Olomski F, Fettelschoss V, Jonsdottir S, et al. - Researchers explored the function of IL-31 in insect bite hypersensitivity (IBH) of horses and developed a therapeutic vaccine against equine IL-31 (eIL-31). They quantified levels of IL-31 in allergen-triggered PBMCs and skin punch biopsies of IBH lesions and healthy skin from IBH-influenced and healthy horses. The vaccine comprised eIL-31 covalently coupled to a virus-like particle obtained from cucumber mosaic virus carrying a tetanus toxoid universal T-cell epitope. A rise of IL-31 in PBMCs was noted. IL-31 was exclusively detectable in skin lesions of IBH-affected horses. A reduction in delta clinical scores was brought about by vaccination against eIL-31, relative to prior untreated IBH season of the same horses and to placebo treated horses in the same year. Good tolerability of the vaccine was reported, with no safety concerns. Findings revealed the involvement of T_H2-derived IL-31 in IBH pathology, and therefore, clinical scores in affected horses were alleviated by the immunotherapeutic vaccination approach targeting IL-31.