Antigenic analysis of divergent genotypes human Enterovirus 71 viruses by a panel of neutralizing monoclonal antibodies: Current genotyping of EV71 does not reflect their antigenicity

In recent year, Enterovirus 71 (EV71)-associated hand, foot and mouth disease (HFMD) has become an important public health issue in China. EV71 has been classified into genotypes A, B1–B5 and C1–C5. With such genetic diversity, whether the convalescent or recovery antibody responses can cross-protect infections from other genotypes remains a question. Understanding of the antigenicity of such diverse genetic EV71 isolates is crucial for the EV71 vaccine development. Here, a total of 186 clones anti-EV71 MAbs was generated and characterized with Western blot and cell-based neutralization assay. Forty neutralizing anti-EV71 MAbs were further used to analyze the antigenic properties of 18 recent EV71 isolates representing seven genotypes in neutralization assay. We found that most neutralizing anti-EV71 MAbs are specific to conformational epitopes. We also classified the 40 neutralizing anti-EV71 MAbs into two classes according to their reactivity patterns with 18 EV71 isolates. Class I MAb can neutralize all isolates, suggesting conserved epitopes are present among EV71. Class II MAb includes four subclasses (IIa–IId) and neutralizes only subgroups of EV71 strains. Conversely, 18 EV71 strains were grouped into antigenic types 1 and four antigenic subtypes (2.1–2.4). These results suggest that the current genotyping of EV71 does not reflect their antigenicity which may be important in the selection of EV71 vaccine strains. This panel of neutralizing anti-EV71 MAbs may be useful for the recognition of emerging antigenic variants of EV71 and vaccine development.