Expression and Identification of Virus-like Particles Presenting Novel Coronavirus RBD Antigen

ABSTRACT

Objective: Hepatitis B virus core protein HBc was used as vector to construct virus-like particles expressing novel coronavirus spike protein receptor binding domain RBD, and their immunogenicity was identified, which provides a new idea for the development of COVID-19 vaccines. Methods: The amino acid coding sequence 78 and 81 of hepatitis B virus core protein HBc (1-183 aa) were inserted into novel coronavirus spike protein receptor binding domain RBD and ligated by flexible linker (G4S) 3. After sequence optimization, the fusion gene was cloned into prokaryotic expression vector pET-28a (+) and transformed into expression strain Rosetta. After induced expression in self-inducing medium, the virus-like particles (VLPs) were purified by sucrose density gradient centrifugation. VLPs were detected and identified by SDS-PAGE, Western blot and transmission electron microscope. BALB/c mice were immunized subcutaneously with the prepared VLPs in equal proportion with adjuvant. The specific antibodies in the serum of the mice were analyzed by ELISA to verify the immune effect of HBc-RBD VLPs. Results: Escherichia coli can express partially soluble VLPs in self-inducing medium. VLPs could be observed by transmission electron microscope after purification by sucrose density gradient centrifugation. Mice immunized with HBc-RBD VLPs produced specific antibodies against RBD antigen. Conclusion: VLPs displaying RBD antigen were successfully expressed in prokaryotic expression systems, and their immunogenicity was preliminarily verified by mouse experiment, which provides a new direction for the research and development of novel coronavirus vaccines. © 2022, China Biotechnology Press. All rights reserved.