Figure 1

Histopathologic and IHC analyses of murine lungs. (a) The histopathologic images of infected lungs (H&E) portray considerably greater extent of epithelial thickening and infiltration into the lungs at 7 dpi than 15 dpi (red circles). At 7 dpi, minimal repair processes were observed other than wound healing (fibrin). In comparison, at 15 dpi, new epithelial and connective tissue filled the alveolar spaces (green circles). (b) Expression of viral NS1 at 7 dpi indicated presence of virus, whereas complete viral clearance was evident at 15 dpi. (c) Dividing cells (PCNA-positive) and AT2 pneumocytes (SP-C-positive) were stained by IHC to assess lung regeneration at both time-points. (d) Higher percentages of PCNA-positive proliferating cells were noted in infected lungs at 7 dpi and especially at 15 dpi. (e) PCNA and SP-C double-positive dividing cells were significantly higher in infected murine lungs at 15 dpi. N = 4 per group per time-point. Asterisks denote P < 0.05 compared to uninfected control.