Abstract
OBJECTIVES/SPECIFIC AIMS: The study aimed at assessing whether M. bovis BCG infection and inflammation exacerbates the development of atherosclerosis in Ldlr-/- mice. METHODS/STUDY POPULATION: Twelve-week old male Ldlr-/- mice (n=10) were infected with M. bovis BCG (0.3–3.0x10^6 colony-forming units (CFUs)) via the intranasal route, to simulate a natural respiratory route of infection. Mice were subsequently fed a western-type diet (WD) containing 21% fat and 0.2% cholesterol for 16 weeks. Age-matched uninfected Ldlr-/- mice (n=10) fed with an identical WD served as controls. Mice were euthanized after 16 weeks of WD to examine atherosclerotic lesions in aortic root sections and en face aorta using Oil Red O staining. Plasma cholesterol and triglyceride levels were measured by enzymatic assays and lipoprotein distribution was assessed using fast protein liquid chromatography. Because of the important role of T cells and monocytes in atherosclerosis development, we assessed these cell subsets in blood using flow cytometry at 8 and 16 weeks. Experiments were conducted in duplicate. We used unpaired Student’s t-test for group comparisons of numeric variables and flow cytometry data. RESULTS/ANTICIPATED RESULTS: M. bovis BCG infection significantly increased atherosclerotic lesions in en face aorta (plaque size per aorta area ratio; 0.15±0.13 vs. 0.06±0.02; P<0.01), but not in the aortic root. There were no significant differences in plasma cholesterol (1,160 mg/dL vs. 1,278 mg/dL; P = 0.36), triglycerides (340 mg/dL vs. 413 mg/dL; P = 0.28), or lipoprotein profiles between infected vs. uninfected mice at 16 weeks. M. bovis BCG increased circulating T lymphocytes (1,490 cells/uL vs. 1,227 cells/uL; P = 0.03) and monocytes (901 cells/uL vs. 414 cells/uL; P<0.01) within 8 weeks post-infection. When we assessed T lymphocyte subsets, M. bovis BCG infection increased total CD4+ T cell counts (556 cells/uL vs. 416 cells/uL; P<0.01) but not CD8+ T cells. No differences in the proportion of CD44+CD25+ activated T lymphocytes were noted between groups. When we assessed monocyte subsets, M. bovis BCG infection increased the numbers of Ly6Chigh (709 cells/uL vs. 362 cells/uL; P<0.01) and Ly6Clow (145 cells/uL vs. 35 cells/uL; P<0.01) monocytes. Infection was associated with an increased proportion of Ly6Clow monocytes at week 8 (17% vs. 8%; P<0.01) and week 16 (19% vs. 5%; P<0.01), compared to uninfected mice. DISCUSSION/SIGNIFICANCE OF IMPACT: M. bovis BCG infection increased the extent of atherosclerosis formation in the aortas of WD-fed hyperlipidemic Ldlr-/- mice after 16 weeks. Lipid profiles were similar between infected and uninfected mice, and therefore do not explain the observed differences in atherosclerosis. Compared to uninfected controls, M. bovis BCG-infected mice exhibited increased CD4+ T cell and monocyte driven inflammation. Interestingly, M. bovis BCG-infected mice had a higher proportion of non-classical Ly6Clow monocytes, suggesting a pro-atherogenic contribution of these cells in our model. Overall, our results support a pathogenic role of mycobacterial infection in atherosclerosis development and ASCVD.