The AIDS virus evades the immune system because most of the proteins that cover the surface of the virus constantly change their structure, now researchers have identified a site that doesn't change, and shown how an antibody can bind to it.
Researchers of the U.S. National Institute of Allergy and Infectious Diseases reported their discovery in the latest issue of Nature published on Thursday.
The researchers said if the body could be stimulated to produce its own copies of this antibody before infection, then in theory, it would allow it to attack the otherwise elusive virus and prevent infection.
The discovery hinges on an HIV protein called gp120, which during infection latches onto a protein found in the human immune system called CD4.
Because this is an essential step in the virus's replication cycle, a key site within gp120 retains its conformation, unlike other HIV surface proteins, according to the researchers.
The discovery could be a significant step forward in the ongoing quest for a vaccine. "For a long time, people have been asking whether an HIV vaccine is even possible. What this finding says is that it's not just a dream -- there is this site of vulnerability," Peter Kwong of the Institute who led the research was quoted as saying.
Vaccine researchers previously thought that this site for antibody binding was hidden within the folds of the gp120 protein until the crucial moment of infection and this masking would mean that antibodies would not be able to recognize the unchanging portion and bind to it.
But Kwong and his colleagues have found this key part of gp120 are never hidden -- the protein doesn't change shape until after gp120 binds with CD4. This meaning means that the never-changing binding site is not locked away from antibodies after all.
The researchers have also succeeded in getting an antibody, called b12, to bind to gp120, and has studied the process to reveal the structure of the two molecules as they clamp together.
The b12 antibody is already known to protect monkeys from infection with the related simian immunodeficiency virus.