Hope rise on HIV/AIDS vaccine

Researchers have for the first time discover two powerful new antibodies to HIV that reveal what may prove to be the virus’ Achilles Heel.
The two newly-discovered HIV-specific antibodies (bNAbs), called PG9 and PG16, are the first to have been identified in over a decade and are the first to have been isolated from donors in developing countries, where the majority of new HIV infections are claimed to occur.
Previously identified bNAbs against HIV have functioned by binding to places on HIV that have proven difficult to exploit by means of vaccine design.
In fact, their identification represents the first success of an ongoing global hunt launched by international AIDS Vaccine Initiative (IAVI) in 2006 to find new HIV-specific antibodies (bNAbs) to support the rational design of novel AIDS vaccine candidates. The efforts, christened “Protocol G”, is unprecedented in scale and distinguished by its emphasis on identifying antibodies that neutralise subtypes of HIV circulating primarily in developing countries.
Until now, scientists were hampered in studying the way effective HIV-neutralising antibodies arise during natural HIV infection as they lacked the tools to obtain more than a few HIV-specific antibodies from any given individual.
Last month however, researchers experimentally induced antibodies that neutralise HIV-1 envelope protein and lipids . The results were reported by the united state (U.S.) military HIV research program (MHRP) researchers on August 25 in online version of AIDS, the official journal of the international AIDS society.
The researchers from IAVI, The Scripps Research Institute, and Theraclone sciences and Monogram Biosciences in the U.S., claimed in their work, expected to be published in the journal science, that the new-found vulnerability on the virus would be exploited by researchers in designing an AIDS vaccine.
Besides, they said the discovery of the two new broadly neutralising 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.’’ Said Wayne Koff, senior vice president of research and development at IAVI.
“And having identified this one, we’re set to find more, which should further accelerate global efforts in AIDS vaccine development,’’ he stated.
Broadly neutralising antibodies to HIV are produced by a minority of HIV-infected individuals and are distinct from other antibodies to HIV as they neutralise a high percentage of the many types of HIV in circulation worldwide.
It is 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 experiment suggests that conceptually, such a vaccine would work. Before this finding, only four antibodies to HIV had been discovered that were widely agreed to be broadly neutralising.
“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,” said Dennis Burton, professor of immunology and microbial science and scientific director of IAVI Neutralising Antibodies Centre at The Scripps Research Institute in La Jolla, California.
So, now we may have a better chance of designing a vaccine that will elicit such broadly neutralising antibodies, which we think are key to successful vaccine development,” he said.
Medical scientists confirmed that the breadth of neutralisation is very important in design of any effective vaccine.
According to them, any effective AIDS protection from a diverse range of the most prevalent types of HIV circulating worldwide.
The two new antibodies, according to the researchers, target a region of the viral spike used by HIV to infect cells.
The viral spike, glycoprotein’s, termed “gp120 and gp14”, are highly variable and have evolved to thwart immune attack. But biochemical studies suggest that PG9 and PG16 that do not change, which probably accounts for their breadth of neutralisation.
Researchers at IAVI-organised Neutralising Antibody Consortium (NAC), a scientific net-work focused on designing vaccine capable of eliciting broadly neutralising antibodies, said they will now turn their attention to studying the molecular structure of PG9 and PG16 and that of the region the target on the HIV spike. They will use this information to try to devise immuno-gens-the active ingredients of vaccine –that elicit similar antibodies.
The methods by which PG9 and PG16 were isolated are themselves proving instructive. IAVI clinical research partners have collected blood specimens from upward of 1,800 HIV infected volunteers from IAVI-supported clinical research centres in seven sub-Saharan countries as well as from centres in Thailand, Australia, the United Kingdom and United state.