Antibodies stir hopes for HIV vaccine

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iol scitech march 4 Caprisa head INDEPENDENT NEWSPAPERS File photo: Leader of the Caprisa team, Durban-born Professor Salim Abdool Karim. Picture: Jennifer Bruce

Durban - The blood of a rural KwaZulu-Natal woman has helped scientists achieve a breakthrough in their quest to prevent and treat HIV infection.

A team of South African and US researchers have discovered how to clone potent antibodies in the woman’s blood, which her body had produced in response to the virus.

The broadly neutralising antibodies were able to kill multiple strains of HIV from across the world, the scientists from the Centre for the Aids Programme of Research in SA (Caprisa) announced on Monday.

Caprisa brings together scientists from the National Institute of Communicable Diseases, and the universities of the Witwatersrand, Cape Town and Colombia.

The woman has so far only been identified as Caprisa 256 or Cap256.

In explaining the significance of the discovery, the leader of the Caprisa team, Durban-born Professor Salim Abdool Karim, said that he had not been this excited for some time.

“The big difference is that for the first time, we have not just studied the antibodies, but have been able to make them in the laboratory. We could never clone them before,” said Karim, who is also the president of the SA Medical Research Council.

He said that it was a “breakthrough, albeit a small one”.

“The are many hurdles on the way to making the vaccine. What we have overcome is one small hurdle. There will be many more to overcome. But this is new knowledge. In our society we don’t quite grasp what it means to make new knowledge.”

The discovery was described in a study published in the international scientific journal Nature.

Karim explained that Cap256, who became infected nearly four years ago, had produced a very unusual antibody.

The human immunodeficiency virus had a very large shield of sugar on its outer covering which prevented antibodies from reaching the surface to kill the virus. But the woman’s antibodies had “long arms” that reached through the sugar shield.

Unfortunately, because these antibodies took several weeks to develop in response to the virus, and because the virus continuously evolved in the body, the antibodies were unable to kill the HIV in her own body.

“HIV is able to evade the body’s immune response,” Karim said.

“So just think about it, any time the body encounters a virus or bacterium it is able to respond, it responds with these different cells, it responds with these antibodies, these soldiers in the body.

“HIV is able to bypass and hide from these soldiers, and the way it does so is through a sort of camouflage. And this camouflage, this shield which hides it, is a shield of sugar. The body is not able to identify that underneath this sugar there is this foreign virus.

“In this particular woman, her body was able to overcome that problem. Her body was able to produce soldiers with these long arms which could reach through the shield and get to the protein and get to the actual virus.”

Karim said the scientists had made a few milligrams of antibodies, and the next step was to manufacture enough to see if it could prevent the equivalent of HIV in monkeys.

“It’s going to take us another four to six months to make enough and another year to undertake the animal study. In 18 to 24 months from now we will have enough information to make a decision as to whether we’re ready to proceed to human studies.”

The government has heaped praise on the scientists and on Karim, with Health Minister Aaron Motsoaledi saying that he was hopeful that the new research had brought the world a step closer to bringing an end to Aids. - The Mercury

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