| Tuberculosis(TB)is a chronic infectious disease caused by Mycobacterium tuberculosis(Mtb)infection.It is one of the top ten causes of death in the world.It has surpassed AIDS as the leading cause of death caused by a single infectious agent.According to statistics from the World Health Organization,the number of new tuberculosis patients worldwide reached 10 million in 2019,and 1.4 million people died of tuberculosis.My country has always been one of the countries with a high burden of tuberculosis.In recent years,there have been many tuberculosis outbreaks,such as the clustered tuberculosis epidemic in Taojiang Middle School in Hunan in 2017 and the clustered tuberculosis of students in Jiangsu Normal University in 2020.Numerous data show that the "white plague" of tuberculosis has not gone far,and the situation is still grim.Macrophages are the first line of defense for human immune defense,and they play an extremely important role in mediating the human immune response.On the one hand,when macrophages face foreign invaders,they can eliminate invading tuberculosis by forming phagolysosomes,producing a variety of cytokines and free radicals for antigen presentation,inducing apoptosis and autophagy,etc.On the other hand,facing the "encirclement and suppression" of macrophages,Mycobacterium tuberculosis has evolved the ability to manipulate and escape the host's immune response to escape the killing of macrophages.The mutual game between macrophages and Mycobacterium tuberculosis plays a very important role in the occurrence,development and recovery of tuberculosis.In this study,we used the non-toxic Mycolicibacterium smegmatis as a model strain to study the function of Rv2091c.Previous studies predicted that Rv2091c is one of 54 potential host-interacting effector molecules,but the specific function is unknown.Effector molecules play an important role in the host immune response of Mycobacterium tuberculosis.At present,it is believed that these effector molecules mainly inhibit the survival of Mycobacterium tuberculosis in macrophages through the formation of phagolysosomes,free radical killing and cell apoptosis,thereby achieving the purpose of protecting the host.In addition,some effector molecules can also save the host's acquired immune response by influencing the host's inflammatory response and the process of antigen presentation.Therefore,exploring new effector molecules and their functional mechanisms in the interaction between Mycobacterium tuberculosis and the host is still one of the important directions of current research.We constructed a recombinant Mycolicibacterium smegmatis that overexpressed Rv2091c through the plasmid pNIT-Myc,and found that Rv2091c was located on the cell wall through subcellular localization analysis.Through experimental studies,we have observed that the survival of Rv2091c recombinant bacteria in macrophages is reduced,accompanied by inflammation and apoptosis,which may be caused by the activation of the Caspase cascade to trigger a series of immunological reactions.Western blotting experiments found that the expression of Caspase-3 and Caspase-7 proteins involved in apoptosis in recombinant bacteria was significantly higher than that in empty bacteria,and the expression of PARP,a key protein for testing apoptosis,also increased in recombinant bacteria.In addition,Rv2091c recombinant bacteria can promote the secretion of pro-inflammatory cytokines such as IL-6,IL-12p40 and TNF-?.The research data of this subject indicate that Rv2091c may be involved in the interaction between Mtb and host macrophages.In summary,we have identified that Rv2091c is localized in the cell wall,and this protein can affect the survival of recombinant M.smegmatis in macrophages by regulating the expression of host cytokines and the level of apoptosis. |
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