Keratin 8 is a potential self-antigen in the coronary artery disease immunopeptidome: A translational approach.

BACKGROUND: Inflammation is an important risk factor in atherosclerosis, the underlying cause of coronary artery disease (CAD). Unresolved inflammation may result in maladaptive immune responses and lead to immune reactivity to self-antigens. We hypothesized that inflammation in CAD patients would manifest in immune reactivity to self-antigens detectable in soluble HLA-I/peptide complexes in the plasma. METHODS: Soluble HLA-I/peptide complexes were immuno-precipitated from plasma of male acute coronary syndrome (ACS) patients or age-matched controls and eluted peptides were subjected to mass spectrometry to generate the immunopeptidome. Self-peptides were ranked according to frequency and signal intensity, then mouse homologs of selected peptides were used to test immunologic recall in spleens of male apoE-/- mice fed either normal chow or high fat diet. The peptide detected with highest frequency in patient plasma samples and provoked T cell responses in mouse studies was selected for use as a self-antigen to stimulate CAD patient peripheral blood mononuclear cells (PBMCs). RESULTS: The immunopeptidome profile identified self-peptides unique to the CAD patients. The mouse homologs tested showed immune responses in apoE-/- mice. Keratin 8 was selected for further study in patient PBMCs which elicited T Effector cell responses in CAD patients compared to controls, associated with reduced PD-1 mRNA expression. CONCLUSION: An immunopeptidomic strategy to search for self-antigens potentially involved in CAD identified Keratin 8. Self-reactive immune response to Keratin 8 may be an important factor in the inflammatory response in CAD.

Identification of apoB-100 Peptide-Specific CD8+ T Cells in Atherosclerosis.

BACKGROUND: T cells are found in atherosclerotic plaques, with evidence supporting a potential role for CD8+ T cells in atherogenesis. Prior studies provide evidence of low-density lipoprotein and apoB-100 reactive T cells, yet specific epitopes relevant to the disease remain to be defined. The current study was undertaken to identify and characterize endogenous, antigen-specific CD8+ T cells in atherosclerosis. METHODS AND RESULTS: A peptide fragment of apoB-100 that tested positive for binding to the mouse MHC-I allele H2Kb was used to generate a fluorescent-labeled H2Kb pentamer and tested in apoE-/- mice. H2Kb pentamer(+)CD8+ T cells were higher in apoE-/- mice fed an atherogenic diet compared with those fed a normal chow. H2Kb pentamer (+)CD8+ T cells in atherogenic diet-fed mice had significantly increased effector memory phenotype with a shift in Vß profile. H2Kb pentamer blocked lytic activity of CD8+ T cells from atherogenic diet-fed mice. Immunization of age-matched apoE-/- mice with the apoB-100 peptide altered the immune-dominant epitope of CD8+ T cells and reduced atherosclerosis. CONCLUSIONS: Our study provides evidence of a self-reactive, antigen-specific CD8+ T-cell population in apoE-/- mice. Immune modulation using the peptide antigen reduced atherosclerosis in apoE-/- mice.