The objective of this study is to appreciate the supplementary efficiency brought by an association of more powerful antiretroviral molecules including enfuvirtide on the evolution of PML. This research program will involve 30 patients in several centres in France. All the patients who will participate will receive enfuvirtide during 6 months in association with a combination of two or more potent antiretroviral drugs. The total duration of follow-up for a patient will be of 1 year.