Characterization of an Isotype-Dependent Monoclonal Antibody against Linear Neutralizing Epitope Effective for Prophylaxis of Enterovirus 71 Infection

Abstract

BackgroundEnterovirus 71 (EV71) is the main causative agent of Hand, Foot and Mouth disease (HFMD) and is associated with severe neurologic complications and mortalities. At present, there is no vaccine or therapeutic available for treatment.Methodology/Principal FindingIn this study, we generated two mAbs, denoted as mAb 51 and 53, both targeting the same linear epitope on VP1 capsid protein, spanning amino acids 215–219. In comparison, mAb 51 belonging to isotype IgM possesses neutralizing activity in vitro, whereas, mAb 53 belonging to isotype IgG1 does not have any neutralizing ability, even towards its homologous strain. When mAb 51 at 10 µg/g of body weight was administered to the 2-week-old AG129 mice one day prior to lethal challenge, 100% in vivo passive protection was observed. In contrast, the isotype control group mice, injected with an irrelevant IgM antibody before the challenge, developed limb paralysis as early as day 6 post-infection. Histological examination demonstrated that mAb 51 was able to protect against pathologic changes such as neuropil vacuolation and neuronal loss in the spinal cord, which were typical in unprotected EV-71 infected mice. BLAST analyses of that epitope revealed that it was highly conserved among all EV71 strains, but not coxsachievirus 16 (CA16).ConclusionWe have defined a linear epitope within the VP1 protein and demonstrated its neutralizing ability to be isotype dependent. The neutralizing property and highly conserved sequence potentiated the application of mAb 51 and 53 for protection against EV71 infection and diagnosis respectively.

A Strain-Specific Epitope of Enterovirus 71 Identified by Cryo-Electron Microscopy of the Complex with Fab from Neutralizing Antibody

“…Linear epitopes of EV71 have been characterized in several studies using synthetic peptides or inactivated whole virus (18)(19)(20)(21). The epitopes, which induce cross-neutralization activity, are located at the rim of the canyon on VP1 and VP2, where SCARB2 binds (18)(19)(20).…”

“…The epitopes, which induce cross-neutralization activity, are located at the rim of the canyon on VP1 and VP2, where SCARB2 binds (18)(19)(20). Strain-specific neutralizing antibodies that recognize conformation-dependent epitopes have been generated and classified (22); however, the epitopes have not been mapped.…”

Phage Display-Derived Cross-Reactive Neutralizing Antibody against Enterovirus 71 and Coxsackievirus A16

“…In recent years, substantial progress has been made in the discovery of an anti-EV71 antibody, and highly potent and broad neutralizing antibodies have been isolated from a variety of animal models (19)(20)(21)39). These antibodies confer protection against EV71 lethal challenge in passively immunized animals.…”

“…These peptide-induced antibodies cross-neutralize EV71 and protect mice from lethal challenges with homologous and heterologous EV71 strains (18). An immunoglobulin M monoclonal antibody (mAb) targeting a highly conserved epitope (amino acids 215-219 in EV71 VP1) confers effective protection against lethal EV71 challenge in vivo when administrated at 10 mg/g body weight (19). In addition, a cross-neutralizing epitope in VP2 (amino acids 141-155) has been identified through overlapped synthetic peptide mapping.…”

Human picornaviruses associated with neurological diseases and their neutralization by antibodies

“…3a, b). Three continuous neutralizing epitopes have been localized to VP1 residues 163-177 (known as SP55) and 215-219 (part of SP70, which localizes to residues 208-222), and to region 240-260 [149][150][151]. SP55 has 85-100 % sequence identity within genotypes A, B1-B5 and C1-C4 and SP70 is 100 % conserved across these genotypes and thus is universal for them [150].…”