Epitope-flanking amino acid substitutions facilitate enhanced antigen processing and improve anti-tumoral T cell immunity

Hepatocellular carcinoma (HCC) is a major leading cause of cancer-related death and the fifth most common kind of cancer worldwide.

Anti-tumoral immune responses are often hampered by reduced antigen presentation of cancer epitopes. Antigen processing is largely governed by amino acids that flank the putative epitopes, thereby controlling presentation of T cell targets on the surface of cancer cells.

Here, we applied systematic testing of amino acid substitutions that flank a defined CD8 T cell epitope to enhance surface antigen presentation on mouse MHC class I molecules.

Liver cancer cell line Hep55.1C was transduced with retrovirus containing different gene cassettes encoding for tumor neoepitopes that were flanked by either wild-type or processing-optimized sequences. Mice bearing subcutaneous tumors that contained processing-optimized sequences showed higher endogenous specific CD8 T cell responses and had longer survival than mice with wild-type sequences expressed in the tumor.

Utilizing a rapid heterologous T cell vaccination regimen, consisting of long polypeptides-pulsed dendritic cells for priming and costimulatory CD40 antibody, TRL3 agonist polyI:C and peptide for boosting, resulted in higher frequencies of specific CD8 T cells when processing-optimized sequences were used, compared to the wild-type polypeptides.

These findings allowed us to define patterns that could improve antigen processing and recognition by anti-tumoral CD8 T cells, thus contributing to tumor growth control. In the upcoming experiments, we will validate the processing-optimized peptide sequence using defined human antigens, which might have implications for human T cell vaccination strategies.

Publication History

Article published online:
20 January 2025