The purpose of this trial is to evaluate the safety and immunogenicity of the therapeutic vaccine candidate VAC-3S in HIV-1 infected patients under AntiRetroviral Therapy (ART) with undetectable viral loads.

Inclusion Criteria:

• HIV-1 infected patient
• Age between 18 and 55 years
• ART (AntiRetroviral Therapy) initiation 1 year ago
• Plasma HIV RNA below 50 copies per ml on three sequential occasions including V-1 in the past 12 months
• CD4 T cell count above or equal to 200 cells per mm3,
• Nadir CD4 T cell count above or equal to 100 cells per mm3,
• Contraception in women with child-bearing potential

Exclusion Criteria:

• Any ART change within a month preceding screening.
• Chronic active liver disease, HIV-Hepatitis Coinfection.
• Immunotherapy in the past year, immunosuppressive treatment within the past month.
• History of auto-immune disease