BoLA‐DRB3 alleles influence proviral load and peripheral blood lymphocyte distribution in bovine leukaemia virus‐infected cattle

Abstract

BackgroundBovine leukaemia virus (BLV)‐infected Holstein cattle carrying certain bovine leukocyte antigen (BoLA)‐DRB3 alleles were previously shown to be resistant to BLV provirus multiplication, while those carrying other alleles were susceptible. This study aimed to determine whether the BoLA‐DRB3 alleles carried by BLV‐infected cattle could predict proviral load (PVL) and peripheral blood lymphocyte (PBL) count distribution (PVL/PBL distribution).MethodsBlood samples from Holstein cattle on four dairy farms were tested for the presence of BLV antibodies using a commercial ELISA. The PVL and PBL levels of the BLV‐infected cattle were also measured, and genotyping was performed to identify the BoLA‐DRB3 alleles they carried, impact of the various BoLA‐DRB3 alleles on the PVL/PBL distribution was then investigated.ResultsOf the 316 cattle tested, 114 were positive for BLV. BLV‐infected cattle carrying BoLA‐DRB3 alleles DRB3*009:02, DRB3*002:01 and DRB3*014:01:01 were classified as resistant (n = 43), those carrying DRB3*012:01 and DRB3*015:01 alleles were classified as susceptible (n = 42) and the remaining cattle were classified as nonsusceptible/nonresistant (n = 29). Multiple regression analysis revealed that PVL was positively correlated (p = 2.1 × 10−23) with PBL count and age was negatively correlated (p = 1.9 × 10−6) with PBL count. Cattle with DRB3*014:01:01 tended to have a lower PBL count (p = 0.031).LimitationThe effects of the BoLA‐DRB3 alleles DRB3*002:01, DRB3*009:02, DRB3*012:01 and DRB3*015:01 on PVL/PBL distribution were unclear due to the small numbers of BLV‐infected animals carrying these alleles.ConclusionThe BLV transmission risk in cattle can be estimated by examining their BoLA‐DRB3 alleles.