Carcinoembryonic antigen (CEA) is well-known soluble tumor marker frequently detectable in peripheral blood of carcinoma patients and considered as good target for antigen-specific immunotherapy. In this study, we used a replication-deficient adenovirus containing CEA to study CTL induction in vitro after adenovirus-mediated gene transfer into DC.

DC were obtained from mouse bone marrow and cultured with IL-4 and GM-CSF. For measuring CTL activity, splenocytes were harvested from the mice, which were immunized with DC that had been infected AdV-CEA or pulsed with CEA peptide. Untreated DC was used as a control. Splenocytes were re-stimulated in vitro with DC pulsed with CEA peptide for 7 days and CTL activity with CEA peptide-pulsed EL-4 cells were assessed in a standard ⁵¹Cr-release assay. The frequencies of antigen-specific cytokine-secreting T cell were determined with mIFN-γ ELISPOT.

DC infected with recombinant adenovirus expressing CEA induced CEA-specific CTL responses in vivo. Splenocyte induced from mice immunized with AdV-CEA-infected DC increase in the number of IFN-γ secreting T cells compared with those from mice immunized with CEA peptide-pulsed DC.

These results suggested that DC infected with recombinant adenovirus has advantages over other forms of vaccination and could provide an alternative approach vaccination therapies.