Jon Cohen, the author of Shots in the Dark- The Wayward Search for an AIDS Vaccine has written a news article in Science about the devastating effect of the recent failure of Merck’s HIV vaccine in its clinical trial. Look here for the press release of the premature end of the trial.

As important as the failure of this clinical trial might seem to those interested in HIV vaccines, I agree with Cohen’s suggestion that this might be the beginning of the end for the novel and interesting concept of T cell inducing vaccines. No vaccine used currently in mass immunization programmes attempts to induce T cells, they all act by stimulating antibodies which prevent infection.

As an ex T-cell vaccine man myself, I have grown fond of the idea of developing vaccines which work by this alternative immune mechanism. While this field is still in its infancy and is slowly becoming more popular, I remember going to conferences where the idea of T cell vaccines has often been scoffed at by immunologists.

In my opinion, there are three main arguments against T cell vaccines. One, that in complex organisms like Plasmodium (causing malaria), Leishmania, Mycobacteria( causing tuberculosis) and HIV it will be difficult to find a single molecule that can be targeted to induce protection. Second, the diversity of Human Leukocyte Antigen (HLA), which are surface molecules that present foreign substances to induce T cells, might require finding a single microbial target common to all main HLA subtypes. Lastly, we do not know enough about how to induce a strong T cell memory response in the human population and therefore a lot of the protection afforded by T cell vaccines might be fleeting.

This failed clinical trial might sound the death knell for T cell vaccines in HIV, although I believe that unless further clinical trials are undertaken and also fail, it would be hasty for us to leave this avenue unexplored. The larger problem might be the use of this trial as evidence for mounting skepticism against T cell inducing vaccines and this might lead to funding for vaccine research in this area becoming tighter.

We should probably take a page out of the history of polio vaccine development and not get too bummed out. In 1934, a trial of a killed polio vaccine had to be stopped because participants were getting polio due to vaccination and the scientific community gave up hope to find a vaccine against polio. Funding decreased and the field remained dormant for many years after that incident until Jonas Salk came along to produce his famous vaccine. I am sure that the fight against HIV is not going to slow down, but I can only hope that it is not time for T cells vaccines to go into hibernation.