Wednesday, January 01, 2003

PROBLEMS WITH DEVELOPING AIDS VACCINE

Moment of Truth Draws Near for Humanity's Best Hope to Date in the Battle Against AIDS
by Steve Connor

The gathering of information about the only AIDS vaccine to go through the final phase of a clinical trial is expected to finish within days so that the findings can be made public early in the new year....

The Vaxgen vaccine was also tried on animals with good results, but protecting a chimpanzee or a monkey against HIV or the simian virus is not the same as protecting people against the human virus.

HIV is perhaps the most difficult virus to target with a vaccine. The virus's killer nature arises from the way that it eventually disables the immune system. But the key to its survival is the way that it initially outwits that system by evolving at an incredible speed. Its genetic structure mutates about a million times faster than that of humans. With influenza, it is the fastest-evolving lifeform on the planet. In the course of infecting one person it spawns hundreds or even thousands of slightly different strains. A person can be infected with one strain of HIV and die years later with a totally different population of its "quasispecies", each slightly different in its genetic alphabet to the next.

That makes it difficult to design anti-viral drugs, because one is trying to hit a moving target, biologically speaking....