Although immunization with MHC class II-restricted ApoB peptides has been shown to be atheroprotective, the mechanism is unclear. Here, we investigated CD4+ T cell populations in immunized atherosclerotic mice. Peptides (16-mers) from mouse ApoB, the core protein of low-density lipoprotein (LDL), were screened for binding to I-Ab by computer prediction and confirmed by radiolabeled peptide competition. Three new peptides, P101 (FGKQGFFPDSVNKALY, 5.5 nM IC50), P102 (TLYALSHAVNSYFDVD, 6.8 nM), and P103 (LYYKEDKTSLSASAAS, 95 nM) were tested in an atherosclerosis model (Apoe-/- mice on western diet). Immunization with each of the three peptides (1x in complete Freund's adjuvant s.c, 4 x in incomplete Freund's adjuvant i.p.), but not with adjuvant alone showed significantly reduced atherosclerotic plaques in the aortic root by serial sections and in the whole aorta by en face staining. There were no differences in body weight, LDL cholesterol or triglycerides. Peritoneal leukocytes from ApoB peptide-immunized mice, but not control mice secreted significant amounts of IL-10 (150 pg/ml). Flow cytometry showed that peptide immunization induced IL-10 in 10% of peritoneal CD4+ T cells, some of which also expressed CCR5. Vaccination with ApoB peptides expanded peritoneal FoxP3+ regulatory CD4+ T cells and more than tripled the number of CCR5+FoxP3+ cells. Similar trends were also seen in the draining mediastinal lymph nodes, but not in the non-draining inguinal lymph nodes. We conclude that vaccination with MHC class II-restricted autologous ApoB peptides induces Tregs and IL-10, suggesting a plausible mechanism for atheroprotection.
- apolipoprotein B-100
- Copyright © 2017, American Journal of Physiology-Heart and Circulatory Physiology