Still a Long Way to Go for HIV Vaccine
By Papiya Bhattacharya | Published: 16th December 2013 09:37 AM |
Reports about a series of clinical trials called the STEP trials, to test the efficacy of a HIV vaccine, have revealed that people injected with the vaccine had a higher possibility of getting infected. These trials involved 3,000 uninfected people in North and South America, Australia and Phambili in South Africa.
Dr Rajat Goyal, Country Director of International AIDS Vaccine Initiative (IAVI) told Express, “In the STEP Phambili and HVTN505 studies, perhaps the vaccine was not able to prevent infection. Currently available data does not provide evidence beyond Ad5 (adenovirus-5) when considering safety issues with adenovirus vectors at large. The data for Ad5 used in the STEP/Phambili and HVTN505 trials cannot be generalised for other adenoviruses.”
Referring to IAVI’s current work, he said India is an important player in its plans.
He said the initiative has programmes to screen, identify and prioritise immunogens. He explained IAVI had a rural research centre at Karad, Maharashtra, which had high prevalence of HIV. “IAVI is working on protocol G - to generate antibodies from volunteers who are HIV positive but neutralise the virus and do not get AIDS. India and South Africa have joined hands to develop an AIDS vaccine while there is a similar initiative with Australia as well,” he added.
How long would it take IAVI to come up with a vaccine for HIV? While Dr Goyal was non-committal, he assured the initiative is focusing on the right areas and had laid a foundation that would lead to huge amounts of data.
Phases of Trials
Dr Goyal, Country Director of International AIDS Vaccine Initiative (IAVI), also provided details of various clinical trials by IAVI in India.
“The first trial was initiated in 2005 at National AIDS Research Institute (NARI) in Pune. The vaccine was found to be safe, well tolerated and moderately immunogenic at high doses,” he said.
However, the vaccine was not found to be suitable for advanced clinical development. The second Phase-I trial of another vaccine, TBC-M4 (modified vaccinia ankara or MVA), began in early 2006 at the Tuberculosis Research Centre (TRC) in Chennai. The vaccine was found to be safe and elicited modest immune responses among volunteers, Dr Goyal explained.
The vaccine was then considered for another Phase-I trial in combination with another vaccine as a ‘prime boost’ regimen. Prime-boost is a method of combining two different vaccines with the hope of getting the best possible response from the body’s immune system.
The third Phase-I clinical trial was initiated in March 2009 at NARI and TRC to test two vaccine candidates- ADVAX and TBC-M4- in a prime-boost regimen.
“The trial ended in 2011. Both these regimens were found to be safe and they evoked modest immune responses in the majority of volunteers,” Dr Goyal explained. However, the vector was identified as being genetically unstable, suggesting that it would be difficult to predict batch-to-batch consistency of the vaccine for efficacy studies and for commercial manufacturing.