Non-Glycosylated SARS-CoV-2 Omicron BA.5 Receptor Binding Domain (RBD) with a Native-like Conformation Induces a Robust Immune Response with Potent Neutralization in a Mouse Model

• Published in: Molecules (Basel, Switzerland) Vol. 29; no. 11; p. 2676
• Main Authors: Wongnak, Rawiwan, Brindha, Subbaian, Oba, Mami, Yoshizue, Takahiro, Islam, Md. Din, Islam, M. Monirul, Takemae, Hitoshi, Mizutani, Tetsuya, Kuroda, Yutaka
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01.06.2024; MDPI
• Subjects: Angiotensin-Converting Enzyme 2 - chemistry; Angiotensin-Converting Enzyme 2 - immunology; Angiotensin-Converting Enzyme 2 - metabolism; Animals; Antibodies; Antibodies, Neutralizing - immunology; Antibodies, Viral - immunology; Antigens; Chemical bonds; COVID-19 - immunology; COVID-19 - prevention & control; COVID-19 vaccines; COVID-19 Vaccines - chemistry; COVID-19 Vaccines - immunology; Disease Models, Animal; E coli; Escherichia coli - metabolism; Ethylenediaminetetraacetic acid; Female; Flow cytometry; Glycosylation; Health aspects; Humans; Immune response; immunogenicity; Infections; Mice; molten globule state; Mutation; native-like state; neutralization; non-glycosylation; Omicron SARS-CoV-2; Pathogens; Protein Binding; Protein Domains; Proteins; SARS-CoV-2 - immunology; Severe acute respiratory syndrome coronavirus 2; Spike Glycoprotein, Coronavirus - chemistry; Spike Glycoprotein, Coronavirus - immunology; Spike Glycoprotein, Coronavirus - metabolism; T-Lymphocytes - immunology; Viral infections; Japan; Omicron SARS-CoV-2; disulfide bonds; molten globule state; E. coli-expression system; native-like state; limited proteolysis; neutralization; non-glycosylation; immunogenicity
• DOI: 10.3390/molecules29112676
• ISSN: 1420-3049

The Omicron BA.5 variant of SARS-CoV-2 is known for its high transmissibility and its capacity to evade immunity provided by vaccine protection against the (original) Wuhan strain. In our prior research, we successfully produced the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein in an E. coli expression system. Extensive biophysical characterization indicated that, even without glycosylation, the RBD maintained native-like conformational and biophysical properties. The current study explores the immunogenicity and neutralization capacity of the E. coli-expressed Omicron BA.5 RBD using a mouse model. Administration of three doses of the RBD without any adjuvant elicited high titer antisera of up to 7.3 × 105 and up to 1.6 × 106 after a booster shot. Immunization with RBD notably enhanced the population of CD44+CD62L+ T cells, indicating the generation of T cell memory. The in vitro assays demonstrated the antisera’s protective efficacy through significant inhibition of the interaction between SARS-CoV-2 and its human receptor, ACE2, and through potent neutralization of a pseudovirus. These findings underscore the potential of our E. coli-expressed RBD as a viable vaccine candidate against the Omicron variant of SARS-CoV-2.