Appearance of mosaic enterovirus 71 in the 2008 outbreak of China

Murine models of neonatal susceptibility to a clinical strain of enterovirus A71

Enterovirus A71 (EV-A71) is neurotropic and one of the primary enteric pathogens responsible for severe central nervous system infection in infants and young children. Neonatal mice are ideal models for studying the pathogenesis of infection caused by EV-A71. In this study, we assessed the susceptibility of neonatal BALB/c, C57BL/6, ICR, Kunming, and NIH mice to a clinically isolated EV-A71 strain. One-day-old mice were challenged with a clinical isolate of EV-A71 via intraperitoneal injection, then observed for 13 days for mortality, body-weight changes, and limb paralysis. RT-qPCR was performed to quantify viral RNA in the brain, spinal cord, skeletal muscle, and lungs of BALB/c and C57BL/6 mice. The expression of murine scavenger receptor class B member 2 (mSCARB2) was measured by western blotting. Finally, lesions were assessed by histological examination. We found that neonatal BALB/c and C57BL/6 mice were both susceptible to EV-A71, leading to decreased survival rate, greater body weight loss, and prominent hind-limb paralysis. Tissue viral loads of C57BL/6J mice were markedly higher than those of BALB/c mice, indicating that EV-A71 replicated more efficiently in C57BL/6 mice. Increased expression of mSCARB2 was observed 5 days after infection in C57BL/6 mice, which coincided with the peak in EV-A71 replication. Histological examination indicated that infection caused obvious pathogenic lesions. In conclusion, C57BL/6 are most susceptible to infection caused by EV-A71 and can be used as a model for studying its pathogenesis and test therapeutic options.

Global spatiotemporal transmission patterns of human enterovirus 71 from 1963 to 2019

Enterovirus 71 (EV71) can cause large outbreaks of hand, foot, and mouth disease (HFMD) and severe neurological diseases, which is regarded as a major threat to public health, especially in Asia-Pacific regions. However, the global spatiotemporal spread of this virus has not been identified. In this study, we used large sequence datasets and a Bayesian phylogenetic approach to compare the molecular epidemiology and geographical spread patterns of different EV71 subgroups globally. The study found that subgroups of HFMD presented global spatiotemporal variation, subgroups B0, B1, and B2 have caused early infections in Europe and America, and then subgroups C1, C2, C3, and C4 replaced B0-B2 as the predominant genotypes, especially in Asia-Pacific countries. The dispersal patterns of genotype B and subgroup C4 showed the complicated routes in Asia and the source might in some Asian countries, while subgroups C1 and C2 displayed more strongly supported pathways globally, especially in Europe. This study found the predominant subgroup of EV71 and its global spatiotemporal transmission patterns, which may be beneficial to reveal the long-term global spatiotemporal transmission patterns of human EV71 and carry out the HFMD vaccine development.

Risk factors for death from hand-foot-mouth disease: a meta-analysis

In recent years, outbreaks of hand–foot–mouth disease (HFMD) in China, Singapore and other Western Pacific Region, involving millions of children, have become a big threat to public health. This study aimed to quantitatively assess all qualified studies and identify the risk factors for HFMD death. A systematic search of the databases PubMed, Medline, Embase and the Cochrane Library was performed. Study heterogeneity and publication bias were estimated. Seven case–control studies involving 1641 participants (634 died and 1007 survived) were included in the meta-analysis. Human enterovirus 71 infection, male, age ⩽3 years, vomiting, cyanosis, convulsion, duration of fever ⩾3 days, atypical rashes and abdominal distention were not significantly related to HFMD death (P ⩽ 0.05). Lethargy (odds ratio (OR) = 6.62; 95% CI 3.61–12.14; I² = 0%; P < 0.0001), pneumonoedema/pneumorrhagia (OR = 4.09; 95% CI 2.44–6.87; I² = 0%; P < 0.0001), seizures (OR = 6.85; 95% CI 2.37–19.74; I² = 0%; P = 0.0004), dyspnoea (OR = 8.24; 95% CI 2.05–33.19; I² = 83%; P = 0.003) and coma (OR = 3.76; 95% CI 1.85–7.67; I² = 0%; P = 0.0003) were significantly associated with HFMD death, which were risk factors for HFMD death.

Impact of Ambient Temperature and Relative Humidity on the Incidence of Hand-Foot-Mouth Disease in Wuhan, China

Background: Few studies have previously explored the relationship between hand, foot, and mouth disease (HFMD) and meteorological factors with the effect modification of air pollution, and these studies had inconsistent findings. We therefore applied a time-series analysis assessing the effects of temperature and humidity on the incidence of HFMD in Wuhan, China to deepen our understanding of the relationship between meteorological factors and the risk of HFMD. Methods: Daily HFMD cases were retrieved from Hubei Provincial Center for Disease Control and Prevention from 1 February 2013 to 31 January 2017. Daily meteorological data including 24 h average temperature, relative humidity, wind velocity, and atmospheric pressure were obtained from Hubei Meteorological Bureau. Data on Air pollution was collected from 10 national air-monitoring stations in Wuhan city. We adopted a distributed lag non-linear model (DLNM) combined with Poisson regression and time-series analysis to estimate the effects of temperature and relative humidity on the incidence HFMD. Results: We found that the association between temperature and HFMD incidence was non-linear, exhibiting an approximate "M" shape with two peaks occurring at 2.3 °C (RR = 1.760, 95% CI: 1.218-2.542) and 27.9 °C (RR = 1.945, 95% CI: 1.570-2.408), respectively. We observed an inverted "V" shape between relative humidity and HFMD. The risk of HFMD reached a maximum value at a relative humidity of 89.2% (RR = 1.553, 95% CI: 1.322-1.824). The largest delayed cumulative effects occurred at lag 6 for temperature and lag 13 for relative humidity. Conclusions: The non-linear relationship between meteorological factors and the incidence of HFMD on different lag days could be used in the early targeted warning system of infectious diseases, reducing the possible outbreaks and burdens of HFMD among sensitive populations.

Impact of Ambient Temperature and Relative Humidity on the Incidence of Hand-Foot-Mouth Disease in Wuhan, China

Background: Few studies have previously explored the relationship between hand, foot, and mouth disease (HFMD) and meteorological factors with the effect modification of air pollution, and these studies had inconsistent findings. We therefore applied a time-series analysis assessing the effects of temperature and humidity on the incidence of HFMD in Wuhan, China to deepen our understanding of the relationship between meteorological factors and the risk of HFMD. Methods: Daily HFMD cases were retrieved from Hubei Provincial Center for Disease Control and Prevention from 1 February 2013 to 31 January 2017. Daily meteorological data including 24 h average temperature, relative humidity, wind velocity, and atmospheric pressure were obtained from Hubei Meteorological Bureau. Data on Air pollution was collected from 10 national air-monitoring stations in Wuhan city. We adopted a distributed lag non-linear model (DLNM) combined with Poisson regression and time-series analysis to estimate the effects of temperature and relative humidity on the incidence HFMD. Results: We found that the association between temperature and HFMD incidence was non-linear, exhibiting an approximate "M" shape with two peaks occurring at 2.3 °C (RR = 1.760, 95% CI: 1.218-2.542) and 27.9 °C (RR = 1.945, 95% CI: 1.570-2.408), respectively. We observed an inverted "V" shape between relative humidity and HFMD. The risk of HFMD reached a maximum value at a relative humidity of 89.2% (RR = 1.553, 95% CI: 1.322-1.824). The largest delayed cumulative effects occurred at lag 6 for temperature and lag 13 for relative humidity. Conclusions: The non-linear relationship between meteorological factors and the incidence of HFMD on different lag days could be used in the early targeted warning system of infectious diseases, reducing the possible outbreaks and burdens of HFMD among sensitive populations.

Enterovirus A71 Infection Activates Human Immune Responses and Induces Pathological Changes in Humanized Mice

Since the discovery of enterovirus A71 (EV-A71) half a century ago, it has been recognized as the cause of large-scale outbreaks of hand-foot-and-mouth disease worldwide, particularly in the Asia-Pacific region, causing great concern for public health and economic burdens. Detailed mechanisms on the modulation of immune responses after EV-A71 infection have not been fully known, and the lack of appropriate models hinders the development of promising vaccines and drugs. In the present study, NOD-scid IL2Rγ^-/- (NSG) mice with a human immune system (humanized mice) at the age of 4 weeks were found to be susceptible to a human isolate of EV-A71 infection. After infection, humanized mice displayed limb weakness, which is similar to the clinical features found in some of the EV-A71-infected patients. Histopathological examination indicated the presence of vacuolation, gliosis, or meningomyelitis in brain stem and spinal cord, which were accompanied by high viral loads detected in these organs. The numbers of activated human CD4⁺ and CD8⁺ T cells were upregulated after EV-A71 infection, and EV-A71-specific human T cell responses were found. Furthermore, the secretion of several proinflammatory cytokines, such as human gamma interferon (IFN-γ), interleukin-8 (IL-8), and IL-17A, was elevated in the EV-A71-infected humanized mice. Taken together, our results suggested that the humanized mouse model permits insights into the human immune responses and the pathogenesis of EV-A71 infection, which may provide a platform for the evaluation of anti-EV-A71 drug candidates in the future.IMPORTANCE Despite causing self-limited hand-food-and-mouth disease in younger children, EV-A71 is consistently associated with severe forms of neurological complications and pulmonary edema. Nevertheless, only limited vaccines and drugs have been developed over the years, which is possibly due to a lack of models that can more accurately recapitulate human specificity, since human is the only natural host for wild-type EV-A71 infection. Our humanized mouse model not only mimics histological symptoms in patients but also allows us to investigate the function of the human immune system during infection. It was found that human T cell responses were activated, accompanied by an increase in the production of proinflammatory cytokines in EV-A71-infected humanized mice, which might contribute to the exacerbation of disease pathogenesis. Collectively, this model allows us to delineate the modulation of human immune responses during EV-A71 infection and may provide a platform to evaluate anti-EV-A71 drug candidates in the future.

Complete genome analysis demonstrates multiple introductions of enterovirus 71 and coxsackievirus A16 recombinant strains into Thailand during the past decade

Hand, foot, and mouth disease (HFMD) caused by enteroviruses remains a public health threat, particularly in the Asia-Pacific region during the past two decades. Moreover, the introduction of multiple subgenotypes and the emergence of recombinant viruses is of epidemiological importance. Based on either the full genome or VP1 sequences, 32 enteroviruses (30 from HFMD patients, 1 from an encephalitic patient, and 1 from an asymptomatic contact case) isolated in Thailand between 2006 and 2014 were identified as 25 enterovirus 71 (EV71) isolates (comprising 20 B5, 1 C2, 2 C4a, and 2 C4b subgenotypes) and 7 coxsackievirus A16 (CA16) isolates (comprising 6 B1a and 1 B1b subgenotypes). The EV71 subgenotype C4b was introduced into Thailand for the first time in 2006 and was replaced by subgenotype C4a strains in 2009. Phylogenetic, similarity plot and bootscan analyses of the complete viral genomes identified 12 recombinant viruses among the 32 viral isolates. Only one EV71-B5 isolate out of 20 was a recombinant virus with one region of intratypic or intertypic recombination, while all four EV71-C4 isolates were recombinant viruses having undergone double recombination, and all seven CA16 isolates were recombinant viruses. The recombination breakpoints of these recombinants are located solely within the P2 and P3 regions. Surveillance for circulating strains and subgenotype replacement are important with respect to molecular epidemiology and the selection of the upcoming EV71 vaccine. In addition, the clinical importance of recombinant viruses needs to be further explored.

Development of a high-growth enterovirus 71 vaccine candidate inducing cross-reactive neutralizing antibody responses

Although Enterovirus 71 (EV71) has only one serotype based on serum neutralization tests using hyperimmune animal antisera, three major genogroups (A, B and C) including eleven genotypes (A, B1-B2, and C1-C5) can be well classified based on phylogenetic analysis. Since 1997, large-scale EV71 epidemics occurred cyclically with different genotypes in the Asia-Pacific region. Therefore, development of EV71 vaccines is a national priority in several Asian countries. Currently, five vaccine candidates have been evaluated in clinical trials in China (three C4 candidates), Singapore (one B2 candidate), and Taiwan (one B4 candidate). Overall, the peak viral titers of these 5 vaccine candidates could only reach about 10⁷ TCID₅₀/mL. Moreover, genotypes of these 5 candidates are different from the current predominant genotype B5 in Taiwan and South-Eastern Asia. We adapted a high-growth EV71 genotype B5 (HG-B5) virus after multiple passages and plaque selections in Vero cells and the HG-B5 virus could reach high titers (>10⁸ TCID₅₀/mL) in a microcarrier-based cell culture system. The viral particles were further purified and formulated with alum adjuvant. After two doses of intramuscular immunization in rabbits, the HG-B5 vaccine candidate could induce cross-reactive neutralizing antibodies against the three major EV71 genogroups. In conclusion, a high-growth EV71 virus was successfully adapted in Vero cells and could induce broad spectrum neutralizing antibody titers against three (A, B5, and C4) genotypes in rabbits.

Inhibition of enterovirus 71 replication and viral 3C protease by quercetin

BACKGROUND

Enterovirus 71 (EV71) is one of the major causative agents of hand, foot, and mouth disease (HFMD), which is sometimes associated with severe central nervous system disease in children. There is currently no specific medication for EV71 infection. Quercetin, one of the most widely distributed flavonoids in plants, has been demonstrated to inhibit various viral infections. However, investigation of the anti-EV71 mechanism has not been reported to date.

METHODS

The anti-EV71 activity of quercetin was evaluated by phenotype screening, determining the cytopathic effect (CPE) and EV71-induced cells apoptosis. The effects on EV71 replication were evaluated further by determining virus yield, viral RNA synthesis and protein expression, respectively. The mechanism of action against EV71 was determined from the effective stage and time-of-addition assays. The possible inhibitory functions of quercetin via viral 2Apro, 3Cpro or 3Dpol were tested. The interaction between EV71 3Cpro and quercetin was predicted and calculated by molecular docking.

RESULTS

Quercetin inhibited EV71-mediated cytopathogenic effects, reduced EV71 progeny yields, and prevented EV71-induced apoptosis with low cytotoxicity. Investigation of the underlying mechanism of action revealed that quercetin exhibited a preventive effect against EV71 infection and inhibited viral adsorption. Moreover, quercetin mediated its powerful therapeutic effects primarily by blocking the early post-attachment stage of viral infection. Further experiments demonstrated that quercetin potently inhibited the activity of the EV71 protease, 3Cpro, blocking viral replication, but not the activity of the protease, 2Apro, or the RNA polymerase, 3Dpol. Modeling of the molecular binding of the 3Cpro-quercetin complex revealed that quercetin was predicted to insert into the substrate-binding pocket of EV71 3Cpro, blocking substrate recognition and thereby inhibiting EV71 3Cpro activity.

CONCLUSIONS

Quercetin can effectively prevent EV71-induced cell injury with low toxicity to host cells. Quercetin may act in more than one way to deter viral infection, exhibiting some preventive and a powerful therapeutic effect against EV71. Further, quercetin potently inhibits EV71 3Cpro activity, thereby blocking EV71 replication.

Oligoadenylate synthetase 3 S381R gene polymorphism is associated with severity of EV71 infection in Chinese children

BACKGROUND

Oligoadenylate synthetase 3 (OAS3) is interferon-induced antiviral enzyme, playing a significant role in the innate immune response. Genetic polymorphism in OAS3 gene has been reported to be a susceptibility factor in many infected diseases, but evidence of its effect on enterovirus 71 (EV71) infection is still lacking.

OBJECTIVES

An attempt study was made to investigate whether genetic polymorphism of OAS3 S381R is associated with the severity of EV71 infection in Chinese children.

STUDY DESIGN

Retrospectively sumed up the clinical onsets and experimental results for 249 cases with EV71 infection (including 151 mild cases and 98 severe cases) and 243 controls. An improved multiplex ligation detection reaction (iMLDR) technique was carried out to analyze polymorphism in OAS3 S381R G/C gene for genetic association analyses. The plasma levels of IFN-γ were determined by enzyme-linked immunosorbent assays.

RESULTS

The distribution of OAS3 S381R CC genotype (73.47%) and C allele (85.20%) in severe cases was markedly higher than in mild cases (45.70%, P < .01; 67.88%, P < .01). The blood IFN-γ levels of severe cases were significantly lower in CC genotype (131.66 ± 10.84 pg/mL) compared to GG (183.37 ± 24.50 pg/mL, p < .01) and GC genotype (168.48 ± 26.57 pg/mL, p < .01).

CONCLUSIONS

Carrying the C allele of the OAS3 S381R gene could be a susceptibility factor in the development of severe EV71 infection in Chinese children.

Antiviral activity of a polysaccharide from Laminaria japonica against enterovirus 71

This in vitro study investigated the antiviral activity of an acidic polysaccharide from Laminaria japonica against enterovirus 71 (EV71) as well as its mechanism of action. The LJ04 polysaccharide was purified from Laminaria japonica by affinity chromatography. To investigate its antiviral activity, an MTT assay, q-PCR, immunofluorescent staining and western-blot analysis were performed. To define its mechanism of action, ELISA, q-PCR and flow cytometry were conducted. LJ04 had a low EC50, high CC50 and high SI. LJ04 inhibited not only JN200804, but also JN200803 in RD cells, and viral proliferation was strongly inhibited, whereas LJ04 suppressed viral-induced apoptosis as detected by flow cytometry. In conclusion, LJ04 was found to have robust antiviral activity by inhibiting apoptosis and inducing IFN-β expression. Our findings indicate that LJ04 is a good candidate for the treatment of EV71.

Asymmetric synthesis of novel triazole derivatives and their in vitro antiviral activity and mechanism of action

In this study, forty-four chiral triazole derivatives have been prepared via asymmetric synthesis, and which has been successfully characterized by typical spectroscopic techniques including ¹H NMR, ¹³C NMR, EI-MS, elemental analysis and optical rotations. Their in vitro antiviral activities against EV71 and CVB3 were fully investigated in cell-based assays. It was observed that 13 synthetic triazole derivatives inhibited the CPE of EV71 on RD cells, with EC_50S in the 5.3-15.9 μg/ml range and corresponding SIs of 4.0-27.6, while 17 triazole derivatives showed antiviral activities against CVB3, with EC_50S in the 4.7-15.1 μg/ml range and the corresponding SIs of 3.7-14.5. In addition, in some cases, the respective enantiomers showed significantly selective inhibitory effect against EV71, most notably for the enantiomers 9(R) and 10(S), 42(R) and 43(S), which presented an obvious activity difference. The most potential molecules are the compounds 10 and 43 with S-configuration, and which exhibit good SI values compared with the control Ribavirin.

Association of the OAS3 rs1859330 G/A genetic polymorphism with severity of enterovirus-71 infection in Chinese Han children

The 2'5'-oligoadenylate synthetase (OAS) is an interferon (IFN)-induced protein that plays an important role in the antiviral action of IFN, with OAS3 being one of the four OAS classes (OAS1, OAS2, OAS3, OASL). The effect of OAS on several infectious viral diseases has been reported; however, a study of the effect of OAS3 on enterovirus 71 (EV71) is lacking. The purpose of this study was to evaluate the association of the OAS3 rs1859330 G/A genetic polymorphism with susceptibility and severity of EV71 infection. We investigated 370 Chinese Han children with hand-foot-mouth disease (HFMD) (214 of which were mild cases while 156 were severe). An improved multiplex ligation detection reaction (iMLDR) technique was carried out to examine the genotype. The AA genotype distribution (p = 0.002) and A allele frequency (OR = 1.83, 95% CI 1.32-2.52, p < 0.001) of OAS3 rs1859330 in severe cases were significantly higher than in mild cases. When comparing the different genotypes in EV71-infected patients, there were statistical differences in relation to rash (p = 0.03), oral ulcers (p = 0.005), pathologic reflex (p = 0.003), WBC counts (p = 0.032), CRP (p = 0.024), BG concentrations (p = 0.029), ALT (p = 0.02), and EEG (p = 0.019). However, there were no differences in relation to age, gender, AST, CK-MB, CT/ MRI, as well as some symptoms and signs (e.g. duration of fever (days), headache, convulsions, consciousness disturbance, paralysis, sign of meningeal irritation). In the cerebrospinal fluid (CSF) of severe cases, there were no differences in the levels of white cells, protein, glucose, chloride, lymphocytes and monocytes between the different genotypes. The plasma levels of IFN-γ in EV71-infected patients were significantly higher than in the control group (p < 0.01). IFN-γ concentrations in severe cases were lower in A allele carriers (AA+GA) (118.5 ± 12.6pg/mL) than in GG homozygotes (152.6 ± 56.3pg/mL p < 0.05). These findings suggest that the OAS3 rs1859330 G/A genetic polymorphism is associated with the severity of EV-71 infection, and that the A allele is a risk factor for the development of severe EV71 infection.

Circulating microRNAs as Potential Biomarkers of Infectious Disease

microRNAs (miRNAs) are a class of small non-coding endogenous RNA molecules that regulate a wide range of biological processes by post-transcriptionally regulating gene expression. Thousands of these molecules have been discovered to date, and multiple miRNAs have been shown to coordinately fine-tune cellular processes key to organismal development, homeostasis, neurobiology, immunobiology, and control of infection. The fundamental regulatory role of miRNAs in a variety of biological processes suggests that differential expression of these transcripts may be exploited as a novel source of molecular biomarkers for many different disease pathologies or abnormalities. This has been emphasized by the recent discovery of remarkably stable miRNAs in mammalian biofluids, which may originate from intracellular processes elsewhere in the body. The potential of circulating miRNAs as biomarkers of disease has mainly been demonstrated for various types of cancer. More recently, however, attention has focused on the use of circulating miRNAs as diagnostic/prognostic biomarkers of infectious disease; for example, human tuberculosis caused by infection with Mycobacterium tuberculosis, sepsis caused by multiple infectious agents, and viral hepatitis. Here, we review these developments and discuss prospects and challenges for translating circulating miRNA into novel diagnostics for infectious disease.

The Epidemiology of Hand, Foot and Mouth Disease in Asia: A Systematic Review and Analysis

CONTEXT

Hand, foot and mouth disease (HFMD) is a widespread pediatric disease caused primarily by human enterovirus 71 (EV-A71) and Coxsackievirus A16 (CV-A16).

OBJECTIVE

This study reports a systematic review of the epidemiology of HFMD in Asia.

DATA SOURCES

PubMed, Web of Science and Google Scholar were searched up to December 2014.

STUDY SELECTION

Two reviewers independently assessed studies for epidemiologic and serologic information about prevalence and incidence of HFMD against predetermined inclusion/exclusion criteria.

DATA EXTRACTION

Two reviewers extracted answers for 8 specific research questions on HFMD epidemiology. The results are checked by 3 others.

RESULTS

HFMD is found to be seasonal in temperate Asia with a summer peak and in subtropical Asia with spring and fall peaks, but not in tropical Asia; evidence of a climatic role was identified for temperate Japan. Risk factors for HFMD include hygiene, age, gender and social contacts, but most studies were underpowered to adjust rigorously for confounding variables. Both community-level and school-level transmission have been implicated, but their relative importance for HFMD is inconclusive. Epidemiologic indices are poorly understood: No supporting quantitative evidence was found for the incubation period of EV-A71; the symptomatic rate of EV-A71/Coxsackievirus A16 infection was from 10% to 71% in 4 studies; while the basic reproduction number was between 1.1 and 5.5 in 3 studies. The uncertainty in these estimates inhibits their use for further analysis.

LIMITATIONS

Diversity of study designs complicates attempts to identify features of HFMD epidemiology.

CONCLUSIONS

Knowledge on HFMD remains insufficient to guide interventions such as the incorporation of an EV-A71 vaccine in pediatric vaccination schedules. Research is urgently needed to fill these gaps.

Amphotericin B Inhibits Enterovirus 71 Replication by Impeding Viral Entry

Enterovirus 71 (EV71) infection causes hand-foot-and-mouth disease that leads to cardiopulmonary complications and death in young children. There is thus an urgent need to find new treatments to control EV71 infection. In this study, we report potent inhibition of EV71 by a polyene antibiotic Amphotericin B. Amphotericin B profoundly diminished the expression of EV71 RNA and viral proteins in the RD cells and the HEK293 cells. As a result, EV71 production was inhibited by Amphotericin B with an EC50 (50% effective concentration) of 1.75 μM in RD cells and 0.32 μM in 293 cells. In addition to EV71, EV68 was also strongly inhibited by Amphotericin B. Results of mechanistic studies revealed that Amphotericin B targeted the early stage of EV71 infection through impairing the attachment and internalization of EV71 by host cells. As an effective anti-fungi drug, Amphotericin B thus holds the promise of formulating a novel therapeutic to treat EV71 infection.

Efficacy and safety of interferon-α2b spray in the treatment of hand, foot, and mouth disease: a multicenter, randomized, double-blind trial

Hand, foot, and mouth disease (HFMD) is a common infectious enterovirus disease, occurring mostly in infants and children younger than 7 years with potentially fatal complications. Therefore, we evaluated the clinical efficacy and safety of recombinant human interferon (IFN)-α2b spray for treating mild HFMD in 400 patients in a randomized, open, controlled clinical trial. The patients were randomized to the IFN-α2b spray and placebo groups, and their temperature, skin rash, oral lesions, and appetite were monitored, while pathogen levels and safety were evaluated with a 7-day follow-up. The mean age of the patients was 20.1 ± 10.2 months. The median duration of fever, oral ulcers or vesicles (or both), and skin rash in addition to median time to regain appetite in the IFN-α2b spray group were shorter than they were in the placebo group. The number of virus-positive cases differed statistically between the two groups for the three follow-up detections. Additionally, the incidences of adverse events (AEs) and severe AEs (SAEs) were not significantly different between the two groups, and the SAEs were evidently unrelated to the IFN-α2b spray or placebo. Therefore, the IFN-α2b spray is suitable for topical treatment of HFMD, and it rapidly relieved fever, promoted oral lesions and subsidence of rash, enhanced appetite, promoted disease recovery, and was safe for application.

Characterization of VP1 sequence of Coxsackievirus A16 isolates by Bayesian evolutionary method

BACKGROUND

Coxsackievirus A16 (CV-A16), a major etiopathologic cause of pediatric hand, foot, and mouth disease (HFMD) worldwide, has been reported to have caused several fatalities. Revealing the evolutionary and epidemiologic dynamics of CV-A16 across time and space is central to understanding its outbreak potential.

METHODS

In this study, we isolated six CV-A16 strains in China's Jilin province and construct a maximum clade credibility (MCC) tree for CV-A16 VP1 gene by the Bayesian Markov Chain Monte Carlo method using 708 strains from GenBank with epidemiological information. The evolution characteristics of CV-A16 VP1 gene was also analysed dynamicly through Bayesian skyline plot.

RESULTS

All CV-A16 strains identified could be classified into five major genogroups, denoted by GI-GV. GIV and GV have co-circulated in China since 2007, and the CV-A16 epidemic strain isolated in the Jilin province, China, can be classified as GIV-3. The CV-A16 genogroups circulating recently in China have the same ancestor since 2007. The genetic diversity of the CV-A16 VP1 gene shows a continuous increase since the mid-1990s, with sharp increases in genetic diversity in 1997 and 2007 and reached peak in 2007. Very low genetic diversity existed after 2010. The CV-A16 VP1 gene evolutionary rate was 6.656E-3 substitutions per site per year.

CONCLUSIONS

We predicted the dynamic phylogenetic trends, which indicate outbreak trends of CV-A16, and provide theoretical foundations for clinical prevention and treatment of HFMD which caused by a CV-A16.

Determinants of EV71 immunogenicity and protection against lethal challenge in a mouse model

Circulating enterovirus 71 (EV71)-associated hand, foot, and mouth disease (HFMD) is a major public health problem in the Asian-Pacific region. An EV71 vaccine for HFMD prevention is currently being developed. However, viral determinants that could influence the vaccine's efficacy have not been well characterized. In this study, we isolated and characterized several EV71 strains that are currently circulating in northern and southern China. We determined that VP1 variation is a major determinant of EV71 immunogenicity. A single amino acid variation in VP1 can lead to significant differences in the breadth and potency of immune responses against primary EV71 isolates as well as the sensitivity of EV71 to heterologous neutralizing antibody responses. We also identified EV71 strains that could induce potent immunogenic and cross-neutralizing antibody responses against diverse EV71 strains. Furthermore, these neutralizing antibodies could protect neonatal mice from lethal dose challenge with various circulating EV71 viruses. Our study provides useful information for EV71 vaccine development and evaluation.

Carnitine palmitoyl transferase 2 polymorphism may be associated with enterovirus 71 severe infection in a Chinese population

Genetic polymorphism in the carnitine palmitoyl transferase 2 (CPT2) gene has been reported to be a susceptibility factor in a number of syndromes of acute encephalopathy with various infectious diseases, but evidence of its effect on enterovirus 71 (EV71) infection is lacking. The goal of this study was to examine the relationship between genetic polymorphism of CPT2 and severity of EV71 infection in a Chinese population. PCR of five exons of the CPT2 gene was carried out to identify single-nucleotide polymorphisms (SNPs) in EV71-infected subjects (n = 333), including mild cases (n = 271) and severe cases (n = 62) as well as healthy controls (n = 328). Blood ATP levels were measured within 24 h of admission. The frequency of the A allele of rs1799821 (P = 0.023) and the G allele of rs2229291 (P = 0.009) in the CPT2 gene was higher in patients with severe EV71 infection. The A-G haplotype of rs1799821and rs2229291 was directly linked to EV71 severe infection risk when compared to all other haplotypes (OR = 2.005, 95 % CI = 1.087-3.700, P = 0.024). The blood ATP levels of severe cases were significantly lower than in mild cases (P < 0.01) and controls (P < 0.01). A significant negative correlation was observed in haplotype A-G between ATP levels and physical findings in severe cases (P < 0.05). These findings suggest that CPT2 polymorphism may be associated with severity of EV71 infection and that the A-G haplotype of the CPT2 gene is involved in the inflammatory process of EV71 infection.

Biological characteristics of different epidemic enterovirus 71 strains and their pathogeneses in neonatal mice and rhesus monkeys

Hand, foot and mouth disease (HFMD) has been prevalent in China since 2008. Enterovirus 71 (EV71) is a common causative agent of HFMD, and various strains of EV71 are prevalent worldwide. The EV71C4 subgenotype is the most endemic strain in China. However, few studies investigating the biological characteristics and pathogeneses of different C4 strains have been reported. Therefore, the current study investigated 19 clinical EV71 strains in neonatal ICR mice and neonatal rhesus monkeys by comparing pathogenicity; the virulence of different viral passages, dosages, and routes of infection; and the effects produced by subject animal age. These 19 clinical EV71 strains, which were of the same subtype, displayed varying pathogenic effects. Three strains (HE31, 231 and 262) induced limb paralysis in neonatal ICR mice. In addition, the degree of virulence was largely dependent upon the dose, route of infection, and number of passages of the challenge virus, as well as the ages of the infected animals. The present study provides valuable basic data to enable further research into EV71 pathogenesis and to facilitate the development of new drugs and vaccines.

Identification of N-Acetyldopamine Dimers from the Dung Beetle Catharsius molossus and Their COX-1 and COX-2 Inhibitory Activities

Recent studies focusing on identifying the biological agents of Catharsius molossus have led to the identification of three new N-acetyldopamine dimers molossusamide A–C (1−3) and two known compounds 4 and 5. The structures of the new compounds were identified by comprehensive spectroscopic evidences. Compound 4 was found to have inhibitory effects towards COX-1 and COX-2.

Broad protection with an inactivated vaccine against primary-isolated lethal enterovirus 71 infection in newborn mice

Background

Circulating enterovirus 71 (EV-A71)-associated hand, foot, and mouth disease is on the rise in the Asian-Pacific region. Although animal models have been developed using mouse-adapted EV-A71 strains, mouse models using primary EV-A71 isolates are scarce. Lethal animal models with circulating EV-A71 infection would contribute to studies of pathogenesis as well as vaccine development and evaluation.

Results

In this study, we established a lethal mouse model using primary EV-A71 isolates from patients infected with serotypes that are currently circulating in humans. We also characterized the dose-dependent virulence and pathologic changes of circulating EV-A71 in this mouse model. Most importantly, we have established this mouse model as a suitable system for EV-A71 vaccine evaluation. An inactivated EV-A71 vaccine candidate offered complete protection from death induced by various circulating EV-A71 viruses to neonatal mice that were born to immunized female mice. The sera of the immunized dams and their pups showed higher neutralization titers against multiple circulating EV-A71 viruses.

Conclusions

Thus, our newly established animal model using primary EV-A71 isolates is helpful for future studies on viral pathogenesis and vaccine and drug development.

Coxsackievirus A16 infection stimulates imbalances of T cells in children

Immune reaction plays a crucial role in the regulation of the progression of Coxsackievirus A16 (CA16)-infected hand, foot and mouth disease (HFMD). However, no details of T-cell subset frequency or imbalance during the CA16 infection process have been revealed. In the present study, whether CA16-induced HFMD changes the frequency of different T-cell subsets and associated immune mediators was determined in children. The results indicate that the percentages of Th1 and Tc1 cells were significantly increased in children with HFMD compared with those in healthy children. In addition, the Th1/Th2 ratio and interferon (IFN)-γ levels were significant higher in children with HFMD. Furthermore, the percentage of Th17 cells and the Th17/Treg ratio as well as interleukin (IL)-17A levels were higher in HFMD cases. In conclusion, the present study demonstrated the dysregulation of T-cell subsets following CA16 infection. The Th1/Th2 and Th17/Treg ratios were imbalanced following infection. Also, the imbalance Th1/Th2 and Th17/Treg ratios contributed to the increased levels of IFN-γ and IL-17A. Based on this information, the present study provides new insights for the future study of CA16-induced HFMD and offers new data of diagnostic and therapeutic value for CA16 infection.

Antiviral effects against EV71 of pimprinine and its derivatives isolated from Streptomyces sp

Background

The pimprinine family of compounds represent very important and promising microbial metabolites for drug discovery. However, their ability in inhibiting viral infections has not yet been tested.

Methods

The antiviral activity of the pimprinine family of compounds was evaluated by determining the cytopathic effect (CPE), cell viability or plaque-forming unit (PFU), and virus yield. The mechanism of action against EV71 was determined from the virucidal activity, and effective stage and time-of-addition assays. The effects on EV71 replication were evaluated further by determining viral RNA synthesis, protein expression and cells apoptosis using the SYBR Green assays, immunofluorescence assays and flow cytometric assays, respectively.

Results

Pimprinethine, WS-30581 A and WS-30581 B inhibited EV71-induced CPE, reduced progeny EV71 yields, as well as prevented EV71-induced apoptosis in human rhabdomyosarcoma (RD) cells. These compounds were found to target the early stages of the EV71 replication in cells including viral RNA replication and protein synthesis. They also showed antiviral activity against ADV-7, and were slightly active against CVB3, HSV-1 and H1N1 with a few exceptions. Pimprinine was slightly active or inactive against all the viruses tested. The mechanisms by which these compounds act against the viruses tested may be similar to that demonstrated for EV71.

Conclusion

The data described herein demonstrate that the pimprinine family of compounds are inhibitors effective against the replication of EV71 and ADV-7, so they might be feasible therapeutic agents for the treatment of viral infections.

Discovery of gramine derivatives that inhibit the early stage of EV71 replication in vitro

Enterovirus 71 (EV71) is a notable causative agent of hand, foot, and mouth disease in children, which is associated with an increased incidence of severe neurological disease and death, yet there is no specific treatment or vaccine for EV71 infections. In this study, the antiviral activity of gramine and 21 gramine derivatives against EV71 was investigated in cell-based assays. Eighteen derivatives displayed some degree of inhibitory effects against EV71, in that they could effectively inhibit virus-induced cytopathic effects (CPEs), but the anti-EV71 activity of the lead compound gramine was not observed. Studies on the preliminary modes of action showed that these compounds functioned by targeting the early stage of the EV71 lifecycle after viral entry, rather than inactivating the virus directly, inhibiting virus adsorption or affecting viral release from the cells. Among these derivatives, one (compound 4s) containing pyridine and benzothiazole units showed the most potency against EV71. Further studies demonstrated that derivative 4s could profoundly inhibit viral RNA replication, protein synthesis, and virus-induced apoptosis in RD cells. These results indicate that derivative 4s might be a feasible therapeutic agent against EV71 infection and that these gramine derivatives may provide promising lead scaffolds for the further design and synthesis of potential antiviral agents.

Cytoplasmic viral RNA-dependent RNA polymerase disrupts the intracellular splicing machinery by entering the nucleus and interfering with Prp8

The primary role of cytoplasmic viral RNA-dependent RNA polymerase (RdRp) is viral genome replication in the cellular cytoplasm. However, picornaviral RdRp denoted 3D polymerase (3D^pol) also enters the host nucleus, where its function remains unclear. In this study, we describe a novel mechanism of viral attack in which 3D^pol enters the nucleus through the nuclear localization signal (NLS) and targets the pre-mRNA processing factor 8 (Prp8) to block pre-mRNA splicing and mRNA synthesis. The fingers domain of 3D^pol associates with the C-terminal region of Prp8, which contains the Jab1/MPN domain, and interferes in the second catalytic step, resulting in the accumulation of the lariat form of the splicing intermediate. Endogenous pre-mRNAs trapped by the Prp8-3D^pol complex in enterovirus-infected cells were identified and classed into groups associated with cell growth, proliferation, and differentiation. Our results suggest that picornaviral RdRp disrupts pre-mRNA splicing processes, that differs from viral protease shutting off cellular transcription and translation which contributes to the pathogenesis of viral infection.

RNA-dependent RNA polymerase (RdRp) is an enzyme that catalyzes the replication from an RNA template and is encoded in the genomes of all RNA viruses. RNA viruses in general replicate in cytoplasm and interfere host cellular gene expression by utilizing proteolytic destruction of cellular targets as the primary mechanism. However, several cytoplasmic RNA viral proteins have been found in the nucleus. What do they do in the nucleus? This study utilized picornaviral polymerase to probe the function of RdRp in the nucleus. Our findings reveal a novel mechanism of viruses attacking hosts whereby picornaviral 3D polymerase (3D^pol) enters the nucleus and targets the central pre-mRNA processing factor 8 (Prp8) to block pre-mRNA splicing and mRNA synthesis. The 3D^pol inhibits the second catalytic step of the splicing process, resulting in the accumulation of the lariat-form and the reduction of the mRNA. These results provide new insights into the strategy of a cytoplasmic RNA virus attacking host cell, that differs from viral shutting off cellular transcription and translation which contributes to the viral pathogenesis. To our knowledge, this study shows for the first time that a cytoplasmic RNA virus uses its polymerase to alter cellular gene expression by hijacking the splicing machinery.

A novel universal neutralizing monoclonal antibody against enterovirus 71 that targets the highly conserved "knob" region of VP3 protein

Hand, foot and mouth disease caused by enterovirus 71(EV71) leads to the majority of neurological complications and death in young children. While putative inactivated vaccines are only now undergoing clinical trials, no specific treatment options exist yet. Ideally, EV71 specific intravenous immunoglobulins could be developed for targeted treatment of severe cases. To date, only a single universally neutralizing monoclonal antibody against a conserved linear epitope of VP1 has been identified. Other enteroviruses have been shown to possess major conformational neutralizing epitopes on both the VP2 and VP3 capsid proteins. Hence, we attempted to isolate such neutralizing antibodies against conformational epitopes for their potential in the treatment of infection as well as differential diagnosis and vaccine optimization. Here we describe a universal neutralizing monoclonal antibody that recognizes a conserved conformational epitope of EV71 which was mapped using escape mutants. Eight escape mutants from different subgenogroups (A, B2, B4, C2, C4) were rescued; they harbored three essential mutations either at amino acid positions 59, 62 or 67 of the VP3 protein which are all situated in the “knob” region. The escape mutant phenotype could be mimicked by incorporating these mutations into reverse genetically engineered viruses showing that P59L, A62D, A62P and E67D abolish both monoclonal antibody binding and neutralization activity. This is the first conformational neutralization epitope mapped on VP3 for EV71.

Over the last decade, EV71 has emerged as a major cause of severe hand, foot and mouth disease in the Asia-Pacific region, occasionally leading to fatal brain stem encephalitis in young children. The rapid progression and high mortality of severe EV71 infection makes it vital to identify neutralization epitopes and putative therapeutic monoclonal antibodies. In this study we mapped the first conformational neutralization epitope on the VP3 protein of EV71. This epitope was confirmed by introducing the mutations into reverse genetically engineered viruses which abolished neutralization with monoclonal antibody (mAb)10D3. The importance of this novel neutralization epitope lies in the optimization of putative EV71 vaccines because the VP3 knob could be incorporated together with VP1 into a bivalent subunit vaccine. Further, the universal recognition of a conserved site on EV71 VP3 and not CVA16 makes mAb 10D3 a valuable tool for differential diagnosis of hand, foot and mouth disease. An additional hope is that mAb 10D3 could be used as a therapeutic intravenous immunoglobulin (IVIG).

Analysis of synonymous codon usage in enterovirus 71

Enterovirus 71 (EV71) is the major cause of hand-foot-and-mouth disease in children. In our study, using the complete genome sequences of 42 EV71 representing all three genotypes, we analyzed synonymous codon usage and the relative dinucleotide abundance in EV71 genome. The general correlation between base composition and codon usage bias suggests that mutational pressure rather than natural selection is the main factor that determines the codon usage bias in EV71 genome. Furthermore, we observed that the relative abundance of dinucleotides in EV71 is independent of the overall base composition but is still the result of differential mutational pressure, which also shapes codon usage. In addition, other factors, such as hydrophobicity and aromaticity, also influence the codon usage variation among the genomes of EV71. This study represents the most comprehensive analysis of EV71 codon usage patterns and provides a basic understanding of the mechanisms for codon usage bias.

Mutations in the non-structural protein region contribute to intra-genotypic evolution of enterovirus 71

Background

Clinical manifestations of enterovirus 71 (EV71) range from herpangina, hand-foot-and-mouth disease (HFMD), to severe neurological complications. Unlike the situation of switching genotypes seen in EV71 outbreaks during 1998–2008 in Taiwan, genotype B5 was responsible for two large outbreaks in 2008 and 2012, respectively. In China, by contrast, EV71 often persists as a single genotype in the population and causes frequent outbreaks. To investigate genetic changes in viral evolution, complete EV71 genome sequences were used to analyze the intra-genotypic evolution pattern in Taiwan, China, and the Netherlands.

Results

Genotype B5 was predominant in Taiwan’s 2008 outbreak and was re-emergent in 2012. EV71 strains from both outbreaks were phylogenetically segregated into two lineages containing fourteen non-synonymous substitutions predominantly in the non-structural protein coding region. In China, genotype C4 was first seen in 1998 and caused the latest large outbreak in 2008. Unlike shifting genotypes in Taiwan, genotype C4 persisted with progressive drift through time. A majority of non-synonymous mutations occurred in residues located in the non-structural coding region, showing annual increases. Interestingly, genotype B1/B2 in the Netherlands showed another stepwise evolution with dramatic EV71 activity increase in 1986. Phylogeny of the VP1 coding region in 1971–1986 exhibited similar lineage turnover with genotype C4 in China; however, phylogeny of the 3D-encoding region indicated separate lineage appearing after 1983, suggesting that the 3D-encoding region of genotype B2 was derived from an unidentified ancestor that contributed to intra-genotypic evolution in the Netherlands.

Conclusions

Unlike VP1 coding sequences long used for phylogenetic study of enteroviruses due to expected host immune escape, our study emphasizes a dominant role of non-synonymous mutations in non-structural protein regions that contribute to (re-)emergent genotypes in continuous stepwise evolution. Dozens of amino acid substitutions, especially in non-structural proteins, were identified via genetic changes driven through intra-genotypic evolution worldwide. These identified substitutions appeared to increase viral fitness in the population, affording valuable insights not only for viral evolution but also for prevention, control, and vaccine against EV71 infection.

Epidemiological features of hand-foot-and-mouth disease in Shenzhen, China from 2008 to 2010

This study analysed the spatio-temporal distribution and propagation of hand-foot-and-mouth disease (HFMD) in Shenzhen from 2008 to 2010. Specifically, we examined the epidemiological data, temporal distribution and spatial distribution, and then the relationship between meteorological, social factors and the number of reported HFMD cases was analysed using Spearman's rank correlation. Finally, a geographically weighted regression model was constructed for the number of reported HFMD cases in 2009. It was found that three independent variables, i.e. the number of reported HFMD cases in 2008 and, annual average temperature and precipitation, had different spatial impacts on the number of reported HFMD cases in 2009. In addition, these variables accounted for the propagation mechanism of HFMD in the centre and east of Shenzhen, where the high incidence rate areas are located. These results will be of great help in understanding the spatio-temporal distribution of HFMD and developing approaches to prevent this disease.

Human enterovirus 71 epidemics: what's next?

Human enterovirus 71 (EV71) epidemics have affected various countries in the past 40 years. EV71 commonly causes hand, foot and mouth disease (HFMD) in children, but can result in neurological and cardiorespiratory complications in severe cases. Genotypic changes of EV71 have been observed in different places over time, with the emergence of novel genotypes or subgenotypes giving rise to serious outbreaks. Since the late 1990s, intra- and inter-typic recombination events in EV71 have been increasingly reported in the Asia-Pacific region. In particular, 'double-recombinant' EV71 strains belonging to a novel genotype D have been predominant in mainland China and Hong Kong over the last decade, though co-circulating with a minority of other EV71 subgenotypes and coxsackie A viruses. Continuous surveillance and genome studies are important to detect potential novel mutants or recombinants in the near future. Rapid and sensitive molecular detection of EV71 is of paramount importance in anticipating and combating EV71 outbreaks.

Necrotizing myositis causes restrictive hypoventilation in a mouse model for human enterovirus 71 infection

BACKGROUND

Enterovirus 71 (EV71) infections are associated with a high prevalence of hand, foot and mouth disease (HFMD) in children and occasionally cause lethal complications. Most infections are self-limiting. However, resulting complications, including aseptic meningitis, encephalitis, poliomyelitis-like acute flaccid paralysis, and neurological pulmonary edema or hemorrhage, are responsible for the lethal symptoms of EV71 infection, the pathogenesis of which remain to be clarified.

RESULTS

In the present study, 2-week-old Institute of Cancer Research (ICR) mice were infected with a mouse-adapted EV71 strain. These infected mice demonstrated progressive paralysis and died within 12 days post infection (d.p.i.). EV71, which mainly replicates in skeletal muscle tissues, caused severe necrotizing myositis. Lesions in the central nervous system (CNS) and other tissues were not observed.

CONCLUSIONS

Necrotizing myositis of respiratory-related muscles caused severe restrictive hypoventilation and subsequent hypoxia, which could explain the fatality of EV71-infected mice. This finding suggests that, in addition to CNS injury, necrotic myositis may also be responsible for the paralysis and death observed in EV71-infected mice.

lncRNA expression signatures in response to enterovirus 71 infection

Outbreaks of hand, foot, and mouth disease caused by enterovirus 71 (EV71) have become considerable threats to the health of infants and young children. To identify the cellular long noncoding RNAs (lncRNAs) involved in the host response to EV71 infection, we performed comprehensive lncRNA and mRNA profiling in EV71-infected rhabdomyosarcoma cells through microarray. We observed the differential expression of more than 4800 lncRNAs during infection. Further analysis showed 160 regulated enhancer-like lncRNA and nearby mRNA pairs, as well as 313 regulated Rinn’s lncRNA [M. Guttman I. Amit, M. Garber, C. French, M.F. Lin, D. Feldser, M. Huarte, O. Zuk, B.W. Carey, J.P. Cassady, M.N. Cabili, R. Jaenisch, T.S. Mikkelsen, T. Jacks, N. Hacohen, B.E. Bernstein, M. Kellis, A. Regev, J.L. Rinn, E.S. Lander. Chromatin signature reveals over a thousand highly conserved large non-coding RNAs in mammals. Nature 458 (2009) 223–227, A.M. Khalil, M. Guttman, M. Huarte, M. Garber, A. Raj, D. Rivea Morales, K. Thomas, A. Presser, B.E. Bernstein, A. van Oudenaarden, A. Regev, E.S. Lander, J.L. Rinn. Many human large intergenic noncoding RNAs associate with chromatin-modifying complexes and affect gene expression. Proc. Natl. Acad. Sci. USA 106 (2009) 11667–11672] and nearby mRNA pairs. The results provided information for further research on the prevention and treatment of EV71 infection, as well as on distinguishing severe and mild EV71 cases.

Detection of human enterovirus 71 and Coxsackievirus A16 in an outbreak of hand, foot, and mouth disease in Henan Province, China in 2009

During 2009, an outbreak of hand, foot, and mouth disease (HFMD) enrolled 490 people in Henan Province, causing the death of two children. In order to investigate the pathogens responsible for this outbreak and characterize their genetic characteristics, a total of 508 clinical specimens (stool, throat swab, and vesicle fluid) were collected from the Center for Disease Control and Prevention of Henan Province. Virological investigations (virus isolation, conventional reverse transcription PCR, and real-time reverse transcription PCR) and phylogenetic analysis were performed. It was found that human enterovirus 71 (EV71) was the main pathogen causing this outbreak, while Coxsackievirus A16 (CoxA16) played only a subsidiary role. Phylogenetic analysis of 24 EV71 isolates collected during the period from March 11 to July 24, 2009 showed that they belonged to subgenotypes C4 and C5. Our study for the first time characterizes the epidemiology of HFMD and EV71 infection in Henan Province in 2009 and provides the first direct evidence of the genotype of EV71 circulating in Henan Province at that time. Our study should facilitate the development of public health measures for the control and prevention of HFMD and EV71 infection in at-risk individuals in China.

Characterization and specificity of the linear epitope of the enterovirus 71 VP2 protein

Background

Enterovirus 71 (EV71) has emerged as a major causative agent of hand, foot and mouth disease in the Asia-Pacific region over the last decade. Hand, foot and mouth disease can be caused by different etiological agents from the enterovirus family, mainly EV71 and coxsackieviruses, which are genetically closely related. Nevertheless, infection with EV71 may occasionally lead to high fever, neurologic complications and the emergence of a rapidly fatal syndrome of pulmonary edema associated with brainstem encephalitis. The rapid progression and high mortality of severe EV71 infection has highlighted the need for EV71-specific diagnostic and therapeutic tools. Monoclonal antibodies are urgently needed to specifically detect EV71 antigens from patient specimens early in the infection process. Furthermore, the elucidation of viral epitopes will contribute to the development of targeted therapeutics and vaccines.

Results

We have identified the monoclonal antibody 7C7 from a screen of hybridoma cells derived from mice immunized with the EV71-B5 strain. The linear epitope of 7C7 was mapped to amino acids 142-146 (EDSHP) of the VP2 capsid protein and was characterized in detail. Mutational analysis of the epitope showed that the aspartic acid to asparagine mutation of the EV71 subgenogroup A (BrCr strain) did not interfere with antibody recognition. In contrast, the serine to threonine mutation at position 144 of VP2, present in recently emerged EV71-C4 China strains, abolished antigenicity. Mice injected with this virus strain did not produce any antibodies against the VP2 protein. Immunofluorescence and Western blotting confirmed that 7C7 specifically recognized EV71 subgenogroups and did not cross-react to Coxsackieviruses 4, 6, 10, and 16. 7C7 was successfully used as a detection antibody in an antigen-capture ELISA assay.

Conclusions

Detailed mapping showed that the VP2 protein of Enterovirus 71 contains a single, linear, non-neutralizing epitope, spanning amino acids 142-146 which are located in the VP2 protein's E-F loop. The S/T(144) mutation in this epitope confers a loss of VP2 antigenicity to some newly emerged EV71-C4 strains from China. The corresponding monoclonal antibody 7C7 was used successfully in an AC-ELISA and did not cross-react to coxsackieviruses 4, 6, 10, and 16 in immunofluorescence assay and Western blots. 7C7 is the first monoclonal antibody described, that can differentiate Coxsackievirus 16 from Enterovirus 71.

Cross-reactivity of anti-EV71 IgM and neutralizing antibody in series sera of patients infected with Enterovirus 71 and Coxsackievirus A 16

OBJECTIVES

To evaluate the cross-reactivity of anti-EV71 IgM and neutralizing antibody in series sera of patients infected with EV71 and CA16.

METHODS

Real-time RT-PCR, virus isolation, ELISA and neutralization test were used to detect enteroviruses from clinical specimens and series sera of 79 HFMD patients.

RESULTS

27 EV71, 37 CA16, and 11 other enterovirus-infected patients were identified by RT-PCR. Among EV71 infected patients, anti-EV71 IgM positive ratios were 87.5% during 1-3 days after onset and 100% over 4 days after onset. In CA16 infected patients, the positive ratios were 7.4%, 26.4%, and 62.5% during 1-3 days, 4-6 days, and over 6 days after onset, respectively. Meanwhile, the results of neutralization test showed 18.9% of CA16 infected patients and 11.1% of EV71 infected patients present high cross-neutralization antibody against each other.

CONCLUSIONS

Cross-reactivity of anti-EV71 IgM in patients infected with EV71 and CA16 becomes stronger with the progress of disease. Moreover, high cross-neutralization antibody existing in part of patients suggests that the immune reactivity to EV71 infection can be recalled by CA16, and the immune reactivity to CA16 infection can be recalled by EV71. Therefore, identifying enteroviruses by neutralization test may not be an ideal selection.

Partial protection against enterovirus 71 (EV71) infection in a mouse model immunized with recombinant Newcastle disease virus capsids displaying the EV71 VP1 fragment

Enterovirus 71 (EV71) infection may cause severe neurological complications, particularly in young children. Despite the risks, there are still no commercially available EV71 vaccines. Hence, a candidate vaccine construct, containing recombinant Newcastle disease virus capsids that display an EV71 VP1 fragment (NPt-VP1(1-100) ) protein, was evaluated in a mouse model of EV71 infection. Previously, it was shown that this protein construct provoked a strong immune response in vaccinated adult rabbits. That study, however, did not address the issue of its effectiveness against EV71 infection in young animals. In the present study, EV71 viral challenge in vaccinated newborn mice resulted in more than 40% increase in survival rate. Significantly, half of the surviving mice fully recovered from their paralysis. Histological analysis of all of the surviving mice revealed a complete clearance of EV71 viral antigens from their brains and spinal cords. In hind limb muscles, the amounts of the antigens detected correlated with the degrees of tissue damage and paralysis. Findings from this study provide evidence that immunization with the NPt-VP1(1-100) immunogen in a newborn mouse model confers partial protection against EV71 infection, and also highlights the importance of NPt-VP1(1-100) as a possible candidate vaccine for protection against EV71 infections.

Prolonged exclusive breastfeeding, autumn birth and increased gestational age are associated with lower risk of fever in children with hand, foot, and mouth disease

Epidemics of hand, foot, and mouth disease (HFMD) have been emerging and reemerging in recent years. This study aims to investigate whether breastfeeding and other factors may affect the profile of fever and disease course in children with HFMD. Three hundred seventy-two preschool children with HFMD were included. The demographics, environmental factors, and delivery- and feeding-associated factors in the children were obtained and their effects on the profile of fever and disease course were analyzed. Of the 372 children, 139 (37.37%) had fever during the disease course. Gender, breastfeeding pattern, birth season and gestational age were significantly different between the children with and without fever (p = 0.034, p < 0.0001, p = 0.035 and p = 0.013, respectively). After multivariate-adjusted analysis, prolonged exclusive breastfeeding (p = 0.001, OR 0.401, 95% CI 0.229-0.704), autumn birth (p = 0.007, OR 0.409, 95% CI 0.214-0.784) and higher gestational age (p = 0.029, OR 0.089, 95% CI 0.010-0.781) were protective factors for the incidence of fever.

The characteristics of blood glucose and WBC counts in peripheral blood of cases of hand foot and mouth disease in China: a systematic review

BACKGROUND

Outbreaks of Hand Foot and Mouth Disease (HFMD) have occurred in many parts of the world especially in China. We aimed to summarize the characteristics of the levels of blood glucose and white blood cell (WBC) counts in cases of HFMD in Mainland China and Taiwan, using meta-analysis based on systematic review of published articles.

METHODS

We systematically reviewed published studies, from the MEDLINE and WANFANG Data, about the levels of blood glucose and WBC counts in cases of HFMD until 15(th) June 2011, and quantitatively summarized the characteristics of them using meta-analysis.

RESULTS

In total, 37 studies were included in this review. In Mainland China and Taiwan, generally, the average level of blood glucose, the prevalence of hyperglycemia, WBC counts and the prevalence of leukocytosis increased with the severity of the illness. There was no significant difference in the prevalence of leukocytosis between ANS (autonomic nervous system dysregulation)/PE (pulmonary edema) group and CNS (central nervous system) group, and in the average level of blood glucose between healthy controls and mild cases of HFMD. WBC counts in cases infected by EV71 were less than those in cases infected by CA16.

CONCLUSIONS

our analyses indicated that blood glucose and WBC counts increased with the severity of HFMD disease, which would help doctors to manage patients efficiently.

The association of recombination events in the founding and emergence of subgenogroup evolutionary lineages of human enterovirus 71

Enterovirus 71 (EV71) is responsible for frequent large-scale outbreaks of hand, foot, and mouth disease worldwide and represent a major etiological agent of severe, sometimes fatal neurological disease. EV71 variants have been classified into three genogroups (GgA, GgB, and GgC), and the latter two are further subdivided into subgenogroups B1 to B5 and C1 to C5. To investigate the dual roles of recombination and evolution in the epidemiology and transmission of EV71 worldwide, we performed a large-scale genetic analysis of isolates (n = 308) collected from 19 countries worldwide over a 40-year period. A series of recombination events occurred over this period, which have been identified through incongruities in sequence grouping between the VP1 and 3Dpol regions. Eleven 3Dpol clades were identified, each specific to EV71 and associated with specific subgenogroups but interspersed phylogenetically with clades of coxsackievirus A16 and other EV species A serotypes. The likelihood of recombination increased with VP1 sequence divergence; mean half-lives for EV71 recombinant forms (RFs) of 6 and 9 years for GgB and GgC overlapped with those observed for the EV-B serotypes, echovirus 9 (E9), E30, and E11, respectively (1.3 to 9.8 years). Furthermore, within genogroups, sporadic recombination events occurred, such as the linkage of two B4 variants to RF-W instead of RF-A and of two C4 variants to RF-H. Intriguingly, recombination events occurred as a founding event of most subgenogroups immediately preceding their lineage expansion and global emergence. The possibility that recombination contributed to their subsequent spread through improved fitness requires further biological and immunological characterization.

Serum microRNA expression profile distinguishes enterovirus 71 and coxsackievirus 16 infections in patients with hand-foot-and-mouth disease

Altered circulating microRNA (miRNA) profiles have been noted in patients with microbial infections. We compared host serum miRNA levels in patients with hand-foot-and-mouth disease (HFMD) caused by enterovirus 71 (EV71) and coxsackievirus 16 (CVA16) as well as in other microbial infections and in healthy individuals. Among 664 different miRNAs analyzed using a miRNA array, 102 were up-regulated and 26 were down-regulated in sera of patients with enteroviral infections. Expression levels of ten candidate miRNAs were further evaluated by quantitative real-time PCR assays. A receiver operating characteristic (ROC) curve analysis revealed that six miRNAs (miR-148a, miR-143, miR-324-3p, miR-628-3p, miR-140-5p, and miR-362-3p) were able to discriminate patients with enterovirus infections from healthy controls with area under curve (AUC) values ranged from 0.828 to 0.934. The combined six miRNA using multiple logistic regression analysis provided not only a sensitivity of 97.1% and a specificity of 92.7% but also a unique profile that differentiated enterovirial infections from other microbial infections. Expression levels of five miRNAs (miR-148a, miR-143, miR-324-3p, miR-545, and miR-140-5p) were significantly increased in patients with CVA16 versus those with EV71 (p<0.05). Combination of miR-545, miR-324-3p, and miR-143 possessed a moderate ability to discrimination between CVA16 and EV71 with an AUC value of 0.761. These data indicate that sera from patients with different subtypes of enteroviral infection express unique miRNA profiles. Serum miRNA expression profiles may provide supplemental biomarkers for diagnosing and subtyping enteroviral HFMD infections.

Comparing Enterovirus 71 with Coxsackievirus A16 by analyzing nucleotide sequences and antigenicity of recombinant proteins of VP1s and VP4s

BACKGROUND

Enterovirus 71 (EV71) and Coxsackievirus A16 (CA16) are two major etiological agents of Hand, Foot and Mouth Disease (HFMD). EV71 is associated with severe cases but not CA16. The mechanisms contributed to the different pathogenesis of these two viruses are unknown. VP1 and VP4 are two major structural proteins of these viruses, and should be paid close attention to.

RESULTS

The sequences of vp1s from 14 EV71 and 14 CA16, and vp4s from 10 EV71 and 1 CA16 isolated in this study during 2007 to 2009 HFMD seasons were analyzed together with the corresponding sequences available in GenBank using DNAStar and MEGA 4.0. Phylogenetic analysis of complete vp1s or vp4s showed that EV71 isolated in Beijing belonged to C4 and CA16 belonged to lineage B2 (lineage C). VP1s and VP4s from 4 strains of viruses expressed in E. coli BL21 cells were used to detect IgM and IgG in human sera by Western Blot. The detection of IgM against VP1s of EV71 and CA16 showed consistent results with current infection, while none of the sera were positive against VP4s of EV71 and CA16. There was significant difference in the positive rates between EV71 VP1 and CA16 VP1 (χ(2) = 5.02, P < 0.05) as well as EV71 VP4 and CA16 VP4 (χ(2) = 15.30, P < 0.01) in the detection of IgG against recombinant proteins with same batch of serum samples. The sera-positive rate of IgG against VP1 was higher than that against VP4 for both EV71 (χ(2) = 26.47, P < 0.01) and CA16 (χ(2) = 16.78, P < 0.01), which might be because of different positions of VP1 and VP4 in the capsid of the viruses.

CONCLUSIONS

EV71 and CA16 were highly diverse in the nucleotide sequences of vp1s and vp4s. The sera positive rates of VP1 and VP4 of EV71 were lower than those of CA16 respectively, which suggested a less exposure rate to EV71 than CA16 in Beijing population. Human serum antibodies detected by Western blot using VP1s and VP4s as antigen indicated that the immunological reaction to VP1 and VP4 of both EV71 and CA16 was different.

Evaluation of sentinel surveillance system for monitoring hand, foot and mouth disease in Hong Kong

OBJECTIVES

A sentinel surveillance system (SSS) was set up in Hong Kong to monitor hand, foot and mouth disease (HFMD) trends. This evaluation assessed the performance of the SSS from 2001 to 2009, and aimed to identify areas for improvement.

STUDY DESIGN

A retrospective review using structured guidelines for evaluating public health surveillance systems published by the US Centers for Disease Control and Prevention.

METHODS

The effectiveness of the SSS was evaluated using routine service statistics, laboratory surveillance data, and results of an acceptability survey conducted among the sentinel doctors. This information was used to assess various attributes of the SSS including simplicity, flexibility, data quality, usefulness, sensitivity, specificity, positive predictive value (PPV), representativeness, timeliness and acceptability.

RESULTS

The SSS was simple and flexible with high-quality data. It correlated well with the laboratory surveillance data (P < 0.001) and facilitated early detection of community epidemics. It helped to identify seasonal trends and high-risk groups. Specificity was high (83.4-88.5%), while sensitivity and PPV were borderline satisfactory (38.4-56.8%). The sentinel clinics were representative of the population distribution. The SSS was acceptable to the sentinel doctors, but 17.9-28.2% of them had delays in reporting.

CONCLUSIONS

The SSS is effective for monitoring HFMD trends in Hong Kong, and is useful for initiating preventive measures.

Inhibition of enterovirus 71 replication by chrysosplenetin and penduletin

In recent years, enterovirus 71 (EV71) infections have caused an increasing epidemic in young children, accompanying with more severe nervous system disease and more deaths. Unfortunately, there is no specific medication for it so far. Here we investigated the anti-EV71 activity of chrysosplenetin and penduletin, two o-methylated flavonols isolated from the leaves of Laggera pterodonta. These two compounds were found to have strong activity in vitro against EV71 with low cytotoxicity. In the cytopathic effect (CPE) inhibition assays, both plaque reduction assay and virus yield inhibition assay, the compounds showed a similar 50% inhibitory concentration (IC(50)) value of about 0.20 μM. The selectivity indices (SI) of chrysosplenetin and penduletin were 107.5 and 655.6 in African green monkey kidney (Vero) cells, and 69.5 and 200.5 in human rhabdomyosarcoma (RD) cells, accordingly. The preliminary mechanism analysis indicates that they function not through blocking virus entry or inactivating virus directly but inhibiting viral RNA replication. In the time-of-addition assay, both compounds inhibited progeny virus production and RNA replication by nearly 100% when introduced within 4h post infection. In addition to EV71, both compounds inhibited several other human enteroviruses with similar efficacy. These findings provide a significant lead for the discovery of anti-EV71 drug.

Estimation of the basic reproduction number of enterovirus 71 and coxsackievirus A16 in hand, foot, and mouth disease outbreaks

BACKGROUND

Coxsackievirus A16 (Cox A16) and enterovirus 71 (EV71) are common pathogens causing hand, foot, and mouth disease (HFMD) in pediatric population. Little is known about the basic reproductive number (R0) for these enteroviruses.

METHODS

We estimated the R0 of EV71 and of Cox A16 from laboratory-confirmed HFMD outbreaks reported to the Department of Health, from 2004 to 2009. We derived a mathematical model and calculated R₀ based on the cumulative number of cases at the initial growth phase of the outbreaks, as determined by the epidemic curves. We tested the association of R₀ with settings and sizes of the institution and total number of persons affected.

RESULTS

We analyzed 34 outbreaks, 27 caused by Cox A16 and 7 caused by EV71. Assuming the incubation period to be 5 days, the median R₀ of EV71 was 5.48 with an interquartile range of 4.20 to 6.51, whereas the median R₀ of Cox A16 was 2.50 with an interquartile range of 1.96 to 3.67. The R₀ of EV71 was significantly higher than that of CoxA16, P = 0.002; and sensitivity analysis showed the same results. The R₀ was not associated with outbreak settings, sizes of the institutions, or number of persons affected.

CONCLUSIONS

The R₀ for EV71 and for Cox A16 was determined using a model which showed that the R₀ for EV71 was higher than that of Cox A16. This finding helps better understand the transmission dynamics of HFMD outbreaks and formulate public health measures for controlling the disease.