First days after HIV infection may hold vaccine key

Phanice Nyandoya (L), 2, and Antony Ochien (R), 4, both living with HIV/AIDS listen to their class teacher at the Dagoretti Children's Centre in Nairobi November 28, 2008. An estimated 33 million people worldwide were living with the HIV virus, mostly in sub-Saharan Africa, at the end of 2007. AIDS has killed 25 million since being identified in 1981.

GENEVA (Reuters) - The body's initial response to contracting HIV could provide the answers scientists need to develop a vaccine for the AIDS-causing virus, a Nobel-winning expert said on Monday.

The AIDS epidemic has killed about 25 million people, and about 33 million worldwide are now infected with HIV. Cocktails of drugs can control the virus but so far there is no cure.

Francoise Barre-Sinoussi, who shared the 2008 Nobel prize for medicine with Luc Montagnier for their discovery of HIV a quarter-century ago, told a World AIDS Day event that the human body reacts very distinctly -- and quickly -- to HIV infection.

The nearly immediate cellular responses seen in the gut and elsewhere could point scientists toward a vaccine that keeps HIV from taking hold and morphing into the immunity-destroying disease, the French expert said.

"Everything is decided very early after exposure to the virus ... When I say very early after, it is a matter of days," she said in a speech at the World Health Organization.

"If we know better the early events of the acute infection, we can think about developing a better vaccine strategy," she said, warning: "If we don't make progress in this basic knowledge, we will never have a vaccine."

Recent efforts to develop a vaccine by jump-starting immune-system cells that tackle the virus -- such as one last year by Merck -- have yielded disappointing results.

Barre-Sinoussi said such "conventional" vaccines would not be enough to tackle HIV, which is a retrovirus, meaning it copies bits of its own genetic code into the DNA of its host.

"We have to consider the conventional approach together with another approach that considers the pathogenic signals," she said. "We need to understand better the role of genetics."

The Institut Pasteur expert also called for more research into co-infections between HIV and tuberculosis, and hit back at those who say the billions of dollars that have been funneled into AIDS projects have drained funds needed for other diseases.

"I am a little bit surprised to see an opposition between the fight against HIV and other primary health issues. It is a total misunderstanding and a major mistake," she said. "I do not understand why these people cannot work together."

(Editing by Katie Nguyen)