Antigenic characteristics of the complete and truncated capsid protein VP1 of enterovirus 71.

The complete VP1 protein of enterovirus 71 (EV71) and a series of truncations were expressed in Escherichia coli and their antigenic characteristics were studied. Immunoblot analysis showed the major immunoreactive region of the VP1 protein was located in the N-terminal portion at position of amino acid (aa) 1-100. The complete VP1 possessed strong cross-reactivity with antisera against coxsackievirus A16 (CA16) and echovirus 6 (Echo6), while the truncated fragment at position 1-100 aa only had weak cross-reactivity. Moreover, an EV71-specific linear epitope at position 94-105 aa was identified using two EV71-specific mAbs (2B9 and 5B7) with indirect ELISA, but could not be recognized by antibodies against EV71 virus particles. The complete and all of truncated VP1 proteins except His-VP1(202-297) and GST-VP1(202-248) failed to elicit a significant neutralizing antibody response in mice. His-VP1(202-297) and GST-VP1(202-248) containing neutralizing epitope(s) could be recognized only by anti-EV71 mouse sera but not rabbit or human sera. These findings may contribute to a further understanding of antigenic characteristics of the capsid protein VP1 and may be helpful to the development of diagnostic reagents and vaccines.