Gene-environment interaction effects on the development of immune responses in the 1st year of life

Epidemiological and immunological evidence for the hygiene hypothesis

Allergic diseases are inflammatory disorders that develop on the basis of complex gene-environment interactions. The prevalence of allergies is steadily increasing and seems to be associated with modern lifestyle. Therefore, it was hypothesized that high living standards and hygienic conditions are correlated with an increased risk for the development of an allergic disease. This so-called "hygiene hypothesis" states that due to reduced exposure to microbial components, the proposed allergy-preventing potential of these factors is no more present in sufficient qualities and/or quantities, which leads to an imbalance of the immune system with a predisposition to the development of allergic disorders. Meanwhile, several epidemiological studies were conducted supporting this concept and generating novel ideas for the underlying mechanisms that were then followed up by use of well-defined animal models and human studies. The current view of cellular and molecular mechanisms responsible for these phenomena includes changes in the fine balancing of T helper cell 1 (Th1), Th2 and regulatory T cell (Treg) responses which are triggered by altered or missing innate immune cell activation. In fact, proper activation of cells of the innate immune system via their so-called pattern recognition receptors has been demonstrated to play a crucial role in early shaping of the immune system and suppression of the development of Th2-driven allergic immune responses. These processes start already in utero and prenatal as well as early postnatal developmental stages seem to represent a certain "window of opportunity" for allergy-preventing environmental influences.

A generic research paradigm for identification and validation of early molecular diagnostics and new therapeutics in common disorders

Genetically complex disorders continue to confound investigators because of their many underlying factors, both genetic and environmental. In order to tease apart the heritable from the non-heritable contributions to disease, clinicians are relying on researchers in the rapidly expanding fields of high-throughput genomics to identify surrogate clinical endpoints, called biomarkers, that provide a measure of the probability that an individual will succumb to the disease in question. The goals of current biomedical research into complex disorders are to identify and utilize these biomarkers, not only for early detection, but also for personalized treatment with knowledge-guided therapeutics. As the identification of these biomarkers is basically a problem of discovery, we discuss new insights into biomarker detection utilizing the most current genomic technologies available. Additionally, we present here a generic paradigm for the validation of such molecular diagnostics as well as new treatment modalities for complex and increasingly common diseases. Lastly, we delve into the ways genomic biomarkers might be implemented in a clinical setting to allow the subsequent application of targeted therapeutics, which can help the ever expanding groups of individuals experiencing these insidious diseases.

Gene-environmental interaction in asthma

PURPOSE OF REVIEW

Asthma is likely to result from the effects of environmental stimuli in genetically susceptible individuals. This review summarizes recent studies of gene-environmental interaction in the pathogenesis of asthma, focusing on study designs.

RECENT FINDINGS

Studies using genetic epidemiology, in-vitro and ex-vivo models and in-vivo model organisms demonstrate that gene-environmental interaction in involved in the development of asthma. Genetic association studies show a reduced risk of asthma and atopy with early life exposure to farming environments and house dust endotoxin, and increased risk with environmental tobacco smoke. These associations are modified by CD14 genotype. In people with a specific genotype, high environmental exposure may have the opposite effect of low exposure, possibly explaining some of the inconsistencies in previous studies. In-vitro and ex-vivo cell culture experiments show gene-environmental interactions with Toll-like receptor agonists, viruses and tobacco smoke. Interactions between innate immunity genes and exposure to endotoxin and air pollution have been observed in in-vivo mouse models.

SUMMARY

The expanding evidence for gene-environmental interaction in asthma indicates the importance of measuring environmental factors in genetic studies of asthma. Understanding gene-environmental interaction would facilitate risk prognostication, improve preventive strategies and develop targeted interventions in people with asthma.

Gene-environment interactions in asthma: with apologies to William of Ockham

Many environmental factors and a large number of genetic polymorphisms have been reported to be associated with asthma risk in different locales and at different ages. It seems that what we call asthma is a heterogeneous set of conditions for which the only common feature is recurrent airway obstruction that is at least partially responsive to usual asthma therapy. Recent studies in which environmental factors and genetic variants were studied concomitantly have suggested a potential unifying concept for the disease. It seems that asthma is a genetically mediated development dysregulation of diverse immune and airway responses to a variety of specific and nonspecific exposures. It thus seems improbable that most genetic variants associated with asthma influence the disease regardless of which environmental factors trigger it and at which lifetime phase they are present. More likely, the most important gene variants for asthma are polymorphisms that exert their influence on the network system controlling biological responses to asthma-related exposures.

Asthma phenotypes

PURPOSE OF REVIEW

Asthma is a heterogeneous disorder presenting with many phenotypes. Precise phenotypic definition has eluded the medical research community for years, despite recognition of different disease subtypes. Improved phenotypic characterization and knowledge of underlying pathobiology is necessary for linkage of specific genotypes with clinical disease manifestations.

RECENT FINDINGS

Phenotyping has been difficult because asthma is likely to be comprised of overlapping syndromes with varying origins and heterogeneous pathobiology. Currently, the field is too reliant on classification by trigger or symptoms. Since genotypic and phenotypic heterogeneity are inherent in asthma, patients presenting with different asthma phenotypes may need tailored therapies. Studies have begun to link genetics with disease mechanism and therapeutic response. As disease etiology, onset, progression and severity vary greatly among patients, however, the relative contribution of genetic factors may be difficult to ascertain. Definition of the full array of complex biological consequences of molecular target modulation is a prerequisite for therapies based on this concept.

SUMMARY

The advent of targeted therapies for asthma and clinical trials based on phenotype and genotype have raised interest in more accurate description of asthma phenotypes. Therapies based on phenotypic and genotypic characteristics may be useful in asthma management. A variety of factors, however, must be addressed before such approaches become standard.

VII International Symposium on Respiratory Viral Infections

The VII International Symposium on Respiratory Viral Infections was a multidisciplinary forum for the presentation of recent advances in respiratory virus research with special emphasis on antiviral therapies and vaccine strategies. Topics covered in invited lectures included detection of novel respiratory viral pathogens and viral evolution, characterization of the 1918 pandemic virus, human metapneumovirus infections, human respiratory epithelial cultures for studying viral pathogenesis, the role of respiratory viruses in the pathogenesis of asthma, influenza-bacterial interactions, advances in generating vaccine candidates against global respiratory threats like avian influenza and SARS, antiviral resistance surveillance in influenza viruses, and a mini-symposium on advances in viral diagnostics. Other talks covered the live, attenuated intranasal influenza vaccine, monoclonals for respiratory syncytial virus (RSV), mechanisms of antiviral resistance in influenza B, and novel inhibitors for influenza, RSV and rhinovirus infections.

Impact of genetic variants in IL-4, IL-4 RA and IL-13 on the anti-pneumococcal antibody response

BACKGROUND

Significant differences in immune responses upon vaccination have been described, suggesting genetics are important in determining the magnitude of vaccine responses. The interleukin (IL)-4 pathway, including IL-4, IL-13 and the IL-4 receptor alpha chain (IL-4 Ralpha), is central to humoral responses and therefore could have an impact on vaccine responsiveness.

OBJECTIVE

To investigate whether single nucleotide polymorphisms (SNPs) in the IL-4, IL-13 and IL-4 RA genes influence pneumococcal serotype-specific IgG antibody responses.

METHODS

SNPs in the IL-4 gene (C -589T, G2979T), the IL-13 gene (G -1112A, Arg130Gln) and in the IL-4 RA gene (Ile50Val, Gln551Arg) were investigated in isolation and in combination, for their influence on serotype-specific IgG antibody responses upon combined pneumococcal conjugate and polysaccharide vaccinations in children with a history of recurrent otitis media.

RESULTS

Lower antibody responses were observed for alleles previously associated with atopy, IL-4 -589T, IL-4 2979T and IL-4 Ralpha 551Gln. Effects were stronger in gene haplotype combinations or in multiple haplotype combination analyses.

CONCLUSION

This study highlights the importance of host genetic factors in vaccine responses. Furthermore, it supports the approach of studying the effect of combinations of multiple alleles, in haplotypes or in combinations of haplotypes, on complex phenotypes within a biological pathway.

Genotype x adiposity interaction linkage analyses reveal a locus on chromosome 1 for lipoprotein-associated phospholipase A2, a marker of inflammation and oxidative stress

Because obesity leads to a state of chronic, low-grade inflammation and oxidative stress, we hypothesized that the contribution of genes to variation in a biomarker of these two processes may be influenced by the degree of adiposity. We tested this hypothesis using samples from the San Antonio Family Heart Study that were assayed for activity of lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), a marker of inflammation and oxidative stress. Using an approach to model discrete genotypexenvironment (GxE) interaction, we assigned individuals to one of two discrete diagnostic states (or "adiposity environments"): nonobese or obese, according to criteria suggested by the World Health Organization. We found a genomewide maximum LOD of 3.39 at 153 cM on chromosome 1 for Lp-PLA(2). Significant GxE interaction for Lp-PLA(2) at the genomewide maximum (P=1.16 x 10(-4)) was also found. Microarray gene-expression data were analyzed within the 1-LOD interval of the linkage signal on chromosome 1. We found two transcripts--namely, for Fc gamma receptor IIA and heat-shock protein (70 kDa)--that were significantly associated with Lp-PLA(2) (P<.001 for both) and showed evidence of cis-regulation with nominal LOD scores of 2.75 and 13.82, respectively. It would seem that there is a significant genetic response to the adiposity environment in this marker of inflammation and oxidative stress. Additionally, we conclude that GxE interaction analyses can improve our ability to identify and localize quantitative-trait loci.

Interrelationships of quantitative asthma-related phenotypes in the Epidemiological Study on the Genetics and Environment of Asthma, Bronchial Hyperresponsiveness, and Atopy

BACKGROUND

Delineating asthma subphenotypes is of interest to understand the cause of the disease. Few studies have addressed the interrelationships of quantitative asthma-related traits.

OBJECTIVE

We sought to study the interrelationships of allergy markers and FEV(1) in relation to asthma and sex in children and adults.

METHODS

Total IgE levels, skin prick test (SPT) positivity, eosinophil counts, and FEV(1) were assessed in 299 asthmatic cases (children and adults) recruited in chest clinics and 309 nonasthmatic population-based control subjects in the French Epidemiological Study on the Genetics and Environment of Asthma, Bronchial Hyperresponsiveness, and Atopy.

RESULTS

Allergy parameters were significantly higher in asthmatic cases than in control subjects for children and adults and for both sexes. Sex and age modified the pattern of concordance of high IgE levels, SPT positivity, and eosinophilia among asthmatic cases, with the greatest overlap in male children (64%) and the lowest in male adults (18%). Patterns of change over the lifespan of IgE levels, eosinophil counts, and FEV(1)/height(2) varied, with the acceleration of FEV(1) decrease being particularly evident in asthmatic adults. In adult cases and control subjects, SPT positivity (particularly to indoor allergens) was significantly related to IgE levels but not to eosinophil counts. The association of eosinophil counts with IgE levels was evident only in children. Environmental factors (smoking, pets, and country living) did not alter the patterns observed.

CONCLUSIONS

Each allergy-related phenotype showed a distinct relation with asthma, with the role for eosinophils being different than that for IgE levels and SPT responses.

CLINICAL IMPLICATIONS

Taking age and sex into account is essential for understanding the interrelationships of the various allergy-related phenotypes to asthma status.

Sex-specific genetic architecture of asthma-associated quantitative trait loci in a founder population

Identifying genes that influence susceptibility to asthma-related and atopy-related phenotypes has been challenging, owing to clinical heterogeneity and a complex underlying genetic architecture that includes both gene-gene and gene-environment interactions. In this article, we report the results of genome-wide linkage and association studies of eight asthma-associated quantitative traits in the Hutterites, a founder population of European descent. Our study revealed significant sex-specific genetic architecture for at least five of these traits, and identified 13 genome-wide significant quantitative trait loci (QTL) by linkage or association that are present in only one of the sexes (nine in males, four in females).

Bronchiolitis to asthma: a review and call for studies of gene-virus interactions in asthma causation

Viral infections are important causes of asthma exacerbations in children, and lower respiratory tract infections (LRTIs), caused by viruses such as respiratory syncytial virus (RSV) and rhinovirus (RV), are a leading cause of bronchiolitis in infants. Infants hospitalized with bronchiolitis are at significantly increased risk for both recurrent wheezing and childhood asthma. To date, studies addressing the incidence of asthma after bronchiolitis severe enough to warrant hospitalization have focused almost exclusively on RSV, but a number of recent studies suggest that other respiratory pathogens, including RV, may contribute as well. It is not known whether viral bronchiolitis directly contributes to asthma causation or simply identifies infants at risk for subsequent wheezing, as from an atopic predisposition or preexisting abnormal lung function. Alternatively, the properties of the infecting virus may be important. Thus, many possible determinants exist that may contribute to the severity of bronchiolitis and the subsequent development of asthma. One such determinant is the potential involvement of genetic susceptibility loci to asthma after viral bronchiolitis, a critical area that is just beginning to be evaluated. By clarifying the roles of both host- (genetic) and virus- (environment) specific factors that contribute to the frequency and severity of viral LRTI, it may be possible to determine if severe LRTIs cause asthma, or if asthma susceptibility predisposes patients to severe LRTI in response to viral infection. Characterizing these relationships offers the potential of identifying at-risk hosts in whom preventing or delaying infection could alter the phenotypic expression of asthma.

Die Einbeziehung genetischer Faktoren in Studien der Epidemiologie

During the last two decades, genetic epidemiology has been established in parallel to the area of classical epidemiology. This paper presents some essentials of the epidemiology of genetic factors. It begins with a discussion of complex diseases that are characterized by an involvement of several genes. The problems that are attached to modeling gene-gene and gene-environment interactions and their integration into causal pathways are elucidated and the role of genetic factors in the etiology of complex diseases is investigated. Classical and new epidemiological study designs that allow an integration of genetic data are introduced. The introduction of this data is partly motivated by the danger of bias due to genetic heterogeneity (population stratification) in classical designs. The problem of replication of study results is discussed and the concept of Mendelian randomization is presented.

Evaluation of the effects of probiotic supplementation from the neonatal period on innate immune development in infancy

BACKGROUND

Activation of the innate immune system by microbial stimulation is believed to be critical for normal immune maturation, and there has been speculation that these pathways are important for inhibiting allergic-immune responses.

OBJECTIVE

To assess innate immune function following a 6-month supplementation with probiotic bacteria.

METHODS

Two hundred and thirty-one allergic, pregnant women were recruited into a randomized, controlled trial. The infants received either a probiotic (Lactobacillus acidophilus LAVRI-A1; Probiomics) or placebo (maltodextrin alone) daily for the first 6 months of life. Mononuclear cell samples were available from 118 infants. Functional responses to toll-like receptor (TLR) were assessed using ligands for TLR2 (Pansorbin) and TLR4/CD14 [lipopolysaccharide (LPS)] and measuring cytokine responses in the supernatants. Antigen-presenting cell function, as well as capacity for cytokine production (IL-12p70 and IL-10) was assessed.

RESULTS

Infants in the probiotic group did not demonstrate differences in innate immune function compared with those in the control group. No differences were seen when cytokine responses were examined following stimulation with Pansorbin (TLR2) or LPS (TLR4). Similarly, no differences were seen in the antigen-presenting capacity of these infants. The mean fluorescence intensities of human leucocyte antigen-DR (HLA-DR) on monocytes, B cells and dendritic cells (DC) subsets were not affected, nor were the percentage of circulating DC subsets affected by a 6-month supplementation with L. acidophilus LAVRI-A1.

CONCLUSIONS

Probiotic supplementation with L. acidophilus for the first 6 months of life did not alter early innate immune responses in this population at high risk of developing allergic disease.

Gene by environment interaction in asthma

Asthma is a chronic inflammatory disease of the airways that is highly prevalent in the Western world. It is a genetically complex disease caused by multiple genetic and environmental factors, which may interact. Genetic research has recently incorporated environmental factors to investigate gene by environment interaction, and the first examples of gene by environment interaction in asthma have been reported. Linkage analyses indicate that one or more genes on chromosome 5q interact with environmental tobacco smoke in infancy in asthma development. Several candidate genes have been consistently shown to interact with the environment. These include the innate immunity genes CD14 and Toll-like receptor 4, and microbial exposures, as well as the detoxifying gene family glutathione-S-transferase and environmental tobacco smoke exposure and air pollutants. Gene by environment interaction is important in asthma pathogenesis, and future studies should take the interaction of both factors into account.

Rat genotype influences quantitative and qualitative aspects of xenogeneic immune response to pig blood mononuclear cells

BACKGROUND

Xenotransplantation seeks to have cells with discordant genotypes co-exist. The hypothesis that host genotype modulates xenogeneic immune response (IR) was tested.

METHODS

Two inbred rat strains [Dark Agouti (DA) and Lewis (LEW)] representing diverse IR phenotypes were immunized with porcine blood mononuclear cells (BMC). Delayed-type hypersensitivity (DTH), immunoglobulin (Ig), antibody (Ab) and isotype bias of Ab response were evaluated.

RESULTS

DTH to pig BMC was greater in DA than in LEW rats. Natural Ab was qualitatively different between strains (IgM and IgA predominated in DA, IgM and IgG(2a) predominated in LEW). Twice as much IgG was elicited from DA than LEW rats and DA utilized all isotypes whereas LEW did not use IgG(2a) or IgG(2c). IR bias was diametrically opposed; type 1 in DA but type 2 in LEW. Strains even differed in Ig profiles and dermal responses to saline injections and mitogen. The DA rats were the higher responders to pig BMC.

CONCLUSIONS

Recipient genotype had significant and broad effects on IR to porcine BMC and may influence xenograft rejection and xenotolerance induction. Moreover, this study suggests that caution should prevail when interpreting data derived from a single inbred strain, particularly given that humans, the target species, are genetically diverse.

The many faces of the hygiene hypothesis

About 15 years have gone by since Strachan first proposed the idea that infections and unhygienic contact might confer protection against the development of allergic illnesses. The so-called hygiene hypothesis has ever since undergone numerous more or less subtle modifications by various researchers in the fields of epidemiology, clinical science, and immunology. Three major tracts have developed exploring the role of overt viral and bacterial infections, the significance of environmental exposure to microbial compounds, and the effect of both on underlying responses of the innate and adaptive immunity. To date, a truly unifying concept has not yet emerged, but various pieces of a complex interplay between immune responses of the host, characteristics of the invading microorganism, the level and variety of the environmental exposure, and the interactions between a genetic background and a range of exposures becomes apparent. These influences are discussed as determinants for a number of complex allergic illnesses in this review, while we attempt to pay attention to the importance of different phenotypes, namely of the asthma syndrome. Even if today practical implications cannot directly be deduced from these findings, there is great potential for the development of novel preventive and therapeutic strategies in the future.

6. Asthma: Factors underlying inception, exacerbation, and disease progression

Asthma is a heterogeneous disorder that is characterized by variable airflow obstruction, airway inflammation and hyperresponsiveness, and reversibility either spontaneously or as a result of treatment. Multiple causes no doubt exist for both its inception and symptom exacerbation once the disease is established. Factors underlying inception can range from viral respiratory tract infections in infancy to occupational exposures in adults. Factors underlying asthma exacerbations include allergen exposure in sensitized individuals, viral infections, exercise, irritants, and ingestion of nonsteroidal anti-inflammatory agents among others. Exacerbating factors might include one or all of these exposures and vary both among and within patients. Asthma treatment is determined to a large extent after an assessment of severity, which can be variable over time and assessed in 2 domains: impairment (current) and risk (long-term consequences). Unfortunately, despite the availability of effective therapies, suboptimal asthma control exists in many patients on a worldwide basis. The future development of novel therapies and treatment paradigms should address these disparities.

Infection, immune responses and the aetiology of childhood leukaemia

Childhood leukaemia is the principal subtype of paediatric cancer and, despite success in treatment, its causes remain enigmatic. A plethora of candidate environmental exposures have been proposed, but most lack a biological rationale or consistent epidemiological evidence. Although there might not be a single or exclusive cause, an abnormal immune response to common infection(s) has emerged as a plausible aetiological mechanism.

Measured Gene-Environment Interactions in Psychopathology: Concepts, Research Strategies, and Implications for Research, Intervention, and Public Understanding of Genetics

There is much curiosity about interactions between genes and environmental risk factors for psychopathology, but this interest is accompanied by uncertainty. This article aims to address this uncertainty. First, we explain what is and is not meant by gene-environment interaction. Second, we discuss reasons why such interactions were thought to be rare in psychopathology, and argue instead that they ought to be common. Third, we summarize emerging evidence about gene-environment interactions in mental disorders. Fourth, we argue that research on gene-environment interactions should be hypothesis driven, and we put forward strategies to guide future studies. Fifth, we describe potential benefits of studying measured gene-environment interactions for basic neuroscience, gene hunting, intervention, and public understanding of genetics. We suggest that information about nurture might be harnessed to make new discoveries about the nature of psychopathology.

Gene-environment interplay and psychopathology: multiple varieties but real effects

Gene-environment interplay is a general term that covers several divergent concepts with different meanings and different implications. In this review, we evaluate research evidence on four varieties of gene-environment interplay. First, we consider epigenetic mechanisms by which environmental influences alter the effects of genes. Second, we focus on variations in heritability according to environmental circumstances. Third, we discuss what is known about gene-environment correlations. Finally, we assess concepts and findings on the interaction between specific identified genes and specific measured environmental risks. In order to provide an understanding of what may be involved in gene-environment interplay, we begin our presentation with a brief historical review of prevailing views about the role of genetic and environmental factors in the causation of mental disorders, and we provide a simplified account of some of the key features of how genes 'work'.

Gene-environment interactions in asthma and allergies: a new paradigm to understand disease causation

The example of complex interactions between environmental exposures and polymorphisms in the CD14 gene in predisposing for allergy-related conditions offers a good indication of the complexity of the mechanisms that determine susceptibility to these conditions. Contrary to what has been the rule for monogenic diseases, the association between genetic variations and polygenic conditions such as asthma and allergies may not always be unidirectional; that is, not always will the same alleles be associated with the conditions under study. Concepts of penetrance of genetic variations that ignore these nonlinear influences (which may affect gene-gene and gene-environment interactions) may hinder a better understanding of mechanisms of disease involved, and therefore may delay the development of preventive strategies for these common conditions. Discrepancies between well-designed genetic studies of asthma and allergies, therefore, may be suggesting something fundamental about how these diseases develop and how it will be possible to abolish them in the future.

Viral infections, cytokine dysregulation and the origins of childhood asthma and allergic diseases

BACKGROUND

The origins of asthma and allergic disease begin in early life for many individuals. It is vital to understand the factors and/or events leading to their development.

METHODS

The Childhood Origins of Asthma project evaluated children at high risk for asthma to study the relationships among viral infections, environmental factors, immune dysregulation, genetic factors, and the development of atopic diseases. Consequently wheezing illnesses, viral respiratory pathogen identification, and in vitro cytokine response profiles were comprehensively evaluated from birth to 3 years of age, and associations of the observed phenotypes with genetic polymorphisms were investigated.

RESULTS

For the entire cohort, cytokine responses did not develop according to a strict T helper cell 1 or T helper cell 2 polarization pattern during infancy. Increased cord blood mononuclear cell phytohemagglutin-induced interferon-gamma responses of mononuclear cells were associated with decreased numbers of moderate to severe viral infections during infancy, especially among subjects with the greatest exposure to other children. In support of the hygiene hypothesis, an increased frequency of viral infections in infancy resulted in increased mitogen-induced interferon-gamma responses at 1 year of age. First year wheezing illnesses caused by respiratory viral infection were the strongest predictor of subsequent third year wheezing. Also, genotypic variation interacting with environmental factors, including day care, was associated with clinical and immunologic phenotypes that may precede the development of asthma.

CONCLUSIONS

Associations between clinical wheezing, viral identification, specific cytokine responses and genetic variation provide insight into the immunopathogenesis of childhood asthma and allergic diseases.

Rethinking genetic models of asthma: the role of environmental modifiers

Asthma is a common, chronic disease with a complex etiology. To date, more than 35 genes have been associated with asthma or related phenotypes in multiple populations, but none of them has been shown to contribute to risk in all populations studied. We suggest that genetic susceptibility is both context dependent and developmentally regulated, and that ignoring the environmental context will miss many important associations and clues to pathogenesis. We define 'environment' broadly to include the in utero environment, maternal affection status and sex, and propose that epigenetic mechanisms are the link between our genes and our environment.

Variation in ITGB3 is associated with asthma and sensitization to mold allergen in four populations

RATIONALE

Recent genetic studies have implicated integrins in asthma and atopy susceptibility. We therefore evaluated the integrin-beta3 gene (ITGB3), an integrin gene within an asthma linkage peak on chromosome 17, as a candidate for susceptibility to asthma- and atopy-related phenotypes.

METHODS AND MEASUREMENTS

We genotyped and performed association tests on 19 single nucleotide polymorphisms in ITGB3 in the Hutterites, a founder population, and in three outbred replication populations.

MAIN RESULTS

Variation in ITGB3 was strongly associated with susceptibility to bronchial hyperresponsiveness and protection from allergic sensitization to mold allergens in this population. Three independent case-control populations representing Caucasians and African Americans were used to replicate this finding, also revealing ITGB3 alleles that are associated with asthma susceptibility and protection from mold allergen sensitization.

CONCLUSIONS

This study provides evidence that ITGB3 plays a role in the pathogenesis of asthma and sensitization to mold allergens.