Enrichment of an antigen-specific T cell response by retrovirally transduced human dendritic cells

The superior ability of dendritic cells (DC) in triggering antigen-specific T cell responses makes these cells attractive tools for the generation of antitumor or antiviral immunity. We report here an efficient retroviral tra nsduction system for the introduction of antigens into DC. A retroviral vec tor encoding several CTL epitopes in a string-of-beads fashion in combinati on with the marker gene green fluorescence protein (GFP) was generated. Pol yepitope transduced EBV-LCL could be isolated on the basis of GFP expressio n and were found to be sensitive 60 lysis by antigen-specific cytotoxic T c ells, demonstrating that antigens encoded by the retroviral construct were stably expressed, processed, and presented in the context of HLA class I mo lecules. CD34(+) cells isolated from G-CSF mobilized peripheral blood were transduced with high efficiency (40 60%) with this retroviral construct. Th ese cells could be considerably expanded in vitro and differentiated into m ature DC without loss of the transduced antigen. DC transduced with the pol yepitope constructs were able to mount a CTL response against an influenza epitope in the context of HLA-A2, demonstrating the antigen-specific CTL pr iming capacity of retrovirally transduced DC. Staining of the T cells with tetramers of HLA-A2 and the influenza virus peptide demonstrated a marked a ntigen-specific CTL enrichment after 2 in vitro stimulations using DC trans duced with the polyepitope. However, additional in vitro stimulations of th e T cells with transduced DC did not result in a further enrichment of tetr amer staining cells. (C) 1999 Academic Press.