Hope For AIDS Vaccine

In a significant discovery, scientists may have found the most potent weapon till date to combat HIV. Bringing hope to the idea of developing an effective vaccine against the deadly virus, scientists have discovered two highly powerful new antibodies that neutralised all major forms of the virus from the body of an African man.

An antibody is an infection-fighting protein produced by our immune system when it detects harmful substances like viruses and bacteria.

Interestingly, this African man is part of a select community on this planet who are infected with HIV but show no symptoms or deterioration of health, thanks to these antibodies.

Scientists associated with the International AIDS Vaccine Initiative (IAVI) at the Scripps Research Institute in the US said these antibodies had also revealed an Achilles heel on the virus.

This major discovery, reported in the journal Science on Friday, also found that these two antibodies target a stable portion of the virus that does not frequently mutate a defence mechanism that has till now helped the virus escape earlier developed experimental vaccines.

Experts will now look at exactly where the antibodies bind to the virus. This will tell them which part of the virus to target with vaccines.

The team of scientists which made the discovery said they also identified what genes the donor's body used to build the neutralising antibodies.

Researchers believe they can create an effective vaccine if they are able to get the human body to produce such neutralising antibodies before exposure to HIV.

Since HIV was first identified in 1981, 40 million people have been infected with the virus. Annually, an estimated 4 million new infections occur, of which 90% are in developing countries. Over the last 25 years, AIDS has claimed more than 25 million lives.

"These HIV neutralising antibodies are produced naturally by a minority of people infected with HIV but who show no symptoms. This finding is an exciting advance towards 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 VP of research and development at IAVI.

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.

To find the neutralising antibodies, researchers collected blood samples from more than 1,800 people in Thailand, Australia and Africa who had been infected with HIV for at least three years without the infection proceeding to severe disease.

They ultimately isolated two antibodies, PG9 and PG16, from an African patient. The antibodies were able to block the activity of about three-quarters of the 162 separate strains of HIV they tested it against.

Before this finding, only four antibodies to HIV had been discovered.

However, contrary to the latest antibodies found (PG9 and PG16), the previously discovered antibodies functioned by binding to places on the HIV that have proven difficult to exploit by means of vaccine design.

"These new antibodies, which are more potent than other antibodies discovered to date, attach to a novel and potentially more accessible site on HIV to facilitate vaccine design," said Dennis Burton, professor of immunology at the Scripps Research Institute.

It's been over two decades since scientists have been making futile attempts to develop a vaccine against HIV. Two large trials of experimental vaccines have failed till now, the most recent in 2007.