Study finds gorilla origins in half of human AIDS virus lineages

Revealing new
details about the origins of AIDS, scientists
said on Monday half the lineages of the main
type of human immunodeficiency virus, HIV-1,
originated in gorillas in Cameroon before
infecting people, probably via bushmeat
hunting.
HIV-1, which causes AIDS, is composed of
four groups, each coming from a separate
cross-species transmission of a simian version
of the virus from apes to humans.
Previous research identified chimpanzees in
southern Cameroon as the source of HIV-1
group M, which has infected more than 40
million people worldwide and triggered the
AIDS pandemic, as well as the geographically
limited group N, identified in only about 20
people.
Until now, the source of the two other groups,
known as O and P, had not been confirmed.
The new research, published in the journal
Proceedings of the National Academy of
Sciences, showed those groups originated in
western lowland gorillas in southern
Cameroon.
"Thus, both chimpanzees and gorillas harbor
viruses that are capable of crossing the
species barrier to humans and causing major
disease outbreaks," said virologist Martine
Peeters of the Institute for Research and
Development and University of Montpellier in
France.
The researchers examined fecal samples from
different gorillas across central Africa,
including western lowland gorillas, eastern
lowland gorillas and mountain gorillas in
Cameroon, Gabon, the Democratic Republic of
Congo and Uganda, for evidence of the gorilla
version of HIV.
Genetic analyses implicated the western
lowland gorillas as the source of HIV-1 groups
O and P.
"The mode of transmission is most likely
exposure to infected blood and/or tissues
during hunting and butchering for bushmeat,"
Peeters said.
Group O viruses, the second most common
HIV-1 lineage, have spread across Cameroon,
Gabon, Nigeria and neighboring countries and
have infected about 100,000 people. Group P
viruses have been documented in just two
Cameroonian patients.
The researchers said group O emerged at the
beginning of the 20th century. Group P arose
sometime later that century.
University of Pennsylvania microbiologist
Beatrice Hahn, the study's other co-leader,
said there does not appear to be any inherent
viral property that prevented the group O
lineage from becoming a pandemic-causing
pathogen like group M. "Hence, on this
occasion, humans got lucky," Hahn said.
Another virus type, called HIV-2, is mainly
restricted to West Africa, less easily
transmitted than HIV-1 and has a slower
progression to AIDS. It was transmitted from
monkeys called sooty mangabeys to humans in
West Africa.