Establishment of tracking system for West Nile virus entry and evidence of microtubule involvement in particle transport

West Nile virus (WNV) is one of flaviviruses and has emerged recently in the United States as a significant cause of viral encephalitis. Although cellular entry of WNV is important for viral pathogenesis, its mechanisms have not been elucidated fully. To explore the entry mechanisms, a virus-particle tracking system in live cells by using fluorescently labeled subviral particles (SVPs) and time-lapse epifluorescence microscopy was established. This study revealed that, following cellular entry, SVP movements could be divided into two phases: early (slow movement) and late (fast movement) phase. Moreover, fast viral particle movements at the late phase correlated with SVP-microtubule association.