[Specific genetic features of the Russian forms of bovine leukemia virus]

Genetic peculiarities of bovine leukemia virus isolates (BLV) spread throughout Russia and Ukraine (BLV-1, BLV-2, and BLV-4) have been characterized based on pol gene polymorphism. Seven viral forms have been detected. The variability of BLV isolates did not exceed 1% within one form. Despite the recent inhabitation of BLV in Russia in the middle of 20th century, Russian BLV variants are characterized by several specific nucleotide substitutions. Point mutations that result in the changes in the aminoacid sequence of reverse transcriptase of BLV specific to distinct viral forms were observed. C --> G transition at the 2752 position (relatively to the reference genome AF033818), which results in the substitution of glutamic to asparaginic acid (GAG --> GAC), is specific to form BLV-2. This mutation was demonstrated in BLV isolates from Ukraine. The T --> G substitution at the 2758 position, which results in the substitution of isoleucine for methionine (ATT --> ATG), is specific to BLV-4 and BLV-7 forms. The BLV-4 form was only detected in Russia and Ukraine. The present study also includes a review of the published data concerning BLV variability. The existing classifications of BLV forms have been critically conceived and the new optimal classification of BLV forms with the maximal resolution has been suggested.