Validating Enterovirus D68-2A as an Antiviral Drug Target and the Discovery of Telaprevir as a Potent D68-2A Inhibitor.

Enterovirus D68 (EV-D68) is a viral pathogen that leads to severe respiratory illness and has been linked with the development of acute flaccid myelitis (AFM) in children. No vaccines or antivirals are currently available for EV-D68 infection， and treatment options for hospitalized patients are limited to supportive care. Here， we report the expression of the EV-D68 2A protease (2A) and characterization of its enzymatic activity. Furthermore， we discovered that telaprevir， an FDA-approved drug used for the treatment of hepatitis C virus (HCV) infections， is a potent antiviral against EV-D68 by targeting the 2A enzyme. Using a fluorescence resonance energy transfer-based substrate cleavage assay， we showed that the purified EV-D68 2A has proteolytic activity selective against a peptide sequence corresponding to the viral VP1-2A polyprotein junction. Telaprevir inhibits EV-D68 2A through a nearly irreversible， biphasic binding mechanism. In cell culture， telaprevir showed submicromolar-to-low-micromolar potency against several recently circulating neurotropic strains of EV-D68 in different human cell lines. To further confirm the antiviral drug target， serial viral passage experiments were performed to select for resistance against telaprevir. An N84T mutation near the active site of 2A was identified in resistant viruses， and this mutation reduced the potency of telaprevir in both the enzymatic and cellular antiviral assays. Collectively， we report for the first time the enzymatic activity of EV-D68 2A and the identification of telaprevir as a potent EV-D68 2A inhibitor. These findings implicate EV-D68 2A as an antiviral drug target and highlight the repurposing potential of telaprevir to treat EV-D68 infection. A 2014 EV-D68 outbreak in the United States has been linked to the development of acute flaccid myelitis in children. Unfortunately， no treatment options against EV-D68 are currently available， and the development of effective therapeutics is urgently needed. Here， we characterize and validate a new EV-D68 drug target， the 2A， and identify telaprevir-an FDA-approved drug used to treat hepatitis C virus (HCV) infections-as a potent antiviral with a novel mechanism of action toward 2A 2A functions as a viral protease that cleaves a peptide sequence corresponding to the VP1-2A polyprotein junction. The binding of telaprevir potently inhibits its enzymatic activity， and using drug resistance selection， we show that the potent antiviral activity of telaprevir was due to 2A inhibition. This is the first inhibitor to selectively target the 2A from EV-D68 and can be used as a starting point for the development of therapeutics with selective activity against EV-D68.