Neutralizing Antibodies Induced by Recombinant Virus-Like Particles of Enterovirus 71 Genotype C4 Inhibit Infection at Pre- and Post-attachment Steps

Zhiqiang Ku,Zhiguo Su,Yicun Cai,Xiaohua Ye,Yan Li,Zhong Huang,Xulin Huang,Qingwei Liu,Xia Jin

doi:10.1371/journal.pone.0057601

Abstract

BackgroundEnterovirus 71 (EV71) is a major causative agent of hand, foot and mouth disease, which has been prevalent in Asia–Pacific regions, causing significant morbidity and mortality in young children. Antibodies elicited by experimental EV71 vaccines could neutralize infection in vitro and passively protect animal models from lethal challenge, indicating that neutralizing antibodies play an essential role in protection. However, how neutralizing antibodies inhibit infection in vitro remains unclear.Methods/FindingsIn the present study, we explored the mechanisms of neutralization by antibodies against EV71 virus-like particles (VLPs). Recombinant VLPs of EV71 genotype C4 were produced in insect cells using baculovirus vectors. Immunization with the VLPs elicited a high-titer, EV71-specific antibody response in mice. Anti-VLP mouse sera potently neutralized EV71 infection in vitro. The neutralizing antibodies in the anti-VLP mouse sera were found to target mainly an extremely conserved epitope (FGEHKQEKDLEYGAC) located at the GH loop of the VP1 protein. The neutralizing anti-VLP antisera were able to inhibit virus binding to target cells efficiently. In addition, post-attachment treatment of virus-bound cells with the anti-VLP antisera also neutralized virus infection, although the antibody concentration required was higher than that of the pre-attachment treatment.ConclusionsCollectively, our findings represent a valuable addition to the understanding of mechanisms of EV71 neutralization and have strong implications for EV71 vaccine development.

Highlights

Enterovirus type 71 (EV71) is a member of the enterovirus genus of the picornaviridae family
Collectively, our findings represent a valuable addition to the understanding of mechanisms of Enterovirus 71 (EV71) neutralization and have strong implications for EV71 vaccine development
The P1/3CD co-infected sample produced a major band of,38 kDa and a minor band of,28 kDa (Figure 2D), which are expected for processed VP0 and VP2 subunit proteins. These results indicate that only the IExBac-P1/ IExBac-3CD combination resulted in efficient production and correct processing of the structural protein P1, which is the prerequirement for EV71 particle assembly

Summary

Introduction

Enterovirus type 71 (EV71) is a member of the enterovirus genus of the picornaviridae family. It possesses a single-stranded, positive-sense RNA genome of ,7.4 kb, which is packaged in an icosahedral capsid. EV71 is the major causative agent of hand, foot and mouth disease (HFMD), which frequently occurs in children under the age of 5 years [3,4]. Enterovirus 71 (EV71) is a major causative agent of hand, foot and mouth disease, which has been prevalent in Asia–Pacific regions, causing significant morbidity and mortality in young children. Antibodies elicited by experimental EV71 vaccines could neutralize infection in vitro and passively protect animal models from lethal challenge, indicating that neutralizing antibodies play an essential role in protection. How neutralizing antibodies inhibit infection in vitro remains unclear

Methods

Results

Conclusion