Figure 2.

Effect of heparin or heparinase I treatment on plaque formation of mutant viruses. (a) Viruses diluted to 100-200 PFU/200 μl were incubated with heparin at the concentrations indicated for 1 h at 37°C. Then the plaque assay was performed on BHK-21 cells as previously described [16]. (b) Confluent BHK-21 cell monolayers were treated with heparinase I at the concentrations as indicated. After washing three times with PBS, the cells were infected with viruses diluted to 100-200 PFU in 200 μl. Plaque formation was analyzed as described.