The trial is co-funded by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), and the pharmaceutical company Merck & Co. Inc. Merck developed the experimental vaccine to stimulate HIV-specific cellular immunity, which prompts the body to produce T cells that kill HIV-infected cells. In previous smaller trials, this vaccine was found to be safe and to induce cellular immune responses against HIV in more than half of volunteers.

"This new study is the first time we have used such a large sample of people to test whether a vaccine that stimulates cellular immunity alone either blocks HIV infection, decreases the level of HIV early in infection or both," says Anthony S. Fauci, M.D., director of NIAID.

This proof-of-concept trial is designed to yield vital information on the potential efficacy of cellular immunity against HIV, although it is not expected to provide enough data to support immediate licensing of the vaccine for public use, says Margaret (Peggy) Johnston, Ph.D., who oversees HIV vaccine research at NIAID's Division of AIDS.

The Merck vaccine contains a weakened adenovirus that serves as a carrier for three subtype B HIV genes. Subtype B is the most prevalent HIV subtype in the regions of the study sites. Adenoviruses are among the main causes of upper respiratory tract ailments such as the common cold. Because the vaccine contains only three HIV genes housed in a weakened adenovirus, study participants cannot become infected with HIV or get a respiratory infection from the vaccine.

"If this study finds that the vaccine can prevent or control infection, we will work with Merck to evaluate the vaccine in a larger number of volunteers," adds Dr. Johnston. "We will al
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Contact: NIAID News Office
niaidnews@niaid.nih.gov
301-402-1663
NIH/National Institute of Allergy and Infectious Diseases
24-Jan-2005