FIG. 5.

Effect of heparin on different PRRSV strains. PRRSV 94V360 (solid bars), LV (striped bars), US-5 (shaded bars), and VR-2332 (open bars) were incubated for 1 h at 37°C with different concentrations of heparin. PAM were inoculated with the mixtures, washed after 2 h of incubation at 37°C to remove unbound virus, and finally fixed after a total infection time of 10 h. The data represent the means ± standard deviations (error bars) of triplicate assays. The analysis of variance test and the least-significant-difference post hoc test were performed to compare the sensitivities of the different PRRSV strains to heparin, with heparin at both at 250 and 2,500 μg/ml. A different symbol on top of two bars indicates that the number of infected cells of these two PRRSV strains are significantly different at the given concentration of heparin (P < 0.01).