HIV-1 Most Likely Originated In 1930s
By Deborah Mitchell
SAN FRANCISCO, Feb 01 (Reuters Health) -- The first case of HIV infection mostly likely
occurred around 1930 in west Africa, according to Dr. Bette Korber of the Los Alamos
National Laboratory in New Mexico.
And although the results of her new study do not completely rule out the recently proposed
theory that the HIV-1 pandemic may be linked to a series of polio vaccines administered in
Africa between 1957 and 1959, they make it highly unlikely, she told attendees Tuesday at
the 7th Conference on Retroviruses and Opportunistic Infections.
Using a fossilized HIV-1 viral sequence (ZR59) dating back to 1959, the oldest currently
available, Korber's group examined numerous HIV-1 sequences available over a 20-year
time-frame to project back 60 years.
The team used very sophisticated mathematical modeling called "molecular clocks"
to project how long it would take for a particular virus to evolve given the known rates
of mutation and the known molecular relationships.
Using such a model and "taking into account the peculiarities of HIV-1 sequence
evolution," Korber estimates that the first human infection with HIV occurred in west
Africa "around 1930." The virus was probably introduced in the US, possibly
through multiple sources, in the 1970s, she added.
It is unlikely that the polio vaccinations administered in sub-Saharan African in the late
1950s are linked with the spread of HIV, Korber concludes. For this to have occurred, it
would have required multiple sources of HIV-1, at least 10, to evolve simultaneously.
She also points out that the initial introduction of HIV-1 into humans and its subsequent
spread need to be viewed as two different events. As proposed by Dr. Beatrice Hahn's
group, the spread of HIV-1 to its current pandemic proportions was most likely facilitated
by development of the remote region of west Africa, where it is believed to have emerged,
in the 1940s.
At last year's conference, Hahn and her colleagues at the University of Alabama at
Birmingham reported that the primary reservoir for HIV-1 is Pan troglodyte troglodyte, a
chimpanzee species found in west Africa.
"Our analyses offer a very small piece concerning the puzzle of HIV," Korber
said at the end of her presentation. However, judging by the response of her colleagues,
Korber's new analysis provides a sizable addition to understanding the origin of the HIV-1
pandemic.
Korber has "synthesized in a very succinct and complete way the real up-to-date
methodologies that are used to delineate the molecular epidemiology of HIV," Dr.
Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases,
told Reuters Health.
Based on this analysis, it is very likely that the cross-species viral jump from
chimpanzees to humans happened well before the polio vaccine. "It is extremely
unlikely, though not impossible, that it occurred during the time the polio vaccine was
administered in sub-Saharan Africa," he said. Fauci believes that these findings will
end any speculation about a link between the HIV-1 pandemic and the African polio vaccine
trials, "at least among scientists."