22 August 2011

Broadly effective antibodies against HIV isolated

by Kate Melville

Researchers working under the auspices of the International AIDS Vaccine Initiative (IAVI) have reported the isolation of 17 novel antibodies capable of neutralizing a broad spectrum of variants of HIV. Founded in 1996, The IAVI is a global not-for-profit organization whose mission is to ensure the development of safe, effective, accessible, preventive HIV vaccines for use throughout the world.

The new broadly neutralizing antibodies (bNAbs), isolated from four HIV-positive individuals, are large protein molecules that bind to pathogens and flag them for destruction. Some of the new bNAbs blocked HIV infection of cells as much as 10 to 100 times as potently as previously discovered bNAbs.

"Most antiviral vaccines depend on stimulating the antibody response to work effectively," said Dennis Burton, director of the IAVI Neutralizing Antibody Center at The Scripps Research Institute. "Because of HIV's remarkable variability, an effective HIV vaccine will probably have to elicit broadly neutralizing antibodies. This is why we expect that these new antibodies will prove to be valuable assets to the field of AIDS vaccine research."

Previous animal studies have suggested that bNAbs could block HIV infection if they were elicited by a preventive vaccine. Researchers expect that they can use information about how bNAbs bind to HIV to construct immunogens - the active ingredients of vaccines - that elicit similar antibodies. The potency of bNAbs matter because a highly potent antibody could confer such protection at relatively low levels.

In that regard, the new bNAbs are very promising as many of them bind hitherto unknown molecular structures on the surface of HIV. This means that they could significantly broaden the target options researchers have in designing vaccines to elicit similar antibodies.

Analysis of the new antibodies also offers some clues as to how future vaccines ought to be formulated to maximize their effectiveness. The authors of the report conclude that AIDS vaccine candidates that seek to effectively harness the antibody response should probably attempt to elicit certain combinations of bNAbs if they are to provide truly comprehensive protection from HIV.

"Solving the neutralizing antibody problem is perhaps the greatest challenge facing the field today," said IAVI's chief scientific officer, Wayne Koff. "IAVI concluded many years ago that unlocking the information stored in bNAbs was going to be essential to the fulfillment of our mission - ensuring the design and development of broadly effective AIDS vaccines. We have no doubt that these new bNAbs will contribute a great deal to our own immunogen design efforts and, we hope, those of other researchers working on AIDS vaccines."

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Source: International AIDS Vaccine Initiative