Catalytic antibodies against viruses have been constantly developed in preventive or therapeutic fields to target viral antigens effectively. 3D8 is an anti-DNA catalytic antibody that binds to DNA and RNA then degrades them without sequence specificity as well known as Abzymes. Previously it was reported that 3D8 single chain variable fragment (scFv) has cell-penetrating activity by electrostatic interaction with cellular membrane and it localizes in cytosol resulting in cell death by cellular rRNA degradation. These result mean that 3D8 scFv would also have potential activity as an intracellular antiviral antibody. Since 3D8 scFv has RNase activity, 3D8 scFv could hydrolyze almost viral RNA transcripts or genomes replicated in cytoplasmic space without sequence specificity. Above all, RNA genome viruses preferentially replicate their genes and transcripts in cytoplasmic space. The 3D8 scFv localized in cell cytoplasm could target these viral RNA genomes as a therapeutic reagent. So far, antiviral drugs are limited in specific viral antigens or specific virus species. The advantage of many viruses is their fast mutation so that can make variant mutants from one genus of viruses. Herein I show viral RNA degradation by 3D8 scFv without sequence specificity resulting in suppressed replication of various RNA genome viruses; classical swine fever virus, vesicular stomatitis virus, and influenza A virus. The method for detection of viral RNA degradation is based on click chemistry. Consequently, it is demonstrated that the antiviral activity of RNA-hydrolyzing 3D8 scFv against RNA viruses by using a 3D8 scFv expressing cell lines and by the exogenous treatment of 3D8 scFv protein to cells. 3D8 scFv strongly suppressed virus replication from the viral RNA replication level without involving IFN-β induction. The antiviral mechanism of action is inhibition of propagating viral RNA transcripts by binding or degrading on viral RNA due to RNase activity of 3D8 scFv itself.
