Wednesday, May 4, 2011

Promising Aids vaccine trials start in Kenya

Both vaccines have been tested in the USA and Europe. Trials have also been going in Asia until last year when Kenya was selected. Photo/FILE

Both vaccines have been tested in the USA and Europe. Trials have also been going in Asia until last year when Kenya was selected. Photo/FILE 

By ARTHUR OKWEMBA aokwemba@yahoo.com

Trials on an Aids vaccine that is generating a lot of excitement in the scientific world have finally started in Kenya with several volunteering for vaccination.

The country becomes the third in Africa to start trials on the most advanced Aids vaccine design likely to stop the virus from surviving in the body.

It produces both antibody and cellular immune response effects.

The antibody response is able to stop the virus from infecting the cell in the first place, while the cellular immune response will destroy the cells already infected with virus, stopping such cells from causing further infection.

Research centre

In an exclusive interview with the Nation, scientists at the Kenya Aids Vaccine Initiative (Kavi) said they were, in collaboration with International Aids Vaccine Initiative (IAVI), testing two vaccines of this nature at two Kavi research sites in Nairobi.

Kavi is a research centre of the University of Nairobi. One of the vaccines, Ad35/Ad26, is being tested at Kangemi site B003 and the second one, Ad35/GSK Protein, is being tried at Kenyatta National Hospital site B002.

Both vaccines have been tested in the USA and Europe. Trials have also been going in Asia until last year when Kenya was selected.

Recruitment of volunteers started in February, and so far each of the locations have vaccinated nine volunteers, a development that has impressed researchers.

“We are excited that Kenyans are more receptive to the idea of participating in clinical trials as volunteers than was the case four years ago,” says Prof Omu Nzala, Kavi director and one of the principal investigators.

According to Prof Nzala, research among a group of HIV positive people, including those from Kenya, has proved their immune system to possess the ability to stop the virus from progressing from HIV to Aids, even without a vaccine inducing such immune systems.

Failure to get Aids has reduced Aids-related deaths among this group of people. When the vaccine trials begun in the country in 2003, it took the scientists more than nine months to recruit the number of volunteers they needed due to the fear people had about such studies.

But now Kenyans have become one of the most receptive populations to clinical trials. The willingness of Kenyans to volunteer for such clinical trials described as being done in the interest of humankind seems to have endeared the country to those funding Aids research.

In the current trials, those vaccinated are to be followed for 16 months, meaning results of Phase One trials are likely to be released in November 2012. Women, who have in the past avoided such trials, are volunteering at the same pace as men.

Volunteers have to be HIV-negative, over 18 years, and at very low risk of HIV infection, meaning at this stage high risk groups are excluded as volunteers.

Scientists across the world have described the new vaccine design as the best weapon against a virus that has defied many interventions.

While Kenya’s past trials on other Aids vaccines have proven that a preventive HIV vaccine is possible, they did not produce the desired results to move to the efficacy trials.

Currently, vaccine performance of 30 per cent and above is being used as a desirable threshold to move the studies to the efficacy stages.

If successful, Kenya is going to benefit immensely in terms of access to the vaccine and funding for future research in the area.

The testing of the two vaccines in two locations simultaneously is a further indication of Kenya’s increased capacity and capabilities in terms of human skills, quality facilities, regulatory authority knowledge on vaccine matters, community receptiveness, and donor confidence in the Kenyan scientists and facilities.

These factors have made it easy for Kenyan researchers to commence recruitment of volunteers without many issues about the vaccine being raised.

The volunteers are critical in such research since they will help scientists determine if the inclusion of antibodies in the design is going to improve the vaccine performance.

Stop the virus

Scientists have for a long time argued that the best strategy would be to stop the virus from infecting the cell. But at the same time, they have explored a strategy that stops the virus from replicating once in the cell.

Last year, a vaccine design of this nature tested in Thailand was able to produce an immune response of 30 per cent, the highest since vaccine trials begun in the world more than 10 years ago.

Buoyed by this success, researchers across the world have focused significant amounts of their resources on this new vaccine design.

Studies in the animal model, where the combined antibody and cellular immune response vaccine was first tested, showed remarkable results.

The vaccine induced better immune response, with high increases in the CD 4 and CD 8 cells — immune cells that protect the body from infections. This response was also shown to be broader and to last longer than the previous designs.

With this data, the vaccine was moved into human trials, with studies in the US and Europe. In Africa, trial on vaccine Ad35/Ad26 is being done in Kenya, South Africa and Rwanda.

It is also being done in Boston, United States. The Ad35/GSK Protein vaccine is being tried in Kenya, Uganda and Zambia.

In other recent research, a team of scientists including those from Kenya has isolated three broadly neutralising antibodies from long-term HIV survivors.

The antibodies are able to neutralise 90 per cent of the HIV-1 virus. Scientists are now working on an Aids vaccine using this information.

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