Item #51: HIV Does Not Kill Chimpanzees

It is claimed that although HIV does not kill the laboratory T-cells used to manufacture AIDS tests, it does kill T-cells in the human body, even though it infects only a very small proportion of them, typically an average of 0.1 percent. HIV does not sicken or kill chimpanzees, though they do produce antibodies. It was recently claimed that HIV appears to be evolving into a form less dangerous to human beings. Such unproven hypotheses about the ingenuity of HIV proliferate in the popular and scientific media like the seasonal flu. Seldom do journalists insist on good hard evidence for these assertions.

Farber further states in footnote 13 that “HIV does not sicken or kill chimpanzees”.

It is true that HIV replicates inefficiently in chimpanzees, to a much lower level than it does in humans so it usually does not cause disease. However, there are recorded examples of HIV causing immunodeficiency in these animals.78 , 79 Many agents which cause disease in man are unable to cause disease in a host of other species because they fail to infect, or infect poorly, or produce a different response. HIV has probably been in the chimpanzee population for a very long time. Therefore it is plausible that natural selection has rendered it less harmful. We note the presumably unintended irony in Farber's closing sentence in this footnote: "Seldom do journalists insist on good hard evidence for these assertions". In fact, most professional science writers do exactly that. Perhaps Farber will take the trouble to do so in the future.

In one study published in 2000, “10 HIV-1-positive chimpanzees were evaluated...All...had been inoculated with various isolates of HIV during the mid to late 1980’s...and all have been seropositive for more than 10 years (median, 13 years)...Chimpanzee C499 was euthanatized in 1996 following development of AIDS [disease(s) not specified]; however, all other animals remain healthy...[4 of the chimps have] experienced progressive reductions in CD2+/CD4+ T lymphocytes [immune cells believed to be targeted by HIV]. In contrast, the numbers of CD4+ T cells in the remaining 6 HIV-infected chimpanzees were similar to those of age-matched HIV-negative controls.” [1]
While it could be argued that this is proof that about 10% of chimpanzees are susceptible to AIDS, this assumes that there is no other reason for a decline in the immune system, such as being locked in a cage for more than 10 years.

<ol><li>O'Neil SP et al. Progressive infection in a subset of HIV-1-positive chimpanzees. J Infect Dis. 2000 Oct; 182: 1051-62.</ol>