HIV VACCINE TRIAL BEGINS IN SOUTH AFRICA

The HIV Vaccine Trials Network (HVTN) has announced the launch of the first large-scale study to evaluate a candidate HIV vaccine in South Africa. The trial will involve up to 3,000 participants at five centers and is expected to continue for four years.

The HVTN is supported by the U.S. NIH, as well as the South African AIDS Vaccine Initiative.

"This trial will answer several major scientific issues that face all of us in the field of HIV-vaccine development," Lawrence Corey, the trial's principal investigator, said. "It will determine the usefulness of vaccines that induce high immune response to the parts of the virus that are similar between different strains of HIV-1."

The Phase IIb study will enable researchers to determine whether the vaccine prevents HIV infection, results in lower HIV levels in those who become infected, or both. In addition, investigators will determine if this vaccine, which is based on clade B HIV, has the potential to protect against the clade C virus, the subtype prevalent in South Africa.

The test vaccine, known as the MRKAd5 HIV-1 trivalent vaccine, is manufactured by Merck and has already been studied for several years in Phase I and II trials involving thousands of volunteers in the U.S., Africa and Australia. In those previous trials this vaccine was found to be safe and to stimulate cellular immune responses against HIV in more than half of volunteers.

The vaccine is based on an adenovirus -- a common cold virus that has been modified so that it cannot cause a cold in humans or be passed from person to person. The adenovirus is the carrier or vector that transports copies of three HIV genes called gag, pol and nef. The vaccine does not contain live HIV and therefore cannot cause infection.