Impressions of a virus and how to combat it

Simon Wain-Hobson; Molecular Retrovirology Laboratory. Institut Pasteur, Paris (France)

Just what is an HIV genome? The question is simple, the answer extraordinarily difficult. Although HIV has a high mutation rate, flu and polio do better. It is however the regent of recombination with an average of 3 crossovers per genome per cycle. For recombination to be of any consequence cells must harbour multiple proviruses that are genetically distinct. Both conditions are largely fulfilled in vivo. In fact the HIV genome is so ephemeral, "for a cycle", that we need to find alternative ways to describe it. Many of the 19th century painters had the same problem trying to capture the infinite shades of colour and light. The impressionists certainly succeeded so why can't HIV geneticists? Yet hasn't HIV variation been a little over done. After all, we can vaccinate against RNA viruses with high mutation rates - polio, measles and to some extent flu - while the "best" SIV/HIV vaccines to date are afforded by the live attenuated viruses which are recombinogenic. A novel highly attenuated strain of SIV that "protects" strongly against an uncloned heterologous challenge virus will be described again emphasizing that HIV/SIV variation is not an inevitable stumbling block.