A Belgian research group, including Lies Peeters, M. Schroyen, A. Coussé, A. Somville, K. Dekeyser, and N. Buys of the University of Louvain (KUL) conducted an expression study for the sensitivity for insect bite hypersensitivity in Belgian Warmblood horses.
Insect bite hypersensitivity (IBH) represents a type I and type IV hypersensitivity to presumably salivary antigens from numerous Culicoides species and possibly other insects. The prevalence of IBH in Belgian Warmblood Horses (BWH) is 9.4% in Belgium so IBH is a serious problem in BWH. Until now, there is no curative treatment but there are clear indications that the susceptibility for IBH is heritable.
The identification of genes that influence the sensitivity for IBH can lead to the development of a marker assisted selection method. Based on literature, two candidate genes were selected: interleukine-4-receptor (IL4R) and the chemokine CCL5 of RANTES (Regulated upon activation normal expressed T-cell secreted). Allelic variation in both genes are associated with atopic dermatitis and asthma in humans (both type I hypersensitivities similar to IBH).
Twelve horses (6 IBH positive and 6 IBH negative) were selected for this expression study with realtime PCR. All IBH positive horses had clinical symptoms at the time of sampling and the IBH negative horses never had shown clinical symptoms and were stabled together with the IBH positive horses so Culicoides contact was assured (case-control set-up).
Whole blood samples (9 ml) were collected from all horses during the summer of 2010 (June-August) using VenosafeTM K2-EDTA tubes by jugular venipuncture and used within 6 hours. Mononuclear cells were isolated from peripheral blood by density gradient centrifugation using Ficoll paqueTM and stored in Trizol at -80 °C until extraction of RNA using the phenol chloroform method. Expression levels of IL4R and CCL5 were measured using qRT-PCR with the relative standard curve method.
Three stable housekeeping genes (GAPDH, ACTB en B2M)with an average expression stability lower than 1.5 were selected using GeNorm. No differential expression was found for IL4R and CCL5 in mononuclear cells isolated from peripheral blood (P=0,5483 and P=0,4874).
Conclusion: Insect bite hypersensitivity (IBH) is an allergic reaction to Culicoides. There is no curative treatment for IBH, but since there is a genetic predisposition, a genetic analysis may lead to the development of a marker assisted selection method (MAS). MAS will make it possible to select on the sensitivity for IBH, hereby reducing the prevalence in the population.
-- ISES Conference Abstract
