Title: Functional Genomics of the IL33/ST2 axis: a therapeutic target for asthma
Funder: Asthma UK

Abstract: Introduction: There is a need for new, more effective treatments for asthma particularly for refractory disease. Using Genome Wide Association (GWA) approaches we have now identified several asthma susceptibility genes with confidence providing novel insights into the underlying pathways in asthma that may be altered and amenable to therapeutic intervention. In particular, there has been overwhelming evidence that polymorphic variation within interleukin (IL)33 and its receptor ST2 genes increase the risk of developing asthma. Elevated IL33 production by airway epithelial cells is a feature of asthma and is thought to alter innate immune responses through ST2 dependent mechanisms, potentially contributing to asthma development and exacerbation. However, little is known regarding the effect of single nucleotide polymorphisms (SNPs) associated with asthma to the biology of the IL33/ST2 axis in these processes. Aims and Relevance: We propose to define 1) the contribution of key IL33/ST2 asthma risk SNPs to clinical measures underlying asthma to provide greater insight into the how these risk alleles influence asthma presentation in carriers and 2) the contribution of SNPs to altered protein expression, localization and epithelial function of IL33/ST2 in asthma patient cells and lung tissue of known genotype. This study has the potential to identify the IL33/ST2 molecular and cellular alterations in the asthmatic airway that, at least in part lead to increased risk of developing asthma. This will represent a significant level of new understandingthat will be fundamental in targeting these alterations for clinical benefit. Thestratification of asthma patients based on genetic profile where the IL33/ST2 axis may be particularly important will also be essential for Phase II trials of any approaches to target this pathway. Experimental Plan: To complete Aim 1 we will use SNP data (retrospective/prospective) and genetic association analyses in multiple asthma cohorts (n~4,500) to determine the contribution of SNPs to key features of asthma including; lung function, bronchial hyper-responsiveness and atopy. The outcomes of Aim 1 may be useful in informing patient selection in Aim 2, however we have excellent preliminary evidence that the IL33 SNP rs3939286 (5.7kb from IL33 transcription start site) tags the majority of SNPs associated with asthma and key ST2 asthma risk alleles are clustered in a small region (151bp) of the coding region of the ST2 TIR signalling domain forming a susceptibility haplotype that is potentially functional (rs10204137 (Glu501Arg), rs10192157 (Thr549Ile) and rs10206753 (Leu551Ser)). Bronchial epithelial cells (isolated via bronchoscopic brush technique) from asthma patients with known IL33/ST2 genotypes (10-15 primary cell lines/genotype and 10-15 controls) will be identified from several cell banks/isolated and cultured using air liquid interface (ALI) to determine the effect of these alleles on; i) IL33/ST2 expression andlocalisation, ii) IL33/ST2 function/signalling and iii) innate immune responses. Matched lung biopsies from these samples will also be interrogated for IL33/ST2 expression using immunohistochemistry. Finally, molecular mechanisms underlying these associations will be further defined using a range of molecular biology techniques including recombinant DNA approaches.


Research activity codes: 2.1 BIOLOGICAL AND ENDOGENOUS FACTORS
Health categories: RESPIRATORY