In hunt for HIV vaccine, focus shifts to stopping transmission
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Scientists have known since 1984 that HIV causes AIDS. But for more than two decades since, the cunning human immunodeficiency virus has foiled all efforts to develop a vaccine.
As nearly a thousand of the world's top vaccine researchers gather in downtown Seattle this week for the four-day AIDS Vaccine 2007 Conference, some of them say the most realistic goal now isn't a vaccine to prevent HIV infection, but rather one that prevents HIV from being passed on.
"The HIV virus is an elusive virus," said Dr. Glenda Gray, a pediatrician and co-founder of the perinatal HIV research unit at the Chris Hani Baragwanath Hospital in Soweto, South Africa.
"I don't think anyone would have expected that it would take so long to find a vaccine."
At the same time, vaccine hunters remain unshaken in their belief that a vaccine is the only way to eventually eradicate AIDS. That's because it is clear now that it's impossible to completely eliminate the biggest sources of infection: unprotected sex, sharing needles, and childbearing and breastfeeding by infected women.
Dr. Lawrence Corey, head of virology for the University of Washington and chairman of the conference, which began Monday, notes that the rate of 40,000 new HIV cases in the U.S. annually has not changed for the past 15 years.
"The only way my granddaughter is going to grow up without the risk of HIV is with a vaccine," Corey said.
Corey is the principal investigator of the HIV Vaccine Trials Network, a global collaboration in the search for an HIV vaccine that is based at the Fred Hutchinson Cancer Research Center in Seattle.
For almost 20 years, researchers have pursued an HIV vaccine by focusing on antibodies in the immune system, which prevent infection.
About five years ago, many researchers shifted focus to vaccines that would produce cytotoxic T-cells, or so-called killer T-cells, to attack HIV-infected cells, Corey said. A T-cell vaccine wouldn't necessarily protect someone from becoming HIV-positive, but it would suppress the infection to delay full-blown AIDS and to prevent transmission to others.
Still, some scientists believe T-cell vaccines wouldn't be enough to stop the spread of HIV, which has infected 40 million people worldwide and killed 25 million.
HIV mutates about a thousand times more quickly than a flu virus, Corey said. And strains of HIV virus can vary from person to person and from region to region, said Pat Fast, executive director for medical affairs for the International AIDS Vaccine Initiative in New York.
That can be a problem for vaccine research: AIDS is raging hardest in Africa, yet subjects in vaccine trials are chosen based on health standards for industrialized nations, Fast said. For example, many Africans are disqualified from clinical trials because their bodies harbor too many parasites or lack high-enough blood-cell counts.
To remedy that, a coalition of HIV-research groups at the conference Monday released the first-ever laboratory benchmarks tailored for Africans.
"It makes sense to try [the vaccine] on the population you'll be giving it to," Fast said. "What's normal in Peoria may not be normal in Lusaka [in Zambia]."
