A roll-over observational study (ISS T-003 EF-UP) is being conducted to extend the follow-up of the volunteers of the ISS T-003 trial in order to evaluate the persistence of vaccine immunogenicity as well as of the immunological and virological effects induced by the therapeutic immunization with Tat.

An open label, non-interventional study roll-over study (ISS T-003 EF-UP) is being conducted to follow-up the persistence of vaccine humoral responses as well as of the immunological and virological effects induced by the therapeutic immunization with Tat.To this aim volunteers of the ISS T-003 study are included in one year study, with visits at weeks 0 and 24 and 54.

To assess the anti-Tat humoral immune response by the determination and titration of IgM, IgG and IgA anti-Tat antibodies (primary endpoint) and to evaluate CD4+ T cell counts and HIV-1 plasma viraemia (as secondary endpoint).

In addition, depending on the availability of residual specimens (PBMC, serum and plasma), further laboratory tests (i.e. HIV DNA copies in blood) to investigate in-depth the immunological and virological profile of the volunteers is being performed.

Physical examination is being performed to monitor the clinical status of the volunteers and to record the appearance of clinical signs and symptoms of disease progression as well as AIDS-defining events, data or records related to ARV treatment compliance. Pregnancy onset for female participants will also be recorded.

Inclusion Criteria:

• previous participation in the ISS T-003 trial without withdrawal of consent;
• availability to participate in the extended follow-up study;
• signed informed consent.

Exclusion Criteria:

• The absence of any of the above criteria will exclude the participants from the study

HAART-treated patients who participated to the therapeutic phase II trial of the Tat vaccine "ISS T-003"