Natural distribution of squirrel monkey retrovirus proviral sequences in primate DNAs

3H-labelled 70S RNA of squirrel monkey retrovirus (SMRV) hybridized to a high degree (greater than 52%) to the DNA of various tissues of two squirrel monkeys. Hybridization of the same probe to DNAs of other primates including New World monkeys (Woolly monkey, capuchin, owl monkey), Old World monkeys (rhesus, African green), apes (gibbon, chimpanzee), and human (A204 cells infected with MPMV) revealed no significant hybridization. Analysis of the kinetics of hybridization indicated that SMRV provirus was present in multiple copies in various squirrel monkey tissues (C0t 1/2 = 120 to 400) and in SMRV-infected A204 cells at a low number of copies (C0t 1/2 = 1500). These results demonstrate that SMRV is an endogenous virus of squirrel monkeys and the first isolated from a New World monkey.