Restriction of lentivirus in monkeys.

Retroviruses are able to cross species barriers and have done so many times throughout evolution. Perhaps as a consequence, dominant mechanisms have arisen to block infection by murine retroviruses in mice (restriction factor Fv1) and humans (restriction factor Ref1), as well as in other mammals. Here we describe a block to HIV and simian immunodeficiency virus in monkeys. Like previously described restrictions the block is saturable and gives rise to multiple-hit infection kinetics. Furthermore, like restriction of murine leukemia virus in humans, the block is before reverse transcription. Intriguingly, African green monkey cells are able to block both HIV and simian immunodeficiency virus, and each virus is able to saturate and abrogate the restriction of the other, suggesting that a common factor is responsible.