Expression of Interleukin-4 Receptor and CCL5 Chemokine is not Related to Insect Bite Hypersensitivity in Horses

Insect bite hypersensitivity (IBH) in horses represents a type I or sometimes a type IV hypersensitivity to salivary antigens from numerous Culicoides spp and some other insects. Until now, there has been no curative treatment available, but there are clear indications that the susceptibility to IBH is partly heritable. Identification of equine genes that are associated with susceptibility to IBH could lead to the development of a marker-assisted selection method. The aim of this study was to investigate the expression of functional candidate genes in relation to IBH. Based on literature, the interleukin-4 receptor (IL4R) and chemokine CCL5 (CCL5) genes were selected for examination by quantitative reverse transcription-PCR (qRT-PCR). Expression levels were determined in 16 horses: 8 IBH-positive horses, all showing clinical IBH symptoms at sampling; and 8 IBH-negative horses, stabled at the same location (case-control set up). Peripheral blood mononuclear cells (PBMC) were isolated from whole- blood samples, and expression levels of IL4R and CCL5 were measured. No differential expression was found for IL4R and CCL5 in PBMC between IBH-positive and IBH-negative horses (P = .58 and P = .63). Expression of CCL5 and IL4R in PBMC is not related to insect bite hypersensitivity in warmblood horses. Research toward a marker-assisted selection procedures could reduce IBH prevalence in horse populations by means of selection.