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U of M researchers zero in on HIV vaccine

'Naturally immune' women the key: expert

By: Amy Husser

Posted: 03/18/2010 1:00 AM | Comments: 0 (including replies)

It was in 1988 -- just a few years after HIV was discovered -- that Keith Fowke travelled to Nairobi as a graduate student to study a group of Kenyan sex-trade workers who, despite their repeated exposure, somehow managed to elude infection.

After two decades of research, Dr. Fowke -- now a microbiologist -- believes these seemingly "naturally immune" women could unlock the secret to the deadly virus -- and lead him directly to a vaccine.

"Some people who are exposed to HIV don't get infected; that's really changed how people think," he said. "In the HIV (research) community, people that wanted to learn about the immune response studied people who were infected by HIV, those who can be thought of as immune failures in that they weren't able to keep HIV away.

"It's very different to study people who are exposed to HIV but are not infected."

Fowke is part of a team of 40 University of Manitoba researchers who have been pioneers in the field since it began.

While he explained that most exposure to the virus won't actually result in infection -- only one in 10,000 particles of the virus is typically infectious -- finding immunity in such a high-risk group of individuals in the AIDS-ravaged East African country is incredibly "counter-intuitive."

According to the World Health Organization, 33 million people worldwide are infected with HIV, including 65,000 in Canada. In Kenya, however, more than seven per cent of the population is infected -- much higher than the global rate of 0.6 per cent -- with the virus that causes the immune system to fail, leading to life-threatening infections that can no longer be warded off.

The team's Kenyan project, where another 40 researchers are based, recently revealed another potential breakthrough; the sex workers appear to have immune quiescence -- or constantly "resting" cells.

"These women have cells in their immune system that are very calm, cool and collected," said Fowke, explaining HIV thrives in cells that are "turned on" with a high metabolism.

"It's like a car being in neutral but with the accelerator pushed down; (if it's) suddenly slammed into gear, it just takes off. HIV is able to replicate much more efficiently in a cell that's activated and highly revved up," he said. "So when HIV is looking for a suitable cell to infect, it would pass over those cells because they are seen as an inhospitable environment."

Fowke describes his life's work as both "frustrating and exhilarating" because of the rapidly changing virus.

According to Fowke, HIV mutates by one per cent each year. Based on well-known influenza data, researchers know that a vaccine often becomes ineffective if a virus changes by two per cent or more.

"The biggest challenge in HIV vaccine design is that you are trying to hit a moving target," he said.

But Fowke is optimistic that a vaccine will be discovered within his lifetime.

"This is not a theory that is being tested in a test tube," he said. "These are real women, living in the real world and they are being exposed to HIV a tremendous amount and yet they are not being infected. It gives us encouragement that the answer is there -- we just have to be smart enough to try and figure it out."

-- Canwest News Service

Republished from the Winnipeg Free Press print edition March 18, 2010 A6

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