Regulatory Effects Of Five Mycobacterium Tuberculosis Secreted Proteins On Immune Function Of Macrophages

Alveolar macrophages are the first living environment for M.tuberculosis after invading the host.After entering the host macrophage,M.tuberculosis can evade the host's immune surveillance and clearance functions through various mechanisms.Secreted proteins,which are important virulence factors,interact with certain components of the host,ultimately helping the pathogens to colonize,multiply and spread in host cells.However,the number of secreted proteins currently known to play a role in the infection of macrophages by M.tuberculosis is very limited,and the relevant regulatory mechanisms have yet to be elucidated.In this study,BCG strain-bovine macrophage(BoMac)interaction was used as a model to screen and initially discover three new secreted proteins(Rv0671,Rv0817,Rv1813),and their regulational function was discussed.The following results were obtained:(1)Based on the large-scale screening in the early stage of our laboratory,17 BCG recombinant strains overexpressing the potential secreted proteins of M.tuberculosis were further constructed,and the infection experiments of bovine macrophages(BoMac)were completed respectively;(2)RNA-seq technology was used to detect gene transcriptional changes in BoMac infected by all these bacteria,and afterwars systematic comparison was done to analyse their regulatory effects of pathways or processes such as apoptosis,TNF,and IL-17 signaling pathway,oxidative phosphorylation process,cytokine and receptor interaction,five secreted proteins including Rv0671,Rv0817,Rv1813,Rv3310 and Rv3841 were found to have significant effects on the host macrophage immune functions;(3)We discovered and preliminary confirmed that in addition to the reported inhibitory function on phagosome maturation,Rv3310(SapM)can also affect macrophage death,inhibit the expression and release of pro-inflammatory cytokines,and facilitate the survival rate of mycobacteria in BoMac and bone marrow derived macrophage(BMDM).These efforts provide new clues for an in-depth understanding of the function of secreted proteins during M.tuberculosis infection.