The results of the Phase I Safety and Immunogenicity Trial of Recombinant HIV-1 Tat (ISS P-001 and ISS T-001) indicate that the vaccine based on the recombinant Tat protein is safe, well tolerated and immunogenic. The present study is intended to extend the follow-up of the volunteers for additional 3 years to evaluate the persistence of the anti-Tat humoral and cellular immune responses. The results of the present study will be key for the design of future phase II trials, particularly for the definition of the optimal schedule for boosting immunizations.

All individuals (27) will be enrolled in a 120-weeks observational study and monitored every 24 weeks for the following 3 years. During these visits, which are performed within the schedule indicated for the clinical monitoring of HIV-1 infected individuals, in addition to the routine virological, hematological and biochemical assessment, the anti-Tat specific humoral and cellular immune responses will be evaluated.

Inclusion Criteria:

• Previous participation to the phase I clinical trial ISS T-001

HIV-1 Infected subject previously included in the Phase I Clinical Trial with Tat protein