Fig. 1.

a Kinetics of IBV release from Vero cells. Medium samples from the virus-infected cell cultures incubated at 37 °C were harvested at 2 h intervals and subjected to plaque titration to determine the time course of release of infectious virus. Note that the release of progeny virus starts between 5 and 6 h post-infection (hpi), while the earlier measurements score residual cell-attached virus from the original inoculum. b Immunofluorescence microscopic localization of the IBV N protein in mock-infected Vero cells and at different times after infection. At 6 hpi the anti-N antibodies give a weak punctate pattern, while at 9 and 12 hpi the infected cells typically display strong diffuse staining due to high N expression. Bar, 10 μm