Immunopeptidome Landscape During Infection in Mice.

Mouse bone marrow-derived dendritic cells (BMDCs) were infected in vitro with the recombinant strain. The immunopeptidome of , which presented peptides bound to MHC class II molecules on their surface, was isolated and characterized. BMDCs infected with were subjected to hypotonic lysis. The associated immunopeptidome was then isolated and characterized using co-immunoprecipitation (Co-IP) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). A total of 289 MHC-II-bound peptide sequences were identified, mapping to 183 distinct proteins. We successfully define the immunopeptidome presented by MHC-II on infected BMDCs. The source proteins of these peptides exhibited significant abundance and functional, structural, and pathway diversity. This study demonstrates that during antigen presentation by antigen-presenting cells (APCs), peptides presented by MHC-II originate from a broad repertoire of proteins, not limited to surface antigens. This complex immunopeptidome, shaped by active selection mechanisms, provides diverse targets for host immune recognition. These findings establish a foundation for further investigation into the transfer of comprehensive immune information between immune cells and the elicitation of immune responses. This work also paves the way for identifying specific T-cell receptors involved in recognition and immune activation, thereby facilitating the analysis of adaptive immunity's molecular basis. Furthermore, this study provides an innovative approach for immunopeptidome analysis, providing a crucial theoretical foundation for developing novel subunit vaccines.