Characterization of infectious type D retrovirus from baboons.

Infectious virus resembling type D simian retrovirus (SRV) was isolated from Ethiopian baboons (Papio cynocephalus) (SRV-Pc) housed at the University of Washington Regional Primate Research Center. When baboon peripheral blood mononuclear cells (PBMC) or tissues were cocultured with the H-9 human T-cell line or the Raji human B-cell line, large multinucleated syncytia positive for SRV-2 antigens were observed microscopically. Immunoblot analysis of purified SRV-Pc from cell culture supernatants demonstrated that the viral core and envelope proteins reacted with rabbit anti-SRV-2 serum. Fresh PBMC and cocultured cells were positive by polymerase chain reaction using two different sets of SRV-2 primers. Preliminary sequence analysis of two separate isolates from portions of the SRV-Pc p27 and gp20 regions revealed homology with SRV-1, SRV-2, and Mason-Pfizer monkey virus. The homologies in the p27 segment were 91-94% and the homologies in the gp20 segment were 72-75%.