The mature EV71 virion induced a broadly cross-neutralizing VP1 antibody against subtypes of the EV71 virus.

Chia-Ying Wu,Pei-Wen Hsiao,Yen-Hung Chow,Yi-Hsuan Chen,Shu-Ling Yu,Yung-Tsung Chen,Juine-Ruey Chen,Shixia Wang

doi:10.1371/journal.pone.0210553

Abstract

Enterovirus 71 (EV71) has emerged as a neurological virus causing life-threatening diseases in young children and infants. Although EV71 vaccines in development have presented promising results in several clinical trials, the identified key antigen for improving the broad protective efficacy of EV71 vaccines has not been well investigated. In this report, we show that different multiplicities of infection (MOIs) of the B4(E59) virus significantly affect EV71 vaccine production in a serum-free microcarrier bioreactor system. The antigens produced from high MOIs of 10−1 and 10−2 exhibited higher yield and more infectious full particle (FP) contents in the EV71 vaccines than those produced with low MOIs of 10−4 and 10−6, leading to better cross-neutralizing efficacy. The C4(E36) neutralization results showed that only antisera raised from EV71 FPs provided substantial neutralizing titers against C4(E36), whereas empty particles (EPs) of EV71 conferred no efficacy. Competitive ELISA showed that anti-FP mainly binds to FPs and that 20% of antibodies bind to EPs, whereas most anti-EP binds EPs, with only 10% antibodies binding to FPs. VP1-adsorbed anti-FP lost most of the virus neutralization efficiency, suggesting that the VP1 subunit of FP is the major immunogenic antigen determining the ability of the EV71 vaccine to elicit cross-neutralizing antibodies against EV71 virus subtypes. These findings demonstrate that the high-MOI production approach is significantly correlated with FP productivity, thereby improving the cross-neutralization efficacy of an EV71 vaccine and providing the basis for a better vaccine design against widespread EV71 viruses.

Highlights

Enterovirus 71 (EV71), which belongs to the Picornaviridae family, is an icosahedral nonenveloped single-stranded RNA virus
When the culture in the 3-L spinner flask grew to a cell density of approximately 8 × 105 cells/mL after 4 days, the culture was divided into four 1-L spinner flasks (S2a, S2c, S2e and S2g Fig), followed by EV71 virus inoculation at different Multiplicity of infection (MOI) of 10−1, 10−2, 10−4, and 10−6 (Fig 1)
We systematically investigated the effects of inocula with varying MOIs, which influence the dynamics of infectious full particle (FP) and defective empty particles (EPs), on EV71 vaccine production in a serum-free microcarrier bioreactor system

Summary

Introduction

Enterovirus 71 (EV71), which belongs to the Picornaviridae family, is an icosahedral nonenveloped single-stranded RNA virus. During its replicative life cycle, EV71 can simultaneously generate fully infectious RNA-containing virions and immature empty particles. An FP-elicited VP1 antibody confers cross-neutralizing efficacy against EV71 subgenotypes role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘‘author contributions’’ section

Methods

Results

Conclusion