Multi-level Strategy for Identifying Proteasome-Catalyzed Spliced Epitopes Targeted by CD8+ T Cells during Bacterial Infection

• Published in: Cell reports (Cambridge) 2017-08, Vol.20 (5), p.1242-1253
• Main Authors: Platteel, Anouk C.M., Liepe, Juliane, Textoris-Taube, Kathrin, Keller, Christin, Henklein, Petra, Schalkwijk, Hanna H., Cardoso, Rebeca, Kloetzel, Peter M., Mishto, Michele, Sijts, Alice J.A.M.
• Format: Article
• Language: English
• Subjects: Animals; antigen presentation; CD8-Positive T-Lymphocytes - immunology; CD8-Positive T-Lymphocytes - pathology; Epitopes, T-Lymphocyte - genetics; Epitopes, T-Lymphocyte - immunology; in silico analysis; intracelllular bacteria; Listeria monocytogenes; Listeria monocytogenes - immunology; Listeriosis - genetics; Listeriosis - immunology; Listeriosis - pathology; Mice; peptide splicing; proteasome; Proteasome Endopeptidase Complex - genetics; Proteasome Endopeptidase Complex - immunology
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2017.07.026

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. [Display omitted] •Development of in-silico-based, multi-level strategy for identifying spliced epitopes•Developed strategy identifies two spliced bacterium-derived CD8+ T cell epitopes•Proteasome-catalyzed peptide splicing increases the pathogen-derived peptide pool Proteasomes both degrade proteins and ligate generated products, creating “spliced peptides” composed of distant protein parts. Platteel et al. now describe a multi-level strategy for identifying proteasome-generated spliced T cell epitopes. This work suggests ways of defining spliced epitopes within any antigen of interest and to determine their immunological relevance.