Fig. 4: Challenging ChAdOx1-NP + M1-RSVF-vaccinated mice with H3N2.

a Vaccination and challenge schematic for the assessment of the protective capacity of ChAdOx1-NP + M1-RSVF against X31 (H3N2) infection and subsequent disease in mice. Mice were prime-boost-vaccinated, then challenged with X31, and culled 6 days later with tissues and fluids harvested. Blood sampling was performed 4 weeks post-prime and 3 weeks post-boost. b Weight change in mice over time post-challenge, measured as % of pre-challenge weight. Significant differences at timepoints between IM-IN and control mouse groups are represented with *, between IM-IN and IM-IM as # and between IN-IN and unvaccinated as @ (*, @ or # =p < 0.05, **=p < 0.01). c Viral load in lungs 6 days post-challenge (M gene copies/μg lung RNA (log₁₀)). d H3N2 NP-specific IgG and IgA levels in serum, NWs, BALF and LHS post-challenge, as measured by ELISA (log₁₀ EU). Median negative control values are displayed as dashed lines. e Levels of antigen-specific CD8⁺ T_RM cells, and relative levels of antigen-specific CD8⁺ T_EM and T_RM, in BAL and lungs post-challenge. T_RM and T_EM cells were defined as CD3⁺CD8⁺CD44⁺CD62L^-CD103⁺CD69⁺, and CD3⁺CD8⁺CD44⁺CD62L^-, respectively, and positive for influenza pentamer H-2Kd TYQRTALV. In boxplots, a “+” symbol represents the group mean. One mouse in group IM-IN did not have detectable Lung T_RM. Group differences for all data were analysed using non-parametric Kruskal-Wallis tests (*=p < 0.05, **=p < 0.01). For all boxplots, whisker endings represent upper and lower extremes, the box bounds represent upper and lower quartiles, respectively, and the central line represents the group median.