Use of cohorts with extensive longitudinal data in investigating the molecular genetics of asthma

Recent studies have associated several chromosomal regions and specific polymorphisms with asthma, atopy and airway hyperresponsiveness. Most of these studies have been cross-sectional which substantially limits their power to analyse genotype/phenotype associations. Asthma is a such a highly variable condition that future genotype/phenotype studies should use longitudinal data. Populations with extensive long-term longitudinal data will facilitate more precise definition of phenotype and allow analysis of asthma's natural history. Longitudinal information also means that each phenotypic attribute can be quantified and considered with respect to age. Collecting longitudinal data prospectively would be extremely expensive and take many years. Using existing longitudinal data sets would clearly be much quicker and more economical, but there are very few suitable data sets to be found. Studying a normal and an asthmatic population is ideal and would provide complementary genotype/phenotype information. This approach is a logical step to using the genotypic information obtained from cross-sectional molecular genetic studies to more critically establish the effect of genotype on phenotype.     

The association between atopy and asthma in a semirural area of Tanzania (East Africa)

BACKGROUND: Atopy is consistently associated with asthma, except in a study in Africa. We assessed the association between atopy and asthma in women from a semirural area of Tanzania (East Africa). METHODS: All pregnant women delivering at the district hospital during a 1-year period were recruited (n = 658, 60.6% of those selected). Asthma was investigated by a standard questionnaire and atopy by specific IgE (immunoglobulin E) antibodies to Dermatophagoides pteronyssinus (Der p 1) and cockroach. RESULTS: The prevalence of wheezing chest was 10.7%; of asthma, 3.5%. Levels of specific IgE of >0.35 kU/l (73%) and high levels of total IgE (62% higher than 1000 kU/l) were highly prevalent. Specific IgE antibody levels in sera were not associated with asthma (3.8% of women with negative specific IgE to any antigen had asthma in comparison to 4.0% of women with positive specific IgE; odds ratio [OR] = 1.06, 0.35-3.22). Total IgE was not different between women with asthma and women without asthma (P=0.36). CONCLUSIONS: In tropical regions, the association between allergy and asthma is complex, and specific IgE reactivity to environmental allergens may not be related to asthma.     

The complexities of defining atopy in severe childhood asthma

Background Defining atopy in children with severe, therapy‐resistant asthma is complex. There is currently no gold standard test; both skin prick testing (SPT) and allergen‐specific IgE (sIgE) are used. Furthermore, atopy is increasingly considered to be a spectrum, not an all‐or‐none phenomenon. Hypothesis SPTs and sIgE cannot be used interchangeably, and if both tests are not performed, opportunities for intervention will be missed. Furthermore, the severity of atopy will be defined differently by the two tests. Methods Cross‐sectional study of 47 children with severe, therapy‐resistant asthma, mean age 11.8 years, range 5.3–16.6 years, who underwent SPT, and measurement of total and sIgE as part of their clinical work‐up. Results Overall, 42/47 (89%) were atopic (defined as either one positive SPT or sIgE). There was 98% concordance between the two tests in classifying atopy. When each allergen was considered individually, in 40/200 (20%), the SPT and sIgE results were discordant, most commonly in 25/200 (12.5%), the SPT was negative and the sIgE was positive. House dust mite and cat sensitization were more likely detected by sIgE, but dog sensitization by SPT. When atopy was quantified, the sum of sIgEs compared with the sum of SPT weal diameter showed a moderate correlation (r²=0.44, P<0.001). Total IgE increased with an increasing number of positive sIgEs (P=0.028), but not significantly with increasing numbers of positive SPTs. Conclusion and Clinical Relevance SPT and sIgE identify group prevalence of atopy equally well; however, for individual allergens, concordance is poor, and when used to quantify atopy, SPTs and sIgE were only moderately correlated. In a clinical setting, if allergen avoidance is contemplated in children with severe, therapy‐resistant asthma, both tests should be performed in order to detect sensitization. Cite this as: J. Frith, L. Fleming, C. Bossley, N. Ullmann and A. Bush, Clinical & Experimental Allergy, 2011 (41) 948–953.     

Sibling effect on atopy in children of patients with asthma.

BACKGROUND: Multiple population studies have shown the presence of a sibling effect on atopic disease. However, it is unclear if the sibling effect is also of importance in subjects who are genetically at high risk for the development of atopy. OBJECTIVE: To study the presence of a sibling effect on markers of atopy (serum total IgE, specific IgE, skin tests) and asthma (bronchial hyper-responsiveness to histamine) in families ascertained through a parent with asthma. METHODS: First-degree offspring in 200 asthma families were studied (n = 541). Mixed effects regression models were used to account for the dependence of the observations within a family, and to adjust for possible confounding variables. RESULTS: Multiple regression analysis showed that having older siblings was inversely related to atopy, defined as >/= 2, >/= 3, >/= 4, or >/= 5 skin tests (P = 0.07-0.009). In addition, family size (number of siblings) had a significant protective effect on the presence of specific IgE to common aeroallergens (P = 0.03). Exposure to cigarette smoke in the first 3 years of life significantly increased the risk of having specific IgE to common aeroallergens (P = 0.04). No sibling effect was detected for serum total IgE or bronchial hyper-responsiveness to histamine. CONCLUSIONS: This study shows a protective sibling effect on the presence and severity of atopy but not on bronchial hyper-responsiveness in children who are genetically at risk. The identification of the sibling effect in high-risk families stresses the need to understand the basis of this effect, in order to design future prevention programmes.     

Serum IgE levels, atopy, and asthma in young adults: results from a longitudinal cohort study

To explore the natural history of asthma and its relation to allergic responses, we examined the relation between total serum IgE in early adulthood and a history of respiratory symptoms, airway hyperresponsiveness (AHR), and atopy during childhood. We studied 180 subjects aged 18–20 years who had been studied since the age of 8–10 years. We measured wheeze in the previous year by questionnaire, AHR by histamine inhalation test, atopy by skin prick tests, and serum IgE levels by immunoassay. Subjects with AHR in early adulthood had higher IgE levels (mean 257.0 IU/ml) than subjects with past AHR (mean 93.3 IU/ml) or with lifelong normal responsiveness (mean 67.6 lU/ml) ( P< 0.001). Subjects who had symptoms had higher IgE levels (mean 125.9 IU/ml) than those who were lifelong asymptomatic (mean 63.1 IU/ml) ( P< 0.001). Recent wheeze, AHR, and allergic sensitization all had a positive relation to serum IgE, but IgE was not more predictive of AHR than skin prick tests. The finding that young adults who are sensitized to common allergens are highly likely to have AHR even in the absence of symptoms is further evidence of the fundamental role of IgE-mediated responses in the natural history of AHR throughout childhood and into adulthood.     

哮喘家系的特应质性状遗传学分析

目的 对哮喘家系的特应质性状进行遗传分析.方法 收集哮喘家系,对所有人进行血清IgE的测定、皮肤挑刺试验和支气管激发试验.结果 ①家系内哮喘病人和正常人SPT阳性有显著差异(P<0.05).②血清总IgE增高个体SPT阳性百分数为76%,在正常个体SPT阳性百分数为53%,在两组之间有显著的差异(P<0.05).③父母双方均为SPT阳性其子女SPT的阳性率为85.7%,父亲为SPT阳性而母亲正常其子女SPT的阳性率为81.8%,父亲正常母亲为SFT阳性其子女SPT的阳性率为63.6%,父母中任一方SPT阳性与父母SPT均正常其子女SPT阳性率比较有显著差异(P<0.05).结论 哮喘家系中病人特应质更明显;血清总IgE升高与SPT阳性有相关性.父母双方特应质对其子女特应质的影响最大.     

Polymorphisms in eosinophil pathway genes, asthma and atopy

BACKGROUND: Eosinophilic inflammation is considered to play an important role in the development as well as in the perpetuation of asthma. As eosinophil production and survival is under genetic control we investigated whether polymorphisms in eosinophil regulation pathway genes (IL-3, IL-5, GM-CSF and their respective enhancers and receptors) may influence the development of atopic diseases. METHODS: In two large study populations of children, the German part of the International Study of Asthma and Allergy in Childhood (ISAAC II) and the German Multicentre Atopy Study (MAS), 3099 and 824 children, seven polymorphisms previously associated with the development of atopic diseases were genotyped: two in and around the GM-CSF gene (Ile117Thr and T3085G), one in IL-3 (Pro27Ser), in IL-5 (C-746T), and in the IL-5 high affinity receptor chain IL-5R (G-80A) and two in the common receptor chain CSFR2b for IL-3, IL-5, and GM-CSF (Asp312Asn and Glu249Gln). Statistical analyses were performed using chi-squared tests and variance analyses. Gene by gene interactions were evaluated in logistic regression models. RESULTS: The T allele at position -746 in the IL-5 gene was significantly protective for atopy in the ISAAC II population (P = 0.006). Furthermore, the risk for atopic asthma was decreased in carriers of the T allele (P = 0.036) and evidence for interaction with the enhancer polymorphism 3085 bp 3' of GM-CSF was detected. CONCLUSIONS: IL-5 C-746T influenced atopic outcomes and showed evidence for gene by gene interaction. No significant associations were found with all other tested polymorphisms in the eosinophil regulation pathway after correction for multiple testing.     

Linkage to atopy on chromosome 19 in north-eastern Italian families with allergic asthma

BACKGROUND: Allergic asthma is a multifactorial disease for which there is a widely assessed, although poorly understood, genetic involvement. Genome-wide screens reported evidence for linkage of allergic asthma-related phenotypes to several chromosomal locations. Markers on chromosome 19 have been linked to allergic asthma phenotypes in different populations in independent studies. OBJECTIVE: The aim of this study was to perform a genetic linkage analysis on chromosome 19 to search for DNA markers linked to phenotypes related to allergic asthma. METHODS: Using non-parametric multipoint linkage analysis on a total of 22 random DNA markers in 2 stages, a sample of 111 families (542 subjects) from north-eastern Italy, recruited through an asthmatic allergic proband, was investigated. Phenotypes examined were: clinical asthma, total serum elevated IgE, skin prick test positivity, bronchial hyper-responsiveness, and atopy defined as skin prick test positivity and/or elevated IgE. Simulation studies were performed to confirm the significance of the results. RESULTS: A novel linkage of atopy and skin prick test positivity to marker D19S601 (19q13.3) was found. Modest evidence for linkage of atopy, skin prick test positivity, and IgE was also found to marker D19S591 (19p13.3). Simulation analysis for atopy gave an NPL-Z > 3.326 in 2 replicates out of 1000 (P = 0.002) for D19S601, and an NPL-Z > 2.56 in 16 replicates out of 1000 (P = 0.016) for D19S591. CONCLUSIONS: On chromosome 19, suggestive linkage of atopy and skin prick test positivity with marker D19S601 (19q13.3) and modest evidence of linkage of marker D19S591 (19p13.3) to the atopic phenotypes investigated were found. These results suggest that these regions may contain susceptibility loci associated to atopic phenotypes.     

The relation of markers of fetal growth with asthma, allergies and serum immunoglobulin E levels in children at age 5–7 years

BACKGROUND: It has been suggested that fetal growth and maturation have an impact on the development of allergic diseases later in life. OBJECTIVE: To examine the association between measures of fetal growth and allergic disease in children at age 5-7 years. METHODS: As part of the German International Study of Asthma and Allergies in Childhood phase II surveys, a random sample of school beginners (n=1138) was examined in 1995. Data on anthropometric measures at birth and gestational age were obtained from maternal copies of birth records. Data on symptoms and doctor-diagnosed asthma, atopic dermatitis and hayfever were gathered by parental questionnaires. Atopic sensitization was assessed by serum IgE and skin prick tests to common aeroallergens. Children (741) had complete data for the explanatory variables of interest and were thus eligible for this analysis. Confounder-adjusted prevalence odds ratios (PORs) and means ratios with 95% confidence intervals (CI) were calculated using multiple logistic and linear regression. RESULTS: Birth weight and gestational age were positively associated with atopic sensitization (Ptrend=0.025 and 0.035, respectively). Children with a low birth weight relative to head circumference had a decreased risk of sensitization (POR 0.44, 95% CI 0.21-0.91; Ptrend=0.020). Moreover, total serum IgE increased with increasing birth weight (Ptrend=0.042). No consistent relationship was observed between markers of fetal growth and wheezing, doctor-diagnosed asthma, atopic dermatitis and hayfever. CONCLUSION: These data suggest that fetal growth and maturity are associated with atopic sensitization and total serum IgE levels in childhood.     

Apoptosis signals in atopy and asthma measured with cDNA arrays

A variety of studies have stressed the importance of the control of inflammatory cell longevity and the balance of pro-survival and pro-apoptotic signalling. Recently, asthma was found to be associated with reduced apoptosis of inflammatory cells in lung tissue. The aim of the study was to investigate the systemic activation of apoptosis pathways using cDNA array technology in atopy and asthma. Eighteen atopic asthmatics (AA), eight atopic non-asthmatic (AN) and 14 healthy control subjects (C) were included in the study. Peripheral blood mononuclear cells were separated with gradient centrifugation, mRNA purified and the reverse-transcribed probes hybridized to cDNA arrays. The signals were compared by standardizing to the 100 most expressed genes and group differences assessed with the Mann-Whitney U-test. We found a concerted up-regulation of several pro-survival cytokines and growth factors in AN and AA. FAS and FASL were not differentially expressed, but FAST kinase was over-expressed in AN and AA. The tumour necrosis factor pathway was activated in AN and AA with increased cytokine and receptor levels and increased TRAF2, an intracellular signalling product. There were indications of a down-regulated p53 system. In contrast, the Bcl-2 family of genes showed a net pro-apoptotic profile in AN and AA. The group of caspases showed a constant gene expression pattern in all groups. In conclusion, significant differences in the expression of apoptosis-related genes were found in peripheral blood of atopic individuals with and without asthma. cDNA array technology proved to be useful and may be complementary to DNA-based studies in order to analyse interactive and multidimensional pathways as shown here for apoptosis.     

No association between vitamin D and atopy,asthma, lung function or atopic dermatitis: a prospective study in adults

Studies suggest that vitamin D may be involved in the pathogenesis of allergic disorders, asthma and decreased lung function. However, results are inconsistent and only few prospective studies have examined adults. The purpose of this study was to investigate the association of serum 25‐hydroxy vitamin D (s25(OH)D) with atopy, atopic dermatitis (AD), asthma, wheezing and impaired lung function in a prospective study of Danish adults. A random sample of 3471 persons was examined in 2006–2008. Of these, 2308 were re‐examined 5 years later. s25(OH)D and specific IgE against four common inhalant allergens were measured by standard procedures. Wheezing, asthma and AD were assessed from questionnaires and lung function was measured by spirometry. We found no statistically significant associations between s25(OH)D and prevalence or incidence of atopy, AD, asthma or wheezing. Associations with lung function were inconsistent. We conclude that vitamin D status does not influence these conditions in adults.     

Meta-analysis of 20 genome-wide linkage studies evidenced new regions linked to asthma and atopy

Asthma is caused by a heterogeneous combination of environmental and genetic factors. In the context of GA2LEN (Global Allergy and Asthma European Network), we carried out meta-analyses of almost all genome-wide linkage screens conducted to date in 20 independent populations from different ethnic origins (≥3024 families with ≥10 027 subjects) for asthma, atopic asthma, bronchial hyper-responsiveness and five atopy-related traits (total immunoglobulin E level, positive skin test response (SPT) to at least one allergen or to House Dust Mite, quantitative score of SPT (SPTQ) and eosinophils (EOS)). We used the genome scan meta-analysis method to assess evidence for linkage within bins of traditionally 30-cM width, and explored the manner in which these results were affected by bin definition. Meta-analyses were conducted in all studies and repeated in families of European ancestry. Genome-wide evidence for linkage was detected for asthma in two regions (2p21–p14 and 6p21) in European families ascertained through two asthmatic sibs. With regard to atopy phenotypes, four regions reached genome-wide significance: 3p25.3–q24 in all families for SPT and three other regions in European families (2q32–q34 for EOS, 5q23–q33 for SPTQ and 17q12–q24 for SPT). Tests of heterogeneity showed consistent evidence of linkage of SPTQ to 3p11–3q21, whereas between-study heterogeneity was detected for asthma in 2p22–p13 and 6p21, and for atopic asthma in 1q23–q25. This large-scale meta-analysis provides an important resource of information that can be used to prioritize further fine-mapping studies and also be integrated with genome-wide association studies to increase power and better interpret the outcomes of these studies.     

IL15 gene variants are not associated with asthma and atopy

Background:  Interleukin 15 (IL15) promotes activation and proliferation of CD8+ T cells and enhances the differentiation into Th2 cells. A previous study described five polymorphisms in the IL15 gene to be associated with asthma in a haplotype analysis.
Aim:  We selected HapMap tagging single nucleotide polymorphisms (SNPs) from IL15 to systematically investigate these IL15 associations in a large population-based sample.
Methods:  Genotyping of seven IL15 SNPs was performed using MALDI-TOF MS in a cross-sectional study population of 3099 children from Dresden or Munich (age 9–11 years). All children were phenotyped by standardized and validated protocols for atopic phenotypes. Effects of single SNPs and haplotypes were studied using sas 9.1.3 and haploview . Equivalence tests were performed to prove the significance of negative results.
Results:  Neither single IL15 polymorphisms nor haplotype analyses showed associations with asthma or atopy after correction for multiple testing.
Conclusion:  These results do not confirm previous case–control studies and suggest that IL15 gene variants do not play an important role in the development for asthma or other atopic disorders.     

Birth order, atopy, and symptoms of allergy and asthma among inner-city children attending Head Start in New York City

Background In past research, children with older siblings were more likely than others to wheeze at age 2 years, but less likely by age 6 years. Higher infection transmission and a down‐regulated allergic immune response as a result of these infections, respectively, were suggested as the causes. However, in a study of children aged 0–3 years in a low‐income urban community in New York City, USA, with high asthma prevalence, we observed no birth‐order effect. Objective To evaluate the association between birth order and atopy and respiratory symptoms in 4‐year‐old children attending Head Start programs in NYC. Methods Respiratory symptoms were assessed by questionnaire for 1005 children (mean age 4.0 years) living in high asthma prevalence neighbourhoods. Serum was collected from a subgroup of the children (n=494) and specific IgE responses to dust mite, cockroach, mouse, and cat allergens were measured. Results Prevalence of specific IgE (0.35 IU/mL) did not differ significantly among first (35%), second (35%), and later‐born children (28%) (P=0.23). Increasing birth order was associated with increasing prevalence of respiratory symptoms in the prior year, including wheeze (first 20%, second 27%, third or later 35%; P<0.001), being awakened at night by cough (28%, 33%, 38%; P=0.005), emergency department visits (14%, 17%, 21%; P=0.02) and hospitalizations for difficulty breathing (6.1%, 6.6%, 10%; P=0.04). The associations of birth order with respiratory symptoms were statistically significant only for the non‐seroatopic children and those without an asthmatic parent. Conclusions Non‐seroatopic children with older siblings were more likely than those without older siblings to have respiratory symptoms at age 4 years. Although the stability of these associations over time remains to be determined, the differences in findings between this study and our previous NYC birth cohort study suggest that patterns of asthma development may vary even among low‐income populations within the same city.     

Genetic susceptibility to asthma and atopy among Chinese in Singapore--linkage to markers on chromosome 5q31-33

BACKGROUND: Asthma and atopy are complex genetic traits, influenced by the interaction of multiple genes and environmental factors. Linkage of these traits to chromosome 5q31-33 has been shown in other populations, but has not been well studied in the Chinese. We studied linkage between asthma and atopy with markers on chromosome 5q31-33 in the Singapore Chinese. This region contains many candidate genes, including the cytokine gene cluster. METHODS: We recruited 88 Chinese families with at least two affected offspring, totaling 373 subjects, with 125 and 119 sib-pairs for atopy and asthma, respectively. All individuals were genotyped with 19 polymorphic microsatellite markers spanning a distance of 41 cM along chromosome 5q31-33. Affected sib-pair and multipoint linkage analysis was performed. RESULTS: There was evidence for linkage of the asthma and atopy phenotypes with three markers, D5S2110, D5S2011, and D5S412 (P values of 0.001 to 0.00001). Multipoint analysis further substantiated this (nonparametric linkage scores of 1.8-2.9). These findings suggest that susceptibility genes for asthma and atopy are found in this region in the Chinese. CONCLUSION: This study has shown linkage of atopy and asthma to chromosome 5q31-33 in a heterogeneous Chinese population. These findings further substantiate the notion that chromosome 5q31-33 contains "universally" important susceptibility genes for these traits.     

Family patterns of asthma, atopy and airway hyperresponsiveness: an epidemiological study

BACKGROUND: The patterns of inheritance of asthma have largely been explored using data of symptom history collected by questionnaires which are subject to bias and which may therefore distort the measured relationship. OBJECTIVE: The purpose of this study was to examine family patterns of allergic disease using objective measurements of atopy and of airway hyperresponsiveness (AHR). METHODS: A large random sample of children aged 8-11 years was studied and 3 months later, their parents were also invited for study. Of the sample of 1655 children, both parents of 661 children were studied. In all subjects, respiratory illness history was measured by questionnaire, atopy by skin tests and AHR by responsiveness to histamine. RESULTS: The odds ratio for a child to have AHR if either parent had the same condition was approximately 2. 0, which was the same as the odds ratio for wheeze or diagnosed asthma in the presence of the same condition in either parent. The odds ratio for atopy was smaller (approximately 1.4, NS) but the risk of a nonatopic child having AHR if the parent had AHR was 3.0 (P = 0.01). The correlation between weal size in the child and parent was poor and the severity of AHR in the child was only modestly correlated with the severity of AHR in the parent (R = 0.51, P = 0.04). CONCLUSION: The use of objective measurements did not strengthen the association between atopic or asthmatic conditions in the parent and child, but did suggest that atopy and AHR are inherited independently.     

Effects of food allergens on asthma exacerbations in schoolchildren with atopic asthma

Although the prevalence with which food causes asthma is not well known, food allergy is implicated in a variety of respiratory symptoms. Eighty-two asthmatic children aged 6–16 years with doctor-diagnosed sensitization to inhalants and presenting with asthma exacerbation participated in this study of food allergies linked to asthma exacerbations. The diagnosis of food allergy was established using a questionnaire, clinical criteria, serum-specific IgE antibody measurements, and an atopy patch test. Asthma exacerbation was determined using fractional exhaled nitric oxide management after the children were admitted to the hospital. On the basis of questionnaire data, suspected food allergy was identified in 59.8% children. The positive and negative rates of serum food-specific IgE tests were 54.9% and 45.1%, respectively. The results of atopy patch tests in radioallergosorbent-positive participants were 88.9% positive and 12.5% negative. Food allergy is a risk factor for asthma exacerbation, and evaluation of food allergy in selected patients with asthma is indicated.