Chicago Tribune
Monday, January 31, 2000
Scientists push HIV's origin back to '30s
By Jeremy Manier
In a finding that could help vaccine researchers anticipate future changes in the virus that causes AIDS, scientists now believe the global pandemic took root in central west Africa roughly around 1930, decades earlier than many experts had thought.
The new estimate, calculated by a team that includes Northwestern University researchers, already is spurring a fresh historical inquiry into the mystery of how a form of HIV jumped the species barrier from chimpanzees to kill more than 16 million people worldwide. The question is expected to be a prime point of interest Tuesday at a meeting in San Francisco of the world's top AIDS researchers.
In an attempt to explain the early routes of human contact with virus-infected chimps, some researchers are looking at events long seen as unconnected to the spread of HIV, such as African railway construction in the first decades of the 20th Century.
The findings were aired publicly Friday in the journal Science, within an HIV research review article by Dr. Beatrice Hahn of the University of Alabama at Birmingham. Hahn's paper included a description of a still-unpublished study on the date estimate, performed by researchers at Northwestern, Alabama and the Los Alamos National Laboratory in New Mexico.
Pushing back the time when HIV first appeared in people would be especially significant because the earliest known HIV infection was discovered in a stored blood plasma sample dating to 1959. Many experts concluded that the virus had gained a foothold just a few years before then.
Although researchers caution that the new 1930 estimate has a 20-year margin of error, it is based on increasingly sophisticated computer models of how HIV evolves.
In addition to helping vaccinemakers forecast the evolution of the virus, understanding the enigma of HIV's origins would let experts assess whether more epidemics might spring from African primates. Findings in the last year suggest as many as 27 different primate species in Africa are naturally infected with simian viruses related to HIV, carrying the risk of more transmissions to people.
It may well be impossible to pinpoint the precise place or time when the AIDS virus first infected people, said Dr. Steven Wolinsky, a researcher at Northwestern University Medical School who specializes in the evolution of HIV. But, he said, narrowing the window of cross-species infection could bring insights into how the virus quietly evolved before it became an explosive epidemic in the 1980s.
"Chances are that this was in the population for a long time, and then something made it really take hold," said Wolinsky, who co-wrote a 1998 paper that used a less sophisticated method to calculate that HIV emerged sometime in the first half of the 20th century.
The estimate of 1930 offers a new focus for African scholars studying the roots of HIV, said Jim Moore, an anthropologist at the University of California at San Diego.
"This directs us to what I think is the right time," Moore said.
Theories about the source of AIDS have abounded in the nearly 20 years since the disease was first recognized through its effects on American homosexual men. Reports in the mid-1980s that HIV had entered humans through African green monkeys soon proved false when genetic tests showed that the species' simian virus was not closely related to HIV.
More recently, the contention that HIV was accidentally passed to people in Africa during tests of an oral polio vaccine in the late 1950s gained weight with the publication last year of the book "The River" by British science writer Edward Hooper. The book documented that many early centers of the AIDS epidemic in central Africa had been polio vaccination sites years before, and that the vaccines might have been contaminated with viruses from primate tissue.
Debate over the issue shifted again at an HIV conference in Chicago last year. A team led by Hahn announced findings that the virus' most common form, Group M of the strain HIV-1, bore the closest genetic resemblance to a virus found naturally in the chimp subspecies Pan troglodytes troglodytes.
The report concluded the virus probably was transmitted to humans somewhere within that chimp subspecies' natural rain-forest habitat: a region that includes the west African nations of Gabon, Cameroon, and the Republic of Congo.
Yet until the recent date estimates, researchers have been at a loss to give a historical account of what might have brought people into increased contact with chimps in that part of Africa.
Efforts to time the epidemic's origin have relied on a huge computer database of HIV-1 samples maintained at the Los Alamos National Laboratory in New Mexico. Researchers use genetic sequences from the samples to calculate an evolutionary tree, which shows roughly when the ancestral virus of Group M would have existed.
Chimp-human infections may have posed a growing hazard in the first few decades of the 20th Century, some historians say.
The French colonial government that ruled west equatorial Africa then enacted a brutal policy of using forced labor for large construction projects, said Bruce Fetter, a social historian of colonial Africa at the University of Wisconsin at Milwaukee. By far the most infamous example was the Congo-Ocean railway, built between 1921 and 1934 in an area then called the French Congo.
More than 20,000 workers are thought to have died during the railway's construction, most from malnutrition. The nightmarish project became bogged down for years as it cut through sparsely inhabited rain forest near the west equatorial coast--prime habitat for Pan troglodytes troglodytes.
Lack of food may have driven the workers to desperate measures, Fetter said.
"If they were underfed, they might have gone off and trapped animals in the forest because they were hungry," Fetter said. "It was something they might not otherwise do."
Even more intriguing is the railroad's location near the earliest known case of HIV. The Congo-Ocean's eastern terminus in Brazzaville sits just across the river Congo from the city of Kinshasa, where the 1959 HIV-positive plasma sample was taken.
The early 20th Century also saw an increase in the capture of chimps from that part of Africa for use in zoos and circuses overseas, according to some researchers.
"Zoos really took off in (the U.S.) around the turn of the century," said Moore, the anthropologist. "It probably would have been the first time people were trying to capture chimps alive. And you're a lot more likely to get bitten by a live one."
Unsanitary vaccination campaigns by the French in central Africa in the early 1900s might have allowed HIV to take root. Moore points to evidence that one clinic used just six needles to immunize more than 89,000 people against sleeping sickness in 1916.
Other researchers see potential problems with the 1930 estimate for HIV's origins.
Preston Marx, a virologist at the Tulane University primate center in New Orleans, said he dates the virus' spread closer to 1950, when African nations began a sharp increase in vaccination programs using shared needles.
Different objections come from Edward Hooper, who has clashed with Hahn and other scientists over his theory that HIV spread through contaminated oral polio vaccines. In an interview, Hooper said it's unlikely HIV would have left no traces between an emergence around 1930 and the first known case in 1959.
For that to happen, Hooper said, the virus would have had to be "hidden in a village somewhere, cooking slowly and silently."
Hahn argued that the 1930 estimate "tends to weaken" Hooper's own theory, since the polio vaccinations in central Africa started only in 1957.
One point on which all of the researchers agree is the urgent need for more testing of African primates for viruses related to HIV. Such tests, Hahn said, could help settle the scientific debate while warning of possible new threats to humans.
"If anything, human contact with these species and potentially infected blood has increased rather than decreased in recent years," Hahn said.
