Abstract
Background
Food allergies pose a considerable worldwide public health burden with incidence as high as one in ten in 12-month old infants. Few food allergy genetic risk variants have yet been identified. The Th2 immune gene IL13 is a highly plausible genetic candidate as it is central to the initiation of IgE-class switching in B cells.
Objective
Here we sought to investigate whether genetic polymorphisms at IL13 are associated with the development of challenge-proven IgE-mediated food allergy.
Method
We genotyped nine IL13 'tag' single nucleotide polymorphisms (tag-SNPs) in 367 challenge-proven food allergic cases, 199 food sensitised-tolerant cases and 156 non-food allergic controls from the HealthNuts study. 12-month old infants were phenotyped using open oral food challenges. SNPs were tested using Cochran-Mantel-Haenszel test adjusted for ancestry strata. A replication study was conducted in an independent, co-located sample of four paediatric cohorts consisting of 203 food allergic cases and 330 non-food allergic controls. Replication sample phenotypes were defined by clinical history of reactivity, 95% PPV or challenge and IL13 genotyping was performed.
Results
IL13 rs1295686 was associated with challenge-proven food allergy in the discovery sample (P=0.003; OR=1.75; CI=1.20-2.53). This association was also detected in the replication sample (P=0.03, OR=1.37, CI=1.03-1.82) and further supported by a meta-analysis (P=0.0006, OR=1.50). However, we cannot rule out an association with food sensitisation. Carriage of the rs1295686 variant A allele was also associated with elevated total plasma IgE.
Conclusions
We show for the first time, in two independent cohorts, that IL13 polymorphism rs1295686 (in complete linkage disequilibrium with functional variant rs20541) is associated with challenge-proven food allergy.
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