Complete nucleotide sequence of a simian immunodeficiency virus from African green monkeys: a novel type of intragroup divergence.

We have determined the entire nucleotide sequence of a full-length molecular clone, termed SIVagm3, which is infectious in vitro and in vivo. The genomic organization was found to be similar to other immunodeficiency viruses of human and simian origin. Comparison of SIVagm3 with SIVagmTYO-1, the only other completely sequenced molecular SIVagm clone, revealed a novel type of intragroup divergence, which is characterized by (1) an unusually high degree of variability in pol in relation to gag and env and (2) a high degree of divergence in the rev and tat genes. Thus, since SIVagm3 and SIVagmTYO-1 evolved from their common ancestor, they diverged in a different manner than human immunodeficiency viruses. Hypervariable regions in env were defined and shown to be relatively restricted in comparison to HIV-1 and HIV-2.