Update of enterovirus 71 infection: epidemiology, pathogenesis and vaccine

Phylogeographic dynamics and molecular characteristics of Enterovirus 71 in China

Enterovirus 71 (EV71) and coxsackievirus (CV-A16) are the major etiological agents of hand, foot and mouth disease (HFMD). This report reviewed the full-length genomic sequences of EV71 identified in different provinces of China between 1998 and 2019 (a total of 312) in addition to eight worldwide reference genomes to address the genomic evolution and genetic events. The main prevalent EV71 strians in China are C4 genotypes, co-circulating with a few A, B5, C1, and C2 subgenotypes. A new emerging subgenotype in China was identified and classified as B6 genotype. Phylogeographic analysis revealed multiple branches, where a Jiangsu strain 2006-52-9 (GenBank ID: KP266579.1) was linked to different subgenotypes through multiple long mutant branches, including the CV-A16 viruses through the A genotype. Furthermore, identification of 28 natural recombination events suggests that the emergence of new genotypes are associated with intratypic recombination involving EV71 strains and intertypic recombination between EV71 and CV-A16 strains. Compared with the structural proteins, the non-structural proteins of EV71 seem to be highly variable with the highest variable regions of peptidase C3 (3C protein), P2A, and the N-terminus of RNA-dependent RNA polymerase. This study updates the phylogenetic and phylogeographic information of EV71 and provides clues to the emergence of new genotypes of EV71 based on genetics.

Enterovirus A Shows Unique Patterns of Codon Usage Bias in Conventional Versus Unconventional Clade

Enterovirus A (EV-A) species cause hand, foot and mouth disease (HFMD), threatening the health of young children. Understanding the mutual codon usage pattern of the virus and its host(s) has fundamental and applied values. Here, through examining multiple codon usage parameters, we found that the codon usage bias among EV-A strains varies and is clade-specific. EVA76, EVA89, EVA90, EVA91 and EVA92, the unconventional clade of EV-A strains, show unique codon usage pattern relative to the two conventional clades, including EVA71, CVA16, CVA6 and CVA10, etc. Analyses of Effective Number of Codon (ENC), Correspondence Analysis (COA) and Parity Rule 2 (PR2), etc., revealed that the codon usage patterns of EV-A strains are shaped by mutation pressure and natural selection. Based on the neutrality analysis, we determined the dominant role of natural selection in the formation of the codon usage bias of EV-A. In addition, we have determined the codon usage compatibility of potential hosts for EV-A strains using codon adaptation index (CAI), relative codon deoptimization index (RCDI) and similarity index (SiD) analyses, and found that EV-A showed host-specific codon adaptation patterns in different clades. Finally, we confirmed that the unique codon usage pattern of the unconventional clade affected protein expression level in human cell lines. In conclusion, we identified novel characteristics of codon usage bias in distinct EV-A clades associated with their host range, transmission and pathogenicity.

Cell pyroptosis in picornavirus and its potential for treating viral infection

Cell pyroptosis has received increased attention due to the associations between innate immunity and disease, and it has become a major focal point recently due to in-depth studies of cancer. With increased research on pyroptosis, scientists have discovered that it has an essential role in viral infections, especially in the occurrence and development of some picornavirus infections. Many picornaviruses, including Coxsackievirus, a71 enterovirus, human rhinovirus, encephalomyocarditis virus, and foot-and-mouth disease virus induce pyroptosis to varying degrees. This review summarized the mechanisms by which these viruses induce cell pyroptosis, which can be an effective defense against pathogen infection. However, excessive inflammasome activation or pyroptosis also can damage the host's health or aggravate disease progression. Careful approaches that acknowledge this dual effect will aid in the exploration of picornavirus infections and the mechanisms that produce the inflammatory response. This information will promote the development of drugs that can inhibit cell pyroptosis and provide new avenues for future clinical treatment. This article is protected by copyright. All rights reserved.

Neutralizing Enterovirus D68 Antibodies in Children after 2014 Outbreak, Kansas City, Missouri, USA

Antibodies to B1, B2, and D clade viruses were detected.

Enterovirus D68 (EV-D68) causes severe respiratory illness outbreaks among children, particularly those with asthma. We previously detected neutralizing antibodies against the predominant EV-D68 B1 clade in the 2014 outbreak in serum collected before the outbreak (2012–2013) from persons 24 months to 85 years of age. We recently detected neutralizing antibodies to the 2014 B1, B2, and D clade viruses in serum collected after the 2014 outbreak (April–May 2017) from 300 children 6 months to 18 years of age. B1 virus neutralizing antibodies were found in 100% of patients, even children born after 2014; B2 in 84.6%, and D in 99.6%. In 2017, titers increased with patient age and were higher than titers in 2012–2013 from comparably aged children. Rate of seronegativity was highest (15.3%) for B2 virus. Multivariate analysis revealed an association between asthma and higher titers against B2 and D viruses. EV-D68 seems to have circulated during 2014–2017.

An auto-antibody identified from phenotypic directed screening platform shows host immunity against EV-A71 infection

Background

Enterovirus A71 (EV-A71) is a neurotropic virus which may cause severe neural complications, especially in infants and children. The clinical manifestations include hand-foot-and-mouth disease, herpangina, brainstem encephalitis, pulmonary edema, and other severe neurological diseases. Although there are some vaccines approved, the post-marketing surveillance is still unavailable. In addition, there is no antiviral drugs against EV-A71 available.

Methods

In this study, we identified a novel antibody that could inhibit viral growth through a human single chain variable fragment (scFv) library expressed in mammalian cells and panned by infection with lethal dose of EV-A71.

Results

We identified that the host protein α-enolase (ENO1) is the target of this scFv, and anti-ENO1 antibody was found to be more in mild cases than severe EV-A71 cases. Furthermore, we examined the antiviral activity in a mouse model. We found that the treatment of the identified 07-human IgG₁ antibody increased the survival rate after virus challenge, and significantly decreased the viral RNA and the level of neural pathology in brain tissue.

Conclusions

Collectively, through a promising intracellular scFv library expression and screening system, we found a potential scFv/antibody which targets host protein ENO1 and can interfere with the infection of EV-A71. The results indicate that the usage and application of this antibody may offer a potential treatment against EV-A71 infection.

Neurocognitive Deficits and Sequelae Following Severe hand, foot, and mouth disease from 2009 to 2017, in JiangSu Province, China: A Long-Term Follow-Up Study

BACKGROUND

To evaluate the long-term sequela and cognitive profile resulting from severe hand, foot and mouth disease (HFMD) with central nervous system (CNS) involvement.

METHODS

Two-hundred-and-ninety-four HFMD cases were included in a retrospective follow-up study. Physical examination were conducted. The Chinese Wechsler Preschool and Primary Scale of Intelligence, Fourth Edition (WPPSI-IV) was used to assess intelligence.

RESULTS

Fifty-eight mild HFMD cases and 99 severe HFMD cases with mild CNS involvement did not present any neurological sequelae. While the sequelae incidence of severe HFMD with more severe CNS complications were 50.0%. The proportion of full scale intelligence quotient (FSIQ) impairment was 45.0%. In the 2:6-3:11 age group, severe HFMD with more severe CNS complications and lower maternal education level were risk factors for verbal comprehension disorder. Urban-rural residence and lower paternal education level were risk factors for FSIQ disorder. Furthermore, in the 4:0-6:11 age group, severe HFMD with more severe CNS complication was a risk factor for visual spatial disorder and fluid reasoning disorder. Lower paternal education level was a risk factor for FSIQ disorder.

CONCLUSION

Early assessment and intervention among severe HFMD patients with more severe CNS involvement at a very young age will prove beneficial for their future performance.

Ginsenoside Rb1 is an immune-stimulatory agent with antiviral activity against enterovirus 71

ETHNOPHARMACOLOGICAL RELEVANCE

According to the theory of traditional Chinese medicine, the main pathogenesis of severe hand, foot and mouth disease (HFMD) is that the heat and wet poisons are deeply trapped in the viscera, which causes the deficiency of Qi and Yin in the patient's body. Ginsenoside Rb1 (Rb1) is the most abundant triterpenoid saponin in Panax quinquefolius L., which has the function of Qi-invigorating and Yin-nourishing. Enterovirus 71 (EV71) is one of the causative pathogens of HFMD, especially the form associated with some lethal complications. Therefore, the therapeutic effect of Rb1 on this disease caused by EV71 infection is worth exploring.

AIM OF THE STUDY

We explored the effective antiviral activities of Rb1 against EV71 in vitro and in vivo and investigated its preliminary antiviral mechanisms.

MATERIAL AND METHODS

EV71-infected two-day-old suckling mice model was employed to detect the antiviral effects of Rb1 in vivo. To detect the antiviral effects of Rb1 in vitro, cytopathic effect (CPE) reduction assay was performed in EV71-infected Rhabdomyosarcoma (RD) cells. Interferon (IFN)-β interference experiment was employed to detect the antiviral mechanism of Rb1.

RESULTS

In this paper, we first found that Rb1 exhibited strong antiviral activities in EV71-infected suckling mice when compared to those of ribavirin. Administration of Rb1 reduced the CPE of EV71-infected RD cells in a dose-dependent manner. Moreover, EV71-induced viral protein-1 (VP-1) expression was significantly reduced by Rb1 administration in vitro and in vivo. Furthermore, Rb1 treatment could induce high cellular and humoral immune responses in vivo. Meanwhile, Rb1 contributed to the enhanced Type I IFN responses and IFN-β knockdown reversed the antiviral activity of Rb1 in vitro.

CONCLUSION

In summary, our findings suggest that Rb1 is an immune-stimulatory agent and provide an insight into therapeutic potentials of Rb1 for the treatment of EV71 infection.

Inhibition of Enterovirus A71 by a Novel 2-Phenyl-Benzimidazole Derivative

Enterovirus A71 (EV-A71) infection has emerged as a significant public health concern at the global level. Epidemic events of EV-A71 have been reported worldwide, and this succession of outbreaks has heightened concern that EV-A71 may become a public health threat. In recent years, widespread A71 enterovirus also occurred in European countries. EV-A71 infection causes hand-foot-mouth disease (HFMD), herpangina, and fever. However, it can sometimes induce a variety of neurological complications, including encephalitis, aseptic meningitis, pulmonary edema, and acute flaccid paralysis. We identified new benzimidazole derivatives and described theirin vitrocytotoxicity and broad-spectrum anti-enterovirus activity. Among them, derivative 2b resulted in interesting activity against EV-A71, and therefore it was selected for further investigations. Compound 2b proved to be able to protect cell monolayers from EV-A71-induced cytopathogenicity, with an EC₅₀ of 3 µM. Moreover, Vero-76 cells resulted in being significantly protected from necrosis and apoptosis when treated with 2b at 20 and 80 µM. Compound 2b reduced viral adsorption to Vero-76 cells, and when evaluated in a time-of-addition assay, the derivative had the highest effect when added during the infection period. Moreover, derivative 2b reduced viral penetration into host cells. Besides, 2b did not affect intestinal monolayers permeability, showing no toxic effects. A detailed insight into the efficacy of compound 2b against EV-A71 showed a dose-dependent reduction in the viral titer, also at low concentrations. Mechanism of action investigations suggested that our derivative can inhibit viral endocytosis by reducing viral attachment to and penetration into host cells. Pharmacokinetic and toxicity predictions validated compound 2b as a good candidate for furtherin vivoassays.

Phytochemical Compositions and Biological Activities of Essential Oils from the Leaves, Rhizomes and Whole Plant of Hornstedtia bella Škorničk

The rapid emergence of drug-resistant strains and novel viruses have motivated the search for new anti-infectious agents. In this study, the chemical compositions and cytotoxicity, as well as the antibacterial, antifungal, antitrichomonas, and antiviral activities of essential oils from the leaves, rhizomes, and whole plant of Hornstedtia bella were investigated. The GC/MS analysis showed that β-pinene, E-β-caryophyllene, and α-humulene were found at high concentrations in the essential oils. The essential oils exhibited (i) inhibition against Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, Staphylococcus epidermidis with minimum inhibitory concentrations (MIC) and minimum lethal concentration (MLC) values from 1 to 4% (v/v); (ii) MIC and MLC values from 2 to 16% (v/v) in Candida tropicalis and Candida parapsilosis; (iii) MIC and MLC values from 4 to 16% in Enterococcus faecalis; and (iv) MIC and MLC values from 8 to greater than or equal to 16% (v/v) in the remaining strains, including Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Candida albicans, and Candida glabrata. In antitrichomonas activity, the leaves and whole-plant oils of Hornstedtia bella possessed IC₅₀, IC₉₀, and MLC values of 0.008%, 0.016%, and 0.03% (v/v), respectively, whilst those of rhizomes oil had in turn, 0.004%, 0.008%, and 0.016% (v/v).Besides, the leaf oil showed a weak cytotoxicity against Vero 76 and MRC-5; meanwhile, rhizomes and whole-plant oils did not exert any toxic effects on cell monolayers. Finally, these oils were not active against EV-A71.

Immunization with a fusion protein vaccine candidate generated from truncated peptides of human enterovirus 71 protects mice from lethal enterovirus 71 infections

Background

Prophylactic vaccines are critical in preventing hand, foot, and mouth disease (HFMD) primarily caused by human enterovirus 71 (EV71) infection. Children aged less than 5 years are especially susceptible to EV71 infections. In addition to the development of vaccines containing the inactivated virus, those containing virus-like particles (VLPs) with repeated antigens also constitute an effective preventive strategy for EV71 infections, with safety and productivity advantages. We previously developed a fusion protein composed with truncated peptides of the EV71 capsid protein, which assembled into spherical particles. This study aimed to assess the immunoprotective effects of this fusion protein as a vaccine candidate in a mouse model of EV71 infection.

Methods

To evaluate the protective effect of fusion protein vaccine candidate, neonatal mice born by immunized female mice, as well as normal neonatal mice immunized twice were infected with EV71 virus. Whereafter, the survival rates, clinical scores and viral loads were measured.

Results

The high dosage and booster immunization helped induce specific serum antibodies with high neutralization titers, which were transferred to neonatal mice, thereby facilitating effective resistance towards EV71 infection. An active immune response was also observed in neonatal mice which generated following immunization.

Conclusions

The present results suggest that this fusion protein is a suitable vaccine candidate in treating EV71 infections.

Chromogranin A provides additional prognostic information in children with severe hand, foot, and mouth disease: A prospective observational study

OBJECTIVE

Severe hand, foot, and mouth disease (HFMD) is associated with high mortality in children, and persistent sympathetic activation is a common presentation. The aim of this study was to prospectively investigate serum chromogranin A (CHGA) levels and their prognostic role in this condition.

METHODS

Serum CHGA, creatine kinase myocardial band (CK-MB), serum D-dimer, norepinephrine, blood glucose, lactate, and C-reactive protein levels, white blood cell (WBC) counts, usage of vasopressors, pediatric risk of mortality Ⅲ (PRISM-Ⅲ) scores, and viral etiology were measured upon pediatric intensive care unit (PICU) admission. The correlation between clinical outcomes and the indicators listed above were analyzed, and the ability of CHGA as a biomarker to predict mortality was evaluated.

RESULTS

Serum CHGA levels were higher in the non-survivors group than in the survivors group (median (interquartile range): 434.8 (374.3-502.4) vs 183.3 (131.9-246.9) μg/l; p < 0.001) and were correlated with norepinephrine (r = 0.37. p < 0.001), blood glucose (r = 0.32, p = 0.001), lactate (r = 0.25, p = 0.009), WBC (r = 0.20, p = 0.039), and PRISM-Ⅲ scores (r = 0.748, p < 0.0001). Patients suffering neurogenic pulmonary edema, those infected with enterovirus A71, and those requiring more vasopressors had higher serum CHGA levels (median (interquartile range): 385 (239.9-488.8) vs 161 (115.6-222.9), 340.6 (190.6-436.0) vs 150.5 (112.1-210.0), 395.6 (209.1-487.0) vs 167.7 (110.5-240.5) μg/l, respectively; p < 0.0001). The CHGA level upon PICU admission in severe HFMD could be an independent risk factor for mortality (adjusted odds ratio 2.459, 95% confidence interval 1.054-5.906, p = 0.038) with high specificity (87.5%) and sensitivity (82.6%) (cut-off value at 339.6 μg/l).

CONCLUSIONS

The CHGA level in severe HFMD was found to be associated with cardiopulmonary failure. If measured upon PICU admission, CHGA may provide additional prognostic information in this disease.

Synthesis and Broad Antiviral Activity of Novel 2-aryl-isoindolin-1-ones towards Diverse Enterovirus A71 Clinical Isolates

Enterovirus 71 (EV-A71) is the main causative pathogen of childhood hand, foot and mouth disease. Effective medicine is currently unavailable for the treatment of this viral disease. Using the fragment-hopping strategy, a series of 2-aryl-isoindolin-1-one compounds were designed, synthesized and investigated for their in vitro antiviral activity towards multiple EV-A71 clinical isolates (H, BrCr, Shenzhen98, Jiangsu52) in Vero cell culture in this study. The structure⁻activity relationship (SAR) studies identified 2-phenyl-isoindolin-1-ones as a new potent chemotype with potent antiviral activity against EV-A71. Ten out of the 24 tested compounds showed significant antiviral activity (EC₅₀ < 10 µM) towards four EV-A71 strains. Compounds A3 and A4 exhibited broad and potent antiviral activity with the 50% effective concentration (EC₅₀) values in the range of 1.23⁻1.76 μM. Moreover, the selectivity indices of A3 and A4 were significantly higher than those of the reference compound, pirodavir. The western blotting experiment indicated that the viral VP1 was significantly decreased at both the protein and RNA level in a dose-dependent manner following treatment with compound A3. Moreover, compound A3 inhibited the viral replication by acting on the virus entry stage. In summary, this study led to the discovery of 2-aryl-isoindolin-1-ones as a promising scaffold with potent anti-EV-A71 activities, which deserves further in-depth studies.

Neutralizing Antibody against Enterovirus D68 in Children and Adults before 2014 Outbreak, Kansas City, Missouri, USA1

We evaluated enterovirus D68 seroprevalence in Kansas City, Missouri, USA, from samples obtained during 2012-2013. Neutralizing antibodies against Fermon and the dominant 2014 Missouri isolate were universally detected. Titers increased with age. Widespread circulation of enterovirus D68 occurred before the 2014 outbreak. Research is needed to determine a surrogate of protection.

Clinical Value of Dorsal Medulla Oblongata Involvement Detected With Conventional Magnetic Resonance Imaging for Prediction of Outcome in Children With Enterovirus 71-Related Brainstem Encephalitis

BACKGROUND

Brainstem encephalitis is the most common neurologic complication after enterovirus 71 infection. The involvement of brainstem, especially the dorsal medulla oblongata, can cause severe sequelae or death in children with enterovirus 71 infection. We aimed to determine the prevalence of dorsal medulla oblongata involvement in children with enterovirus 71-related brainstem encephalitis (EBE) by using conventional magnetic resonance imaging (MRI) and to evaluate the value of dorsal medulla oblongata involvement in outcome prediction.

METHODS

Forty-six children with EBE were enrolled in the study. All subjects underwent a 1.5 Tesla MRI examination of the brain. The disease distribution and clinical data were collected. Dichotomized outcomes (good vs. poor) at longer than 6 months were available for 28 patients. Logistic regression was used to determine whether the MRI-confirmed dorsal medulla oblongata involvement resulted in improved clinical outcome prediction when compared with other location involvement.

RESULTS

Of the 46 patients, 35 had MRI evidence of dorsal medulla oblongata involvement, 32 had pons involvement, 10 had midbrain involvement and 7 had dentate nuclei involvement. Patients with dorsal medulla oblongata involvement or multiple area involvement were significantly more often in the poor outcome group than in the good outcome group. Logistic regression analysis showed that dorsal medulla oblongata involvement was the most significant single variable in outcome prediction (predictive accuracy, 90.5%), followed by multiple area involvement, age and initial Glasgow Coma Scale score.

CONCLUSIONS

Dorsal medulla oblongata involvement on conventional MRI correlated significantly with poor outcomes in EBE children, improved outcome prediction when compared with other clinical and disease location variables, and was most predictive when combined with multiple area involvement, Glasgow Coma Scale score and age.

Identification of fukinolic acid from Cimicifuga heracleifolia and its derivatives as novel antiviral compounds against enterovirus A71 infection

Human enterovirus 71 (EV-A71) infections cause a wide array of diseases ranging from diarrhoea and rashes to hand-foot-and-mouth disease and, in rare cases, severe neurological disorders. No specific antiviral drug therapy is currently available. Extracts from 75 Chinese medicinal plants selected for antiviral activity based on the Chinese pharmacopeia and advice from traditional Chinese medicine clinicians were tested for activity against EV-A71. The aqueous extract of the rhizome of Cimicifuga heracleifolia (Sheng Ma) and Arnebia euchroma (Zi Cao) showed potent antiviral activity. The active fractions were isolated by bioassay-guided purification, and identified by a combination of high-resolution mass spectrometry and nuclear magnetic resonance. Fukinolic acid and cimicifugic acid A and J, were identified as active anti-EV-A71 compounds for C. heracleifolia, whereas for A. euchroma, two caffeic acid derivatives were tentatively deduced. Commercially available fukinolic acid analogues such as L-chicoric acid and D-chicoric also showed in vitro micromolar activity against EV-A71 lab-strain and clinical isolates.

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.

Hand-foot-mouth disease and use of steroids, intravenous immunoglobulin, and traditional Chinese herbs in a tertiary hospital in Shantou, China

BACKGROUND

In contrast to the guidelines of World Health Organization (WHO) and United States-Centers for Disease Control and prevention (US-CDC), the Chinese national guidelines recommend the use of steroids, intravenous immunoglobulin (IVIG), or traditional Chinese herbs (TCHs) in hand-foot-mouth disease (HFMD) management. Their use and therapeutic efficacies are, however, unclear. We aimed to describe their use in and the clinical outcomes of hospitalized HFMD cases.

METHODS

A retrospective review of hospital medical records for HFMD cases during 2008-2016 was conducted in a medical school-affiliated tertiary hospital in Shantou, Guangdong, China.

RESULTS

Hospitalized children with the discharge diagnosis of HFMD (n = 3778), comprising mild (58.4%), severe (41.5%), and very severe (0.1%) cases, were enrolled in the study. Steroids, IVIG, and antiviral TCH Lan-Qin were respectively prescribed in 60.5, 37.1, and 71.0% of cases. Most cases (99.8%) recovered and six died. Recovery rate was lower with the use of IVIG and higher with Lan-Qin (alone or in combination with steroid) in the mild cases (Ps < 0.05). Longer hospital stay was observed with steroid/IVIG with or without Lan-Qin in the severe cases (Ps < 0.05).

CONCLUSIONS

This nine-year retrospective review shows 1) an increase in the incidence of HFMD as well as the use of steroids, IVIG, and TCH over time, 2) no significant advantage of using steroids and IVIG, either alone or in combination, in the management of mild HFMD cases, and 3) a higher recovery rate in mild HFMD cases with the use of antiviral TCH (Lan-Qin). Our findings need verification in a larger prospect study with cases from hospitals in other regions of China. Lan-Qin efficacy should be evaluated in randomized trials. Meanwhile, caution should be exercised in the extensive use of steroids and IVIG in HFMD management.

Circulating Salivary miRNA hsa-miR-221 as Clinically Validated Diagnostic Marker for Hand, Foot, and Mouth Disease in Pediatric Patients

Enhancements in the diagnostic capabilities using host biomarkers are currently much needed where sensitivity and specificity issues plague the diagnosis of Hand, Foot and Mouth Disease (HFMD) in pediatrics clinical samples. We investigated miRNome profiles of HFMD saliva samples against healthy children and developed miRNA-based diagnosis models. Our 6-miRNA scoring model predicted HFMD with an overall accuracy of 85.11% in the training set and 92.86% in the blinded test set of Singapore cohort. Blinded evaluation of the model in Taiwan HFMD cases resulted in 77.08% accuracy with the 6-miRNA model and 68.75% with the 4-miRNA model. The strongest predictor of HFMD in all of the panels, hsa-miR-221 was found to be consistently and significantly downregulated in all of our HFMD cohorts. This is the first study to prove that HFMD infection could be diagnosed by circulating miRNAs in patient's saliva. Moreover, this study also serves as a stepping stone towards the future development of other infectious disease diagnosis workflows using novel biomarkers.

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Targeted salivary miRNome profiling was conducted between Hand Foot and Mouth disease patients and healthy individuals.

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HFMD diagnosis models were established with training data from Singapore HFMD cohort using the support vector machine.

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The models were also validated blindly using the testing data from Singapore HFMD cohort and the entire Taiwan HFMD cohort.

Using saliva as the medium for diagnosis of human diseases has been a long dream for doctors and patients. In this research article, we developed a rapid test for detecting hand foot and mouth disease using molecules known as miRNA in saliva. We created a mathematical model to detect a specific pattern of miRNA response of the HFMD infection to identify HFMD infected patients. Our model can accurately distinguish HFMD patients from the healthy person by 92.86% in the blinded testing set of Singapore HFMD cohort.

A flavonoid compound library screen revealed potent antiviral activity of plant-derived flavonoids on human enterovirus A71 replication

Hand Foot Mouth Disease (HFMD), resulting from human enterovirus A71 (HEVA71) infection can cause severe neurological complications leading to fatality in young children. Currently, there is no approved antiviral for therapeutic treatment against HEVA71 infection. In this study, a 500-compound flavonoid library was screened to identify potential inhibitors of HEVA71 using high-throughput immunofluorescence-based phenotypic screening method. Two lead flavonoid compounds, ST077124 and ST024734 at the non-cytotoxic concentration of 50 μM were found to be effective antivirals that inhibited replication of HEVA71, reducing infectious viral titers by 3.5 log₁₀ PFU/ml and 2.5 log₁₀ PFU/ml respectively. Our study revealed that ST077124 is a specific antiviral compound that inhibits human enteroviruses while ST024734 exhibited antiviral activity against human enteroviruses as well as dengue virus type-2. We also identified that both compounds affected the viral RNA transcription and translation machinery of HEVA71 but did not interfere with the viral internal ribosomal entry site (IRES) activity. Hence, our findings strongly suggest that ST077124 and ST024734 are effective antiviral compounds of minimal cytotoxicity and could serve as promising therapeutic agents against HEVA71 infection.

Hsc70 regulates the IRES activity and serves as an antiviral target of enterovirus A71 infection

Enterovirus A71 (EV-A71) is a small positive-stranded RNA virus that causes human hand, foot and mouth disease (HFMD) and fatal neurological disorders in some cases without effective treatment. Here we show that heat shock cognate protein 70 (Hsc70), a molecular chaperone, displays pivotal role in viral infections. Knockdown of Hsc70 significantly suppresses viral replication evidenced by reducing not only the level of both viral replication intermediates (negative stranded RNA) and viral genomic RNA (positive stranded RNA), but also the level of viral protein expression; whereas ectopic expression of Hsc70 markedly promotes viral replication. Interestingly, depletion of Hsc70 decreases the IRES activity of EV-A71, and the ectopic expression of Hsc70 enhances the IRES activity accordingly. Further study shows that Hsc70 binds viral genomic RNA but does not directly interact with IRES. Moreover, we reveal that Hsc70 interacts with 2A protease and promotes eIF4G cleavage. More importantly, Hsc70 inhibitor Ver-155008 significantly protects cytopathic effects from EV-A71 infection and inhibits both IRES activity and viral reproduction in a dose-dependent manner. The cell viability assay shows that the IC50 and CC50 are 2.01 μM and 47.67 μM, respectively. These results demonstrate not only an important mechanism of Hsc70 in facilitating EV-A71 replication, but also a target for antiviral drug development.

Antiviral effects of Retro-2cycl and Retro-2.1 against Enterovirus 71 in vitro and in vivo

Enterovirus 71 (EV71) is one of the causative pathogens of hand, foot and mouth disease (HFMD), especially the form associated with fatal neurological disorders. Sustained outbreaks of EV71 infections remain a serious health threat worldwide. However, no antiviral agent against EV71 for clinical therapy has been approved. Retro-2^cycl and Retro-2.1 are inhibitors of several pathogens specifically targeting the intracellular vesicle transport, which also participates in the EV71 lifecycle processes including progeny virus release. Here, we reported that Retro-2^cycl and Retro-2.1, respectively, could inhibit EV71 infection with 50% effective concentrations of 12.56 μM and 0.05 μM in a cytopathic effect inhibition assay and showed relatively low cytotoxicity with 50% cytotoxicity concentrations of more than 500 μM and 267.80 μM. Preliminary mechanism studies revealed that Retro-2^cycl and Retro-2.1 did not inhibit EV71 protein synthesis or RNA replication but could block progeny EV71 release specifically. Furthermore, administration of Retro-2^cycl at the dose of 10 mg/kg significantly protected 90% of newborn mice from lethal EV71 challenge. Consequently, our results for the first time identified Retro-2^cycl and Retro-2.1 as effective inhibitors of EV71 as well as lead compounds, which would contribute to anti-EV71 drug development. We also identified progeny virus release and the intracellular vesicle transport as antiviral targets for EV71.

Synonymous codon usage analysis of hand, foot and mouth disease viruses: A comparative study on coxsackievirus A6, A10, A16, and enterovirus 71 from 2008 to 2015

Enterovirus 71 (EV71) and coxsackievirus A16 (CVA16) have been considered major pathogens of hand, foot and mouth disease (HFMD) throughout the world for decades. In recent years, coxsackievirus A6 (CVA6) and coxsackievirus A10 (CVA10) have raised attention as two other serious pathogens of HFMD. The present study focused on the synonymous codon usage of four viruses isolated from 2008 to 2015, with particular attention on P1 (encoding capsid proteins) and P2-P3 regions (both encoding non-structural proteins) in the genomic RNA. Relative synonymous codon usage, effective number of codons, neutrality and correspondence were analyzed. The results indicated that these viruses prefer A/T at the third position in codons rather than G/C. The most frequent codons of 4 essential and 2 semi-essential amino acids, as well as a key amino acid of metabolic junctions (Glu) used in the four viruses are also the most frequently used in humans. Effective number of codons (ENC) values indicated weak codon usage bias in all the viruses. Relatively, the force of mutation pressure in the P1 region was found to be stronger than that in the P2-P3 region, and this force in the P1 region of CVA6 and EV71 was stronger than that of CVA10 and A16. The neutrality analysis results implied that mutation pressure plays a minor role in shaping codon bias of these viruses. Correspondence analysis indicated that the codon usage of EV71 strains varied much more than that of other viruses. In conclusion, the present study provides novel and comparative insight into the evolution of HFMD pathogens at the codon level.

Enterovirus 71-induced has-miR-21 contributes to evasion of host immune system by targeting MyD88 and IRAK1

Enterovirus71(EV71), the etiological agent of hand-foot-and-mouth disease, has increasingly become a public health challenge around the world. Type I interferons (IFNs) are an important family of cytokines that regulate innate and adaptive immune responses to pathogens.These pathways are tightly regulated by the host to prevent an inappropriate cellular response, but viruses can modulate these pathways to proliferate and spread. In this study, we demonstrated that EV71 evades the immune surveillance system to proliferate by activating microRNA-21. We demonstrated that EV71 infection upregulates miR-21, which in turn suppresses EV71-triggered type I IFN production, thus promoting EV71 replication. Furthermore, we demonstrated that miR-21 targets the myeloid differentiation factor 88(MyD88) and interleukin-1 receptor-associated kinase 1(IRAK1), which are involved in EV71-induced type I IFN production.

Antiviral activities of Schizonepeta tenuifolia Briq. against enterovirus 71 in vitro and in vivo

No effective drug is currently available for treatment of enterovirus 71 (EV71) infection. Schizonepeta tenuifolia Briq. (ST) has been used as a herbal constituent of traditional Chinese medicine. We studied whether the aqueous extract of Schizonepeta tenuifolia Briq (STE) has antiviral activity. STE inhibited replication of EV71, as evident by its ability to diminish plaque formation and cytopathic effect induced by EV71, and to inhibit the synthesis of viral RNA and protein. Moreover, daily single-dose STE treatment significantly improved the survival of EV71-infected mice, and ameliorated the symptoms. Mechanistically, STE exerts multiple effects on enteroviral infection. Treatment with STE reduced viral attachment and entry; the cleavage of eukaryotic translation initiation factor 4 G (eIF4G) by EV71 protease, 2A^pro; virus-induced reactive oxygen species (ROS) formation; and relocation of heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) from the nucleus to the cytoplasm. It was accompanied by a decline in EV71-associated hyperphosphorylation of p38 kinase and EPS15. It is plausible that STE may inhibit ROS-induced p38 kinase activation, and subsequent hnRNP A1 relocation and EPS15-mediated membrane trafficking in infected cells. These findings suggest that STE possesses anti-EV71 activities, and may serve as health food or candidate antiviral drug for protection against EV71.

Crystal structure of 2C helicase from enterovirus 71

Enterovirus 71 (EV71) is the major pathogen responsible for outbreaks of hand, foot, and mouth disease. EV71 nonstructural protein 2C participates in many critical events throughout the virus life cycle; however, its precise role is not fully understood. Lack of a high-resolution structure made it difficult to elucidate 2C activity and prevented inhibitor development. We report the 2.5 Å-resolution crystal structure of the soluble part of EV71 2C, containing an adenosine triphosphatase (ATPase) domain, a cysteine-rich zinc finger with an unusual fold, and a carboxyl-terminal helical domain. Unlike other AAA+ ATPases, EV71 2C undergoes a carboxyl terminus-mediated self-oligomerization, which is dependent on a specific interaction between the carboxyl-terminal helix of one monomer and a deep pocket formed between the ATPase and the zinc finger domains of the neighboring monomer. The carboxyl terminus-mediated self-oligomerization is fundamental to 2C ATPase activity and EV71 replication. Our findings suggest a strategy for inhibition of enterovirus replication by disruption of the self-oligomerization interface of 2C.

Transcriptome analysis reveals dynamic changes in coxsackievirus A16 infected HEK 293T cells

BACKGROUND

Coxsackievirus A16 (CVA16) and enterovirus 71 (EV71) are two of the major causes of hand, foot and mouth disease (HFMD) world-wide. Although many studies have focused on infection and pathogenic mechanisms, the transcriptome profile of the host cell upon CVA16 infection is still largely unknown.

RESULTS

In this study, we compared the mRNA and miRNA expression profiles of human embryonic kidney 293T cells infected and non-infected with CVA16. We highlighted that the transcription of SCARB2, a cellular receptor for both CVA16 and EV71, was up-regulated by nearly 10-fold in infected cells compared to non-infected cells. The up-regulation of SCARB2 transcription induced by CVA16 may increase the possibility of subsequent infection of CVA16/EV71, resulting in the co-infection with two viruses in a single cell. This explanation would partly account for the co-circulation and genetic recombination of a great number of EV71 and CVA16 viruses. Based on correlation analysis of miRNAs and genes, we speculated that the high expression of SCARB2 is modulated by down-regulation of miRNA has-miR-3605-5p. At the same time, we found that differentially expressed miRNA target genes were mainly reflected in the extracellular membrane (ECM)-receptor interaction and circadian rhythm pathways, which may be related to clinical symptoms of patients infected with CVA16, such as aphthous ulcers, cough, myocarditis, somnolence and potentially meningoencephalitis. The miRNAs hsa-miR-149-3p and hsa-miR-5001-5p may result in up-regulation of genes in these morbigenous pathways related to CVA16 and further cause clinical symptoms.

CONCLUSIONS

The present study elucidated the changes in 293T cells upon CVA16 infection at transcriptome level, containing highly up-regulated SCARB2 and genes in ECM-receptor interaction and circadian rhythm pathways, and key miRNAs in gene expression regulation. These results provided novel insight into the pathogenesis of HFMD induced by CVA16 infection.

Correlation of symptomatic enterovirus infection and later risk of allergic diseases via a population-based cohort study

Infants who are exposed to the rhinovirus or respiratory syncytial virus are at a higher risk of subsequently developing wheezing or asthma. This study aims to determine whether preschoolers with a history of symptomatic enterovirus infection are at an increased risk of developing allergic diseases or not.We used data from the Taiwan National Health Insurance Research Database from 1999 to 2006 for this nationwide population-based cohort study. The subsequent risks for allergic diseases, which included asthma (International Classification of Diseases [ICD]-9: 493.X), allergic rhinitis (AR; ICD-9 CM code 477.X), and atopic dermatitis (AD; ICD-9-CM code 691.X), were compared between herpangina (ICD-9: 074.0) and hand, foot, and mouth disease (HFMD; ICD-9: 074.3) throughout the follow-up period using the Cox proportional hazards model.In this database, 12,016 neonates were born between January 1999 and December 1999. Among them, we further evaluated 8337 subjects; 3267 children infected with either herpangina or HFMD served as the study cohort, and the other 5070 children made up the comparison cohort. Children in the herpangina group had a higher risk of developing AR and AD, with adjusted hazard ratios of 1.15 (1.02-1.30, 95% CI) and 1.38 (1.17-1.63. 95% CI), respectively, while children suffered from HFMD had decreased risks of asthma, with an adjusted hazard ratio of 0.76 (0.63-0.93, 95% CI).Children who previously suffered from herpangina experienced an increased risk of subsequently developing AD and AR. Meanwhile, children who had suffered from HFMD experienced a decrease in the subsequent occurrence of asthma compared to the general population.

Antiviral Probiotics: A New Concept in Medical Sciences

In recent decades, probiotics have shown beneficial effects on animal and human health. Probiotics can protect the host against several health threats, including infectious diseases. Before 1995, researchers believed that the effect of probiotics was only on gut microbiota which can restore the gut flora and thus prevent pathogenic bacteria from triggering gastroenteritis. Recent studies have shown that the immunomodulatory activity is the most important mechanism of action of probiotics. From this information, researchers started to evaluate the effect of some immunobiotics, not only on pathogenic bacteria but also on viruses, including enteric and respiratory viruses. Several studies have confirmed the potential antiviral activity of some probiotics due to the immunomodulatory effect. These studies were conducted on humans (clinical trials) and in animal models. In this chapter, probiotics with antiviral effect against respiratory and enteric viruses will be presented and discussed, as well as their mechanisms of action.

Development of a fluorescence resonance energy transfer-based intracellular assay to identify novel enterovirus 71 antivirals

Enterovirus 71 (EV71) is considered one of the most virulent pathogens in the family Picornaviridae. However, there have been no effective treatments for the severe complications caused by EV71. Development of new drugs against targets that are essential for viral replication often requires screening large collections of compounds, for which a high-throughput screening platform is needed. In this study, a drug-screening platform was developed based on a genetically engineered cell line that displays fluorescence resonance energy transfer (FRET) and shows a real-time and quantifiable impairment of FRET upon EV71 infection. A library of small molecules consisting of 1280 compounds with defined bioactivities was used for screening drugs with anti-EV71 activity; accurate, rapid, and robust results were obtained from this screening procedure. Ten drugs were identified in the primary screening, and their antiviral activities were indicated by dose-dependent elevation of FRET. Among these, AC-93253, mitoxantrone and N-bromoacetamide had not been reported as enterovirus inhibitors, and it was confirmed that they were able to suppress viral yields in a dose-dependent manner. Taken together, these studies demonstrate the feasibility of this FRET-based platform for efficient screening and identification of novel compounds with activity against EV71 infection.

New Findings, Classification and Long-Term Follow-Up Study Based on MRI Characterization of Brainstem Encephalitis Induced by Enterovirus 71

BACKGROUND

To report the diversity of MRI features of brainstem encephalitis (BE) induced by Enterovirus 71. This is supported by implementation and testing of our new classification scheme in order to improve the diagnostic level on this specific disease.

METHODS

Neuroimaging of 91 pediatric patients who got EV71 related BE were hospitalized between March, 2010 to October, 2012, were analyzed retrospectively. All patients underwent pre- and post-contrast MRI scan. Thereafter, 31 patients were randomly called back for follow-up MRI study during December 2013 to August 2014. The MRI signal patterns of BE primary lesion were analyzed and classified according to MR signal alteration at various disease stages. Findings in fatal and non-fatal cases were compared, and according to the MRI scan time point during the course of this disease, the patients' conditions were classified as 1) acute stage, 2) convalescence stage, 3) post mortem stage, and 4) long term follow-up study.

RESULTS

103 patients were identified. 11 patients did not undergo MRI, as they died within 48 hours. One patient died on 14th day without MR imaging. 2 patients had postmortem MRI. Medical records and imaging were reviewed in the 91 patients, aged 4 months to 12 years, and two cadavers who have had MRI scan. At acute stage: the most frequent pattern (40 patients) was foci of prolonged T1 and T2 signal, with (15) or without (25) contrast enhancement. We observed a novel pattern in 4 patients having foci of low signal intensity on T2WI, with contrast enhancement. Another pattern in 10 patients having foci of contrast enhancement without abnormalities in T1WI or T2WI weighted images. Based on 2 cases, the entire medulla and pons had prolonged T1 and T2 signal, and 2 of our postmortem cases demonstrated the same pattern. At convalescence stage, the pattern observed in 4 patients was foci of prolonged T1 and T2 signal without contrast enhancement. Follow-up MR study of 31 cases showed normal in 26 cases, and demonstrated foci of prolonged T1 and T2 signal with hyper-intensity on FLAIR in 3 cases, or of prolonged T1 and T2 signal with hypo-intensity on FLAIR in 2 cases. Most importantly, MR findings of each case were thoroughly investigated and classified according to phases and MRI signal alteration.

CONCLUSIONS

This study has provided enhanced and useful information for the MRI features of BE induced by EV71, apart from common practice established by previous reports. In addition, a classification scheme that summarizes all types of features based on the MRI signal at the four different stages of the disease would be helpful to improve the diagnostic level.

Enterovirus 71 infection and neurological complications

Since the outbreak of the enterovirus 71 (EV71) infection in Malaysia in 1997, large epidemics of EV71 have occurred in the Asia-Pacific region. Many children and infants have died from serious neurological complications during these epidemics, and EV71 infection has become a serious public health problem in these areas. EV71 infection causes hand, foot and mouth disease (HFMD) in children, and usually resolves spontaneously. However, EV71 occasionally involves the central nervous system (CNS), and induces diverse neurological complications such as brainstem encephalitis, aseptic meningitis, and acute flaccid paralysis. Among those complications, brainstem encephalitis is the most critical neurological manifestation because it can cause neurogenic pulmonary hemorrhage/edema leading to death. The characteristic clinical symptoms such as myoclonus and ataxia, cerebrospinal fluid (CSF) pleocytosis, and brainstem lesions on magnetic resonance imaging, in conjunction with the skin rash of HFMD and the isolation of EV71 from a stool, throat-swab, or CSF sample are typical findings indicating CNS involvement of EV71 infection. Treatment with intravenous immunoglobulin and milrinone are recommended in cases with severe neurological complications from EV71 infection, such as brainstem encephalitis. Despite the recent discovery of receptors for EV71 in human cells, such as the scavenger receptor B2 and P-selection glycoprotein ligand 1, it is not known why EV71 infection predominantly involves the brainstem. Recently, 3 companies in China have completed phase III clinical trials of EV71 vaccines. However, the promotion and approval of these vaccines in various countries are problems yet to be resolved.

Seroepidemiology of Human Enterovirus 71 Infection among Children, Cambodia

Enterovirus 71 is reported to have emerged in Cambodia in 2012; at least 54 children with severe encephalitis died during that outbreak. We used serum samples collected during 2000–2011 to show that the virus had been widespread in the country for at least a decade before the 2012 outbreak.

Gene sequencing and variable site analyzing of coding region of two enterovirus A71 isolates with different clinical phenotypes

Currently, it is still controversial that if the pathogenicity of EV-A71 causing severe or mild hand, foot, and mouth disease (HFMD) is associated with viral nucleotide or amino acid sequence(s). In this study, 19 clinical strains were detected in samples from diagnosed patients of EV-A71-caused HFMD with mild or severe symptoms. Then, VP1-2A fragment sequences of 19 EV-A71 isolates were determined, the phylogenetic analysis, based on VP1 sequences of 19 EV-A71 stains in this study and which of 62 EV-A71 strains with different clinical phenotypes reported before, were carried out. Our results showed that no difference in the genotype and evolution distribution was observed among the EV-A71 strains mentioned above. Furthermore, two EV-A71 isolates, which with much close evolutionary relationship but different clinical manifestations, were purified by plaque assay, the complete genome sequencing was done, and deduced amino acid sequence analysis of 11 proteins coded by EV-A71 was carried out. Eight variable amino acid sites were found and further verified with those of 62 strains reported before. Our study provides further evidence that the potential pathogenicity of EV-A71 causing severe or mild HFMD seems not to be associated with viral genotype and even the amino acid substitution.

Molecular epidemiology of enterovirus and parechovirus infections according to patient age over a 4-year period in Spain

The epidemiology and clinical association of enterovirus (EV) and parechovirus (HPeV) infections, as well as the type-distribution-according-to-age, were determined during a 4-year study period in Spain. During 2010-2013, a total of 21,832 clinical samples were screened for EV and the detection frequency was 6.5% (1,430). Of the total EV-negative samples, only 1,873 samples from 2011 to 2013 were available for HPeV testing. HPeV was detected in 42 (2%) of them. Positive samples were genotyped using PCR and sequencing. EV infections occurred in all age groups of patients: neonates (17%), children 28 days to 2 years (29%), children 2-14 years (40%), and adults (14%). Thirty-four different EV types were identified. HPeV infections were detected exclusively in infants <8 m (70% neonates, P < 0.05). All but one HPeV were HPeV-3. Differences in type frequency detection were found according to age and clinical manifestation. Coxsackievirus (CV)-B4 (61%), CV-B5 (83%), and HPeV-3 (64%) were more frequent in neonates than in older patients (P < 0.05). Echovirus (E)-3 (60%), E-18 (47%), E-25 (62%), CV-A6 (61%), CV-A16 (72%), and EV-71 (75%) were mainly detected in children 28 days to 2 years (P < 0.05), whereas, E-6 (79%), E-20 (88%), and E-30 (85%) were predominant in children >2 years and adults (P < 0.05). Clinically, meningitis was associated with EV (P < 0.01) whereas, encephalitis was more frequent in HPeV-infected patients. CV-B types were associated with myocarditis (90%; P < 0.05) and EV species A with hand-foot-mouth-disease/atypical exanthema (88%; P < 0.05). J. Med. Virol. 89:435-442, 2017. © 2016 Wiley Periodicals, Inc.

Antiviral activity of Lactobacillus reuteri Protectis against Coxsackievirus A and Enterovirus 71 infection in human skeletal muscle and colon cell lines

Background

Recurrence of hand, foot and mouth disease (HFMD) pandemics continues to threaten public health. Despite increasing awareness and efforts, effective vaccine and drug treatment have yet to be available. Probiotics have gained recognition in the field of healthcare worldwide, and have been extensively prescribed to babies and young children to relieve gastrointestinal (GI) disturbances and diseases, associated or not with microbial infections. Since the faecal-oral axis represents the major route of HFMD transmission, transient persistence of probiotic bacteria in the GI tract may confer some protection against HFMD and limit transmission among children.

Methods

In this work, the antiviral activity of two commercially available probiotics, namely Lactobacillus reuteri Protectis (L. reuteri Protectis) and Lactobacillus casei Shirota (L. casei Shirota), was assayed against Coxsackieviruses and Enterovirus 71 (EV71), the main agents responsible for HFMD. In vitro infection set-ups using human skeletal muscle and colon cell lines were designed to assess the antiviral effect of the probiotic bacteria during entry and post-entry steps of the infection cycle.

Results

Our findings indicate that L. reuteri Protectis displays a significant dose-dependent antiviral activity against Coxsackievirus type A (CA) strain 6 (CA6), CA16 and EV71, but not against Coxsackievirus type B strain 2. Our data support that the antiviral effect is likely achieved through direct physical interaction between bacteria and virus particles, which impairs virus entry into its mammalian host cell. In contrast, no significant antiviral effect was observed with L. casei Shirota.

Conclusions

Should the antiviral activity of L. reuteri Protectis observed in vitro be translated in vivo, such probiotics-based therapeutic approach may have the potential to address the urgent need for a safe and effective means to protect against HFMD and limit its transmission among children.

Interleukin-27 as a Novel Biomarker for Early Cardiopulmonary Failure in Enterovirus 71-Infected Children with Central Nervous System Involvement

Enterovirus 71 (EV71) is a major pathogen for severe hand, foot, and mouth disease (HFMD), which leads to severe neurological complications and has high morbidity and mortality. Reliable biomarker for the prediction of deterioration in EV71-infected children with central nervous system (CNS) involvement may reduce the cardiopulmonary failure and mortality. Here, we found that serum IL-27 levels were significantly higher in stage III EV71-infected HFMD patients with early cardiopulmonary failure and strong correlation with CRP levels. IL27p28 polymorphisms (rs153109, rs17855750, and rs181206) did not influence IL-27 production, and these three SNPs were not associated with EV71 infection risk and clinical stage. IL-27 can be used as an prediction indicator for early cardiopulmonary failure in EV71-infected children with CNS involvement.

Enterovirus 71: a whole virion inactivated enterovirus 71 vaccine

INTRODUCTION

Enterovirus A71 (EV71) is the predominant causative agent of hand, foot, and mouth disease (HFMD), which is often associated with severe cases and even deaths. EV71-associated epidemics have emerged as a serious threat to public health, particularly in the Asia-Pacific region.

AREAS COVERED

We searched PubMed using the terms 'enterovirus 71', 'hand, foot, and mouth disease', and 'vaccine', with no date or language restrictions for all publications before April 27, 2016. Among various vaccine candidates, the alum-adjuvant inactivated EV71 vaccines are most promising. Three alum-adjuvant inactivated EV71 vaccines developed by mainland China showed high efficacy, good immunogenicity persistence and acceptable safety profiles in clinical trials. Recently, two of these EV71 vaccines have been approved for marketing in China and the other one is undergoing the review process of licensure. In this manuscript, we summarized previous study results as well as discussed the regulatory affairs and post-market surveillances issues. Expert commentary: The marketing of EV71 vaccines is a milestone in the controlling of HFMD. International clinical trials are needed to further assess the efficacy and cross-immunogenicity. Establishing a sensitive pathogen monitoring system would be essential to monitor the variation of genotypes and control HFMD epidemics.

Characterization of Coxsackievirus A6- and Enterovirus 71-Associated Hand Foot and Mouth Disease in Beijing, China, from 2013 to 2015

BACKGROUND

Etiology surveillance of Hand Foot and Mouth disease (HFMD) in Beijing showed that Coxsackievirus A6 (CVA6) became the major pathogen of HFMD in 2013 and 2015. In order to understand the epidemiological characteristics and clinical manifestations of CVA6-associated HFMD, a comparison study among CVA6-, EV71- (Enterovirus 71), and CVA16- (Coxsackievirus A16) associated HFMD was performed.

METHODS

Epidemiological characteristics and clinical manifestations among CVA6-, EV71- and CVA16-associated mild or severe cases were compared from 2013 to 2015. VP1 gene of CVA6 and EV71 from mild cases, severe cases were sequenced, aligned, and compared with strains from 2009 to 2015 in Beijing and strains available in GenBank. Phylogenetic tree was constructed by neighbor-joining method.

RESULTS

CVA6 became the predominant causative agent of HFMD and accounted for 35.4 and 36.9% of total positive cases in 2013 and 2015, respectively. From 2013 to 2015, a total of 305 severe cases and 7 fatal cases were reported. CVA6 and EV71 were responsible for 57.5% of the severe cases. Five out six samples from fatal cases were identified as EV71. High fever, onychomadesis, and decrustation were the typical symptoms of CVA6-associated mild HFMD. CVA6-associated severe cases were characterized by high fever with shorter duration and twitch compared with EV71-associated severe cases which were characterized by poor mental condition, abnormal pupil, and vomiting. Poor mental condition, lung wet rales, abnormal pupil, and tachycardia were the most common clinical features of fatal cases. The percentage of lymphocyte in CVA6-associated cases was significantly lower than that of EV71. High percentage of lymphocyte and low percentage of neutrophils were the typical characteristics of fatal cases. VP1 sequences between CVA6- or EV71-associated mild and severe cases were highly homologous.

CONCLUSION

CVA6 became one of the major pathogens of HFMD in 2013 and 2015 in Beijing. Epidemiological characteristics, clinical manifestations of CVA6-, EV71- and CVA16-associated cases in this study enriched the definition of HFMD caused by different pathogens and shed light to accurate diagnosis, appropriate treatment and effective prevention of HFMD.

Milrinone in Enterovirus 71 Brain Stem Encephalitis

Enterovirus 71 (EV71) was implicated in a widespread outbreak of hand-foot-and-mouth disease (HFMD) across the Asia Pacific area since 1997 and has also been reported sporadically in patients with brain stem encephalitis. Neurogenic shock with pulmonary edema (PE) is a fatal complication of EV71 infection. Among inotropic agents, milrinone is selected as a therapeutic agent for EV71- induced PE due to its immunopathogenesis. Milrinone is a type III phosphodiesterase inhibitor that has both inotropic and vasodilator effects. Its clinical efficacy has been shown by modulating inflammation, reducing sympathetic over-activity, and improving survival in patients with EV71-associated PE. Milrinone exhibits immunoregulatory and anti-inflammatory effects in the management of systemic inflammatory responses in severe EV71 infection.

MRI signal intensity differentiation of brainstem encephalitis induced by Enterovirus 71: a classification approach for acute and convalescence stages

Background

The objective of this study is to assess standardized histograms of signal intensities of T1 signal and T2 signal on sagittal view without enhancement during (1) acute stage, and (2) convalescence stage of pediatric patients with Enterovirus 71 related brainstem encephalitis (BE), and with respect to (3) healthy normal.

Methods

Our subjects were hospitalized between March 2010 and October 2012, and underwent pre- and post-contrast MRI studies. The research question to be answered is whether the comparison of the MRI image intensity histograms and relevant statistical quantification can add new knowledge to the diagnosis of BE patients. So, both 25 cases in acute stage with prolonged T1 and T2 signal, without enhancement, and 13 cases in convalescence stage were introduced. In additional, a healthy group with 25 cases was recruited for comparison.

Results

MRI signal intensity histogram changes of the lesions were compared at the acute and convalescence stages of the disease. Our preliminary results suggest that standardized histograms of signal intensities and their statistical properties are able to provide diagnostic information for the clinical assessment of the disease. Different stages pertaining to the histogram plots comparison showed that overall T1 signal intensity values increase as we traverse from the acute stage to the convalescence stage. And then for the healthy subjects, the T2 signal intensity values changed their magnitudes in a reverse direction. However, exceptions of this can happen in four cases where the primary lesions occurred in the brainstem that developed encephalomalacia resulting in a lower signal in T1WI and higher signal in T2WI. Statistical analysis revealed there was significant difference of T1 signal intensity among the three groups; and also, the T2 signal intensity was lower than other two groups.

Conclusions

Standardized histogram of T1 and T2 intensity provide valuable and useful information for disease diagnosis and evaluation, which can potentially help medical doctors to save the lives of children.

Electronic supplementary material

The online version of this article (doi:10.1186/s12938-016-0136-7) contains supplementary material, which is available to authorized users.

Validation and evaluation of serological correlates of protection for inactivated enterovirus 71 vaccine in children aged 6-35 months

BACKGROUND

A primary goal of this study was to establish the serological mechanistic correlate of protection (mCoP) for an inactivated Enterovirus 71 (EV71) vaccine.

METHODS

We used the Prentice criterion framework and scaled logit model to explore the relationship between the neutralizing antibody (NTAb) and EV71-associated disease, and to build a protection curve for estimating the efficacy of EV71 vaccine. Data of NTAb at day 56 post-vaccination and the occurrence of EV71-associated disease during a 12-month follow-up period were collected from a phase 3 efficacy trial of EV71 vaccine in this study.

RESULTS

NTAb at day 56 post-vaccination in participants met the Prentice criterion framework. According to the protection curve, the antibody levels of 14.7, 27.8, 55.7, 129.0 and 459.4 (U/mL) were associated with 50%, 60%, 70%, 80% and 90% clinical protection rate, respectively. Vaccine efficacy predicted by the model was 81.5%, which was very similar to the actual vaccine efficacy of 80.4% (95% CI, 58.2, 90.8) observed in the phase 3 trial.

CONCLUSIONS

NTAb titers post-vaccination can be validated as mCoP for evaluating the efficacy of an inactivated enterovirus 71 vaccine, with a titers of 14.7 (U/ml) as a surrogate associated with the protection of 50% against EV71-associated disease.

Global gene expression analysis of peripheral blood mononuclear cells in rhesus monkey infants with CA16 infection-induced HFMD

Coxsackievirus A16 (CA16) is a dominant pathogen that results in hand, foot, and mouth disease and causes outbreaks worldwide, particularly in the Asia-Pacific region. However, the underlying molecular mechanisms remain unclear. Our previous study has demonstrated that the basic CA16 pathogenic process was successfully mimicked in rhesus monkey infant. The present study focused on the global gene expression changes in peripheral blood mononuclear cells of rhesus monkey infants with hand, foot, and mouth disease induced by CA16 infection at different time points. Genome-wide expression analysis was performed with Agilent whole-genome microarrays and established bioinformatics tools. Nine hundred and forty-eight significant differentially expressed genes that were associated with 5 gene ontology categories, including cell communication, cell cycle, immune system process, regulation of transcription and metabolic process were identified. Subsequently, the mapping of genes related to the immune system process by PANTHER pathway analysis revealed the predominance of inflammation mediated by chemokine and cytokine signaling pathways and the interleukin signaling pathway. Ultimately, co-expressed genes and their networks were analyzed. The results revealed the gene expression profile of the immune system in response to CA16 in rhesus monkey infants and suggested that such an immune response was generated as a result of the positive mobilization of the immune system. This initial microarray study will provide insights into the molecular mechanism of CA16 infection and will facilitate the identification of biomarkers for the evaluation of vaccines against this virus.

Norepinephrine and Epinephrine Enhanced the Infectivity of Enterovirus 71

Background

Enterovirus 71 (EV71) infections may be associated with neurological complications, including brainstem encephalitis (BE). Severe EV71 BE may be complicated with autonomic nervous system (ANS) dysregulation and/or pulmonary edema (PE). ANS dysregulation is related to the overactivation of the sympathetic nervous system, which results from catecholamine release.

Objective

The aims of this study were to explore the effects of catecholamines on severe EV71 infection and to investigate the changes in the percentages of EV71-infected cells, virus titer, and cytokine production on the involvement of catecholamines.

Study Design

Plasma levels of norepinephrine (NE) and epinephrine (EP) in EV71-infected patients were measured using an enzyme-linked immunoassay. The expression of adrenergic receptors (ADRs) on RD, A549, SK-N-SH, THP-1, Jurkat and human peripheral blood mononuclear cells (hPBMCs) were detected using flow cytometry. The percentages of EV71-infected cells, virus titer, and cytokine production were investigated after treatment with NE and EP.

Results

The plasma levels of NE and EP were significantly higher in EV71-infected patients with ANS dysregulation and PE than in controls. Both α_1A- and β₂-ADRs were expressed on A549, RD, SK-N-SH, HL-60, THP-1, Jurkat cells and hPBMCs. NE treatment elevated the percentages of EV71-infected cells to 62.9% and 22.7% in THP-1 and Jurkat cells, respectively. Via treatment with EP, the percentages of EV71-infected cells were increased to 64.6% and 26.9% in THP-1 and Jurkat cells. The percentage of EV71-infected cells increased upon NE or EP treatment while the α- and β-blockers reduced the percentages of EV71-infected cells with NE or EP treatment. At least two-fold increase in virus titer was observed in EV71-infected A549, SK-N-SH and hPBMCs after treatment with NE or EP. IL-6 production was enhanced in EV71-infected hPBMCs at a concentration of 10² pg/mL NE.

Conclusion

The plasma levels of NE and EP elevated in EV71-infected patients with ANS dysregulation and PE. Both NE and EP enhanced the percentages of infected cells and virus titers in EV71 infection in vitro. NE and EP may play a role in the pathogenesis of EV71 BE complicated with ANS dysregulation and PE.

Magnesium lithospermate B and rosmarinic acid, two compounds present in Salvia miltiorrhiza, have potent antiviral activity against enterovirus 71 infections

The aim of this study was to identify the active ingredients responsible for the anti-EV71 activity produced by Salvia miltiorrhiza extracts. A pGS-EV71 IRES-based bicistronic reporter assay platform was used for rapid analysis of compounds that could specifically inhibit EV71 viral IRES-mediated translation. The analysis identified 2 caffeic acid derivatives, magnesium lithospermate B (MLB) and rosmarinic acid (RA), which suppressed EV71 IRES-mediated translation at concentrations of 30μg/ml. We also found that MLB and RA inhibited EV71 infection when they were added to RD cells during the viral absorption stage. MLB had a low IC50 value of 0.09mM and a high TI value of 10.52. In contrast, RA had an IC50 value of 0.50mM with a TI value of 2.97. MLB and RA (100µg/ml) also reduced EV71 viral particle production and significantly decreased VP1 protein production. We propose that these two derivatives inhibit EV71 viral entry into cells and viral IRES activity, thereby reducing viral particle production and viral RNA expression and blocking viral VP1 protein translation. This study provides useful information for the development of anti-EV71 assays and reagents by demonstrating a convenient EV71 IRES-based bicistronic assay platform to screen for anti-EV71 IRES activity, and also reports 2 compounds, MLB and RA, which are responsible for the anti-EV71 activity of S. miltiorrhiza.

Both ERK1 and ERK2 are required for enterovirus 71 (EV71) efficient replication

It has been demonstrated that MEK1, one of the two MEK isoforms in Raf-MEK-ERK1/2 pathway, is essential for successful EV71 propagation. However, the distinct function of ERK1 and ERK2 isoforms, the downstream kinases of MEKs, remains unclear in EV71 replication. In this study, specific ERK siRNAs and selective inhibitor U0126 were applied. Silencing specific ERK did not significantly impact on the EV71-caused biphasic activation of the other ERK isoform, suggesting the EV71-induced activations of ERK1 and ERK2 were non-discriminative and independent to one another. Knockdown of either ERK1 or ERK2 markedly impaired progeny EV71 propagation (both by more than 90%), progeny viral RNA amplification (either by about 30% to 40%) and protein synthesis (both by around 70%), indicating both ERK1 and ERK2 were critical and not interchangeable to EV71 propagation. Moreover, suppression of EV71 replication by inhibiting both early and late phases of ERK1/2 activation showed no significant difference from that of only blocking the late phase, supporting the late phase activation was more importantly responsible for EV71 life cycle. Taken together, this study for the first time identified both ERK1 and ERK2 were required for EV71 efficient replication and further verified the important role of MEK1-ERK1/2 in EV71 replication.

The clinical correlation of regulatory T cells and cyclic adenosine monophosphate in enterovirus 71 infection

Background

Brainstem encephalitis (BE) and pulmonary edema (PE) are notable complications of enterovirus 71 (EV71) infection.

Objective

This study investigated the immunoregulatory characterizations of EV71 neurological complications by disease severity and milrinone treatment.

Study Design

Patients <18 years with virologically confirmed EV71 infections were enrolled and divided into 2 groups: the hand, foot, and mouth disease (HFMD) or BE group, and the autonomic nervous system (ANS) dysregulation or PE group. Cytokine and cyclic adenosine monophosphate (cAMP) levels, and the regulatory T cell (Tregs) profiles of the patients were determined.

Results

Patients with ANS dysregulation or PE exhibited significantly low frequency of CD4⁺CD25⁺Foxp3⁺ and CD4⁺Foxp3⁺ T cells compared with patients with HFMD or BE. The expression frequency of CD4⁻CD8⁻ was also significantly decreased in patients with ANS dysregulation or PE. Among patients with ANS dysregulation or PE, the expression frequency of CD4⁺Foxp3⁺ increased markedly after milrinone treatment, and was associated with reduction of plasma levels IL-6, IL-8 and IL-10. Plasma concentrations of cAMP were significantly decreased in patients with ANS dysregulation or PE compared with patients with HFMD or BE; however, cAMP levels increased after milrinone treatment.

Conclusions

These findings suggested decreased different regulatory T populations and cAMP expression correlate with increased EV71 disease severity. Improved outcome after milrinone treatment may associate with increased regulatory T populations, cAMP expression and modulation of cytokines levels.