Dendritic cells infected with recombinant fowlpox virus vectors are potentand long-acting stimulators of transgene-specific class I restricted T lymphocyte activity

The identification of dendritic cells (DC) as the major antigen-presenting cell type of the immune system, combined with the development of procedures for their ex vivo culture, has opened possibilities for tumour immunothera py based on the transfer of recombinant tumour antigens to DC. It is antici pated that the most effective type of response would be the stimulation of specific, MHC class I restricted cytotoxic T lymphocytes capable of recogni sing and destroying tumour cells. in order to make this approach possible, methods must be developed for the transfer of recombinant antigen to the DC in such a way that they will initiate an MHC class I restricted response. Here, we demonstrate that murine DC infected with a recombinant fowlpox vir us (rFWPV) vector stimulate a powerful, MHC class 1 restricted response aga inst a recombinant antigen. A rFWPV containing the OVA gene was constructed and used to infect the DC line DC2.4. The infected DC2.4 cells were found to stimulate the T-T cell hybridoma line RF33.70, which responds specifical ly to the MHC class I restricted OVA peptide SIINFEKL. The stimulatory abil ity of the rFWPV-infected DC2.4 cells lasted for at least 72 h after infect ion and was eventually limited by proliferation of uninfected cells. By com parison, DC2.4 cells pulsed with synthetic SIINFEKL peptide stimulated RF33 . 70 well initially, but the stimulatory ability had declined to zero by 24 h after pulsing. FWPV infection of DC2.4 up-regulated MHC and costimulator y molecule expression, rFWPV was also found to infect both immature and mat ure human DC derived from cord blood CD34' progenitors and express trangene s for up to 20 days after infection. We conclude that rFWPV shows promise a s a vector for antigen gene transfer to DC in tumour immunotherapy protocol s.