Longitudinal follow-up of cellular and humoral immunity induced by recombinant adenovirus-mediated gene therapy in cancer patients

Replication-defective adenoviruses are arousing growing interest as both gene therapy and vaccine vectors. In a phase I clinical trial designed to evaluate the feasibility and tolerance of recombinant adenovirus (rAd)-mediated gene transfer, we previously demonstrated that a single intratumoral injection of 10⁹ PFU of rAd encoding the β-galactosidase protein (Ad-β-Gal) induced strong short-term (1-3 months) humoral, helper (Th1 type) and cytotoxic T cell responses specific for the transgene product in patients with advanced lung cancer. The purpose of the present study was to evaluate the persistence of long-lasting immunity to the transgene protein and in parallel, to assess patient immunocompetence revealed by responses to recall antigens (tetanus toxoid, purified protein derivative), viral pathogens (Epstein-Barr virus, influenza virus), and allogeneic antigens in mixed lymphocytic reactions. The β-Gal-specific proliferative response declined rapidly in patients with progressive disease, as did responses to the other antigens. In contrast, a long-lasting proliferative response to β-gal was maintained in an immunocompetent patient in complete remission 2 years after an injection of 10⁸ PFU of Ad-β-Gal. Anti-β-Gal humoral (IgG and IgA) responses persisted notably, as did responses to TT and poliomyelytic antigens. While T cell effector cytotoxic responses specific for the viral peptides plummeted, the frequency of anti-β-Gal CTL precursors remained particularly high, thus attesting to major immunization. Despite the impact of both advanced disease and chemotherapy on immunocompetence, we show the long-term persistence of immunity to the transgene protein veetorized by rAd.