US researchers reveal why so many antibodies fail to protect against HIV infection

Researchers have been stymied for years over the fact that people infected with the AIDS virus do indeed produce antibodies in response to the pathogen - antibodies that turn out to be ineffective in blocking infection. Now, scientists at Duke University Medical Center, USA, can explain why: Some of the earliest and most abundant antibodies available to fight HIV can't actually "see" the virus until after it's already invaded a healthy cell.

The scientists based their conclusion on the results of a series of crystallography and biochemical experiments that revealed the specific molecular structures different types of antibodies need to have in place in order for them to mount an effective defense. The study was funded by a Collaboration for AIDS Vaccine Discovery Grant from the Bill & Melinda Gates Foundation.

Previous research had shown that two of the most robust antibodies against HIV - antibodies called 2F5 and 4E10 - target a specific part of the outer coating of the virus called the MPER region of gp41. The antibodies, which operate in a lock and key relationship, are able to latch on to the virus as it reveals this vulnerable part of its structure, referred to as an "Achilles heel" of the AIDS virus.