V-1 Immunitor (V1) is a therapeutic vaccine comprising pooled HIV antigens formulated into an oral pill. Recent V1 studies demonstrated body weight gain, increase in CD4 and CD8 cells, decrease in viral load, and improved survival of end-stage AIDS patients. The potential of V1 as a prophylactic vaccine has been evaluated in a phase II placebo-controlled trial on 35 volunteers. Twenty HIV-negative volunteers who received V1 b.i.d. for 4 weeks had gained 28.2 and 17.5% in absolute CD4 (825 versus 1058; P=0.007) and CD8 (597 versus 702; P=0.013) cells, while lymphocytes in placebo group did not increase, suggesting that CD4 and CD8 counts may become an easily measurable immune correlate of the efficacy of AIDS vaccines. V1 does not appear to induce HIV-specific antibodies as orally administered immunogens usually produce cell-mediated but not systemic humoral response. V1 as a preventive oral vaccine targeting cellular and mucosal immunity deserves further evaluation.