You know that depressing feeling that whenever you’re in a hurry and waiting for the bus, its always running late, and that excitement you feel as two turn up at once? Well those working in the HIV vaccine arena must have a similar feeling, as after years of depressing failures two exciting results have been published within the last month.

While the first result discussed the discovery of two broadly neutralising antibodies that block a large number of HIV strains from entering T-cells, the second result is perhaps even more surprising as it involves the results of a clinical trial of a combination of two vaccines that had both been canned by their developers.

The RV144 trial showed that a combination of Sanofi-Pasteur’s Alvac and VaxGen’s AidsVAX B/E cut the risk of HIV infection by 31 per cent. Alvac consists of a disabled canarypox virus modified to carry synthetic versions of three HIV genes into the body, and was designed to prime the immune system to release T-cells that hunt down and kill infected cells. AidsVax was designed to produce neutralising antibodies that destroy HIV before it infects cells, and contains the gp120 protein that the virus uses to enter cells.

Both vaccines had failed in trials where they were tested separately, and both developers had given up on them. But when combined they seem to work synergistically to cut the risk of infection.

While the positive reduction has been met with great excitement, experts have warned that the result is merely a proof of principle and that further studies will be needed to validate the results.

Full analysis of the trail, which was conducted on over 16,000 Thai volunteers aged between 18 and 30 and deemed to be of moderate risk of infection, is still being conducted. But the fact that of the 8,197 given the drugs 51 became infected compared to 74 of the 8,197 that were given a placebo bodes well for the future development of so-called ‘prime-boost’ vaccines.

Matt Wilkinson