Molecular genetic research methods make it possible to evaluate the genetic diversity of bovine leukemia virus (BLV) and are the most informative approaches to its genetic identification. Molecular genetic research methods work well for the phylogenetic analysis of sequenced nucleotide DNA sequences of the provirus, as well as for the polymerase chain reaction-restriction fragment length polymorphism analysis (PCR-RFLP) according to the phylogenetic classification of the pathogen. The purpose of the research was to study the scientific and methodological approaches to the genetic identification of bovine leukemia virus, integrated into the molecular monitoring of infection of cattle with BLV genotypes. The authors used PCR-RFLP-genotyping and comparative phylogenetic analysis of aligned nucleotide sequences of the env gene fragment of the BLV provirus isolates to detect the genotypic affiliation of the cattle from twenty-one livestock farms of the Republic of Tatarstan. As a result, isolates of four out of ten BLV genotypes were found in the Tatarstani cattle, namely genotypes 1, 4, 7, and 8. The research involved a comparative analysis of 505 nucleotide sequences of a fragment of the BLV env gene, including those deposited in GenBank NCBI. The analysis confirms the inconsistency of several earlier PCR-RFLP typing strategies with the current approach in assessing the genotypic diversity by phylogenetic analysis. The improved strategy of PCR-RFLP genotyping of BLV corresponds with its modern phylogenetic classification. The strategy makes it possible to identify all the known genotypes of the viral pathogen. Its validity has been proved by in silico modelling of restrictogrammes and a phylogenetic analysis of the env gene fragment of 57 reference isolates of ten BLV genotypes that generate 57 genotype-associated combinations of diagnostically significant PCR-RFLP profiles.
MODERN MOLECULAR-GENETIC IDENTIFICATION METHODS OF BO-VINE LEUKEMIA VIRUS
