Plaque-purified Taiwan-isolated Japanese encephalitis virus (JEV) strain RP-9 [28] was used as a positive control for the study of GAG effect on the virus-cell attachment. The adsorption of JEV was performed with serum-free RPMI medium at 37°C for 1 h. Virus-infected cells were incubated in RPMI containing 2% fetal bovine serum (FBS). Virus titers were determined by plaque assay in BHK-21 (baby hamster kidney) cells, which were maintained in RPMI 1640 with 5% FBS, 2 mM L-glutamine, 100 mg/mL of streptomycin, and 100 IU/mL of penicillin. The medium and culture reagents are obtained from Invitrogen (Carlsbad, CA, USA).