- PI GROUP: prior virologic failure of a Highly active antiretroviral therapy (HAART) regimen including a Protease inhibitor (PI) (ritonavir boosted or not), and a second consecutive start HAART regimen including a PI boosted with ritonavir + 2 Nucleoside Reverse Transcriptase Inhibitor (NRTI). The 6 months prior to the start of the second HAART regimen, are considered as a baseline.