Lentiviruses have apparently been infecting mammals for tens of
thousands of years at least, and more likely millions to tens of
millions of years.  Felines (lions, housecats, pumas, lepards, etc.)
nearly all have a species-specific feline immunodefieicny virus, as do
bovines, equines, caprines and primates.

Among the primates, only African, and not New World, Asian or
Madagascar primates have lentiviruses.  The great apes; chimpanzees,
gorillas, organgutans and humans also appear to not have co-evolved
with lentiviruses.  The chimpanzees appear to have picked up a
lentivirus, now known as SIV-chimpanzee, from some smaller primte in
the last few thousand years.

Humans have picked up Simian Immunodeficiency viruses at least 10
times, most likley all within the past 70 to 100 years.  There have
been at least 7 transfers of SIV from sooty mangabeys to humans, to
cause the HIV-2 A through G groups.  There have been at least 3
transfers of SIV-chimpanzee from chimps to humans to create the HIV-1
M, N and O groups.  HIV-1 M group viruses have caused the global AIDS
pandemic, while all of the other HIVs account for a very minor number
of AIDS cases.

Humans have interacted with chimpanzees in many ways, with increasing
frequency in the past 100 years.  We hunt them for food, kill mothers
to steal their babies for pets or to sell to zoos.  We keep them to
preform in circuses, or to be research subjects.  Likewise, sooty
mangabeys are often kept as household pets or eaten for food.  Today,
the African "bushmeat" trade is a multi-million dollar per year
business, which puts humans at risk of picking up many more viruses and
bacteria which are adapted to primates.

A recent publication by Beatrice Hahn's group has now shown that the
viruses which created the HIV-1 M and N groups can still be found in
wild bands or tribes of chimpanzees in Southeastern and Centraleastern
Cameroon, respectively.

Keele BF, Van Heuverswyn F, Li Y, Bailes E, Takehisa J, Santiago ML,
Bibollet-Ruche F, Chen Y, Wain LV, Liegeois F, Loul S, Mpoudi Ngole E,
Bienvenue Y, Delaporte E, Brookfield JF, Sharp PM, Shaw GM, Peeters M,
Hahn BH. Chimpanzee Reservoirs of Pandemic and Nonpandemic HIV-1.
Science. 2006 May 25;
PMID: 16728595

A book published in the late 1990's argued that chimpanzees from
north-central Zaire (now the Democratic Republic of Congo) could
possibly have been used to prepare local batches of polio vaccine.
Neither the epidemiology of human AIDS, nor the locations of
SIV-infected wild chimpanzees matches up with that argument.  Likewise
there is no solid evidence that chimpanzee tissue cultures were ever
used in polio vaccine manufacturing.  The chimpanzees were used to test
polio vaccine, but not to grow it.