Effect of fucoidan on viral penetration. Vero cells monolayers were infected with NDV at 4°C in the absence of fucoidan and then shifted to 37°C to permit penetration of the adsorbed virus in the presence of fucoidan. The effects of fucoidan were evaluated using a PFU inhibition assay. The data shown are the mean ± SD of triplicate experiments. The asterisks indicate a significant difference between the treatment and viral control (*p<0.05).