India halts HIV vaccine trial11th December 2007
India's hopes for a vaccine against HIV have taken a knock with the cancellation of human trials of a potential candidate.
The US-produced vaccine was shelved after it was found to produce poor immune responses in people.
The company developing the vaccine, Targeted Genetics Corp, had hoped to use the adeno-associated virus (AAV) as a vector to deliver the vaccine targeted the sub-type C HIV virus most commonly found in India.
The vaccine met safety criteria during a trial on 30 volunteers, but did not induce immune responses, according to a statement by India's National AIDS Research Institute, or NARI.
Further trials were discontinued, said Pat Fast, executive director of medical affairs at the International AIDS Vaccine Initiative (IAVI).
The vaccine had shown a 20% immune response in phase I trials. But IAVI generally looks for 60% immune response before moving on to phase II. The vaccine has shown a similar response in trials in Belgium and Germany.
In addition, recent studies in animals have shown that the virus used to deliver the vaccine, AAV, may pose a greater risk to human health than was previously thought.
A study carried out on vaccinated mice, led by the University of Pennsylvania and published in the November issue of the Journal of Clinical Investigation (JCI), showed that AAV affected the ability of a crucial group of immune cells - CD8 cells, a type of T cell.
CD8 cells play a key role in the immune response to HIV infection, killing the infected cells.
One of the study's authors, Hildegund Ertl, professor at the university's Wistar Institute, said she was relieved that the trial had now been halted in India. A similar immune impairment in human vaccine recipients could not be ruled out, she said.
In July 2007, a study published in the journal Science showed links between a disabled AAV vector and tumour growth in mice said more research was needed into AAV to determine its long-term safety in humans.
Critics of the JCI study pointed to fundamental differences between the immune responses of mice and humans, particularly where HIV is concerned. The mice in the study had also received a very high dose of the vaccine.
Another HIV/AIDS vaccine trial is ongoing at the Tuberculosis Research Centre (TRC) in Chennai, using a modified vaccinia Ankara virus, one of the pox viruses, as a vector.
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Title: India halts HIV vaccine trial
Author: Luisetta Mudie
Article Id: 5051
Date Added: 11th Dec 2007