Antigenic profiling and target specific isolation of mAb against viral spike protein of emerging diseases

Abstract

Outbreak of viral infections cause infectious diseases with variable mortality rates and are associated with serious public health concerns and major economic crippling. Two notable examples of such emerging diseases are Chikungunya and the current pandemic of COVID19, Most viral particles enter target host cells through the specific interaction between their surface glycoproteins and target host cell surface receptor(s) in the viral life cycle. As such, the surface glycoproteins (also known as spike proteins) have been the focus to identify potential neutralizing monoclonal antibodies (nmAbs) for antibody therapy. While many neutralizing mAbs that prevent host cell surface receptors binding have shown potent immune responses, the receptor-binding domain (RBD) of viral surface proteins is prone to hypermutations, resulting in the emergence of more virulent strains. Using the technique of yeast surface display (YSD), the immunodominant epitopes within the Chikungunya virus (CHIKV) surface glycoproteins was comprehensively mapped using patient convalescent serum, and a novel immunodominant epitope(s) within the CHIKV-E1 was identified and used to isolate E1-specific mAbs from phage single-chain variable fragment (ScFv) library. After which, a panel of ScFvs were expressed as human IgGs to carry out biochemical and structural analysis. Using similar principles and approaches, a conserved immunodominant epitope within the S2 domain of MERS-CoV was identified, which was used to isolate a panel of cross-reactive mAbs from SARS patient samples that showed cross-reactivity and neutralizing ability. More importantly, these mAbs also showed neutralizing ability to the SARS-CoV-2. Furthermore, CHIK-virus like particals(VLP) was expressed in different expression systems, and chimeric-VLP for SARS-CoV-2 RBD was generated using the SpyCatcher/SpyTag system to assess the feasibility of potential vaccine candidates for both CHIK and COVID19.