Isolation of scFv Antibodies Against Linear Epitopes of SARS-CoV-2 Spike Protein by Phage Display Technology

Abstract

Introduction and purpose: COVID-19 (coronavirus disease 2019) caused by a new coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Numerous mutations have occurred since the initial outbreak, resulting in the emergence of new strains of the virus, which has reduced the effectiveness of existing vaccines and treatments. In this study, monoclonal antibodies in single chain fragment variable (scfv) format were screened by phage display antibody library against the receptor binding domain (RBD). The aim of this study was to identify a novel scFv that can be utilized for the treatment and diagnosis of SARS-CoV-2. Materials and methods: The RBD protein was expressed and purified in the prokaryotic expression system and was used as an antigen in the Biopanning process. 6 rounds of selection were performed and the enrichment of RBD-specific phages was determined. A polyclonal phage ELISA was performed to monitor the binding affinity of RBD binders. Finally, specific clones were identified by monoclonal phage ELISA. After confirming the sequence, the expression and reactivity of the isolated anti-RBD was assessed. Also, the interaction of the identified scFv with the Wuhan and Variant of Concern strains was determined by bioinformatics tools. Findings: ELISA analysis revealed that the expressed RBD protein maintains its structural integrity and is well-reacted with serum antibodies. Phage display library screening led to the identification of a novel scFv that showed a strong reaction to RBD. Furthermore, bioinformatics analyses demonstrated that this scFv effectively neutralized and interacted with the main strain and other emerging VOCs. Conclusion: As a result of this study, a novel scFv antibody that neutralizes and interacts with SARS-CoV-2 virus has been identified, which can potentially be useful for research and therapeutic applications.