypothesized that STH infections may affect immune responses through alterations of immune homeostasis (or the steady-state adjustments of the immune system that maintain equilibrium). We investigated the capacity of blood from children classified as having no, light, or chronic STH infections to produce cytokines at rest (i.e. no immunologic stimulation) and the expression of genes in blood samples. Our data show that blood cells of children with chronic STH infections have an altered immune response that is likely to be associated with less allergic inflammation (the modified Th2 response) and that the expression of some inflammatory genes are reduced. Our findings provide insights into the mechanisms by which STH infections suppress immune responses in children to ensure the survival of the parasite and reduce inflammation.

Atopy and current intestinal parasite infection: a systematic review and meta-analysis

BACKGROUND

The rate of increase in prevalence of allergic disease in some countries implies environmental exposures may be important etiological factors. Our aim was to undertake a systematic review and meta-analysis of epidemiological studies to quantify the association between current intestinal parasite infection and the presence of atopy and to determine whether this relation is species specific.

METHODS

We searched MEDLINE, EMBASE, LILIACS and CAB Abstracts (to March 2009); reviews; and reference lists from publications. No language restrictions were applied. We included studies that measured current parasite infection using direct fecal microscopy and defined atopy as allergen skin sensitization or presence of specific IgE. We estimated pooled odds ratios (OR) and 95% confidence intervals (95% CI) using data extracted from published papers using random-effects model.

RESULTS

Twenty-one studies met our inclusion criteria. Current parasite infection was associated with a reduced risk of allergen skin sensitization OR 0.69 (95% CI 0.60-0.79; P < 0.01). When we restricted our analyses to current geohelminth infection, the size of effect remained similar OR 0.68 (95% CI 0.60-0.76; P < 0.01). In species-specific analysis, a consistent protective effect was found for infection with Ascaris lumbricoides, Tricuris trichuria, hookworm and Schistosomiasis. There were insufficient data to pool results for atopy defined by the presence of specific IgE.

CONCLUSION

Intestinal parasite infection appears to protect against allergic sensitization. Work should continue to identify the mechanisms of this effect and means of harnessing these to reduce the global burden of allergic disease.

Pulmonary ascariasis: two cases in Austria and review of the literature

Ascariasis is the most common helminthic infection, with an estimated worldwide prevalence of 25%. The estimated mortality ranges from 0.8 to 1%. Second stage larvae pass through the intestinal wall and migrate via the portal vein system to the liver and then proceed to the lungs, where they may produce pneumonia and eosinophilia. Symptoms include wheezing, dyspnea, nonproductive cough, hemoptysis, and fever. Two cases of pulmonary ascariasis in Austrian males are reported. Both patients presented with dyspnea, nonproductive cough, fever, and eosinophilia (19 and 26%). One patient additionally had pulmonary infiltrates. Recent travel history was unremarkable in both individuals. Serology for Ascaris was positive twice in both patients, while microscopic examination of stool was negative for helminthic ova. Extensive diagnostic procedures were performed to rule out possible differentials for the patients symptoms. Both patients responded well to antiparasitic treatment with albendazole 400 mg and mebendazole 100 mg q12h for 3 days, respectively. This report highlights the importance of considering parasitic infection in patients presenting with eosinophilia and pulmonary symptoms also in Austria.

Toxocara and Ascaris seropositivity among patients suspected of visceral and ocular larva migrans in the Netherlands: trends from 1998 to 2009

Toxocara canis, Toxocara cati and Ascaris suum are roundworms of dogs, cats and pigs, respectively, that can also infect humans. These zoonotic helminths have a worldwide distribution and are also endemic in the Netherlands. Infection with Toxocara sp. may result in visceral larva migrans (VLM) or ocular larva migrans (OLM) caused by the migrating larvae. Although A. suum has been reported to occasionally mature to the adult stage in humans, clinical cases of VLM suspected to be caused by A. suum have been described. Diagnosis of these helminth infections relies mainly on serology. Here we analyse the results from the Toxocara and Ascaris IgG-ELISA from a total of 2,838 serum samples from VLM and OLM suspected patients that were sent to our institution from 1998 to 2009. Results indicate that for each year the Ascaris seropositivity is significantly higher compared to the Toxocara seropositivity. Furthermore, while Toxocara seropositivity has decreased over time, the Ascaris seropositivity has not significantly changed for the past 12 years. The Ascaris and Toxocara seropositivity was also shown to increases with age and, while gender has no influence on the Ascaris seropositivity, males showed higher Toxocara seropositivity.

Co-infection with Ascaris lumbricoides modulates protective immune responses against Giardia duodenalis in school Venezuelan rural children

We evaluated the effect of Ascaris lumbricoides on Giardia duodenalis infection and TH1/TH2 type immune mechanisms toward this parasite in 251 rural parasitized and 70 urban non-parasitized school children. The children were classified according to light (0-5000 eggs/g faeces) or moderate (>5001-50,000 eggs/g faeces) A. lumbricoides infection. Anti G. duodenalis skin hyper-reactivity, IgE, IgG, IL-13, IFN γ, IL6 and IL-10 levels were compared among G. duodenalis infected and non-infected children according to light or moderate A. lumbricoides infection. It was found that 62% of the A. lumbricoides moderately infected children were co-infected by G. duodenalis compared to 45% of the lightly infected group. After treatment, 42% of the A. lumbricoides moderately group were infected with G. duodenalis compared to 11% of their lightly counterparts, being A. lumbricoides IL-10 levels higher (p<0.0001) in the moderately infected group. In the A. lumbricoides lightly parasitized children, G. duodenalis infection was associated to a significant increase (p<0.005) of the levels of G. duodenalis IL-13, IFN-γ, IL-6, IgE, IgG and skin test hyper reactivity. In contrast, there was no effect of G. duodenalis infection in the elevation of these parameters among the A. lumbricoides moderately parasitized group, being those levels similarly lower as those observed in the control group. Inverse correlations were found between the levels of anti G duodenalis antibodies, skin test hyper-reactivity and cytokines with the intensity of A. lumbricoides infection (p>0.0001) and A. lumbricoides IL-10 levels (p>0.0001), suggesting that co-infection with A. lumbricoides may affect both TH1 and TH2 type immunity against G. duodenalis that may play an important role in the susceptibility to the infection after chemotherapy in children from endemic areas.

A helminth immunomodulator exploits host signaling events to regulate cytokine production in macrophages

Parasitic worms alter their host's immune system to diminish the inflammatory responses directed against them, using very efficient immunomodulating molecules. We have previously shown that the helminth immunomodulator cystatin (AvCystatin) profoundly reduces the progression of inflammatory diseases via modulation of macrophages. Here we elucidate the signaling events in macrophages triggered by AvCystatin. Labeled AvCystatin was predominantly taken up by macrophages and subsequently induced the phosphorylation of the mitogen-activated protein kinases (MAPK) ERK1/2 and p38. IL-10 expression induced by AvCystatin in macrophages was tyrosine kinase sensitive and dependent on activation of both MAP kinases, in clear contrast to expression of IL-12/23p40. In addition, phosphorylation of the transcription factors CREB and STAT3 was induced by AvCystatin and regulated by phospho-ERK. Chemical inhibition of phosphoinositide 3-kinase (PI3K) reduced AvCystatin-induced cytokine release; however, AKT, the downstream target of PI3K, was not activated following AvCystatin exposure. To characterize signaling elements involved in alteration of the macrophage phenotype we applied mathematical modeling. Experimental testing of the in silico generated hypotheses identified dual specificity phosphatase (DUSP) 1 and 2, as regulators in AvCystatin triggered macrophages in vitro and in vivo. In particular, DUSP1 was subsequently found to be responsible for regulation of ERK- and p38-phosphorylation and controlled the IL-10 expression in macrophages by AvCystatin. Thus, we show that AvCystatin exploits activation and deactivation pathways of MAP kinases to induce regulatory macrophages. This study provides insights into molecular mechanisms of macrophage manipulation by parasites and highlights the utility of mathematical modeling for the elucidation of regulatory circuits of immune cells.

Helminths have the ability to interfere with their host's immune response, thus downregulating inflammatory responses. We previously demonstrated the role of helminth infections or isolated helminth proteins in suppressing bystander immune responses in mouse models of allergy and colitis via a macrophage and IL-10 dependent mechanism. The current study elucidates the signaling events induced by the parasite immunomodulator AvCystatin, leading to alteration of the macrophage phenotype. AvCystatin was predominantly taken up by macrophages and induced cytokine production by phosphorylation of mitogen-activated protein kinases (MAPK) ERK1/2 and p38. To identify molecules involved in the regulation of IL-10 production we developed a mathematical model. In silico generated data suggested a negative feedback mechanism via deactivating ERK1/2 and p38. Ensuing experiments validated the model and revealed AvCystatin-induced dual specificity phosphatases (DUSPs) as negative regulators of MAPK activation and IL-10 expression in vitro and in vivo. Taken together, the nematode immunomodulator AvCystatin targets activating and deactivating pathways of MAPK to induce regulatory macrophages.

Infections and asthma: new insights into old ideas

A relationship between infections and allergic airway disease has long been recognized, and many reviews have been written on this topic. However, both clinical and basic science studies published in the last 3 years provide new insights into the relationship between infection and allergic conditions. In this review, we focus on these very recent studies, which address the role of infection in the development, maintenance, and exacerbation of asthma. Bacterial, viral, fungal, and parasitic infections have each been examined and provide a framework for these novel concepts.

Food allergy prevalence in children of opisthorchiasis world region

The study of the food allergy prevalence in children of Tomsk city and rural areas with high and low opisthorchiasis level was performed. It was revealed that the food allergy prevalence in children is associated with chronic opisthorchiasis level.

Towards improved diagnosis of zoonotic trematode infections in Southeast Asia

Humans in Southeast Asia are at risk for at least 70 species of food-borne and water-borne trematodes, including blood flukes, intestinal flukes, liver flukes and lung flukes, which are shared with a great variety of animals. Co-infection with several other zoonotic trematodes is pervasive, and hence differential diagnosis represents a major challenge. Many zoonotic trematodes are commonly overlooked, leading to unreliable prevalence data, underappreciation of their veterinary and public health burden and impact, and general neglect with respect to treatment and control. Additionally, many eggs are indistinguishable by microscopy. For example, failure to address this diagnostic dilemma has resulted in overestimation of Clonorchis sinensis prevalence and underestimation of minute intestinal flukes. Test insensitivity is becoming a problem of prime interest as surveillance is gaining in importance and various control programmes now regularly register progress. Hence, the likelihood of underestimating the true burden of disease is growing in well-controlled areas when the faecal egg excretion among infected individuals approaches zero. While antibody testing has ultimate sensitivity, its use as a test of cure remains contentious. On the other hand, employing faecal egg detection as the diagnostic 'gold' standard makes many positive antibody test results (incorrectly) appear false. Polymerase chain reaction (PCR)-based diagnostics could solve this dilemma, but more experience is needed and costs must be brought down to permit large-scale use of this approach. The future development of virtual microscopy to be used for diagnosis of parasitic infections in the field could make ordinary microscopy obsolete by electronically capturing specimens at point-of-contact in remote areas.

The landscape of human genes involved in the immune response to parasitic worms

BACKGROUND

More than 2 billion individuals worldwide suffer from helminth infections. The highest parasite burdens occur in children and helminth infection during pregnancy is a risk factor for preterm delivery and reduced birth weight. Therefore, helminth infections can be regarded as a strong selective pressure.

RESULTS

Here we propose that candidate susceptibility genes for parasitic worm infections can be identified by searching for SNPs that display a strong correlation with the diversity of helminth species/genera transmitted in different geographic areas. By a genome-wide search we identified 3478 variants that correlate with helminth diversity. These SNPs map to 810 distinct human genes including loci involved in regulatory T cell function and in macrophage activation, as well as leukocyte integrins and co-inhibitory molecules. Analysis of functional relationships among these genes identified complex interaction networks centred around Th2 cytokines. Finally, several genes carrying candidate targets for helminth-driven selective pressure also harbour susceptibility alleles for asthma/allergy or are involved in airway hyper-responsiveness, therefore expanding the known parallelism between these conditions and parasitic infections.

CONCLUSIONS

Our data provide a landscape of human genes that modulate susceptibility to helminths and indicate parasitic worms as one of the major selective forces in humans.

The hidden sense of symptoms: urticaria can be beneficial

Evolutionary Medicine can be useful when analysing the origin of disease and symptoms. Acute urticaria or anaphylaxis is bothersome and potentially life-threatening. We analyse this symptom-complex in the context of Gastro-allergic Anisakiasis (GAA), where the human is an incidental host for the cosmopolitan fish-nematode Anisakis simplex (A. simplex). The immunological response against this nematode resembles that against other helminths, but overt expression of allergic symptoms is by far more frequent in GAA. This could be due to the missing co-evolutionary relationship between host and parasite. Features of acute gastric parasitism with and without overt allergic type 1 hypersensitivity symptoms are compared with the abdominal complications in intestinal Anisakiasis, where clinically visible IgE mediated symptoms are missing. In GAA, parasite induced chronic abdominal complications are missing. We postulate that urticaria in GAA can be considered the price for rapidly expelling the live larva of A. simplex in those subjects whose evolutionary history made them more resistant to other helminth parasites. Further, urticaria is explained as a possibly exaggerated immunopathological feature in this special type of acute parasitism, where sensitized mast-cells are not only present in the skin, but also in the gastro-intestinal mucosa. This evolutionary analysis of clinical observations is the first known report that addresses the possible beneficial feature of hypersensitivity type 1 response with overt allergic urticaria-anaphylaxis in GAA and confers an evolutionary based sense to the acute IgE-mediated reaction.

Allergic conjunctivitis and the impact of allergic rhinitis

Although nasal allergy has been prominent in allergy research, ocular allergy is increasingly recognized as a distinct symptom complex that imposes its own disease burden and reduction in patients' quality of life. In the past year, knowledge of the relationships between allergic conjunctivitis and allergic rhinitis has increased. Allergic conjunctivitis is highly prevalent and has a close epidemiologic relationship with allergic rhinitis. Both conditions also exhibit similar pathophysiologic mechanisms. Pathways of communication are thought to increase the likelihood of an inflammatory reaction at both sites following allergen exposure of nasal or ocular tissue. Clinical trials of intranasal therapies have demonstrated efficacy in allergic conjunctivitis and rhinitis. Newer intranasal steroids decrease ocular symptoms, potentially achieving efficacy by suppressing the naso-ocular reflex, downregulation of inflammatory cell expression, or restoration of nasolacrimal duct patency. Proposed pathophysiologic interactions between allergic rhinitis and ocular allergy underscore the need for therapies with efficacy in both symptom sets.

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.

Helminth-induced CD19+CD23hi B cells modulate experimental allergic and autoimmune inflammation

Numerous population studies and experimental models suggest that helminth infections can ameliorate immuno-inflammatory disorders such as asthma and autoimmunity. Immunosuppressive cell populations associated with helminth infections include Treg and alternatively-activated macrophages. In previous studies, we showed that both CD4⁺CD25⁺ Treg, and CD4^– MLN cells from Heligmosomoides polygyus-infected C57BL/6 mice were able to transfer protection against allergic airway inflammation to sensitized but uninfected animals. We now show that CD4^–CD19⁺ MLN B cells from infected, but not naïve, mice are able to transfer a down-modulatory effect on allergy, significantly suppressing airway eosinophilia, IL-5 secretion and pathology following allergen challenge. We further demonstrate that the same cell population can alleviate autoimmune-mediated inflammatory events in the CNS, when transferred to uninfected mice undergoing myelin oligodendrocyte glycoprotein_(p35–55)-induced EAE. In both allergic and autoimmune models, reduction of disease was achieved with B cells from helminth-infected IL-10^−/− donors, indicating that donor cell-derived IL-10 is not required. Phenotypically, MLN B cells from helminth-infected mice expressed uniformly high levels of CD23, with follicular (B2) cell surface markers. These data expand previous observations and highlight the broad regulatory environment that develops during helminth infections that can abate diverse inflammatory disorders in vivo.

Asthma: time to confront some inconvenient truths

Despite major advances in the understanding of the pathogenesis of asthma and improvements in management, the accompanying benefits from public health initiatives and clinical practice have arguably been less than expected. For example, there are no effective public health strategies or treatment regimes that reduce the risk of developing asthma or influence its natural history. These represent priority areas for future translational research, which would need to investigate genetic and environmental interactions and vaccine strategies. In terms of asthma management it is tempting to focus on novel drug therapies; however, a case can be made that the priority is to undertake research that leads to improvements in the use of existing treatments through public health and primary care initiatives. Guidelines represent an important component of this approach, with recommendations for asthma imbedded within respiratory guidelines that can be implemented in the developing world where other acute and chronic respiratory disorders are common. This approach offers the best opportunity to close the gap between what is currently achieved in asthma management and that which is potentially achievable.

Allergic disorders in Africa and africans: is it primarily a priority?

In Africa, the burden of some diseases has been a problem for centuries. The spectrum of African diseases includes allergies, infections, nutritional deficiencies, and natural disasters. Efforts made by scientists to search for possible means of disease control have been outstanding; however, in some infections, solutions are still out of reach. In disease control programs, it might be worthwhile to pay attention to the most striking diseases than merely follow a holistic approach. This short review tackles the problems of allergy and allergens in Africa as compared with other disease burdens that may suggest the need for a more balanced approach based on priority.

Chronic intestinal helminth infections are associated with immune hyporesponsiveness and induction of a regulatory network

Helminth infections have been associated with protection against allergy and autoimmune diseases. We investigated the effects of chronic infections with Ascaris lumbricoides and Trichuris trichiura (measured twice over a 5-year period) on cytokine and antibody responses. We collected blood from 1,060 children aged 4 to 11 years living in a poor urban area of Brazil and measured Th1 (gamma interferon [IFN-gamma]) and Th2 (interleukin-5 [IL-5] and IL-13) cytokines and the regulatory cytokine IL-10 in unstimulated and stimulated (with mitogen or A. lumbricoides antigens) cultures of peripheral blood leukocytes and levels of total IgE and anti-A. lumbricoides IgG4 and IgE in serum. Intestinal helminth infections were associated with an increased proportion of children producing IL-5 in response to A. lumbricoides and producing IL-10 spontaneously, especially among coinfected and chronically infected children. Helminth infections were associated with a generalized suppression of cytokine responses to mitogen. Levels of total IgE and anti-A. lumbricoides IgG4 and IgE were especially elevated in chronically infected children. In conclusion, intestinal helminth infections were associated with a typical Th2 immune response profile and with the induction of immune hyporesponsiveness that was associated with greater frequencies of the production of spontaneous IL-10.

Does treatment of intestinal helminth infections influence malaria? Background and methodology of a longitudinal study of clinical, parasitological and immunological parameters in Nangapanda, Flores, Indonesia (ImmunoSPIN Study)

Background

Given that helminth infections are thought to have strong immunomodulatory activity, the question whether helminth infections might affect responses to malaria antigens needs to be addressed. Different cross-sectional studies using diverse methodologies have reported that helminth infections might either exacerbate or reduce the severity of malaria attacks. The same discrepancies have been reported for parasitemia.

Methods/Design

To determine the effect of geohelminth infections and their treatment on malaria infection and disease outcome, as well as on immunological parameters, the area of Nangapanda on Flores Island, Indonesia, where malaria and helminth parasites are co-endemic was selected for a longitudinal study. Here a Double-blind randomized trial will be performed, incorporating repeated treatment with albendazole (400 mg) or placebo at three monthly intervals. Household characteristic data, anthropometry, the presence of intestinal helminth and Plasmodium spp infections, and the incidence of malaria episodes are recorded. In vitro cultures of whole blood, stimulated with a number of antigens, mitogens and toll like receptor ligands provide relevant immunological parameters at baseline and following 1 and 2 years of treatment rounds. The primary outcome of the study is the prevalence of Plasmodium falciparum and P. vivax infection. The secondary outcome will be incidence and severity of malaria episodes detected via both passive and active follow-up. The tertiary outcome is the inflammatory cytokine profile in response to parasite antigens. The project also facilitates the transfer of state of the art methodologies and technologies, molecular diagnosis of parasitic diseases, immunology and epidemiology from Europe to Indonesia.

Discussion

The study will provide data on the effect of helminth infections on malaria. It will also give information on anthelminthic treatment efficacy and effectiveness and could help develop evidence-based policymaking.

Trial registration

This study was approved by The Ethical Committee of Faculty of Medicine, University of Indonesia, ref:194/PT02.FK/Etik/2006 and has been filed by ethics committee of the Leiden University Medical Center. Clinical trial number:ISRCTN83830814. The study is reported in accordance with the CONSORT guidelines for cluster-randomized studies.

Helminth-derived immunomodulators: can understanding the worm produce the pill?

Helminths may protect humans against allergic and autoimmune diseases and, indeed, defined helminth-derived products have recently been shown to prevent the development of such inflammatory diseases in mouse models. Here, we propose that helminth-derived products not only have therapeutic potential but can also be used as unique tools for defining key molecular events in the induction of an anti-inflammatory response and, therefore, for defining new therapeutic targets.

Prevalence of antibodies against Ascaris suum and its association with allergic manifestations in 4-year-old children in The Netherlands: the PIAMA birth cohort study

The association between helminth infections and childhood atopic diseases remains controversial. The majority of studies have been carried out in tropical areas, whereas less information is available from western countries with low intensity of helminth infections. In the Netherlands, the infection of pigs with Ascaris suum is very common, particularly on pig farms with outdoor facilities. This helminth can also infect humans, causing visceral larva migrans. This study aims at determining the prevalence of antibodies against A. suum and its association with allergic symptoms and sensitisation in a population of 4-year-old children living in The Netherlands. Blood samples from 629 children from the prospective birth cohort Prevention and Incidence of Asthma and Mite Allergy (PIAMA) study were examined for Ascaris antibodies. Data on allergic symptoms and sensitisation were collected using questionnaires and radioallergosorbent tests (RAST). A total of 45 out of 629 (7%) were found to be Ascaris-seropositive. In addition, a positive association between Ascaris seropositivity and wheeze in the last year, doctor-diagnosed asthma and food and aero-allergen sensitisation was found. These results support the hypothesis that low-level or transient infection with helminths enhances allergic reactivity.

Mucosal immunology of geohelminth infections in humans

There is limited data on the human mucosal immune response to geohelminths, but extensive data from experimental animals. Geohelminth infections may modulate mucosal immunity with effects on parasite expulsion or persistence and mucosal inflammation. Geohelminths are considered to have important effects on immunity to mucosal vaccines, infectious disease susceptibility, and anti-inflammatory effects in inflammatory bowel disease and asthma. This review will discuss the findings of studies of human immunity to geohelminths and their potential effects on non-parasite mucosal immune responses. Such effects are likely to be of public health importance in middle- and low-income countries where these parasites are endemic. There is a need for human studies on the effects of geohelminth infections on mucosal immunity and the potential for anthelmintic treatment to modify these effects. Such studies are likely to provide important insights into the regulation of mucosal immunity and inflammation, and the development of more effective mucosal vaccines.