V^LIgMM transgene expression in DC via a GPI-anchor using a novel retroviral vector induces an in vitro autologous T-cell proliferation restricted to MHC class I molecules

Abstract

Introduction: In order to improve the treatment and cure rate of multiple myeloma (MM), immunotherapy is a novel therapeutic approach. Since neoplastic plasma cells do not undergo further hypermutation, the variable region of the immunoglobulin light chain obtained from MM patients (V L IgMM) could serve as a tumor-specific antigen. In addition, dendritic cells (DC) have been identified as potent stimulators of an antigen-specific immune response. Here, we analyze in vitro autologous T-cell proliferation against the V L IgMM on presentation by retrovirally transduced dendritic cells. Materials and methods: Expression of the tumor antigen in DC has been achieved using a novel retroviral vector containing NH 2 (34a.a)DAF-FLAG-V L IgMM-DAF(37a.a)COOH transgene. After cleavage of the amino- and carboxy-terminal hydrophobic domains of DAF, the FLAG-V L IgMM fusion gene is attached to the membrane via a GPI-anchor molecule. Thus, transduced cells can be detected using monoclonal anti-FLAG antibodies. Results: PI-PLC releases cell surface FLAG-antigen from transduced CD34 + cells indicating that the vector directs the fusion protein to the cell surface via GPI-anchor. V L IgMM transgene expression in DC using our retroviral vector elicited an autologous T-cell proliferation restricted to MHC class I molecules. The proliferative response is more prominent in PMA-derived DC compared to cytokine-derived DC indicating that PMA-derived DC are more potent in activating autologous T-cell proliferation. Conclusion: V L IgMM is an immunogenic peptide, which under certain conditions could provide a basis for a V L Ig-based immunotherapy in MM.