Polymorphisms of BoLA-DRB3 gene and its association with resistance / susceptibility to Leucosis in Holstein cattle from La Pampa

Abstract

EBL is a disease of adult cattle caused by the retrovirus, bovine leukemia. It can manifest: aleukemic an asymptomatic form, with a normal number of B lymphocytes in the blood; a form of permanent lymphocytosis, with an increase in the number of B lymphocytes and finally a lymphoproliferative tumor presenta­tion in the form of lymphosarcoma. The alleles of the genes of the Bovine Major Histocompatibility Complex (BoLA) have been associated with resistance and susceptibility to infectious dis­eases. The overall objective of this study was to associate poly­morphisms of the BoLA-DRB3.2 gene, defined by the technique of polymerase chain reaction technique and polymorphisms length of the restriction fragment (PCR-RFLP), with resistance / susceptibility to leucosis in Holstein cows of La Pampa. It relied on a case/control design, for which blood samples were taken to 150 animals in 3 opportunities with intervals of three months each. The case group comprised animals that were positive in the immunodiffusion agar animals test (DIDA) and whose blood lymphocyte count was ≥ 10.000 linf/μl and the control group included cows that ware negative for DIDA and present < 10.000 linf/μl of blood. Fisher’s Exact test and Odds Ratio (OR) of Woolf-Haldane were used to study the association between lym­phocyte count and DIDA results with allelic variants. In 82 ani­mals genotyped by PCR-RFLP, the DRB3.2*22 allele showed an OR = 5.332 (p = 0.0138) and DRB3.2*11 allele had a OR value of 0.11 (p=0.001) and were the most frequent in the control group and in the case group, respectively. These results would showed DRB3.2*22 allele and DRB3.2*11 allele a high risk of having leucosis (susceptibility) and low risk to suffer (resistance) re­spectively. The analysis of the relationship between alleles of the BoLA and resistance/susceptibility to leucosis could be im­proved with deep research on family lineages of dairy cows.