CpG-DNA activates in vivo T cell epitope presenting dendritic cells to trigger protective antiviral cytotoxic T cell responses

MHC class I-restricted T cell epitopes lack immunogenicity unless aided by IFA or CFA, In an attempt to circumvent the known inflammatory side effects of IPA and CFA, we analyzed the ability of immunostimulatory CpG-DNA to ac t as an adjuvant for MHC class I-restricted peptide epitopes, Using the imm unodominant CDS T cell epitopes, SIINFEKL from OVA or KAVYN-FATM (gp33) fro m lymphocytic choriomeningitis virus glycoprotein, we observed that CpG-DNA conveyed immunogenicity to these epitopes leading to primary induction of peptide-specific CTL, Furthermore, vaccination with the lymphocytic choriom eningitis virus gp33 peptide triggered not only CTL but also protective ant iviral defense. We also showed that MNC class I-restricted peptides are con stitutively presented by immature dendritic cells (DC) within the draining lymph nodes but failed to induce CTL responses. The use of CpG-DNA as an ad juvant, however, initiated peptide presenting immature DC progression to pr ofessional licensed APC, Activated DC induced cytolytic CD8 T cells in wild -type mice and also mice deficient of Th cells or CD40 ligand, CpG-DNA thus incites CTL responses toward MHC class I-restricted T cell epitopes in a T h cell-independent manner. Overall, these results provide new insights into CpG-DNA-mediated adjuvanticity and may influence future vaccination strate gies for infectious and perhaps tumor diseases.