Fig. 6: Vaccination with Spike^Ax IT produces lasting circulating and lung-local neutralising antibodies and IgG1.

C57BL/6 mice were vaccinated as in Fig. 1 and at time points after each vaccination, plasma was collected and assessed for neutralizing antibody titers (NAb) against pseudovirus expressing the ancestral (A) or delta spike proteins (B). C Individual animal comparisons of NAb at four weeks post booster (day 49). D NAb titer in bronchoalveolar lavage fluid (BALF) taken eight weeks after booster vaccination (day 77 after first immunization). Plasma was also tested for the presence of spike-specific IgG1, IgG2c via ELISA (E, F). G Plasma IgG1/IgG2c ratios were calculated for day 49 samples. H BALF was tested for spike-specific IgG1. Dotted lines depict the limit of detection of assays. Graphs depict pooled or representative mean values +/− SEM of two experiments with four or five mice per group, except for (D) and (H) which are representative of a single experiment. For line graphs, statistical analysis on differences between Spike^Ax IT and Spike^Ax IM were performed using a two-way ANOVA with Holm-Sidak multiple comparisons test (A–C, E–F), p < 0.05 (*), p < 0.005 (**), p < 0.0005 (***). For bar graphs, an unpaired two-tailed T-test was performed, p < 0.05 (*), p < 0.005 (**), p < 0.0005 (***).