Soluble CD14 at 2 yr of age: gender-related effects of tobacco smoke exposure, recurrent infections and atopic diseases

Associations between biomarkers of environmental enteric dysfunction and oral rotavirus vaccine immunogenicity in rural Zimbabwean infants

BACKGROUND

Oral rotavirus vaccines (RVV) are poorly immunogenic in low-income countries. Environmental enteric dysfunction (EED) resulting from poor water, sanitation and hygiene (WASH) may contribute. We therefore tested associations between EED and RVV immunogenicity, and evaluated the effect of improved WASH on EED.

METHODS

We measured nine biomarkers of EED among Zimbabwean infants born to mothers enrolled in a cluster-randomised 2 × 2 factorial trial of improved WASH and improved feeding between November 2012 and March 2015 (NCT01824940). We used multivariable regression to determine associations between EED biomarkers and RVV seroconversion, seropositivity and geometric mean titer. Log-binomial regression was used to evaluate the effect of improved WASH on EED.

FINDINGS

Among 303 infants with EED biomarkers and immunogenicity data, plasma intestinal fatty-acid binding protein and stool myeloperoxidase were positively associated with RVV seroconversion; adjusted RR 1.63 (95%CI 1.04, 2.57) and 1.29 (95%CI 1.01, 1.65), respectively. There were no other associations between RVV immunogenicity and either individual biomarkers or EED domains (intestinal permeability, intestinal damage, intestinal inflammation and microbial translocation). EED biomarkers did not differ between randomised WASH and non-WASH groups.

INTERPRETATION

We found no evidence that EED was associated with poor RVV immunogenicity. Contrary to our hypothesis, there was weak evidence that EED was associated with increased seroconversion. EED biomarkers were not affected by a package of household-level WASH interventions.

Cord Blood Soluble CD14 Predicts Wheeze and Prolonged Cough in Young Children: The PATCH Study

BACKGROUND

Soluble cluster of differentiation 14 (sCD14) plays a role in the development and manifestation of atopic symptoms, although the results of previous studies have been inconclusive. The aim of this study is to evaluate the practical use of sCD14 as a predictive biomarker of allergy in young children.

METHODS

Children aged 0-1 year from a birth cohort in the Prediction of Allergies in Taiwanese Children (PATCH) study were enrolled. Cord blood sCD14 concentrations were measured. Pediatrician evaluation and questionnaire interviews were performed periodically until 1 year of age to determine the children's allergic and respiratory symptoms.

RESULTS

Two hundred and six 1-year-old subjects were enrolled. Wheeze was positively associated with cord blood sCD14, a family member with asthma and parental smoking. Prolonged cough was associated with cord blood sCD14, older maternal age and more siblings. In the multivariate logistic regression analysis, cord blood sCD14 was the only independent predictive biomarker for wheeze and prolonged cough by 1 year of age. Every 100-ng/ml increase in cord blood sCD14 resulted in a 1.56-fold higher risk of developing wheeze and a 1.62-fold higher risk of prolonged cough in children by 1 year of age.

CONCLUSIONS

Cord blood sCD14 may be a useful biomarker for predicting infant wheeze and prolonged cough by 1 year of age.

Childhood lung function and the association with β2-adrenergic receptor haplotypes

AIM

To determine associations between ADRB2 polymorphisms and lung function through childhood, and possible modification by gender, pet keeping or tobacco smoke.

METHODS

Four ADRB2 single nucleotide polymorphisms (rs1042711, rs1042713, rs1042714 and rs1800888) were genotyped in 953 children from the prospective birth cohort 'Environment and Childhood Asthma' study and analysed for association with flow-volume parameters at birth (tidal breathing) and at 10 years of age (maximally forced), stratified by environmental exposures.

RESULTS

The risk of reduced lung function was reduced in 10-year-old children carrying the most common ADRB2 haplotype (CGGC) (OR 0.45 (95% CI 0.25, 0.82)), whereas there was no association between lung function at birth and ADRB2 haplotypes. Tobacco smoke exposure, gender and pet keeping did not significantly interact with the haplotypes in influencing lung function.

CONCLUSION

This study demonstrates a possible protective effect by the ADRB2 haplotype I (CGGC) on reduced FEV1 in 10-year-old children, whereas no ADRB2 geno-/haplotypes were significantly associated with neonatal lung function. The ADRB2 gene thus appears to contribute to lung function development in childhood, independently of smoking, pets and gender.

The impact of pre- and postnatal exposures on allergy related diseases in childhood: a controlled multicentre intervention study in primary health care

BACKGROUND

Environmental factors such as tobacco exposure, indoor climate and diet are known to be involved in the development of allergy related diseases. The aim was to determine the impact of altered exposure to these factors during pregnancy and infancy on the incidence of allergy related diseases at 2 years of age.

METHODS

Children from a non-selected population of mothers were recruited to a controlled, multicenter intervention study in primary health care. The interventions were an increased maternal and infant intake of n-3 PUFAs and oily fish, reduced parental smoking, and reduced indoor dampness during pregnancy and the children's first 2 years of life. Questionnaires on baseline data and exposures, and health were collected at 2 years of age.

RESULTS

The prevalence of smoking amongst the mothers and fathers was approximately halved at 2 years of age in the intervention cohort compared to the control cohort. The intake of n-3 PUFA supplement and oily fish among the children in the intervention cohort was increased. There was no significant change for indoor dampness. The odds ratio for the incidence of asthma was 0.72 (95% CI, 0.55-0.93; NNTb 53), and 0.75 for the use of asthma medication (95% CI, 0.58-0.96). The odds ratio for asthma among girls was 0.41 (95% CI 0.24-0.70; NNTb 32), and for boys 0.93 (95% CI 0.68-1.26). There were no significant change for wheeze and atopic dermatitis.

CONCLUSION

Reduced tobacco exposure and increased intake of oily fish during pregnancy and early childhood may be effective in reducing the incidence of asthma at 2 years of age. The differential impact in boys and girls indicates that the pathophysiology of asthma may depend on the sex of the children.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN28090297.

Allergic predisposition modifies the effects of pet exposure on respiratory disease in boys and girls: the seven northeast cities of China (SNECC) study

BACKGROUND

The relationship between pet exposure and the respiratory disease in childhood has been a controversial topic, much is still unknown about the nature of the associations between pet exposure and children's respiratory health stratified by gender and allergic predisposition. The objective of the present study was to assess the relationship between pet exposure and respiratory symptoms in Chinese children, and to investigate the modified effects of gender and allergic predisposition on such relationship.

METHODS

31,049 children were selected from 25 districts of 7 cities in Northeast China in 2009. Information on respiratory health and exposure to home environmental factors was obtained via a standard questionnaire designed by the American Thoracic Society.

RESULTS

Children with an allergic predisposition were found to have more frequent exposure to pets than those without an allergic predisposition (18.5% vs. 15.4%). In children without an allergic predisposition, pet exposure was associated with increased susceptibility to respiratory symptoms/diseases, with girls being more susceptible than boys. No association was found between pet exposure and respiratory symptoms/diseases in boys with an allergic predisposition. In girls with an allergic predisposition, association was found between doctor-diagnosed asthma and pet exposure of their mother during pregnancy (adjusted odds ratio (ORs)=2.03; 95% confidence interval (CI): 1.01-4.33), and their current pet exposure (ORs=1.37; 95%CI: 1.00-1.88).

CONCLUSIONS

Pet exposure in children without an allergic predisposition was associated with increased susceptibility to respiratory disease, with girls being more susceptible than boys.

A growing role for gender analysis in air pollution epidemiology

Epidemiologic studies of air pollution effects on respiratory health report significant modification by sex, although results are not uniform. Importantly, it remains unclear whether modifications are attributable to socially derived gendered exposures, to sex-linked physiological differences, or to some interplay thereof. Gender analysis, which aims to disaggregate social from biological differences between males and females, may help to elucidate these possible sources of effect modification. Studies of children suggest stronger effects among boys in early life and among girls in later childhood. The qualitative review describes possible sources of difference in air pollution response between women and men, which may vary by life stage, coexposures, hormonal status, or other factors. The sources of observed effect modifications remain unclear, although gender analytic approaches may help to disentangle gender and sex differences in pollution response. A framework for incorporating gender analysis into environmental epidemiology is offered, along with several potentially useful methods from gender analysis.

Reduced basal salivary cortisol in children with asthma and allergic rhinitis

AIM

Reduced basal cortisol is reported in allergic disease. We investigated if basal salivary cortisol levels were reduced in children with asthma or allergic rhinitis, controlling for inhaled corticosteroids (ICS) use.

METHODS

Morning and evening saliva of asthmatic children aged 7-12 years (n = 50) and that of controls (n = 52) were sampled. A total of 19 asthmatics and four controls had allergic rhinitis. Healthy children were controls without rhinitis. Of all, 14 asthmatic children used low, and 12 used moderate or high doses of ICS. Cortisol was analysed by radioimmunoassay.

RESULTS

Morning salivary cortisol median (95% CI) was lower in asthmatics (8.7 (7.1, 9.7)) compared with that in controls (10.4 (9.6, 11.8); p = 0.006), which was similar for evening cortisol levels. Regression analyses demonstrated that asthmatics using moderate or high doses of ICS had reduced morning salivary cortisol adjusted (for age and gender) odds ratio (aOR) (95% CI) (0.54 (0.37, 0.80); p = 0.002) and reduced evening cortisol aOR (0.09 (0.01, 0.6); p = 0.02) compared with that in healthy children. Asthmatics with rhinitis on no or low doses of ICS had reduced morning cortisol aOR (0.73 (0.56, 0.96); p = 0.02) compared with that in healthy children.

CONCLUSION

Asthmatic children on moderate or high doses of inhaled corticosteroids had reduced salivary cortisol, but co-morbidity of asthma and rhinitis was also associated with reduced cortisol levels.

Renal CD14 expression correlates with the progression of cystic kidney disease

Monocyte and macrophage markers are among the most highly overexpressed genes in cpk mouse kidneys with severely progressive renal cystic disease. We show here that one of these markers, CD14, is abnormally transcribed, activated and shed in cystic kidneys. However, these abnormalities were not associated with an increased number of interstitial CD14-positive mononuclear cells. Instead, we found that most non-cystic and cystic renal tubular epithelia were CD14-positive; even distal nephron-derived principal cells. Cd14 was significantly overexpressed in the kidneys of 5-day-old cpk mice and further increased as the disease progressed. In the cpk model with variable rates of cystic kidney enlargement (due to an intercross of two distinct genetic backgrounds), Cd14 expression positively correlated with kidney volume, exceeding the correlation with MCP-1, an established marker of autosomal-dominant polycystic kidney disease (ADPKD). In 16 patients with ADPKD, the baseline urinary CD14 level showed some tendency to correlate with the 2-year change in total kidney volume; however, the tendency was not statistically significant. But the association was significant when the analysis was confined to males. Clearly more studies need to be done to evaluate the utility of CD14 as a marker for outcomes in ADPKD.

CD14 polymorphisms and serum CD14 levels through childhood: a role for gene methylation?

BACKGROUND

CD14 is a pattern-recognition receptor for environmental LPS, and engagement of the CD14-LPS complex activates innate host defense mechanisms. Single nucleotide polymorphisms (SNPs) in the CD14 gene have been associated with soluble CD14 (sCD14) levels, but inconsistencies between studies suggest the presence of regulatory mechanisms hitherto not well understood.

OBJECTIVE

We sought to investigate possible associations between CD14 SNPs and sCD14 levels at different time points in childhood (at birth [cord blood] and 2 and 10 years) and to explore whether these associations were related to CD14 gene methylation.

METHODS

Four SNPs, rs2569191 (-1145GA), rs5744455 (-550CT or -651CT), rs2569190 (-159CT or -260CT), and rs4914 in CD14 were genotyped in 762 children from the Environmental and Childhood Asthma study. Genotype frequencies were analyzed for association with sCD14 levels in 660 babies, 346 children at age 2 years, and 360 children at age 10 years. In a subgroup of 157 children with DNA available at both 2 and 10 years of age, CD14 methylation patterns were determined and analyzed against detected CD14 gene-sCD14 associations.

RESULTS

rs2569191, rs5744455, and rs2569190 were associated with sCD14 levels at birth and 2 years, but only rs5744455 was associated with sCD14 levels at 10 years. CD14 methylation increased significantly from age 2 to 10 years, and the level of methylation was inversely correlated with sCD14 levels at 10 years.

CONCLUSION

The reduced effect of CD14 polymorphisms on sCD14 levels from early to late childhood paralleled a small but significant increase in CD14 methylation during the same period.

A growing role for gender analysis in air pollution epidemiology

OBJECTIVE

Epidemiologic studies of air pollution effects on respiratory health report significant modification by sex, although results are not uniform. Importantly, it remains unclear whether modifications are attributable to socially derived gendered exposures, to sex-linked physiological differences, or to some interplay thereof. Gender analysis, which aims to disaggregate social from biological differences between males and females, may help to elucidate these possible sources of effect modification.

DATA SOURCES AND DATA EXTRACTION

A PubMed literature search was performed in July 2009, using the terms "respiratory" and any of "sex" or "gender" or "men and women" or "boys and girls" and either "PM2.5" (particulate matter <or= 2.5 microm in aerodynamic diameter) or "NO2" (nitrogen dioxide). I reviewed the identified studies, and others cited therein, to summarize current evidence of effect modification, with attention to authors' interpretation of observed differences. Owing to broad differences in exposure mixes, outcomes, and analytic techniques, with few studies examining any given combination thereof, meta-analysis was not deemed appropriate at this time.

DATA SYNTHESIS

More studies of adults report stronger effects among women, particularly for older persons or where using residential exposure assessment. Studies of children suggest stronger effects among boys in early life and among girls in later childhood.

CONCLUSIONS

The qualitative review describes possible sources of difference in air pollution response between women and men, which may vary by life stage, coexposures, hormonal status, or other factors. The sources of observed effect modifications remain unclear, although gender analytic approaches may help to disentangle gender and sex differences in pollution response. A framework for incorporating gender analysis into environmental epidemiology is offered, along with several potentially useful methods from gender analysis.

Personalized medicine: a pediatric perspective

The aim of pediatric personalized medicine is to uniquely combine genetic variation with developmental stage and environmental exposure to provide a tailored preventive, diagnostic, and therapeutic regimen. Recent advances in genomic research have identified many genetic variants that may be related to allergic and inflammatory disease and therapeutic response. These include variants involved in immune response, barrier proteins, and medication response. Current evidence also suggests that the effect of genetic variation often depends on the developmental stage of a child and environmental exposure such as infection or tobacco smoke during a specific stage. Personalized medicine is a new and exciting field with the potential to significantly improve medical care for children and adults.

Soluble immune receptor serum levels are associated with age, but not with clinical phenotype or disease severity in childhood atopic dermatitis

BACKGROUND

Soluble immune receptors (SIRs) have been proposed as biomarkers in patients with atopic dermatitis (AD). However, their clinical applicability in affected children has rarely been studied.

OBJECTIVE

To assess the diagnostic usefulness of serum SIRs in childhood AD by correlating the obtained receptor profiles with serological parameters and clinical features such as age, AD phenotype and disease severity.

METHODS

We investigated 100 children with AD. The sCD14, sCD23, sCD25, sCD30, total IgE (tIgE) and eosinophilic cationic protein (ECP) were determined using sera of all children. The clinical phenotype was classified as extrinsic AD (ADe) or intrinsic AD (ADi) by the presence of allergen-specific IgE antibodies.

RESULTS

A total of 55 male and 45 female children were recruited. The sCD23, sCD25 and sCD30 serum levels revealed significant age-dependency. At a mean SCORAD of 40 (range 8-98), none of the evaluated SIRs was correlated to disease severity. In all, 73% of patients suffered from ADe while 27% showed the ADi phenotype. None of the analysed SIRs differed significantly between ADe and ADi patients, while tIgE and ECP levels were elevated in the ADe subgroup.

CONCLUSION

The current study provides evidence that sCD23, sCD25 and sCD30 serum levels are highly age-dependent. Serum concentrations of all investigated SIRs did not significantly correlate with disease severity in children with AD and were not differentially expressed in patients of different AD phenotypes. Therefore, we believe that the studied SIRs cannot be regarded as clinically useful biomarkers for the assessment of childhood AD.

Influence of C-159T SNP of the CD14 gene promoter on lung function in smokers

CD14, a co-receptor for endotoxin, plays a significant role in regulating the inflammatory response to this agent. The C-159T single nucleotide polymorphism (SNP) in the CD14 gene promoter is an important regulator of CD14 expression, with TT homozygotes having increased expression of CD14. This SNP has been linked to pathogenesis of asthma and with cardiovascular diseases in smokers. We hypothesize that CD14 also plays a role in the pathophysiology of COPD in smokers who are exposed to endotoxin contained in cigarette smoke as well as endotoxin derived from Gram-negative microbes colonizing their airways. To assess the effect of the C-159T SNP of the CD14 gene promoter on lung function, we recruited 246 smokers 40 years of age or older with a range of 10-156 pack-year smoking exposures. The TT genotype was associated with lower lung function in smokers with a moderate smoking history. However, the CC genotype was associated with decreased lung function in heavy smokers (>56 pack years). The effect of CC genotype on severity of COPD is analogous with the effect of this genotype in risk for asthma. CD14 may be a factor in the pathophysiology of COPD, as it is in asthma and smoking-related cardiovascular diseases.

An interdisciplinary analysis of sex and gender in relation to the pathogenesis of bronchial asthma

BACKGROUND

An increasing number of studies confirm that pathogenesis and prevalence of bronchial asthma are age and sex dependent. Detailed physiological mechanisms of the changing sex ratios with age are not fully known, however, the gender (socio-cultural) factors are also imperative. Although multiple factors definitely influence the pathogenesis of asthma, only individual or few combinations of these have been investigated.

METHODS

The terms 'sex', 'gender' and plausible combinations of both were systematically researched in selected databases (Medline, Scopus) or other sources, including publications from January 2000 to June 2007. Generated articles were categorized, either as endogenous or exogenous factors influencing the pathogenesis of asthma, and divided into the following subgroups: genetic, immunological, hormonal, gynaecological, nutritional, and environmental parameters.

RESULTS

An increasing number of studies investigate the influence of sex and gender in the aetiology, therapy and prevention of asthma. While their results are still debatable, others regarding its initiation, perpetuation and cessation have been clarified. Recent insights into interactions at biomolecular and immunological levels greatly contribute to clarifying sex-specific influences. Despite occasional oversimplifications, a trend for explanations considering the complex interplay of different factors can be observed. This work is in line with this trend and offers explanation models from our point of view.

CONCLUSIONS

Some disagreements regarding the patho-physiology, diagnosis, treatment and prevention of asthma still prevail. Nevertheless, in order to better appreciate its complexity, openness to and persistent consideration for interdisciplinary as well as sex- and gender-related factors is required of the medical-research community in future investigations.

Helicobacter pylori infection and allergic diseases: epidemiological study in Japanese university students

BACKGROUND AND AIM

A negative association between Helicobacter pylori infection and allergic diseases has not been consistent. The aim of this study was to examine the association between allergic diseases and H. pylori infection in Japan.

METHODS

Newly enrolled university students completed health survey questionnaires regarding general health and the presence of allergic diseases. Helicobacter pylori status was determined by the presence of serum H. pylori IgG and the presence of allergic manifestations was confirmed by interview.

RESULTS

A total of 1953 students had a routine health survey; H. pylori status was determined in 777 including 369 with allergic diseases and 408 controls. The reported frequency of allergic rhinoconjunctivitis, atopic dermatitis, urticaria, bronchial asthma and mixed diseases was 29.0%, 11.1%, 2.0%, 0.9% and 5.0%, respectively. Helicobacter pylori infection was diagnosed less frequently in the allergic group compared with controls (11.4% vs 17.6%, P = 0.015). Helicobacter pylori infection was less frequent in men with allergic diseases (OR 0.49, 95% CI 0.27-0.89).

CONCLUSION

Allergic diseases are frequent in young Japanese adults and are negatively associated with H. pylori infection especially in men.

Asthma genetics: personalizing medicine

Asthma is a chronic inflammatory lung disease that leads to significant morbidity, mortality, and economic burden. The clinical symptoms, which are a result of airway inflammation and reversible airway obstruction, have led to the mainstay of therapies for asthma: anti-inflammatory medications and bronchodilators. However, the efficacies of the various classes of medications are not equal among all patients and may be affected by asthma phenotypes, environmental exposures, and genetic differences. Similarly, the risk for developing asthma and the natural history of the disease show great inter-individual variability due to these same factors. Over the past few decades, much effort has been focused on the genetics of asthma, and investigators have identified more than one hundred potential asthma susceptibility genes, of which at least ten have been replicated in numerous independent studies. In parallel, researchers have also identified genetic factors that impact the pharmacotherapeutic responses to the major classes of asthma medications. While the results of previous studies have been promising, future investigations need to combine genetics, pharmacogenetics, accurate disease phenotyping, and environmental exposures to build the foundation for personalized and predictive medicine for the 21st century. The ultimate goal is to enable physicians to identify those at risk for asthma, intervene to prevent or attenuate the disease, and select the optimal medical regimen for each individual patient. If successful, the resulting paradigm shift in medical practice will lead to improved clinical outcomes and decreased health care expenditures.

Respiratory effects of tobacco smoking on infants and young children

Second-hand smoke (SHS) and tobacco smoke products (TSPs) are recognised global risks for human health. The present article reviews the causal role of SHS and TSPs for respiratory disorders in infants and young children. Several studies have shown an effect of TSPs exposure during pregnancy upon lung function in the newborn infant and of SHS on symptoms and lung function after birth. From 1997 to 1999 a set of systematic reviews concerning the relationship between second-hand exposure to tobacco smoke and respiratory health in children was published in Thorax by Cook and Strachan, covering hundreds of published papers. The evidence for a causal relationship between SHS exposure and asthmatic symptoms and reduced lung function is quite strong, whereas the evidence related to the development of allergy is much weaker. There is recent evidence relating to an interaction between TSP exposure and genetic ploymorphisms, demonstrating that certain individuals are more susceptible to the effect of TSP exposure on lung health. In the present review, an overview is given for the effects of TSP exposure and SHS upon lung health in children, with a focus on infants and young children. There is a need for intervention to reduce TSP exposure in young children, by educating parents and adolescents about the health effects of TSP exposure. Recent legislation in many European countries related to smoking in the workplace is of great importance for exposure during pregnancy. Studies are needed to identify possible critical periods for TSPs to induce harmful effects upon lung health in young children and on environment-gene interactions in order to prevent harm.

Soluble CD14: role in atopic disease and recurrent infections, including otitis media

Soluble CD14 (sCD14) is a part of innate immunity that has been implicated in many diseases, including allergic diseases. However, many influencing factors and confounders, including gender-gene-environment interactions, may complicate interpretations of the observed associations to allergic diseases. In this paper, we review current literature describing the functions of sCD14 and its associations with common (recurrent) infections and with allergic diseases. Because sCD14 is involved with immunologic responses to infections, and exposure to microbial compounds is debated as a protective or a trigger factor for allergy development, these factors-which include genotypes, gender, age, microbial agents (from the environment and infection), and tobacco smoke-cannot be assessed independently. We conclude that confounding effects are important and must be considered to understand the role of sCD14 in allergic development.

Rhinosinusitis: prevention strategies

Risk factors of recurrent sinusitis involve upper respiratory infections, bacterial load of the adenoids, day care attendance and exposure to tobacco smoke as well as sinonasal abnormalities, including septal deviation, choanal atresia, polyps and hypoplasia of sinuses. Furthermore, several systemic disorders can facilitate the development of chronic sinusitis, such as allergic rhinitis, gastro-esophageal reflux disease (GER), cystic fibrosis, primary ciliary dyskinesia, and immunodeficiency diseases. A clinical practice guideline for the management of sinusitis is available only for the acute disease, but does not include for the management of the chronic form (i.e. chronic/recurrent sinusitis) and even less for the prevention strategies. As several studies indicate that the majority of children respond to sequential medical followed by surgical interventions, when needed, the best prevention of recurrence or chronicity is to properly treat acute sinusitis; in addition, children should be removed from larger and crowded day care whenever possible and should not be exposed to cigarette smoke. If allergic rhinitis co-exists, it can be managed with nasal steroids sprays and anti-histamines, although the long-term results are controversial. In case of chronic sinusitis, the strategy of prevention is to assess and to cure the associated conditions.

Severe asthma in adults: what are the important questions?

The term severe refractory asthma (SRA) in adults applies to patients who remain difficult to control despite extensive re-evaluation of diagnosis and management following an observational period of at least 6 months by a specialist. Factors that influence asthma control should be recognized and adequately addressed prior to confirming the diagnosis of SRA. This report presents statements according to the literature defining SRA in order address the important questions. Phenotyping SRA will improve our understanding of mechanisms, natural history, and prognosis. Female gender, obesity, and smoking are associated with SRA. Atopy is less frequent in SRA, but occupational sensitizers are common inducers of new-onset SRA. Viruses contribute to severe exacerbations and can persist in the airways for long periods. Inflammatory cells are in the airways of the majority of patients with SRA and persist despite steroid therapy. The T(H)2 immune process alone is inadequate to explain SRA. Reduced responsiveness to corticosteroids is common, and epithelial cell and smooth muscle abnormalities are found, contributing to airway narrowing. Large and small airway wall thickening is observed, but parenchymal abnormalities may influence airway limitation. Inhaled corticosteroids and bronchodilators are the mainstay of treatment, but patients with SRA remain uncontrolled, indicating a need for new therapies.

Gene-environmental interaction in asthma

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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