Researchers in France reported Tuesday that they've discovered a way in a laboratory setting to stimulate immune system antibodies to widely recognize and target HIV, the first time such a success has been achieved against a broad genetic range of the virus, Agence France-Presse reports. The discovery could be an important step in the development of a protective vaccine against HIV, the scientists say.
Antibodies are the first line of defense in the body's immune system. The molecules are programmed to recognize and destroy specific viruses and bacteria that invade the body to prevent infection. Many vaccines--including those against the flu, polio, and measles--work by priming antibodies to prevent those pathogens from taking hold in the body. But attempts to stimulate an antibody attack against HIV have so far been a major disappointment for AIDS researchers. One of the reasons many scientists think it has been so difficult to stimulate an antibody attack against HIV is because it mutates often, slightly changing its genetic structure so that any anti-HIV antibodies developed in the body no longer recognize and attack the virus. The various subtypes of the virus around the world also are all slightly genetically different from one another, further hampering efforts to develop an antibody-based vaccine.
The French scientists focused their efforts on stimulating antibodies to target a tiny area of a surface protein that they say remains unchanged across the range of various HIV subtypes. The area is called CBD1 and is part of HIV's key gp41 protein. The researchers developed a chain of synthetic peptides mirroring CBD1 that can be used to prime antibodies to recognize and attack that portion of the virus. Lab experiments on rabbits immunized with the synthetic peptides showed that CD4 cells taken from the animals were protected from infection against a range of HIV subtypes. "The anti-CBD1 antibodies work in two ways," the researchers said in a statement. "Firstly, they inhibit cellular infection by HIV, and secondly, among cells that are already infected, they lead to the production of defective viruses which are unable to infect other cells."
The researchers hope their discovery will pave the way for a human vaccine that will prevent HIV infections. So far, only lab and animal tests have been conducted, but human safety and efficacy studies are planned, they say.
Their full study appears in the November 16 edition of the journal Immunity.