FIG. 7.

Ultrastructural localization of HCoV-HKU1 in HAE. Representative transmission electron photomicrographs of HAE inoculated with HCoV-HKU1. (A and B) HAE mock inoculated with the vehicle alone, demonstrating the typical morphological features of the apical surfaces of HAE with cilia (black arrows) and microvilli (white arrows). (C to G) HAE infected with HCoV-HKU1 for 96 h showing the presence of the large numbers of virions (circled) associated with the surfaces of ciliated cells or shed into pericilial regions (black arrows, cilia; white arrows, microvilli). Intracellular virions were also noted inside vesicular structures in the cytoplasm of ciliated cells (D, box). F represents a high-power image of a virion associated with the tip of a microvillus. Scale bars are shown in the lower right of each panel and represent 2 μm in panels A to D and G and 1 μm in panels E and F.