Phylogenetic and mutational analysis of bovine leukemia virus (BLV) tax gene in specialized dairy production systems in Antioquia, Colombia.

The bovine leukemia virus (BLV) is a pathogen of high importance for the dairy industry. Currently, twelve genotypes have been described worldwide with different pathogenicity and virulence, so it is critical to evaluate the circulating genotypes in each country/region to associate this information with risk situations. The aim of this work was to perform a phylogenetic and mutational analysis of the BLV tax gene in cows that belong to specialized dairies in the Department of Antioquia, Colombia. A conventional PCR for the tax gene was performed on 86 bovine samples. Sanger sequencing was carried out on 22 PCR products with a size of 959 bp. The sequences obtained were aligned and analyzed using the Maximum Likelihood and Bayesian phylogenetic approaches. A predictor was used to analyze the possible impact of amino acid substitution on the Tax structure and function. Although all sequences were found to belong to genotype 1, four of the 22 sequences were grouped into a different subclade G1A. Fifty percent of the samples showed punctual mutations in their amino acids. Mutation S104L was identified as "possibly harmful," while the V146A change found in all subclade G1A samples was identified as "possibly benign." Although further studies are necessary to determine whether there is an effect of these mutations on the development of the disease, this study presents part of the evolution of the virus and the changes at the amino acid level that are occurring in cattle from specialized dairy farms in Antioquia.