This phase II clinical trial was directed at evaluating the immunogenicity and the safety of the HIV-1 Tat protein-based vaccine. Anti-Tat antibody negative, HIV-1 positive subjects treated successfully with HAART have been screened and recruited for a 48-weeks study, including a period of 16 or 8 weeks treatment phase and a period of 32 or 40 weeks follow-up phase, in arm A or Arm B, respectively. One hundred sixty-eight subjects have been randomized 1:1:1:1 to one of the 2 arms (Arm A and Arm B) and each arm has been divided in the following groups: