Binding and internalization of CPV-VLPs labeled with OG-488 into transferrin receptor expressing cells. Cells differing in level of transferrin receptor expression, TRVb1 (express TfRs) and TRVb (low or lacking TfR expression) were exposed to CPV-VLPs. Internalized dye-labeled CPV-VLPs were detected by fluorescence confocal microscopy. TOTO-3 (blue) was used for staining the nuclei. (A) TRVb1 cells with internalized dye-derivatized CPV-VLPs, are seen as green areas in the cytoplasm, and (B) TRVb cells show lack of VLP internalization. Scale bar, 25 μm.