Genes for asthma? An analysis of the European Community Respiratory Health Survey

Prevalence, risk factors and underdiagnosis of asthma and wheezing in adults 40 years and older: A population-based study

OBJECTIVE

There are differences in the prevalence and risk factors of asthma around the world. The epidemiological situation of adults 40 years and older is not well established. Our aim was to determine the prevalence, underdiagnosis and risk factors of asthma and wheezing in adults in Colombia.

METHODS

A cross-sectional, population-based study including 5539 subjects from 40 to 93 years selected by a probabilistic sampling technique in five cities was conducted.

MEASUREMENTS

respiratory symptoms and risk factors questionnaire and spirometry.

DEFINITIONS

(a) Wheezing: Affirmative answer to the question "have you ever had two or more attacks of "wheezes" causing you to feel short of breath?" (b) Asthma: Wheezing definition and FEV1/FVC post-bronchodilator ≥ 70%. (c) Underdiagnosis: Asthma definition without a physician-diagnosis. Logistic regression was used for exploring risk factors.

RESULTS

Prevalence of asthma was 9.0% (95% CI: 8.3-9.8) and wheezing 11.9% (95% CI: 11.0-12.8). Asthma underdiagnosis was 69.9% and increased to 79.0% in subjects 64 years or older. The risk factors related to asthma and/or wheezing were: living in Bogota or Medellin, female gender, first degree relative with asthma, respiratory disease before 16 years of age, obesity, no education, indoor wood smoke exposure and occupational exposure to dust particles, gases or fumes.

CONCLUSION

We described the epidemiologic situation of asthma in adults 40 years and older in Colombia. In addition to some recognized risk factors, our data supports the association of indoor wood smoke and occupational exposures with asthma and wheezing. Underdiagnosis of asthma in adults was high, particularly in older subjects.

Genome-wide association studies of asthma in population-based cohorts confirm known and suggested loci and identify an additional association near HLA

RATIONALE

Asthma has substantial morbidity and mortality and a strong genetic component, but identification of genetic risk factors is limited by availability of suitable studies.

OBJECTIVES

To test if population-based cohorts with self-reported physician-diagnosed asthma and genome-wide association (GWA) data could be used to validate known associations with asthma and identify novel associations.

METHODS

The APCAT (Analysis in Population-based Cohorts of Asthma Traits) consortium consists of 1,716 individuals with asthma and 16,888 healthy controls from six European-descent population-based cohorts. We examined associations in APCAT of thirteen variants previously reported as genome-wide significant (P<5 x 10(-8)) and three variants reported as suggestive (P<5× 10(-7)). We also searched for novel associations in APCAT (Stage 1) and followed-up the most promising variants in 4,035 asthmatics and 11,251 healthy controls (Stage 2). Finally, we conducted the first genome-wide screen for interactions with smoking or hay fever.

MAIN RESULTS

We observed association in the same direction for all thirteen previously reported variants and nominally replicated ten of them. One variant that was previously suggestive, rs11071559 in RORA, now reaches genome-wide significance when combined with our data (P = 2.4 × 10(-9)). We also identified two genome-wide significant associations: rs13408661 near IL1RL1/IL18R1 (P(Stage1+Stage2) = 1.1x10(-9)), which is correlated with a variant recently shown to be associated with asthma (rs3771180), and rs9268516 in the HLA region (P(Stage1+Stage2) = 1.1x10(-8)), which appears to be independent of previously reported associations in this locus. Finally, we found no strong evidence for gene-environment interactions with smoking or hay fever status.

CONCLUSIONS

Population-based cohorts with simple asthma phenotypes represent a valuable and largely untapped resource for genetic studies of asthma.

A genome-wide meta-analysis of genetic variants associated with allergic rhinitis and grass sensitization and their interaction with birth order

BACKGROUND

Hay fever or seasonal allergic rhinitis (AR) is a chronic disorder associated with IgE sensitization to grass. The underlying genetic variants have not been studied comprehensively. There is overwhelming evidence that those who have older siblings have less AR, although the mechanism for this remains unclear.

OBJECTIVE

We sought to identify common genetic variant associations with prevalent AR and grass sensitization using existing genome-wide association study (GWAS) data and to determine whether genetic variants modify the protective effect of older siblings.

METHOD

Approximately 2.2 million genotyped or imputed single nucleotide polymorphisms were investigated in 4 large European adult cohorts for AR (3,933 self-reported cases vs 8,965 control subjects) and grass sensitization (2,315 cases vs 10,032 control subjects).

RESULTS

Three loci reached genome-wide significance for either phenotype. The HLA variant rs7775228, which cis-regulates HLA-DRB4, was strongly associated with grass sensitization and weakly with AR (P(grass) = 1.6 × 10(-9); P(AR) = 8.0 × 10(-3)). Variants in a locus near chromosome 11 open reading frame 30 (C11orf30) and leucine-rich repeat containing 32 (LRRC32), which was previously associated with atopic dermatitis and eczema, were also strongly associated with both phenotypes (rs2155219; P(grass) = 9.4 × 10(-9); P(AR) = 3.8 × 10(-8)). The third genome-wide significant variant was rs17513503 (P(grass) = 1.2 × 10(-8); PAR = 7.4 × 10(-7)) which was located near transmembrane protein 232 (TMEM232) and solute carrier family 25, member 46 (SLC25A46). Twelve further loci with suggestive associations were also identified. Using a candidate gene approach, where we considered variants within 164 genes previously thought to be important, we found variants in 3 further genes that may be of interest: thymic stromal lymphopoietin (TSLP), Toll-like receptor 6 (TLR6) and nucleotide-binding oligomerization domain containing 1 (NOD1/CARD4). We found no evidence for variants that modified the effect of birth order on either phenotype.

CONCLUSIONS

This relatively large meta-analysis of GWASs identified few loci associated with AR and grass sensitization. No birth order interaction was identified in the current analyses.

Risk factors for asthma onset between the ages of 12 and 40. Results of the FENASMA study

OBJECTIVES

To describe the clinical profile of patients with asthma and to identify possible risk factors for its development in subjects over the age of 12.

PATIENTS AND METHODS

A multicenter study of cases and controls. Recruited for inclusion were case subjects between the ages of 12 and 40 diagnosed with asthma, with an onset of symptoms after the age of 12. Control subjects were selected, with ages between 12 and 40, who did not have childhood asthma and did not present symptoms of asthma at the time of the study.

RESULTS

We evaluated 923 subjects: 247 cases and 671 controls. 54.9% were women. Mean age of the cases was 28.3 ± 8.2; mean age of controls was 30.8 ± 7.1 (p<0.001). In the logistic regression analysis, it was observed that the determining factors for the of the presence of asthma were hypersensitivity to animals or other allergens, presence of rhinitis, family history of asthma, occupational risk/exposure to irritants and the hypersensitivity/intolerance to NSAIDs. In said analysis, it was also demonstrated that age was a protection factor, as well as level of education.

CONCLUSIONS

The risk factors for the development of asthma at an adult age are hypersensitivity to animals or other allergens, rhinitis, family history of asthma, occupational risk/exposure to irritants and the hypersensitivity/intolerance to NSAIDs, while age and level of education are protection factors.

Major gene effect and additive familial pattern of inheritance of asthma exist among families of probands with sickle cell anemia and asthma

In the United States, sickle cell anemia (SCA) affects approximately 1 in 400 African-American newborns. Acute episodes of pain and acute chest syndrome (ACS) are the two leading causes of hospitalization. A relationship between the diagnosis of asthma and the incidence of pain and ACS has been established. We tested the hypothesis that a familial pattern of inheritance of asthma exists among first degree relatives of probands with SCA and asthma. Segregation analysis was performed in 104 families ascertained through affected probands. Of these, 19.7% (41/208) of the parents and 31.8% (28/88) of siblings of affected probands reported having been told by a doctor he or she had asthma at any age. Modes of inheritance were tested, using the Pedigree Analysis Package parameterized for the discrete trait of asthma affection status. A major effect was present and significant. Further tests were performed to determine whether transmission probabilities of the major effect followed Mendelian expectations. The additive mode of inheritance was the most parsimonious, while the residual heritability was found negligible. Our results support the hypothesis that a familial pattern of inheritance of asthma exists among first degree relatives of probands with SCA and asthma, suggesting that asthma is a co-morbid condition with SCA rather than a lung disease phenotype mimicking asthma.

Association of a lymphotoxin-alpha gene polymorphism and atopic asthma in Taiwanese children

BACKGROUND

The lymphotoxin-alpha (LT-alpha) gene is located on chromosome 6 (6p21.1-6p21.3) and it may regulate tumor necrosis factor (TNF) production. TNF is a potent cytokine in the airway inflammatory response. Polymorphisms of TNF-associated genes have been related to asthma. This study investigated an LT-alpha-Ncol polymorphism in the first intron of the LT-alpha gene (LT-alpha-Ncol*1 allele, as a variant type; and LT-alpha-Ncol*2 allele), which may predispose individuals to asthma and atopy.

METHODS

Polymerase chain reaction-based assays were performed to determine LT-alpha-Ncol genotypes among our subjects. A genetic case control analysis was then performed on 114 atopic asthmatic and 155 non-asthmatic unrelated children.

RESULTS

There was a statistically higher frequency of LT-alpha-Ncol*1 allele carriers (1/1+1/2) in the subjects with atopic asthma than in controls (OR=1.923; 95% CI = 1.061-3.484; p = 0.031).

CONCLUSION

The results indicate that LT-alpha-Ncol*1 may be a risk factor for atopic asthma in Taiwanese children.

Polymorphisms in the IL-4, IL-4 receptor alpha chain, TNF-alpha, and lymphotoxin-alpha genes and risk of asthma in Hong Kong Chinese adults

BACKGROUND

Susceptibility to the development of asthma and other atopic diseases is known to be associated with genetic components. However, association studies with interleukin-4 (IL-4), IL-4 receptor alpha subunit (IL-4R alpha), tumor necrosis factor-alpha (TNF-alpha) and lymphotoxin-alpha (LT-alpha) genes were inconclusive, as both positive and negative results were obtained in several populations studied. We aimed to investigate the association of the polymorphisms for IL-4 (C-589T), IL-4R alpha (Gln576Arg), TNF-alpha (G-308A) and LT-alpha (A252G) genes as candidates and asthma in adult Hong Kong Chinese population.

METHODS

The association study was conducted in an age- and smoking status-matched case-control design in asthma patients (n = 292) and healthy controls (n = 292) using polymerase chain reaction and restriction fragment length polymorphism.

RESULTS

No significant differences were found in allele and genotype frequencies of all four genes between patients and controls. After stratification by atopic status, the heterozygous AG genotype of LT-alpha (A252G) was found to increase risk of asthma in atopic population [odds ratio (OR) = 2.00, 95% CI 1.09-3.67, p = 0.024]. When stratified by smoking status, we found increased risk of asthma with subjects carrying the heterozygous AG and homozygous GG genotypes of LT-alpha in ever-smokers (OR = 2.73, 95% CI 1.11-6.69, p = 0.028 for heterozygotes; OR = 3.34, 95% CI 1.16-9.62, p = 0.026 for homozygotes).

CONCLUSION

Our results suggest that the variability of LT-alpha genotypes may have potential implications for individual susceptibility to asthma in atopic or in ever-smoking Chinese adults in Hong Kong.

Risk factors and characteristics associated with severe and difficult to treat asthma phenotype: an analysis of the ENFUMOSA group of patients based on the ECRHS questionnaire

BACKGROUND

Severe and difficult to treat asthma impairs health status and accounts for about half of asthma expenditure. In 1994, a European Network For Understanding Mechanisms of Severe Asthma (ENFUMOSA) was formed. A large group of patients from nine European countries has been selected.

OBJECTIVE

To examine the risk factors and symptoms associated with a phenotype of severe/difficult to treat asthma.

METHODS

The present report presents data assessed through the use of the European Community Respiratory Health Survey (ECRHS) Questionnaire in 148 mild-moderate controlled and 155 severe asthmatics from the ENFUMOSA group.

RESULTS

There is a negative association of severe asthma with reported allergy and with a family history of allergy (Odds ratio (OR)=0.45). Sharing a bedroom before the age of five is associated with a higher risk of severe asthma (OR=1.5) while childhood infections, play school attendance and exposure to allergens or animals are not. A larger proportion of severe asthma patients report symptoms at work (OR=2.7) or have to change jobs (OR=4.3) and fewer severe than mild patients are currently employed (OR=0.39). Smoking and exposure to smoke is similar in mild and severe asthma. Dietary habits do not differ between the groups, but severe asthmatics report eating less savoury snacks and there is a trend for lower intake of sweets.

CONCLUSIONS

Analysis of the ECRHS questionnaire in the ENFUMOSA study shows that severe asthma patients experience more symptoms and their health status is impaired by their inability to work and perhaps eat freely. Personal and maternal history of allergy is associated with mild but not severe asthma. Other than sharing a bedroom before the age of 5 years, no childhood exposure risk factors associated with severe asthma could be identified from this analysis.

Profiling of genes expressed in peripheral blood mononuclear cells predicts glucocorticoid sensitivity in asthma patients

Gene expression profiles were examined in freshly isolated peripheral blood mononuclear cells (PBMC) from two independent cohorts (training and test sets) of glucocorticoid (GC)-sensitive (n = 64) and GC-resistant (n = 42) asthma patients in search of genes that accurately predict responders and nonresponders to inhaled corticosteroids. A total of 11,812 genes were examined with high-density oligonucleotide microarrays in both resting PBMC (106 patients) and cells treated in vitro with IL-1beta and TNF-alpha combined (88 patients), with or without GC. A total of 5,011 genes were expressed at significant levels in the PBMC, and 1,334 of those were notably up-regulated or down-regulated by IL-1beta/TNF-alpha treatment. The expression changes of 923 genes were significantly reversed in GC responders in the presence of GC. The expression pattern of 15 of these 923 genes that most accurately separated GC responders (n = 26) from the nonresponders (n = 18) in the training set, based on the weighted voting algorithm, predicted the independent test set of equal size with 84% accuracy. The expression accuracy of these genes was confirmed by real-time-quantitative PCR, wherein 11 of the 15 genes predicted GC sensitivity at baseline with 84% accuracy, with one gene predicting at 81% in an independent cohort of 79 patients. We conclude that we have uncovered gene expression profiles in PBMC that predict clinical response to inhaled GC therapy with meaningful accuracy. Upon validation in an independent study, these results support the development of a diagnostic test to guide GC therapy in asthma patients.

Association of a haplotype block spanning SDAD1 gene and CXC chemokine genes with allergic rhinitis

BACKGROUND

Seasonal allergic rhinitis (SAR) is a common allergic disorder characterized by episodes of sneezing, rhinorrhea, and swelling of the nasal mucosa. Although the pathogenesis of SAR remains unclear, there does appear to be a genetic predisposition to development of SAR. We previously identified regions of chromosomes 1p, 4q, and 9q linked to SAR in 48 families (188 members) identified through children with SAR against orchard grass pollens.

OBJECTIVE

The aim of the current study was to identify susceptibility genes for SAR on 4q.

METHODS

We screened for markers associated with SAR on 4q with 17 microsatellite markers and then for mutations in 11 genes. We genotyped 44 single nucleotide polymorphisms (SNPs) in 48 SAR families and performed haplotype-based haplotype relative risk statistics implemented in the UNPHASED program. We also examined expression of genes with human multiple tissue and immune system cDNA panels.

RESULTS

We found that 1 microsatellite marker, D4S3042, was associated with SAR (P = .034). The haplotype-based haplotype relative risk approach revealed that SNPs in SDA1 domain containing 1; chemokine, CXC motif, ligand (CXCL)-9; CXCL10; and CXCL11 were associated with SAR (P = .001-.04). These SNPs made up a haplotype block, and the most common haplotype of this block was transmitted preferentially to affected offspring (P = .002).

CONCLUSION

Our results suggests that genetic variations in a haplotype block spanning the SDA1 domain containing 1 and CXC chemokine genes on 4q21 may contribute to development of SAR in the Japanese population.

Fetal sensitivity to testosterone, left-handedness and development of bronchial asthma: a new approach

In contrast to Geschwind, Behan and Galaburda (GBG) theory, there is strong evidence that inheritance through maternal line is responsible for the coexistence of asthma and left-handedness early in childhood. A new model that incorporates GBG's theory and maternal inheritance is proposed. This hypothesis suggests that maternal atopy is the most important factor in the evolution of asthma and that GBG's theory applies mainly in childhood. An inherited enhanced sensitivity of fetus to testosterone may be the underlying mechanism that leads to the development of bronchial asthma.

Therapeutic response to asthma medications: genotype predictors

Asthma is a major social and economic burden. Studies have shown that genetic polymorphisms can influence drug efficacy and/or toxicity. The understanding of the pharmacogenetics of asthma will allow therapeutic regimens to be tailored on an individual basis. It is hoped that linkage and association studies will define new therapeutic targets for asthma but until then, studies have focused on improving response to beta(2)-adrenoceptor agonist and leukotriene modifier therapy. Genetic polymorphism may account for interindividual differences in toxicity and efficacy of asthma medications. To date, single nucleotide polymorphism and limited haplotype analysis have provided inconclusive evidence as to how genotype predictors can be used to optimize current asthma therapies based on each patient's genetic profile.

Gene-gene synergistic effect on atopic asthma: tumour necrosis factor-alpha-308 and lymphotoxin-alpha-NcoI in Taiwan's children

BACKGROUND

Asthma is now known to be an inflammatory response caused by the release of inflammatory mediators and cytokines. Tumour necrosis factor (TNF) is a potent cytokine in the inflammation response of the airway, and the polymorphisms of TNF genes have been associated with asthma.

OBJECTIVE

This study investigated two variants, TNF-alpha-308*2 and lymphotoxin (LT)-alpha-NcoI*1, which may predispose individuals to asthma and atopy pathogenesis.

METHODS

PCR-based assays were performed to determine LT-alpha-NcoI*1 and TNF-alpha-308*2 genotypes among our subjects, with 128 atopic asthmatics and 51 non-atopic asthmatics, 55 atopic controls, and 78 non-atopic controls in this genetic case-control study.

RESULTS

The TNF-alpha-308*2 polymorphism increased in subjects with atopic asthma vs. non-atopic controls after adjusting for age distribution (adjusted odds ratios, AOR=2.73, 95% confidence interval, CI=1.16-6.64), but was not associated with non-atopic asthma (AOR=2.40, 95% CI=0.81-7.09). LT-alpha-NcoI*1 did not show an independent association with either atopic asthma or any one phenotype of specific IgE. The synergistic effect between these two genes was conducted, and the interaction between TNF-alpha-308*2 and LT-alpha-NcoI*1 polymorphisms was seen for atopic asthma (OR=2.59, 95% CI=1.10-6.10) when compared with all controls.

CONCLUSION

We have concluded that TNF-alpha-308 may be a risk factor for atopic asthma, whereas the LT-alpha-NcoI polymorphism may modify risk to atopic asthma with TNF-alpha-308.

Toll-like receptor 2 as a major gene for asthma in children of European farmers

BACKGROUND

The finding that the prevalence of asthma and allergies is less frequent in children raised on animal farms has led to the conjecture that exposure to microbial products modifies immune responses. The toll-like receptors (TLRs) represent an evolutionarily conserved family of innate immunity receptors with microbial molecules as ligands.

OBJECTIVES

We reasoned that polymorphisms in genes encoding TLRs might modulate the protective effects observed in farming populations.

METHODS

Farmers' and nonfarmers' children living in rural areas in Austria and Germany and who were enrolled in the cross-sectional ALEX study were genotyped for single nucleotide polymorphisms in the TLR2 and TLR4 genes. The frequencies of asthma, allergic rhinitis, and atopic sensitization were compared between the genotypes in relation to exposure to farming and endotoxin.

RESULTS

Among farmers' children, those carrying a T allele in TLR2/-16934 compared with children with genotype AA were significantly less likely to have a diagnosis of asthma (3% vs 13%, P = .012), current asthma symptoms (3% vs 16%, P = .004), atopic sensitization (14% vs 27%, P = .023), and current hay fever symptoms (3% vs 14%, P = .01). The association between TLR2/-16934 and asthma among children of farmers was independent of atopy. No such association was found among children from the same rural communities but not living on farms.

CONCLUSION

Our results suggest that genetic variation in TLR2 is a major determinant of the susceptibility to asthma and allergies in children of farmers.

Association of the interleukin-1 receptor antagonist gene with asthma

The interleukin-1 cluster on human chromosome 2q12-2q14 harbors various promising candidate genes for asthma and other inflammatory diseases. We conducted a systematic association study with single-nucleotide polymorphisms (SNPs) located in candidate genes situated in this cluster. Single-marker, two-locus and three-locus haplotype analysis of SNPs yielded several significant results (p < 0.05-0.0021) for the human IL1RN gene encoding the IL-1 receptor antagonist protein, an antiinflammatory cytokine that plays an important role in maintaining the balance between inflammatory and antiinflammatory cytokines. These findings were replicated and confirmed in an independent Italian family sample in which significant, although weaker, association with asthma was detected. A sequencing approach to the coding region of the human IL1RN gene revealed additional DNA variants, from which a selection was also associated with the disease in German and Italian samples. Calculation of the linkage disequilibrium for the human IL1RN gene showed strong linkage disequilibrium for nearly all analyzed SNPs. Further haplotype analysis indicated that six SNPs are sufficient for tagging all haplotypes with a prevalence of more than 1%. The most frequent haplotype constructed from these SNPs was 1.4-fold overtransmitted in the German family sample.

Allergen-induced airway disease is mouse strain dependent

We investigated the development of airway hyperreactivity (AHR) and inflammation in the lungs of nine genetically diverse inbred strains of mice [129/SvIm, A/J, BALB/cJ, BTBR+(T)/tf/tf, CAST/Ei, C3H/HeJ, C57BL/6J, DBA/2J, and FVB/NJ] after sensitization and challenge with ovalbumin (OVA). At 24, 48, and 72 h post-OVA exposure, the severity of AHR and eosinophilic inflammation of the mouse strains ranged from relatively unresponsive to responsive. The severity of the airway eosinophilia of some strains did not clearly correlate with the development of AHR. The temporal presence of T helper type 2 cytokines in lung lavage fluid also varied markedly among the strains. The levels of IL-4 and IL-13 were generally increased in the strains with the highest airway eosinophilia at 24 and 72 h postexposure, respectively; the levels of IL-5 were significantly increased in most of the strains with airway inflammation over the 72-h time period. The differences of physiological and biological responses among the inbred mouse strains after OVA sensitization and challenge support the hypothesis that genetic factors contribute, in part, to the development of allergen-induced airway disease.

Further support for the association of CCR5 allelic variants with asthma susceptibility

English and German nuclear families containing multiple asthmatic children and asthmatic parents were analysed to retest a recently reported association between resistance to asthma and the delta32 allele of chemokine receptor 5 (CCR5). Analysis of the families by the transmission-disequilibrium test (TDT) revealed a non-significant trend in the English families that provided marginal confirmation of the association (P < 0.125), but no similar trend was observed in the German families. Case-control comparison of delta32 allele and genotype frequencies in asthmatic vs. non-asthmatic parents revealed a significantly lower frequency of delta32 in asthmatic English parents (P < 0.009) and a similar but non-significant trend in German parents (P < 0.265). Taken together, the pattern of results provides confirmation for the previously observed delta32-asthma association and indicates that susceptibility to asthma may be influenced by CCR5 or another gene in chromosomal region 3p21.

A major susceptibility gene for asthma maps to chromosome 14q24

Asthma is a complex genetic disorder with a heterogeneous phenotype, largely attributed to the interactions among many genes and between these genes and the environment. Numerous loci and candidate genes have been reported to show linkage and association to asthma and atopy. Although some studies reporting these observations are compelling, no gene has been mapped that confers a sufficiently high risk of asthma to meet the stringent criteria for genomewide significance. Using 175 extended Icelandic families that included 596 patients with asthma, we performed a genomewide scan with 976 microsatellite markers. The families were identified by cross-matching a list of patients with asthma from the Department of Allergy/Pulmonary Medicine of the National University Hospital of Iceland with a genealogy database of the entire Icelandic nation. We detected linkage of asthma to chromosome 14q24, with an allele-sharing LOD score of 2.66. After we increased the marker density within the locus to an average of one microsatellite every 0.2 cM, the LOD score rose to 4.00. We designate this locus "asthma locus one" (AS1). Taken together, these results provide evidence of a novel susceptibility gene for asthma on chromosome 14q24.

Association of the ADAM33 gene with asthma and bronchial hyperresponsiveness

Asthma is a common respiratory disorder characterized by recurrent episodes of coughing, wheezing and breathlessness. Although environmental factors such as allergen exposure are risk factors in the development of asthma, both twin and family studies point to a strong genetic component. To date, linkage studies have identified more than a dozen genomic regions linked to asthma. In this study, we performed a genome-wide scan on 460 Caucasian families and identified a locus on chromosome 20p13 that was linked to asthma (log(10) of the likelihood ratio (LOD), 2.94) and bronchial hyperresponsiveness (LOD, 3.93). A survey of 135 polymorphisms in 23 genes identified the ADAM33 gene as being significantly associated with asthma using case-control, transmission disequilibrium and haplotype analyses (P = 0.04 0.000003). ADAM proteins are membrane-anchored metalloproteases with diverse functions, which include the shedding of cell-surface proteins such as cytokines and cytokine receptors. The identification and characterization of ADAM33, a putative asthma susceptibility gene identified by positional cloning in an outbred population, should provide insights into the pathogenesis and natural history of this common disease.

Two-trait-locus linkage analyses of asthma susceptibility

A genome-wide search was conducted to identify chromosomal regions likely to harbor genes for asthma susceptibility. One hundred and twelve Caucasian families ascertained through a proband with a diagnosis of asthma by the Collaborative Study on the Genetics of Asthma (CSGA) were used for this search. Genotype data on 323 polymorphic markers were analyzed via parametric and nonparametric linkage analysis in an initial genome scan to identify potential asthma susceptibility region(s). The regions where hold or nonparametric linkage scores were greater than 2.0 were selected for further investigation using two-trait-locus linkage analysis models.

Childhood asthma: new insights into management

Recently, a concerted effort has been made to reverse the trend of increasing asthma mortality and morbidity. One additional strategy might be to recognize patients at risk for persistent asthma and to intervene early. This review summarizes new information on asthma pathogenesis that has helped shape a new direction in managing childhood asthma. At the core is the recognition that asthma is a chronic inflammatory disease. Subsequently, inhaled steroids, the most potent anti-inflammatory asthma medications, have emerged as the cornerstone of the management of persistent asthma. The recent report of the National Heart, Lung, and Blood Institute's Childhood Asthma Management Program provides a comprehensive "profile of performance" for 3 treatment choices for the management of persistent asthma. This study answers questions regarding the benefits and shortcomings of the medications evaluated and prompts a closer evaluation of the long-term effects of other treatment strategies, including medications currently being developed. Although intervention with inhaled steroids offers new opportunities to control the development of asthma, one must be cognizant of potential risks in early and long-term therapeutic intervention. This review provides a perspective on our present knowledge, the rationale for early intervention, and opportunities for more aggressive therapy, as well as speculation on how ongoing clinical research will continue to play a role in advancing asthma care and moving toward a "cure" for this life-threatening disease.

Risk factor associations with wheezing patterns in children followed longitudinally from birth to 3(1/2) years

BACKGROUND

There is a paucity of detailed longitudinal data on wheeze in early childhood. Not all children who wheeze in early infancy will continue to wheeze into childhood and beyond. This study aims to investigate possible risk factors for different patterns of wheeze in the pre-school years.

SUBJECTS AND METHODS

Study participants were part of the Avon Longitudinal Study of Parents and Children (ALSPAC). Maternal reports of child wheeze between birth and 6 months and again between 30 and 42 months were gathered prospectively. Children were categorized into early wheeze, persistent wheeze or late onset wheeze. A large number of risk factors were assessed for each wheezing phenotype using multivariable logistic regression models.

RESULTS

Over 70% of children who wheezed in the first 6 months did not wheeze 3 years later. Wheezing between 0-6 months was independently associated with the presence of older siblings, male sex, delivery between April and December, bottle feeding, young maternal age, prenatal tobacco smoke exposure, atopy and parental history of asthma. From within this group of early wheezers, risk factors for wheeze that persisted beyond 6 months included pre-term delivery, young maternal age, living in rented local authority housing, atopy and a maternal (not paternal) history of asthma. Atopy and a family history of asthma emerged as the main predictors of wheeze that developed after 6 months of age.

CONCLUSION

It is clear that a number of wheezing syndromes exist by 3(1/2) years, albeit with some degree of overlap. Detailed follow-up of this cohort is underway to determine whether risk factor associations determined in the first 3(1/2) years have long-term significance for the clinical entity termed 'asthma'.

Segregation analyses of asthma and respiratory allergy: the Humboldt family study

We performed segregation analyses of asthma and respiratory allergy based on data from 309 nuclear families comprising 1,053 individuals living in the town of Humboldt, Saskatchewan, in 1993, using the REGD program of the S.A.G.E. program package. For adults, information on asthma and history of respiratory allergy was provided by the subjects themselves, and for children by their parents. When asthma was considered as the trait in segregation analysis, models of no major effect, with or without familial effects, were rejected, but they were not rejected after adjusting for history of respiratory allergy. The major gene hypothesis was not rejected before adjusting for history of respiratory allergy. When respiratory allergy was analyzed as the trait, both major gene and multifactorial models fitted the data well, regardless of whether there was adjustment for asthma or not. Other covariates adjusted for in the segregation analyses were age, sex, number of household smokers, current smoking, number of household members, generation, and house type. The data suggest that a major gene related to respiratory allergy may explain the familial aggregation of asthma.

The European Community Respiratory Health Survey: what are the main results so far? European Community Respiratory Health Survey II

The European Community Respiratory Health Survey (ECRHS) was the first study to assess the geographical variation in asthma and allergy in adults using the same instruments and definitions. The database of the ECRHS includes information from approximately 140,000 individuals from 22 countries. The aim of this review is to summarize the results of the ECRHS to date. The ECRHS has shown that there are large geographical differences in the prevalence of asthma, atopy and bronchial responsiveness, with high prevalence rates in English speaking countries and low prevalence rates in the Mediterranean region and Eastern Europe. Analyses of risk factors have highlighted the importance of occupational exposure for asthma in adulthood. The association between sensitization to individual allergens and bronchial responsiveness was strongest for indoor allergens (mite and cat). Analysis of treatment practices has confirmed that the treatment of asthma varies widely between countries and that asthma is often undertreated. In conclusion, the European Community Respiratory Health Survey has shown that the prevalence of asthma varies widely. The fact that the geographical pattern is consistent with the distribution of atopy and bronchial responsiveness supports the conclusion that the geographical variations in the prevalence of asthma are true and most likely due to environmental factors.

Allergy markers in respiratory epidemiology

Assessing allergy by measurement of serum immunoglobulin (Ig) E antibodies is fast and safe to perform. Serum antibodies can preferably be assessed in patients with dermatitis and in those who regularly use antihistamines and other pharmacological agents that reduce skin sensitivity. Skin tests represent the easiest tool to obtain quick and reliable information for the diagnosis of respiratory allergic diseases. It is the technique more widely used, specific and reasonably sensitive for most applications as a marker of atopy. Measurement of serum IgE antibodies and skin-prick testing may give complimentary information and can be applied in clinical and epidemiological settings. Peripheral blood eosinophilia is less used, but is important in clinical practice to demonstrate the allergic aetiology of disease, to monitor its clinical course and to address the choice of therapy. In epidemiology, hypereosinophilia seems to reflect an inflammatory reaction in the airways, which may be linked to obstructive airflow limitation.

Left-handedness and inheritance of bronchial asthma

A statistically significant difference in mean laterality quotients of 15 asthmatic and 106 nonasthmatic children showed a coexistence of left-handedness and asthma early in life. It is suggested that this phenomenon is not only a fetal event as the Geschwind-Galaburda hypothesis claims but it is mainly based on maternal line inheritance.

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.

Complex segregation analysis of families ascertained through Gilles de la Tourette syndrome

Although family and twin studies suggest that genetic factors are involved in the etiology of Tourette syndrome and other related tic disorders, further evidence is needed to demonstrate that the familial transmission is consistent with known genetic factors. We performed a complex segregation analysis that allowed for a variable age of onset of Gilles de la Tourette, other tic disorders and obsessive compulsive phenotype information on 108 extended families, each ascertained through one Tourette proband by using regressive models that are able to incorporate additional explanatory variables and major gene effects. A special version of the S.A.G.E. program, REGTLhunt, was used to explore the likelihood surface of all examined models. Results indicated that the pattern of Tourette and other related tic disorders in our data sample is not consistent with Mendelian inheritance even after modelling explanatory variables such as obsessive compulsive symptomatology.

Genetic variability in pulmonary physiological, cellular, and antibody responses to antigen in mice

Wide differences among inbred mouse strains in susceptibility to develop components of asthmalike pulmonary changes would provide insights into the nature of the relationships among those components and set the stage for genetic approaches to their etiology. We therefore examined pulmonary pathophysiological and serum immunoglobulin (Ig)E responses in mice of 12 inbred strains sensitized intraperitoneally with ovalbumin (OVA) and repeatedly exposed to aerosolized OVA. One day after the last OVA exposure the intravenous methacholine (MCh) dose required to reduce lung conductance by 50% (ED(50)GL) in OVA-sensitized and exposed mice was reduced by 0 to 2.7-fold, compared with sham-sensitized mice, depending on the strain. In OVA-sensitized mice, bronchoalveolar lavage (BAL) eosinophils comprised from 3.3 +/- 3.1 (SD) to 91.2 +/- 5.0% of BAL cells and eosinophilic pulmonary inflammation varied from being nondetectable to widespread and severe. OVA-specific IgE concentrations ranged from less than 3 ng/ml to 455 ng/ml in different strains. Shifts in responsiveness correlated significantly with pulmonary eosinophilia among strains (r > 0.70, p < 0.001) but not with antigen-specific IgE levels (r = 0.55, p = 0.056). These results demonstrate that allergen- induced enhancement of cholinergic responsiveness, pulmonary eosinophil influx, and elevations of serum antigen-specific IgE levels are each genetically determined and are not always associated.

Genes, factor X, and allergens: what causes allergic diseases?

Genetic disposition and allergen exposure play the main roles in the development of allergic diseases. Another factor that could be involved is the nutritional intake of vitamin D.

A genome-wide search for linkage to asthma. German Asthma Genetics Group

Asthma is among the most frequent chronic diseases in childhood. Although numerous environmental risk factors have already been identified, the basis for familial occurrence of asthma remains unclear. Previous genome screens for atopy in British/Australian families and for asthma in different American populations showed inconsistent results. We report a sib pair study of a sample of 97 families, including 415 persons and 156 sib pairs. Following an extensive clinical evaluation, all participants were genotyped for 351 polymorphic dinucleotide markers. Linkage analysis for asthma identified four chromosomal regions that could to be linked to asthma: chromosome 2 (at marker D2S2298, P = 0.007), chromosome 6 (around D6S291, lowest P = 0.008), chromosome 9 (proximal to D9S1784, P = 0.007), and chromosome 12 (D12S351, P = 0.010). These linkage regions could be reproduced for all loci by analysis of total or specific immunoglobulin E (minimum P values at these regions were 0. 003, 0.001, 0.010, and 0.015, respectively).

Prevalence of respiratory symptoms, bronchial hyperreactivity, and asthma in a megacity. Results of the European community respiratory health survey in Mumbai (Bombay)

To estimate adult asthma prevalence in the world's most rapidly growing mega-city, we applied epidemiologic surveillance tools, as a cooperating center of the European Community Respiratory Health Survey, to a randomly selected sample of Mumbai (Bombay) residents in 1992 through 1995. From a metropolitan population of over 10 million, we took a one-in-ten random sample from electoral rolls in a socially diverse residential district, and examined asthma symptoms in adults age 20 to 44 yr. In Phase I, we interviewed 2,313 adults about symptoms, asthma diagnosis, and medications in the previous 12 mo. In Phase II, family and smoking history, socioeconomic data, housing characteristics, serum IgE, allergy skin tests, spirometry, and methacholine challenge tests were obtained in a subset of 20% of those who had completed Phase I. House dust mite was the most common positive skin test (18% prevalence) and the only one of the nine applied that was significantly associated with asthma symptoms and physician-diagnosed asthma. Asthma prevalence was 3.5% by physician diagnosis, and 17% using a very broad definition including those with asymptomatic bronchial hyperreactivity. Asthma prevalence was strongly associated with positive house dust mite skin test, family history of asthma, and total IgE.