AIDS vaccine focus shifts after disappointments

By Andrew Quinn

WASHINGTON (Reuters) - A global AIDS vaccine conference this week will seek fresh strategies against the HIV virus, with experts weighing the value of basic laboratory research against large-scale human clinical trials after a string of disappointments.

Approaches focusing on "neutralizing antibodies" that would allow the human immune system to block infection completely, are likely to take precedence over existing models that seek to manage infection after it occurs, experts said.

"There's a real redirection and rethinking," said Lynn Morris, co-chair of a world AIDS vaccine conference that starts in Cape Town, South Africa, on Monday.

"Fundamentally we don't understand enough about the human immune system and we don't know how the immune system deals with HIV."

The conference -- a gathering of many of the top names in HIV research -- follows a year that saw scientists drop plans for widespread human testing of the two most promising vaccine prototypes due to safety concerns.

The AIDS virus infects an estimated 33 million people globally and has killed 25 million since it was identified in the 1980s. Cocktails of drugs can control the virus but there is no cure.

The two stalled vaccines, one developed by drug giant Merck and the other by U.S. government researchers, both aimed to fight AIDS by encouraging so-called cell-mediated immunity, jump-starting T-cells to tackle the virus and stop or slow the progress of HIV-related disease.

But early results from a large human trial of the Merck product were discouraging and data showed the vaccine may have left some people more prone to HIV infection -- halting the tests and prompting some scientists to reconsider the model.  Continued...