Immunization of hypercholesterolemic mice with selected apoB-100 peptide antigens reduces atherosclerosis but the precise immune mediators of athero-protection remain unclear. In this study we show that immunization of apoE (-/-) mice with p210, a 20 amino acid apoB-100 related peptide, reduced aortic atherosclerosis compared with PBS or adjuvant/carrier controls. Immunization with p210 activated CD8+ T cells, reduced dendritic cells (DC) at the site of immunization and within the plaque with an associated reduction in plaque macrophage immunoreactivity. Adoptive transfer of CD8+ T cells from p210 immunized mice recapitulated the athero-protective effect of p210 immunization in naïve, non-immunized mice. CD8+ T cells from p210 immunized mice developed a preferentially higher cytolytic response against p210-loaded dendritic cells in vitro. Although p210 immunization profoundly modulated DCs and cellular immune responses, it did not alter the efficacy of subsequent T cell dependent or independent immune response to other irrelevant antigens. Our data define, for the first time, a role for CD8+ T cells in mediating the athero-protective effects of apoB-100 related peptide immunization in apoE (-/-) mice.

Poly-IgM treatment reduced aortic and accelerated carotid atherosclerosis in apoE-/- mice in association with increased anti-oxLDL IgG titers, and reduced number and proliferative function of splenic CD4(+) T cells. Our study identifies a novel athero-protective and immunomodulatory role for non-immune polyclonal IgM.

BackgroundThe lipid milleu exacerbates the inflammatory response in atherosclerosis but its effect on T cell mediated immune response has not been fully elucidated. We hypothesized that lipid lowering would modulate T cell mediated immune function.Methods and ResultsT cells isolated from human PBMC or splenic T cells from apoE-/- mouse had higher proliferative response to T cell receptor (TCR) ligation in medium supplemented with 10% fetal bovine serum (FBS) compared to medium with 10% delipidated FBS. The differences in proliferation were associated with changes in lipid rafts, cellular cholesterol content, IL-10 secretion and subsequent activation of signaling molecule activated by TCR ligation. Immune biomarkers were also assessed in vivo using male apoE-/- mice fed atherogenic diet (AD) starting at 7 weeks of age. At 25 weeks of age, a sub-group was switched to normal diet (ND) whereas the rest remained on AD until euthanasia at 29 weeks of age. Dietary change resulted in a lower circulating level of cholesterol, reduced plaque size and inflammatory phenotype of plaques. These changes were associated with reduced intracellular IL-10 and IL-12 expression in CD4+ and CD8+ T cells.ConclusionOur results show that lipid lowering reduces T cell proliferation and function, supporting the notion that lipid lowering modulates T cell function in vivo and in vitro.

Auto-immunity is believed to contribute to inflammation in atherosclerosis. The antimicrobial peptide LL-37, a fragment of the cathelicidin protein precursor hCAP18, was previously identified as an autoantigen in psoriasis. Given the reported link between psoriasis and coronary artery disease, the biological relevance of the autoantigen to atherosclerosis was tested in vitro using a truncated (t) form of the mouse homolog of hCAP18, CRAMP, on splenocytes from athero-prone ApoE(-/-) mice. Stimulation with tCRAMP resulted in increased CD8+ T cells with Central Memory and Effector Memory phenotypes in ApoE(-/-) mice, differentially activated by feeding with normal chow or high fat diet. Immunization of ApoE(-/-) with different doses of the shortened peptide (Cramp) resulted in differential outcomes with a lower dose reducing atherosclerosis whereas a higher dose exacerbating the disease with increased neutrophil infiltration of the atherosclerotic plaques. Low dose Cramp immunization also resulted in increased splenic CD8+ T cell degranulation and reduced CD11b+CD11c+ conventional dendritic cells (cDCs), whereas high dose increased CD11b+CD11c+ cDCs. Our results identified CRAMP, the mouse homolog of hCAP-18, as a potential self-antigen involved in the immune response to atherosclerosis in the ApoE(-/-) mouse model.

BackgroundT 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 ResultsA 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 Vβ 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.ConclusionsOur 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.