Fig. 4: YFV-specific immunity and protection in mice.

a Ifnar^-/- mice were vaccinated intraperitoneally with 250 (circles) or 2500 PFU (squares) of either YF-EBO, YF17D or sham. A subset of mice vaccinated with 250 PFU and all mice vaccinated with 2500 PFU were sacrificed 4 weeks post-vaccination for spleen collection. Remaining mice vaccinated with 250 PFU were challenged intracranially with 3000 PFU of YF17D after which they were monitored daily for 2 weeks for the development of disease symptoms. b YF17D-specific neutralizing antibody (nAb) titers at 4 weeks post-vaccination with 250 PFU (circles; YF-EBO n = 8; YF17D n = 8; sham n = 6) or 2500 PFU (squares; YF-EBO n = 5; YF17D n = 5). c ELISpot counts of IFNγ-secreting cells after YFV NS3 peptide stimulation of isolated splenocytes from Ifnar^-/- mice that were vaccinated with 250 PFU (circles; YF-EBO n = 14; sham n = 6) or 2500 PFU (squares; YF-EBO n = 5; YF17D n = 5). A representative image of an ELISpot well from each group is shown below the x-axis. d Percentage of IFNγ-expressing CD8⁺ cells after YFV NS4B peptide pool stimulation of splenocytes from mice vaccinated with 250 PFU (YF-EBO n = 8; YF17D n = 7; sham n = 7). One sham mice with high background staining in ICS was excluded from the analysis because it was detected as an outlier with ROUT method (Q = 0.1%). e Mean weight evolution, error bars indicate SEM (YF-EBO n = 8; YF17D n = 8; sham n = 6), and f survival curves after challenge, number of surviving mice at study endpoint are indicated within parentheses. g YF17D infectious viral loads in the brain at day of euthanasia determined by virus endpoint titration on BHK-21J cells. Dashed line indicates limit of detection (LOD). Data are median ± IQR and two-tailed Kruskal–Wallis test was applied followed by Dunn’s multiple comparison (b–d, g) and a log-rank test was applied to compare survival curves (f), significant p values < 0.05 are indicated.