Fig 1: FcRn-mediated intranasal vaccination significantly induces S-specific local immune responses in the respiratory tract.A. Ten µg of S-Fc or PBS in combination with 10 µg of CpG was i.n. administered into 6–8 week old mice (n=10). Mice were boosted 14 days after primary immunization. An additional group of mice (n=10) that were intramuscularly (i.m.) immunized in 10 µg S-Fc with 10 µg of CpG was included as an i.m. route control. Tissues were collected at the indicated time points.B+C+D. Anti-SARS-CoV-2 S-specific IgA or IgG Ab titers in nasal washings (A), BAL (B), and serum (C) after the boost. SARS-CoV-2 S-specific Abs were measured by ELISA 14 days after the boost in 10 representative mouse samples per group. The data represent a geometric mean with 95% CI.E+F+G. Tissue-resident memory (TRM) T cells in mouse lungs. The IV-CD3+CD4+CD69+ CD103+ (top panel) or IV-CD3+CD8+CD69+CD103+ (bottom panel) TRM T cells in the lungs were assessed 7 days after the boost by FACS. Flow cytometry plots are the representative results from 5–6 individual samples per group. Numbers in the top right quadrants (E) or the graph (F+G) represent the percentage of TRM CD4+ or CD8+ T lymphocytes following i.n. or i.m. immunizations. The student t-test was used for the statistical analysis of data from experiments B-D, while one-way ANOVA was used for analyzing the results of F and G. Nonparametric test was used if the distribution of data was not normal.