Viral entry is initiated by attachment of the virion to functional receptor(s) followed by uncoating to release the viral genome.This process is rather well-characterized for enveloped viruses-the enveloped virus binds host receptors via viral proteins, undergoes further conformational changes, fuses to cell membrane and releases subvirions or viral genome (Fig.1).In contrast, for non-enveloped virus, although a number of host factors that mediate viral attachment have been identified, the molecular mechanism of receptor-triggered uncoating remains poorly understood (Fig.1).