ObjectiveTo demonstrate the safety and enhancement of HIV-1-specific immune responses in HIV-infected asymptomatic patients following treatment with retroviral vector (Retrovector®)-transduced autologous fibroblasts (VTAF) expressing HIV-1IIIBEnv/Rev proteins.DesignA non-placebo-controlled, single arm Phase I study.ParticipantsFour HIV-1-seropositive asymptomatic volunteers were selected based on age (18–50 years), CD4/CD3 lymphocyte counts (> 600 × 106/l or > 40%), and positive delayed-type hypersensitivity test to at least one recall antigen.InterventionsPatients were treated at 2-week intervals with a total of three intramuscular injections of irradiated autologous fibroblasts transduced with a molecularly engineered, non-replicating amphotropic murine retrovector encoding the HIV-1IIIBEnv/Rev proteins.Main outcome measuresThe clinical status of patients was assessed by history, physical examination, serum chemistry and hematology, CD4/CD3 lymphocyte counts, HIV viral burden, and monitored throughout the study to detect potentially treatment-induced toxic or unwanted side-effects. In addition, HIV-1-specific cytotoxic T-lymphocyte (CTL) activity was measured to determine the biological activity of VTAF.ResultsNo acute local or systemic adverse events occurred following three injections with VTAF. Furthermore, a statistically significant increase of CD8+ CTL activity against HIV-1IIIBEnv/Rev-expressing targets was observed in peripheral blood mononuclear cells from two out of four patients.ConclusionsThis is the first report of the administration of a gene transfer treatment to HIV-1-infected patients and provides initial support for the safety and biological activity of retrovector-transduced fibroblasts administered to asymptomatic patients. This treatment resulted in the detection of increased HIV-1IIIBEnv/Rev-specific CTL activity in two HIV-seropositive patients and could provide a better understanding of the role of CTL activity in HIV disease progression.