India stops further trials of HIV vaccine
[NEW DELHI] Further human trials of a US-produced HIV/AIDS vaccine will not be conducted in India after it was found to induce poor immune responses.
The decision was announced last month (November).
The vaccine, developed by the US-based Targeted Genetics Corporation, uses the adeno-associated virus (AAV) as a vector to deliver an AIDS vaccine against subtype C, the dominant HIV subtype in India.
India's National AIDS Research Institute (NARI) tested the vaccine on 30 volunteers.
"[The vaccine] met safety criteria, but did not induce immune responses in a sufficient number of the volunteers to meet the criteria for advancement. At present there are no plans to test it further," Pat Fast, executive director of medical affairs at the International AIDS Vaccine Initiative (IAVI), told SciDev.Net.
Fast said the vaccine showed a 20 per cent immune response in the phase I trials — IAVI generally looks for 60 per cent immune response before moving on to phase II. The vaccine has shown a similar response in trials in Belgium and Germany.
The halt comes at a time when animal studies of AAV are suggesting that the virus may pose a risk to human health.
A study, led by the US-based University of Pennsylvania and published in the November issue of the Journal of Clinical Investigation (JCI), reports that AAV affects the ability of a crucial group of immune cells — CD8 cells, a type of T cell — to proliferate in vaccinated mice.
CD8 cells play a key role in the immune response to HIV infection, killing the infected cells.
"I am relieved that the trial is halted in India. Although our work centred on mice we cannot rule out a similar impairment in human vaccine recipients," Hildegund Ertl, professor at the university's Wistar Institute and one of the authors of the JCI study, told SciDev.Net.
In July 2007, a study published in Science showed links between a disabled AAV vector and tumour growth in mice. It concluded that further research into AAV is needed to determine its long-term safety in humans.
However, Fast points out there are fundamental differences between the immune responses of mice and humans, particularly with regards to HIV. Additionally, the mice received a very high dose of the vaccine — which is known to impair immune response.
India's hopes for a HIV vaccine now rest on an ongoing trial at the Tuberculosis Research Centre (TRC) in Chennai, on a modified vaccinia Ankara virus, one of the pox viruses, as a vector.
Link to full paper in the Journal of Clinical Investigation [1.4MB]
References: Journal of Clinical Investigation doi 10.1172/JCI33138 (2007)
Science 317, 477 (2007)