Virus binding to host cell surface receptors is critical for determining tissue tropism and viral pathogenesis. It has been shown that H or HS may serve as a coreceptor in fibroblast cells for infection by the IBV Beaudette strain, but not the M41 strain [18] . In this study, highly sulfated GAG, such as H and DS, and common GAG, such as HS and CS, were tested to determine whether they possess different neutralizing effects on binding of Taiwan-isolated IBV to ATE cells. JEV was used as a positive control for the evaluation of the GAG effect [28] . Figure 5A shows that both H and DS at 7.5 lg/mL effectively blocked JEV infection in BHK-21 cells, as previously reported [28] . Complete inhibition of JEV infection was achieved when the concentrations of H and DS were elevated to 30 lg/mL. Although low concentrations of HS and CS did not affect JEV infection, a modest neutralizing effect was observed when the concentrations of HS and CS were elevated to 30 lg/mL. In contrast to the JEV results, even when all of the tested GAG were applied at 2.0 mg/mL, no significant inhibitory effects were observed on the infection of primary ATE cells by TW2575/98 (Fig. 5B ). In addition, the GAG did not alter the cell tropism of IBV on cilia cells or goblet cells (data not shown). These results strongly suggest that the binding affinity of GAG for IBV is too low to interfere with viral entry into tracheal epithelial cells. In this study, we showed that primary ATE cells exhibit the same cell composition as tracheal epithelia and can be passaged and amplified in a convenient and efficient way. These cells support IBV viral replication and viral release, providing an ideal system to amplify respiratory viruses and characterize their pathogenesis.