Productive reovirus infection in cell preparations. The cell line SK-Mel28 was exposed to reovirus in suspension. The uninfected cells (a) show no viral-specific signal; note the uniformity of the large neoplastic cells. After reoviral treatment, many cells show a strong red cytoplasmic signal for the viral capsid protein (b). Note that many of the cells show shrunken, darkened nuclei typical of apoptosis (c, higher magnification). The cell line CAL27 was tested for co-expression of reovirus (red signal) and tubulin (brown signal) (d); the insert shows the Nuance converted signal for reovirus (fluorescent red). (e) Shows the Nuance converted tubulin signal (fluorescent green). The merged images for reovirus and tubulin (f) show reovirus protein-positive cells that co-express tubulin as fluorescent yellow, consistent with productive infection.