Fig. 4.

Susceptibility of primary murine alveolar epithelial cells to infection by murine coronavirus, MHV-1. (A) Murine cells were cultured as either an ATI or ATII cell phenotype for 5 days, then were inoculated with MHV-1 for 12 or 24 h. Infection was analyzed by immunofluorescence assay of viral nucleocapsid protein (green) and nuclei were stained with DAPI (blue). (B) Cells were cultured on fibronectin (ATI phenotype) and inoculated with MHV-1 or mock-inoculated. Cells were photographed on phase contrast at 24 h p.i. (C) Infection of MHV-1-inoculated ATI and ATII cells was analyzed by plaque assay of supernatant medium at the indicated times. The mean virus titers and standard errors from four replicate experiments are shown.