Novel small-molecule inhibitors of transmissible gastroenteritis virus

We used swine testicle (ST) cells infected with transmissible gastroenteritis virus (TGEV) and an indirect immunofluorescent assay with antibodies against TGEV spike and nucleocapsid proteins to screen small-molecule compounds that inhibit TGEV replication. Analogues of initial hits were collected and subjected to a 3CL protease (3CL(pro)) inhibition assay with recombinant 3CL(pro) and a fluorogenic peptide substrate. A series of benzothiazolium compounds were found to have inhibitory activity against TGEV 3CL pro and to exert anti-TGEV activities in terms of viral protein and RNA replication in TGEV-infected ST cells, with consequent protection of TGEV-infected ST cells from cytopathic effect by blocking the activation of caspase-3.