This application proposes research designed to provide solid mechanistic underpinnings for immunotherapy and vaccination to prevent and treat atherosclerosis. Vaccination with MHC-II restricted peptide epitopes from apolipoprotein B (ApoB) ameliorates atherosclerosis by inducing ApoB-specific regulatory CD4 T cells (Tregs). I have developed reagents (tetramers and dextramers) to detect and isolate these ApoB-specific Tregs at the single cell level in mice and humans. The proposed work has a T cell aspect, currently supported by R01 HL121697 (2014-2018), and a vascular macrophage aspect, currently supported by R01 HL115232 (2012- 2022). To gain better mechanistic insight, I propose to adoptively transfer ApoB-specific Tregs (if necessary expanded in Rag2-/- mice) into recipient mice and measure atherosclerosis. I will also transfer ApoB peptide- specific antibodies to formally test possible antibody effects, and test the role of B cells in two B cell-deficient mouse lines. I will study changes in functions of vascular macrophages in vivo after vaccination. To improve the vaccine efficacy, I propose to test vaccine formulations similar to what would be used clinically, test the atherosclerosis vaccines in two other mouse models of atherosclerosis (Apoe-/- on chow diet, Ldlr-/- on high fat diet), optimize the vaccination protocol, and add low-dose IL-2 to stabilize Tregs. To discover how and why Tregs switch to effector T cells, I will use FoxP3 (the Treg defining transcription factor) lineage tracker mice. TCR-Seq will test the hypothesis that the apparent switch is caused by an outgrowth of a minor population of pro-inflammatory ApoB-specifc CD4 T cells. To test cell-exogenous factors, I will incubate ApoB-specific CD4 T cells with explanted normal or atherosclerotic aortas, and measure epigenetic changes by DNA and histone methylation around the FoxP3 locus. To prepare for translating the vaccine into humans, I propose more human work, including mass cytometry (CyTOF) on peripheral blood mononuclear cells (PBMCs) with 42- ?color? panels. Barcoded scRNA-Seq to obtain single cell transcriptomes will define the cell types more deeply. I propose to expand the current clinical data set (all women, most HIV+) to both genders and HIV-. When this work is completed, we will have a good understanding how atherosclerosis vaccination works. We will have extensive human data for the phenotype of ApoB-specific CD4 T cells in PBMCs collected from cardiovascular disease cases and controls.
Atherosclerosis is a chronic inflammatory disease of the artery walls that leads to heart attacks and strokes. We discovered in mouse models that vaccination with short sequences of APOB, a protein associated with cholesterol transport, can reduce the inflammation in the artery wall. The proposed work will lay the mechanistic groundwork for developing an atherosclerosis vaccine that is expected to benefit tens of millions of people in the US and billions of people worldwide.
