The Bill & Melinda Gates Foundation took its support of AIDS-related research and care to a new level Wednesday, announcing a half-billion-dollar grant to a global fund that provides AIDS assistance in poor countries.

The Geneva-based Global Fund to Fight AIDS, Tuberculosis and Malaria will receive the grant over five years.

The gift dwarfs the $150 million the Microsoft Corp. (MSFT) founder's foundation has given since the fund was created four years ago, and the additional $287 million Gates announced last month to speed development of an AIDS vaccine.

"The Global Fund is one of the most important health initiatives in the world today," Bill Gates said in a statement announcing the gift. "The Fund has an excellent track record, and we need to do everything we can to support its continued success, which will save millions of lives."

The announcement comes as nearly 25,000 scientists, advocates and policy-makers prepare to meet in Toronto this weekend for the International AIDS Conference.