Characterization of enterovirus 71 capsids using subunit protein-specific polyclonal antibodies.

Enterovirus 71 (EV71), a member of the Enterovirus genus of the Picornaviridae family, is one of the major causative agents of hand-foot-and-mouth disease (HFMD), which is prevalent in the Asia-Pacific region. In this article, a set of capsid subunit protein-specific antibodies was used to characterize the EV71 structural protein processing and to determine the composition and assembly of EV71 capsids. SDS-PAGE and Western blot analyses showed that the capsids of a purified EV71 preparation, which lacked viral infectivity, were composed of processed VP0, VP1 and VP3, all of which co-assembled into particles. Analyses of infectious EV71-containing cell lysate revealed the presence of VP2, in addition to VP0, VP1 and VP3, suggesting that the cleavage of VP0 into VP2 and VP4 is important for infectivity. Immunofluorescent staining with the three specific antibodies demonstrated that the capsid subunit proteins co-localized in the cytoplasm of cells infected with EV71. The results add new information on the processing, assembly and localization of EV71 capsid proteins, and demonstrate the usefulness of the capsid protein-specific antibodies for virological investigation and for development of vaccines and diagnostic reagents.