Genetic diversity of bovine lentivirus distributed in south Asian countrirs

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To understand the genetic diversity of bovine lentivirus (BIV), we have examined serological survey of BIV infection in cattle in Hokkaido and found 10% of positive reactors. From the seropositive animals, 3 BIV were isolated and DNA samples were obtained from peripheral blood lymphocytes of these positive animals for the detection of BIV proviral DNA by nested-PCR to detect a part of the pol gene. A 298-bp pol region fragment specific to BIV proviral DNA was amplified. Nucleotide sequences of the amplified fragments from Japanese BIV field isolates had 99% homology with American isolate, R-29. Amplification of the C2, V1, V2 and C3 regions of the env gene of Japanese BIV isolates were carried out by nested PCR. All 3 isolates seemed to be smaller, several base substitutions were observed in the V1 region and deletions were found in the V2 region of the env gene when compared to that of American R-29 isolate.In Cambodia, samples from 544 cattle and 43 water buffalo were obtained and BIV seropositive rate were 26% in cattle and 17% in water buffalo. Five BIV proviruses were obtained from seropositive animals. Nucleotide sequence of pol region was highly conserved when compared to that of American and Japanese BIV. In contrast, env region of Cambodian BIV field isolates seemed to be smaller than those of American isolates. Nucleotide substitutions which alter amino acid sequences were observed in the V2 region of Cambodian isolates.Total 262 serum samples were obtained from cattle in Zambia and seropositive rate was 11.4%. Four BIV proviruses were obtained by nested PCR. Nucleotide sequences of pol region of these proviruses were highly homologous (over 97%) to that of American and Japanese isolates.