The search for a safe and efficacious AIDS vaccine has received a shot in the arm. The Phase I trial, aimed primarily at ascertaining the safety and HIV–specific immune response of a candidate vaccine, has yielded encouraging results in the exercise conducted at the Tuberculosis Research Centre, Chennai. Unlike the vaccine tried out earlier at the National AIDS Research Institute, Pune — the first time ever in the country — the one used in the Chennai tri al, apart from returning a positive verdict on the safety count, threw up a remarkable outcome by way of good immune response in all the volunteers. The cent per cent immune response reported by those who had received the high dose places this candidate AIDS vaccine as far superior to any other tested so far on humans. But there were also some shortcomings. While the immune response has been across the board, the level of such response was seen to be not only modest but declining over months. Since the level and persistence of immune response is equally important, the Modified Vaccinia Ankara-based vaccine tried out at Chennai may not be the best candidate if used alone. The proposal to use, along with it, a DNA-based vaccine in the Phase I prime-boost vaccine trial to be started next year at NARI and the TRC makes eminent sense in this context. Efforts should be directed towards producing a DNA vaccine construct using HIV genes isolated from Indian HIV strains as in the case of the candidate vaccine used in the Chennai trial. Such a vaccine may well produce a better immune response.
The vaccine tested in Chennai is unlikely to prevent infection. It is not surprising, given that most of the vaccine candidates being tested across the world are designed more to keep the viral load under check, thereby delaying the progression to the diseased state, than to prevent infection. With no medicines available to cure HIV and with no vaccine to prevent infection at an advanced stage of testing, the time-tested measures to prevent infection gain utmost importance. Apart from producing a promising candidate vaccine for a prime-boost trial, the scientists attached to the TRC and NARI have gained valuable experience from their participation in trials of international standards. The Phase I prime-boost trial to be conducted at the same institutions, subject to regulatory approvals, will go a long way in further upgrading them and enhancing the level of competence of the scientists. This is a big gain as India is fast becoming an ideal field for undertaking various drug/vaccine trials.