The Wall Street Journal, February 1, 1999
Michael Waldholz

Using state-of-the-art gene probing techniques, researchers have tracked the virus's origin to chimpanzees who have roamed the once-isolated rain forests of central West Africa for hundreds of thousands of years.

The researchers say they have persuasive evidence suggesting that a simian virus closely related to HIV jumped from monkeys to humans, and then later mutated into its current deadly form, following one of many inter-species transmissions during the past 50 years.

Based on studying current cultural practices in several West African countries, virologists believe humans were infected by the primate virus through blood contact during the hunting and slaughtering of the chimps for food. The researchers say that it seems that versions of the HIV -like simian virus have likely jumped to humans numerous times over the past centuries, but were either harmless or were not transmitted widely.

The current infection is probably the result of many exposures in recent decades resulting from the growing increase in the killing of primates for human consumption that is accompanying the incursion of civilization and logging commerce into the wild.

In a scheduled presentation last night to an annual HIV /AIDS science conference here, microbiologist Beatrice Hahn of the University of Alabama at Birmingham planned to show data indicating that a virus isolated from a stored blood sample from a female chimpanzee who died in captivity in 1985 is genetically more closely related to HIV than any other simian virus previously identified. Virus researchers who saw the genetic comparisons say it provides the strongest evidence yet tying a specific species of chimpanzee to the original source of HIV .

"Chimpanzees are being frequently hunted for food, especially in West-Central Africa, and we believe that HIV was introduced into the human population through exposure to blood during hunting and field dressing of these animals," says Dr. Hahn, who led a team of investigators from her institution and elsewhere that analyzed the blood sample over the past year.

Researchers say the discovery may turn out to have far-reaching implications. In particular, the simian virus doesn't appear to cause disease in the chimpanzees, suggesting that, over the centuries, the primates' disease-fighting immune systems have learned to control the virus, keeping the viral infection benign.

George Shaw, part of the research team in Alabama, says that because humans and chimpanzees are 98% identical in their genetic makeup, by studying the chimps' immune system "we may obtain important clues" as to how to prevent and treat the devastating infection in people. The goal would be to develop vaccines that stimulate an immune response similar to the one that keeps the virus in check in the chimps.

In addition, the link is expected to focus attention on the rapid rise of the so-called "bushmeat trade" in parts of Africa which is decimating the chimp population along with other primates and wild animals. "I simply was unaware of the terrible consequences of slaughtering that's going on," Dr. Hahn says.

She and others worry that the killing of the chimps will make it difficult to study the natural course of the virus in chimpanzees in the wild. Moreover, she says that crude butchering of the chimps in the forests means that it's likely people are still being exposed to the virus.

"We cannot afford to lose these animals, either from an animal conservation or a medical investigative standpoint," Dr. Hahn says.

But the scientific evidence isn't likely to be universally welcomed. Many African nations aren't happy to be identified as the original source of a viral plague that has spread to 34 million people world-wide, 90% of whom live in sub-Saharan Africa. The focus on hunting and dietary habits unfamiliar to the developing world also could make some Africans uncomfortable.

"I just don't know how they'll react," said Jane Goodall, the pioneering British primate conservationist and founder of the Jane Goodall Institute, which runs primate sanctuaries in Africa. In an interview from her home in Britain last week , the 65-year-old Dr. Goodall said the population of wild chimpanzees in Africa has dwindled to fewer than 150,000 from one to two million 100 years ago. "The killing is terrible," she said. "We hope the new discovery will help draw the world's attention to the problem."

Scientists had long speculated that HIV came out of Africa via human contact with one of several species of chimps or other monkeys. But about a year ago, Dr. Hahn and her group, including scientists at the University of Nottingham in Britain, began studying the virus isolated from a chimp named Marilyn who died in childbirth 14 years ago.

By sequencing parts of the virus's genetic material, the scientists found that more segments of the simian and human virus overlapped than had been identified in three previous simian viruses isolated in recent years from other chimpanzees.

The investigation revealed that the other previously studied simian viruses were more closely related to very rare forms of HIV that don't account for most of the infections in the world. Further evidence came when the researchers realized that Marilyn was from a species called Pan troglodytes troglodytes whose natural habitat overlaps precisely with the region in central West Africa where the major type of HIV was first recognized.

"The finding may not help us fight HIV ," said Joseph Sodroski, an HIV researcher at Dana Farber Cancer Institute, in Boston. "But finally locating the source of the virus may turn out to be an important lesson to us humans."

Dr. Sodroski said the discovery is persuasive evidence that deadly germs can be transmitted to humans from exposure to animals in the wild who previously had been isolated from most human contact. The advance of civilization into other deeply forested regions is likely to generate other viral exposures. Furthermore, he said, the transmission may provide a cautionary note to efforts to use animal organs for human transplantation. In any case, Dr. Sodroski said, he and others will be interested in studying samples of blood recovered from other chimpanzees located in the wild.

But Dr. Goodall and other conservationists say it will be difficult to change the growing practice of hunting and killing the chimps, perhaps creating barriers to conducting research into the wild. Logging companies are building roads deep into the rain forests where few humans have ever traveled. The roads give hunters access to virgin territory, where they kill animals for consumption by the loggers who are far from towns and villages. Dr. Goodall said most of the bushmeat isn't used for subsistence but is being marketed as a delicacy featured in marketplaces in cities and towns.

"We hope to help people in Africa understand the importance of saving the animals," Dr. Goodall said. She added: "Maybe this will help. On the other hand, identifying the chimps as the source of HIV may simply increase animosity to the animals."
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