Newsday - February 1, 1999
Laurie Garrett - Staff Correspondent

But while the finding could be a potential gold mine for those seeking a vaccine or cure, researchers say the missing-link strain - a unique genetic blend of HIV and SIV (or simian immunodeficiency virus) - is carried by a type of chimpanzee that could be extinct within three to 10 years. The chimps are being driven from their homes in the rain forests of the Congo River Basin and West and Central Africa by loggers, and massacred for their meat.

Dr. Beatrice Hahn and her colleagues at the University of Alabama announced discovery of the unique strain yesterday at the opening session of the sixth annual national retrovirus meeting. And she said an international effort to save the chimps is already beginning.

"It took us 20 years to find where HIV-1 came from, only to realize that the very animal species that harbors it is at the brink of extinction," Hahn said. "We cannot afford to lose these animals . . . we can't afford to have them end up in the cook pot!"

Until recently scientists had nearly given up hope of figuring out how the Human Immunodeficiency Virus first infected humans, or where the AIDS epidemic began. Though all evidence indicated that HIV-1, the primary strain, originated as a monkey virus, no one could find anything resembling that most lethal form of HIV in primates other than human.

Last year, however, Hahn obtained blood samples taken in 1985 from a healthy chimpanzee named Marilyn that had been caught in the wild, a member of the Pan troglodytes troglodytes subspecies native to Central Africa. She then isolated a previously unknown virus from Marilyn's blood that turned out to be a blend between well-known monkey forms of the virus and the humanly infectious HIV. The virus appears to be harmless to chimpanzees, offering no symptoms in this subspecies.

Marilyn died of non-AIDS causes at age 26. Since the initial discovery, a Pasteur Institute research team led by Dr. Simone Barre-Sinoussi, the co-discoverer of HIV, has turned up three others with the blended strain. Working independently in Cameroon, Barre-Sinoussi found them in a survey of 29 chimpanzees.

"We conclude that [P.t. troglodytes] is the natural host and reservoir of HIV-1," Hahn writes in a report to be published Thursday in the journal Nature, co-authored with scientists from the Institute of Genetics in Nottingham, England; the Laboratory of Structural and Genetic Information in Marseille, France; Laboratoire Retrovirus in Montpelier, France; and the National Cancer Institute's AIDS Vaccine Program.

Dr. George Shaw, a co-author and fellow University of Alabama researcher, says the "importance of the current findings could be far-reaching" since the "chimpanzees are identical to humans in over 98 percent of their genome . . . yet they appear to be resistant to the damaging effects of the AIDS virus on the immune system.

"By studying the biological reasons for this difference," he explained, "we may be able to obtain important clues concerning the pathogenic basis of HIV-1 in humans and possibly new strategies for treating the disease more effectively."

Now that they know the strain exists, researchers said they hope soon to start looking for it in humans. Such an effort, however, requires a complex genetic analysis of blood samples since the blended strain reacts similarly to HIV-1 in the antibody tests generally used for diagnosis.

If one maps a genetic "family tree" of all known HIVs and SIVs, this virus looks like the Adam-and-Eve strain, Shaw said, the mother of all HIVs. Once the strain known as SIVcpz made its way into the human species, probably about five decades ago according to recent studies, it mutated into the existing human strain, adapting naturally to its new host.

Hahn's dramatic call to save the chimps is already being picked up worldwide by both top AIDS scientists, such as Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases in Bethesda, Md., and well-known African wildlife researchers such as Jane Goodall and Richard Leakey.

"If these wild chimpanzees disappear, so too will the pieces of the AIDS puzzle," Goodall wrote in an e-mail to Newsday last week.

"Only if we work together to preserve the wild chimpanzee populations can scientists like Dr. Hahn study the way in which chimps have adapted to the virus," she said. "Only if we keep the chimpanzees in their natural setting can we learn how the virus transfers from one chimpanzee to another . . ."

Noting that SIV has long been seen in infected, yet healthy monkeys, Fauci suggested the chimp finding could reveal, "what the host defense mechanisms in the chimps are that enable them not to get sick," and, by conjecture, what's wrong with human genetics, permitting HIV infection to be a lethal event.

"The most important practical implication of our findings, I believe, is the realization that chimpanzees may represent both cause and solution to the AIDS problem," Hahn said.

Hahn said she scoured captive chimp populations in zoos and animal colonies, learning they were not infected with the SIVcpz virus. Only wild chimpanzees were exposed to and transmitted the virus, presumably from mother-to-child and sexually.

"So, we identified the species," Hahn said. "And we know they're naturally infected."

It seemed a simple matter, then, to contact animal researchers in West Africa and obtain hundreds of wild chimp blood samples for analysis. Or so Hahn thought, until she discovered that the number of this type of chimp available in Gabon, the Congo, Equatorial Guinea, Cameroon and the Democratic Republic of the Congo was shrinking daily because of wholesale slaughter. Through a series of e-mail queries to chimp experts, Hahn then connected with Karl Ammann in Kenya, a wildlife preservationist and member of the London-based World Society for the Protection of Animals.

A Swiss-born former hotel manager, Ammann has documented a dramatic West African surge in so-called "bush meat" trade, or the hunting of monkeys, chimps, gorillas and other animals for sale as food in Africa's large cities. Though some African cultures have long consumed monkey and ape meat, they have done so in small quantities, leaving little lasting impact on the overall size of the animal populations.

What's new, Ammann says, is a sudden shift in hunting practices, sparked by the 1994 devaluation of the French-subsidized West African currency, the CFA. When Paris stopped artificially boosting the CFA it fell in value by half, and European investors moved into the region, finding resource development highly affordable in the new economic climate in 15 former French colonies.

The chief booming industry is logging, which since 1994 is practiced in the West African region by at least 67 non-African companies.

According to a 1996 reckoning by the World Bank, those companies currently log more than 4 million cubic meters of wood annually from Cameroon, alone, a nation 33 percent of whose lands are rain forest. (By comparison, 28 million cubic meters of wood is logged annually in all Latin American countries, combined.) The pace of logging operations has suddenly exploded further, according to local experts, because the governments have passed laws mandating expensive reforestation efforts by any company that logs after year 2000.

Loggers are building dirt roads, which, in turn, are providing hunters with previously unheard of access to the once remote rain forest.

"The rate of loss of habitat, natural resources and species in tropical Africa is now higher than ever before," Ammann says. "The hunting has increased drastically . . . it's getting worse quite quickly. Wherever logging starts up, hunting follows."

Ammann provided Newsday with more than four hours of videos taped recently in Cameroon that illustrated the tight link between loggers and hunters. Truck drivers who haul logs out of the forest typically earn extra cash by giving groups of carbine-armed hunters rides into formerly remote areas. The drivers also often purchase monkey and ape carcasses from the hunters, either to eat or sell in town. Ammann's videos show families gathered around their dinner seatings, chewing on charred chimpanzee hands.

"The problem really stems from the commercialization" of the hunting, said Michael Hutchkins, chief scientist for the American Zoo and Aquarium Association. "To commercialize something you need a way to collect it, transport it and market it. The collection and marketing were already in place. What was missing was a way to get [bush meat] into the cities. The logging roads really provided that."

In some cities, Ammann said, "Gorilla and chimp meat is two times more expensive than beef or pork, so it's not the poor who buy it. It's the middle class and the rich, who know what they're buying."

But David Wilkie, who has devoted 20 years to the study of hunter-gatherers in Central Africa, says much of the bush meat consumed in this area is done so by poor people, for whom hunted animals are the only affordable source of protein. For example, he pointed out, a market survey in Ngotto, in the Central African Republic, found that bush meat sells for less than 75 cents a kilo, while chicken costs $3.52 per kilo.

Before departing last week for Africa, Wilkie spoke with Newsday from his office in Boston, where he does consulting research for the World Bank and other international agencies. While he concedes there are urban areas where dining on chimpanzee is considered gourmet, it is generally not Africa's wealthy gourmands who are depleting the chimp and gorilla populations. It is, he says, the starving poor.

Already, a variety of studies in the region show that between 43 and 100 percent of the chimp and gorilla populations in any given forest area have been killed by hunters since 1990. And because the large primates, like human beings, reproduce slowly, giving birth to only one or two babies at a time, experts say these areas will be slow to repopulate.

Hahn is now spearheading an alliance between laboratory HIV researchers and leading primate conservationists, aimed at stopping bush-meat hunting of chimps.

Next month, she said, scientists will gather at the Centers for Disease Control and Prevention in Atlanta to discuss the effort. Another meeting, organized by the American Zoo and Aquarium Association, will address the issue within two weeks in Silver Spring, Md.

Time is short, however. Scientists believe only 50,000 to 70,000 lowland gorillas remain alive in Africa, and Ammann calculates 800 are killed annually in Cameroon, alone. In one city in northern Congo the Wildlife Conservation Society calculated that 12,500 pounds of bush meat were sold each week, much of it chimpanzee and gorilla.

There are an estimated 200,000 chimpanzees, of all species, remaining in Africa, according to wildlife experts. No one seems to know exactly how many P.t. troglodytes are alive, but their entire habitat range is located right in the middle of recent logging operations. Ammann estimates the animals could be hunted into extinction within less than 10 years; Hahn says other experts have told her it could happen in just three years.

Meanwhile, European researchers have developed techniques for collecting wild chimp feces and analyzing them for the presence of viruses. Such a method could help discern how widespread SIVcpz infection is among the remaining wild chimps, but researchers say it cannot answer larger immunological questions. Only study of live chimpanzees can do that.

Hahn and her colleagues are convinced that HIV jumped from the P.t. troglodyte chimps to humans many times in the recent past. While the infection can't be passed by eating cooked meat or meat that has been left out in the open air, it can be transmitted to hunters or butchers through blood-to-blood contact. She says it is very possible that the SIVcpz strain is being reintroduced today into the human species in the Congo Basin region.

Because of this, Hahn said she plans in the near future to study blood samples from local hunters to determine if the blended strain is being carried by humans in the area - a task she fears may be complicated by her efforts to save the chimps. If the hunters feel their livelihoods are under attack, she said, they could refuse to be involved.

Hutchkins, meanwhile, argues that the animal eradication issue could affect the course of other diseases as well. Chimps in this same region have been known to suffer periodic epidemics of Ebola, the deadly hemorrhagic fever virus, and could well be carriers of other as-yet unidentified microbes.

In the absence of wild chimps for study, one alternative would be to simply analyze SIVcpz in captive-born P.t. troglodyte chimps in order to see how their immune systems respond to the virus. But there are key obstacles here, as well: Available supplies of the virus are minuscule, and most chimps living in animal colonies and zoos are of other subspecies.
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