Prunella extracts inhibit virion binding to cells. EIAVWSU5 virions mixed with the Prunella (132 μg/mL of Ames 27664 or 126 μg/mL of Ames 27748) extracts or DMSO and added to ED cells at 4°C to promote binding but prevent internalization. After a two h binding period, the unbound virions were removed, cells were washed and lysed. Cell lysates were immunoblotted for EIAV Gag proteins to detect bound virions, and tubulin served as a loading control. The experiment was repeated three times. A representative blot is shown.