Re: what do monkeys have to do with AIDS?

	Many different species of African primates carry immunodeficiency
viruses.  The primates found in Asia and the New World (south America)
do not carry immunodeficiency viruses.  Human Immunodeficiency Virus
Type 1 (HIV-1) has now infected over 30 million people.  Once infected
with HIV-1, most people (probably greater than 85%) will develop AIDS
(Aquired Immune Deficiency Syndrome) within 10 years of infection.  
HIV-1 is very similar to the immunodeficiency virus carried by chimpanzees
and a very recent paper in Nature Magazine by Feng Gao and Beatrice Hahn
Nature. 1999 Feb 4;397(6718):436-41.  shows how HIV-1 probably came
from chimpanzees to humans, when humans in Africa cut up chimpanzees
for meat.  It is also possible that humans got HIV-1 when a chimpanzee
bit or scratched them, but more likely it was from blood during killing
or cutting up a chimpanzee for food.
	Human Immunodeficiency Virus Type 2 (HIV-2) has so far only 
infected a few hundred thousand people, mostly in Cameroon.  It is
not as transmissible and not as deadly as HIV-1, but still a significant
problem.  HIV-2 is very similar to immunodeficiency viruses carried
by sooty mangabeys, and humans probably got it from these mangabeys
either when they killed them for food, or by being bitten or scratched
by pet mangabeys.  Many people in Africa keep mangabeys as pets.
	We think there have been at least 3 different transmissions 
of HIV-1 from chimpanzees to humans and at least 6 different transmissions
of HIV-2 from mangabeys to humans.  We have not found any cases of
the immunodeficiency virus being transferred from African green monkeys,
Sykes monkeys, Mandrils, or other African primates which carry the
virus.  I am not sure if enough gorillas, oragnutans and other primates
have been tested to be sure they do not carry an immunodeficiency virus.

	Most primates do not get AIDS if they are infected with
their own type of virus.  But if you take the sooty mangaby virus and
infect a macaque with it, the macaque gets AIDS and dies.  Likewise
chimpanzees can get AIDS from sooty mangabey virus and from HIV-1.
By studying why or how the virus and its natural host adapt so they
don't get sick, we might be able to figure out ways to help humans
not get sick from HIV-1 or HIV-2 infection.  People also use primates
to test experimental vaccines and drugs, before testing them
on humans.  You can't just test any old drug on primates, you have
to be reasonably certain it has a chance of working, and not harm
the animal first.  Most researchers are very fond of the primates and
hate to use them, but the only other choice is to use actual humans.

	Cats carry a feline immunodeficiency virus and they sometimes
die of an AIDS-like disease from this.  Cows carry bovine
immunodeficiency virus and horses carry a related virus called
equine infectious anemia virus.  These are all lentiviruses, as
are the primate immunodeficiency viruses.  They are all much more
distantly related to each other than the primate viruses are.
We do not yet know how many different type of these lentiviruses
are ot there, but it seems that a great many mammals carry them.

Brian Foley
HIV Database
Los Alamos National Laboratory
btf@t10.lanl.gov