Fig. 9. cHA-ΔNS1-LAIV vaccination protects mice from severe bronchointerstitial histopathology after seasonal virus challenge.

Four weeks post-final-boost, mice were challenged with a QIV-matched IVR-180 using a lethal dose of 100 LD₅₀. On day 5 post infection left lung lobes were fixed in formalin and were processed for H&E staining and IHC. Lungs were scored by a blinded independent veterinary pathologist to assess pathology features. a Representative images from an animal derived from each group are shown as H&E staining (top panels) and NP IHC immunostaining (bottom panels). Peribronchiolar (black hashed outlines) and perivascular inflammation were observed to variable degrees in all influenza virus-inoculated animals regardless of vaccination group. Normal naïve lungs are represented for comparison. Scale bar = 100 microns. All images acquired at 200x total magnification. b Scoring for IHC (α-NP), c scoring for interstitial pathology, d. scoring for airway epithelial integrity and e. cumulative scores based on the assessed parameters. Scoring for individual parameters range from 0–5: 0 no pathology and 5 being severe pathology. Each dot is derived from a single animal and data is shown as mean ± SEM.