Extended Data Fig. 8: Mucosal recall responses were comparable between PBS-treated and isotype control antibody-treated P+S mice.

a, Schematic of the experimental setup showing C57BL/6J mice were primed i.m. with mRNA-LNPs at day 0, i.n. boosted with an unadjuvanted SARS-CoV-2 spike protein at day 14, followed by intranasal and intraperitoneal treatment with PBS, mouse IgG1, polyclonal American hamster, rat IgG2b isotype antibodies, and a CD4 depleting antibody at days 0, 2, 4, and 6 post intranasal boosting, followed by lung, BALF, serum collection at day 7 post intransal booster. b, Number of extravascular CD44⁺Tet⁺CD4⁺ T cells, CD44⁺Tet⁺CD8⁺ T cells, RBD⁺CD38⁺GL7^-IgM^-IgD^- CS B cells, and RBD⁺IgA⁺ ASCs in the lung of naïve C57BL/6J mice (D0, n = 4); P + S mice treated with PBS (D21^PBS, n = 5), mouse IgG1 antibody (D21^{mouse IgG1}, n = 5), polyclonal Armenian hamster IgG antibody (D21^{polyclonal Armenian hamster}, n = 5), rat IgG2b antibody (D21^{rat IgG2b}, n = 5); and CD4 depleting antibody (D21^CD4, n = 5) at day 21 post-priming analyzed by flow cytometry as in a. c, ELISA measurements of SARS-CoV-2 S1-specific IgA and IgG in the BALF and serum from mice as in b. AUC, Area under the curve. Mean ± SEM. Statistical significance was calculated by one-way ANOVA, and Tukey’s multiple comparisons (b,c) were performed; *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. Data were representative of an experiment (b,c). Values shown as zero indicate the absence of detectable cells (b).

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