Figure 3

Eosinophilic infiltration in the lungs of vaccinated mice after challenge infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Lung specimens were collected at the humane endpoint or 10 d post-infection. The study schedule is described in detail in Fig. 2. (a) Representative histopathological findings from mice with the highest levels of eosinophilic infiltration. Infiltration was detected using eosinophilic staining with a combined eosinophil­mast cell (C.E.M.) staining kit. Scale bar = 100 μm. Green arrows indicate representative eosinophils. Br, bronchus; V, blood vessel. (b) Number of eosinophils per lung section. The number of eosinophils in five regions with an area of 147,000 μm² around the pulmonary bronchioles of each mouse was counted at 40 × magnification. Each circle represents the results of individual animals. The bar represents the mean number of eosinophils (error bars indicate standard deviation). Statistical significance was determined using a nonparametric comparison test, followed by the Kruskal–Wallis test (*P < 0.05 and ***P < 0.001).