Fig 2: Intranasal immunization with CuMVTT‐RBD promotes isotype switching to IgA and leads to balanced IgG subclass responses. (A) RBD‐specific IgG1, IgG2a, IgG2b, and IgG3 titer for the groups vaccinated with CuMVTT‐RBD vaccine or CuMVTT control on Day 42 measured by ELISA, LOG10 OD50 shown. (B) RBD‐specific IgA titer for the groups vaccinated with CuMVTT‐RBD vaccine or CuMVTT control on Day 42 measured by ELISA, OD450 shown. (C) RBD‐specific IgA titer at Day 42 from mice immunized with CuMVTT‐RBD vaccine, LOG10 OD50 shown. Plates in duplicates: treated with PBSTween or 7 M urea. (D) Avidity index of RBD‐specific IgA titer. Statistical analysis (mean ± SEM) using Student's t‐test. Control group n = 6, vaccine group n = 6. One representative of 2 similar experiments is shown

Fig 3: Intranasal administration of CuMVTT-RBD induced RBD-specific IgG and IgA plasma cells locally and systemically. (A–C) Number of RBD specific IgG and IgA secreting cells per 2 × 106 seeded cells in spleen (A), BM (B) or per 2 × 105 seeded cells in lung (C) after immunization with CuMVTT-RBD vaccine or CuMVTT control, detected by Fluorospot. (D–F) Representative pictures of wells seeded with cells out of spleen (D), BM (E), lung (F). Statistical analysis (mean ± SEM) using Student's t-test. Control group n = 6, vaccine group n = 6. One representative of 2 similar experiments is shown