4 April 2007

Modified Rabies Virus Could Tackle HIV

by Kate Melville

Scientists from Jefferson Medical College say they have produced viral immunity to an AIDS-like disease by using a weakened rabies virus to deliver HIV-related proteins into non-human primates.

The study, published in the Journal of Infectious Diseases, details how two years after the initial vaccination, four vaccinated rhesus macaques were still protected from disease, even after being "challenged" with a dangerous animal-human virus.

To test the effectiveness of rabies as a delivery vector, the scientists inserted two different viral proteins into the rabies virus genome. One was a glycoprotein on the surface of HIV, while the other was an internal protein from simian immunodeficiency virus (SIV). The modified rabies virus was the same one that has been used for more than 20 years in oral vaccines against rabies in wildlife in Europe.

Four rhesus macaques were immunized with both vaccines, while two animals received only the weakened rabies virus. After they gave the animals an initial vaccination, the researchers then tried two different immune system boosts, but didn't see enhanced immune responses. They then developed a new vector, a viral surface protein from another virus, vesicular stomatitis virus (VSV). Two years after the initial immunization, they gave a booster vaccine with the rabies-VSV vector, and saw SIV/HIV-specific immune responses.

Challenging the animals with SIV, the researchers found that those animals that were given the test vaccine could control the infection. The control animals without the experimental vaccine had high levels of virus and a loss of CD4 cells.

"We still need a vaccine that protects from HIV infection, but protecting against developing disease can be a very important step," researcher Martin Schnell said, adding that he and his colleagues aren't sure how long the viral immunity will last. But he did say this work was a proof of principle, and that future studies in larger groups of animals should be carried out.

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Source: Thomas Jefferson University