FIG. 1.

Interaction of ISAV with SHK-1 cells. (A) Kinetics of ISAV binding to SHK-1 cells at pH 7.4. The cells were incubated with trace quantities of ¹²⁵I-labelled virus at 0°C. Cell-associated radioactivity was determined at the indicated times. Shown is a typical experiment (wells in triplicate). (B) Effect of pH on ISAV binding to SHK-1 cells at 0°C. The cells were incubated with ¹²⁵I-labelled virus for 3 h at 0°C in L-15 medium adjusted to the indicated pH. After 3 h the cells were washed three times with binding medium and solubilized in 0.1 N NaOH–1% SDS and cell-associated virus radioactivity was determined. Data are expressed as percentages of control binding at pH 7.4 in each experiment. Values are the means of three different experiments +/− standard deviations (SD). (C) Effect of pH on neuraminidase-sensitive binding of ISAV to SHK-1 cells. Trace quantities of ¹²⁵I-labelled ISAV were allowed to bind to SHK-1 cells for 3 h at 0°C and pH 4.5 or 7.4. After being washed, cells were treated with neuraminidase (5 mg/ml) in L-15 medium for 90 min at 0°C. The cells were washed twice with L-15 medium before cell-associated radioactivity was determined. Data are expressed as percentages of control. Values are the means of three different experiments +/− SD.