Figure 1 | Scientific Reports

Figure 1

From: Novel intranasal vaccine targeting SARS-CoV-2 receptor binding domain to mucosal microfold cells and adjuvanted with TLR3 agonist Riboxxim™ elicits strong antibody and T-cell responses in mice

Figure 1

Monovalent SARS-CoV-2 RBD vaccines induce IgG antibody responses in NALF, BALF and serum. Mice were prime-boost immunized (d0, d21) intranasally with non-targeted (nt) RBD, strain Wuhan-Hu-1 (group #1) or primed subcutaneously and boosted intranasally with nt RBD (group #2), or prime-boosted intranasally with nt RBD, adjuvanted with Riboxxim and Chitosan (group #3), or prime-boosted intranasally with M-cell targeted RBD (RBD-cCPE, group #7). All vaccines were adjuvanted with Riboxxim. Sera, nasal fluid (NALF) and bronchioalveolar fluid (BALF) were obtained on day 28, 1 week after the boost, diluted in fourfold steps, and assayed for IgA antibodies in a Luminex assay with recombinant nt RBD, or recombinant trimeric spike protein, both derived from SARS-CoV-2 strain Wuhan-Hu-1. Endpoint titers (EP) were defined as highest sample dilution exceeding the signal of mean of control group (#9) + 3xSD. Log10 EC50 values were calculated using GraphPad Prism 7, 5PL. For mice with low titers, EC50 could not be determined and log10 EC50 (IgG) was accepted as zero. Log10 of endpoint titers or EC50 were plotted with geometric mean ± geometric SD. Two-way comparisons using the Mann–Whitney U test.

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