Inclusion Criteria:

• Ages 18-60
• HIV-1 infection, as documented by any licensed PCR kit or ELISA (confirmed by an complementary assay e.g. Western blot HIV-1 culture, HIV-1 antigen, plasma HIV-1 RNA, or a second antibody test by a method other than ELISA) at any time prior to study entry.
• Stable on HAART for at least 6 consecutive months prior to study entry (changes of one drug for the another drug due to reasons other than virologic failure are allowed)
• Plasma HIV-1 RNA levels of < 50 copies/ml for at least 6 months prior to study entry (two single blips of up to 200 HIV-1 RNA copies/ml are acceptable if they resolve spontaneously without a change in HAART)
• Plasma HIV-1 RNA levels of < 50 copies/ml at study entry
• CD4 nadir >100
• CD4+ cell counts > 250/µl (one measurement within 4 months prior to study entry and one measurement within screening phase)
• For women, negative serum pregnancy test at screening and negative urine or serum pregnancy test within 24 hours prior to vaccination.
• If the volunteer is female and of childbearing potential, she agrees to use an acceptable method of contraception, and not become pregnant for at least 56 days after the last vaccination. A woman is considered of childbearing potential unless post-menopausal or surgically sterilized. (Acceptable contraception methods are restricted to intrauterine contraceptive device; oral contraceptives; diaphragm or condom in combination with contraceptive jelly, cream or foam; Norplant® or DepoProvera®) with use of method for a minimum of 30 days prior to vaccination).
• ALT/SGPT, AST/SGOT, and alkaline phosphatase < 3 times institutional upper limit of normal (ULN).
• Urine protein by dipstick or urinalysis < 100mg/dl or <2+ proteinuria
• CBC: Haemoglobin >8 g/dl; White blood cells greater than 2,500 and less than 11,000/mm3; Platelets greater than or equal to 100,000/mm3
• Read, signed and dated informed consent document after being advised of the risks and benefits of the study in a language able to understand, and prior to performance of any study specific procedure
• Cardiac enzymes: within normal range.

Exclusion Criteria:

• Pregnant or breast-feeding women.
• Administration of any HIV nef vaccine or vaccinia immunization within the past 5 years.
• Uncontrolled serious infection i.e. not responding to antimicrobial therapy.
• History of any serious medical condition, which in the opinion of the investigator would compromise the safety of the subject.
• History of or active autoimmune disease. Persons with vitiligo or thyroid disease on thyroid replacement are not excluded.
• History of malignancy, other than squamous cell or basal cell skin cancer, unless there has been surgical excision that is considered to have achieved cure.
• History or clinical manifestation of clinically significant mental illness or haematological, renal, hepatic, pulmonary, central nervous, cardiovascular or gastrointestinal disorders.
• Any condition which might interfere with study objectives or would limit the subject's ability to complete the study in the opinion of the investigator.
• ECG with clinical significance (complete left or right bundle branch block, or sustained ventricular arrythmia, or 2 PVCs in a row, or ST elevation consistent with ischemia).
• History of myocardial infarction, angina, congestive heart failure, cardiomyopathy, stroke or transient ischemic attack, or other heart condition under the care of a doctor.

• 3 or more of the following risk factors:

  1. High blood pressure requiring therapy.
  2. High blood cholesterol (> 300 mg/dl or ratio LDL/HDL ≥ 3) not induced by the HIV therapy.
  3. Diabetes mellitus or high blood sugar.
  4. He/she has a first degree relative (for example mother, father, brother, or sister) who had a heart condition before the age of 50.
  5. Smoking cigarettes now.
• History of chronic alcohol abuse (40g / day for at least 6 month) and/or intravenous drug abuse (within the past 6 month).
• History of allergic disease or reactions likely to be exacerbated by any component of the vaccine.
• History of anaphylaxis or severe allergic reaction.
• Acute disease (a moderate or severe illness with or without a fever) at the time of enrolment.
• Any vaccinations with active vaccines within a period starting 30 days prior to administration of the vaccine and ending 30 days after administration of the study vaccine. Any vaccinations with inactive vaccines within a period starting 14 days prior to administration of the vaccine and ending 14 days after administration of the study vaccine.
• Chronic administration (defined as more than 14 days) of immuno- suppressant or immune-modifying drugs during the study period (Corticosteroid nasal sprays are permissible. Subjects who have used topical and inhaled steroids can be enrolled after their therapy is completed).
• Administration or planned administration of immunoglobulins and/or any blood products during a period starting from 3 months prior to administration of the vaccine and ending at study conclusion.
• Use of any investigational or non-registered drug or vaccine other than the study vaccine within 30 days or 7 half-lives (whichever is longer) preceding the first dose of the study vaccine, or planned administration of such a drug during the study period.