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(Ivanhoe Newswire) -- Last year, a study on an HIV vaccine was abruptly stopped after it was found to increase rather than prevent infection of the deadly disease. New information shows how the vaccine went awry.
Mercks STEP vaccine used a common cold virus to carry HIV pieces into the body. The pieces were supposed to help the immune system ward off later infection with the virus. Three years after the trial began, researchers discovered vaccine recipients who were previously immunized to adenoviruses were more likely to be infected with HIV.
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French researchers recently discovered antibodies produced during natural infections with the common cold may have changed the immune response to the HIV vaccine. Long-lasting Ad5 specific antibodies allowed HIV infection to spread three times faster than without them. The antibodies helped the vaccine enter antigen-presenting cells (APCs) immune cells. Once inside, the APCs activated T cells, which HIV prefers to infect.
The vaccine may have passed a phase I trial because it was tested in primates that dont naturally come into contact with human adenoviruses. The study was halted in its second phase.
SOURCE: Journal of Experimental Medicine, published online November 3, 2008
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