Figure 6. Virus infection and pathological changes in the lungs of mice inoculated with the recombinant H7N9 viruses.

Eight- to ten-week-old female C57BL/6 mice (n = 3/group/time-point) were inoculated intranasally with 50 μl PBS containing 10³ TCID₅₀ (a–c,e–g,i–k) or 10⁵ TCID₅₀ (d,h,l) of the recombinant A/Anhui/1/2013 (H7N9) viruses. Animals were euthanized at 1 (a–d) and 5 (e–l) dpi, respectively, and the lung lobes were used for immunohistochemical staining with the anti-NP antibody (a–h) and standard hematoxylin and eosin (H&E, Sigma) staining (i–l). Slides were shown to represent the pathological changes and virus replication at different time points post-inoculation of rgAH1-KD (a,e,i), rgAH1-KN (b,d,f,j) and rgAH1-EN (c,g,h,k,l). rgAH1-KD (wild type virus carrying PB2-627K and 701D), rgAH1-KN (with PB2-627K and 701N) and rgAH1-EN (with PB2-627E and 701N). Scale bars indicate 100 μm.