The genetics of atopy and airway hyperresponsiveness

Serum level of interleukin-24 and its polymorphism in eczematic Iraqi patients

Eczema is a common skin disease associated with inflammation. Interleukin (IL)-24 is crucial in the pathogenesis of inflammatory diseases like eczema. The study objective was the assessment of IL-24 serum levels and its gene polymorphisms in eczematic Iraqi patients. This retrospective case-control study involved 145 participants, divided into 82 patients with eczema and 63 healthy controls. An enzyme-linked immunosorbent assay measured serum IL-24, while polymerase chain reaction and Sanger DNA sequencing were used for genotype analysis. Serum IL-24 level was significantly higher (P value < .001) in patients compared to controls (41.6 [interquartile range (IQR): 28.9-53.6] vs 9.8 [IQR: 0.8-19.6] pg/mL, respectively). DNA sequence illustrated 2 SNPs with polymorphic frequencies (rs1150256 G/A and rs3093425 del/ins). The first SNP (rs1150256 G/A) showed 3 genotypes (GG, AA, and G/A), while the second SNP (rs3093425) showed 3 genotypes (-/G del/Ins, G Ins/Ins, and - del/del). The subsequent investigation revealed the presence of the following findings within the DNA sequence of the PCR amplified region (329bp). In the control group, all participants had GG/G (wild type) genotype/allele for the rs1150256 SNP, while in eczematic patients, 24.4% GG, 50% GA, and 25.6% AA. For the second SNP genotype (rs3093425 del/ins), the genotype frequencies in patients vs control were (24.4% vs 84.1%, 50.0% vs 11.1%, and 25.6% vs 4.8; Del/Del, Del/Ins, and Ins/Ins, respectively). The presence of Ins compared to Del increased the risk of eczema by 8.91 (4.66-17.03); OR (95% CI). In conclusion, IL-24 is a good predictor of eczema and A-allele carrier for rs1150256 SNP, and insertion-allele carrier for rs3093425 SNP is associated with elevated serum IL-24 and higher risk of eczema.

Discriminant analysis and logistic regression on genetic history and environmental factors in children with asthma

BACKGROUND

Asthma is known to be related to genetic and environmental factors, we aimed to identify the predictors discriminating between children with asthma and a control group in order to build typical profiles of these children.

METHODS

A multidimensional analysis covered children (58 with asthma and 217 as control group), under 17 years of age, involving environmental variables and medical history of these children and their families.

RESULTS

Chi-square tests highlighted significant links between variables as rhinitis and conjunctivitis (P<0.001). The results showed, in group of asthmatic children, significant high frequencies of allergies, mainly seasonal (P<0.001), rhinitis, family history more present in mothers (P=0.002) and in maternal aunts and uncles (P<0.02). Allergies were mostly present in mothers of asthmatic children (P=0.03). Children whose father, mother or both had asthma were significantly more numerous in asthmatic group (P=0.0007). A multiple correspondence analysis (MCA) identified two typical profiles of children, a first group of asthmatic children with positive modalities of family history, medical and environmental factors, a second, the control group (nA, non-asthmatic children), with essentially negative modalities of the variables. Logistic regression (LR) resulted in a final model which retained four significant predictors, rhinitis (P=0.01), atopic dermatitis (P=0.04), mother antecedents (P=0.03) and paternal uncle antecedents (P=0.008) with a globally appreciable predictive value (82%) of the Hosmer-Lemeshow Test.

CONCLUSIONS

These results allowed the drafting of a typical profile quantifying through a function of a few predictors, the variation of the probability for a child to develop an asthma.

Multidimensional analysis of genetic background and environmental factors: Cases of atopy in asthmatic children

The present work aimed, through a multidimensional analysis of a data set related to 76 asthmatic children (2-16 years), to their family, and to their antecedents, to establish typical profiles of children with asthma, combining similar or even identical characteristics. A questionnaire was presented to the parents concerning possible consanguinity, prematurity of the child, birth order, skin prick test results, presence of animals, indoor dampness, medical history, and cases of atopy among the children and their antecedents. The links between variables were first identified by means of chi-square tests. Ascending hierarchical classification (AHC) was performed to identify significant groupings. Multiple correspondence analysis (MCA) was then carried out to focus on typical children profiles. The results showed a high frequency of bronchitis (86.9%), rhinitis (46.1%), and indoor dampness (64.5%). Family history (asthma, rhinitis, conjunctivitis, and atopic dermatitis) and various allergies (to drugs, to food, or other allergies in general) were present mostly in mothers (≈20%) with a slightly significant association between mothers and siblings (P=0.045) but not between fathers and siblings (P=0.41). The AHC highlighted two distinct groups, well discriminated: a predominant group with maternal antecedents and another of lesser significance with paternal antecedents. The MCA identified groupings, with positive modalities of variables, largely around boys and paternal antecedents with an impact on girls. This work allowed us to establish a typical profile of children who have developed (or can develop) asthma. They are children with a history of atopy and allergies, mainly of their mothers, who have contracted early bronchitis and probably rhinitis, and who live in an environment with indoor dampness and smoking.

Modest genetic influence on bronchodilator response: a study in healthy twins

Aim

To determine the reasons for large standard deviation of bronchodilator response (BDR) and establish whether there is a potential heritable component in healthy subjects.

Methods

67 monozygotic and 42 dizygotic adult twin pairs were assessed for bronchodilator response (%change in FEV₁ after inhaling 400 µg salbutamol). Univariate quantitative genetic modeling was performed.

Results

Multiple regression modeling showed a significant association between BDR and sex and baseline FEV1 (P < 0.05), while no association was found with smoking habits, body mass index, or age. Within pair correlation in monozygotic twins was modest (0.332), but higher than in dizygotic twins (0.258). Age-, sex-, and baseline FEV1-adjusted genetic effect accounted for 14.9% (95% confidence interval, CI 0%-53.1%) of the variance of BDR, shared environmental effect for 18.4% (95% CI 0%-46.8%), and unshared environmental effect for 66.8% (95% CI 46.8%-88.7%).

Conclusion

Our twin study showed that individual differences in BDR can be mostly explained by unshared environmental effects. In addition, it is the first study to show low, insignificant hereditary influences, independently from sex, age, and baseline FEV1.

A functional brain-derived neurotrophic factor (BDNF) gene variant increases the risk of moderate-to-severe allergic rhinitis

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is a secretory protein that has been implicated in the pathogenesis of allergic rhinitis (AR), atopic asthma, and eczema, but it is currently unknown whether BDNF polymorphisms influence susceptibility to moderate-to-severe AR.

OBJECTIVE

We sought to identify disease associations and the functional effect of BDNF genetic variants in patients with moderate-to-severe AR.

METHODS

Tagging single nucleotide polymorphisms (SNPs) spanning the BDNF gene were selected from the human HapMap Han Chinese from Beijing (CHB) data set, and associations with moderate-to-severe AR were assessed in 2 independent cohorts of Chinese patients (2216 from Shandong province and 1239 living in Singapore). The functional effects of the BDNF genetic variants were determined by using both in vitro and ex vivo assays.

RESULTS

The tagging SNP rs10767664 was significantly associated with the risk of moderate-to-severe AR in both Singapore Chinese (P = .0017; odds ratio, 1.324) and Shandong Chinese populations (P = .039; odds ratio, 1.180). The coding nonsynonymous SNP rs6265 was in perfect linkage with rs10767664 and conferred increased BDNF protein secretion by a human cell line in vitro. Subjects bearing the AA genotype of rs10767664 exhibited increased risk of moderate-to-severe AR and displayed increased BDNF protein and total IgE levels in plasma. Using a large-scale expression quantitative trait locus study, we demonstrated that BDNF SNPs are significantly associated with altered BDNF concentrations in peripheral blood.

CONCLUSION

A common genetic variant of the BDNF gene is associated with increased risk of moderate-to-severe AR, and the AA genotype is associated with increased BDNF mRNA levels in peripheral blood. Together, these data indicate that functional BDNF gene variants increase the risk of moderate-to-severe AR.

Genetic variation in BDNF is associated with allergic asthma and allergic rhinitis in an ethnic Chinese population in Singapore

Allergic diseases affect more than 25% of the world population and result from a complex interplay between genetic and environmental factors. Recent evidence has shown that BDNF (Brain Derived Neurotrophic Factor) could serve as an important marker of allergic disease. Increased levels of BDNF in blood, bronchoalveolar lavage fluid and nasal lavage fluid positively correlate with disease activity and severity in patients with allergic rhinitis (AR), asthma and atopic eczema. However, reports on the association between genetic variation in BDNF and allergic disease have been controversial. This study therefore aims to clarify the relationship between single nucleotide polymorphisms (SNPs) in BDNF and a genetic predisposition to AR and asthma in an ethnic Chinese population of Singapore. Volunteers with a self-reported history of asthma (718 subjects) or a history of AR as determined by a researcher-administered questionnaire (795 subjects) were used in this study, alongside controls with no personal or family history of allergy (717 subjects). The association results identified a significant association for the tagSNP rs10767664 with a significant PDominant=0.0007 and OR=1.3 for AR and PDominant=0.0005 and OR=1.3 for asthma (using a dominant model of association). The haplotype based analysis also identified a significant association further confirming the single SNP association. The SNP rs10767664 is strongly linked (r2=0.95) to the functional polymorphism rs6265 (Val66Met), which has previously been reported to be associated to allergic phenotypes and also shown to affect BDNF expression. BDNF is a therefore a key molecular player in allergy. Further studies on polymorphisms within BDNF may shed light on its role in the pathogenesis of allergic diseases and potentially serve as biomarkers for allergic disease.

Genome-wide association study for atopy and allergic rhinitis in a Singapore Chinese population

Allergic rhinitis (AR) is an atopic disease which affects about 600 million people worldwide and results from a complex interplay between genetic and environmental factors. However genetic association studies on known candidate genes yielded variable results. The aim of this study is to identify the genetic variants that influence predisposition towards allergic rhinitis in an ethnic Chinese population in Singapore using a genome-wide association study (GWAS) approach. A total of 4461 ethnic Chinese volunteers were recruited in Singapore and classified according to their allergic disease status. The GWAS included a discovery stage comparing 515 atopic cases (including 456 AR cases) and 486 non-allergic non-rhinitis (NANR) controls. The top SNPs were then validated in a replication cohort consisting of a separate 2323 atopic cases (including 676 AR cases) and 511 NANR controls. Two SNPs showed consistent association in both discovery and replication phases; MRPL4 SNP rs8111930 on 19q13.2 (OR = 0.69, P(combined) = 4.46×10(-05)) and BCAP SNP rs505010 on chromosome 10q24.1 (OR = 0.64, P(combined) = 1.10×10(-04)). In addition, we also replicated multiple associations within known candidates regions such as HLA-DQ and NPSR1 locus in the discovery phase. Our study suggests that MRPL4 and BCAP, key components of the HIF-1α and PI3K/Akt signaling pathways respectively, are two novel candidate genes for atopy and allergic rhinitis. Further study on these molecules and their signaling pathways would help in understanding of the pathogenesis of allergic rhinitis and identification of targets for new therapeutic intervention.

Risk factors for bronchial hyperresponsiveness in teenagers differ with sex and atopic status

BACKGROUND

Sex-related differences in bronchial hyperresponsiveness (BHR) have been reported in adolescents, but the mechanisms remain obscure.

OBJECTIVE

To investigate the risk factors for BHR in the Raine Study, a community-based longitudinal birth cohort.

METHODS

At 14 years of age, children underwent a respiratory assessment including a questionnaire, lung function testing, methacholine challenge, and determination of atopic status.

RESULTS

A total of 1779 children provided data for assessment, with 1510 completing lung function and methacholine challenge testing. Current asthma was present in 152 (10.4%), 762 (50.5%) were atopic, and 277 (18.6%) had BHR. BHR was more common in girls, whereas atopy was more common in boys, with no sex differences in asthma or current wheeze. Independent risk factors for BHR were being female (odds ratio [OR], 3.45; P < .001), atopy at 14 years (OR, 1.27; P = .004), and current asthma (OR, 2.15; P = .005). Better lung function was protective against BHR (forced expiratory flow between 25% and 75% of forced vital capacity/forced vital capacity, OR, 0.09; P < .001). Risk factors differed with sex and atopic status. Early-life factors were generally not independent risk factors for BHR at 14 years of age, with the exception of being smaller at birth in boys (birth length, OR, 6 × 10(-9); P = .017) and maternal asthma in girls (OR, 1.84; P = .041). Current asthma was not a risk for BHR in nonatopic children.

CONCLUSION

Bronchial hyperresponsiveness was more common and more severe in girls. These differences could not be explained by differences in lung function or atopic status.

Immunological and genetic aspects of asthma and allergy

Prevalence of allergy and allergic asthma are increasing worldwide. More than half of the US population has a positive skin prick test and approximately 10% are asthmatics. Many studies have been conducted to define immunological pathways underlying allergy and asthma development and to identify the main genetic determinants. In the effort to find missing pieces of the puzzle, new genomic approaches and more standardized ones, such as the candidate gene approach, have been used collectively. This article proposes an overview of the actual knowledge about immunological and genetic aspects of allergy and asthma. Special attention has been drawn to the challenges linked to genetic research in complex traits such as asthma and to the contribution of new genomic approaches.

Association of the cysteinyl leukotriene receptor 1 gene with atopy in the British 1958 birth cohort

BACKGROUND

Cysteinyl leukotrienes (CysLTs) play an important role in the pathophysiology of many allergic inflammatory disorders. However, data on the contribution of genetic variability of the cysteinyl leukotriene receptor 1 gene (CYSLTR1) in asthma and atopy remain conflicting.

OBJECTIVE

We investigated the association of polymorphisms of interest located at this locus and allergic disease prevalence in a national population with an established DNA archive, the British 1958 birth cohort.

METHODS

The British 1958 birth cohort comprises all persons born in Britain during 1 week in 1958. Asthma, wheezy bronchitis, and wheezing were ascertained by interview at ages 7, 11, 16, 23, 33, and 42 years. At age 44 to 45 years, serum total circulating IgE levels were measured and atopy was defined as a serum total IgE level of greater than 30 kU/L and specific IgE levels to 1 or more of dust mite, cat fur, and mixed grass of greater than 0.3 kU/L. DNA samples from 8018 participants were genotyped for 2 variants of the CYSLTR1 promoter (Xq13-Xq21).

RESULTS

The rare polymorphism C > T (rs7066737) was not associated with any of the phenotypes studied. The common promoter polymorphism A > G (rs2806489) was not associated with total IgE levels or the prevalence or age of onset of asthma, wheezy bronchitis, or wheeze. However, the wild-type allele A was significantly associated with atopy in female subjects (chi(2) = 8.30, P = .004), although not in male subjects (P = .841).

CONCLUSIONS

These data suggest that a CYSLTR1 polymorphism previously shown to affect the gene transcription in vitro might influence the risk of atopy in the female white population with suggestive evidence of heterozygote vigor.

Duration of postviral airway hyperresponsiveness in children with asthma: effect of atopy

Background

Respiratory viruses induce asthma exacerbations and airway hyperresponsiveness (AHR). Atopy is an important risk factor for asthma persistence.

Objective

We sought to evaluate whether atopy is a risk factor for prolonged AHR after upper respiratory tract infections (URIs).

Methods

Twenty-five children (13 atopic and 12 nonatopic children) with intermittent virus-induced asthma were studied. Clinical evaluation, skin prick tests, methacholine bronchoprovocation, questionnaires, and a nasal wash specimen were obtained at baseline. For 9 months, subjects completed diary cards with respiratory symptoms. During their first reported cold, a nasal wash specimen was obtained. Methacholine provocation was performed 10 days and 5, 7, 9, and 11 weeks later. In case a new cold developed, the provocation schedule was followed from the beginning.

Results

Viruses were detected in 17 (68%) of 25 patients during their first cold, with rhinovirus being most commonly identified (82%). AHR increased significantly 10 days after the URI, equally in both groups (P = .67), and remained so up to the fifth week. Duration of AHR in subjects experiencing a single URI ranged from 5 to 11 weeks, without a significant difference between groups. In the duration of the study, atopic children experienced more colds and asthma exacerbations than nonatopic children. Thus for duration of AHR, significant prolongation was noted in the atopic group when assessed cumulatively.

Conclusion

In asthmatic children the duration of AHR after a single natural cold is 5 to 11 weeks. However, an increased rate of symptomatic cold and asthma episodes in atopic children is associated with considerable cumulative prolongation of AHR, which might help explain the role of atopy as a risk factor for asthma persistence.

Familial correlations and inter-relationships of four asthma-associated quantitative phenotypes in 320 French EGEA families ascertained through asthmatic probands

Asthma is a complex disease, associated with biological and physiological phenotypes including immunoglobulin E (IgE) levels, sum of positive skin prick tests to allergens (SPTQ), eosinophil counts (EOS) and percent predicted forced expiratory volume in 1 s (%FEV1). We investigated the patterns of familial correlations and the inter-relationships of these four quantitative phenotypes, using the general class D regressive model, in 320 French EGEA nuclear families ascertained through 204 offspring (set A) and 116 parents (set B). Familial correlations of IgE and SPTQ were consistent with a model including no spouse correlation and equal parent-offspring and sib-sib correlations (rhoPO = rhoSS = 0.25 for IgE and 0.15 for SPTQ), this model being compatible with an additive polygenic model in the whole sample and the two family subsets A and B. Different patterns of familial correlations of EOS and %FEV1 were observed in these two sets. In set A, the best fitting model included no spouse correlation and equality of parent-offspring and sib-sib correlations (rhoPO = rhoSS = 0.14 for EOS and 0.23 for %FEV1). In set B, EOS had only a significant rhoSS of 0.28, while %FEV1 had significant rhoMO of 0.28 and rhoSS of 0.16. Analysis of shared familial determinants between these phenotypes indicated an overlap of at most 30% in rhoFO for IgE and SPTQ and in both rhoFO and rhoMO for IgE and EOS, while determinants of %FEV1 and atopy-related phenotypes appear distinct. These results may have implications for further linkage and association studies with genetic markers.

Evaluation of risk factors for asthma in Taipei City

BACKGROUND

Asthma has rarely been studied by evaluating all of its trigger factors in 1 study population. Thus, correlations between the concentration of allergen immunoglobulin (Ig) E antibodies and airway limitation or asthma severity remain unclear.

METHODS

Five hundred and seventy-nine asthmatic patients were enrolled, and serum specific IgE antibodies to allergens were analyzed. All suspected trigger factors were assessed by questionnaire, case histories over a 4-year period, and diary card recordings; possible trigger factors were then re-evaluated.

RESULTS

Antibodies to the following allergens were found: Dermatophagoides pteronyssinus (59.8% of patients), D. microceras (58.8%), D. farinae (56.8%), cockroach (38.3%), dog dander (26.3%), Candida albicans (13.3%), cat dander (10%), and Cladosporium herbarum (6.6%). A greater prevalence of allergy to dog and cat dander was found than previously. Younger patients were more often positive for mite allergens, and had higher titers of antibodies against such allergens, than older patients. Further, females had a lower concentration of mite allergen antibodies than males. No correlation between the concentration of allergen antibodies and forced expiratory volume in 1 second (FEV1), or the ratio of FEV1:forced vital capacity (FEV1:FVC), was found. In addition, there was no significant change in antibody titers with varying asthma severity. Non-allergenic trigger factors were irritant air inhalants (94.6% of patients), respiratory infection (92.2%), exercise (75.2%), emotional factors (58.8%), drugs and chemical substances (16%).

CONCLUSION

There are multiple trigger factors in asthma. Allergenic trigger factors are more common in younger than older patients, whereas non-allergenic trigger factors are more common in older patients. There was no linear correlation between the concentration of specific IgE antibodies and asthma severity or airway limitation; therefore, to prevent asthma attacks in individual asthmatic patients, greater attention should be paid to avoiding all potential trigger factors, and not just house dust mite allergens.

An immunoepidemiological approach to asthma: identification of in-vitro T-cell response patterns associated with different wheezing phenotypes in children

BACKGROUND

Increasing evidence suggests that patterns of T-cell immunity to inhalant allergens in genetically diverse human populations are more heterogeneous than previously assumed, and that covert differences in expression patterns might underlie variations in airway disease phenotypes. We tested this proposition in a community sample of children.

METHODS

We analysed data from 172 individuals who had been recruited antenatally to a longitudinal birth cohort study. Of the 194 birth cohort participants, data from the 147 probands (age range 8.6-13.5 years) who consented to blood collection were included along with data from 25 consenting siblings (mean age 11 years [range 7.4-17.4]). We ascertained clinical phenotypes related to asthma and allergy. We measured T-cell responses to allergens and mitogens, together with blood eosinophils and IgE/IgG antibodies, and assessed associations between these indices and clinical phenotypes.

FINDINGS

Atopy was associated with allergen-specific T-helper (Th)2 responses dominated by interleukin 4, interleukin 5, interleukin 9, interleukin 13, whereas interleukin 10, tumour necrosis factor alpha, and interferon gamma responses were common to both atopics and non-atopics. The wheal size from skin prick with allergen was positively associated with in-vitro interleukin 5 and interferon gamma responses, and negatively associated with interleukin 10. Asthma, especially in atopics, was strongly associated with eosinophilia/interleukin 5, and bronchial hyper-responsiveness (BHR) was associated with eosinophilia plus polyclonal interferon gamma production. BHR in non-atopics was associated with elevated allergen-specific and polyclonal interleukin 10 production.

INTERPRETATION

Parallel immunological and clinical profiling of children identified distinctive immune response patterns related to asthma and wheeze compared with BHR, in atopics non-atopics. Immunological hyper-responsiveness, including within the Th1 cytokine compartment, is identified as a hallmark of BHR.

RELEVANCE TO PRACTICE

These findings highlight the heterogeneity of immune response patterns in asthmatic children, including those with seemingly homogeneous Th2-driven atopic asthma. Further elucidation of the covert relationships between wheezing phenotypes and underlying immunophenotypes in this age group will potentially lead to more effective treatments for what is an unexpectedly heterogeneous collection of disease subtypes.

The upper and lower airway responses to nasal challenge with house-dust mite Blomia tropicalis

BACKGROUND

The house dust mite Blomia tropicalis (B. tropicalis) was found to be the most prevalent domestic mite in Singapore. However, its pathogenicity in allergic airway diseases remains to be investigated.

METHODS

Twenty adults with persistent allergic rhinitis (PAR) were studied. Five had a history of asthma, and all were asymptomatic except one who was under treatment with low-dose inhaled corticosteroid. Nasal challenge was carried out by nasal spray with phosphate-buffered saline (PBS) and with increasing concentrations of crude B. tropicalis extracts (0.6, 6.0 and 60 micro g/ml) at 15 min intervals. Subjective symptom scores and absolute number of sneezes were recorded together with objective measurements of spirometry (forced expiratory volume in 1 s, FEV1) and acoustic rhinomanometry (volume of the nasal cavity). These were performed at baseline, 5 min after each incremental challenge, and 30 min, 1 h, 3 h, 5 h and 7 h after the last challenge. Meanwhile, concentrations of mediators in nasal secretions (tryptase, leukotriene C4 (LTC4) and eosinophil cationic protein (ECP)) were measured in nasal aspirate samples at similar time intervals. An identical (control) challenge procedure with PBS alone was repeated in seven patients after a washout period of at least 2 weeks.

RESULTS

Significant increases in the subjective and objective nasal symptoms, together with a significant increase of tryptase and LTC4 concentrations in nasal secretion, were found 5 min after each challenge with B. tropicalis, but not with PBS. There was no definitive pattern of the late-phase nasal response in either subjective symptoms or objective measurements. Three patients (3/5) with a history of asthma showed a fall in FEV1 readings (33%, 22% and 11% from baseline, respectively) at 7 h post challenge with concomitant mild wheezing in the night.

CONCLUSIONS

Our study demonstrates direct evidence of allergic nasal response to B. tropicalis in sensitized adults. It shows that nasal provocation may also provoke concomitant asthmatic symptoms during the late-phase reaction, especially in people with a history of asthma.

The effect of bacillus Calmette-Guérin immunization depends on the genetic predisposition to Th2-type responsiveness

The aim of this study was to investigate whether the effect of bacillus Calmette-Guérin (BCG) immunization on ovalbumin-induced allergic inflammation in a rat model depends on the genetic predisposition to react with a T helper cell (Th) 2-type cytokine response. This study was performed in an inbred Th2-predisposed "asthma prone" rat strain (brown Norway [BN]) and in an outbred nonpredisposed strain (Sprague Dawley [SD]), to differentiate between genetic and environmental factors. BCG decreased numbers of lung eosinophils and macrophages in the SD rat. This effect was not seen in the BN rat. In the BN rat, but not in the SD rat, BCG downregulated levels of total serum IgE. No significant differences were found with respect to frequencies of IFNgamma- or interleukin-4-producing cells in the lung in both rat strains. These results indicate that the degree and pathway of immunomodulatory effect of BCG in two genetically different rat strains is dependent on the genetic predisposition to develop a Th2-type response. Therefore, differences in genotype in relation to environment may result in difference in involvement of contributing pathogenic factors and thus different responsiveness to therapeutic strategies.

Glutathione S-transferase GSTP1 is a susceptibility gene for occupational asthma induced by isocyanates

BACKGROUND

Polymorphism at the pi class glutathione-S-transferase locus (GSTP1) is associated with allergen-induced asthma and related phenotypes.

OBJECTIVE

We sought to determine whether GSTP1 polymorphism influences susceptibility to asthma induced by toluene diisocyanate (TDI).

METHODS

The role of GSTP1 was assessed in 131 workers exposed to TDI, 92 with TDI-induced asthma and 39 asymptomatic subjects. The phenotype of the disease was characterized by using detailed clinical history, lung volumes, airway responsiveness to methacholine, and airway responsiveness to TDI. GST genotypes were determined by using PCR-based assays.

RESULTS

In patients exposed to TDI for 10 or more years, the frequency of the GSTP1 Val/Val genotype was lower in subjects who had asthma (odds ratio, 0.23; 95% confidence interval, 0.05-1.13; P =.074). Similarly, the frequency of this genotype was significantly lower in subjects with evidence of moderate-to-severe airway hyperresponsiveness to methacholine compared with the frequency in subjects with normal or mild hyperresponsiveness (P =.033).

CONCLUSION

These data suggest that homozygosity for the GSTP1*Val allele confers protection against TDI-induced asthma and airway hyperresponsiveness. This view is supported by the finding that the protective effect increases in proportion to the duration of exposure to TDI.

The IL-1beta genotype carries asthma susceptibility only in men

One proinflammatory cytokine possibly implicated in the pathogenesis of asthma is IL-1beta. We analyzed the polymorphism of the IL-1beta gene (single nucleotide exchange at position -511) in a cohort of 245 patients with asthma (mean age, 58 years; age range, 31-84 years) and 405 controls. There were no differences in the allele frequencies. However, in men the genotype distribution differed significantly between asthmatic and control subjects (P =.03). The number of 1.2 heterozygotes was decreased in the patient group (P =.01). In subgroup analysis, the genotype distributions between cases and controls proved significantly different only in men with lower serum IgE (<100 IU/mL; P =.009). The odds ratio of the 1.2 heterozygote men was 0.37 (95% CI, 0.19-0.71). Thus in the case of men the effect of the IL-1beta locus is clear, whereas in women there is no effect. In men this might make a significant contribution to the total asthma prevalence because of the high number of functional genotypes (ie, 50/50 IL-1beta homozygote/heterozygote ratio).

Risk factors for onset and remission of atopy, wheeze, and airway hyperresponsiveness

BACKGROUND

Although many children with asthma may have a remission as they grow and other children who did not have asthma may develop asthma in adult life, knowledge about the factors that influence the onset and prognosis of asthma during adolescence and young adulthood is very limited.

METHODS

A cohort of 8-10 year old children (n=718) living in Belmont, New South Wales, Australia were surveyed six times at 2 yearly intervals from 1982 to 1992, and then again 5 years later in 1997. From this cohort, 498 subjects had between three and seven assessments and were included in the analysis. Atopy, airway hyperresponsiveness (AHR), and wheeze in the last 12 months were measured at each survey. Late onset, remission, and persistence were defined based on characteristics at the initial survey and the changes in characteristics at the follow up surveys.

RESULTS

The proportion of subjects with late onset atopy (13.7%) and wheeze (12.4%) was greater than the proportion with remission of atopy (3.2%) and wheeze (5.6%). Having atopy at age 8-12 years (OR 2.8, 95% CI 1.5 to 5.1) and having a parental history of asthma (OR 2.0, 95% CI 1.02 to 4.13) were significant risk factors for the onset of wheeze. Having AHR at age 8-12 years was a significant risk factor for the persistence of wheeze (OR 4.3, 95% CI 1.3 to 15.0). Female sex (OR 1.9, 95% CI 1.01 to 3.60) was a significant risk factor for late onset AHR whereas male sex (OR 1.9, 95% CI 1.1 to 2.8) was a significant risk factor for late onset atopy.

CONCLUSIONS

The onset of AHR is uncommon during adolescence, but the risk of acquiring atopy and recent wheeze for the first time continues during this period. Atopy, particularly present at the age of 8-10 years, predicts the subsequent onset of wheeze.