Association of atopy, asthma, allergic rhinoconjunctivitis, atopic dermatitis and intestinal helminth infections in Cuban children

Geographische Unterschiede zwischen städtischem und ländlichem Raum beim Risiko für atopische Dermatitis: Systematischer Review und Meta-Analyse

Die atopische Dermatitis ist die häufigste chronisch‐entzündliche Hauterkrankung im Kindesalter. Einige Studien kamen zu dem Ergebnis, das Risiko für diese Erkrankung sei im städtischen Raum höher als im ländlichen. Wir haben die verfügbaren Studien systematisch untersucht und eine Meta‐Analyse durchgeführt, um Unterschiede im Risiko für atopische Dermatitis zwischen städtischem und ländlichem Raum zu erkennen. Die Suche in den Datenbanken Embase und MEDLINE wurde am 19. April 2021 durchgeführt. Einschlusskriterium war das Stichwort “Beobachtungsstudie”. Wir haben außerdem Subgruppenanalysen bezüglich Patientenalter, Publikationsjahr und Land durchgeführt. Insgesamt wurden bei der Datenbanksuche 2115 Studien aufgefunden, von denen letztlich 43 Studien mit insgesamt 1 728 855 Patienten in die Meta‐Analyse eingeschlossen wurden. Ein Wohnsitz im städtischen Raum war mit einem erhöhten Risiko für atopische Dermatitis assoziiert; die Odds Ratio war 1,56 (95 %‐Konfidenzintervall 1,43–1,71). Dieses signifikant erhöhte Risiko war nur bei Kindern zu beobachten (Odds Ratio 1,55, 95 %‐Konfidenzintervall 1,39–1,73), nicht jedoch bei Erwachsenen. Hier betrug die Odds Ratio 1,29 (95 %‐Konfidenzintervall 0,99–1,67). Das Risiko für atopische Dermatitis ist in den letzten Jahrzehnten angestiegen, wobei das Risiko in Entwicklungsländern mit einer Odds Ratio von 1,95 höher liegt als in Industrieländern (Odds Ratio 1,35). Unsere Studie bestätigt die Assoziation zwischen atopischer Dermatitis und dem Wohnsitz im städtischen gegenüber dem ländlichen Raum.

Geographic differences in atopic dermatitis risk between urban and rural area: A systematic review and meta-analysis

Atopic dermatitis is the most common chronic inflammatory skin disease affecting children. Some studies have reported a higher risk of atopic dermatitis in urban areas than in rural areas. We systematically reviewed and carried out a meta-analysis to investigate the differences in the development of atopic dermatitis between urban and rural areas. The search was performed on April 19, 2021, using Embase and MEDLINE databases. Eligible for inclusion were observational studies. Subgroup analyses were performed for age, publication year, and country. We identified 2,115 studies, and 43 studies with 1,728,855 subjects were finally included. Urban residency was associated with an increased risk of atopic dermatitis, with an odds ratio of 1.56 (95% confidence interval, 1.43-1.71). A significantly increased risk was observed only in children, with an odds ratio of 1.55 (95% confidence interval, 1.39-1.73), but not in adults, with an odds ratio of 1.29 (95% confidence interval, 0.99-1.67). The risk has increased in recent decades, with a higher risk in developing countries (odds ratio, 1.95) compared to developed countries (odds ratio, 1.35). Our study provides evidence of an association between atopic dermatitis and urban compared to rural living.

The Relationship of Parasite Allergens to Allergic Diseases

PURPOSE OF REVIEW

Helminth infections modify the natural history of allergic diseases, by either decreasing or increasing their symptoms. Several helminth components are involved in the increasing of the allergic response and symptoms, overcoming the concomitant immunosuppression of helminthiases. However, the role of individual IgE-binding molecules in this process remains to be defined.

RECENT FINDINGS

We updated the list of helminth allergens and IgE-binding molecules, their effects on asthma presentation, and their impact on allergy diagnosis. Data from genetic and epigenetic studies of ascariasis are analyzed. A new species-specific A. lumbricoides allergen has been discovered, with potential use in molecular diagnosis. Most helminth IgE-binding components are not officially classified as allergens in the WHO/IUIS database, although there is evidence of their influence increasing allergic manifestations. Further immunological characterization of these components is needed to better understand their mechanisms of action and evaluate the ways in which they can influence the diagnosis of allergy.

Impact of helminth-microbiome interactions on childhood health and development-A clinical perspective

Humans have co-existed with parasites for virtually the entirety of our existence as a species. Today, nearly one third of the human population is infected with at least one helminthic species, most of which reside in the intestinal tract, where they have co-evolved alongside the human gut microbiota (GM). Appreciation for the interconnected relationship between helminths and GM has increased in recent years. Here, we review the evidence of how helminths and GM can influence various aspects of childhood development and the onset of paediatric diseases. We discuss the emerging evidence of how many of the changes that parasitic worms inflict on their host is enacted through gut microbes. In this light, we argue that helminth-induced microbiota modifications are of great importance in both facing the global challenge of overcoming parasitic infections, and in replicating helminthic protective effects against inflammatory diseases. We propose that deepening our knowledge of helminth-microbiota interactions will uncover novel, safer and more effective therapeutic strategies in combatting an array of childhood disorders.

Concurrent allergy and helminthiasis in underprivileged urban South African adults previously residing in rural areas

This study investigated whether prior exposure to helminths (Ascaris IgE, Ascaris eggs and Trichuris eggs) either in childhood or in adulthood, and residence in rural and resource‐limited urban areas influence allergy outcomes (asthma, rhinitis, IgE atopy and food allergy) in a South African population. Participants historical and present allergies data were collected through questionnaires and clinical record files. Coproscopy and immunoassays (ImmunoCAP^TM Phadiatop, total IgE and allergen‐specific fx3 IgE immunoassays and Ascaris IgE radioallergosorbent [RAST] tests) were used for active helminthiasis and allergy screens respectively. Data were analysed using logistic regression analysis, and models were adjusted for age, gender and locality. High Ascaris IgE was significantly associated with asthma (adjusted odds ratio [aOR] = 2.20, p = .047), IgE atopy (aOR = 18.18, p < .0001) and food allergy (aOR = 14.47, p < .0001). Asthma was significantly less likely among participants with Ascaris eggs (aOR = 0.43, p = .048) and Trichuris eggs (aOR = 0.36, p = .024). The findings of co‐occurrent helminthiasis and allergic disorders in a population that has resided both in rural and peri‐urban informal settlements both oppose and agree with two main notions of the hygiene hypothesis that (i) individuals residing in rural settings with poor sanitation and geohelminth infection are less prone to allergy, and (ii) helminth infections protect against allergy respectively. Further research is warranted.

Helminth infections and allergic diseases: systematic review and meta-analysis of the global literature

INTRODUCTION

There is considerable research interest in the role of helminth infections in the development of allergic diseases. However, findings from previous studies are mixed. Existing systematic reviews of these studies are outdated. We performed a systematic review of the global literature on the association between helminth infections and development and clinical outcomes of allergic diseases.

METHODS

We searched Cochrane Library, MEDLINE, EMBASE, ISI Web of Science, PubMed, Global Index Medicus, Scielo, KoreaMed, Google Scholar, and Lilacs for studies published up to January 2020. We included observational epidemiological studies (cohort, case-control and cross-sectional studies) of children and adults reporting associations between helminth infections and asthma, allergic rhinitis, eczema and atopy. We performed random-effects meta-analysis to summarize the effect estimates.

RESULTS

We included 80 studies with 99,967 participants. In the meta-analyses, we did not observe an overall association between helminth infections and allergic diseases. There was, however, evidence that A. lumbricoides infections was associated with an increased risk of bronchial hyperreactivity in children (RR:1.41, 95%CI: 1.17-1.70; I²=50, p for I²=0.09), and was associated with an increased risk of atopy among helminth-infected adults (RR:1.37, 95%CI: 1.18-1.61; I²=52, p for I²=0.02). We found no study that addressed the association between helminth infection and clinical outcomes of allergic diseases. The overall strength of the underlying evidence was low to moderate.

CONCLUSION

Helminth infections may increase the risk of bronchial hyperreactivity in children and atopy in adults. Well-designed longitudinal cohorts may help clarify potential causal associations between chronic helminth infections and allergic diseases.

Intestinal helminthic infection and allergic disorders among school children enrolled in mass deworming program, Sululta, Ethiopia

BACKGROUND

Intestinal helminths have been proposed to have a protective role against allergic sensitization and atopic diseases. However, consistent data demonstrating this are lacking in Sub-Saharan countries. We aimed to assess the association between intestinal helminths and allergic disorders among school children enrolled in mass deworming program in Sululta, Ethiopia.

METHODS

A cross sectional study was conducted among 526 school children aged 5 to 14 years old from primary government schools in Sululta district, Ethiopia. An interviewer-led questionnaire administered to parents provided information on demographic and lifestyle variables. Questions on allergic disease symptoms were collected using the International Study of Asthma and Allergies in Children (ISAAC) questionnaire 6 months following deworming treatments. Atopy was defined as a positive skin prick test reaction to one or both dust mite (Dermatophagoides) and German cockroach (Blatella germanica) allergens. Fresh stool samples were collected, processed, and examined by direct wet mount, Kato-Katz technique, and formol-ether concentration technique. Multivariate logistic regressions were used to assess the association between allergic disorder and helminths infection.

RESULTS

Of the total 526 school children, 58.2% were females. Overall, 24% (126/526) had allergic symptoms, 5.1% (27/526) had atopy, and 16.9% (89/526) had intestinal helminths. There was no association between helminthic infection and self-reported allergic symptoms (P = 0.317), but Ascaris lumbricoides infection was positively associated with atopy (AOR = 4.307, 95% CI 1.143-16.222, P = 0.031). Atopy was related to increased allergy symptoms (AOR = 2.787, 95% CI 1.253-6.197, P = 0.012), and family history of allergy was associated with increased childhood allergy (AOR = 2.753, 95% CI 1.565-4.841, P = 0.001). Deworming in the past 6 months showed a reduced odd of self-reported allergic symptoms (AOR = 0.581, 95% CI 0.366-0.954, P = 0.034).

CONCLUSION

While no significant association between self-reported allergy and helminths was found in this study, this may have been due to the low prevalence and intensity of helminthic infection in the sample. There was a positive association between Ascaris lumbricoides and atopy. To further examine the underlying mechanism behind this positive association, a longitudinal study is needed.

House dust mite sensitization drives cross-reactive immune responses to homologous helminth proteins

The establishment of type 2 responses driven by allergic sensitization prior to exposure to helminth parasites has demonstrated how tissue-specific responses can protect against migrating larval stages, but, as a consequence, allow for immune-mediated, parasite/allergy-associated morbidity. In this way, whether helminth cross-reacting allergen-specific antibodies are produced and play a role during the helminth infection, or exacerbate the allergic outcome awaits elucidation. Thus, the main objective of the study was to investigate whether house dust mite (HDM) sensitization triggers allergen-specific antibodies that interact with Ascaris antigens and mediate antibody-dependent deleterious effects on these parasites as well as, to assess the capacity of cross-reactive helminth proteins to trigger allergic inflammation in house dust mite presensitized mice. Here, we show that the sensitization with HDM-extract drives marked IgE and IgG1 antibody responses that cross-react with Ascaris larval antigens. Proteomic analysis of Ascaris larval antigens recognized by these HDM-specific antibodies identified Ascaris tropomyosin and enolase as the 2 major HDM homologues based on high sequence and structural similarity. Moreover, the helminth tropomyosin could drive Type-2 associated pulmonary inflammation similar to HDM following HDM tropomyosin sensitization. The HDM-triggered IgE cross-reactive antibodies were found to be functional as they mediated immediate hypersensitivity responses in skin testing. Finally, we demonstrated that HDM sensitization in either B cells or FcγRIII alpha-chain deficient mice indicated that the allergen driven cell-mediated larval killing is not antibody-dependent. Taken together, our data suggest that aeroallergen sensitization drives helminth reactive antibodies through molecular and structural similarity between HDM and Ascaris antigens suggesting that cross-reactive immune responses help drive allergic inflammation.

Epidemiological studies related to the interaction between allergies and helminth infection led to the observations that helped shape the so-called hygiene hypothesis, which generally states that chronic exposure to helminths diminishes the risk of the development of allergic disease. However, there are conflicting studies that have called this particular hypothesis into question, such as, the studies that suggest that infection with the helminth Ascaris lumbricoides is a risk factor for wheezing and atopy or can aggravate the clinical symptoms of asthma. A hypothetical explanation for such phenomenon is the fact that there is a high degree of molecular and structural similarities among helminth antigens with many common allergens, including the house dust mite (HDM). This high degree of homology of certain epitopes shared between helminths and allergens generate cross-react antibodies which may play a role in the pathogenesis or regulation of both conditions. Thus, this study aimed to understand the structural basis for cross-reactive antibodies induced by HDM sensitization. Here, we demonstrate that HDM sensitization drives helminth cross-reactive antibodies through molecular and structural homology between tropomyosins and enolases. This study highlights the pro-allergenic properties of HDM and helminth proteins that share homologous epitopes.

Mycobacterium-Induced Th1, Helminths-Induced Th2 Cells and the Potential Vaccine Candidates for Allergic Asthma: Imitation of Natural Infection

Bronchial asthma is one of the most chronic pulmonary diseases and major public health problems. In general, asthma prevails in developed countries than developing countries, and its prevalence is increasing in the latter. For instance, the hygiene hypothesis demonstrated that this phenomenon resulted from higher household hygienic standards that decreased the chances of infections, which would subsequently increase the occurrence of allergy. In this review, we attempted to integrate our knowledge with the hygiene hypothesis into beneficial preventive approaches for allergic asthma. Therefore, we highlighted the studies that investigated the correlation between allergic asthma and the two different types of infections that induce the two major antagonizing arms of T cells. This elucidation reflects the association between various types of natural infections and the immune system, which is predicted to support the main objective of the current research on investigating of the benefits of natural infections, regardless their immune pathways for the prevention of allergic asthma. We demonstrated that natural infection with Mycobacterium tuberculosis (Mtb) prevents the development of allergic asthma, thus Bacille Calmette-Guérin (BCG) vaccine is suggested at early age to mediate the same prevention particularly with increasing its efficiency through genetic engineering-based modifications. Likewise, natural helminth infections might inhabit the allergic asthma development. Therefore, helminth-derived proteins at early age are good candidates for designing vaccines for allergic asthma and it requires further investigation. Finally, we recommend imitation of natural infections as a general strategy for preventing allergic asthma that increased dramatically over the past decades.

Helminth Induced Immunoregulation and Novel Therapeutic Avenue of Allergy

Allergic diseases are increasing at an alarming rate worldwide, particularly in developed countries. In contrast, there is a decrease in the prevalence of helminthic infections and other neglected diseases. The hygiene hypothesis elaborates parasitic infection, and allergy-associated diseases have an inverse relationship. Acute helminthic infection and allergic reaction stimulate Type 2 helper cells (Th2) immune response with up-regulation of cytokines IL-4-, IL-5-, and IL-13-mediated IgE and mast cell production, as well as eosinophilia. However, people who chronically suffer from helminthic infections are demarcated through polarized Th2 resulting in alternative macrophage activation and T regulatory response. This regulatory system reduces allergy incidence in individuals that are chronically diseased through helminth. As a result, the excretory-secretory (ES) substance derived from parasites and extracellular vesicular components can be used as a novel therapeutic modality of allergy. Therefore, the aim of this review meticulously explored the link between helminth infection and allergy, and utilization of the helminth secretome for therapeutic immunomodulation.

Human Toxocara Infection: Allergy and Immune Responses

BACKGROUND

Toxocariasis is a cosmopolitan infection that occurs in various regions worldwide, more frequently in developing countries. Chronic infections with Toxocara species in humans are associated with the production of high levels of specific and non-specific antibodies of all isotypes and IgG subclasses and a cytokine response characterized by the production of Th2 cytokines including IL-4, IL-5 and IL-13 by Peripheral Blood Monocytes (PBMCs) and Leukocytes (PBLs) in whole blood cultures. Other Th2 effector responses are also prominent during infection, reflected by elevated numbers of peripheral blood eosinophils and increased expression of eosinophil degranulation products. The production of IFN-γ by PBMCs/PBLs stimulated with Toxocara-secreted proteins is not prominent in toxocariasis but IL-10 production may be increased in infected individuals. The relationship between Toxocara species with allergic reactions was reported in the recent century. Experimental and epidemiological investigations revealed that toxocariasis with this parasite led to the development of allergic symptoms, such as asthma. However, the findings are conflicting since in other investigations no association between these two immunopathologies has been reported.

CONCLUSION

The present review endeavours to summarize the data on Toxocara species and findings from studies on the relationship of toxocariasis with symptoms and signs of allergy. Furthermore, the mechanisms of immune responses and the factors associated between allergy and Toxocara infection are discussed.

Hookworms in Emergency Department: The ＂Vampire＂ Within

Hookworms infection is a soil-transmitted helminthic disease particularly endemic in developing counties of tropical regions. It is attributed mainly to two human pathogens nematodes namely Necator americanus and Ancylostoma duodenale. Although the disease has been characterized as "neglected" is very diffi cult to be eliminated and the economic consequences are great. Worms are fed with blood of hosts in small intestine and cause typically iron deficiency anemia with relevant symptoms as well as eosinophilia. Patients admitted in emergency department claim often diffuse general symptoms, whereas cases with obscure gastrointestinal bleeding can be seen. Within this brief review, after introducing some basic elements of hookworms' epidemiology, taxonomy and socioeconomic problem is emphasized, pathogenesis, and life cycle of parasite are concisely explained. Furthermore, clinical manifestations often or rarely seen in emergency department are described. Therapeutic options are also enclosed. Awareness of the problem and critical thinking of patients coming from endemic regions could result to identifying more hookworm cases and their therapy will efficiently alleviate not only the patients per se but health system and societies as well.

Helminth parasites and immune regulation

Helminth parasites are complex metazoans that belong to different taxonomic families but that collectively share the capacity to downregulate the host immune response directed toward themselves (parasite-specific immunoregulation). During long-standing chronic infection, these helminths appear able to suppress immune responses to bystander pathogens/antigens and atopic, autoimmune, and metabolic disorders. Helminth-induced immunoregulation occurs through the induction of regulatory T cells or Th2-type cells (or both). However, secreted or excreted parasite metabolites, proteins, or extracellular vesicles (or a combination of these) may also directly induce signaling pathways in host cells. Therefore, the focus of this review will be to highlight recent advances in understanding the immune responses to helminth infection, emphasizing the strategies/molecules and some of the mechanisms used by helminth parasites to modulate the immune response of their hosts.

Parasites and allergy: Observations from Brazil

Brazil is a middle-income country undergoing the epidemiological transition. Effects of changes in daily life habits and access to clean water, sanitation and urban services on a growing urban population have contributed to a double burden of both infectious and noncommunicable chronic diseases. Studies have indicated that parasite infections may modulate the human immune system and influence the development of allergic conditions such as asthma. However, there is no consensus in the published literature on the effects of parasitic infections on allergy, perhaps as a consequence of factors determining the epidemiology of these infections that vary between populations such as age of first infection, duration and chronicity of infections, parasite burden and species, and host genetic susceptibility. In this review, we discuss the observations from Brazil concerning the relationship between parasite infections and allergy.

Is childhood wheeze and asthma in Latin America associated with poor hygiene and infection? A systematic review

Introduction

High asthma prevalence in Latin-American cities is thought to be caused by poor hygiene and infections. This contradicts the widely accepted 'hygiene hypothesis' for asthma aetiology.

Methods

Systematic review of observational studies evaluating the association between poor hygiene exposures or infections and asthma/wheeze among Latin-American children aged 4-16 years. MEDLINE, EMBASE, LILACS and CINAHL electronic databases were searched following a predefined strategy to 18 December 2017. We quantified outcomes measured and reported, assessed risk of bias and tabulated the results.

Results

Forty-five studies included: 6 cohort, 30 cross-sectional and 9 case-control studies. 26 cross-sectional studies were school-based surveys (14 of over 3000 children), whereas 5 case-control studies were hospital/health centre-based. Exposures measured and reported varied substantially between studies, and current wheeze was the most common outcome reported. Data showed selective reporting based on statistical significance (P value <0.05): 17/45 studies did not clearly describe the number of exposures measured and 15/45 studies reported on less than 50% of the exposures measured. Most exposures studied did not show an association with wheeze or asthma, except for a generally increased risk associated with acute respiratory infections in early life. Contradictory associations were observed frequently between different studies.

Conclusion

Selective reporting is common in observational studies exploring the association between environmental exposures and risk of wheeze/asthma. This, together with the use of different study outcomes (wheeze/asthma) associated with possibly distinct causal mechanisms, complicates inferences about the role of poor hygiene exposures and childhood infections in explaining asthma prevalence in Latin-American children.

Opisthorchis felineus negatively associates with skin test reactivity in Russia-EuroPrevall-International Cooperation study

BACKGROUND

Most studies on the relationship between helminth infections and atopic disorders have been conducted in (sub)tropical developing countries where exposure to multiple parasites and lifestyle can confound the relationship. We aimed to study the relationship between infection with the fish-borne helminth Opishorchis felineus and specific IgE, skin prick testing, and atopic symptoms in Western Siberia, with lifestyle and hygiene standards of a developed country.

METHODS

Schoolchildren aged 7-11 years were sampled from one urban and two rural regions. Skin prick tests (SPT) and specific IgE (sIgE) against food and aeroallergens were measured, and data on allergic symptoms and on demographic and socioeconomic factors were collected by questionnaire. Diagnosis of opisthorchiasis was based on PCR performed on stool samples.

RESULTS

Of the 732 children included, 34.9% had opisthorchiasis. The sensitization to any allergen when estimated by positive SPT was 12.8%, while much higher, 24.0%, when measured by sIgE. Atopic symptoms in the past year (flexural eczema and/or rhinoconjunctivitis) were reported in 12.4% of the children. SPT was positively related to flexural eczema and rhinoconjunctivitis, but not to wheezing. Opisthorchiasis showed association with lower SPT response, as well as borderline association with low IgE reactivity to any allergen. However, the effect of opisthorchiasis on SPT response was not mediated by IgE, suggesting that opisthorchiasis influences SPT response through another mechanism. Opisthorchiasis also showed borderline association with lower atopic symptoms.

CONCLUSIONS

There is a negative association between a chronic helminth infection and skin prick test reactivity even in a developed country.

Hay fever, asthma, and eczema and early infectious diseases among children in Kilimanjaro, Tanzania

OBJECTIVES

To investigate the hygiene (or "old friends") hypothesis in a high-infectious disease (ID) environment, rural Kilimanjaro, Tanzania.

METHODS

Among a cross-sectional sample of 2- to 7-year-old children, we collected physician-diagnosed hay fever, asthma, and eczema, history of hospitalization, family size, and household environment information via questionnaire; performed active and passive surveillance for ID; and, evaluated total immunoglobulin E (IgE) and biomarkers of inflammation in dried blood spot specimens. We used regression models to describe patterns in allergic diseases.

RESULTS

Complete information was available for 280 children: 12.5% had been diagnosed with hay fever; 18.9% with eczema; 2.1% with asthma. There was a positive association between hay fever and eczema diagnoses (π² : 4.07; P = 0.044); total IgE was positively associated with eczema (β: 0.24; P = 0.100) and allergic diseases together (β: 0.26; P = 0.042). ID were common: the incidence of any ID diagnosis was 28 per 100 children per month. Hay fever was inversely associated with household animals (OR: 0.27; P = 0.006), and positively associated with earth housing materials (OR: 1.93; P = 0.079) and hospitalization in infancy with an ID (3.16; P = 0.066); patterns were similar when allergic disease outcomes were considered together. Few associations between these predictors and eczema or asthma alone were apparent.

CONCLUSIONS

Allergic diseases were common among children in Kilimanjaro. The inverse association between household animals and allergy is consistent with the hygiene/old friends hypothesis; however, positive associations between allergic diseases and earth housing materials and early hospitalization with ID bear further explanation.

Different clinical allergological features of Taenia solium infestation

The tapeworm Taenia (T.) solium can be responsible for two different conditions: taeniasis and cysticercosis. Helminth infections in human host cause an immune response associated with elevated levels of IgE, tissue eosinophilia and mastocytosis, and with the presence of CD4+ T cells that preferentially produce IL-4, IL-5, and IL-13. Individuals exposed to helminth infections may have allergic inflammatory responses to parasites and parasite antigens. PubMed search of human cases of allergic reactions occurring during T. solium infestation was performed combining the terms (allergy, urticaria, angioedema, asthma, anaphylaxis) with T. solium. A study was considered eligible for inclusion in the review if it reported data on patients with T. solium infestation who had signs or symptoms of allergy. In literature we found six articles reporting the association between an allergic reaction and T. solium infestation: two cases of urticaria, two cases of relapsing angioedema, one case of asthma and two cases of anaphylaxis. Despite the large diffusion of T. solium infestation, we found only a few cases of concomitant allergic reaction and the presence of Taenia in the host. The association between T. solium infestation and allergic manifestations has never been clearly demonstrated, and in absence of a well-documented causality the hypotheses are merely speculative. Therefore, the association between Taenia infection and allergy needs to be thoroughly studied to better clarify if this association may really exist and which is the pathogenetic mechanism supported.

The Hygiene Hypothesis and Its Inconvenient Truths about Helminth Infections

Current iterations of the hygiene hypothesis suggest an adaptive role for helminth parasites in shaping the proper maturation of the immune system. However, aspects of this hypothesis are based on assumptions that may not fully account for realities about human helminth infections. Such realities include evidence of causal associations between helminth infections and asthma or inflammatory bowel disease as well as the fact that helminth infections remain widespread in the United States, especially among populations at greatest risk for inflammatory and autoimmune diseases.

Human Helminths and Allergic Disease: The Hygiene Hypothesis and Beyond

There is much debate about the interaction between helminths and allergic disease. The "Hygiene Hypothesis," a very popular concept among scientists and the lay public, states that infections, especially during childhood, can protect against allergic diseases. Indeed, helminth infections are known to induce regulatory responses in the host that can help the control of inflammation (including allergic inflammation). However, these infections also induce type-2-associated immune responses including helminth-specific IgE that can cross-react against environmental allergens and mediate IgE-driven effector responses. Thus, it is the delicate balance between the parasites' anti- and pro-allergenic effects that define the helminth/allergy interface.

Allergic Sensitization Underlies Hyperreactive Antigen-Specific CD4+ T Cell Responses in Coincident Filarial Infection

Among the various hypotheses put forward to explain the modulatory influence of helminth infection on allergic effector responses in humans, the IL-10-induced suppression of Th2-associated responses has been the leading candidate. To explore this helminth/allergy interaction more fully, parasite- and allergen-specific CD4(+) T cell responses in 12 subjects with filarial infections, and coincident allergic sensitization (filarial [Fil](+)allergy [A](+)) were compared with the responses to three appropriate control groups (Fil(-)A(-) [n = 13], Fil(-)A(+) [n = 12], Fil(+)A(-) [n = 11]). The most important findings revealed that Fil(+)A(+) had marked (p < 0.0001 for all cytokines) increases in parasite Ag-driven Th2 (IL-4, IL-5, IL-13), Th9 (IL-9), and the regulatory (IL-10) cytokines when compared with Fil(+)A(-) Moreover, using multiparameter flow cytometry, filarial parasite Ag induced a marked increase in not only the frequency of CD4(+) T cells producing IL-4, IL-5, IL-2, and TNF-α in Fil(+)A(+) when compared with Fil(+)A(-) patients, but also in the frequencies of polyfunctional Th2-like (CD4(+)IL-4(+)IL-5(+) and CD4(+)IL-2(+)IL-4(+)IL-5(+)TNF-α(+)) cells. The Th2-associated responses seen in the Fil(+)A(+) group were correlated with serum IgE levels (p < 0.01, r = 0.5165 for IL-4; p < 0.001, r = 0.5544 for IL-5; and p < 0.001, r = 0.4901 for IL-13) and levels of circulating eosinophils (p < 0.0116, r = 0.5656) and their degranulation/activation products (major basic protein [p < 0.001, r = 0.7353] and eosinophil-derived neurotoxin [p < 0.01, r = 0.7059]). CD4(+) responses to allergen were not different (to a large extent) among the groups. Taken together, our data suggest that allergic sensitization coincident with filarial infection drives parasite Ag-specific T cell hyperresponsiveness, which is characterized largely by an augmented Th2-dominated immune response.

Identification and Characterization of IgE-Binding Tropomyosins in Aedes aegypti

BACKGROUND

The mosquito Aedes aegypti is a potential source of important clinically relevant allergens. However, the allergenicity and cross-reactivity of most of these has not been fully described.

METHODS

Natural wild-type mosquito tropomyosin was purified by size exclusion and anionic-exchange chromatography from an A. aegypti extract. Further characterization was accomplished by MALDI-TOF/TOF. Two recombinant variants of tropomyosin were obtained by expression in Escherichia coli. Specific IgE measurement by ELISA and skin tests for mosquito extract were performed in 12 patients with asthma or allergy rhinitis residing on the Caribbean island of Martinique. Cross-reactivity between natural A. aegypti tropomyosin and recombinant tropomyosins from A. aegypti, house dust mite, shrimp and Ascaris lumbricoides was analyzed by ELISA competition.

RESULTS

Four variants of natural tropomyosin were purified. A band of 32 kDa in SDS-PAGE representing 2 tropomyosin variants (Aed a 10.0101 and Aed a 10.0201) reacted with specific IgE of 4 of the 12 (33%) allergic patients and with rabbit polyclonal anti-shrimp tropomyosin. A high degree of cross-reactivity (60-70%) was detected between natural mosquito tropomyosin and Blo t 10, Der p 10 and Lit v 1, and a lower degree with Asc l 3 from A. lumbricoides (<30%). rAed a 10.0101 inhibited IgE binding to natural A. aegypti tropomyosin; however, rAed a 10.0201 showed a low inhibitory capacity.

CONCLUSION

Tropomyosin is a new IgE-binding protein from A. aegypti. Two of the 4 variants identified showed different degree of cross-reactivity with tropomyosins from other arthropods. The potential allergenic role of each variant should be further investigated.

Schistosome infection is negatively associated with mite atopy, but not wheeze and asthma in Ghanaian schoolchildren

BACKGROUND

Epidemiological evidence suggests that helminth infection and rural living are inversely associated with allergic disorders.

OBJECTIVE

The aim of the study was to investigate the effect of helminth infections and urban versus rural residence on allergy in schoolchildren from Ghana.

METHODS

In a cross-sectional study of 1385 children from urban-high socio-economic status (SES), urban-low SES and rural schools, associations between body mass index (BMI), allergen-specific IgE (sIgE), parasitic infections and allergy outcomes were analysed. Allergy outcomes were skin prick test (SPT) reactivity, reported current wheeze and asthma.

RESULTS

Helminth infections were found predominantly among rural subjects, and the most common were hookworm (9.9%) and Schistosoma spp (9.5%). Being overweight was highest among urban-high SES (14.6%) compared to urban-low SES (5.5%) and rural children (8.6%). The prevalence of SPT reactivity to any allergen was 18.3%, and this was highest among rural children (21.4%) followed by urban-high SES (20.2%) and urban-low SES (10.5%) children. Overall, SPT reactivity to mite (12%) was most common. Wheeze and asthma were reported by 7.9% and 8.3%, respectively. In multivariate analyses, factors associated with mite SPT were BMI (aOR 2.43, 95% CI 1.28-4.60, P = 0.007), schistosome infection (aOR 0.15, 95% CI 0.05-0.41) and mite sIgE (aOR 7.40, 95% CI 5.62-9.73, P < 0.001) but not area. However, the association between mite IgE and SPT differed by area and was strongest among urban-high SES children (aOR = 15.58, 95% CI 7.05-34.43, P < 0.001). Compared to rural, urban-low SES area was negatively associated with current wheeze (aOR 0.41, 95% CI 0.20-0.83, P = 0.013). Both mite sIgE and mite SPT were significantly associated with current wheeze and asthma.

CONCLUSION AND CLINICAL RELEVANCE

Infection with schistosomes appeared to protect against mite SPT reactivity. This needs to be confirmed in future studies, preferably in a longitudinal design where schistosome infections are treated and allergic reactions reassessed.

Helminth therapy or elimination: epidemiological, immunological, and clinical considerations

Deworming is rightly advocated to prevent helminth-induced morbidity. Nevertheless, in affluent countries, the deliberate infection of patients with worms is being explored as a possible treatment for inflammatory diseases. Several clinical trials are currently registered, for example, to assess the safety or efficacy of Trichuris suis ova in allergies, inflammatory bowel diseases, multiple sclerosis, rheumatoid arthritis, psoriasis, and autism, and the Necator americanus larvae for allergic rhinitis, asthma, coeliac disease, and multiple sclerosis. Studies in animals provide strong evidence that helminths can not only downregulate parasite-specific immune responses, but also modulate autoimmune and allergic inflammatory responses and improve metabolic homoeostasis. This finding suggests that deworming could lead to the emergence of inflammatory and metabolic conditions in countries that are not prepared for these new epidemics. Further studies in endemic countries are needed to assess this risk and to enhance understanding of how helminths modulate inflammatory and metabolic pathways. Studies are similarly needed in non-endemic countries to move helminth-related interventions that show promise in animals, and in phase 1 and 2 studies in human beings, into the therapeutic development pipeline.

Impact of periodic selective mebendazole treatment on soil-transmitted helminth infections in Cuban schoolchildren

OBJECTIVE

To evaluate the impact of periodic selective treatment with 500 mg mebendazole on soil-transmitted helminth (STH) infections in Cuban schoolchildren.

METHODS

We followed up a cohort of 268 STH-positive schoolchildren, aged 5-14 years at baseline, at six-month intervals for two years and a final follow-up after three years. Kato-Katz stool examination was used to detect infections with Ascaris lumbricoides, Trichuris trichiura and hookworm. Common risk factors related to STHs were assessed by parental questionnaire.

RESULTS

A significant reduction in the number of STH infections was obtained after three years with the highest reduction for T. trichiura (87.8%) and the lowest for hookworm (57.9%). After six months, cure rates (CRs) were 76.9% for A. lumbricoides, 67.4% for T. trichiura and 44.4% for hookworm. After two treatment rounds, more than 75% of all STH-positive children at baseline were cured, but with important differences between STH species (95.2% for A. lumbricoides, 80.5% for T. trichiura and 76.5% for hookworm). At the end of the study, these cumulative CRs were almost 100% for all three STHs. Risk factors for STHs were sex, sanitary disposal and habit of playing in the soil.

CONCLUSIONS

Our results indicate that periodic selective treatment with 500 mg mebendazole is effective in reducing the number of STH infections in Cuban schoolchildren. Although important differences were found between helminth species, two rounds of treatment appeared sufficient to obtain substantial reductions.

Parasitic worms and allergies in childhood: insights from population studies 2008-2013

The last few decades have seen a marked increase in the global prevalence of allergic diseases particularly among children. Among the factors attributed to this rise has been reduced exposure to pathogens during childhood leading to insufficient maturation of the regulatory arm of developing immune systems. Over the years, a number of epidemiological studies have observed an inverse relationship between parasitic worm (helminth) infections and allergies. The purpose of this review is to highlight insights from population studies conducted among children published between 2008 and 2013 that explore the complex dynamics between helminth infections and allergies. These insights include the effect of anthelmintic treatment on allergic responses, an elucidation of immune mechanisms and an examination of helminth-induced immunoglobulin E cross-reactivity. A better understanding of the relationship between helminths and allergies is imperative as research directions move toward harnessing the therapeutic potential of helminths and their products in the treatment of allergic disorders.

What are the main environmental exposures associated with elevated IgE in Cuban infants? A population-based study

OBJECTIVE

Immunoglobulin E (IgE) plays a key role in allergy disease pathogenesis, but little is known about the environmental factors associated with higher IgE levels in infants. The aim of this study was to determine the risk factors for elevated serum total IgE infants living in Havana.

METHODS

Eight hundred and seventy-seven infants provided blood samples. Data on allergic disease symptoms and a wide range of exposures were collected.

RESULTS

The median IgE was 35 IU/ml (interquartile range 13-96). The risk of having an IgE level above the median was higher for children who had been breastfed for 4 months or more (adjusted odds ratio (OR) 1.28; 95% confidence interval (CI): 1.02-1.61) and for children who reported cockroaches in their home (OR 1.30; 95% CI: 1.03-1.63). The risk was lower for children whose mother was in paid employment (OR 0.73; 95% CI: 0.54-0.97 compared with those who did not), for children living in homes where gas and electricity were used for cooking (OR 0.45; 95% CI: 0.32-0.62 compared with electricity only) and for children with domestic pets at birth (OR 0.83; 95% CI: 0.70-1.00). There was no association between paracetamol use and serum IgE levels.

CONCLUSIONS

Associations between gas fuel use and maternal employment indicate that IgE levels in early life are lower in children who may be living in relative affluence. The discrepancy in the effect of early exposure to pets or cockroaches may reflect differences in these allergens, or be confounded by relative affluence. Further investigation of this cohort will determine how these effects translate into the expression of allergic disease in later life.

Of worms, mice and man: an overview of experimental and clinical helminth-based therapy for inflammatory bowel disease

The incidence of inflammatory and autoimmune disorders is highest in well-developed countries which is directly related to their higher hygienic standards: it is suggested that the lack of exposure to helminths contributes to the susceptibility for immune-related diseases. Epidemiological, experimental and clinical data support the idea that helminths provide protection against immune-mediated diseases such as inflammatory bowel disease (IBD). The most likely mechanism for the suppression of immune responses by helminths is the release of helminth-derived immunomodulatory molecules. This article reviews the experimental and clinical studies investigating the therapeutic potential of helminth-based therapy in IBD and also focuses on the current knowledge of its immunomodulatory mechanisms of action highlighting innate as well as adaptive immune mechanisms. Identifying the mechanisms by which these helminths and helminth-derived molecules modulate the immune system will help in creating novel drugs for the treatment of IBD and other disorders that result from an overactive immune response.

Helminth Allergens, Parasite-Specific IgE, and Its Protective Role in Human Immunity

The Th2 immune response, culminating in eosinophilia and IgE production, is not only characteristic of allergy but also of infection by parasitic worms (helminths). Anti-parasite IgE has been associated with immunity against a range of helminth infections and many believe that IgE and its receptors evolved to help counter metazoan parasites. Allergens (IgE-antigens) are present in only a small minority of protein families and known IgE targets in helminths belong to these same families (e.g., EF-hand proteins, tropomyosin, and PR-1 proteins). During some helminth infection, especially with the well adapted hookworm, the Th2 response is moderated by parasite-expressed molecules. This has been associated with reduced allergy in helminth endemic areas and worm infection or products have been proposed as treatments for allergic conditions. However, some infections (especially Ascaris) are associated with increased allergy and this has been linked to cross-reactivity between worm proteins (e.g., tropomyosins) and highly similar molecules in dust-mites and insects. The overlap between allergy and helminth infection is best illustrated in Anisakis simplex, a nematode that when consumed in under-cooked fish can be both an infective helminth and a food allergen. Nearly 20 molecular allergens have been isolated from this species, including tropomyosin (Ani s 3) and the EF-hand protein, Ani s troponin. In this review, we highlight aspects of the biology and biochemistry of helminths that may have influenced the evolution of the IgE response. We compare dominant IgE-antigens in worms with clinically important environmental allergens and suggest that arrays of such molecules will provide important information on anti-worm immunity as well as allergy.

Enterobius vermicularis and allergic conditions in Norwegian children

Studies investigating the association between Enterobius vermicularis and allergic conditions have shown conflicting results. This study was conducted to test for any such associations in Norwegian children. Parents were asked to answer questionnaires concerning their children's history of allergies, wheezing or eczema and pinworm infections. Current pinworm infections were diagnosed by microscopic examination of anal scotch tape samples. The data were analysed using logistic regression. Atopic eczema, allergy or wheezing was reported to be confirmed by a physician in 23% of the children (84/364). A possible association between current pinworm infections and food allergy was found, with 17·5% of children without food allergy testing positive for pinworms, compared to 36·8% of children with food allergy (odds ratio 2·9, 95% confidence interval 1·1-8·0). No association was found between past pinworm treatments and present atopic conditions. The association between current E. vermicularis infections and food allergy warrants further study.

Allergic diseases and helminth infections

The relationships between allergic diseases and helminth infections are inconsistent. Some studies have suggested that helminth infections induce or increase the severity of atopic diseases. Other studies report that children infected with some helminths have lower prevalence and milder atopic symptoms. Expanding our knowledge on the mechanism of immunological modification as a result of helminth infection, and understanding the interaction between helminth infections and allergic diseases will be useful for developing potentially new treatments using some helminths, and for evaluating the risks and benefits of eradicating helminth infections in endemic areas. This article reviews current knowledge on the mechanisms of allergic disease, the immunological modifications that result from helminth infections, and clinical evidence of the effects of these infections on allergic diseases.

Update on the mapping of prevalence and intensity of infection for soil-transmitted helminth infections in Latin America and the Caribbean: a call for action

It is estimated that in Latin America and the Caribbean (LAC) at least 13.9 million preschool age and 35.4 million school age children are at risk of infections by soil-transmitted helminths (STH): Ascaris lumbricoides, Trichuris trichiura and hookworms (Necator americanus and Ancylostoma duodenale). Although infections caused by this group of parasites are associated with chronic deleterious effects on nutrition and growth, iron and vitamin A status and cognitive development in children, few countries in the LAC Region have implemented nationwide surveys on prevalence and intensity of infection. The aim of this study was to identify gaps on the mapping of prevalence and intensity of STH infections based on data published between 2000 and 2010 in LAC, and to call for including mapping as part of action plans against these infections. A total of 335 published data points for STH prevalence were found for 18 countries (11.9% data points for preschool age children, 56.7% for school age children and 31.3% for children from 1 to 14 years of age). We found that 62.7% of data points showed prevalence levels above 20%. Data on the intensity of infection were found for seven countries. The analysis also highlights that there is still an important lack of data on prevalence and intensity of infection to determine the burden of disease based on epidemiological surveys, particularly among preschool age children. This situation is a challenge for LAC given that adequate planning of interventions such as deworming requires information on prevalence to determine the frequency of needed anthelmintic drug administration and to conduct monitoring and evaluation of progress in drug coverage.

Soil-transmitted helminths (STH) are part of the group of neglected infectious diseases (NID) in Latin America and the Caribbean (LAC), and are associated with several adverse chronic effects on child health. Although control interventions such as periodic administration of anthelmintic drugs, health education, improved access to safe water and sanitation, among others, are acknowledged to be an important means to reduce morbidity and to achieve control, epidemiological information on prevalence status is lacking at the lowest sub-national administrative levels (municipalities, districts or provinces) in many countries thus hindering decision making regarding not only the treatment, but also the monitoring of progress in deworming coverage, the assessment of epidemiological impact on parasite prevalence and load and, therefore, the achievement of the overall public health goals. Epidemiological surveys can be expensive and require time and effort for their implementation, which could explain the low number of studies published with data on prevalence and intensity of infection in the Americas. The use of alternative methodologies, for instance those based on geographical information systems and remote sensing technologies, or of sentinel surveillance in schools may help countries in the task of collecting information and support the implementation of integrated control programs against STH.

Severity of atopic dermatitis and Ascaris lumbricoides infection: an evaluation of CCR4+ and CXCR3+ helper T cell frequency

INTRODUCTION

Ascaris lumbricoides-infected patients present lower prevalence of severe atopic dermatitis.

METHODS

Peripheral blood of infected children with atopic dermatitis was assessed by flow cytometry of the frequency of Th1 and Th2 cells through the expression of CXCR3 and CCR4 chemokine receptors, respectively.

RESULTS

Helminth-free patients with atopic dermatitis presented a high frequency of CCR4+Th2 cells. Parasitized patients with atopic dermatitis showed a lower frequency of CXCR3+Th1 cells compared to infected individuals only.

CONCLUSIONS

Ascariasis modifies the blood traffic of Th2 cells in atopic dermatitis patients, while the allergic disease down-regulates the traffic of Th1 cells in parasitized patients.

Toxocara seropositivity, atopy and asthma: a study in Cuban schoolchildren

INTRODUCTION

Evidence suggests that human toxocariasis (HT) could stimulate the onset of allergic diseases such as asthma. More specifically, in subjects having a hypothetical 'atopic genotype', HT could boost preexistent allergy symptoms. We tested the latter hypothesis in Cuba, a country where both asthma and HT are prevalent.

MATERIAL AND METHODS

In a group of Cuban school-aged children (n = 958), we investigated the association of Toxocara seropositivity and atopic status with asthma. Toxocara seropositivity was diagnosed with ELISA and atopy by allergen skin prick test. Both physician-diagnosed asthma and current wheeze, as determined by International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire, were considered. Associations were assessed using multivariable logistic regression analyses, with either 'physician-diagnosed asthma' or 'current wheeze' as outcome variable.

RESULTS

40.1% of the children were Toxocara seropositive. Prevalences were 21.7% for current wheeze and 32.7% for physician-diagnosed asthma. The odds of having asthma were almost two times higher in atopic children, but only reached borderline significance (OR=1.90, CI 95%: 0.95-3.80 for physician-diagnosed asthma and OR=1.94, CI 95%: 0.98-3.85 for current wheeze). Toxocara seropositivity and physician-diagnosed asthma were associated (OR=1.51, CI 95%: 1.01-2.26). Moreover, in children without antibodies to Toxocara, being atopic was significantly associated with having physician-diagnosed asthma (OR=2.53, CI 95%: 1.63-3.90), while this association was not present in Toxocara positives (OR=1.38, CI 95%: 0.82-2.37).

CONCLUSION

Our data confirm previous observations of higher Toxocara seropositivity rates in asthmatic children. Toxocara seropositivity appeared to abrogate the apparent association between atopy and asthma in Cuban children. Although this observation was limited to physician-diagnosed asthma, it challenges the hypothesis that HT stimulates the onset of allergic diseases such as asthma in atopic individuals.

Clonorchis sinensis infection is positively associated with atopy in endemic area

BACKGROUND

Epidemiologic studies have suggested that helminth infections play a protective role against allergy; this inverse association, however, has not been consistent. Clonorchis sinensis, the liver fluke of human, is prevalent in the Far East. The association between C. sinensis infection and allergy has not yet been reported.

OBJECTIVE

We evaluated the association between clonorchiasis and atopy or allergic diseases in adults in endemic areas of clonorchiasis.

METHODS

A total of 1116 subjects (males 419, females 697; age range, 30-86; mean age=61 years) were recruited from two endemic areas of C. sinensis in Korea. Clonorchiasis was confirmed by stool examination. Allergic symptoms were evaluated with a modified ISAAC questionnaire, and atopy was defined by skin prick test for common inhalant allergens. Total serum IgE and C. sinensis-specific IgE level was measured by ELISA and methacholine bronchial provocation test was performed to evaluate airway hyperresponsiveness (AHR).

RESULTS

Clonorchiasis was positively associated with atopy [odds ratio (OR), 1.856; 95% confidence interval (CI), 1.199-2.873] and high levels of total serum IgE (OR, 1.455; 95% CI, 1.050-2.016). Higher association with clonorchiasis was shown in subjects who showed both atopy and high total serum IgE levels (OR, 2.540; 95% CI, 1.448-4.455). Clonorchiasis had no association with wheezing, AHR, asthma or allergic rhinitis.

CONCLUSION AND CLINICAL RELEVANCE

Clonorchiasis was positively associated with atopy in adults in endemic area.

Helminth infection does not reduce risk for chronic inflammatory disease in a population-based cohort study

BACKGROUND & AIMS

Parasitic helminth infections can suppress symptoms of allergy, type 1 diabetes, arthritis, and inflammatory bowel disease in animal models. We analyzed data from a large, population-based cohort study to determine whether common childhood enterobiasis protects against these diseases.

METHODS

We collected information on individual prescriptions filled for the drug mebendazole against Enterobius vermicularis for all children born in Denmark 1995-2008 from the National Register of Medicinal Product Statistics (n = 924,749; age 0-14 years); 132,383 of these children (14%) filled a prescription for mebendazole, 102,482 of the children (11%) had a household peer who was registered with a filled mebendazole prescription, and the remaining 689,884 children (75%) comprised the reference group. Children diagnosed with asthma, type 1 diabetes, juvenile arthritis, ulcerative colitis, or Crohn's disease were identified from the National Patient Registry. We used Poisson regression to estimate confounder-adjusted incidence rate ratios for first in- or outpatient hospital diagnosis of chronic inflammatory disease according to history of mebendazole treatment prescribed to children in the study.

RESULTS

Chronic inflammatory disease was diagnosed in 10,352 children during 6.4 million person-years of follow-up. The incidence rate ratios was 1.07 for asthma (95% confidence interval [CI]: 1.00-1.13), 1.05 for type 1 diabetes (95% CI: 0.79-1.12), 1.13 for juvenile arthritis (95% CI: 0.94-1.37), 0.77 for ulcerative colitis (95% CI: 0.41-1.46), and 1.44 for Crohn's disease (95% CI: 0.82-2.53). Results were not modified by number of treatments or age at treatment.

CONCLUSIONS

Based on a population-based analysis, enterobiasis does not reduce risk for asthma, type 1 diabetes, arthritis, or inflammatory bowel disease.

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.

A study on the immunological basis of the dissociation between type I-hypersensitivity skin reactions to Blomia tropicalis antigens and serum anti-B. tropicalis IgE antibodies

Background

Two conditions are used as markers of atopy: the presence of circulating anti-allergen IgE antibodies and the presence of positive skin prick test (SPT) reactions to allergenic extracts. The correlation between these conditions is not absolute. This study aimed at investigating immunological parameters that may mediate this lack of correlation. Individuals whose sera contained anti-B. tropicalis extract IgE antibodies (α-BtE IgE) were divided into two groups, according to the presence or absence of skin reactivity to B. tropicalis extract (BtE). The following parameters were investigated: total IgE levels; α-BtE IgE levels; an arbitrary α-BtE IgE/total IgE ratio; the proportion of carbohydrate-reactive α-BtE IgE; the proportion of α-BtE IgE that reacted with Ascaris lumbricoides extract (AlE); the production of IL-10 by BtE- and AlE-stimulated peripheral blood cells (PBMC).

Results

Total IgE levels were similar in the two groups, but α-BtE IgE was significantly higher in the SPT-positive group (SPT+). A large overlap of α-BtE IgE levels was found in individuals of both groups, indicating that these levels alone cannot account for the differences in SPT outcome. Individuals of the two groups did not differ, statistically, in the proportion of α-BtE IgE that reacted with carbohydrate and in the production of IL-10 by BtE- and AlE-stimulated PBMC. Both groups had part of α-BtE IgE activity absorbed out by AlE, indicating the existence of cross-reactive IgE antibodies. However, the α-BtE IgE from the SPT-negative individuals (SPT-) was more absorbed with AlE than the α-BtE IgE from the SPT+ individuals. This finding may be ascribed to avidity differences of the α-BtE IgE that is present in the two groups of individuals, and could occur if at least part of the α-BtE IgE from the SPT- individuals were elicited by A. lumbricoides infection.

Conclusion

The present results suggest that a low ratio of specific IgE to total IgE levels (in a minority of individuals), and differences in α-BtE IgE avidities (which would have high affinities for A. lumbricoides antigens in SPT- than in SPT+ individuals) may play a role in the down-modulation of type-I hypersensitivity reaction against aeroallergens described in helminth-infected individuals.

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.

Structural and immunologic cross-reactivity among filarial and mite tropomyosin: implications for the hygiene hypothesis

BACKGROUND

The hygiene hypothesis suggests that parasitic infection modulates host immune responses and decreases atopy. Other data suggest parasitic infections may induce allergic responsiveness.

OBJECTIVE

To assess the structural and immunologic relationships between the known Dermatophagoides pteronyssinus (Der p 10) tropomyosin allergen and filarial tropomyosin of Onchocerca volvulus (OvTrop).

METHODS

The molecular, structural, and immunologic relationships between OvTrop and Der p 10 were compared. Levels of OvTrop-specific and Der p 10-specific IgE, IgG, and IgG₄ in sera of filaria-infected and filarial-uninfected D pteronyssinus-atopic individuals were compared, as were the responses in nonhuman primates infected with the filarial parasite Loa loa. Cross-reactivity was compared by antigen-mediated depletion assays and functionality by passive basophil sensitization.

RESULTS

Filarial and mite tropomyosins were very similar, with 72% identity at the amino acid level, and overlapping predicted 3-dimensional structures. The prevalence of IgE and IgG to Der p 10 was increased in filaria-infected individuals compared with uninfected subjects. There was a strong correlation between serum levels of Ov- and Der p 10-tropomyosin-specific IgE, IgG, and IgG₄ (P < .0001; r > 0.79). Preincubation of sera from anti-Der p 10-positive subjects with OvTrop completely depleted IgE, IgG, and IgG₄ anti-Der p 10. Basophils sensitized with sera from individuals allergic to Der p 10 released histamine similarly when triggered with OvTrop or Der p 10. Primates experimentally infected with L loa developed IgE that cross-reacted with Der p 10.

CONCLUSION

Filarial infection induces strong cross-reactive antitropomyosin antibody responses that may affect sensitization and regulation of allergic reactivity.

The presence of serum anti-Ascaris lumbricoides IgE antibodies and of Trichuris trichiura infection are risk factors for wheezing and/or atopy in preschool-aged Brazilian children

BACKGROUND

The elucidation of factors that trigger the development of transient wheezing in early childhood may be an important step toward understanding the pathogenesis of asthma and other allergic diseases later in life. Transient wheezing has been mainly attributed to viral infections, although sensitisation to aeroallergens and food allergens may occur at an early age. In developing countries, intestinal helminthic infections have also been associated with allergy or atopy-related disorders.

OBJECTIVE

The aim of this study was to explore the association of Trichuris trichiura and Ascaris lumbricoides infections with wheezing and atopy in early childhood.

STUDY DESIGN

A cross-sectional study using a Portuguese-language ISAAC phase I questionnaire, adapted for preschool-aged children, nested in a cohort study of childhood diarrhoea, was conducted on 682 children. Two faecal samples per child were examined for the presence of intestinal helminthic infection. IgE antibodies against three allergenic preparations (Dermatophagoides pteronyssinus, Blomia tropicalis and common child food), as well as against A. lumbricoides antigens, were measured in a sub-sample of these children, whose parents allowed the procedure. Atopy was defined by the presence of levels of serum IgE antibodies ≥0.35 kU/L against at least one of the three tested allergenic preparations.

RESULTS

Active T. trichiura infection but not A. lumbricoides infection was positively associated with wheezing in the total studied children population [adjusted OR = 2.60; CI = 1.54;4.38] and in the atopic children sub-population [adjusted OR = 3.07; CI = 1.00;9.43]. The association with atopy was also positive and statistically significant only in the brute analysis [OR = 2.13; CI = 1.03;4.40]. Anti-A. lumbricoides IgE antibodies, but not current A. lumbricoides infection, were positively associated with wheezing in atopic children [adjusted OR = 2.01; CI = 1.00;4.50] and in non-atopic children [adjusted OR = 3.07; CI = 1.13;8.35] and it was also associated with atopy [adjusted OR = 7.29; CI = 3.90; 13.4]. On the other hands, reports of wheezing were not significantly associated with atopy.

CONCLUSIONS

These data corroborate previous studies showing that wheezing is predominantly associated with infection in early childhood and shows that anti-A. lumbricoides IgE antibodies, but not active Ascaris infections, are associated with wheezing and atopy. Additionally, the data demonstrate that T. trichiura infection may play a role in the pathogenesis of atopic wheezing in early childhood.

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.

Interactions between helminth parasites and allergy

PURPOSE OF REVIEW

To review the findings of recent human studies of the association between helminth parasite infections and allergy and discuss their potential relevance to public health.

RECENT FINDINGS

Different helminth parasites may have different effects on allergy that may depend on the timing or intensity of the exposure or host genetic factors. Infections with Trichuris trichiura in early life are associated with a reduced prevalence of allergen skin test reactivity later in life and infants of helminth-infected mothers have been reported to have a reduced prevalence of eczema. Hookworm infection has been associated with a reduced prevalence of asthma in Ethiopia. Several studies have reported that anti-Ascaris IgE is an important risk factor for asthma, but this could be explained by an enhanced ability of atopics to produce IgE. Toxocara infections may be associated with an increased risk of wheeze in some populations that may be caused by the host response to the parasite or by parasite-enhanced Th2 responses to aeroallergens.

SUMMARY

Although helminth infections can modulate the host inflammatory response directed against the parasite, a causal association between helminths and atopic diseases remains uncertain.

Gastrointestinal nematode infection interferes with experimental allergic airway inflammation but not atopic dermatitis

BACKGROUND

Some helminth infections are negatively associated with the prevalence of allergic disorders, arguing for a modulation of allergic reactions by the parasites, depending on the worm species, intensity and phase of infection and the type of disease.

OBJECTIVE

The aim of this study was to analyse the influence of a chronic infection with the gastrointestinal nematode Heligmosomoides polygyrus, in a murine model of allergic airway disease and of atopic dermatitis (AD), respectively.

METHODS

Mice were infected with H. polygyrus and systemically sensitized with the model allergen ovalbumin. Subsequently, the animals were challenged with the allergen either via the airways for induction of airway disease, or via skin patches for induction of dermatitis.

RESULTS

Mice concomitantly infected with H. polygyrus showed diminished eosinophil and lymphocyte recruitment into the lungs and decreased allergen-specific IgE levels when compared with sensitized and airway challenged controls. In addition, animals showed a trend towards reduced airway hyper-reactivity. In contrast, no significant differences in the severity of eczematous skin lesions were observed between infected and control animals in the AD model. Although H. polygyrus infection reduced CD8+ and CD4+ T-cell infiltration into the skin and production of allergen-specific IgE, mast cell recruitment was significantly increased in worm-infected mice in the dermatitis model. The worm infection was associated with significantly elevated numbers of Foxp3+ regulatory T cells (Treg) in peribronchial lymph nodes in H. polygyrus-infected sensitized and airway challenged mice. In contrast, Treg cells were basically absent in eczematous skin and their number was not increased in skin-draining lymph nodes of mice with experimental dermatitis.

CONCLUSION

Infection with the gastrointestinal nematode used in our study leads to significant inhibition of mucosa-associated but not cutaneous allergic reactions, pointing to a site specificity of the immunomodulation exerted by helminths. This finding might be an important aspect for future considerations of helminths for treatment of allergic diseases.

Rural dermatology in the tropics

Rural dermatology in the tropics is determined by socioeconomic factors, climate, and skin type. Lack of interest of the profession leads to late and inadequate diagnosis and treatment. No proper data on the magnitude of the problem are available, even though a great number of the world population live under those conditions. This contribution provides an overview of the most common skin diseases, in particular, infections and infestations. Other skin conditions, both eczematous and immune-mediated, that are typical for the rural tropics also are discussed. Etiology, pathology, and treatments are presented against the socioeconomic background.