Canadian Network for Vaccines and Immunotherapeutics - CANVAC

The Canadian Network for Vaccines and Immunotherapeutics finds hope in the search for an AIDS vaccine

The prostitutes of Majengo, Kenya, lead lives of quiet desperation. But a small handful also show that the absolute worst circumstances can give rise to the best that human beings have to offer: hope for the future. And hope for a vaccine to help millions of people not just in Kenya, but also in Canada and around the world.

Since HIV (the virus that carries AIDS) first appeared in Kenya in the early 1980s, the sexually transmitted disease (STD) has infected 95 percent of the prostitutes who work in the grim shantytown outside Nairobi. Five percent, however, have remained HIV-free, despite contracting other STDs and despite showing no behavioural differences from those who were infected. The question is how.

"We think that they are resistant to the AIDS virus, that something in their immune systems is able to recognize and kill the disease," says Dr. Frank Plummer, one of the world leaders in the hunt for an AIDS vaccine. He is a University of Manitoba Professor of Medical Microbiology and a member of the Canadian Network for Vaccines and Immunotherapeutics (CANVAC). Based for much of the year in Kenya, he has been testing the prostitutes for HIV at a clinic for STDs since 1985 as part of a team of Canadian, American and Kenyan researchers.

"Most successful human vaccines have been developed on the basis of understanding natural immunity," says Dr. Plummer. "If you understand how natural immunity takes place, you can create a vaccine that duplicates the response."

Science has shown that certain people are immune to the AIDS virus because they lack a particular co-receptor necessary for HIV to infect cells. But the "something" at work in the Kenyan prostitutes' immune systems appears to be quite different.

The most likely candidate is an abundance of killer T-cells specific to HIV. The researchers believe that immunity has built up in the prostitutes like a callus: Their first exposure to the virus provoked enough T-cell production to beat it back, and the second and subsequent exposures provoked even more T-cells, which heightened immunity again and again. This theory was reinforced when several women with immunity left prostitution for a time, then returned to it and contracted the virus.

"We are trying to develop a vaccine to promote a T-cell response to HIV like the one we have seen in the prostitutes," says Dr. Plummer. "All of us should be able to respond to the virus the way these women are responding."

Dr. Plummer now works as part of a partnership that involves the universities of Manitoba, Nairobi and Oxford and the International AIDS Vaccine Initiative. This vaccine based on T-cell response is one of a handful of candidate vaccines picked for rapid development by the International AIDS Vaccine Initiative.

The initial phase-vaccinating small numbers of humans to test for safety and immune responses-began in January 2001 in collaboration with Oxford University. Volunteers in both the UK and Kenya are participating in these early trials.

CANVAC is one of 20 federally funded Networks of Centres of Excellence, the objectives of which are to enhance the Canadian economy and our quality of life. The program is funded by the Natural Sciences and Engineering Research Council (NSERC), the Canadian Institutes of Health Research (CIHR) and the Social Sciences and Humanities Research Council (SSHRC), in partnership with Industry Canada.

For more information on CANVAC research initiatives, visit www.canvacc.org.