2 new antibodies may pave way for powerful AIDS vaccine

WASHINGTON - In what may be called the discovery of an Achilles heel on the AIDS virus, researchers have found two powerful new antibodies to HIV, called PG9 and PG16, that could ultimately lead to a powerful vaccine for the deadly disease.

Researchers associated with the International AIDS Vaccine Initiative (IAVI), at The Scripps Research Institute, and at the biotechnology companies Theraclone Sciences and Monogram Biosciences, made the breakthrough discovery, which they will use to craft novel approaches to designing an AIDS vaccine.

Moreover, the global collaboration and process that led to the discovery of the two new broadly neutralizing antibodies (bNAbs) are likely to produce more such antibodies, which may in turn reveal additional vulnerabilities of HIV, adding still more vitality to the effort to develop a vaccine against AIDS.

“The findings themselves are an exciting advance toward the goal of an effective AIDS vaccine because now we’ve got a new, potentially better target on HIV to focus our efforts for vaccine design. And having identified this one, we’re set up to find more, which should further accelerate global efforts in AIDS vaccine development,” said Wayne Koff, senior vice president of research and development at IAVI.

Broadly neutralizing antibodies to HIV are produced by a minority of HIV-infected individuals and are distinct from other antibodies to HIV because they neutralize a high percentage of the many types of HIV in circulation worldwide.

It is widely believed that to prevent HIV infection an AIDS vaccine would need to teach the body to produce these powerful antibodies before exposure to the virus.

Animal experiments have suggested that conceptually such a vaccine would work.

Before the discovery, only four antibodies to HIV had been discovered that were widely agreed to be broadly neutralizing.

The two newly discovered bNAbs-PG9 and PG16-are the first to have been identified in more than a decade and are the first to have been isolated from donors in developing countries, where the majority of new HIV infections occur.

Besides, previously identified bNAbs against HIV have functioned by binding to places on HIV that have proven difficult to exploit by means of vaccine design.

“These new antibodies, which are more potent than other antibodies described to date while maintaining great breadth, attach to a novel, and potentially more accessible site on HIV to facilitate vaccine design. So now we may have a better chance of designing a vaccine that will elicit such broadly neutralizing antibodies, which we think are key to successful vaccine development,” said Dennis Burton at Scripps.

The two new antibodies target a region of the viral spike used by HIV to infect cells.

The viral spike glycoproteins, termed gp120 and gp41, are highly variable and have evolved to thwart immune attack.

But biochemical studies suggest that PG9 and PG16 target regions of gp120 that do not change, which probably accounts for their breadth of neutralization.

Now researchers are planning to focus on studying the molecular structure of PG9 and PG16 and that of the region they target on the HIV spike.

They will use this information to try to devise immunogens-the active ingredients of vaccines-that elicit similar antibodies.

The study has been published in the journal Science. (ANI)