Characterization of Systemic and Mucosal Humoral Immune Responses to an Adjuvanted Intranasal SARS-CoV-2 Protein Subunit Vaccine Candidate in Mice

Mariam Maltseva; Yannick Galipeau; Tyler M Renner; Lise Deschatelets; Yves Durocher; Bassel Akache; Marc-André Langlois

doi:10.3390/vaccines11010030

Characterization of Systemic and Mucosal Humoral Immune Responses to an Adjuvanted Intranasal SARS-CoV-2 Protein Subunit Vaccine Candidate in Mice

Vaccines (Basel). 2022 Dec 23;11(1):30. doi: 10.3390/vaccines11010030.

Authors

Mariam Maltseva¹, Yannick Galipeau¹, Tyler M Renner², Lise Deschatelets², Yves Durocher², Bassel Akache², Marc-André Langlois^{1

3}

Affiliations

¹ Department of Biochemistry, Microbiology & Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada.
² National Research Council Canada, Human Health Therapeutics, Ottawa, ON K1A 0R6, Canada.
³ Ottawa Center for Infection, Immunity and Inflammation (CI3), Ottawa, ON K1H 8N5, Canada.

Abstract

Continuous viral evolution of SARS-CoV-2 has resulted in variants capable of immune evasion, vaccine breakthrough infections and increased transmissibility. New vaccines that invoke mucosal immunity may provide a solution to reducing virus transmission. Here, we evaluated the immunogenicity of intranasally administered subunit protein vaccines composed of a stabilized SARS-CoV-2 spike trimer or the receptor binding domain (RBD) adjuvanted with either cholera toxin (CT) or an archaeal lipid mucosal adjuvant (AMVAD). We show robust induction of immunoglobulin (Ig) G and IgA responses in plasma, nasal wash and bronchoalveolar lavage in mice only when adjuvant is used in the vaccine formulation. While the AMVAD adjuvant was more effective at inducing systemic antibodies against the RBD antigen than CT, CT was generally more effective at inducing overall higher IgA and IgG titers against the spike antigen in both systemic and mucosal compartments. Furthermore, vaccination with adjuvanted spike led to superior mucosal IgA responses than with the RBD antigen and produced broadly targeting neutralizing plasma antibodies against ancestral, Delta and Omicron variants in vitro; whereas adjuvanted RBD elicited a narrower antibody response with neutralizing activity only against ancestral and Delta variants. Our study demonstrates that intranasal administration of an adjuvanted protein subunit vaccine in immunologically naïve mice induced both systemic and mucosal neutralizing antibody responses that were most effective at neutralizing SARS-CoV-2 variants when the trimeric spike was used as an antigen compared to RBD.

Keywords: AMVAD; COVID-19; SARS-CoV-2; intranasal vaccine; mucosal immunity; receptor binding domain; spike; subunit vaccine.

Grants and funding

This study was supported in part by a COVID-19 Rapid Response grant by the Canadian Institutes of Health Research (CIHR; #VR2-172722) and by a grant supplement by the COVID-19 Immunity Task Force (CITF) to M-A Langlois. Production of COVID-19 reagents was financially supported by the NRC’s Pandemic Response Challenge Program. M.M. holds an Ontario Graduate Scholarship. Y.G. holds a CIHR Frederick Banting and Charles Best graduate scholarship (CGS-Doctoral).