Abstract
The virus behind the current pandemic, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the etiology of novel coronavirus disease (COVID-19) and poses a critical public health threat worldwide. Effective therapeutics and vaccines against multiple coronaviruses remain unavailable. Single-chain variable fragment (scFv), a recombinant antibody, exhibits broad-spectrum antiviral activity against DNA and RNA viruses owing to its nucleic acid-hydrolyzing property. The antiviral activity of 3D8 scFv against SARS-CoV-2 and other coronaviruses was evaluated in Vero E6 cell cultures. Viral growth was quantified with quantitative RT-qPCR and plaque assay. The nucleic acid-hydrolyzing activity of 3D8 was assessed through abzyme assays of in vitro viral transcripts and cell viability was determined by MTT assay. We found that 3D8 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 reduction of coronavirus nucleoproteins and infectious particles, respectively, in 3D8 scFv-treated cells. These data demonstrate the broad-spectrum antiviral activity of 3D8 against SARS-CoV-2 and other coronaviruses. Thus, it could be considered a potential antiviral countermeasure against SARS-CoV-2 and zoonotic coronaviruses.
Highlights
IntroductionCoronaviruses (subfamily Orthocoronavirinae in the family Coronaviridae of the order Nidovirales) are a group of enveloped viruses containing a single-stranded positive-sense RNA genome [1,2]
Coronaviruses are a group of enveloped viruses containing a single-stranded positive-sense RNA genome [1,2]
D8 Degraded In Vitro RNA Transcripts (IVTs) of SARS-CoV-2, HCoV-OC43, and porcine epidemic diarrhea virus (PEDV)
Summary
Coronaviruses (subfamily Orthocoronavirinae in the family Coronaviridae of the order Nidovirales) are a group of enveloped viruses containing a single-stranded positive-sense RNA genome [1,2]. Divergent coronaviruses constitute four genetic lineage groups, namely alphacoronaviruses, betacoronaviruses, gammacoronaviruses, and deltacoronaviruses These viruses infect a broad range of natural reservoir hosts, including humans, bats, rodents, pigs, and camels [3]. The viral evasion is facilitated by transmembrane serine protease 2 (TMPRSS2) through spike protein fusogenic activity [8,9] This novel strain is genetically distinct from SARS-CoV-1, despite both being members of lineage 2 betacoronaviruses [10]. COVID-19 is characterized by influenza-like symptoms ranging from mild to severe lung injury and multi-organ failure, leading to death in patients with comorbidities [12] This novel virus has led to a global pandemic, resulting in unparalleled public health emergencies [13]. As of 10 March 2021, it has rapidly spread to 223 countries and territories, affecting over 117.3 million people and causing more than 2.6 million deaths [14]
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