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10 Kenyans hold the key to HIV vaccine

Posted by African Press International on September 25, 2008

Prof Walter Jaoko, left, with Prof Omu Anzala at their laboratories at the Kenya Aids Vaccine Initiative. Behind is a lab technician. Photo / ARTHUR OKWEMBA


In Summary

  • The 10 have not been attacked by opportunistic infections despite not being on antiretrovirals.
  • Those screened so far have an immune system able to elicit antibodies.

Ten Kenyans found to carry powerful antibodies that neutralise HIV, stopping it from infecting new cells, may hold the key to developing a vaccine according to researchers at the Kenya Aids Vaccine Initiative.

On being screened, the individuals were found to possess high CD4 count immune cells used to fight infections and very low viral loads amount of HIV in the body which is uncharacteristic with an infected person.

The 10 have not been attacked by opportunistic infections despite not being on antiretrovirals.

The 10 individuals are now being followed to establish who among them qualify to be what scientists refer to as Elite Controllers individuals who are able to control HIV viral load to less than 50 copies compared to over 30,000 copies of HIV in a person without such antibodies.

This new phenomenon is being seen in both men and women who we have screened in Nairobi, and we are keenly following them to identify the key antibodies that make them tick, says Prof Omu Anzala, the director Kenya Aids Vaccine Initiative.

Disclosing the findings to Horizons, Prof Anzala said those screened so far have an immune system able to elicit antibodies CD4 and CD8 with a unique protein that target specific sites of HIV stopping it from infecting new cells.

In Africa, of the 1,700 HIV positive people who been screened in the past one year, 170 have HIV neutralising antibodies. Kenya, Uganda, Rwanda, South Africa, and Zambia, are some of those marked to help in studying this phenomenon.

What we are experiencing now is phenomenal and provides critical information of how we move forward and the massive work we need to undertake in this direction, says Dr Wayne Koff of International Aids Vaccine Initiative (IAVI).

In interview with Horizons, Wayne said they have managed to identify four antibodies with ability to neutralise the virus and are currently studying them to see which ones are broadly neutralising those with ability to neutralise different types of HIV strains such as A, B, C and D.

In this quest, they are also paying particular attention to immune systems of individuals who have lived with HIV for the past three years without using ARVs. Some of them are believed to possess the neutralising antibodies.


Buoyed by these new findings, IAVI is going to set aside between 30 and 50 per cent of its budget trying to develop e a new vaccine based on the new findings, according to Dr Koff.

Likewise, IAVI has developed what they call Protocol G, whose sole objective is to help scientists identify elite controllers across Africa and other parts of the world.

Identifying the broadly neutralising antibodies and then using the knowledge to develop a vaccine to produce similar responses in HIV negative individuals has been the most difficult thing for scientists. It has taken them over 10 years to just understand this phenomenon well.

Speaking recently in Nairobi to a group of scientists from Africa, Dr Koff admitted that, as a field we have not understood as yet how to elicit broadly neutralising antibodies to tackle HIV.

But now, adds an optimistic Prof Anzala, we are on the path to somewhere and we can see light at the end of the tunnel.


Still, there other challenges even with the new discovery. The four neutralising antibodies identified so far work on just one site of HIV, while ideally they should do so from various points so as to be able to disable it effectively. Consequently, the search is now on to find other antibodies that work on different sites of the virus.

Discovery of these antibodies will help the scientists develop a vaccine with the ability to disable a wide range of HIV strains such as A, C, and D, which are circulating in Kenya.

As for now, the four antibodies discovered are crucial since unlike the cellular immune response that destroys a cell once infected and on which past vaccines have been developed; the neutralising antibodies are able to prevent the virus from infecting the cell in the first place.

Studies in non human primates have already shown broadly neutralising anti-bodies to possess the ability to prevent infection.

This encouraging information has led scientists to establish Neutralising Antibody Consortium, whose sole responsibility is pick-up more antibodies with ability to prevent HIV infection.

Formed in 2002, the Consortium has grown from four academic institutions to 18 now.

But as they undertake all these initiatives, scientists believe a vaccine that produces both broadly neutralising antibodies and cellular immune response would be the most effective one in controlling the virus.

An AWC Feature




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