Vaccine Can Induce CD4-Mediated Responses to Homocitrullinated Peptides Multiple HLA-Types and Confer Anti-Tumor Immunity.

Homocitrullination is the post translation modification (PTM) of the amino acid lysine to homocitrulline also referred to as carbamylation. This PTM has mainly been studied in relation to autoimmune diseases including rheumatoid arthritis. Homocitrullination of lysines alters their charge which can lead to generation of neoepitopes that are differentially presented by MHC-II and induce modification-specific immune responses. Homocitrullination is often considered a process which triggers autoimmune disease by bypassing self-tolerance however, we suggest that homocitrullination may also have an alternative role in immune responses including protection against cancer. Here we demonstrate that immune responses to homocitrullinated peptides from three different proteins can be induced multiple HLA-types. Immunization of Balb/c or HLA-transgenic DR4 and DR1 mice can induce modification-specific CD4 mediated IFNγ responses. Healthy human donors show a clear repertoire for the homocitrullinated Vimentin peptide (Vim116-135), with modification-specific and oligoclonal responses. Importantly, homocitrulline specific Vim116-135Cyk8 371-388 and Aldo 140-157 responses are able to confer an anti-tumor effect in the murine B16 melanoma model. The Vim116-135 anti-tumor response was dependent upon tumor expression of MHC-II suggesting the direct recognition of PTMs on tumor is an important anti-tumor mechanism. Cancer patients also have a CD4 repertoire for Vim116-135. Together these results suggest that homocitrulline-specific immune responses can be generated in healthy mice and detected in human donors through a variety of HLA-restrictions. Immunization can induce responses to Vim116-135Aldolase 140-157 and Cyk8 371-388 which provide anti-tumor therapy across several HLA-types. Our results advance our understanding of homocitrulline-specific immune responses, with implications for a number of fields beyond autoimmunity, including tumor immune surveillance.