Cape Town — Scientists yesterday began enrolling volunteers for SA's first phase two clinical trial of a candidate HIV vaccine, under a multisite study funded by the International AIDS Vaccine Initiative.

Scientists will be testing a vaccine called tgAAC09, developed by Nasdaq-listed Targeted Genetics Corporation, which combines two of the latest techniques for helping the body defend itself against HIV.

More than 6-million South Africans are infected with HIV.

With no cure in sight, a vaccine offers the best hope of combating the pandemic.

So far local scientists have only carried out phase one trials on potential HIV vaccines, which test safety. Phase two trials go on to test the ideal dose and how often to inject healthy volunteers to provoke an immune system response.

SA's selection for a phase two trial signals international confidence in the quality of its scientific research, said the study's national protocol chair, Eftyhia Vardas, of the University of the Witwatersrand's Perinatal HIV Research Unit.

Scientists hope tgAAC09 will provide protection from HIV by prompting the body to make anti-bodies against the virus, and stimulating the body's own mechanisms for getting rid of infected cells.

"It's very exciting science," said Vardas.

The institute has funded three South African testing sites -- the Perinatal HIV Research Unit at Chris Hani Baragawanath Hospital, the Desmond Tutu Institute for HIV Research at the University of Cape Town, and the Medunsa Campus of the University of Limpopo.

"Finding a vaccine to stop the spread of the HIV virus must be a global priority," said AIDS Vaccine Initiative CEO Seth Berkley.