tgAAC09 differs from most other AIDS vaccine candidates now in trials in that it is potentially a single-shot vaccine, rather than one that would require multiple injections over time. A single-shot AIDS vaccine would be particularly useful for developing countries, where most new HIV infections occur, as delivery of healthcare in these regions can be haphazard.
Given the apparent failure of behavioural interventions to stem the spread of the disease, a preventive vaccine is considered the best approach to stop the spread of the HIV/AIDS epidemic, now infecting 14,000 people daily around the world. 95 per cent of these individuals live in developing countries, and Targeted Genetics and its collaborators, including the International AIDS Vaccine Initiative (IAVI), have committed to bringing it to the market at a price that is affordable in the developing world.
The vaccine is based Targeted Genetics' rAAV (recombinant adeno-associated viral vector) technology. This is used to elicit two different types of immune responses, an antibody response and a cell-mediated response, as this dual response is considered essential for effective prophylaxis.
However, an effective preventative vaccine has eluded researchers for years.Earlier in 2003, trials of another prophylactic HIV vaccine, AIDSVAX, failed to protect against infection in Caucasian and Latin races, but demonstrated some activity in blacks and Asians. Later, a variant on the product designed for use in Asia achieved disappointing results in a trial of intravenous drug abusers in Thailand.
Meanwhile, global estimates from the United Nations showed about 40 million people worldwide are living with HIV/AIDS, including an estimated 2.5 million children under 15 years old. About five million people were infected in 2003.
The trial of tgAAC09 is being conducted at the Centre Hospitalier Universitaire Saint-Pierre in Brussels. It will enroll up to 50 volunteers, both men and women, and will test if tgAAC09 is safe and elicits the desired immune response.
At least a dozen other vaccines are in human trials, but all are a long way from reaching the market.