These experiments confirmed that the observed cluster of adaptations resulted in resistance specifically to cercopithecine lentiviruses, but had no effect on restriction of other retroviruses, including lentiviruses of other, non-cercopithecine primates. (sciencedaily.com)
Nor is it clear how the virus causes cancer, although other retroviruses are known to do so... (newscientist.com)
They have known for many years that HIV, like other retroviruses, needs help from its host's cellular machinery — for example, to transcribe its genetic material. (newscientist.com)