Proteasome-catalyzed peptide splicing (PCPS) generates peptides that are
presented by MHC class I molecules, but because their identification is
challenging, the immunological relevance of spliced peptides remains unclear.
Here, we developed a reverse immunology-based multi-level approach to identify
proteasome-generated spliced epitopes. Applying this strategy to a murine
Listeria monocytogenes infection model, we identified two spliced epitopes
within the secreted bacterial phospholipase PlcB that primed antigen-specific
CD8+ T cells in L. monocytogenes-infected mice. While reacting to the spliced
epitopes, these CD8+ T cells failed to recognize the non-spliced peptide parts
in the context of their natural flanking sequences. Thus, we here show that
PCPS expands the CD8+ T cell response against L. monocytogenes by exposing
spliced epitopes on the cell surface. Moreover, our multi-level strategy opens
up opportunities to systematically investigate proteins for spliced epitope
candidates and thus strategies for immunotherapies or vaccine design