Regulatory CD4 + T Cells Recognize Major Histocompatibility Complex Class II Molecule–Restricted Peptide Epitopes of Apolipoprotein B

• DOI: 10.1161/circulationaha.117.031420
• Publication Date: 2018-03-27T09:25:14Z
• Authors: Takayuki Kimura; Kouji Kobiyama; Holger Winkels; Kevin Tse; Jacqueline Miller; Melanie Vassallo; Dennis Wolf; Christian Ryden; Marco Orecchioni; Thamotharampillai...; Marc K. Jenkins; Eddie A. James; William W. Kwok; David B. Hanna; Robert C. Kaplan; Howard D. Strickler; Helen G. Durkin; Seble G. Kassaye; Roksana Karim; Phyllis C. Tien; Alan L. Landay; Stephen J. Gange; John Sidney; Alessandro Sette; Klaus Ley
• Keywords: Male; 0301 basic medicine; Aging; Mice, Knockout, ApoE; T-Lymphocytes; Freund's Adjuvant; Epitopes, T-Lymphocyte; Clinical sciences; Cardiorespiratory Medicine and Haematology; Cardiovascular; Inbred C57BL; Lymphocyte Activation; regulatory T cells; Epitopes; Mice; Immunologic; 2.1 Biological and endogenous factors; Aetiology; Aorta; Plaque; Atherosclerotic; Vaccination; Regulatory; 3. Good health; Heart Disease; Apolipoprotein B-100; Public Health and Health Services; Female; ApoE; Knockout; Immunology; Clinical Sciences; Aortic Diseases; Cardiovascular medicine and haematology; Vaccine Related; apoB-100; 03 medical and health sciences; Adjuvants, Immunologic; Animals; Humans; Adjuvants; Apolipoproteins B; Biomedical and Clinical Sciences; Animal; Prevention; Histocompatibility Antigens Class II; vaccination; Atherosclerosis; Peptide Fragments; Mice, Inbred C57BL; Disease Models, Animal; Good Health and Well Being; T-Lymphocyte; Cardiovascular System & Hematology; Disease Models; antigen specificity; Immunization; atherosclerosis; Sports science and exercise; Epitope Mapping

Background:

CD4 + T cells play an important role in atherosclerosis, but their antigen specificity is poorly understood. Immunization with apolipoprotein B (ApoB, core protein of low density lipoprotein) is known to be atheroprotective in animal models. Here, we report on a human APOB peptide, p18, that is sequence-identical in mouse ApoB and binds to both mouse and human major histocompatibility complex class II molecules.

Methods:

We constructed p18 tetramers to detect human and mouse APOB-specific T cells and assayed their phenotype by flow cytometry including CD4 lineage transcription factors, intracellular cytokines, and T cell receptor activation. Apolipoprotein E–deficient (

Apoe −/−

) mice were vaccinated with p18 peptide or adjuvants alone, and atherosclerotic burden in the aorta was determined.

Results:

In human peripheral blood mononuclear cells from donors without cardiovascular disease, p18 specific CD4 + T cells detected by a new human leukocyte antigen-antigen D related-p18 tetramers were mostly Foxp3 + regulatory T cells (Tregs). Donors with subclinical cardiovascular disease as detected by carotid artery ultrasound had Tregs coexpressing retinoic acid-related orphan receptor gamma t or T-bet, which were both almost absent in donors without cardiovascular disease. In

Apoe −/−

mice, immunization with p18 induced Tregs and reduced atherosclerotic lesions. After peptide restimulation, responding CD4 + T cells identified by Nur77-GFP (green fluorescent protein) were highly enriched in Tregs. A new mouse I-A b -p18 tetramer identified the expansion of p18-specific CD4 + T cells on vaccination, which were enriched for interleukin-10–producing Tregs.

Conclusions:

These findings show that APOB p18–specific CD4 + T cells are mainly Tregs in healthy donors, but coexpress other CD4 lineage transcription factors in donors with subclinical cardiovascular disease. This study identifies ApoB peptide 18 as the first Treg epitope in human and mouse atherosclerosis.