α2,3-and α2,6-linked sialic acids are important for cell binding and replication of Newcastle disease virus in chicken primary neuronal cells

Velogenic Newcastle disease virus (NDV) causes encephalitis and severe neurological disorders in avian species. Sialic acid (SA) has been considered as a receptor for NDV infection and determining tissue tropism. The neurotropic mechanism of NDV in birds is completely unknown. Here we have investigated the role of viral receptor SA in neurotropism of NDV in chickens. We determined that alpha 2,3- and alpha 2,6-linked SA receptors were implicated in NDV encephalitis and viral binding to primary neuronal cells using immuno-histofluorescence and virus-cell binding assay. Both SA receptors were found to co-localize with velogenic strain F48E9 in neuropathological lesions of chicken brains after infection through intraocular-nasal routes. The replication of velogenic F48E9 in primary neuronal cells was more efficient than that of lentogenic strain LaSota. The virus-neuronal cell binding capabilities of both the velogenic and the lentogenic strains have no difference. Furthermore, the cell-binding capability and the replication of both strains were significantly decreased by pretreatment with sialidases in neuronal cells. These results demonstrated that alpha 2,3- and alpha 2,6-linked SA receptors were important for the initiation of NDV infection in the chicken nervous system. This study should provide preliminary evidence for a better understanding of the neurotropism of NDV in chickens.