AIDS VACCINE: Researchers Turn to SIV to Elucidate How HIV Evades the Immune System

Scientists have discovered that SIV, the "monkey version" of HIV, self-mutates during the first few weeks of entering a host's body, enabling it to evade the human immune response. The research, carried out by University of Wisconsin researchers and published in this week's Nature, was performed on 18 rhesus macaque monkeys. Researchers found that four weeks after they exposed the monkeys to SIV, the version of the virus in the monkeys' bloodstream had mutated from the original strain. The genetic mutation was linked to the Tat protein, and "provided enough disguise to enable the virus to escape immune attack." Tat is a functional protein that is required for the virus to replicate (NIH release, 9/20). When monkeys are first infected with SIV, they produce a powerful anti-SIV immune response targeted at Tat. Once the Tat gene mutates, it creates a form of Tat that killer T cells are no longer able to recognize, and thus are powerless against the virus. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, which funded the research, said, "The results suggest that using vaccines that stimulate immune responses against virus proteins produced within a few hours after infection, such as Tat, may help control HIV" (Garrett, Newsday, 9/21). He added, "These animal studies open the window on immune events in early HIV infection and provide a rationale for exploring a new approach to designing HIV vaccines." Peggy Johnston, NIAID's assistant director for AIDS vaccines and associate director of the Vaccine and Prevention Research Program in the Institute's Division of AIDS, said, "If ongoing work by these investigators shows that vaccinating monkeys with SIV Tat induces a massive killer T cell response that can prevent infection or substantially reduce the amount of virus in monkeys, research on HIV vaccines that incorporate similar targets will be stimulated" (NIH release, 9/20). Scientists are increasingly turning to monkeys to learn more about HIV. Researchers at Atlanta, Ga.-based Emory University are currently investigating HIV-infected chimpanzees, which can naturally impede HIV's progression to AIDS. Dr. Shawn O'Neil explained that "understanding why HIV-infected chimps do not get sick could help researchers in developing an HIV vaccine and possibly in preventing HIV-positive people from progressing to AIDS" (Norton, Reuters Health, 9/20). Chimp 'Reward' Meanwhile, the Senate Health Education, Labor and Pensions Committee has agreed to allocate $30 million to build a "rest home" for aged and ailing chimps who have participated in scientific research at the NIH and other laboratories. The facility "rewards" chimps for serving as medical subjects and provides a sanctuary with "humane conditions," in which chimps can enjoy their final years (CongressDaily/A.M., 9/21).