Effect Of Mycobacteriun Tuberculosis Antigen CFP-10-ESAT-6 Complex On Function And Phenotype Of Human Monocytes/macrophage And The Mechanism Of Action

Tuberculosis,caused by mycobacterium tuberculosis infection,still tops the list of death due to infectious diseases.Approximately one third of world population was infected by mycobacterium tuberculosis,over 8 million new cases of tuberculosis and at least 2 million deaths from this disease occur every year worldwide. It is estimated that the individual developed into active TB,may be caused by short-term newly infection by MTB or activation after long-term latent MTB.The interaction between host and pathogen may decided the different results of infection.MTB is a typical intracellular pathogen,whose main host cell is macrophage.MTB binded the macrophage surface receptors,then formed phagosomes by membrane invagination ,engulfed into the macrophage.Macrophage can wound , kill and scanvenge MTB by phagosome-lysosome fusion,generation of active free radical such as reactive nitrogen intermediates and reactive oxygen intermediates,self apoptosis,secretion of a large amount of cytokines to regulate the immune response and processing and presenting MTB antigen to CD4+T和CD8+T cells,generation of MTB-specific T cells.MTB also can escape scanvenging by interfering with the pathway above.In the infection or process of growth ,MTB can generate different protein in different period,for axample: low molecular weight antigens such as ESAT-6 and CFP-10 in the early period of infection or culture;the cell wall and cytoplasm antigens such as Ag85 complex, MPT53,MPT63,MPT64,MPT70,MPT32,38kd,19kd,LAM,PGL,etc.Some of these antigens can induce strong cellular immune response,however,the others were regarded to be related with immune regulation and immune evasion of MTB.CFP-10 and ESAT-6,encoded by RD1 region,which only present in virlurent and pathogenic MTB but absent in BCG and non-pathogenic mycobacteria,is very specific.The two linked with each other closely to form a 1:1 heterodimer as complex.Both CFP-10 and ESAT-6 can activated macrophage to generate NO and TNF-α,express antigen presenting relevant functional elements such as B7.1(CD80),MHC-II,ICAM-I,etc.Both of them can strongly induce mouse bone marrow differentiated into dendritic cells-like antigen presenting cells.As a closely linked heterodimer,CE complex may bind to the surface of human monocytes by the CFP-10 protein C-terminal,induce changes of corresponding intracellular signaling pathway to modulate host's anti-TB immune response of monocytes-macrophage.Objective To investigate the effect of Mycobacterium tuberculosis CE complex on the function and phenotype of monocytes/macrophage and conceivable mechanism of action or signaling pathway of it,thus find the conceivable mechanism of immune invasion of MTB,which leaded to latent and chronic infection,provide the new ideas for the prevention and treatment of tuberculosis.Methods Used the recombinant CE complex ,which expressed by E.coli to co-culture with leukmic THP-1 cells or peripheral blood mononuclear cells in different concentration of CE complex and different culture time,then collected the supernantant and cells.Detceted the level of TNF-α,IL-10,IL-12 generated by the monocytes/macrophage,which stimulated by the CE coplex,and the phenotype of monocytes/macrophage.And used the specific signaling pathway inhibitors to investigate the signaling pathway of effect of the CE complex. monocytes/macrophage,generated a large amout of TNF-αin the early period(4~8h) of co-culture;selective inhibitors of signaling pathway MEK1/2 and P38 MAPK can inhibit the effect of CE complex.CE complex promoted the expression of antigen presenting relevnet functional elements HLA-DR,CD80,CD40 on the surface of monocytes/macrophage.But in later period of co-culture(>48h),CE complex inhibited the TNF-αgeneration by monocytes/macrophage,inhibited the expression of HLA-DR,CD80,CD40,promoted the generation of IL-10 and stimulated the monocytes to express a great quantity of DC-SIGN with the participation of IL-4.Conclusions CE complex activated the monocytes/macrophage may by the activation of signaling pathway MEK1/2 and P38 MAPK,formed a strongly anti-TB immune response,limited the growth of MTB in vivo,may have important protective significance in the early period of infection.But in later period of infection,CE complex may inhibited the protective immune response of monocytes/macrophage against MTB,inhibited the MTB eliminated by monocytes/macrophage,help MTB survive in the monocytes/macrophage,leaded to latent and chronic infection.