May 18, 2007
Scientists Report on Search for HIV Vaccine

Vaccines typically work by mimicking the effects of natural exposure to a specific microbe, which stimulates the immune system to recognize that microbe and protect the human body from it if it reappears. But current HIV vaccine candidates are not working that way, said top scientists at the National Institutes of Health. Instead, it appears that the HIV vaccine candidates developed so far simply reduce HIV levels in the body, thereby delaying the progression to AIDS and the need to start antiretroviral drugs, but not completely protecting against the virus. In a review article in the May 17 issue of the New England Journal of Medicine, Anthony Fauci and Margaret Johnston, who head HIV/AIDS research in the National Institutes of Health, noted that scientists have been thwarted in their efforts to develop a fully protective vaccine against HIV by the fact that the virus "is unusually well equipped to elude immune defenses." They explain that when HIV enters the body, it infects the crucial T-cells that would normally mediate an immune response, and from them spreads throughout the body, establishing HIV reservoirs in lymphatic tissue. Currently, several vaccines that induce primarily T-cell responses are in human clinical trials, but researchers are continuing to search for a vaccine that would actually produce antibodies and thereby prevent the establishment of HIV infection. "Clearing the virus before cells become latently infected remains the goal," Fauci and Johnston said. They noted, however, that there may be public health benefits from current vaccine candidates that appear to reduce viral levels in the body of someone infected with HIV, which may hold off progression to AIDS and make it less likely that an infected person will pass HIV on to others. The article, "An HIV Vaccine—Evolving Concepts," appears in the May 17, 2007, issue of the New England Journal of Medicine. http://thomas.loc.gov.