Bovine leukemia virus (BLV) causes enzootic bovine leukosis, a worldwide disease that causes substantial losses in the cattle industry. BoLA-DRB3 is a polymorphic gene associated with BLV proviral load (PVL), which dictates disease progression and transmission risk; progeny PVL is influenced by the BoLA-DRB3 alleles of their sires. In addition, two novel single-nucleotide polymorphisms (SNPs) affecting BLV PVL have been identified in Japanese Black cattle. In this study, to identify whether two specific PVL-associated SNPs (SNPT12 and SNPT13) were associated with elevated PVL in Japanese Black cattle, we developed and validated a high-throughput TaqMan-based SNP genotyping assay targeting SNPT12 and SNPT13, clarified the distribution of these SNP genotypes in 178 distinct commercial semen samples from widely used Japanese Black sires, and confirmed that the distribution was based on field blood samples collected from Japanese Black cattle in a nationwide survey across Japan. A total of 199 progeny derived from 36 sires representing three SNPT13 genotypes (TT, TC, and CC) were assessed for SNPT13 genotype and BLV PVL. Progeny from sires with TT genotype exhibited the highest mean PVL, whereas those from sires with CC genotype showed the lowest PVL. The intensity of BLV PVL followed the order: progeny with TT genotype > progeny with TC genotype > progeny with CC genotype. These findings demonstrate that BLV susceptibility is inherited by the progeny via SNPT13 genotypes in semen, and that SNP genotypes in semen offer a useful tool for predicting heritable BLV susceptibility.
Bao et al. (Thu,) studied this question.