Immunoreactivity Analysis of the Nonstructural Proteins of Human Enterovirus 71

Human enterovirus 71 (EV-A71) is one of the main etiological agents of hand, foot, and mouth disease (HFMD), which has been prevalent mainly in the Asia-Pacific region in the past several decades. The nonstructural proteins of EV-A71 will be expressed significantly during viral replication in host cells after EV-A71 infection. For the determination of the antibodies response against nonstructural proteins of EV-A71, in this study, the complete 2ABC, 3ABC, and 3D proteins were expressed in Escherichia coli and were then studied for their immunoreactivity by immunoblot assay and indirect enzyme-linked immunosorbent assay (ELISA), respectively. Three His-tagged fusion proteins were expressed effectively in E. coli, which were in agreement with the expected molecular mass. The results from immunoblot assay and indirect ELISA showed that all three purified fusion proteins can react with IgG antibodies from EV-A71-infected patients, but can hardly be recognized by IgG antibodies derived from mice or rabbits immunized by inactivated EV-A71 virus particles. The IgG antibody response against nonstructural proteins of EV-A71 is associated with viral infection or replication, which indicate that these nonstructural proteins could be used as candidate antigen for early diagnosis of EV-A71 infection, or to distinguish the EV-A71-specific antibodies after viral infection from inactivated vaccine immunization.