Recent advances in the molecular epidemiology and control of human enterovirus 71 infection

doi:10.1016/j.coviro.2012.02.009

Current Opinion in Virology

Volume 2, Issue 2, April 2012, Pages 199-205

https://doi.org/10.1016/j.coviro.2012.02.009 Get rights and content

Human enterovirus 71 (HEV71) has emerged as an important cause of viral encephalitis in the Southeast Asia over the past 15 years. A pattern of increased epidemic activity and endemic circulation of HEV71 has been observed since 1997 and is associated with the regular emergence of new genetic lineages. Although the reason for this increase in HEV71 circulation remains unknown, evidence is accumulating that recombination events may drive the evolution of new genetic lineages. Prevention of HEV71 epidemics is likely to require the development of an effective vaccine. Fortunately, several candidate EV71 vaccines have recently been reported, several of which have been shown to be effective in animal models and commenced clinical trial in 2010. Furthermore, ongoing investigations into the molecular basis of HEV71 infection and virulence have pointed the way towards novel approaches to live attenuated vaccine development.

Highlights

► Human enterovirus 71 has emerged as a major cause of viral encephalitis in the Southeast Asia over the past fifteen years. ► Increased epidemic activity of HEV71 is associated with the regular emergence of new genetic lineages. ► The reason for this increase in HEV71 circulation remains unknown. ► Prevention of HEV71 epidemics is likely to require the development of an effective vaccine. ► Several candidate EV71 vaccines have recently been reported, several of which have been shown to be effective in animal models.

Introduction

Human enterovirus 71 (HEV71) is member of the Genus Enterovirus, Family Picornaviridae, which comprises a group of small, non-enveloped, positive sense single-stranded RNA viruses. HEV71 is a member of the Human Enterovirus A (HEVA) species, which cause hand-food-and-mouth disease (HFMD) in young children. However, infection with HEV71 carries an additional risk of acute neurological disease [1].

HEV71 has emerged as an important cause of viral encephalitis in the Southeast Asia in the past 15 years [2^•]. A pattern of increased epidemic activity and endemic circulation of HEV71 has been observed in the region since 1997 and is associated with the regular emergence of new genetic lineages of HEV71. However, the reason for this increase in HEV71 circulation remains unknown.

In this article, I will review recent developments in the molecular epidemiology of HEV71 infection, in the development of animal models of HEV71 infection and in progress towards the development of HEV71 vaccines.

Section snippets

HEV71 genome structure

The 7.5 kb RNA genome of HEV71 has a single open reading frame (ORF) encoding a polyprotein, flanked by 5′ and 3′ untranslated regions (UTRs). The polyprotein is cleaved into 11 proteins: the four capsid proteins (P1 – VP1, VP2, VP3, VP4), and seven non-structural proteins (P2 – 2A, 2B, 2C; P3 – 3A, 3B, 3C, 3D) [1, 2•]. The 5′UTR of HEV71 contains six putative stem-loop structures [3, 4]. Stem-loop I is called the HEV71 cloverleaf and is involved in viral RNA synthesis [5], whilst stem-loops

Molecular epidemiology of HEV71

HEV71 was first isolated in California in 1969 from the stool of an infant with encephalitis [7]. For the next 28 years it caused relatively minor and infrequent epidemics [1]. However, in the past 15 years HEV71 has been associated with increasingly large epidemics in Southeast Asia [1, 2•, 8].

The highly variable sequences of the HEV71 VP1 gene have been used to group HEV71 isolates into four genogroups (A, B, C, D) [9, 10]. Virus isolates from the same genogroup have more than 92% nucleotide

Animal models of HEV71 infection and disease

One of the ongoing challenges in studying the pathogenesis of HEV71 infection is the lack of a suitable animal model. The most authentic animal model of HEV71 infection is the cynomolgus macaque model [38, 39, 40], which mimics human disease closely. However, owing to financial and ethical constraints, this model has not been used extensively. Therefore, several mouse models have been developed to allow investigations of pathogenesis and to perform efficacy studies of vaccines. Most of the

HEV71 vaccine research and development

Several strategies are currently being employed to develop a HEV71 vaccine. The most straightforward of these strategies is to develop inactivated whole virus vaccines, which have been found to confer good protection in animal models. Ong et al. [53] developed a formaldehyde inactivated whole virus vaccine from a mouse-adapted strain of a subgenogroup B3 clinical isolate and showed that active immunisation of infant outbred ICR mice provided complete protection against lethal challenge with the

Conclusion

Human enterovirus 71 (HEV71) has emerged as an important cause of viral encephalitis in the Southeast Asia over the past 15 years. Several distinct lineages from genogroups B and C of HEV71 have evolved and circulated widely in Southeast Asia during this time. Recent studies suggest that recombination events may be the primary driver in the evolution of new genetic lineages. There have been several recent reports of candidate HEV71 vaccines, including formalin-inactivated whole virus, DNA, SVP,

References and recommended reading

Papers of particular interest, published within the period of review, have been highlighted as:

• of special interest
•• of outstanding interest

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Advances in anti-EV-A71 drug development research
2024, Journal of Advanced Research
Enterovirus A71 (EV-A71) is capable of causing hand, foot and mouth disease (HFMD), which may lead to neurological sequelae and even death. As EV-A71 is resistant to environmental changes and mutates easily, there is still a lack of effective treatments or globally available vaccines.
For more than 50 years since the HFMD epidemic, related drug research has been conducted. Progress in this area can promote the further application of existing potential drugs and develop more efficient and safe antiviral drugs, and provide useful reference for protecting the younger generation and maintaining public health security.
At present, researchers have identified hundreds of EV-A71 inhibitors based on screening repurposed drugs, targeted structural design, and rational modification of previously effective drugs as the main development strategies. This review systematically introduces the current potential drugs to inhibit EV-A71 infection, including viral inhibitors targeting key sites such as the viral capsid, RNA-dependent RNA polymerase (RdRp), 2C protein, internal ribosome entry site (IRES), 3C proteinase (3C^pro), and 2A proteinase (2A^pro), starting from each stage of the viral life cycle. Meanwhile, the progress of host-targeting antiviral drugs and their development are summarized in terms of regulating host immunity, inhibiting autophagy or apoptosis, and regulating the cellular redox environment. In addition, the current clinical methods for the prevention and treatment of HFMD are summarized and discussed with the aim of providing support and recommendations for the treatment of enterovirus infections including EV-A71.
The stability and immunogenicity of formalin-inactivated Enterovirus A71 whole virion vaccine after ten years of low temperature storage
2023, Journal of Microbiology, Immunology and Infection
Vaccine stability is an important issue for vaccine development, which affects whether the vaccine product is effective within a certain period of time in each progress. Hand, foot, and mouth diseases (HFMD) is an epidemic disease in young children usually caused by Enterovirus A group viruses, and the Enterovirus A71 (EV-A71) had caused several pandemics and public health issues around the world. After two decades of research and development, formalin-inactivated EV-A71 (FI-EV-A71) vaccines are the first to complete the phase III clinical trials for protection against EV-A71 infection. Currently, the shelf life of FI-EV-A71 vaccine product is set to be within 18 months, but the stability and the effectiveness of the FI-EV-A71 whole virion when stored long-term at low temperature remains undetermined.
Assessing the long-term storage properties of viral particles facilitates flexibility in manufacturing of vaccine products. In this study, the stability profiles of FI-EV-A71 vaccine lots and bulks after long-term of low temperature storage were analyzed by protein tests, particle measurement and animal immunization study.
After over ten years of storage, the reduction of protein concentration in the FI-EV-A71 bulk samples is less than 30 % and the antigenic content remained in a suspended, particulate state. Both the packed FI-EV-A71 final vaccine products and the FI-EV-A71 antigens adjuvant premix bulk could elicit strong neutralizing responses in mice.
After ten years of low temperature storage, the FI-EV-A71 vaccine still presents decent stability and good immunogenicity.
Separation and purification of highly infectious enterovirus A71 particles using a strong anion-exchange column
2022, Journal of Chromatography A
Virions produced from cell culture is the primary source for production of formalin-inactivated whole virus vaccines for enteroviruses. EV-A71 particles produced from culture system comprise two major types, the immature/empty (E)-particle and the mature/full (F)-particle, which both exhibit low isoelectric point (pI) values but have distinct differences in infectivity and immunogenicity. Although EV-A71 particles can conventionally be separated into E-particle and F-particle using sucrose gradient ultracentrifugation, this procedure is cumbersome and difficult to put into practice for vaccine production. Methods based on ion-exchange chromatography have been exploited to improve the purification efficacy; however, none of them are capable of separating the E- and F-particles efficiently. In this study, we aimed to develop an approach to isolate and purify the highly immunogenic mature EV-A71 particles. By applying a step gradient elution procedure, we successfully isolated the viral structure protein VP0-cleaved particles of EV-A71 from a mixture of cultured viral solution using the Q-membrane anion-exchange chromatography. The elution started with 0.1x phosphate buffered saline (PBS) solution while increasing the percentage of 1x PBS containing 1M NaCl in sequential steps. By this procedure, the VP0-cleaved mature particles and VP0-uncleaved immature particles of EV-A71 could be separated into different fractions in Q-membrane with gradually increased NaCl concentration in elution buffer. The purified VP0-cleaved particles were shown to have characteristics equivalent to those of the highly infectious F-particles of EV-A71. The overall recovery rate for the mature EV-A71 particles by Q-membrane is 56% and its purity was shown to be equivalent to those isolated by the sucrose gradient ultracentrifugation. Our approach provides a simple and efficient purification method for recovering mature, highly infectious virus particles from the EV-A71 culture bulk.
Treponema primitia α1–2-fucosyltransferase-catalyzed one-pot multienzyme synthesis of fucosylated oligosaccharide lacto-N-fucopentaose I with antiviral activity against enterovirus 71
2022, Food Chemistry: X
Fucosylated oligosaccharides have important biological functions as well as an excellent antiviral activity. A novel α 1–2-fucosyltransferase (α 2FT) from Treponema primitia (Tp2FT) was cloned and expressed in Escherichia coli BL21(DE3) and purified as an N-His₆-tagged fusion protein (His₆-Tp2FT). Mass spectrometry was carried out to identify the products of enzymatic reaction. The Tp2FT exhibited strict acceptor substrate specificity for type 1 structure (Galβ1-3GlcNAc)-containing glycans. It might be a promising emzyme for the chemo-enzymatic synthesis of lacto-N-fucopentaose I (LNFP I), which is one of the important fucosylated oligosaccharides. In this study, different in vitro experiments were used to study the biological activities of LNFP I. It could reduce the concentrations of inflammatory cytokines and effectively inhibit the synthesis of enterovirus 71 proliferation. LNFP I was an inhibitor of enterovirus 71 in the early stages of infection, it can used in infant nutrition and might provide a new drug for hand foot mouth disease.
Chimeric enterovirus 71 virus-like particle displaying conserved coxsackievirus A16 epitopes elicits potent immune responses and protects mice against lethal EV71 and CA16 infection
2021, Vaccine
Hand-foot-and-mouth disease (HFMD) is an infectious disease of infants and young children frequently caused by the enterovirus A species, mainly enterovirus 71 (EV71) and coxsackievirus A16 (CA16). In this study, we prepared the EV71 virus-like particle (EV71-VLP) and its chimeras using recombinant baculovirus (Bac-P1-3CD) co-expressing EV71 P1 (under polyhedrin promoter) and 3CD (under CMV-IE promoter) proteins in Sf9 cells. EV71-VLP chimera ChiEV71(1E)-VLP or ChiEV71(4E)-VLP displayed single CA16 PEP71 epitope in VP1 or four conserved CA16 neutralizing epitopes (PEP71 in VP1, aa136-150 in VP2, aa176-190 in VP3 and aa48-62 in VP4) by substitution of the corresponding regions of EV71 structure proteins, respectively. In mice, EV71-VLP and its chimeras elicited similar EV71-specific IgG and neutralizing antibody (NAb) titers compared to inactivated EV71. Expectedly, vaccination of ChiEV71(1E)-VLP or ChiEV71(4E)-VLP resulted in significantly increased CA16-specific IgG and NAb production and improved cross-protection against CA16 infection compared to EV71-VLP. Interestingly, the VLPs induced potent cellular immune responses and significantly decreased Th2 type (IL-4 and IL-10) cytokines secretion in the splenocytes of immunized mice compared to inactivated EV71 or inactivated CA16. Neonatal mice born to dams immunized with the chimeric VLPs or neonatal mice passively transferred with sera of immunized mice were completely protected from lethal EV71 challenge and partially protected from lethal CA16 infection. Our study provides a novel bivalent or multivalent vaccine strategy to prevent EV71 and related-enterovirus infections.
Emergence of a non vaccine-cognate enterovirus A71 genotype C1 in mainland China
2021, Journal of Infection
Citation Excerpt :
EV-A71 was first isolated in 1969 from the cerebrospinal fluid of a patient with encephalitis in California, USA. Since then, numerous outbreaks have occurred worldwide and multiple subgenotypes have been detected.6 In mainland China, EV-A71 C4 was the single predominant subgenotype since 20081, and thus the current licensed in-activated EV-A71 vaccines are all C4-based.
EV-A71 is a common causative agent of hand foot and mouth disease. In mainland China, EV-A71 subgenotype C4 has been the sole circulating genotype since 2008, and was used in the production of multiple licensed vaccines. Here, we report the first detection EV-A71 C1 strains in China.
Full genomic sequence were obtained. The origin of the EV-A71 C1 strains were tracked down by Bayesian inferences. Recombination was analyzed using Simplot program. And the antigenicity were tested using the microneutralization test.
The C1-GD2019 shared high identity with the C1-like lineage recently identified in Europe and was introduced into Guangdong in 2018–2019. Close genetic relatedness between the C1-GD2019 and Europe C1-like strains were observed except for the 3D-3′UTR region. The late showed high similarity with CVA genomes. Antigenic variance was found. The C1-GD2019 could not be effectively neutralized by EV-A71 C4a neutralizing antibody positive samples.
This is the first report of EV-A71 subgenotype C1 isolated in China. It is a recombinant strain originating from C1-like strains recently identified in Europe and CVA strains. The different antigenicity between the C1 strains and C4a vaccine strains highlighted the importance on closely monitoring the EV-A71 C1 strains in China.

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Recent advances in the molecular epidemiology and control of human enterovirus 71 infection

Highlights

Introduction

Section snippets

HEV71 genome structure

Molecular epidemiology of HEV71

Animal models of HEV71 infection and disease

HEV71 vaccine research and development

Conclusion

References and recommended reading

FEMS Microbiol Rev

Lancet Infect Dis

Microbes Infect

J Virol

J Virol

Arch Virol

Virology

J Gen Virol

J Virol

Nat Med

Vaccine

Vaccine

Virology

Cell Host Microbe

Proc Natl Acad Sci USA

PLoS ONE

Far upstream element binding protein 2 interacts with enterovirus 71 internal ribosomal entry site and negatively regulates viral translation

Nucl Acids Res

Enterovirus 71 contains a type I IRES element that functions when eukaryotic initiation factor eIF4G is cleaved

Virology

An apparently new enterovirus isolated from patients with disease of the central nervous system

J Infect Dis

Molecular epidemiology of human enterovirus 71 strains and recent outbreaks in the Asia-Pacific region: comparative analysis of the VP1 and VP4 genes

Emerg Infect Dis

Molecular epidemiology and evolution of enterovirus 71 strains isolated from 1970 to 1998

J Virol

Enterovirus 71 isolated from a case of acute flaccid paralysis in India represents a new genotype

Curr Sci

Genetic analysis of the VP1 region of enterovirus 71 reveals the emergence of genotype A in central China in 2008

Virus Genes

Reemergence of enterovirus 71 in 2008 in Taiwan: dynamics of genetic and antigenic evolution from 1998 to 2008

J Clin Microbiol

Epidemiology of enterovirus 71 in The Netherlands, 1963 to 2008

J Clin Microbiol

Enterovirus 71 outbreak, Brunei

Emerg Infect Dis

Molecular epidemiology of human enterovirus 71 in the United Kingdom from 1998 to 2006

J Clin Microbiol

Genetic evolution of enterovirus 71: epidemiological and pathological implications

Rev Med Virol

Genetic changes of Coxsackievirus A16 and Enterovirus 71 isolated from hand, foot, and mouth disease patients in Toyama, Japan between 1981 and 2007

Jpn J Infect Dis

Seroprevalence and molecular epidemiology of enterovirus 71 in Germany

Arch Virol

Phylogenetic evidence for a recent spread of two populations of human enterovirus 71 in European countries

J Gen Virol

Epidemiology of human enterovirus 71 infections in France, 2000–2009

J Clin Virol