Abstract: The present invention provides a Mycobacterium tuberculosis intein splicing inhibitor screening system, where Mycobacterium smegmatis is used as a model bacterium, a gene sequence of a protein regulated by an intein is inserted into a 65S site of a kanamycin-resistant protein gene, a vector with first antibiotic resistance is used for constructing a recombinant plasmid, and the recombinant plasmid is transferred into Mycobacterium smegmatis and is cultured in a medium containing a first antibiotic and kanamycin, to obtain the Mycobacterium tuberculosis intein splicing inhibitor screening system. The first antibiotic is any antibiotic other than kanamycin.

Abstract: The present invention discloses a targeted exosome based on the RBD region of SARS-CoV-2 S protein and a preparation method thereof. An RBD-VSVG fusion protein is expressed on the targeted exosome of the present invention, and the RBD-VSVG fusion protein is obtained by replacing the extracellular region of VSVG with the RBD of the SARS-CoV-2 S protein. In the present invention, a targeted exosome capable of efficiently and tissue-specifically delivering a potential anti-SARS-CoV-2 medicine is constructed. The targeted exosome is used to encapsulate SARS-CoV-2 siRNA, to specifically inhibit the virus replication in tissues and organs. In a mouse animal model, tail vein injection of exosome encapsulated SARS-CoV-2 siRNA significantly inhibits virus replication in mouse lung tissue and alleviates symptoms such as pneumonia caused by virus infection.