Immunofluorescence analysis of HHV-7 antigen (A) and cyclin B (B) expression in uninfected and HHV-7–infected SupT1 cells. The same cells are viewed by phase contrast microscopy (top panels) and fluorescence microscopy (bottom panels). In (A), note that enlarged cells, characteristic of HHV-7 infected cultures, are positively stained for expression of viral antigens. In (B), note that, whereas cyclin B expression is heterogenous among small cells, enlarged HHV-7–infected cells always exhibit an intense staining for cyclin B. Original magnification × 400. Representative fields are shown.