Vaccine candidate successful in blocking Simian version of HIV

May 18 2009

Researchers have successfully blocked SIV, the simian version of HIV, using a new technique that could help lead to the development of an effective HIV/AIDS vaccine, the . The team also included scientists from Nationwide Children's Hospital in Columbus, Ohio, and the New England Primate Research Center in Boston.

Johnson and colleagues developed a genetically altered virus that carried the vaccine candidate and injected it into the muscles of monkeys. The vaccine prompted the muscles to produce a protein that is designed to bind to SIV and prevent it from infecting cells (Goldstein, Philadelphia Inquirer, 5/18). After treating nine monkeys with the vaccine candidate for one month, the researchers injected them with SIV. Six monkeys were not administered the vaccine candidate before being injected with SIV. None of the immunized monkeys developed AIDS, while three showed indications of SIV infection. Researchers detected high concentrations of the proteins in their blood one year later. All six non-immunized monkeys became infected with SIV, and four died during the trial (Schmid, AP/Austin American-Statesman, 5/18). The DNA used in the carrier virus can deliver DNA into the cells of both monkeys and humans, according to the Inquirer.

Johnson said that the results of the trials were so encouraging that he plans to request approval from FDA to begin clinical trials in humans, the Inquirer reports. However, he said that there is "no guarantee that things that work in monkeys will work in humans," adding that an HIV/AIDS vaccine could be 10 years away (Philadelphia Inquirer, 5/18). Recent HIV/AIDS vaccine failures prompted the researchers to try a different route that involved "bypassing the natural immune system that was the target of all previous HIV and SIV vaccines candidates," Johnson said. "Some years ago I came to the conclusion that HIV was different from other viruses ... and we might not ever be able to use traditional approaches," he added (AP/Austin American-Statesman, 5/18).

Peggy Johnson -- head of the HIV Vaccine Research Branch at NIH's National Institute of Allergy and Infectious Diseases, which helped fund the study -- said, "As a concept, I think this is very promising." She added, "We need to make the genes as humanized as possible so that the human body doesn't react to that." According to Peggy Johnson, tests will be needed to prove that the vaccine candidate can protect against sexually acquired HIV (Fox, Reuters, 5/17). Beatrice Hahn, an HIV/AIDS researcher with the University of Alabama-Birmingham, said that the study's findings indicate that there is "a light at the end of the tunnel," adding, "It shows thinking outside the box is a good idea and can yield results, and we need perhaps more of these nonconventional approaches" (AP/Austin American-Statesman, 5/18).

Hildegund Ertl, a virus expert at the Wistar Institute in Philadelphia, said, "It is a very innovative approach but currently, in my mind, still far from clinical use." Ertl added that because most people have been exposed to adeno-associated viruses through cold viruses, they would be "likely to mount an immune response" to the vaccine. According to Phillip Johnson, most people have not been exposed to the strain of the adeno-associated virus that the researchers used as the carrier. He added that they "will be certainly looking at that as part of our Phase I testing in humans" (Philadelphia Inquirer, 5/18).