Study On The Effect And Mechanism Of IL-27/IL-27R Signaling Pathway On Host Defence To Chlamydia Lung Infection

Background and Objective:As one of the four major infectious diseases that spread widely in the world,chlamydia is seriously endangering human health and there is no effective and specific treatment method at present.Therefore,it is necessary to look for key factors that affect the role of host Th1-mediated infection in chlamydia,and to provide new clues in the treatment of chlamydia infection.IL-27 can be produced by multiple antigen-presenting cells（APCs）when stimulated by microorganisms and their products,as well as being specific immune environment.IL-27/IL-27R pathway has impact on the host innate and adaptive immune responses in the models of infectious pathogens,including parasites,bacteria and nematodes.Taking chlamydia as an example,we aim to explore the role of IL-27/IL-27R pathway in against intracellular bacteria and to further study the effect of IL-27/IL-27R pathway in host immune response against chlamydia infection.Our preliminary findings suggested that IL-27may play a role as an important immunomodulatory factor during host chlamydia lung infection.Methods:Female C57BL/6（wild type,WT）mice at the age of 6-8 weeks old were inoculated intranasally with 1×10³ inclusion-forming units（IFU）of Chlamydia muridarum（Cm）to induce the mouse Chlamydia pneumonitis.Mice were executed at day 0,day 3,day 7 and day 14 p.i..Total RNA of lung tissue were extracted and the expression of IL-27 and IL-27R were detected by RT-PCR to explore whether IL-27/IL-27R axis was affected during Cm lung infection.The IFU of infected WT mice and IL-27rαgene knockout(WSX-1^-/-)mice were detected by ELISA,while pathological change and inflammatory cells infiltration in lungs was detected by H&E-staining.Intracellular cytokines including IFNγ,IL-17A and IL-4 were detected by flow cytometer to explore the immune responses of Th1,Th17 and Th2 in lungs and spleen.Results:In WT mice,the expression of IL-27/IL-27R mRNA was significantly increased at day 7 p.i..Compared with WT mice,WSX-1^-/-mice showed a poor condition with more severe emaciation,dim fur,piloerection and reduction of activity than WT mice after Cm lung infection.By monitoring the body weight change during Cm infection,WSX-1^-/-mice showed more weight loss comparing with WT mice,especially at day11 to 14 p.i..The bacteria load of WT and WSX-1^-/-mice both reached to the top at day 7 p.i.,but bacterium in WSX-1^-/-mice lung was more than that of WT mice at day14 p.i..Pathological analysis results showed that WSX-1^-/-mice had more serious pathological changes with more seriflux,severer edema,more inflammatory cell infiltration and more obvious consolidation compared with WT mice at day 14 p.i..Comparing to WT mice,WSX-1^-/-mice displayed stronger Th17 response and impaired Th1 and Th2 response in lungs at day 7 and/or day 14 p.i..Furthermore,there was no obviously difference on Th1/Th2/Th17 responses in spleen between WT and WSX-1^-/-mice during Cm lung infection.Conclusions:1.IL-27/IL-27R participates in host against chlamydia immune response2.IL-27/IL-27R signaling pathway has protective effect in chlamydia infection.3.IL-27/IL-27R signaling pathway affects the local immune function in lungs, but has no significant effect on system immune function in spleen.IL-27/IL-27R signaling pathway suppresses the secretion of IL-17 by Th17cells while enhance the secretion of IFNγby Th1 cells to play the role in immune protection against Cm infection.