Identification of novel HLA class I-restricted hepatitis B virus peptides and their modulation by peptide editor...

Hepatitis B virus (HBV) is the leading cause of hepatocellular carcinoma and infections remain a substantial global health problem for which no curative therapy exists. As cytotoxic CD8⁺ T lymphocytes are the principal effectors of natural HBV resolution, there is considerable interest in identification of HBV epitopes that are presented for immune recognition. Current knowledge of HBV-derived peptide presentation to CD8⁺ T cells is largely dominated human leukocyte antigen (HLA)-A*02:01. Our aim was to characterize novel HBV-derived peptides presented on HLA-B and -C molecules, particularly allotypes that are prevalent in regions with high HBV infection rates.

To discover new HBV-derived peptides, immunopeptidomic analysis was performed on cells expressing single HLA class I molecules transduced to express individual HBV proteins. Peptide binding assays were used to validate HLA binding of selected peptides. Additionally, we used immunopeptidomic analysis to determine the effect of the recently discovered major histocompatibility complex class I (MHC-I) peptide editor TAPBPR on presentation of HBV-derived peptides. The results were validated using TAPBPR peptide-exchange assays.

We identified 28 novel HBV-derived peptides presented on HLA class I. Importantly, 22 of the newly discovered HBV-derived peptides were identified on cells expressing HLA-B*08:01, -B*15:03, -B*35:01, -C*06:02 and -C*12:03.

This work presents a substantial expansion of the HLA-B and HLA-C-restricted HBV-derived peptides described in the Immune Epitope Database (IEDB). Additionally, TAPBPR^KO HeLa cells presented four additional and novel HBV-derived peptides, representing the first indication that TAPBPR shapes not only the cellular but also the viral peptide repertoire presented on MHC-I molecules.