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42 residues of the amino terminus of alpha' chain fragment of C3b enhances cross-presentation of exogenous peptides antigens

Objective To assess whether the 42 residues of the amino terminus of alpha′ chain fragment of C3b(C3b_ AN42 ) can enhance cross-presentation of exogenous peptides antigens. Methods Three peptides, OVA CTL epitope(257-264), C3b_ AN42 -OVA_ 257-264 and OVA_ 253-266 , were synthesized, and were purified by analytical and preparative HPLC and then characterized by mass spectrometry. After that, peptides were added into murine macrophage cell line ANA-1, TAP-deficient cell(RMA-S)in different circumstances. Monoclonal antibody specific for OVA_ 257-264 /K b, 25-D1.16 respectively was used for counting peptide-classⅠ complexes presented on the cell surface. Results Peptide C3b_ AN42 -OVA_ 257-264 is easier to be presented than OVA_ 253-266 . C3b_ AN42 -mediated cross presentation was not affected by TAP molecule, but was influenced by temperature and NH_4Cl. The stability of peptide-MHC complex was increased by C3b_ AN42 -mediated cross presentation. Conclusion C3b_ AN42 can enhance cross-presentation of exogenous peptides antigens and C3b_ AN42 -mediated delivery of CTL peptides into APCs may prolong antigen presentation. These findings have implications for the design of peptide and protein-based vaccines.