Nucleotide sequence of feline immunodeficiency virus: classification of Japanese isolates into two subtypes which are distinct from non-Japanese subtypes.

Seven isolates of feline immunodeficiency virus (FIV), Shizuoka, Yokohama, Sendai-1, Sendai-2, Fukuoka, Aomori-1, and Aomori-2, were isolated from FIV-seropositive domestic cats in Japan, and their proviral DNAs were amplified by PCR. The nucleotide sequences of their env and gag genes were determined and compared with those of previously described isolates: U.S. and European isolates and one Japanese isolate, TM2. Phylogenetic analyses of complete env gene sequences demonstrate that worldwide isolates are classified into three subtypes: Japanese TM2, Japanese Shizuoka, and non-Japanese subtypes (U.S. and European isolates), with 20% amino acid distances from each other. This pattern indicates that an evolutionary radiation of these three subtypes of FIV occurred at approximately the same time. The sequence data of gag genes also confirmed these results. Furthermore, the Sendai-1 isolate was identified as an imported FIV isolate.