http://www.discover.com/jan_02/gthere.html?article=feat_aids.html
Were well-intended medical treatments ultimately responsible for the rise of the HIV virus? By Solana Pyne
More than a decade ago, field virologist Preston Marx traveled through Liberia and Sierra Leone searching for what he calls the missing epidemic. He hoped to pin down the origins of HIV2, one strain of the deadly virus that causes AIDS.
Theory held that all strains of HIV came from animal viruses that had naturally infected humans, so Marx, a professor of tropical medicine at the Tulane University Health Science Center in New Orleans, hunted for isolated HIV infections that had been caught from primate hosts. Instead, he uncovered a series of inconsistencies that have led him to believe that the transfer was not natural and that human activity has unknowingly created HIV. In a theory that is slowly gaining prominence, Marx argues that injection campaigns in the last century that were meant to treat infections also encouraged strains of SIV--the simian immunodeficiency virus--to mutate from a bug easily squashed by the human immune system to today's epidemic HIV strains. A Liberian girl holds her pet sooty mangabey, a species of primate that is the likely source of the virus that became HIV2. Photo by Preston Marx.
Marx's theory started with his work in the late 1980s, when he identified an SIV strain from a west African primate called the sooty mangabey as the likely ancestor of HIV2. Since people in western Africa both eat sooty mangabeys and keep them as pets, he figured that if this strain of the virus, called SIVsm, could jump to humans and mutate into HIV2, there must have been more than a single occurrence of this in people living with sooty mangabeys. "What I expected to find was little pockets of HIV2 spread from monkeys and causing mini epidemics," says Marx. "But I tested 10,000 people and found no missing epidemic."
He did find a handful of people infected with versions of SIVsm but not HIV2, and in most cases the infected person's immune system successfully fought the infection, so it was unable to spread from person to person. "I found no evidence you could catch AIDS from a monkey," he says.
In light of this discovery, Marx started to suspect that some external factor had helped SIVsm mutate into HIV2. The more he thought about it, the more unlikely it seemed that HIV strains arose out of a natural transfer from primates to humans.
If pockets of HIV existed in isolated African villages for centuries, he wondered, why hadn't the virus been brought to America by the slave trade, where there was a massive movement of people out of supposed HIV hot spots? If, on the other hand, the transfer of SIV to humans is so rare that it only happened in the last century, Marx found it very unlikely that this would have occurred successfully more than once. Yet around the time that SIVsm leapt from sooty mangabeys in west Africa, so-called SIVcpz spread from chimpanzees to humans in central Africa, becoming HIV1, the most deadly and widespread of HIV strains.
Marx began to look for links between human activities and the emergence of AIDS. The first documented, though initially undiagnosed, case of AIDS was a 25-year-old former sailor who died in Manchester, England, in 1959. HIV can take years to manifest as AIDS, so the man was likely infected in the early to mid-1950s. It was also in the 1950s that syringes became widely available, and injections were the preferred method for administering medicine. Upon discovering this correlation in timing, it occurred to Marx that widespread injections with reused, unsterilized needles might have been the Frankenstein that created HIV.
Marx's reasoning was similar to that of journalist Edward Hooper, author of The River. In the book, Hooper proposed that the first people with cases of AIDS were infected by SIV-contaminated batches of polio vaccine. The contamination could have occurred, he contended, if the polio vaccine had been derived from viruses grown in the kidney cells of SIV-infected chimpanzees. Studies of polio vaccine stocks have not supported Hooper's theory, but the circumstantial connections between the first AIDS cases and the sites of vaccination campaigns may bolster Marx's theory.
Marx proposes that when SIV infects humans, it begins to mutate, but the human immune system kills it off before it has mutated enough to be dangerous. This explains why most direct infections with SIV are not fatal or transmissible. If, however, a partially mutated pathogen is transferred from one person to another via an unsterilized needle, the virus gains time to mutate while its new host's immune system readies its defenses. After 5 or 10 such transmissions, the SIV strain might have mutated into an HIV strain.
And vast injection campaigns in the early 1950s could have done the job, Marx says. Between 1952 and 1957 the United Nations International Children's Emergency Fund administered over 12 million injections of penicillin to treat a common bacterial infection in central Africa, where all strains of HIV1 originated. It's also possible that smaller vaccination campaigns around the turn of the century might be the culprits.
Marx presented his theory at several meetings in the 1990s but began trying to get experimental evidence only after a chance meeting with epidemiologist Ernest Drucker four years ago. The two men were seated next to each other on an airplane and struck up a conversation. Marx began to outline his theory when he found out that Drucker, a doctor at Montefiore Medical Center and Albert Einstein College of Medicine in New York, studied the spread of HIV among intravenous drug users. That common interest in how HIV spreads led to a joint effort to prove Marx's hypothesis.
Their research is still in adolescent stages. Marx and Drucker, along with colleagues in Africa, are collecting blood samples and needles that have been used for injections and testing them for contaminating viruses. Injections are still used extensively to administer medication in much of Africa, and needle reuse remains a problem, so the scientists hope to find partially mutated SIV viruses moving from person to person via unsterilized needles. "We want to catch the virus in the act," Drucker said. "If it's true that it happened 50 years ago, it should be happening now."
With these studies Drucker and Marx hope to find out if SIV strains can contaminate syringes. In separate studies, they also plan to test how well the virus survives when it crosses species, by infecting other nonhuman primates with SIVsm. Once they have these answers, they hope to plug them into a computer model to determine if early injection campaigns could have created HIV.
For now, Marx's admits this is "just a theory." But if he's right, it could be a race against time to stop further epidemics, because Africa isn't the only country where injections with unsterilized needles are still very common, he says. "If this theory is correct, we are making new viruses for people."
— Posted 1/7/02
-------------------------------------------------------------------------------- RELATED WEB SITES: Drucker and Marx's viewpoint article "The injection century: massive unsterile injections and the emergence of human pathogens" in the journal Lancet (vol. 358, no. 9297) can be accessed at http://www.lancet.com/journal/vol358/iss9297/contents.
See Preston Marx's Web site for more information about his research and affiliations: http://www.drprestonmarx.com/.
For a brief synopsis of Ernest Drucker's research, visit http://www.aecom.yu.edu/home/cfar/ernest_drucker.htm.
A Tulane University article on Drucker and Marx's research can be found at http://www2.tulane.edu/article_news_details.cfm?ArticleID=3338.
This Centers for Disease Control site includes extensive information about HIV and AIDS on topics ranging from prevention and transmission of HIV to current and future scientific research: http://www.cdc.gov/hiv/pubs/facts.htm.
See more about the polio vaccine-AIDS connection debate in Nature's "The river without a paddle," by Tom Clarke, April 26, 2001: http://www.nature.com/nsu/010426/010426-12.html.
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