Rfp-Y region polymorphism and Marek's disease resistance in multitrait immunocompetence-selected chicken lines.

Although the influence of the chicken classical MHC in resistance to many diseases is well established, the role of the recently identified, genetically independent, MHC-like region known as Rfp-Y is unclear. The objectives of this study were to analyze the frequencies of DNA polymorphisms of the Rfp-Y region in White Leghorn lines, which were divergently selected in replicate for multitrait immunocompetence, and to determine the association of these polymorphisms with Marek's disease (MD) resistance. Chicks, either with or without herpes virus of turkey (HVT) vaccination, were challenged with 500 ffu of a very virulent Marek's disease virus (Md5) at 2 d of age. The MD-related data were collected for 10 wk. PvuII-digested genomic DNA was hybridized with an Rfp-Y region-specific probe, 18.1. Three Rfp-Y polymorphisms were observed. The frequency of one Rfp-Y polymorphism was significantly different between divergently selected multitrait immunocompetence lines in one replicate only; therefore, the impact of multitrait immunocompetence selection on Rfp-Y polymorphisms is inconclusive. The PvuII defined Rfp-Y region polymorphisms had no association with either innate or vaccine-induced MD resistance to Md5 virus challenge.