Targeting infection-specific peptides in immunopeptidomics studies for vaccine target discovery.

Vaccine-elicited T cell responses can contribute to immune protection against emerging infectious disease risks such as antimicrobial-resistant (AMR) microbial pathogens and viruses with pandemic potential, but rapidly identifying appropriate targets for T cell priming vaccines remains challenging. Mass spectrometry (MS) analysis of peptides presented on MHCs can identify potential targets for protective T cell responses in a proteome-wide manner. However, pathogen-derived peptides are outnumbered by self-peptides in the MHC repertoire and may be missed in untargeted MS analyses. Here, we present a novel approach, termed PathMHC, that uses computational analysis of untargeted MS data followed by targeted MS to discover novel pathogen-derived MHC peptides more efficiently than untargeted methods alone. We applied this workflow to identify MHC peptides derived from multiple microbes, including potential vaccine targets presented on MHC-I by human dendritic cells infected with Mycobacterium tuberculosis (Mtb), finding that all Mtb peptides detected in the MHC-I repertoire derived from proteins exported by type VII secretion systems. PathMHC will facilitate antigen discovery campaigns for vaccine development.