New research -- funded and coordinated by the International AIDS Vaccine Initiative -- has discovered two antibodies that help prevent HIV from replicating and thus prevent it from causing AIDS. The research is exciting because the antibodies bind to a relatively stable portion of the virus (versus other areas that rapidly mutate), making it an ideal candidate for therapy and vaccine development.
To find the neutralizing antibodies, researchers collected blood samples from more than 1,800 people in Thailand, Australia and Africa who had been infected with HIV for at least three years without the infection proceeding to severe disease. Such individuals are most likely to produce antibodies that interfere with the replication of the virus.
Researchers at Monogram Biosciences in South San Francisco studied the samples most resistant to infection, then a team from Theraclone Sciences in Seattle isolated the antibodies responsible for the resistance.
They ultimately isolated two antibodies, called PG9 and PG16, from one African patient. The antibodies were able to block the activity of about three-quarters of the 162 separate strains of HIV they tested it against.
Immunologist Dennis Burton of Scripps and his colleagues then showed that the antibodies bind to regions of two proteins on the surface of the virus, called gp120 and gp41, that help the virus invade cells. These regions had never before been considered as targets for vaccines.
Researchers still have a long way to go to produce a vaccine, however.
The antibodies themselves could potentially be used as a treatment for infected patients who develop severe disease.
But the long-term hope is to find molecules, either synthetic or natural, that can stimulate the body to produce the broadly neutralizing antibodies. Such molecules could potentially be the basis for a successful vaccine.
