论文部分内容阅读
Japanese encephalitis（JE）is an important mosquito-borne zoonosis,caused by Japanese encephalitis virus（JEV）.During JEV infection,JEV can escape the immune surveillance and invade into the central nervous system（CNS）.Viral immune escape is the prerequisite for the CNS infection.Myeloid derived suppressor cells（MDSCs）,as a heterogeneous population composed of a large number of immature cells,have the ability to significantly suppress the immune response.Monocytic MDSCs（M-MDSCs）are a subtype of MDSCs.Early research showed that MDSCs accumulated in the spleen in the early stage of JEV infection,and inhibited the proliferation of CD4+T cell,especially for follicular helper T cell（Tfh）.But the derivation of MDSCs’proportion in the early stage of JEV infection is unclear.In this study,JEV infected mouse model was used to investigated the derivation of MDSCs.As shown in the results,on day 3 after JEV infection,the proportion of M-MDSCs in mice spleen significantly increased;bone marrow cells（BMC）were isolated and infected with JEV,after 3 days of infection,the proportion of M-MDSCs-like cells increased and the m RNA level of Arg1 was also up-regulated.After cultured with JEV for 3 days,BMC were mixed with CFSE-labeled lymphcytes in the ratio of 2:1 for 4days,and it was shown that the proliferation of CD4+T cell was inhibited.The m RNA levels of TLR9 and TLR3 in BMC were significantly up-regulated at 12 h,24 h,and 48 h after JEV infection;treatment with Cp G or Poly（I:C）could induce M-MDSCs-like cells in BMC,and TLR9 deficiency could decreased the proportion of M-MDSCs.The expression of STAT1 and p-STAT1 increased after 12 h of JEV infection,but it could be declined after TLR9 deficiency,and the m RNA levels of cell cycle-related gene CCDN1and GATA2 was up-regulated after JEV infection.The mitochondrial membrane potential in BMC decreased and the cytosol mitochondrial DNA increased after JEV infection.Compared with wild-type mice,the proportion of M-MDSCs significantly reduced in the spleen of TLR9-/-mice,along with the enhanced activity of T cells,and an increased proportion of Tfh and a decrease of Treg.Compared with wild-type mice,the survival rate of TLR9-/-mice increased about 20%after JEV infection.It also showed that a significant reduction in viral load and the alleviated pathological changes in the brain of TLR9-/-mice at 5 dpi.These results uncover the key role of TLR9 in M-MDSCs induction during JEV infection.It can provide theoretical basis for further study of JEV immune evasion and clinical treatment.