PAC-3066 does not affect HN-receptor interaction or neuraminidase activity. (A) Sensitivity of HN-receptor binding to viral entry inhibitors of cell monolayers expressing clinical isolate HPIV3 HN, incubated with either PAC-3066, zanamivir, or DMSO. Percent inhibition relative to that for DMSO-treated cells is shown. Each point represents the mean from 3 experiments, each of which was performed in triplicate, ± SEM. (B) The inhibition of neuraminidase activity in the presence or absence of the indicated compounds was assayed at 37°C and pH 5 on cell monolayers transiently expressing HPIV3 clinical isolate HN. Each bar represents the results from triplicate experiments, each of which was performed in triplicate, ± SEM.