Scientists around the world continue to struggle with the challenge of developing a working vaccine against the AIDS virus. Yet while 30 trials are underway on six continents, a vaccine that could block infection remains frustratingly out of reach.
Two experts provided an update on efforts to develop a vaccine against HIV, the virus responsible for AIDS, on the closing day of the AAAS science meeting in Washington yesterday.
The United Nations Programme on AIDS estimates there are 39 million people across the globe living with the virus and 2004 alone saw almost five million new HIV infections.
There are now 30 different vaccine trials underway including a second new trial in India and existing trials in the US, Europe and Africa, according to Dr Seth Berkley, president of the International AIDS Vaccine Initiative which funds trials.
Most of these are start-up Phase I trials but there are also later Phase II trials in train. All, however, rely on "cell-mediated immunity", according to Dr Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases.
This form of immunity only works after a person has been infected by a virus, targeting cells already invaded by disease. "These protect against progression of disease," Dr Fauci said.
No important vaccines used today rely only on this form of immunity, and instead depend on a host developing antibodies that can prevent disease, he said. None of the trials planned so far could produce any neutralising antibody response.
Dr Berkley said, however, that having a vaccine that could deliver a cell-mediated response would still be valuable.
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