Origins of HIV and the AIDS Epidemic

September 11-12, 2000, The Royal Society, London, United Kingdom

Jonathan Weber, FRCP, FRCPath, FmedSci, Keith Alcorn, Medical Writer

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In This Article

Other Hypotheses About the Role of Western Science in the Origins of HIV

Preston Marx of Tulane Regional Primate Research Center noted that although the OPV hypothesis may in his view be fatally wounded, that does not exclude other iatrogenic possibilities. Marx presented his research into the potential role of nonsterile injecting equipment not only in spreading HIV, but in turning it into an aggressive human virus in the first place.

Marx began to be interested in this possibility after looking for human HIV-2 infection in West Africa that might be associated with sooty mangabey contact. These primates are the hosts of SIVsm, the ancestor of HIV-2, and Marx was surprised to find little evidence of SIVsm infection among the population. Only 2 of 9509 individuals tested in Sierra Leone were HIV-2-infected, despite no difficulty in finding SIVsm-infected mangabeys kept as household pets. Might HIV-2 be a relatively nonpathogenic infection, also difficult to transmit onward due to extremely low viral titer? Cohort evidence certainly suggests this is so, and that HIV-2 can incubate for upwards of 40 years without causing disease.

Had something occurred to amplify the virulence of HIV-1 after its transfer from chimpanzees? It is known that SIV becomes more aggressive if passaged through a new host, especially if the index case is experiencing primary infection. Might HIV-1 not do the same? And what would provide the most efficient means of passaging HIV through multiple hosts? This hypothesis is attractive at explaining how the adaptation of SIVcpz to a new host (humans) might have occurred rapidly, through sequential passage mediated by hypodermic needles.

Marx points to the massive increase in the use of antibiotics and injections in Africa during the 1950s. Before the Second World War, syringe use was limited because they were expensive and made from glass. Plastic syringes were introduced in 1959, when their cost dropped up to 100-fold, and the use of penicillin and choloroquine became more common in Africa. Re-use of syringes was so commonplace as to be unremarkable and continues to this day. Marx pointed out that "if we are correct about this, ...we will continue to get new strains. It could wreck vaccine research."

Charles Gilks of Liverpool University School of Tropical Medicine noted that the extremely high prevalence of hepatitis C in Egypt is directly attributable to injectable treatments used to combat schistosomiasis in mass campaigns during the 1950s. He also pointed out that human/chimpanzee contact accelerated hugely in the 20th century driven by the imperatives of medical and scientific research. Chimps were used in malaria experiments because it was noted that they carried 3 of 4 of the malaria parasite species that affected humans. Doctors are known to have injected themselves with blood from malarial chimps in the 1930s, and subsequent experiments included the injection of chimp blood into 20 individuals in Antwerp and prisoners in the United States. It was feared at the time that if malaria was eradicated by measures such as DDT spraying in the developing world, chimps might serve as a reservoir for renewed human exposure.

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