Analysis of surface expressed recombinant SARS-CoV-2 spike protein using human monoclonal antibodies

Abstract

SARS-CoV-2 virus has become the centre of virology research since the outbreak of COVID-19. Many studies have been done on the viral structure and properties. It was discovered that spike protein mediates critical functions of viral attachment to host cells and membrane fusion, rendering it an important target for therapeutic development. This project aims to analyse the spike protein by focusing on its interaction with four human monoclonal antibodies (PD4, PD5, SC23, SC29). The purpose is to first determine which part of the S protein these antibodies specifically bind to, and use them to monitor the process of spike protein synthesis, modification, and export onto the cell surface. The main method used was immunofluorescence assay done in transfected Vero-E6 cells expressing recombinant spike protein. It is revealed that a key conformation is formed in S1 subunit when spike protein undergoes post-translational modification in Golgi apparatus, and this conformation is targeted by neutralising antibodies. Notably, S1 subunit can be displayed on the cell surface independently without S2 subunit, enabling it to serve as a potential means of immunity escape by seizing the neutralising antibodies away from full-length spike proteins. These conclusions highlight the importance of targeting S1 in therapeutic development.