Immunity & infection
Marek's disease (MD) is a herpesvirus-induced lymphoma in chickens with a significant economic impact to the poultry industry, costing the industry over $1 billion annually worldwide. MD is controllable by vaccination and improving genetic resistance in the host. Two inbred layer lines, matched at the MHC locus, have been bred for high (Line 63) and low (Line 72) genetic resistance, respectively, to MD. We identified large differences in TCR Vbeta usage in the peripheral T cells of these bird lines by flow cytometry. In the chicken, two families of Vbeta genes have been identified (Vbeta-1 and Vbeta-2). While TCR Vbeta-1+ T cells are more prevalent in both lines than TCR Vbeta-2+, MD-resistant birds used the Vbeta-2 TCR at very low rates. During infection with Marek’s disease virus, Vbeta usage on CD4+ T cells was stable in both lines until day 21 post-challenge, when lymphomagenisis is occuring. Conversely, an increased bias towards Vbeta-1 TCRs was found as early as day 8 in CD8+ splenocytes in the MD-resistant chicken only. We hypothesize that differences in TCR repertoire may play a direct role in CD8+ T cell-mediated resistance to MD-induced tumors. We are comparing TCR usage in an additional MD resistance model which varies only at the MHC locus; as well as in a panel of Lines 63x72 recombinant strains, in order to further establish the importance of TCR usage in MD and to identify genomic regions which influence TCR expression in the chicken.