The gels, or microbicides, act like an invisible condom and could offer added protection against the virus that has infected 40 million people worldwide.

   

AIDS experts estimate that even a partially effective microbicide could prevent 2.5 million deaths from AIDS over three years.

   

"We desperately need new methods to prevent HIV transmission in the face of rising prevalence of infection globally," said Professor Jonathan Weber, of Imperial College London, who is working on the project.

   

Condoms are the best method to prevent HIV infection but not everyone uses them. Microbicides would allow women, who account for half of new HIV infections worldwide, to protect themselves if their partners do not use condoms.

 

Effective

   

AIDS experts say microbicides, applied before sex, will be most effective when used along with other prevention methods against AIDS. Microbicides could also protect against other sexually transmitted diseases.

   

"We need a product that women and men find culturally and personally acceptable, as well as free or at very low cost," Robin Gorna, of Britain's Department for International Development (DFID), told a news conference.

 

"There is a lot of optimism about products in development and a lot of work to do to prove that they actually work"

Janet Darbyshire,
Medical Research Council

Sixty microbicide products are under development worldwide and 14 are already in clinical trials. Britain's microbicide development programme, which is backed by the DFID, plans to begin human trials of two vaginal microbicides, Pro-2000 and Emmelle, being developed by the British company ML Laboratories Plc.

   

Trials

 

The trials will enable researchers to see whether the products, which have proven effective in laboratory and animal studies, prevent infection in humans.

   

About 12,000 women will be needed for the trials that will be conducted in Africa, home to the majority of people living with HIV/AIDS.

   

"Even if the products are partially effective, at the level of 40%, 50% or 60%, they could still have a major public health impact," said Professor Janet Darbyshire of the Medical Research Council, who is working on the project.

   

"But to do that, women have got to use them and use them consistently," she added.

   

Plans for the trials were announced ahead of the start of an international microbicide conference in London from 28-31 March.

   

"There is a lot of optimism about products in development and a lot of work to do to prove that they actually work," Darbyshire added.