FIG. 3.

Immunofluorescence staining of protein E in BHK-21 cells at 37°C (A) and 28°C (B). Cells were transfected with in vitro RNA transcripts of the clones indicated on the left (left panels) and stained with a polyclonal serum detecting protein E. Supernatants with or without trypsin were transferred onto fresh BHK-21 cells and stained again (middle and right panels, respectively). The mutant prM(ΔR88/Y76C) could be passaged five times with increasing infection efficiencies, as seen by the number of fluorescent cells (bottom panel).