Newsday - February 2, 2000
Laurie Garrett, Staff Correspondent

That conclusion, presented yesterday by Bette Korber of Los Alamos National Laboratory in New Mexico, had been highly anticipated here at this year's Conference on Retroviruses. The origin of HIV, and accusations that it was inadvertently introduced in contaminated oral polio vaccines in Africa from 1957 to 1961, have been hotly debated for years.

The Los Alamos results not only offer strong refutation of those allegations but, together with other research presented here this week, provide a striking vision of where HIV came from and where the evolution of this virus may be headed.

The oldest viral sample discovered to date came from a patient who died in Leopoldville, Congo, in 1959. That 1959 virus was a member of the M class of HIVs-the type responsible for most HIV cases today. And though it was an old virus, it was clear from genetic analysis that it was not the "mother of all HIVs."

Some people noted that the 1959 date coincided with the first big oral polio vaccine campaigns in Central Africa. In "The River," published last year, British journalist Edward Hooper charges that Drs. Hilary Koprowski and Stanley Plotkin of the Wistar Institute in Philadelphia used African chimpanzee cells to grow polio viruses that were the basis of their vaccine. Those chimp cells, he argues based on circumstantial evidence, were from an animal infected with the virus that became the mother of all HIVs.

In a news conference yesterday, Plotkin, 67, reiterated "that no chimpanzee tissue was used to make the oral polio vaccine. The introduction of HIV from chimpanzees occurred well before the vaccine."

Korber, whose specialty is evolutionary statistics, led a diverse team of specialists that set out to resolve the debate over the origin of the pandemic. The team used the Los Alamos Nirvana Machine, capable of making one trillion calculations per second.

The calculations used two firm dates: the 1959 virus and a virus that appeared in Thailand in 1987. Those two dates allowed them to compare the genetic details of 160 other HIVs found worldwide in the past 20 years. Nirvana generated "family trees" of the virus and gave statistical explanations for how related various viruses were, when each first appeared and how rapidly HIV was evolving. Most important, it allowed scientists to see when the virus' roots were first set down. Nirvana put the date of origin at 1930, with a statistical range of error that could put it as early as 1915 or as late as 1942.

Nirvana also told the scientists that the virus is older in Haiti than in the United States, possibly appearing on the Caribbean island in the early 1960s. And the first U.S. strain probably surfaced around 1970.

After that, Korber said, "there has been a quite frightening diversification of the virus" as the original "tree" of HIV has branched and evolved worldwide. Korber noted that it is clear that HIV started as an animal virus and jumped to humans.

An entirely unique other class of HIV is also emerging in Western Africa. It's called the N class of HIV. In this week's issue of Science, Dr. Beatrice Hahn of the University of Alabama in Birmingham and Dr. Kevin DeCock of the U.S. Centers for Disease Control and Prevention outline a probable series of events in Western Africa. In all likelihood, they argue, both the M and N virus groups jumped from chimps to human hunters who became infected while butchering the animals. After that, the spread among people proceeded sexually.

The new N-type HIVs look like genetic blends of the ancient M virus, the strain responsible for the global AIDS pandemic, and SIV, the animal form of HIV.

"It suggests the prevalence of HIV in chimps is much higher than we had assumed," Hahn said.

To date, six HIV-like strains have been discovered in chimpanzees. One looks like an M-class HIV. In all cases the viruses cluster in Cameroon, Gabon and the Central African rain forest region.

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