A Phase Il of a Therapeutic, Recombinant, Biologically Active HIV-1 Tat Protein Vaccine in HIV-Infected, Anti-Tat Negative, ARV-Treated Adult Volunteers

Inclusion Criteria: * Male and female volunteers aged 18-45 years (inclusive) * Anti-Tat antibody negative * HIV-1 infected individuals currently receiving treatment with ARVs * Chronically suppressed HIV-1 infection as indicated by a HIV-1 plasma viraemia \< 400 copies/ml and a CD4+ T cell count ≥ 200 cells/μl at screening, and documented at least once during the 12 month period prior to screening, irrespective of the pre-ARV CD4 nadir. * Negative pregnancy test for females of childbearing potential (not sterilized and still menstruating or within 1 year of the last menses) to be performed during the screening phase and immediately before each vaccination, and use of an acceptable method of contraception (double barrier methods, combined oral contraceptives, injectable contraceptives or intra-uterine devices) for at least 3 weeks prior to the first vaccination and for the duration of the study * Has provided written informed consent. * Agrees to stay in contact with the research site for the duration of the study Exclusion Criteria: * Acute illness on Study Day 0 * Body temperature \>=37.5 °C on Study Day 0 * Any current AIDS-related opportunistic disease * Any current neoplastic disease * Known history of malignant neoplastic diseases \[NOTE: Subjects with known history of non-malignant neoplastic diseases that are completely resolved according to the fulfilment of all the specific recovery criteria, in agreement with the current guidelines in medical oncology, are eligible\] * Known history of encephalopathy, neuropathy or unstable CNS pathology, immunodeficiency, autoimmune disease, angina or cardiac arrhythmias, or any other clinically significant medical problems in the opinion of the investigator * Any evidence, as judged by the investigator, of unstable cardio-vascular disease (e.g. unstable hypertensive disease needing modification or introduction of an anti-hypertensive treatment) * Chest radiography showing evidence of active or acute cardiac or pulmonary disease within 6 months prior to the study screening visit \[Note if no previous chest X-ray available, this will be performed at screening\]; * Known history of anaphylaxis or serious adverse reactions to vaccines * Known history of serious allergic reaction to any substance, requiring hospitalization or emergent medical care (e.g. Steven-Johnson syndrome, bronchospasm, or hypotension) * Active pulmonary tuberculosis within 12 months of screening as evidenced by chest radiography and/or medical history. * Any known medical or psychiatric condition which precludes subject compliance with the protocol, specifically, persons with psychotic disorders, major affective disorders and/or suicidal ideation are to be excluded * Current use of psychotropic drugs prescribed for major psychotic disorders * Concomitant participation in any study with an investigational product or device * Current or prior therapy with immunomodulator, immunosuppressive and/or anticoagulant drugs within 30 days prior to administration of the investigational product * Live attenuated vaccines within 60 days of the first administration of the investigational product \[NOTE: Medically indicated sub-unit or killed vaccines (e.g., influenza, pneumococcal, hepatitis A and B) are permitted, but must have been administered at least 4 weeks prior to the first administration of the investigational product\] * Known receipt of blood products or immunoglobulins during the year prior to screening * Previous participation in an HIV-1 vaccine trial (subjects who are known to have previously participated in the placebo arm of an HIV-1 vaccine trial, and so have never received an investigational HIV-1 vaccine, are eligible for inclusion) * Known drug and/or alcohol abuse in the year prior to screening * Use in the last 6 months or concomitant use of anti-CCR5 inhibitors and/or integrase inhibitors and/or fusion inhibitors * Pregnant or lactating females