Priming specific, murine CD8+ T cell responses by complexes of cationic/ antigenic fusion peptides with nucleic acids
Final Report Abstract
Cationic peptide motifs are 4 to 30 residue long clusters of positively charged arginine (R) or lysine (K) side groups that are abundantly present in some viral and eukaryotic proteins. Cationic peptides deliver large proteins or immune-stimulating oligonucleotides into cells and thus represent a novel, potentially universal delivery system for proteins and nucleotides into the cytosol in bioactive form. We used the binding activity of positively charged antigenic/cationic fusion peptides to negatively charged nucleotides to form rigid complexes and tested these complexes in vaccination experiments to induce monospecific CDS T cell responses in murine model systems. I analyzed how changes in the different components (cationic sequences; MHC class I binding, antigenic epitopes, immunostimulating nucleic acids) of these complexes influence their immunogenicity for CD8 T cells. I showed that the cationic domain but not its position relative to the epitope influences the antigenicity of the formulation. Fusion peptides containing, in addition to the antigenic peptide, >7 cationic residues (irrespective of the R/K composition) most efficiently supported priming of CDS T cell responses. Many human (HLA-A2) and murine (Ld, Kd, Kb, Db) class l-binding epitopes were tested as cationic, antigenic peptide vaccines, and all epitopes primed specific CDS T cell responses. Large antigenic/cationic peptide vaccines (80 residues) efficiently stimulated CDS T cell as well as humoral B cell responses, indicating that multispecific immune responses can be primed by this technique. Furthermore, antigenic/cationic peptides complexed with different TLR-9- or TLR-7/8- stimulating nucleic adds efficiently induced CDS T cell responses. Thus, we were able to define a standardized method to deliver cationic peptide vaccines: antigenic sequences were fused with the HlV-taUs- 57 sequence and complexed with CpG ODN-1826. Cationic peptide/ODN complexes were successfully used to induce therapeutic CD8 T cell responses in a preclinical mouse model of chronic HBV infection. Peptide- (but not DNA-) based vaccination primed HBsAg (Kb/Si9o-i97)-specifrc CDS T cell immunity in 1.4HBV-Smut B6 mice, and these T cells could suppress HBV replication in the liver. Cationic, antigenic peptide vaccines complexed to ODN are hence an attractive option to prime monospecific CDS T cell immunity in a tolerogenic milieu that can deliver therapeutic (anti-viral) effects to antigenexpressing hepatocytes. Similarly, insulin-specific cationic peptide/nucleotide complexes primed autoreactive CDS T cell responses and diabetes in RIP-B7.1 mice. In this diabetes model we designed disease-enhancing epitope variants of the insulin autoantigen. Cationic, antigenic peptides hence allowed us to characterize the fine specificity of monospecific CDS T cell responses in this preclinical diabetes model.
Publications
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Dikopoulos N., Riedl P., Schirmbeck R. and J. Reimann. 2004. Novel peptide-based vaccines efficiently prime murine "help"-independent CD8 T cell responses in the liver. Hepatology 40:300-309.
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Riedl P., Reimann J. and Schirmbeck R. 2006. Complexes of DNA vaccines with cationic, antigenic peptides are potent, polyvalent CDS T cell-stimulating immunogens Methods Mol Med 127: 159-169.
