WASHINGTON, DC - Attempts to unravel how a vaccine against the monkey version of the AIDS virus actually works led to renewed calls for testing a similar - but potentially risky - vaccine in humans. The findings were reported here at the 4th Conference on Retroviruses and Opportunistic Infections.
thereAbout 5 years primate researcher Ronald Desrosiers, New England Regional Primate Research Center of Harvard reported that he and his colleagues have developed a manufactured vaccine from weakened SIV, the simian cousin of HIV . This virus "attenuated" did not itself cause disease in monkeys, and it protected the animals from huge doses of virulent strains of SIV.
To unravel how the vaccine worked, the team bled Desrosiers monkeys immunized with SIV attenuated vaccine and purified antibodies which were found in their blood. They injected the antibodies into two monkeys that did not receive the vaccine. As a control, two monkeys received a generic antibody preparation and two others received antibodies in test tube studies can prevent infection with virulent SIV. Three hours after the infusion of six animals with these various preparations, the researchers injected the monkeys with virulent SIV. In a few weeks, all six were infected
Desrosiers concluded that the vaccine does not work with the most obvious mechanism :. Stimulate the immune system to produce antibodies that can then block the virus before it infects cells. "The antibodies do not seem sufficient to confer the protection afforded by the [attenuated vaccine]," said Desrosiers. So what could be the protection of apes? AIDS researchers believe the vaccine may trigger immune killer cells to destroy cells infected with HIV or stimulate production of immune system messengers called chemokines that can block a receptor used by SIV to enter the cell and establish an infection.
Because of the difficulty of determining why the vaccine works, Desrosiers and several researchers argue that a weaker version should simply be tested in people. they point out that most vaccines against other pathogens moved in clinical trials before researchers understood how they worked. But others argue that the weakening of HIV, when injected into a person, could mutate into a virulent form and cause AIDS. The fact that HIV integrates into the host cell DNA also poses the risk of triggering cancer. "The scientific leadership was really against the idea of moving forward with this vaccine," said John Sullivan pediatrician from the University of Massachusetts, Worcester, yesterday morning in a presentation. However, he said, "it is important for the scientific community to start lobbying for it."
Sullivan noted that one of his patients and seven other recipients of blood transfusions infected with the same bad lot of blood in Australia are infected with attenuated strains of HIV that resemble designed vaccine Desrosiers. These people, Sullivan said, never showed symptoms of AIDS. He suggested that 10 or so patients a terminal illness with less than a year to live could be invited to volunteer to be vaccinated against the attenuated HIV.
at least one prominent group is hoping to advance strategy mitigated closer to human trials. the International AIDS Vaccine Initiative, sponsored by the Rockefeller Foundation, recently announced that it is interested in funding further work on the approach to assess the risks and potential benefits.
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