Mapping Enterovirus A71 Antigenic Determinants from Viral Evolution

Abstract

Human enterovirus A71 (EV-A71) belongs to the Enterovirus A species in the Picornaviridae family. Several vaccines against EV-A71, a disease causing severe neurological complications or even death, are currently under development and being tested in clinical trials, and preventative vaccination programs are expected to start soon. To characterize the potential for antigenic change of EV-A71, we compared the sequences of two antigenically diverse genotype B4 and B5 strains of EV-A71 and identified substitutions at residues 98, 145, and 164 in the VP1 capsid protein as antigenic determinants. To examine the effects of these three substitutions on antigenicity, we constructed a series of recombinant viruses containing different mutation combinations at these three residues with a reverse genetics system and then investigated the molecular basis of antigenic changes with antigenic cartography. We found that a novel EV-A71 mutant, containing lysine, glutamine, and glutamic acid at the respective residues 98, 145, and 164 in the VP1 capsid protein, exhibited neutralization reduction against patients' antisera and substantially increased virus binding ability to human cells. These observations indicated that this low-neutralization-reactive EV-A71 VP1-98K/145Q/164E mutant potentially increases viral binding ability and that surveillance studies should look out for these mutants, which could compromise vaccine efficacy. IMPORTANCEEmerging and reemerging EV-A71 viruses can cause severe neurological etiology, primarily affecting children, especially around Asia-Pacific countries. We identified a set of mutations in EV-A71 that both reduced neutralization activity against humoral immunity in antisera of patients and healthy adults and greatly increased the viral binding ability to cells. These findings provide important insights for EV-A71 antigenic determinants and emphasize the importance of continuous surveillance, especially after EV-A71 vaccination programs begin.

Neutralizing Antibodies against Enteroviruses in Patients with Hand, Foot and Mouth Disease

“…Of note, the emergence of C4 in 2018 resulted in a severe outbreak that caused >130,000 hospitalizations and 17 deaths. The underlying mechanism that determines the emergence of certain subgenogroups in specific localities remains a puzzle; it may be a consequence of a complex interplay among the pathogen, the hosts, and public health response, of which antigenic evolution might play a role (26,27). The fact that all serum samples from subgenogroup B5-infected patients collected before 2018 could neutralize the 2018 C4 virus suggests that immunity developed as a consequence of natural infection with subgenogroup B5 could provide protection against subgenogroup C4.…”

Enterovirus A71: virulence, antigenicity, and genetic evolution over the years

“…These data suggest the difference in antigenic properties and the antigenic diversity among the various genotypes of EV-A71. Recently, Huang et. al.…”

“…1). By creating reverse-genetics EV-A71 viruses containing mutations at VP1-98 K, VP1-145Q, and VP1-164E, they had found that these mutants significantly decreased neutralizing titers by 4-fold against the antisera of 3 of the 6 healthy individuals [28]. However, it was also noted that none of the single mutation alone was responsible for the antigenic changes, but rather all 3 mutations cooperatively influence the viral antigenic phenotype.…”

“…PSGL-1 alone was found to be insufficient in enhancing EV-A71 infection in mice [26], while SCARB2 was found to be sufficient in causing neurological diseases in mice due to its roles in viral attachment, internalization, and uncoating [27]. In addition, some of the residues such as VP1-98, − 145, and − 164 [28], are antigenic sites for antibody recognition. The remaining P2 and P3 regions contain the non-structural proteins 2A to 2C and 3A to 3D, respectively.…”

Enterovirus A71 Containing Codon-Deoptimized VP1 and High-Fidelity Polymerase as Next-Generation Vaccine Candidate

“…VP1-D31G confers growth and fitness advantages in the CNS in humans (46). In addition, we previously reported that genetic variations in VP1-K98E, -E145Q, and -D164E cooperatively cause antigenic change of EV-A71 (47). To minimize quasispecies of viral genomes, in this study we applied a codon-deoptimized genome and highfidelity 3D polymerase in a reverse genetics preparation to obtain a genetically stable vaccine seed candidate with low virulence.…”