Medical professor Warner Greene of the Gladstone Institute of Virology and Immunology in San Francisco, California, said in Uganda that his London colleague, Michael Malim, "has established how the (HIV) virus enters and degrades the Apo Bec 3G cell."

"We think if a drug is developed that can close up the cell's membrane, the virus will not be able to enter and it will provide a great prevention strategy," Greene told reporters in Kampala during the opening of an AIDS research facility.

"We don't have a drug yet, but this is the most important breakthrough and a possibility for future drug discovery," he added.

Ugandan President Yoweri Museveni, who has presided over Africa's most successful AIDS-prevention campaign, said the announcement would "cause some smiles on many faces."

When the human body is invaded, there is a rapid increase in the production of T4 cells, which is the body's signal that a pathogen is present and an immune response must be mounted for protection, a system the HIV virus interferes with.

Additionally, when HIV encounters a T4 cell inside the blood system, it attaches itself and inserts its genetic code into the cell.

"In this way, the T4 is transformed into a biological factory that begins producing new HIV," according to the scientists.

UNAIDS estimates that Africa is home to 26 million of the world's 40 million AIDS patients.

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