Vaccination with ApoB100 Derived HLA-A2 Restricted CD8 T Cell Epitopes Did Not Reduce Atherosclerosis in Male LDLrKO hApoB100tg HLA-A2tg Mice

Abstract

CD8 T cells make up a large amount of lymphocytes in atherosclerotic plaques , however their role in atherosclerosis has not been thoroughly studied. Since ApoB100 is a key antigen in atherosclerosis and a plausible vaccination target, we were interested in the role of ApoB100 specific CD8 T cells in atherosclerosis. To be directly relevant for human vaccination HLA-A2 transgenic (HLA-A2) and human ApoB100 transgenic (hApoB100tg) mice were used. HLA-A2 restricted CD8 T cell epitopes derived from human ApoB100 were in silico predicted using The “Proteasomal cleavage/TAP transport/MHC class I combined predictor”of the immune epitope database. Best 6 epitopes were synthesized and binding to HLA-A2 assesed with T2 cell binding assays . To assess induction of peptide specific CD8 T cells, HLA-A2 transgenic mice were vaccinated with peptide pulsed DCs. Peptide recall responses were measured with flow cytometry . To study whether vaccination with ApoB100 derived CD8 T cell epitopes could influence atherosclerosis , male hApoB100tg HLA-A2tg LDLrKO mice (n=10-11) were vaccinated with peptide pulsed bone marrow derived DCs and boosted a week later with with αCD40 and Poly(I:C) and peptides. Animals were fed western type diet for 11 weeks following DC vaccination, after which they were sacrificed to assess aortic root lesion development. All predicted HLA-A2 restricted CD8 T cell epitopes stabilized HLA-A2 in T2 cell binding assays , indicating binding of all peptides to HLA-A2. For 5 of 6 peptides peptide specific recall response were measured a week after vaccination with peptide pulsed DCs. Vaccination with these CD8 T cell epitopes did not lead to reduced atherosclerosis . 10 weeks after the booster vaccination still peptide specific CD8 T cell responses could be detected, indicating that the vaccination was succesful. We have identified 5 HLA-A2 restricted ApoB100 derived CD8 T cell epitopes. Vaccination with these peptides did induce long lasting ApoB100 specific CD8 T cells, however did not affect atherosclerosis in male hApoB100tg HLA-A2tg LDLrKO mice