Fig. 1: Intranasal vaccination with RBD-fused MSA in female BALB/c mice induces protective antigen-specific IgG and IgA antibodies. | Nature Communications

Fig. 1: Intranasal vaccination with RBD-fused MSA in female BALB/c mice induces protective antigen-specific IgG and IgA antibodies.

From: An intranasal subunit vaccine induces protective systemic and mucosal antibody immunity against respiratory viruses in mouse models

Fig. 1

a Top panel: Illustration of a fusion design with albumin genetically fused to RBD, and intranasal vaccination followed by FcRn-mediated transport of the vaccine across polarized mucosal epithelial cells, immune cell processing, and transport of generated IgG and IgA antibodies by FcRn and the pIgR, respectively, to the mucosal surface, and also blood for IgG. Bottom panel: Flow chart outlining the intranasal vaccination protocol with live virus challenge or endpoint sample harvest at week 5. Mice were vaccinated with equimolar amounts of RBD and RBD-MSA (prime dose: 6.2 µg and 19.9 µg, respectively, boost: 10% of prime) in combination with 20 μg CpG, or given PBS. b Illustration of ELISA and data for determination of RBD epitope availability on the RBD-albumin fusion compared to RBD alone, using the commercial monoclonal antibodies sotrovimab, cilgavimab and tixagevimab. c Illustration of the flow cytometric bead array (FCBA) for detection of antigen-specific antibodies in sera and BALF and data from analyses at endpoint. d Illustration of the FCBA for detection of antibodies able to inhibit human ACE2-RBD binding. Antibodies can inhibit human ACE2 binding to RBD-coupled beads (1a-1b), or not, leading to detection of ACE2-DIG bound to RBD-coupled beads by anti-DIG-PE (2), and results from sera and BALF at endpoint, detected using FCBA and ELISA (only sera). e Illustration of a pseudovirus neutralization cellular assay based on lentiviral infection of 293T-hACE2-TMPRSS2 cells where the presence of antibodies blocks cellular infection (1), while reduced blocking ability leads to pseudoviral entry and GFP expression (2), and results from sera and BALF at endpoint using SARS-CoV-2 pseudovirus of the ancestral strain (Wuhan). Curve plots in b are presented as each replicate of technical duplicates. Bars indicating c, d group mean ± SD with individual mice represented as a single datapoint (sera: n = 6, BALF: RBD n = 3 and RBD-MSA n = 4) and e technical duplicates of pooled biological samples per group (sera: n = 6, BALF: RBD n = 3 and RBD-MSA n = 5). c, d Two-tailed unpaired t-test. a Created or b–e partially created in BioRender86.

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