30 treated chronic HIV-1 infected patients with CD4+ cell counts above 450 cells/ mm3 will be randomized 1:2 to receive placebo (n=10) or vaccine (n=20) at week 0, 4 and 16 and will be observed at the Investigation Unit of the study site for one hour following vaccination. At week 24 they will stop their HAART until the end of the study.