Association between farm exposure and atopy, according to the CD14 C-159T polymorphism

BackgroundA higher exposure to bacterial compounds is purported to explain the lower prevalence of allergy in farm children, but responsiveness to bacterial compounds is modulated by genetic factors.ObjectiveTo assess whether the protective effect of farm exposure on atopy is influenced by a CD14 promoter functional polymorphism.MethodsWe administered a detailed questionnaire on farm exposure in childhood and genotyped the CD14 C-159T polymorphism in 2 French centers participating in the European Community Respiratory Health Survey (ECRHS)–II.ResultsSix hundred randomly selected young adults provided blood samples for IgE measurements and had CD14 C-159T genotyped. Exposure to a farming environment in early life was associated with a reduced risk of nasal allergies (odds ratio [OR], 0.54; 95% CI, 0.29-1.00) and atopic sensitization (OR, 0.47; 95% CI, 0.24-0.93) in adulthood. A lower risk of allergic rhinitis and atopy was also observed in carriers of the CD14-159TT genotype compared with −159CC subjects (OR, 0.52; 95% CI, 0.30-0.88; and OR, 0.54; 95% CI, 0.31-0.92, respectively). When farm exposure and CD14 C-159T were considered together, the risk of nasal allergies and atopy was the most reduced in the subjects who combined both an early-life exposure to a farming environment and the −159TT genotype (OR, 0.26; 95% CI, 0.07-0.94; and OR, 0.21; 95% CI, 0.05-0.93, respectively, vs nonexposed −159CC+CT subjects). The results were consistent in the 2 centers, supporting the validity of the results.ConclusionA gene-by-environment interaction between CD14 C-159T and environmental exposure in childhood may modify the development of atopy.Clinical implicationsThis polymorphism should be considered in interventions studies that use microbial stimuli to reduce sensitization.