IgE cross-reactivity between Ascaris and domestic mite allergens: the role of tropomyosin and the nematode polyprotein ABA-1

Identification of rBlo t 41 with a chitin-binding type-2 domain: A novel major allergen from Blomia tropicalis

BACKGROUND

Blomia tropicalis (B. tropicalis) has been reported to impose an increased risk of allergic diseases. However, few characteristics of the unknown allergen components responsible for B. tropicalis allergy and clinical relevance have been fully identified.

METHODS

We synthesized and characterized the physicochemical properties and cross-reactivity of the newly discovered recombinant B. tropicalis group 41 allergen (rBlo t 41). Subsequently, sera were collected from 107 B. tropicalis allergic subjects to evaluate the prevalence of the rBlo t 41. Lastly, its allergenicity was tested in humans by basophil activation assays, and in mice by a model of allergic asthma.

RESULTS

The mature protein of rBlo t 41 was described as 104 amino acids long and 15.8 kDa, and its limited cross-reactivity was observed between allergens of house dust mites (HDM). Sensitization rate of rBlo t 41 (56.07 %) was lower than rBlo t 2 (76.29 %) and rBlo t 5 (69.07 %) in our study. Besides, rBlo t 41 elicited CD63 upregulation in basophils, whereas rBlo t 41-sensitized mice generated rBlo t 41-IgE and developed allergic airway inflammation after allergen exposure. Of note, component-based tests showed a high area under curve value (AUC = 0.75) of rBlo t 41, displaying its favorable diagnostic potential in B. tropicalis allergy.

CONCLUSIONS

rBlo t 41 was identified as a candidate novel major allergen with good diagnostic potential in B. tropicalis sensitization. Additionally, we provided strong evidence about rBlo t 41 on the clinically relevant manifestations in B. tropicalis allergies, conducive to facilitating the development of component-resolved diagnosis.

What's childhood asthma in French Guiana? A cohort study based on children referred for allergology consultations at the Cayenne hospital center

Background

Asthma is a multifactorial chronic disease, whose most frequent etiology is allergy, especially to Blomia tropicalis. In French Guiana, the childhood prevalence of Blomia T sensitization is unkwown. The aim of this study was to determine the proportion of sensitization to Blomia T and other mites in asthmatic children, and to describe the characteristics of childhood asthma in French Guiana.

Methods

A retrospective cohort study focused on children from 0 to 18 years of age, followed for asthma at the Department of Pediatrics of the Cayenne Hospital Center in French Guiana. All asthmatic children followed by the same paediatric allergist were systematically skin-tested with Bt total extract, and Bt-specific IgE tests were additionally performed to confirm specific sensitization. All follow-up variables were collected from medical records. The outcome was sensitization to Blomia tropicalis and other allergens, and the explanatory variables were those of asthma follow-up. Patients were categorized into Blomia tropicalis sensitization yes/no. Logistic regression analysis was used to assess the relationship between follow-up variables and the outcome.

Results

302 patients were followed: 177 cases of allergic rhinitis, 135 allergic conjunctivitis, 105 atopic dermatitis, 153 food allergy, and 14 cases of drug allergy. Poly-allergy (respiratory, food, skin, and medicinal) was present in 239 children. There were 158 children followed for asthma, of whom 103 (65%) were sensitized to Blomia tropicalis. The median age of the asthmatic children sensitized to Blomia tropicalis was 7 years, and 3 years for those who were not sensitized (p < 0.001). Among the girls (n = 58), 67% were sensitized to Blomia; 97 (92%) asthmatic children co-sensitized to Blomia tropicalis, Dermatophagoides pteronyssinus, and Dermatophagoides farinae. Multivariate analysis showed that the childhood asthma in French Guiana is characterized by a median age of 7 years (p < 0.001), a high prevalence of Blomia tropicalis (p < 0.001), co-sensitization to other mites (p < 0.001), and a high prevalence of co-sensitization to cockroaches (p = 0.006). The area under the ROC curve was close to 0.9, confirming the quality of our model.

Conclusion

In French Guiana, asthma is characterized by a high prevalence of Blomia tropicalis sensitization.

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.

Frequent IgE recognition of Blomia tropicalis allergen molecules in asthmatic children and young adults in equatorial Africa

Background

Asthma is not well investigated in equatorial Africa and little is known about the disease-associated allergen molecules recognized by IgE from patients in this area. The aim was to study the molecular IgE sensitization profile of asthmatic children and young adults in a semi-rural area (Lambaréné) of an equatorial African country (Gabon), to identify the most important allergen molecules associated with allergic asthma in equatorial Africa.

Methods

Fifty-nine asthmatic patients, mainly children and few young adults, were studied by skin prick testing to Dermatophagoides pteronyssinus (Der p), D. farinae (Der f), cat, dog, cockroach, grass, Alternaria and peanut. Sera were obtained from a subset of 35 patients, 32 with positive and 3 with negative skin reaction to Der p and tested for IgE reactivity to 176 allergen molecules from different allergen sources by ImmunoCAP ISAC microarray technology and to seven recombinant Blomia tropicalis (Blo t) allergens by IgE dot blot assay.

Results

Thirty-three of the 59 patients (56%) were sensitized to Der p and 23 of them (39%) were also sensitized to other allergen sources, whereas 9 patients (15%) were only sensitized to allergen sources other than Der p. IgE serology analyses (n=35) showed high IgE-binding frequencies to the Blo t allergens Blo t 5 (43%), Blo t 21 (43%) and Blo t 2 (40%), whereas the Der p allergens rDer p 2, rDer p 21 and rDer p 5 (34%, 29% and 26%) were less frequently recognized. Only few patients showed IgE reactivity to allergens from other allergen sources, except to allergens containing carbohydrate determinants (CCDs) or to wasp venom allergens (i.e., antigen 5).

Conclusion

Our results thus demonstrate that IgE sensitization to mite allergens is very prevalent in asthmatics in Equatorial Africa with B. tropicalis allergen molecules representing the most important ones associated with allergic asthma.

House dust mite allergy: The importance of house dust mite allergens for diagnosis and immunotherapy

House dust mite (HDM) allergy belongs to the most important allergies and affects approximately 65-130 million people worldwide. Additionally, untreated HDM allergy may lead to the development of severe disease manifestations such as atopic dermatitis or asthma. Diagnosis and immunotherapy of HDM allergic patients are well established but are often hampered by the use of mite extracts that are of bad quality and lack important allergens. The use of individual allergens seems to be a promising alternative to natural allergen extracts, since they represent well-defined components that can easily be produced and quantified. However, a thorough characterization of the individual allergens is required to determine their clinical relevance and to identify those allergens that are required for correct diagnosis of HDM allergy and for successful immunotherapy. This review gives an update on the individual HDM allergens and their benefits for diagnosis and immunotherapy of HDM allergic patients.

EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

Excretory/Secretory Proteome of Females and Males of the Hookworm Ancylostoma ceylanicum

The dynamic host-parasite mechanisms underlying hookworm infection establishment and maintenance in mammalian hosts remain poorly understood but are primarily mediated by hookworm's excretory/secretory products (ESPs), which have a wide spectrum of biological functions. We used ultra-high performance mass spectrometry to comprehensively profile and compare female and male ESPs from the zoonotic human hookworm Ancylostoma ceylanicum, which is a natural parasite of dogs, cats, and humans. We improved the genome annotation, decreasing the number of protein-coding genes by 49% while improving completeness from 92 to 96%. Compared to the previous genome annotation, we detected 11% and 10% more spectra in female and male ESPs, respectively, using this improved version, identifying a total of 795 ESPs (70% in both sexes, with the remaining sex-specific). Using functional databases (KEGG, GO and Interpro), common and sex-specific enriched functions were identified. Comparisons with the exclusively human-infective hookworm Necator americanus identified species-specific and conserved ESPs. This is the first study identifying ESPs from female and male A. ceylanicum. The findings provide a deeper understanding of hookworm protein functions that assure long-term host survival and facilitate future engineering of transgenic hookworms and analysis of regulatory elements mediating the high-level expression of ESPs. Furthermore, the findings expand the list of potential vaccine and diagnostic targets and identify biologics that can be explored for anti-inflammatory potential.

Risk Factors Associated With Health Care Utilization in Preschool Recurrent Wheezers in a Tropical Environment

Introduction: The severity of wheezing episodes is related with the need for health services, but the factors associated with health care utilization in preschool recurrent wheezers in underdeveloped regions are unclear.

Objective: To evaluate the factors associated with health care utilization in preschool recurrent wheezers in Cartagena, Colombia.

Methods: One hundred twenty-seven recurrent wheezers (age 2–6 years old) who were admitted to the emergency room (ER) due to wheezing in a Pediatric reference hospital in Cartagena were included. Children were evaluated by means of questionnaires and classified according to the number of ER visits, need for hospitalization and history of intensive care unit (ICU) admission due to wheezing within the last year. Total serum IgE and specific IgE to house dust mite allergens (HDM) were measured by ImmunoCAP® and allergen sensitization was evaluated by skin prick tests (SPT).

Results: The maternal report of nocturnal cough without fever in their children increased the risk to have ≥5 ER visits in the last year due to wheezing. The use of montelukast was negatively associated with hospitalization, while a history of pneumonia and lack of tap water, increased the risk of hospitalization due to wheezing. A history of bronchiolitis, family history of asthma, cohabiting with two or more siblings, passive exposure to smoke and lack of sewage facilities increased the risk of ICU admission due to wheezing. The presence of atopy evaluated by SPT reactivity, total IgE levels or specific IgE to HDM were not associated with health care utilization. We also found that seroprevalence of positive IgE (≥0.35 kU/L) was 27% to B. tropicalis and 20.3% to D. pteronyssinus but the prevalence of positive IgE sensitization to these allergens was below 2% and 8% when evaluated by SPT, respectively.

Conclusions: Poverty indicators are associated with ICU admission in a group of preschool recurrent wheezers and should be considered as aggravating factors for wheezing. These factors must be systematically assessed in the medical approach in underdeveloped regions in the tropics. Nocturnal cough without fever is a symptom associated with frequent ER visits while atopy was not associated with health care utilization in preschool recurrent wheezers.

Presence of IgE Autoantibodies Against Eosinophil Peroxidase and Eosinophil Cationic Protein in Severe Chronic Spontaneous Urticaria and Atopic Dermatitis

Purpose

Eosinophils are frequently found in atopic dermatitis (AD) and chronic spontaneous urticaria (CSU) that release eosinophil peroxidase (EPX) and eosinophil cationic protein (ECP). Continuous exposure to these proteins could trigger an autoimmune response which may contribute to the pathogenesis and severity of skin inflammation. In this study, we investigate the immunoglobulin E (IgE) response against eosinophil proteins in CSU and AD.

Methods

We recruited patients with severe AD, severe CSU and healthy subjects to explore the presence of IgE autoantibodies and cross-reactivity against EPX, ECP and thyroid peroxidase (TPO). The potential cross-reactive epitopes among the peroxidase family were determined using in silico tools.

Results

The frequencies of anti-EPX IgE (28.8%) and anti-ECP IgE (26.6%) were higher in the AD group, and anti-TPO IgE was higher in the CSU group (27.2%). In the CSU group, there was a correlation between the anti-EPX IgE and anti-TPO IgE levels (r = 0.542, P < 0.001); TPO inhibited 42% of IgE binding to EPX, while EPX inhibited 59% of IgE binding to TPO, suggesting a cross-reactivity with EPX as a primary sensitizer. There was greater inhibition when we used a pool of sera CSU and AD, TPO inhibited 52% of IgE binding to EPX, while EPX inhibited 78% of IgE binding to TPO. In silico analysis showed a possible shared epitope in the peroxidase protein family.

Conclusions

IgE against eosinophil proteins may contribute to chronic inflammation in patients with AD and CSU. Cross-reactivity between EPX and TPO could explain thyroid problems in CSU patients.

Patterns of allergic sensitization and factors associated with emergence of sensitization in the rural tropics early in the life course: findings of an Ecuadorian birth cohort

Introduction

There are limited data on emergence of allergic sensitization (or atopy) during childhood in tropical regions.

Methods

We followed a birth cohort of 2404 newborns to 8 years in tropical Ecuador and collected: risk factor data by maternal questionnaires periodically from birth; atopy was measured by skin prick test reactivity (SPT) to aeroallergens in parents, and aeroallergens and food allergens in children at 2, 3, 5, and 8 years; and stool samples for soil-transmitted helminths (STH) from children periodically to 8 years and from parents and household members at the time of recruitment of cohort children. Data on risk factors were measured either at birth or repeatedly (time-varying) from birth to 8 years. Longitudinal repeated-measures analyses were done using generalized estimating equations to estimate an the age-dependent risk of positive SPT (SPT+) to any allergen or mite during early childhood to school age.

Results

SPT+ to any allergen was present in 29.0% of fathers and 24.8% of mothers, and in cohort children increased with age, initially to mite but later to cockroach, reaching 14.8% to any allergen (10.7% mite and 5.3% cockroach) at 8 years. Maternal SPT+, particularly presence of polysensitization (OR 2.04, 95% CI 1.49-2.77) significantly increased the risk of SPT+ during childhood, while household overcrowding at birth decreased the risk (OR 0.84, 95% CI 0.72-0.98). For mite sensitization, maternal polysensitization increased (OR 2.14, 95% CI 1.40-3.27) but rural residence (OR 0.69, 95% CI 0.50-0.94) and birth order (3^rd -4^th vs. 1^st - 2^nd: OR 0.71, 95% CI 0.52-0.98) decreased the risk. Time-varying exposures to agricultural activities (OR 0.77, 95% CI 0.60-0.98) and STH parasites (OR 0.70, 95% CI 0.64-0.91) during childhood decreased while anthelmintics increased the childhood risk (OR 1.47, 95% CI 1.05-2.05) of mite sensitization.

Conclusion

Our data showed the emergence of allergic sensitization, primarily to mite and cockroach allergens, during childhood in tropical Ecuador. A role for both antenatal and postnatal factors acting as potential determinants of SPT+ emergence was observed.

Mosquitoes: Important Sources of Allergens in the Tropics

There are more than 3,000 mosquito species. Aedes aegypti, Ae. communis, and C. quinquefasciatus are, among others, three of the most important mosquito allergen sources in the tropics, western, and industrialized countries. Several individuals are sensitized to mosquito allergens, but the epidemiological data indicates that the frequency of sensitization markedly differs depending on the geographical region. Additionally, the geographical localization of mosquito species has been affected by global warming and some mosquito species have invaded areas where they were not previously found, at the same time as other species have been displaced. This phenomenon has repercussions in the pathogenesis and the accuracy of the diagnosis of mosquito allergy. Allergic individuals are sensitized to mosquito allergens from two origins: saliva and body allergens. Exposure to saliva allergens occurs during mosquito bite and induces cutaneous allergic reactions. Experimental and clinical data suggest that body allergens mediate different manifestations of allergic reactions such as asthma and rhinitis. The most studied mosquito species is Ae. aegypti, from which four and five allergens of the saliva and body, respectively, have been reported. Many characterized allergens are homologs to arthropod-derived allergens, which cause strong cross-reactivity at the humoral and cellular level. The generalized use of whole body Ae. communis or C. quinquefasciatus extracts complicates the diagnosis of mosquito allergy because they have low concentration of saliva allergens and may result in poor diagnosis of the affected population when other species are the primary sensitizer. This review article discusses the current knowledge about mosquito allergy, allergens, cross-reactivity, and proposals of component resolved approaches based on mixtures of purified recombinant allergens to replace saliva-based or whole-body extracts, in order to perform an accurate diagnosis of allergy induced by mosquito allergen exposure.

Allergological Importance of Invertebrate Glutathione Transferases in Tropical Environments

Glutathione-S transferases (GSTs) are part of a ubiquitous family of dimeric proteins that participate in detoxification reactions. It has been demonstrated that various GSTs induce allergic reactions in humans: those originating from house dust mites (HDM), cockroaches, and helminths being the best characterized. Evaluation of their allergenic activity suggests that they have a clinical impact. GST allergens belong to different classes: mu (Blo t 8, Der p 8, Der f 8, and Tyr p 8), sigma (Bla g 5 and Asc s 13), or delta (Per a 5). Also, IgE-binding molecules belonging to the pi-class have been discovered in helminths, but they are not officially recognized as allergens. In this review, we describe some aspects of the biology of GST, analyze their allergenic activity, and explore the structural aspects and clinical impact of their cross-reactivity.

Immunological underpinnings of Ascaris infection, reinfection and co-infection and their associated co-morbidities

Human ascariasis is the most common and prevalent neglected tropical disease and is estimated that ~819 million people are infected around the globe, accounting for 0.861 million years of disability-adjusted life years in 2017. Even with the existence of highly effective drugs, the constant presence of infective parasite eggs in the environment contribute to a high reinfection rate after treatment. Due to its high prevalence and broad geographic distribution Ascaris infection is associated with a variety of co-morbidities and co-infections. Here, we provide data from both experimental models and humans studies that illustrate how complex is the interaction of Ascaris with the host immune system, especially, in the context of reinfections, co-infections and associated co-morbidities.

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.

Identification and Physicochemical Characterization of a New Allergen from Ascaris lumbricoides

To analyze the impact of Ascaris lumbricoides infection on the pathogenesis and diagnosis of allergic diseases, new allergens should be identified. We report the identification of a new Ascaris lumbricoides allergen, Asc l 5. The aim of this study was to evaluate the physicochemical and immunological features of the Asc l 5 allergen. We constructed an A. lumbricoides cDNA library and Asc l 5 was identified by immunoscreening. After purification, rAsc l 5 was physicochemically characterized. Evaluation of its allergenic activity included determination of Immunoglobulin E (IgE) binding frequency (in two populations: 254 children and 298 all-age subjects), CD203c based-basophil activation tests (BAT) and a passive cutaneous anaphylaxis (PCA) mouse model. We found by amino acid sequence analysis that Asc l 5 belongs to the SXP/RAL-2 protein family of nematodes. rAsc l 5 is a monomeric protein with an alpha-helical folding. IgE sensitization to rAsc l 5 was around 52% in general population; positive BAT rate was 60%. rAsc l 5 induced specific IgE production in mice and a positive PCA reaction. These results show that Asc l 5 has structural and immunological characteristics to be considered as a new allergen from A. lumbricoides.

Proteomic analysis of Ascocotyle longa (Trematoda: Heterophyidae) metacercariae

Ascocotyle longa is parasitic trematode with wide distribution throughout America, Europe, Africa, and Middle East. Despite the fact that this fish-borne pathogen has been considered an agent of human heterophyiasis in Brazil, the molecules involved in the host-parasite interaction remain unknown. The present study reports the proteome profile of A. longa metacercariae collected from the fish Mugil liza from Brazil. This infective stage for humans, mammals and birds was analyzed using nLC-MS/MS approach. We identified a large repertoire of proteins, which are mainly involved in energy metabolism and cell structure. Peptidases and immunogenic proteins were also identified, which might play roles in host-parasite interface. Our data provided unprecedented insights into the biology of A. longa and represent a first step to understand the natural host-parasite interaction. Moreover, as the first proteome characterized in this trematode, it will provide an important resource for future studies.

Personalized medicine for asthma in tropical regions

PURPOSE OF REVIEW

Precision medicine could help to improve diagnosis and treatment of asthma; however, in the tropics there are special conditions to be considered for applying this strategy. In this review, we analyze recent advances of precision allergology in tropical regions, highlighting its limitations and needs in high-admixed populations living under environments with high exposure to house dust mites and helminth infections.

RECENT FINDINGS

Advances have been made regarding the genetic characterization of the great diversity of populations living in the tropics. Genes involved in shared biological pathways between immune responses to nematodes and the allergic responses suggested new mechanisms of predisposition. Genome wide association studies of asthma are progressively focusing on some highly replicated genes such as those in chromosome 17q31-13, which have been also replicated in African ancestry populations. Some diagnostic difficulties, because of the endemicity of helminth infections, are now more evident in the context of phenotype definition.

SUMMARY

The clinical impact of the advances in precision medicine for asthma in the tropics is still limited and mainly related to component resolved diagnosis. More basic and clinical research is needed to identify genetic, epigenetic, or other biologic markers that allow and accurate definition of phenotypes and endotypes of this heterogeneous disease. This will substantially improve the selection of personalized treatments.

The allergenic activity and clinical impact of individual IgE-antibody binding molecules from indoor allergen sources

A large number of allergens have been discovered but we know little about their potential to induce inflammation (allergenic activity) and symptoms. Nowadays, the clinical importance of allergens is determined by the frequency and intensity of their IgE antibody binding (allergenicity). This is a rather limited parameter considering the development of experimental allergology in the last 20 years and the criteria that support personalized medicine. Now it is known that some allergens, in addition to their IgE antibody binding properties, can induce inflammation through non IgE mediated pathways, which can increase their allergenic activity. There are several ways to evaluate the allergenic activity, among them the provocation tests, the demonstration of non-IgE mediated pathways of inflammation, case control studies of IgE-binding frequencies, and animal models of respiratory allergy. In this review we have explored the current status of basic and clinical research on allergenic activity of indoor allergens and confirm that, for most of them, this important property has not been investigated. However, during recent years important advances have been made in the field, and we conclude that for at least the following, allergenic activity has been demonstrated: Der p 1, Der p 2, Der p 5 and Blo t 5 from HDMs; Per a 10 from P. americana; Asp f 1, Asp f 2, Asp f 3, Asp f 4 and Asp f 6 from A. fumigatus; Mala s 8 and Mala s 13 from M. sympodialis; Alt a 1 from A. alternata; Pen c 13 from P. chrysogenum; Fel d 1 from cats; Can f 1, Can f 2, Can f 3, Can f 4 and Can f 5 from dogs; Mus m 1 from mice and Bos d 2 from cows. Defining the allergenic activity of other indoor IgE antibody binding molecules is necessary for a precision-medicine-oriented management of allergic diseases.

Ascaris lumbricoides Cystatin Prevents Development of Allergic Airway Inflammation in a Mouse Model

Severe helminth infections are negatively associated to allergic diseases like asthma; therefore, the immunomodulatory properties of parasite-derived components have been analyzed, raising the possibility of their use as anti-inflammatory molecules. We evaluated the immunomodulatory properties of Ascaris lumbricoides recombinant cysteine protease inhibitor (rAl-CPI) in a mouse model of allergic airway inflammation induced by the house dust mite (HDM) Blomia tropicalis and its effects on human monocyte-derived dendritic cells (HmoDCs). The B. tropicalis sensitized/challenged mice developed extensive cellular airway inflammatory response, which was significantly reduced upon treatment with rAl-CPI prior to B. tropicalis sensitization, affecting particularly the perivascular/peribronchial infiltrate cells, eosinophils/neutrophils, and goblet cells. A significant decrease of Th2 cytokines, total, and specific IgE antibodies was observed in rAl-CPI treated mice. The antibody response was biased to IgG, mainly IgG2a. Administration of rAl-CPI-alone and rAl-CPI before mite sensitization were associated with a significant increase of regulatory T cells (Tregs) in spleen and elevated IL-10 levels in BAL and splenocytes culture supernatants, which was partially affected by anti-IL10 receptor use. In vitro, rAl-CPI showed a modulatory effect on HmoDCs, lowering the expression of HLA-DR, CD83, and CD86, while inducing IL-10 and IL-6 production. This suggests an inhibition of HmoDC maturation and a possible link with the inhibition of the allergic response observed in the murine model.

Proteomic Analysis Reveals Allergen Variability among Breeds of the Dust Mite Blomia tropicalis

BACKGROUND

The dawn of the "omics" technologies has changed allergy research, increasing the knowledge and identification of new allergens. However, these studies have been almost restricted to Dermatophagoides spp. Although Blomia tropicalis has long been established as a clinically important source of allergens, a thorough proteomic characterization is still lacking for this dust mite.

OBJECTIVE

To increase knowledge of B. tropicalis allergens through proteomic analysis.

METHODS

Eleven in-bred lineages of B. tropicalis were obtained from 11 unique different pregnant females. Their somatic extracts were analyzed and compared with a commercially available extract by liquid chromatography tandem mass spectrometry (LC-MS/MS).

RESULTS

Considerable differences in the protein expression profiles were found among the breeds, and most of them displayed higher expression levels of major allergens than the commercially available extract. Blo t 2 was the most prominent allergenic protein in the analyzed extracts. Six identified allergens and 14 isoforms have not yet been recognized by IUIS. Conversely, 3 previously recognized B. tropicalis allergens were not found.

CONCLUSIONS

The clear impact of inbreeding on allergen content shown by our study leads us to conclude that the quantification and/or identification of allergens from in-bred lines should be routinely considered for mite cultivation in order to select breeds with higher amounts of major allergens. In this sense, LC-MS/MS may be a useful method to achieve this quality control for research and commercial purposes.

Hygienic conditions influence sensitization to Blomia tropicalis allergenic components: Results from the FRAAT birth cohort

BACKGROUND

In tropical zones, perennial exposure to house dust mite (HDM) allergens and helminth infections is present. Studying the impact of these conditions on the inception and evolution of allergic diseases is necessary to have an accurate view of their natural history. We aimed to evaluate the dynamics of genuine sensitization to Blomia tropicalis and Ascaris in children from the FRAAT birth cohort and the effects of helminth infection, environmental HDM allergen levels, and sociodemographic factors.

METHODS

Children were followed up to 6 years old. Specific IgE to recombinant allergens from B. tropicalis (Blo t 5 and Blo t 12) and Ascaris spp (Asc l 3, Asc l 13 and Asc s 1) was measured by ELISA at different time points. Allergen levels were measured in dust when children were 6 months old.

RESULTS

IgE sensitization increased over time up to 3 years old. Correlation among the specific IgE levels to B. tropicalis and Ascaris components is poor at year 1, but coefficients are high and significant (Spearman's rho coefficients >0.70) at year 6. Unhygienic conditions increased the odds of sensitization to B. tropicalis allergenic components. Blo t 5 levels were lower in the poorest. IgE response to Blo t 5 and Blo t 12 was less intense in children with high exposure to Blo t 5 (levels >80th percentile).

CONCLUSION

In this tropical community, the pattern of childhood IgE sensitization is different from that in developing countries and is influenced by the hygienic conditions.

House Dust Mite Allergy Under Changing Environments

Environmental variations induced by industrialization and climate change partially explain the increase in prevalence and severity of allergic disease. One possible mechanism is the increase in allergen production leading to more exposure and sensitization in susceptible individuals. House dust mites (HDMs) are important sources of allergens inducing asthma and rhinitis, and experimentally they have been demonstrated to be very sensitive to microenvironment modifications; therefore, global or regional changes in temperature, humidity, air pollution or other environmental conditions could modify natural HDM growth, survival and allergen production. There is evidence that sensitization to HDMs has increased in some regions of the world, especially in the subtropical and tropical areas; however, the relationship of this increase with environmental changes is not so clear as has reported for pollen allergens. In this review, we address this point and explore the effects of current and predicted environmental changes on HDM growth, survival and allergen production, which could lead to immunoglobulin E (IgE) sensitization and allergic disease prevalence. We also assess the role of adjuvants of IgE responses, such as air pollution and helminth infections, and discuss the genetic and epigenetic aspects that could influence the adaptive process of humans to drastic and relatively recent environmental changes we are experiencing.

Ascariasis as a model to study the helminth/allergy relationships

Ascariasis is the most frequent soil transmitted helminthiasis and, as well as other helminth infections, is expected to influence the clinical presentation of allergic diseases such as asthma. Indeed, several clinical and experimental works have shown an important impact either increasing or suppressing symptoms, and the same effects have been detected on the underlying immune responses. In this review we analyze the work on this field performed in Colombia, a Latin American tropical country, including aspects such as the molecular genetics of the IgE response to Ascaris; the allergenic activity of Ascaris IgE-binding molecular components and the immunological and clinical influences of ascariasis on asthma. The analysis allows us to conclude that the impact of ascariasis on the inception and evolution of allergic diseases such as asthma deserves more investigation, but advances have been made during the last years. The concurrent parasite-induced immunostimulatory and immunosuppressive effects during this helminthiasis do modify the natural history of asthma and some aspects of the practice of allergology in the tropics. Theoretically it can also influence the epidemiological trends of allergic diseases either by its absence or presence in different regions and countries.

Parasites and allergy: Observations from Africa

Population studies from the African continent have observed a marked increase in the prevalence of allergy‐related diseases over the past few decades, but the cause of this rise is not fully understood. The most investigated potential risk factor has been the relationship between exposure to helminths and allergy‐related outcomes. Immunologically, parallels exist between responses to helminths and to allergens as both are associated with elevated levels of immunoglobulin E, increased numbers of T helper 2 cells and other immune cells. However, epidemiological studies from the African continent have found inconsistent results. In this review, observations from population studies carried out in Africa over the last decade that focus on the relationship between helminth infections and allergy‐related outcomes are examined. How these findings advance our understanding of the complex interactions between helminths and allergies at the population level is also explored as well as some of the underlying immune mechanisms involved. This knowledge is important for better diagnosis, treatment and prevention of allergy‐related diseases and has wider global significance.

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.

Worms: Pernicious parasites or allies against allergies?

Type 2 immune responses are most commonly associated with allergy and helminth parasite infections. Since the discovery of Th1 and Th2 immune responses more than 30 years ago, models of both allergic disease and helminth infections have been useful in characterizing the development, effector mechanisms and pathological consequences of type 2 immune responses. The observation that some helminth infections negatively correlate with allergic and inflammatory disease led to a large field of research into parasite immunomodulation. However, it is worth noting that helminth parasites are not always benign infections, and that helminth immunomodulation can have stimulatory as well as suppressive effects on allergic responses. In this review, we will discuss how parasitic infections change host responses, the consequences for bystander immunity and how this interaction influences clinical symptoms of allergy.

Parasite allergens

Human IgE against helminths is a normal component of the whole protective response elicitesd during infection, when specific IgE to a great number of antigens is produced; however, few of those IgE binding components are actually allergens. In general, considering the strong Th2/IgE responses during helminth infections is intriguing that they are not usually associated with allergic symptoms, which probably (but not exclusively) depends on parasite-induced immunomodulation. However, allergic manifestations have been described during some helminth infections such as ascariasis, strongyloidiasis, anisakiasis and hydatidosis. In addition, there is evidence that helminthiases (e.g. ascariasis) can increase symptoms in allergic patients. Furthermore, allergic reactions during anti-helminth vaccination have been observed, a problem that also could be associated to the future use of parasite derived immunomodulators. Therefore, identification and characterization of helminth allergens is a matter of increasing research and a great number of IgE binding antigens have been found (www.allergen.org and www.allergome.org). Here we describe only a small group of them, for which allergenic activity (the ability to induce IgE mediated inflammation) have been clinical or experimentally demonstrated. Ascaris lumbricoides tropomyosin (Asc l 3) has strong allergenic activity; in the Tropics it has been associated with asthma and asthma severity, suggesting clinical relevance. In addition, due to its cross reactivity with mite tropomyosins this allergen could influence house dust mite (HDM) allergy diagnosis. Characterized Ascaris allergens also include the polyprotein As s 1 (ABA-1) and the Glutathione transferase As l 13. Other helminth allergens include Anisakis simplex Ani s 1, Ani s 4, Ani s 7 and Ani s 9; Necator americanus NaASP2q and Nacal1 and Schistosoma mansoni SmVAL4 and Sm22.6. Future work on helminth IgE binding antigens will help to understand several aspects of allergenicity and allergenic activity, among them the increasing finding of IgE binding molecules that not induce allergic symptoms.

Role in Allergic Diseases of Immunological Cross-Reactivity between Allergens and Homologues of Parasite Proteins

Implied under the rubric of the hygiene hypothesis is that helminth infection can protect against allergic disease. It is well known that helminths induce processes associated with type 2 immune responses, but they also induce important regulatory responses that can modulate these type 2-associated responses-modulation that influences responses to bystander antigens including allergens. Indeed, most epidemiological studies demonstrate a beneficial effect of helminth infection on atopy, but there are also convincing data to demonstrate that helminth infection can precipitate or worsen allergic inflammation/disease. Reasons for these disparate findings are much debated, but there is a school of thought that suggests that helminth-triggered type 2-associated responses, including IgE to cross-reactive aeroallergens, can offset the regulatory effects imposed by the same organisms. The cross-reactivity among helminths and allergenic tropomyosins dominated the antigen/allergen cross-reactivity field, but recent data suggest that cross-reactivity is much more common than previously appreciated. It has been demonstrated that a high degree of molecular similarity exists between allergens and helminth proteins. Thus, an understanding of the mechanisms underlying the response induced by helminth infection and their impact on the induction of allergic disease in the host are critical for designing therapies using iatrogenic infections or parasite products to treat inflammatory diseases and for developing vaccines against helminth parasites.

Risk factors for Toxocara spp. seroprevalence and its association with atopy and asthma phenotypes in school-age children in a small town and semi-rural areas of Northeast Brazil

Toxocara canis, Toxocara cati, are roundworms that live in the intestines of dogs and cats, respectively, and are predominantly agents of human toxocariasis. Studies have suggested that Toxocara spp. seroprevalence increases levels of total and aeroallergen-specific IgE (sIgE), asthma prevalence and asthma morbidity. Nevertheless, other work reported a negative association between Toxocara spp. seropositivity with skin hypersensititity and a positive association with sIgE. The objective of the present study was to evaluate risk factors for acquiring Toxocara spp. infection and to investigate possible significant association between its seroprevalence with atopy and asthma. Students from elementary schools, residents in a small town and its surroundings of Northeast Brazil, underwent blood sampling to measure levels of anti-Toxocara spp. IgG, peripheral blood eosinophils, and specific IgE to aeroallergens. We used univariable and multivariable logistic regression analyses to assess possible risk factors for Toxocara spp. seropositivity and its association with atopy, wheeze/asthma with asthma phenotypes, in a sample of 791 elementary school children aged 6-13 years. Toxocara spp. seroprevalence reached 63.6%; 49.9% had sIgE; 7.2% and 3.3% had atopic wheeze/asthma and non-atopic wheeze/asthma respectively. Risk factors associated with Toxocara spp. seropositivity were: contact with dogs (adj. OR 2.33; 95% CI=1.70-3.19) and cats (adj. OR 3.09; 95% CI=2.10-4.55), and male sex (adj. OR 2.21; 95% CI=1.62-3.02). The presence of anti-Toxocara IgG was statistically associated with blood eosinophils >4% and >10% (adj. OR 1.84; 95% CI=1.33-2.55 and adj. OR 2.07; 95% CI=1.45-2.97, respectively), and atopy (adj. OR 2.00; 95% CI=1.49-2.68), but it was not associated with wheeze/asthma. Concluding, the results obtained in this study showing the association of Toxocara spp. seroprevalence with sIgE may suggest a possible immunological cross-reactivity between IgE epitopes from Toxocara spp. and aeroallergens.

Influence of Parasitic Worm Infections on Allergy Diagnosis in Sub-Saharan Africa

Epidemiological studies from Sub-Saharan Africa indicate that allergies are on the rise in this region especially in urban compared to rural areas. This increase has been linked to improved hygiene, lifestyle changes, and lower exposure to pathogens in childhood. Reduced exposure to parasitic worm (helminth) infections and allergy outcomes has been the focus of a number of population studies over the years. Paradoxically, there are parallels in the immune responses to helminths and to allergies. Both conditions are associated with elevated levels of immunoglobulin E, high numbers of T helper 2 cells, eosinophils, and mast cells. These immune parallels have meant that the diagnosis of allergies in parts of the world where helminths are endemic can be hampered. The aim of this review is to examine observations from population studies conducted in Sub-Saharan Africa that demonstrate how helminth infections influence the parameters used to diagnose allergy outcomes in this region. We explore specifically how helminth infections hinder the in vitro diagnosis of allergic sensitization, influence the clinical manifestations of allergy, and also the effect of anthelmintic treatment on allergy outcomes. Advancing our understanding of how helminths influence allergy diagnosis is imperative for the development of improved tools to assess, diagnose, and treat allergic disorders in both helminth-endemic and non-endemic countries worldwide.

[Blomia tropicalis: A house dust mite in the tropics]

INTRODUCTION

Blomia tropicalis is a mite that belongs to the superfamily of Glycyphagidae. Initially described as a storage mite, it is now considered as a house dust mite of tropical and sub-tropical areas.

STATE OF THE ART

Sensitization to this mite is very common in South America and Southeast Asia. Epidemiological studies have also found sensitization to this mite in Africa and Central America. Blo t 5 is the major allergen of B. tropicalis. Co-sensitization to other house dust mites such as Dermatophagoides pteronyssinus (Der p) and Dermatophagoides farinae (Der f) is very common. Cross-reactivity has been described but recombinant allergens revealed by molecular biology techniques do not explain this cross-reactivity. Sensitization to B. tropicalis seems to begin at the age of 36 months, the incidence increases until adulthood, and decreases from the age of 50. The involvement of B. tropicalis in allergic rhinitis and asthma is well described. It is also implicated in other allergic diseases. Few studies have assessed the therapeutic strategies available against this mite but immunotherapy is widely used.

PERSPECTIVES

Studies are needed to better understand the role of B. tropicalis in human diseases and to develop specific treatments.

Allergens of Blomia tropicalis: An Overview of Recombinant Molecules

Allergic diseases are considered a major problem for healthcare systems in both developed and developing countries. House dust mites are well-known triggers of allergic manifestations. While the Dermatophagoides genus is widely distributed globally, Blomia tropicalis is the most prominent mite species in the tropical and subtropical regions of the world. Over the last decades, an increase in sensitization rates to B. tropicalis has been reported, leading to increased research efforts on Blomia allergens. In fact, 8 new allergens have been identified and characterized to different degrees. Here, we provide an overview of recent developments concerning the identification and production of recombinant Blomia allergens, as well as their structural and immunological characterization. Although considerable progress has been achieved, detailed molecule-based studies are still needed to better define the clinical relevance of Blomia allergens. Thus, the establishment of a well-standardized and fully characterized panel of allergens remains a challenge for the development of better diagnosis and therapy of allergic diseases induced by B. tropicalis.

Dissociation between skin test reactivity and anti-aeroallergen IgE: Determinants among urban Brazilian children

Background

The dissociation between specific IgE and skin prick test reactivity to aeroallergens, a common finding in populations living in low and middle-income countries, has important implications for the diagnosis and treatment of allergic diseases. Few studies have investigated the determinants of this dissociation. In the present study, we explored potential factors explaining this dissociation in children living in an urban area of Northeast Brazil, focusing in particular on factors associated with poor hygiene.

Methods

Of 1445 children from low income communities, investigated for risk factors of allergies, we studied 481 with specific IgE antibodies to any of Blomia tropicalis, Dermatophagoides pteronyssinus, Periplaneta americana and Blatella germanica allergens. Data on demographic, environmental and social exposures were collected by questionnaire; serum IgG and stool examinations were done to detect current or past infections with viral, bacterial, protozoan and intestinal helminth pathogens. We measured atopy by skin prick testing (SPT) and specific IgE (sIgE) to aerollergens in serum (by ImmunoCAP). SIgE reactivity to B. tropicalis extract depleted of carbohydrates was measured by an in-house ELISA. Total IgE was measured by in house capture ELISA. SNPs were typed using Illumina Omni 2.5.

Results

Negative skin prick tests in the presence of specific IgE antibodies were frequent. Factors independently associated with a reduced frequency of positive skin prick tests were large number of siblings, the presence of IgG to herpes simplex virus, Ascaris lumbricoides and Trichuris trichiura infections, living in neighborhoods with infrequent garbage collection, presence of rodents and cats in the household and sIgE reactivity to glycosylated B. tropicalis allergens. Also, SNP on IGHE (rs61737468) was negatively associated with SPT reactivity.

Conclusions

A variety of factors were found to be associated with decreased frequency of SPT such as unhygienic living conditions, infections, total IgE, IgE response to glycosylated allergens and genetic polymorphisms, indicating that multiple mechanisms may be involved. Our data, showing that exposures to an unhygienic environment and childhood infections modulate immediate allergen skin test reactivity, provide support for the “hygiene hypothesis”.

Genetic Variants in CHIA and CHI3L1 Are Associated with the IgE Response to the Ascaris Resistance Marker ABA-1 and the Birch Pollen Allergen Bet v 1

Helminth infections and allergic diseases are associated with IgE hyperresponsiveness but the genetics of this phenotype remain to be defined. Susceptibility to Ascaris lumbricoides infection and antibody levels to this helminth are associated with polymorphisms in locus 13q33-34. We aimed to explore this and other genomic regions to identify genetic variants associated with the IgE responsiveness in humans. Forty-eight subjects from Cartagena, Colombia, with extreme values of specific IgE to Ascaris and ABA-1, a resistance marker of this nematode, were selected for targeted resequencing. Burden analyses were done comparing extreme groups for IgE values. One-hundred one SNPs were genotyped in 1258 individuals of two well-characterized populations from Colombia and Sweden. Two low-frequency coding variants in the gene encoding the Acidic Mammalian Chitinase (CHIA rs79500525, rs139812869, tagged by rs10494133) were found enriched in high IgE responders to ABA-1 and confirmed by genetic association analyses. The SNP rs4950928 in the Chitinase 3 Like 1 gene (CHI3L1) was associated with high IgE to ABA-1 in Colombians and with high IgE to Bet v 1 in the Swedish population. CHIA rs10494133 and ABDH13 rs3783118 were associated with IgE responses to Ascaris. SNPs in the Tumor Necrosis Factor Superfamily Member 13b gene (TNFSF13B) encoding the cytokine B cell activating Factor were associated with high levels of total IgE in both populations. This is the first report on the association between low-frequency and common variants in the chitinases-related genes CHIA and CHI3L1 with the intensity of specific IgE to ABA-1 in a population naturally exposed to Ascaris and with Bet v 1 in a Swedish population. Our results add new information about the genetic influences of human IgE responsiveness; since the genes encode for enzymes involved in the immune response to parasitic infections, they could be helpful for understanding helminth immunity and allergic responses. We also confirmed that TNFSF13B has an important and conserved role in the regulation of total IgE levels, which supports potential evolutionary links between helminth immunity and allergic response.

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.

Helminths are positively associated with atopy and wheeze in Ugandan fishing communities: results from a cross-sectional survey

Background

Parasitic helminths are potent immunomodulators and chronic infections may protect against allergy‐related disease and atopy. We conducted a cross‐sectional survey to test the hypothesis that in heavily helminth‐exposed fishing villages on Lake Victoria, Uganda, helminth infections would be inversely associated with allergy‐related conditions.

Methods

A household survey was conducted as baseline to an anthelminthic intervention trial. Outcomes were reported wheeze in last year, atopy assessed both by skin prick test (SPT) and by the measurement of allergen‐specific IgE to dust mites and cockroach in plasma. Helminth infections were ascertained by stool, urine and haemoparasitology. Associations were examined using multivariable regression.

Results

Two thousand three hundred and sixteen individuals were surveyed. Prevalence of reported wheeze was 2% in under‐fives and 5% in participants ≥5 years; 19% had a positive SPT; median Dermatophagoides‐specific IgE and cockroach‐specific IgE were 1440 and 220 ng/ml, respectively. S. mansoni, N. americanus, S. stercoralis, T. trichiura, M. perstans and A. lumbricoides prevalence was estimated as 51%, 22%, 12%, 10%, 2% and 1%, respectively. S. mansoni was positively associated with Dermatophagoides‐specific IgE [adjusted geometric mean ratio (aGMR) (95% confidence interval) 1.64 (1.23, 2.18)]; T. trichiura with SPT [adjusted odds ratio (aOR) 2.08 (1.38, 3.15)]; M. perstans with cockroach‐specific IgE [aGMR 2.37 (1.39, 4.06)], A. lumbricoides with wheeze in participants ≥5 years [aOR 6.36 (1.10, 36.63)] and with Dermatophagoides‐specific IgE [aGMR 2.34 (1.11, 4.95)]. No inverse associations were observed.

Conclusions

Contrary to our hypothesis, we found little evidence of an inverse relationship between helminths and allergy‐related outcomes, but strong evidence that individuals with certain helminths were more prone to atopy in this setting.

The Anisakis Transcriptome Provides a Resource for Fundamental and Applied Studies on Allergy-Causing Parasites

Background

Food-borne nematodes of the genus Anisakis are responsible for a wide range of illnesses (= anisakiasis), from self-limiting gastrointestinal forms to severe systemic allergic reactions, which are often misdiagnosed and under-reported. In order to enhance and refine current diagnostic tools for anisakiasis, knowledge of the whole spectrum of parasite molecules transcribed and expressed by this parasite, including those acting as potential allergens, is necessary.

Methodology/Principal Findings

In this study, we employ high-throughput (Illumina) sequencing and bioinformatics to characterise the transcriptomes of two Anisakis species, A. simplex and A. pegreffii, and utilize this resource to compile lists of potential allergens from these parasites. A total of ~65,000,000 reads were generated from cDNA libraries for each species, and assembled into ~34,000 transcripts (= Unigenes); ~18,000 peptides were predicted from each cDNA library and classified based on homology searches, protein motifs and gene ontology and biological pathway mapping. Using comparative analyses with sequence data available in public databases, 36 (A. simplex) and 29 (A. pegreffii) putative allergens were identified, including sequences encoding ‘novel’ Anisakis allergenic proteins (i.e. cyclophilins and ABA-1 domain containing proteins).

Conclusions/Significance

This study represents a first step towards providing the research community with a curated dataset to use as a molecular resource for future investigations of the biology of Anisakis, including molecules putatively acting as allergens, using functional genomics, proteomics and immunological tools. Ultimately, an improved knowledge of the biological functions of these molecules in the parasite, as well as of their immunogenic properties, will assist the development of comprehensive, reliable and robust diagnostic tools.

Nematodes within the genus Anisakis (i.e. A. simplex and A. pegreffii, also known as herring worms) are the causative agents of the fish-borne gastrointestinal illness known as ‘anisakiasis’, with infections resulting in symptoms ranging from mild gastric forms to severe allergic reactions leading to urticaria, gastrointestinal and/or respiratory signs and/or anaphylaxis (‘allergic anisakiasis’). Despite significant advances in knowledge of the pathobiology of allergic anisakiasis, thus far, the exact number and nature of parasite molecules acting as potential allergens are currently unknown; filling this gap is necessary to the development of robust and reliable diagnostics for allergic anisakiasis which, in turn, underpins the implementation of effective therapeutic strategies. Here, we use RNA-Seq and bioinformatics to sequence and annotate the transcriptomes of A. simplex and A. pegreffii, and, as an example application of these resources, mine this data to identify and characterise putative novel parasite allergens based on comparisons with known allergen sequence data from other parasites and other organisms.

Particularities of allergy in the Tropics

Allergic diseases are distributed worldwide and their risk factors and triggers vary according to geographical and socioeconomic conditions. Allergies are frequent in the Tropics but aspects of their prevalence, natural history, risk factors, sensitizers and triggers are not well defined and some are expected to be different from those in temperate zone countries. The aim of this review is to investigate if allergic diseases in the Tropics have particularities that deserve special attention for research and clinical practice. Such information will help to form a better understanding of the pathogenesis, diagnosis and management of allergic diseases in the Tropics. As expected, we found particularities in the Tropics that merit further study because they strongly affect the natural history of common allergic diseases; most of them related to climate conditions that favor permanent exposure to mite allergens, helminth infections and stinging insects. In addition, we detected several unmet needs in important areas which should be investigated and solved by collaborative efforts led by the emergent research groups on allergy from tropical countries.

EAACI Molecular Allergology User's Guide

The availability of allergen molecules ('components') from several protein families has advanced our understanding of immunoglobulin E (IgE)-mediated responses and enabled 'component-resolved diagnosis' (CRD). The European Academy of Allergy and Clinical Immunology (EAACI) Molecular Allergology User's Guide (MAUG) provides comprehensive information on important allergens and describes the diagnostic options using CRD. Part A of the EAACI MAUG introduces allergen molecules, families, composition of extracts, databases, and diagnostic IgE, skin, and basophil tests. Singleplex and multiplex IgE assays with components improve both sensitivity for low-abundance allergens and analytical specificity; IgE to individual allergens can yield information on clinical risks and distinguish cross-reactivity from true primary sensitization. Part B discusses the clinical and molecular aspects of IgE-mediated allergies to foods (including nuts, seeds, legumes, fruits, vegetables, cereal grains, milk, egg, meat, fish, and shellfish), inhalants (pollen, mold spores, mites, and animal dander), and Hymenoptera venom. Diagnostic algorithms and short case histories provide useful information for the clinical workup of allergic individuals targeted for CRD. Part C covers protein families containing ubiquitous, highly cross-reactive panallergens from plant (lipid transfer proteins, polcalcins, PR-10, profilins) and animal sources (lipocalins, parvalbumins, serum albumins, tropomyosins) and explains their diagnostic and clinical utility. Part D lists 100 important allergen molecules. In conclusion, IgE-mediated reactions and allergic diseases, including allergic rhinoconjunctivitis, asthma, food reactions, and insect sting reactions, are discussed from a novel molecular perspective. The EAACI MAUG documents the rapid progression of molecular allergology from basic research to its integration into clinical practice, a quantum leap in the management of allergic patients.

IgE responses to Ascaris and mite tropomyosins are risk factors for asthma

BACKGROUND

The relationship between helminthiases and allergy is a matter of considerable interest and research. In the tropics, house dust mite exposure, a known risk factor for asthma, is frequently concurrent with helminth infections. It remains to be defined whether infection with the common roundworm Ascaris or its bystander immunological effects influence the prevalence and pathogenesis of asthma independently of mite sensitization.

OBJECTIVE

To investigate the relationship between the IgE responses to Ascaris and its purified allergens and the risk of asthma in a tropical country.

METHODS

A nested case-control study was performed in 356 subjects who reported current and past asthma symptoms (asthmatics) and 435 controls that had never experienced such symptoms. They were tested for serum levels of total IgE and specific IgE to Ascaris extract, Asc s 1 (ABA-1), Asc l 3 (tropomyosin) and GST (glutathione transferase). In addition, specific IgE to Dermatophagoides pteronyssinus, Blomia tropicalis and their tropomyosins Der p 10 and Blo t 10 was measured. Sensitization was defined as a positive specific IgE result to any extract or recombinant allergen.

RESULTS

Sensitization to Ascaris and D. pteronyssinus was independently associated with asthma after adjustment for age, gender, socio-economic stratum, city and other IgE levels (adjusted ORs: 2.17; 95% CI 1.37-3.42 and 2.46; 95% CI 1.54-3.92), respectively. There was also a significant association with sensitization to the highly allergenic and cross-reactive tropomyosins Asc l 3, Blo t 10 and Der p10 (aORs: 1.76; 95% CI 1.21-2.57, 1.64; 95% CI 1.14-2.35 and 1.51; 95% CI 1.02-2.24), respectively.

CONCLUSION AND CLINICAL RELEVANCE

IgE responses to Ascaris are associated with asthma symptoms in a population living in the tropics. Sensitization to the cross-reactive Ascaris and mite tropomyosins partially underlies this finding. These results have potential relevance in asthma diagnosis and management.

Presensitization to Ascaris antigens promotes induction of mite-specific IgE upon mite antigen inhalation in mice

BACKGROUND

Patients with house dust mite (HDM) allergy or Ascariasis produce serum IgE specific to the antigens of HDM or nematode Ascaris, respectively. Although human IgE cross-reactivity has been reported between HDM and Ascaris antigens, it remains unclear whether it contributes to the pathogenesis of allergic diseases. We herein investigated the induction of cross-reactive antibodies and T cells in mice and effects of airway exposure to HDM antigens after preimmunization with Ascaris antigens.

METHODS

Mice were intraperitoneally immunized with HDM or Ascaris antigens with Alum, followed by the intranasal administration of HDM antigens. Serum antigen-specific IgE and IgG were measured by ELISA. Cytokine release in splenocytes from Ascaris-immunized mice upon in vitro restimulation with HDM antigens were measured by ELISA.

RESULTS

Immunization with Ascaris or HDM antigens induced cross-reactive IgG1. Splenocytes from Ascaris-immunized mice released IL-5 and IL-13 in response to the restimulation with HDM antigens. Subsequent airway exposure to HDM antigens promoted the induction of HDM-specific IgE and upregulation of HDM-specific IgG1 in Ascaris-immunized mice, whereas these responses were not detected or smaller without the Ascaris presensitization.

CONCLUSIONS

We demonstrated that the immunization of naïve mice with Ascaris antigens induced production of antibodies and differentiation of Th2 cells, which were cross-reactive to HDM antigens, and accelerated induction of serum HDM-specific IgE upon subsequent airway exposure to HDM antigens in mice. These results suggest that sensitization to HDM towards IgE-mediated allergic diseases is faster in individuals with a previous history of Ascaris infection than in those without presensitization to Ascaris.

Antigenicity, Immunogenicity, Allergenicity

The term “immune” pertains to the body keeping itself free from diseases, not to trigger any diseases. In this regard, it makes sense for us to divide antigenicity into immunogenicity and allergenicity. This distinction allows for the characterization of all types of modern antigens, i.e., to evaluate and modify a priori the allergenicity of an antigen before it is applied to humans. In this chapter, we also formulated the hypothesis that “Balanced Stimulation by Whole Antigens” is essential for immune development. This hypothesis revives the practicality of the “Hygiene Hypothesis” and can provide a fundamental solution to curb the increasing prevalence of allergic disease, namely, early exposure, at 0–1 year old or earlier, in utero, of representative allergens/protein antigens with immunogenicity retained or improved and allergenicity attenuated or eliminated.

Effect of urban vs. rural residence on the association between atopy and wheeze in Latin America: findings from a case-control analysis

Background

The association between atopy and asthma is attenuated in non-affluent populations, an effect that may be explained by childhood infections such as geohelminths.

Objective

To investigate the association between atopy and wheeze in schoolchildren living in urban and rural areas of Ecuador and examine the effects of geohelminths on this association.

Methods

We performed nested case–control studies among comparable populations of schoolchildren living in rural communities and urban neighbourhoods in the Province of Esmeraldas, Ecuador. We detected geohelminths in stool samples, measured recent wheeze and environmental exposures by parental questionnaire, and atopy by specific IgE (sIgE) and skin prick test (SPT) reactivity to aeroallergens.

Results

Atopy, particularly sIgE to house dust mite (HDM), was more strongly associated with recent wheeze in urban than rural schoolchildren: (urban, adj. OR 5.19, 95% CI 3.37–8.00, P < 0.0001; rural, adj. OR 1.81, 95%CI 1.09–2.99, P = 0.02; interaction, P < 0.001). The population fractions of wheeze attributable to atopy were approximately two-fold greater in urban schoolchildren: SPT to any allergen (urban 23.5% vs. rural 10.1%), SPT to HDM (urban 18.5% vs. rural 9.6%), and anti-HDM IgE (urban 26.5% vs. rural 10.5%), while anti-Ascaris IgE was related to wheeze in a high proportion of rural (49.7%) and urban (35.4%) children. The association between atopy and recent wheeze was attenuated by markers of geohelminth infections.

Conclusions

Our data suggest that urban residence modifies the association between HDM atopy and recent wheeze, and this effect is explained partly by geohelminth infections.

Analysis of glutathione S-transferase allergen cross-reactivity in a North American population: Relevance for molecular diagnosis

BACKGROUND

It is not clear whether cross-reactivity or cosensitization to glutathione S-transferases (GSTs) occurs in tropical and subtropical environments. In the United States, Bla g 5 is the most important GST allergen and lack of coexposure to GSTs from certain species allows a better assessment of cross-reactivity.

OBJECTIVES

To examine the molecular structure of GST allergens from cockroach (Bla g 5), dust mites (Der p 8 and Blo t 8), and helminth (Asc s 13) for potential cross-reactive sites, and to assess the IgE cross-reactivity of sensitized patients from a temperate climate for these allergens for molecular diagnostic purposes.

METHODS

Four crystal structures were determined. Sera from patients allergic to cockroach and mite were tested for IgE reactivity to these GSTs. A panel of 6 murine anti-Bla g 5 mAb was assessed for cross-reactivity with the other 3 GSTs using antibody binding assays.

RESULTS

Comparisons of the allergen structures, formed by 2-domain monomers that dimerize, revealed few contiguous regions of similar exposed residues, rendering cross-reactivity unlikely. Accordingly, anti-Bla g 5 or anti-Der p 8 IgE from North American patients did not recognize Der p 8 or Bla g 5, respectively, and neither showed binding to Blo t 8 or Asc s 13. A weaker binding of anti-Bla g 5 IgE to Der p 8 versus Bla g 5 (∼ 100-fold) was observed by inhibition assays, similar to a weak recognition of Der p 8 by anti-Bla g 5 mAb. Patients from tropical Colombia had IgE to all 4 GSTs.

CONCLUSIONS

The lack of significant IgE cross-reactivity among the 4 GSTs is in agreement with the low shared amino acid identity at the molecular surface. Each GST is needed for accurate molecular diagnosis in different geographic areas.

The IgE response to Ascaris molecular components is associated with clinical indicators of asthma severity

Background

Asthma is a common chronic disease worldwide and Ascaris lumbricoides infection (ascariasis) is frequent in tropical regions. However, the effect of ascariasis on asthma severity has not been sufficiently explored. We sought to evaluate the influence of the IgE immune response to Ascaris extract and purified house dust mites (HDM) and Ascaris allergens on indicators of asthma severity in patients living in the tropics.

Methods

Asthmatic patients from Cartagena, Colombia were recruited. Clinical assessment included questionnaires, physical examination, allergy skin tests, spirometry, parasite stool examination and IgE antibody measurements. Asthma was diagnosed by a physician according to validated criteria. Indicators of severity were occurrence of severe dyspnea episodes, night awakenings events, > 4 emergency room (ER) visits and hospitalizations during the last year. Specific IgE to Der p 2, Ascaris spp., Blomia tropicalis and Dermatophagoides pteronyssinus extracts was determined by ImmunoCap. IgE to tropomyosins (Asc l 3, Blo t 10 and Der p 10), Blo t 5 and Asc s 1 was detected by ELISA. Logistic regression analyses were used to explore the relationships between sensitization and indicators of asthma severity.

Results

After adjustment for HDM sensitization, Ascaris sensitization remained associated with severe dyspnea (aOR: 1.90, 95% CI: 1.08 - 3.34, p = 0.03) and > 4 ER visits (aOR: 2.23, 95% CI: 1.15 - 4.30, p = 0.02). We also found that sensitization to the species specific markers Blo t 5 and Asc s 1, as well as the cross-reactive tropomyosins of D. pteronyssinus and Ascaris were associated with > 4 ER visits. Der p 2 sensitization was associated with bronchodilator responsiveness (aOR: 2.24: 1.25-4.02, p = 0.01). Remarkably, significantly higher IgE levels to HDM species specific allergens were found in Ascaris sensitized patients.

Conclusions

In this tropical population, IgE sensitization to Ascaris and the cross-reactive tropomyosins was frequent and associated with clinical indicators of asthma severity. The significant relationship between sensitization to the nematode-specific marker Asc s 1 and ER attendance supports these findings. Moreover, ascariasis increases the human IgE responses to HDM specific allergens.