Abstract
Objective: To associate the proviral load (PVL) of the bovine leukosis virus found in the Harton del Valle (HV) breed with the alleles of the BoLA-DRB3 gene. Methods: In 100 HV animals, the PVL was evaluated using a real-time quantitative PCR and a TaqMan probe; the animals were classified according to their PVL in high proviral load (HPVL) or low proviral load (HPVL). Additionally, the animals were genotyped using the PCR-SBT method. The allele frequencies were estimated. Alleles were associated with HPVL (susceptible, S), LPVL (resistant, R) or neutral (N) using the Odds ratio (OR) statistic and the presence of common amino acids in the R and S alleles were determined. Findings: A total of 22 alleles were found, the *1101 was the most frequent. High-frequency alleles accumulate 71.9%. The PVL mean was 129740 copies/μg of DNA. Seven alleles were associated with PVL, alleles *1002, *1601 and *1701 with HPVL (S) and alleles *0902, *1101, *20012 and *2703 with LPVL (R). The PVL of the alleles S and R was 516966 and 75074 copies/μg of DNA respectively. The allelic frequency R and genotype RR accumulated was higher than that of the alleles and genotypes S. The amino acid Glu located in positions 70 of the DRβ peptide chain was common in the R alleles. Application/Improvements: The resistance to the PVL (LPVL) has particularities in each breed since the alleles according to the literature reports are not the same. These results can be used in selection programs in favor of the genes categorized here as R, and thus, decrease the infection rate of the virus. Keywords: Colombian Creole Cattle, Enzootic Bovine Leukosis, Genetic Resistance
Highlights
The enzootic bovine leukosis (EBL), is an infectious disease, the causative agent is the bovine leukosis virus (VLB) (BLV) is a B-lymphotropic oncogenic deltaretrovirus infecting cattle that shares common biological and structural features with the human T-cell leukemia virus I and II (HTLV-I and II)[1]
The Proviral Load of the Bovine Leukosis Virus is Associated with the Polymorphisms of the bovine leukocyte antigen (BoLA)-DRB3 Gene in the HartonDel Valle Breed
22 alleles were found in the BoLADRB3 gene, of which *1101 was the most frequent (16.88%)
Summary
The enzootic bovine leukosis (EBL), is an infectious disease, the causative agent is the bovine leukosis virus (VLB) (BLV) is a B-lymphotropic oncogenic deltaretrovirus infecting cattle that shares common biological and structural features with the human T-cell leukemia virus I and II (HTLV-I and II)[1]. In the majority of cases, infection is asymptomatic but 30% of BLVinfected animals will develop a persistent lymphocytosis and less than 5% will progress to B-cell lymphoma or leukemia in animals older than 3 years, after a long period of latency characterized by the absence of viral replication[2]. BLV tropism in the host is directed primarily to B cells, has a reverse transcriptase responsible for the synthesis of a DNA copy from viral RNA (provirus). The provirus is integrated into the DNA of host lymphoid cells[3]. Infected cells, surviving host immune response clearance, undergo a tight mRNA BLV transcriptional silencing, promoting cellular transformation and BLV persistence/replication through mitotic division[4,5].
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