Nucleotide sequence analysis of SA-OMVV, a visna-related ovine lentivirus: phylogenetic history of lentiviruses.

The nucleotide sequence analysis of the visna-related South African Ovine Maedi Visna virus (SA-OMVV) demonstrates extensive genetic polymorphism among ovine lentiviruses. Differences between visna virus and SA-OMVV proteins range from 8.5 to 35% mismatched amino acids. Moreover, there is a new open reading frame (orf W) in the central part of the genome. A phylogenetic history calibrated by the divergence and isolation dates of these two ovine lentiviruses shows that radiation of the lentiviridae family is a recent event. Visna virus and SA-OMVV evolved independent of each other for about 42 years. The inferred molecular clock was used to calculate the minimal time elapsed since the divergence of some lentiviruses: 93 years for ovine and caprine lentiviruses, 430 years for ungulate and primate lentiviruses, and roughly 200 years for HIV-1, HIV-2, and SIVAGM. BRU, ELI, and MAL HIV-1 isolates diverged in the early 1960s.