Researchers find promising target for AIDS vaccine

According to research by scientists at the Dana-Farber Cancer Institute, a section of the protein envelope of the AIDS virus once believed to be an unlikely target for a vaccine may be one of the most promising.

The section, called the V3 loop, is a twisting strand of protein that is an attractive vaccine target because immune system antibodies aimed at the loop could offer protection against multiple HIV-1 genetic subtypes. Offering protection against different subtypes is key because of how rapidly the viruses mutate.

The investigators injected a monoclonal antibody - a preparation of millions of identical virus fighting antibodies - into Asian monkeys called macaques. The antibody was from a person infected with a specific clade or particular genetic subtype. The macaques were then exposed to a virus from a different clade, which protected all the treated monkeys from infection from the monkey form of HIV-1. All of the exposed monkeys without the antibody were heavily infected.

"This is the first time a monoclonal antibody made against an AIDS virus of one clade has provided complete protection against an AIDS virus of a different clade in animal models," Ruth Reprecht, the study’s senior author, said. "Previous studies have shown that such neutralizing antibodies can protect macaques from infection within one clade; but as more clades of the AIDS virus evolve, it has been unclear whether such antibodies could shield across different clades and prevent infection. Now we have an answer."

The study has provided some vindication for the V3 loop as a target for the immune system as many scientists have thought the protein strand was a decoy due to its rapid mutation. The researchers hope to find a way to focus the body’s immune system responses to the small portion of the V3 loop that is shared by viruses of different clades. This would enable the body to generate its own protective antibodies to fight the virus.