Phylogenetic relationships of bovine immunodeficiency virus in cattle and buffaloes based on surface envelope gene sequences

Isolates of bovine immunodeficiency virus (BIV) exhibit a striking genomic diversity, most of which are located in the viral envelope gene. Since this property of the BIV group of viruses may play an important role in the pat hobiology of the virus, the surface envelope gene, particularly the conserv ed (C) 2, hypervariable (V) 1, V2 and C3 regions, of eleven different isola tes from different environments with different bovine breeds naturally infe cted with BIV, including dairy cows in Japan, buffaloes in Pakistan and dra ught animals in Cambodia, were sequenced. When compared to the nucleotide s equence of American BIV isolates, all Asian BIV field isolates seem to be s maller, several base substitutions were observed in the V1 region, and dele tions were also found in the V2 region of env gene in these samples. Howeve r, deduced amino acid sequences were not so different among isolates from d ifferent bovine breeds, suggesting that bovine susceptibility to BIV infect ion may not depend upon bovine breed or buffaloes. Moreover, phylogenetic a nalysis revealed that genotypes were distinct between Asian and American BI V isolates and these results also provide an information on the molecular e pidemiology of naturally occurring BIV infection in cattle and buffaloes