The primary objective of the trial is to assess the ability of an early and intermittent antiretroviral therapy in maintaining an immunological stability in antiretroviral naive HIV infected adults, to offer a potential alternative strategy to differed and continuous antiretroviral treatment.This is a 2-year phase II, open-label, multicentric "proof of concept" trial. The patients included are treated following a pulse-therapy scheme, i.e. 6-month periods with once daily boosted-PI based therapy in alternance with 6-month periods without antiretroviral therapy. The preferentially recommended treatment of the study is atazanavir boosted with ritonavir, associated with a fixed combination of abacavir and lamivudine or emtricitabine + tenofovir.The patients are closely followed to assess the efficacy and the tolerance of the strategy, with clinical, biochemical, immunological, virological and pharmacokinetic evaluations.