Fig. 7: Repeated unadjuvanted nasal boosters enhance IgA recall responses in both upper and lower respiratory mucosa.
a, Schematic of the experimental strategy showing C57BL/6J mice i.m. primed with mRNA–LNPs at day 0, i.m. boosted with mRNA–LNPs or i.n. boosted with an unadjuvanted recombinant SARS-CoV-2 spike protein at day 14, followed by boosting i.n. with homologous spike protein at day 28 post-prime, followed by lung, BALF, serum and nasal wash analysis at day 35 post-priming i.m. b, Representative flow cytometry plots and number of extravascular total and RBD-specific IV−IgA+ ASCs in the lungs of naive C57BL/6 mice (D0, n = 11), i.m. primed + i.m. boosted mice (D35P+B, n = 10), i.m. primed + i.n. spike boosted mice (D35P+S, n = 10), i.m. primed + i.m. boosted + i.n. boosted mice (D35P+B+S, n = 9) and i.m. primed + i.n. boosted + i.n. boosted mice (D35P+S+S, n = 10) at day 35 post-priming, analyzed by flow cytometry as in a. c, ELISA measurements of SARS-CoV-2 S1-specific IgA and IgG in the BALF, serum and nasal wash from mice as in b. Data are the mean ± s.e.m. The statistical significance was calculated using one-way ANOVA (b,c). Tukey’s multiple comparisons were performed: *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. Data were pooled from two (b,c) independent experiments. Values shown as zero indicate the absence of detectable cells (b).
