FIG. 1.

CVA21 elution from DAF-expressing CHO cells in response to time, temperature, and pH of the incubation media. (A) Radiolabeled CVA21 (5 × 10⁵ cpm) was incubated with DAF-expressing CHO cells (approximately 2 × 10⁷) for 2 h at 4°C; following three washes with phosphate-buffered saline (PBS) to remove unbound virions, cell aliquots were resuspended in 200 μl of PBS and incubated at 37°C for 0, 1, 5, 15, 30, and 60 min to induce viral-particle elution. Levels of CVA21 eluted were determined by liquid scintillation counting (23). Approximately 10 to 15% of input radiolabeled CVA21 bound to DAF-expressing CHO cells (data not shown). (B) Radiolabeled CVA21 was bound to cell surface-expressed DAF at 4°C for 2 h and then eluted by incubation at the appropriate temperature for a further 30 min. (C) Radiolabeled CVA21 was bound to cell surface-expressed DAF at 4°C for 2 h and then eluted by incubation in media of the appropriate pH at 37°C for a further 30 min.