Fig. 1. Vaccination with Pam₂Cys Spike induces potent Spike-specific neutralizing antibody responses, which is enhanced in the airways with mucosal vaccination.

a Experimental outline. C57BL/6 mice were immunized with Pam₂Cys (P₂C) and Spike protein s.c (blue) or i.n (red) three times, two weeks (wks) apart. Immunogenicity was assessed one week (wk) post final vaccination. Control mice were unvaccinated (UNV; black). b Anti-spike IgG isotypes and IgA titres (log₁₀ scale) in the serum (n = 10 animals) and broncho-alveolar lavage fluid (BALF) (n = 6 animals), determined by ELISA, using the mean +3 SD of the level in 1:100 dilution of sera or 1:40 BALF from unvaccinated mice as the cut-off. c Neutralizing antibody (nAb) titres (log₁₀ scale) in the serum (n = 5 or 6 animals) and BALF (n = 6 animals) of vaccinated mice were determined as the titre needed for 50% inhibition of SARS-CoV-2 Spike-expressing lentivirus in HEK293-ACE2 cells, and d 50% inhibition of SARS-CoV-2 infection in VeroE6 cells. Limits of detection are indicated by the dotted lines. Data points represent individual mice from two independent experiments, means + /− SEM are shown. Statistics: p-values indicated, (b) Mann–Whitney (two-sided test), (c, d) Kruskal–Wallis test, Dunn’s multiple comparisons. Source data are provided as a Source Data file.