Effects of Mycobacterium tuberculosis HSP65 on Treg/Th17 immune balance in ApoE-knockout mice

To investigate the effects of Mycobacterium tuberculosis heat shock protein 65(HSP65)on Treg/Th17 immune balance in ApoE-knockout(ApoE^-/-)mice, ApoE^-/- mice with a high-cholesterol diet were immunized with M. tuberculosis HSP65. Sera were obtained for measurement of anti-HSP65 antibodies by ELISA; the effect of administration of different antigens was investigated, respectively, using flow cytometry analysis on the number of CD4⁺CD25⁺Foxp3⁺Tregs and CD4⁺IL-17⁺ Th17; the production of cytokines(IL-10, TGF-β1, IL-17 and IL-21)by these cells were determined by ELISA; total plasma cholesterol(TC), triglyceride(TG), high-density lipoprotein cholesterol(HDL-C)and low-density lipoprotein cholesterol(LDL-C)levels were detected by biochemical autoanalyzer. Atherosclerotic lesions were measured by lipid deposition stained with oil red O. The results demonstrated that the levels of anti-HSP65 IgG antibodies were increased significantly in Mycobacterium tuberculosis HSP65-treated ApoE^-/- mice, revealed obvious decrease in Treg number, Treg related cytokines(IL-10, TGF-β1)levels and significant increase in Th17 number, Th17 related cytokines(IL-17 and IL-21)levels, the levels of TC, TG, HDL-C and LDL-C did not change between groups, while the atherosclerotic lesions significantly increased. Results indicate that M. tuberculosis HSP65 could interrupt the Th17/Treg immune balance in ApoE^-/- mice, suggesting a potential role in the formation and progression of atherosclerosis.