Aug. 17, 2011 -- In the spring of 1997, then-president Bill Clinton called for an effective AIDS vaccine within a decade. Fourteen years and billions of research dollars later, a vaccine to prevent HIV infection remains an elusive goal.
International efforts to develop a useful HIV vaccine have proven disappointing, with failed clinical trials and dashed hopes. But a new study may represent an important break in the search.
Researchers with the Scripps Howard Research Institute and the International AIDS Vaccine Initiative (IAVI) have identified 17 new antibodies with broad activity against HIV.
Some of the antibodies are 10 times more potent than any that had previously been identified, and the hope is that they will turn out to be new targets for potential HIV vaccines.
The research appears today in the online issue of the journal Nature.
New Paths for AIDS Vaccine
Vaccines that target viruses work by training the immune system to recognize and kill invading viruses. They do this by exposing the body to a harmless form of the targeted virus.
The reason it has been so hard to develop a vaccine against HIV is that the virus mutates far more often than most other disease-causing pathogens.
“Unlike other viruses, like measles or polio, you can’t just make a weakened form because HIV is crafty enough that if you weaken it the virus figures out a way to return to its virulent form,” IAVI Chief Science Officer Wayne Koff, PhD, tells WebMD.
Although earlier research has identified the outer protein coating of the HIV virus as a major target of antibodies that inhibit infection, Koff says investigators had not previously identified the specific vulnerable sites on the protein to target with a vaccine.
Within a few years of infection most people who are HIV positive do not produce virus-targeting antibodies, but a minority of patients do.
By studying serum samples from HIV-infected people around the world, the researchers identified a select few who not only produced these antibodies, but who produced remarkably effective ones that neutralized a broad range of HIV subtypes at very low concentrations.
Antibodies Came From 4 Patients
The 17 new broadly neutralizing antibodies (bNAbs) identified by the research consortium were isolated from just four HIV-positive people.
“These people carried highly potent antibodies in their serum that were able to neutralize a large number of viruses,” study co-author Katie J. Doores, PhD, of the Scripps Research Institute tells WebMD.
The hope is that vaccine developers can use the new bNAbs to develop proteins that elicit the same broad response in the body to prevent infection with the HIV virus.
“We have accomplished major milestones, but obviously the last milestone is the hardest,” Koff says. “I would not want people to think that a vaccine is around the corner, but they ought to take away that it is feasible now and we have a rational path for moving forward.”
Vaccine Would Have Global Impact
Koff says even a partially effective HIV vaccine could have a major worldwide impact.
Each day, more than 7,000 people around the world are infected with the virus that causes AIDS. The IAVI estimates that a partially effective vaccine that works in just half of the people who get it, given to just 30% of the population would prevent 5.6 million new infections between 2015 and 2030.
Joseph P. McGowan, MD, of the North Shore University Hospital in Manhasset, N.Y., calls the new research exciting, but he adds that it remains to be seen if it will lead to an effective HIV vaccine.
McGowan is medical director of North Shore University Hospital’s Center for AIDS Research & Treatment.
“We’ve had a lot of setbacks, but there does appear to be something here,” he tells WebMD. “There are still major hurdles. I wouldn’t want people to get the idea that this will result in vaccine trials next week or next month.”
The Seattle-based biotech company Theraclone Sciences and San Francisco-based Monogram Biosciences Inc. contributed to the research