MHC-B haplotypes impact susceptibility and resistance to RSV-A infection.

We investigated the impact of haplotype of major histocompatibility complex (MHC)-B on the outcome of infection of Synthetic Dam Line (SDL) broiler strain with Rous Sarcoma Virus (RSV). Genomic analysis of MHC-B haplotypes, revealed a total of 12 known standard haplotypes that constituted to twenty-five different genotypes and one new haplotype of 217 bp size, designated BX . The inoculation of RSV-A in SDL chicks resulted in the development of tumors of progressive or regressive phenotypes with varying tumor profile index (TPI). Haplotypes B2 , B21  and B22 had low TPI scores (1 or 2) with less mortality and were resistant to RSV-A tumor. The haplotypes B13 , B13.1. , B15 , B15.1.  and B15.2.  had significantly higher TPI scores (5 or 6), indicating a susceptibility to RSV-A. The genotype, Bx  /Bx , had a mean TPI score of 3.67 ± 1.33, which was closer to the resistant haplotype. Sequence analysis of the new haplotype (BX ) revealed 99.5% similarity with B2 haplotype. Metastases was observed in 44% of chicks and comprised of mixed fibrosarcoma and myxosarcoma.