Utilizing Aspergillus oryzae for Expression of SARS-CoV-2 Spike Protein Domains: Insights into COVID-19 Research

Abstract

The COVID-19 pandemic has underscored the urgent need for effective diagnostics due to the highly contagious nature of SARS-CoV-2, which infects host cells by binding to the ACE2 receptor in the respiratory system. The spike (S) protein of the virus, essential for viral entry, comprises two subunits (S1 and S2) with an N-terminal domain (NTD) and a receptor-binding domain (RBD). Various expression systems have been employed to produce these viral proteins to evaluate their utility as antigens in COVID-19 detection assays. Aspergillus oryzae, recognized as Generally Recognized as Safe (GRAS), is widely used in fermentation and enzyme production owing to its high secretion capability, cost-effective media, and environmental resilience. This study demonstrates the successful expression of the NTD and RBD in Aspergillus oryzae for the first time, producing them as glucoamylase-fusion proteins. These fusion proteins were purified through metal affinity chromatography and verified by size-exclusion chromatography. Their ability to bind human anti-IgG antibodies was assessed using an ELISA, revealing significant, concentration-dependent interactions. This confirms their functionality in antigen antibody interactions and establishes A. oryzae as a viable platform for producing viral proteins, facilitating scalable and cost-effective production for advanced research, vaccine development, and immunoassay design.