AIDS researchers have discovered two highly potent and unique antibodies that can neutralize more than 100 strains of HIV, one of the most promising preliminary breakthroughs in more than a decade in the elusive quest to produce an effective AIDS vaccine.
The discovery marks the first time in years that researchers have identified and isolated proteins known as “broadly neutralizing antibodies,” which have the ability to block numerous forms of HIV by targeting parts of the highly-mutable virus that do not change.
Antibodies are protein molecules produced by the body to fight infection. They bind to the specific antigen – bacteria, viruses or other foreign substances – that provoked the immune response.
The two newly discovered broadly-neutralizing antibodies are extremely unique because they appear adept at exploiting vulnerabilities in a wide range of HIV strains. They're also more potent than any previously discovered broadly-neutralizing antibody, which may be because they target regions of HIV that don't change when the virus mutates.
“This is kind of opening up a whole new area of science,” said Seth Berkley, president, chief executive officer and founder of the International AIDS Vaccine Initiative (IAVI), whose headquarters are in New York.
The research, published online today in Science, was developed by IAVI, the Scripps Research Institute and biotechnology companies Theraclone Sciences and Monogram Biosciences.
Dr. Berkley said scientists have long believed that broadly-neutralizing antibodies – which he refers to as the “Holy Grail” of AIDS vaccine development – are key because they guard against many strains, a critical factor when battling the most mutable virus known to humankind. Although some of these antibodies have been discovered before, they targeted parts of the HIV virus that were difficult to exploit for vaccine production.
The new antibodies, however, bind to an ideal spot, which is giving the researchers involved hope that this may represent the breakthrough everyone has been looking for.
It's also the first time broadly-neutralizing antibodies were found in infected individuals living in developing countries. In the past, researchers discovered broadly-neutralizing antibodies in North Americans, but they weren't able to use them to make a vaccine. By turning their attention to Africa and other developing countries, where strains of HIV typically have different forms than they do in North America, researchers were hoping to find new antibodies that could neutralize the strains of HIV where infection rates are highest.
If scientists can use those unique antibodies – which are produced only by a small number of HIV-infected individuals – to develop an immunogen, the active ingredient of vaccines, they believe it will trigger an immune response that can protect against numerous forms of the highly mutable virus before infection.
But that's the key word: if.
While the discovery of the antibodies represents an important breakthrough, the next steps will be a formidable challenge. No one has ever successfully developed an immunogen for an AIDS vaccine and there have been many disappointments in the past. In 2007, a trial of one of the most promising experimental AIDS vaccines, led by Merck & Co., was halted after it failed to show any results and appeared to increase the likelihood of HIV infection.
Despite the enormity of the challenge, Dr. Berkley said he is optimistic that, with time, researchers will be able to understand the molecular structure of the newly discovered antibodies to devise an immunogen.
“We have to trust science to be able to solve it,” Dr. Berkley said.
In addition, the discovery of two new antibodies provides realistic hope scientists will be able to discover more of them, providing new avenues to explore.
One of Canada's leading AIDS researchers, Stanley Read, chair of the scientific advisory committee at the Canadian National Foundation for AIDS Research, said in an e-mail that the results are “promising with respect to the potential for vaccine development,” but that he's also cautious about getting too excited just yet.
