3D8, a nucleic acid-hydrolyzing scFv, confers antiviral activity against SARS-CoV-2 and multiple coronaviruses in vitro

The current pandemic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pose a critical public health threat worldwide. Coronaviruses (subfamily Orthocoronavirinae, family Coronaviridae, order Nidovirales) are a group of enveloped positive-sense single-stranded RNA viruses. Six pathogenic human coronaviruses, likely zoonotic viruses, cause the common cold in humans. A new emerging coronavirus, SARS-CoV-2, become a crucial etiology for the Coronavirus-induced disease 19 (COVID-19). However, effective therapeutics and vaccines against multiple coronaviruses remain unavailable. This study aimed to investigate an antiviral molecule, single chain variable fragment (scFv), against SARS-CoV-2 and other coronaviruses. 3D8, a recombinant scFv, exhibits broad-spectrum antiviral activity against DNA and RNA viruses owing to its nucleic acid-hydrolyzing property. Here, we report that 3D8 scFv inhibited the replication of SARS-CoV-2, human coronavirus OC43 (HCoV-OC43), and porcine epidemic diarrhea virus (PEDV). Our results revealed the prophylactic and therapeutic effects of 3D8 scFv against SARS-CoV-2 in Vero E6 cells. Immunoblot and plaque assays showed the absence of coronavirus nucleoproteins and infectious particles in 3D8 scFv-treated cells, respectively. In addition, we observed the antiviral effects of 3D8 against HCoV-OC43 and PEDV. In conclusion, this study provides insights into the broad-spectrum antiviral agent of 3D8 scFv; thus, it could be considered a potential antiviral countermeasure against SARS-CoV-2 and zoonotic coronaviruses. Key points (Main message)O_LI3D8, a nucleic acid-hydrolyzing scFv, exhibits potent prophylactic and therapeutic antiviral effects on SARS-CoV-2. C_LIO_LI3D8 exhibits broad-spectrum antiviral activity against multiple coronaviruses: hCoV OC43 and PEDV. C_LIO_LI3D8 potentially degrades viral RNA. C_LI