Stimulation of Anti-Tumor Immunity Using Dendritic Cells Transduced with Fowl Pox Vector Expressing MUC-1 and Costimulatory Molecules (PANVAC-F).

In pre-clinical models, vaccination with attenuated vaccinia and fowl pox virus expressing tumor antigens and costimulatory molecules (CD54/ICAM-1; CD58/LFA-1 and CD80/B7.1-TRICOM) potently stimulates anti-tumor immune responses. However, vaccine efficacy may be limited by intrinsic deficiencies of native dendritic cells (DC) populations in patients with malignancy that are required to process and present the virally introduced antigens. An alternative strategy involves the transduction of ex vivo generated activated DCs. We have examined the capacity of DCs transduced with a fowl pox vector expressing MUC-1, CEA, and TriCOM (PANVAC-F) to elicit antigen specific responses and expand activated as compared to regulatory T cell populations. Partially mature DCs were generated from leukopak preparations obtained from normal volunteers by culturing adherent peripheral blood mononuclear cells for 5 days with GM-CSF and IL-4. DCs were transduced with PANVAC-F vector and matured with either TNFa or the combination of PG-E2, TNFa, IL-6 and IL-1b. In 5 serial studies, transduction with PANVAC-F resulted in mean MUC1 expression in 64.6% (SEM: ±1.6) of cells with a mean fluorescent intensity (MFI) of 249.8 (SEM: ±45.7). In addition, transduced DCs also demonstrated high levels of expression of class II (99%; MFI:250), CD54 (98.4%;MFI:516), CD58 (98.8%;MFI:155) and CD80 (78.2%; MFI:115). Of note, transduced DCs demonstrated higher levels of the maturation marker CD83 (40.3%; SEM: ±1.6, n=3) as compared to untransduced DCs 19.7% (SEM: ±2.9) (p=0.02) suggesting that transduction enhanced DC maturation and activation. Transduced DCs matured with PGE2, TNFa, IL-6 and IL-1b as compared to TNFa alone demonstrated higher levels of CD83 and CCR7 and a more stable phenotype following withdrawal of cytokine support. To assess the ability of PANVAC-F to stimulate tumor antigen specific responses, the presence of T cells binding the MUC-1 specific tetramer was quantified following stimulation of autologous T cells derived from HLA*0201 healthy donors. An increase in CD8+ and MUC1+ cells were observed (8.3%) with stimulation with PANVAC-F transduced DCs as compared to untransduced DCs (2.5%). The capacity of DCs transduced with PANVAC-F to stimulate interferon gamma producing activated T cells, as compared to CD4+/CD25+/Foxp3+ regulatory T cell populations is being assessed. In summary, PANVAC-F transduced DCs stimulate expansion of antigen specific T cell populations suggesting their potential role as tumor vaccines for MUC-1/CEA expressing tumors. We are initiating a trial for patients with ovarian carcinoma in early (marker only) relapse in which patients will be randomized to undergo serial vaccination with PANVAC-V/PANVAC-F or DCs transduced with PANVAC-F. The capacity to generate anti-tumor immunity in vivo will be assessed as a primary endpoint.