Neurodevelopment and cognition in children after enterovirus 71 infection

Antivirals against enteroviruses: a critical review from a public-health perspective

The enteroviruses (EVs) of the Picornaviridae family are the most common viral pathogens known. Most EV infections are mild and self-limiting but manifestations can be severe in children and immunodeficient individuals. Antiviral development is actively pursued to benefit these high-risk patients and, given the alarming problem of antimicrobial drug resistance, antiviral drug resistance is a public-health concern. Picornavirus antivirals can be used off-label or as part of outbreak control measures. They may be used in the final stages of poliovirus eradication and to mitigate EV-A71 outbreaks. We review the potential emergence of drug-resistant strains and their impact on EV transmission and endemic circulation. We include non-picornavirus antivirals that inhibit EV replication, for example, ribavirin, a treatment for infection with HCV, and amantadine, a treatment for influenza A. They may have spurred resistance emergence in HCV or influenza A patients who are unknowingly coinfected with EV. The public-health challenge is always to find a balance between individual benefit and the long-term health of the larger population.

miR-146a and miR-370 coordinate enterovirus 71-induced cell apoptosis through targeting SOS1 and GADD45β

Enterovirus 71 (EV71) is an emerging life-threatening pathogen particularly in the Asia-Pacific region. The major pathogenic feature in EV71-infected cells is apoptosis. However, which molecular mechanism mainly contributes to EV71-induced apoptosis is not investigated thoroughly. MicroRNAs (MiRNAs), the newly discovered molecules, govern a wide range of biological functions through post-transcriptional regulation including viral pathogenesis. Whether miRNAs and messenger RNAs (mRNAs) coordinate to trigger host cell apoptosis in EV71 infection was investigated in this study. We conducted an apoptosis-oriented approach using both mRNA and miRNA profiling and bioinformatic analysis. We identified two major apoptosis-associated signalling pathways, Bcl2 antagonist of cell death (BAD) phosphorylation and p53-dependent apoptosis pathways, in which Son of sevenless homolog 1 (SOS1) and Growth arrest and DNA damage-inducible protein 45β (GADD45β) were predicted as targets of miR-146a and miR-370 respectively. Luciferase reporter assays and Western blots demonstrated the negative regulation between miR-146a and SOS1 and between miR-370 and GADD45β. Silencing of miR-146a restored SOS1 expression and partially attenuated EV71 infection-induced apoptosis. Conversely, ectopic expression of miR-370 decreased virus infection-induced GADD45β expression and also diminished apoptosis. Finally, the transfection of antagomiR-146a and miR-370 contributed to attenuating EV71 infection-induced apoptosis. Herein we clearly demonstrate that EV71-induced cell apoptosis is partly governed by altered miRNAs.

Update on hand-foot-and-mouth disease

Hand-foot-and-mouth disease is a viral exanthem caused, primarily by Coxsackie A16 and enterovirus 71 with typical clinical features of fever, painful papules and blisters over the extremities and genitalia and an enanthem involving ulceration of the mouth, palate, and pharynx. Other enteroviruses have recently been noted to cause severe neurologic illness and paralysis (enterovirus 68) with variable cutaneous features. A recent outbreak of Coxsackie A6 infection has been seen worldwide with cases reported in the United States, Japan, Southeast Asia, and Europe. These cases have caused extensive cutaneous disease variants, some of which are not previously recognized in Coxsackie infection, namely vesicobullous and erosive eruptions, extensive cutaneous involvement, periorificial lesions, localization in areas of atopic dermatitis or in children with atopic dermatitis (the so-called eczema coxsackium), Gianotti-Crosti-like lesions, petechial/purpuric eruptions, delayed onychomadesis, and palmoplantar desquamation. Finally, adult cases appear to occur with this form of hand-foot-and-mouth disease, likely due to fecal-oral transmission in a household setting.

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.

Presence of human non-polio enterovirus and parechovirus genotypes in an Amsterdam hospital in 2007 to 2011 compared to national and international published surveillance data: a comprehensive review

Enteroviruses (EV) and human parechoviruses (HPeV) are endemic worldwide. These infections are a constant cause of hospitalisation and severe disease, predominantly in young children and infants. Coordinated monitoring and surveillance are crucial to control these infections. We have monitored EV and HPeV epidemiology in Amsterdam from 2007 to 2011 with real-time RT-PCR and direct genotyping, facilitating highly sensitive surveillance. Moreover, we conducted a literature survey of existing surveillance data for comparison. Only 14 studies were identified. While HPeV1 was most frequently detected in Amsterdam, EV-B viruses dominated nationally and internationally. Furthermore, the top 10 strains detected differed yearly and per study. However, detection and typing methods were too varied to allow direct comparison and comprehension of the worldwide distribution and circulation patterns of the different genotypes. This limited a direct response to anticipate peaks. Uniform European monitoring programmes are essential to aid prediction of outbreaks and disease management.

Pyrrolidine dithiocarbamate inhibits enterovirus 71 replication by down-regulating ubiquitin-proteasome system

Enterovirus 71 (EV71) is the main causative pathogen of hand, foot, and mouth disease (HFMD). The severe neurological complications caused by EV71 infection and the lack of effective therapeutic medicine underline the importance of searching for antiviral substances. Pyrrolidine dithiocarbamate (PDTC), an antioxidant, has been reported to inhibit the replication of coxsackievirus B (CVB) through dysregulating ubiquitin-proteasome system (UPS). In this study, we demonstrated that PDTC exerted potent antiviral effect on EV71. Viral RNA synthesis, viral protein expression, and the production of viral progeny were significantly reduced by the treatment of PDTC in Vero cells infected with EV71. Similar to the previous report about the inhibitory effect of PDTC on UPS, we found that PDTC treatment led to decreased levels of polyubiquitinated proteins in EV71-infected cells. The inhibitory effect of PDTC on UPS was further confirmed by the increased accumulation of cell cycle regulatory proteins p21 and p53, which are normally degraded through UPS, while the expression levels of both proteins remained unchanged. We also showed that PDTC had no impact on the activity of proteasome. Thus, we demonstrated that the down-regulation of PDTC on UPS was the result of its inhibition on ubiquitination. More importantly, this study provides evidence that the inhibition on UPS was required for the antiviral activity of PDTC, since MG132, a potent proteasome inhibitor, significantly inhibited the cytopathic effect and viral protein synthesis in EV71-infected cells. We also found that the antioxidant property of PDTC did not contribute to its antiviral effect, since N-acetyl-l-cysteine, a potent antioxidant, could not inhibit viral replication. In addition, CPE and viral protein synthesis were not inhibited in the cells pretreated with PDTC 2h before viral infection and then cultured in the media with no PDTC supplement, while the antioxidant effect of PDTC was retained. PDTC also showed significant inhibition on apoptosis induced by EV71 infection when it was applied at the early stage of viral infection. Our results collectively suggest that PDTC could be a potential anti-EV71 compound which possesses both antiviral and anti-apoptotic capacity.

Enterovirus 71 infects brain-derived neural progenitor cells

Neural progenitor cells (NPCs) are stem cells that can differentiate into various neural lineage cells. The damage and loss of NPCs are associated with neurological conditions such as cognitive deficits and memory impairment. In a long-term study of patients with EV71, cognitive disorders were observed. Therefore, we hypothesized that NPCs may be permissive to EV71 infection. We demonstrated that NPCs are prone to EV71 infection and that these stem cells can support the active replication of this virus. Furthermore, EV71 infection triggers apoptosis, resulting in significant cell death in infected NPCs. However, EV71 did not replicate in the differentiated cell types that were tested. Our findings suggest that EV71 can infect NPCs and cause the depletion of these cells.

Enterovirus 71 3C inhibits cytokine expression through cleavage of the TAK1/TAB1/TAB2/TAB3 complex

Enterovirus 71 (EV71) causes hand, foot, and mouth disease in young children and infants. Severe infection with EV71 can lead to various neurological complications or fatal diseases. However, the mechanism of EV71 pathogenesis is poorly understood. Emerging evidence suggests that EV71 modulates type I interferon (IFN) and cytokine responses. Here, we show that EV71 disables components of the TAB2 complex through the 3C protein. When expressed in mammalian cells, EV71 3C interacts with TAB2 and TAK1, which inhibits NF-κB activation. Furthermore, 3C mediates cleavage of TAB2 and its partners, which requires the protease activity. H40D or C147S substitution in the 3C active sites abolishes its activity, whereas R84Q or V154S substitution in the RNA binding domain has no effect. The 3C protein targets TAB2 at Q113-S114, TAK1 at Q360-S361, TAB1 both at Q414-G415 and Q451-S452, and TAB3 at Q173-G174 and Q343-G344. Importantly, overexpression of TAB2 inhibits EV71 replication, whereas addition of cleaved fragments has no effect. Thus, an equilibrium between the TAB2 complex and EV71 3C represents a control point of viral infection. These results suggest that TAK1/TAB1/TAB2/TAB3 cleavage mediated by EV71 may be a mechanism to interfere with inflammatory responses.

IMPORTANCE

The TAK1 complex plays a critical role in the activation of NF-κB and cytokine production. However, little is known about its connection to enterovirus 71 (EV71). We demonstrate that EV71 3C suppresses cytokine expression via cleavage of the TAK1 complex proteins. EV71 3C interacts with TAB2 and TAK1. Furthermore, overexpression of TAB2 inhibits EV71 replication, whereas addition of cleaved fragment has no effect. These results suggest that the interplay of EV71 and the TAK1 complex influences the outcome of viral infection.

Histopathological features and distribution of EV71 antigens and SCARB2 in human fatal cases and a mouse model of enterovirus 71 infection

Enterovirus 71 (EV71) is a neurotropic pathogen that causes hand, foot, and mouth disease. While infection is usually self-limiting, a minority of patients infected with EV71 develop severe neurological complications. In humans, EV71 has been reported to utilize the scavenger receptor class B, member 2 (SCARB2) as a receptor for infectious cellular entry. In this study, we define the pathological features of EV71-associated disease as well as the distribution of EV71 antigen and SCARB2 in human fatal cases and a mouse model. Histopathologically, human fatal cases showed severe central nervous system (CNS) changes, mainly in the brainstems, spinal cords, and thalamus. These patient further exhibited pulmonary edema and necrotic enteritis. Immunohistochemical analysis of human fatal cases demonstrated that EV71 antigen and SCARB2 were observed mainly in neurons, microglia cells and inflammatory cells in the CNS, and epithelial cells in the intestines. However, skeletal muscle tissue was negative for EV71 antigen. In a mouse model of EV71 infection, we observed massive necrotic myositis, different degrees of viral diseases in CNS, and extensive interstitial pneumonia. In mice, EV71 exhibits strong myotropism compared to the neurotropism seen in humans. EV71 antigen was detected in the spinal cord and brainstem of mice. However, there was no clear correlation between mouse SCARB2 and EV71 antigen distribution in the mouse model, consistent with previous results that SCARB2 functions as a receptor for EV71 in humans but not mice. The EV71-induced lesions seen in the mouse model resembled the pathological changes seen in human samples. These results increase our understanding of EV71 pathogenesis and will inform further work developing a mouse model for EV71 infection.

Early dexamethasone treatment exacerbates enterovirus 71 infection in mice

Enterovirus 71 (EV71) infection can induce encephalitis. Overt immune responses is suspected to cause severe symptoms, so anti-inflammatory agents, corticosteroids have been recommended for treatment. However, one clinical study reported that treatment with glucocorticoids, dexamethasone (Dex) exacerbates disease severity. Here we investigated Dex treatment on EV71 infection using the murine model and found that both long-term (14-day) and short-term (4-day) Dex treatment starting from 1 or 3 days postinfection increased the mortality and disease severity of infected mice. Dex treatment starting from 4 or 8 days postinfection did not affect mouse mortality and disease severity. Early Dex treatment starting from 1 day postinfection caused atrophy and enhanced apoptosis in lymphoid organs to decrease the numbers of lymphocytes (CD4(+) T cells, CD8(+) T cells, and CD19(+) B cells) and to increase viral loads in infected tissues of mice. Our results demonstrate that Dex treatment has no beneficial effect on EV71 infection.

Epidemiology of enterovirus 71 infections in Taiwan

Enterovirus 71 (EV71) was first described in USA in 1969 but retrospective studies in The Netherlands further detected EV71 in the clinical specimens collected in 1963. EV71 has one single serotype measured by using hyperimmune animal antisera but can be phylogenetically classified into three genogroups (A, B, and C) including 11 genotypes (A, B1-B5, C1-C5). In Taiwan, EV71 caused a large-scale nationwide epidemic in 1998. Retrospective studies further detected EV71 in clinical specimens collected from hand-foot-mouth disease patients in 1980 and 1986. Therefore, EV71 may have circulated in Taiwan prior to 1980. Since 1998, EV71 has cyclically caused nationwide epidemics with different predominant genotypes in 1998 (genotype C2), 2000-2001 (B4), 2005 (C4), 2008 (B5), and 2012 (B5). Phylogenetic analysis revealed that C4 viruses isolated in 2005 were probably from China, B5 viruses isolated in 2008 were probably from South Eastern Asia, and B5 viruses isolated in 2012 were probably from Xiamen, China. Several studies have collected postinfection sera from children to measure cross-reactive neutralizing antibody titers against different EV71 genotypes and found that antigenic differences between genogroup B and C viruses did not have a clear pattern but that genotype A virus was antigenically different from genogroup B and C viruses. In conclusion, EV71 cyclically caused nationwide epidemics through international importations. EV71 surveillance in Taiwan should combine genetic and serological methods.

The correlation between the presence of viremia and clinical severity in patients with enterovirus 71 infection: a multi-center cohort study

BACKGROUND

Enterovirus 71 (EV71) is a great disease burden across the whole world, particularly in Southeast Asia. However, in recent decades, the pathogenesis of severe EV71 infection was not well understood. This study was aimed to investigate the correlation between the presence of viremia and the clinical severity of EV71 infection.

METHODS

We organized a prospective cohort study and enrolled laboratory-confirmed EV71 cases in six tertiary care hospitals in Taiwan during the EV71 epidemic from 2011 to 2012. Blood samples were collected once in the acute stage, on the first day of admission. We used real-time RT-PCR to detect EV71 viremia. Demographical and clinical data were collected and the clinical severity was categorized into four grades. Data analysis was performed to identify the risk factors of viremia and the correlation between viremia and clinical severity of EV71 infection.

RESULTS

Of the total 224 enrolled patients, 59 (26%) patients were confirmed to have viremia. Two-thirds (68%) of viremic cases were detected within the first three days of infection. Viremia occurred more frequently in children under the age of one year old (odds ratios [OR] 4.82, p < 0.001) but the association between the presence of viremia and complicated EV71 infection was not found (OR 1.02, p = 0.96). In the viremia group, patients had significantly more severe complications if viremia was detected after the third day of disease onset (26% vs. 5%, p = 0.03).

CONCLUSIONS

Viremia occurred more frequently in children under the age of one year and viremia detected beyond three days after the onset of disease correlated with more severe disease in EV71 patients.

Clinical features of severe cases of hand, foot and mouth disease with EV71 virus infection in China

INTRODUCTION

Hand, foot and mouth disease (HFMD) caused by EV71 infection has become one of the major public health issues in China, which deeply affects children's health. The prevention and control of EV71 is a challenge currently because there is no safe and effective vaccine or antiviral medications available.

MATERIAL AND METHODS

A case control study was conducted in a designated hospital to compare severe and mild cases of patients infected with the EV71 virus. Demographic information along with clinical features of HFMD was collected through a standardized questionnaire. Multi-factorial logistic regression was used to analyze independent associations between potential risk factors and severe HFMD.

RESULTS

There were 120 cases (60 cases and 60 controls) collected. The male-to-female ratio was 1.3: 1 in the case group and 1.7: 1 in the control group. Multi-factorial logistic regression revealed that the main risk factors for severe cases were highest body temperature being ≥ 38.5°C (OR = 9.45, 95% CI: 2.07-43.11, p < 0.05), first visited a village level clinic (OR = 4.72, 95% CI: 1.15-19.45, p < 0.05), etc.

CONCLUSIONS

Close surveillance combined with laboratory testing should be in place during the epidemic period of HFMD. Grass root level medical facilities and training of clinical and laboratory staff should be reinforced so that the diagnostic and treatment capacity can be improved.

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.

Autism spectrum disorder secondary to enterovirus encephalitis

Millions of children are infected by enteroviruses each year, usually exhibiting only mild symptoms. Nevertheless, these viruses are also associated with severe and life-threatening infections, such as meningitis and encephalitis. We describe a 32-month-old patient with enteroviral encephalitis confirmed by polymerase chain reaction in cerebrospinal fluid, with unfavorable clinical course with marked developmental regression, autistic features, persistent stereotypes and aphasia. She experienced slow clinical improvement, with mild residual neurologic and developmental deficits at follow-up. Viral central nervous system infections in early childhood have been associated with autism spectrum disorders but the underlying mechanisms are still poorly understood. This case report is significant in presenting a case of developmental regression with autistic features and loss of language improving on follow-up. To our knowledge, this is the first published report of enterovirus encephalitis leading to an autism spectrum disorder.

Cell surface vimentin is an attachment receptor for enterovirus 71

Enterovirus 71 (EV71) is a highly transmissible pathogenic agent that causes severe central nervous system diseases in infected infants and young children. Here, we reported that EV71 VP1 protein could bind to vimentin intermediate filaments expressed on the host cell surface. Soluble vimentin or an antibody against vimentin could inhibit the binding of EV71 to host cells. Accompanied with the reduction of vimentin expression on the cell surface, the binding of EV71 to cells was remarkably decreased. Further evidence showed that the N terminus of vimentin is responsible for the interaction between EV71 and vimentin. These results indicated that vimentin on the host cell surface may serve as an attachment site that mediated the initial binding and subsequently increased the infectivity of EV71.

IMPORTANCE

This study delivers important findings on the roles of vimentin filaments in relation to EV71 infection and provides information that not only improves our understanding of EV71 pathogenesis but also presents us with potentially new strategies for the treatment of diseases caused by EV71 infections.

Co-circulation and genomic recombination of coxsackievirus A16 and enterovirus 71 during a large outbreak of hand, foot, and mouth disease in Central China

A total of 1844 patients with hand, foot, and mouth disease (HFMD), most of them were children of age 1–3-year-old, in Central China were hospitalized from 2011 to 2012. Among them, 422 were infected with coxsackievirus A16 (CVA16), 334 were infected with enterovirus 71 (EV71), 38 were co-infected with EV71 and CVA16, and 35 were infected with other enteroviruses. Molecular epidemiology analysis revealed that EV71 and CVA16 were detected year-round, but EV71 circulated mainly in July and CVA16 circulated predominantly in November, and incidence of HFMD was reduced in January and February and increased in March. Clinical data showed that hyperglycemia and neurologic complications were significantly higher in EV71-infected patients, while upper respiratory tract infection and C-reactive protein were significantly higher in CVA16-associated patients. 124 EV71 and 80 CVA16 strains were isolated, among them 56 and 68 EV71 strains were C4a and C4b, while 25 and 55 CVA16 strains were B1a and B1b, respectively. Similarity plots and bootscan analyses based on entire genomic sequences revealed that the three C4a sub-genotype EV71 strains were recombinant with C4b sub-genotype EV71 in 2B–2C region, and the three CVA16 strains were recombinant with EV71 in 2A–2B region. Thus, CVA16 and EV71 were the major causative agents in a large HFMD outbreak in Central China. HFMD incidence was high for children among household contact and was detected year-round, but outbreak was seasonal dependent. CVA16 B1b and EV71 C4b reemerged and caused a large epidemic in China after a quiet period of many years. Moreover, EV71 and CVA16 were co-circulated during the outbreak, which may have contributed to the genomic recombination between the pathogens. It should gain more attention as there may be an upward trend in co-circulation of the two pathogens globally and the new role recombination plays in the emergence of new enterovirus variants.

Anti-enterovirus 71 effects of chrysin and its phosphate ester

Enterovirus 71 (EV71) can cause severe disease and even lead to death in children, and an effective antiviral drug is currently unavailable. The anti-EV71 effect of chrysin (5,7-dihydroxyflavone), a natural flavonoid commonly found in many plants, was tested in this report. By using the predicting program Autodock 4.0 and an in vitro protease inhibition assay, we found that chrysin could suppress viral 3Cpro activity. Replication of viral RNA and production of viral capsid protein and the infectious virion were strongly inhibited by chrysin, without noticeable cytotoxicity. Cytopathic effects on cells were also prevented. Diisopropyl chrysin-7-yl phosphate (CPI), the phosphate ester for chrysin, was generated through a simplified Atheron-Todd reaction to achieve stronger anti-viral activity. CPI was also able to bind with and inhibit viral 3Cpro activity in vitro. As expected, CPI demonstrated more potent antiviral activity against EV71.

Long-term motor and cognitive outcome of acute encephalitis

OBJECTIVES

To examine the long-term motor and neurocognitive outcome of children with acute encephalitis and to look at possible prognostic factors.

METHODS

Children who were treated for acute encephalitis in 2000-2010 were reevaluated. All children and their parents were interviewed by using structured questionnaires, and the children underwent full neurologic examinations, along with comprehensive neurocognitive, attention, and behavioral assessments.

RESULTS

Of the 47 children enrolled, 1 died and 29 had neurologic sequelae, including motor impairment, mental retardation, epilepsy, and attention and learning disorders. Children with encephalitis had a significantly higher prevalence of attention-deficit/hyperactivity disorder (50%) and learning disabilities (20%) compared with the reported rate (5%-10%) in the general population of Israel (P < .05) and lower IQ scores. Lower intelligence scores and significantly impaired attention and learning were found even in children who were considered fully recovered at the time of discharge. Risk factors for long-term severe neurologic sequelae were focal signs in the neurologic examination and abnormal neuroimaging on admission, confirmed infectious cause, and long hospital stay.

CONCLUSIONS

Encephalitis in children may be associated with significant long-term neurologic sequelae. Significant cognitive impairment, attention-deficit/hyperactivity disorder, and learning disabilities are common, and even children who were considered fully recovered at discharge may be significantly affected. Neuropsychological testing should be recommended for survivors of childhood encephalitis.

Recent developments in antiviral agents against enterovirus 71 infection

Enterovirus 71 (EV-71) is the main etiological agent of hand, foot and mouth disease (HFMD). Recent EV-71 outbreaks in Asia-Pacific were not limited to mild HFMD, but were associated with severe neurological complications such as aseptic meningitis and brainstem encephalitis, which may lead to cardiopulmonary failure and death. The absence of licensed therapeutics for clinical use has intensified research into anti-EV-71 development. This review highlights the potential antiviral agents targeting EV-71 attachment, entry, uncoating, translation, polyprotein processing, virus-induced formation of membranous RNA replication complexes, and RNA-dependent RNA polymerase. The strategies for antiviral development include target-based synthetic compounds, anti-rhinovirus and poliovirus libraries screening, and natural compound libraries screening. Growing knowledge of the EV-71 life cycle will lead to successful development of antivirals. The continued effort to develop antiviral agents for treatment is crucial in the absence of a vaccine. The coupling of antivirals with an effective vaccine will accelerate eradication of the disease.

Time series analysis of hand-foot-mouth disease hospitalization in Zhengzhou: establishment of forecasting models using climate variables as predictors

Background

Large-scale outbreaks of hand-foot-mouth disease (HFMD) have occurred frequently and caused neurological sequelae in mainland China since 2008. Prediction of the activity of HFMD epidemics a few weeks ahead is useful in taking preventive measures for efficient HFMD control.

Methods

Samples obtained from children hospitalized with HFMD in Zhengzhou, Henan, China, were examined for the existence of pathogens with reverse-transcriptase polymerase chain reaction (RT-PCR) from 2008 to 2012. Seasonal Autoregressive Integrated Moving Average (SARIMA) models for the weekly number of HFMD, Human enterovirs 71(HEV71) and CoxsackievirusA16 (CoxA16) associated HFMD were developed and validated. Cross correlation between the number of HFMD hospitalizations and climatic variables was computed to identify significant variables to be included as external factors. Time series modeling was carried out using multivariate SARIMA models when there was significant predictor meteorological variable.

Results

2932 samples from the patients hospitalized with HFMD, 748 were detected with HEV71, 527 with CoxA16 and 787 with other enterovirus (other EV) from January 2008 to June 2012. Average atmospheric temperature (T{avg}) lagged at 2 or 3 weeks were identified as significant predictors for the number of HFMD and the pathogens. SARIMA(0,1,0)(1,0,0)₅₂ associated with T{avg} at lag 2 (T{avg}-Lag 2) weeks, SARIMA(0,1,2)(1,0,0)₅₂ with T{avg}-Lag 2 weeks and SARIMA(0,1,1)(1,1,0)₅₂ with T{avg}-Lag 3 weeks were developed and validated for description and predication the weekly number of HFMD, HEV71-associated HFMD, and Cox A16-associated HFMD hospitalizations.

Conclusion

Seasonal pattern of certain HFMD pathogens can be associated by meteorological factors. The SARIMA model including climatic variables could be used as an early and reliable monitoring system to predict annual HFMD epidemics.

The cytokine and chemokine profiles in patients with hand, foot and mouth disease of different severities in Shanghai, China, 2010

Background and purpose

Systemic upregulation of inflammatory cytokines is characteristic of critical severe hand, foot, and mouth disease (HFMD) with pulmonary edema. Thus, immunomodulatory medicines such as steroids, including methylprednisolone, have been proposed to treat patients with severe HFMD in China, because it is postulated that inflammatory cytokines play a role in the development of severe complications. This study is to further investigate the inflammatory response in the relatively mild HFMD patients, and whether steroid treatment has a beneficial effect on the suppression of inflammation in HFMD patients.

Method

We measured the levels of 50 kinds of chemokines, cytokines, growth factors and soluble receptors in serum samples from control patients without HFMD and the HFMD patients with or without prior treatment of intravenous methylprednisolone.

Results

Our present study found that even relatively mild HFMD patients without central nervous system (CNS) complications had elevated serum levels of inflammatory cytokines, including interleukin (IL)-3, IL-6, IL-12p40, and tumor necrosis factor (TNF)-α, which suggested systemic inflammation. In contrast, these patients also have decreased levels of other serum biomarkers, including IL-1Ra, IL-8, IL-16, soluble ICAM-1, CXCL-1, and CCL27. The dysregulation of cytokine and chemokine expression may be involved in CNS complications and unbalanced circulating leukocytes in HFMD patients. Surprisingly, patients treated with methylprednisolone had no difference in the expression levels of HFMD-associated biomarkers instead had slightly increased levels of IL-17A, which was not associated with the occurrence of HFMD.

Conclusion

Whether steroid treatment has any beneficial effect on the prognosis of HFMD patients requires to be further investigated.

Systemic inflammation is characteristic of severe hand, foot, and mouth disease (HFMD). Steroids are considered immunomodulators and have been officially recommended to treat the severe HFMD patients with CNS complications in China. So far, it is uncertain whether steroid treatment has an immunomodulatory role in inflammation in HFMD patients and has a real beneficial effect on their prognosis. This study revealed that even relatively mild HFMD patients without CNS complications had elevated inflammation. Unexpectedly, the inflammatory cytokine levels in patients treated with methylprednisolone, one kind of steroid, were not significantly different from those in patients without the treatment. Rather, the treated patients tended to have elevated levels of IL-17A, whose expression levels were actually not significantly associated with the presence of HFMD. IL-17A is known to play a role in the pathogenesis of CNS-related inflammatory diseases. Altogether, our study does not support the presumption that steroids have beneficial effect on the prognosis of HFMD patients by inhibiting systemic inflammation.

Enterovirus 71 VP1 activates calmodulin-dependent protein kinase II and results in the rearrangement of vimentin in human astrocyte cells

Enterovirus 71 (EV71) is one of the main causative agents of foot, hand and mouth disease. Its infection usually causes severe central nervous system diseases and complications in infected infants and young children. In the present study, we demonstrated that EV71 infection caused the rearrangement of vimentin in human astrocytoma cells. The rearranged vimentin, together with various EV71 components, formed aggresomes-like structures in the perinuclear region. Electron microscopy and viral RNA labeling indicated that the aggresomes were virus replication sites since most of the EV71 particles and the newly synthesized viral RNA were concentrated here. Further analysis revealed that the vimentin in the virus factories was serine-82 phosphorylated. More importantly, EV71 VP1 protein is responsible for the activation of calmodulin-dependent protein kinase II (CaMK-II) which phosphorylated the N-terminal domain of vimentin on serine 82. Phosphorylation of vimentin and the formation of aggresomes were required for the replication of EV71 since the latter was decreased markedly after phosphorylation was blocked by KN93, a CaMK-II inhibitor. Thus, as one of the consequences of CaMK-II activation, vimentin phosphorylation and rearrangement may support virus replication by playing a structural role for the formation of the replication factories. Collectively, this study identified the replication centers of EV71 in human astrocyte cells. This may help us understand the replication mechanism and pathogenesis of EV71 in human.

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.

Prospective comparison of the detection rates of human enterovirus and parechovirus RT-qPCR and viral culture in different pediatric specimens

BACKGROUND

Reverse-transcriptase quantitative real-time polymerase chain reaction (RT-qPCR) has become the gold standard for the diagnosis of human enterovirus (EV) and parechovirus (HPeV) infections. The detection rate of RT-qPCR in different pediatric body specimens has not been compared prospectively in a multicentre study.

OBJECTIVES

This study compared the diagnostic detection rates of EV and HPeV RT-qPCR and viral culture in different specimens (feces, nasopharynx, blood, urine and cerebrospinal fluid (CSF)) of pediatric patients.

STUDY DESIGN

This prospective, multicenter study performed an EV and HPeV RT-qPCR on nasopharynx, blood, urine, feces and CSF specimens and a viral culture on nasopharynx, feces and CSF specimens in symptomatic children<16 years.

RESULTS

Of 285 included children EV was detected in 140 (49%) and HPeV in 44 (15%) children. Both EV and HPeV RT-qPCR had a higher sensitivity and negative predictive value than EV and HPeV viral culture, respectively. EV and HPeV RT-qPCR in feces specimen had the highest sensitivity (99.2% and 95.1%) of all specimens. Pooling results of specimens increased the detection rate for both viruses.

CONCLUSION

Of all specimens, RT-qPCR in feces had the highest detection rate for both EV and HPeV in symptomatic pediatric patients. An EV was detected in all EV positive patients if a RT-qPCR was performed on both feces and CSF specimens or in both feces and urine specimens. HPeV was detected in all HPeV positive patients if a RT-qPCR was performed on both feces and CSF specimens, feces and nasopharynx specimens or CSF and nasopharynx specimens.

Causal inference regarding infectious aetiology of chronic conditions: a systematic review

BACKGROUND

The global burden of disease has shifted from communicable diseases in children to chronic diseases in adults. This epidemiologic shift varies greatly by region, but in Europe, chronic conditions account for 86% of all deaths, 77% of the disease burden, and up to 80% of health care expenditures. A number of risk factors have been implicated in chronic diseases, such as exposure to infectious agents. A number of associations have been well established while others remain uncertain.

METHODS AND FINDINGS

We assessed the body of evidence regarding the infectious aetiology of chronic diseases in the peer-reviewed literature over the last decade. Causality was assessed with three different criteria: First, the total number of associations documented in the literature between each infectious agent and chronic condition; second, the epidemiologic study design (quality of the study); third, evidence for the number of Hill's criteria and Koch's postulates that linked the pathogen with the chronic condition. We identified 3136 publications, of which 148 were included in the analysis. There were a total of 75 different infectious agents and 122 chronic conditions. The evidence was strong for five pathogens, based on study type, strength and number of associations; they accounted for 60% of the associations documented in the literature. They were human immunodeficiency virus, hepatitis C virus, Helicobacter pylori, hepatitis B virus, and Chlamydia pneumoniae and were collectively implicated in the aetiology of 37 different chronic conditions. Other pathogens examined were only associated with very few chronic conditions (≤ 3) and when applying the three different criteria of evidence the strength of the causality was weak.

CONCLUSIONS

Prevention and treatment of these five pathogens lend themselves as effective public health intervention entry points. By concentrating research efforts on these promising areas, the human, economic, and societal burden arising from chronic conditions can be reduced.

Rapid and highly sensitive detection of Enterovirus 71 by using nanogold-enhanced electrochemical impedance spectroscopy

Enterovirus 71 (EV71) infection is an emerging infectious disease causing neurological complications and/or death within two to three days after the development of fever and rash. A low viral titre in clinical specimens makes the detection of EV71 difficult. Conventional approaches for detecting EV71 are time consuming, poorly sensitive, or complicated, and cannot be used effectively for clinical diagnosis. Furthermore, EV71 and Coxsackie virus A16 (CA16) may cross react in conventional assays. Therefore, a rapid, highly sensitive, specific, and user-friendly test is needed. We developed an EV71-specific nanogold-modified working electrode for electrochemical impedance spectroscopy in the detection of EV71. Our results show that EV71 can be distinguished from CA16, Herpes simplex virus, and lysozyme, with the modified nanogold electrode being able to detect EV71 in concentrations as low as 1 copy number/50 μl reaction volume, and the duration between sample preparation and detection being 11 min. This detection platform may have the potential for use in point-of-care diagnostics.

Global transcriptomic analysis of human neuroblastoma cells in response to enterovirus type 71 infection

Human enterovirus type 71 (EV71) is the major pathogen of hand-foot-and-mouth disease (HFMD) and has been associated with severe neurological disease and even death in infants and young children. The pathogenesis of EV71 infection in the human central nervous system remains unclear. In this study, human whole genome microarray was employed to perform transcriptome profiling in SH-SY5Y human neuroblastoma cells infected with EV71. The results indicated that EV71 infection lead to altered expression of 161 human mRNAs, including 74 up-regulated genes and 87 down-regulated genes. Bioinformatics analysis indicated the possible roles of the differentially regulated mRNAs in selected pathways, including cell cycle/proliferation, apoptosis, and cytokine/chemokine responses. Finally, the microarray results were validated using real-time RT-PCR with high identity. Overall, our results provided fundamental information regarding the host response to EV71 infection in human neuroblastoma cells, and this finding will help explain the pathogenesis of EV71 infection and virus-host interaction.

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.

Implications of Age-Dependent Immune Responses to Enterovirus 71 Infection for Disease Pathogenesis and Vaccine Design

Epidemics of enterovirus serotype 71 (EV71) infection in Asia appear to be increasing in size and severity, and there is increasing concern for pandemic spread. Efforts are underway to develop an effective EV71 vaccine. However, the immunologic correlates of protection against EV71 infection are not fully understood, and studies suggest that severe complications may result from a combination of pathological immune responses and direct viral effects. Severe disease and death typically occur only in young children, which is likely due in part to a lack of EV71-specific adaptive immunity but possibly also due to age-dependent hyperactive innate immune responses. Infants are the primary targets of EV71 vaccination strategies. Therefore, studies are needed to understand the interplay between age, immunopathology, and severity of EV71 infection to distinguish protective from harmful immune responses and to guide the development of effective EV71 vaccines. This review summarizes our current understanding and outlines the next steps forward.

A safety study of inactivated Enterovirus 71 vaccine

Enterovirus 71 (EV71) is one of the major causative agents for hand, foot and mouth disease (HFMD) in childhood. Nowadays, HFMD or EV71 infections have already become an important public health issue throughout the world. Vaccination may be the most effective measure to control the transmission of the virus. Therefore, to pave EV71 vaccine into human clinical trial, in the present study a comprehensive preclinical safety assessment of inactivated EV71 vaccine including single- and repeat-dose toxicity studies were conducted in rats and cynomolgus monkeys. No abnormal findings were observed in rats following single intramuscular administration with EV71 vaccine (640 U). The results also showed no obvious systemic toxicities from four repetitive intramuscular injections, with a 14-d interval, of two dosages of EV71 vaccine in the two animal species. Antinuclear antibody response was not detected after the repeated administrations. Histopathological examination demonstrated the minimal to severe inflammatory changes in muscle tissues of the injection sites in EV71 vaccine-injected animals and most of findings have been improved over time. Furthermore, test article could induce highly EV71-specfic neutralizing antibody response in both animal species. Taken together, these data suggested a favorable safety profile for inactivated EV71 vaccine and supported this product to enter human phase I clinical trial.

The influences of temperature on spatiotemporal trends of hand-foot-and-mouth disease in mainland China

Understanding the influence of temperature on hand-foot-and-mouth disease (HFMD) is an important public health concern as well as being a major climate-infection issue in mainland China. City-scale data of incidence rates (IRs) of HFMD and temperature from 2008 to 2009 in mainland China has been analyzed. There were two peak periods for HFMD prevalence from April to July and August to November. Regions with higher monthly IR of HFMD periodically shifted following the pattern of south-north-south from March to December. Monthly IR of HFMD at city scale were closely associated with both average monthly temperature and monthly temperature range. Our study shows that spatiotemporal trends of HFMD infection were sensitive to temperature variation, and suggest that preventive measures should be considered for limiting the epidemic of HFMD in the cities with higher monthly IR during the peak periods.

Cleavage of interferon regulatory factor 7 by enterovirus 71 3C suppresses cellular responses

Enterovirus 71 (EV71) is a positive-stranded RNA virus which is capable of inhibiting innate immunity. Among virus-encoded proteins, the 3C protein compromises the type I interferon (IFN-I) response mediated by retinoid acid-inducible gene-I (RIG-I) or Toll-like receptor 3 that activates interferon regulatory 3 (IRF3) and IRF7. In the present study, we report that enterovirus 71 downregulates IRF7 through the 3C protein, which inhibits the function of IRF7. When expressed in mammalian cells, the 3C protein mediates cleavage of IRF7 rather than that of IRF3. This process is insensitive to inhibitors of caspase, proteasome, lysosome, and autophagy. H40D substitution in the 3C active site abolishes its activity, whereas R84Q or V154S substitution in the RNA binding motif has no effect. Furthermore, 3C-mediated cleavage occurs at the Q189-S190 junction within the constitutive activation domain of IRF7, resulting in two cleaved IRF7 fragments that are incapable of activating IFN expression. Ectopic expression of wild-type IRF7 limits EV71 replication. On the other hand, expression of the amino-terminal domain of IRF7 enhances EV71 infection, which correlates with its ability to interact with and inhibit IRF3. These results suggest that control of IRF7 by the 3C protein may represent a viral mechanism to escape cellular responses.

Enterovirus 71 infection increases expression of interferon-gamma-inducible protein 10 which protects mice by reducing viral burden in multiple tissues

Enterovirus 71 (EV71) infection has induced fatal encephalitis in thousands of young children in the Asia-Pacific region over the last decade. EV71 infection continues to cause serious problems in areas with outbreaks, because vaccines and antiviral therapies are not available. Lymphocytes are present in the brains of infected patients and mice, and they protect mice from infection by decreasing the viral burden. The chemokines responsible for recruiting lymphocytes to infected organs are yet to be identified. Among the lymphocyte chemokines detected, high levels of interferon-gamma-inducible protein-10 (IP-10) are found in the plasma and cerebral spinal fluid of patients with brainstem encephalitis as compared with the levels of a monokine induced by gamma interferon (Mig). Using a murine model to investigate the induction of IP-10 by EV71 infection, we observed that EV71 infection significantly enhanced IP-10 protein expression in the serum and brain, with kinetics similar to viral titres in the blood and brain. Brain neurons of infected mice expressed IP-10. Using wild-type mice and IP-10 gene knockout mice to investigate the role of IP-10 in EV71 infection, we found that IP-10 deficiency significantly reduced levels of Mig in serum, and levels of gamma interferon and the number of CD8 T cells in the mouse brain. Absence of IP-10 significantly increased the mortality of infected mice by 45%, with slow virus clearance in several vital tissues. Our observations are consistent with a model where EV71 infection boosts IP-10 expression to increase gamma interferon and Mig levels, infiltration of CD8 T cells, virus clearance in tissues and the survival of mice.

Quinacrine impairs enterovirus 71 RNA replication by preventing binding of polypyrimidine-tract binding protein with internal ribosome entry sites

Since the 1980s, epidemics of enterovirus 71 (EV71) and other enteroviruses have occurred in Asian countries and regions, causing a wide range of human diseases. No effective therapy is available for the treatment of these infections. Internal ribosome entry sites (IRESs) are indispensable for the initiation of translation in enteroviruses. Several cellular factors, as well as the ribosome, are recruited to the conserved IRES during this process. Quinacrine intercalates into the RNA architecture and inhibits RNA transcription and protein synthesis, and a recent study showed that quinacrine inhibited encephalomyocarditis virus and poliovirus IRES-mediated translation in vitro without disrupting internal cellular IRES. Here, we report that quinacrine was highly active against EV71, protecting cells from EV71 infection. Replication of viral RNA, expression of viral capsid protein, and production of virus were all strongly inhibited by quinacrine. Interaction of the polypyrimidine tract-binding protein (PTB) with the conserved IRES was prevented by quinacrine. Coxsackieviruses and echovirus were also inhibited by quinacrine in cultured cells. These results indicate that quinacrine may serve as a potential protective agent for use in the treatment of patients with chronic enterovirus infection.

Antiviral drug discovery for the treatment of enterovirus 71 infections

Enterovirus 71 (EV71) is a small, positive-sense, single-stranded RNA virus in the genus Enterovirus, family Picornavirus. It causes hand, foot and mouth disease in infants and children, which in a small percentage of cases progresses to central nervous system infection, ranging from aseptic meningitis to fatal encephalitis. Sporadic cases of EV71 infection occur throughout the world, but large epidemics have occurred recently in Southeast Asia and China. There are currently no approved vaccines or antiviral therapies for the prevention or treatment of EV71 infection. This paper reviews efforts to develop antiviral therapies against EV71.

Picornavirus and enterovirus diversity with associated human diseases

Members of the Picornaviridae family are non-enveloped, positive-stranded RNA viruses with a 30nm icosahedral capsid. This virus family exhibits a considerable amount of genetic variability driven both by mutation and recombination. Recently, three previously unknown human picornaviruses, namely the human Saffold cardiovirus, cosavirus and salivirus, have been identified in stools or respiratory samples from subjects presenting symptoms ranging from gastroenteritis to acute flaccid paralysis. However, these viruses were also frequently detected in asymptomatic subjects and their clinical relevance remains to be elucidated. The Enterovirus genus is a prototype example of the Picornaviridae heterogeneity at both genetic and phenotypic levels. This genus is divided into 10 species, seven of which contain human viruses, including three Rhinovirus species. Both human rhino- and enteroviruses are also characterized by high levels of genetic variability, as exemplified by the existence of over 250 different serotypes and the recent discovery of new enterovirus genotypes and the Rhinovirus C species. Despite their common genomic features, rhinoviruses are restricted to the respiratory tract, whereas the vast majority of enteroviruses infect the gastrointestinal tract and can spread to other organs, such as the heart or the central nervous system. Understanding the genetic determinants of such phenotypic diversity is an important challenge and a field for future investigation. Better characterization of these ubiquitous human pathogens may help to develop vaccines or antiviral treatments and to monitor the emergence of new strains.

Enterovirus 71 blocks selectively type I interferon production through the 3C viral protein in mice

Type I interferons (IFNs) represent an essential innate defense mechanism for controlling enterovirus 71 (EV 71) infection. Mice inoculated with EV 71 produced a significantly lower amount of type I IFNs than those inoculated with poly (I:C), adenovirus type V, or coxsackievirus B3 (CB3). EV 71 infection, however, mounted a proinflammatory response with a significant increase in the levels of serum and brain interleukin (IL)-6, monocyte chemoattractant protein-1, tumor necrosis factor, and IFN-γ. EV 71 infection abolished both poly (I:C)- and CB3-induced type I IFN production of mice. Such effect was not extended to other enteroviruses including coxsackievirus A24, B2, B3, and echovirus 9, as mice infected with these viruses retained type I IFN responsiveness upon poly (I:C) challenge. In addition, EV 71-infected RAW264.7 cells produced significantly lower amount of type I IFNs than non-infected cells upon poly (I:C) stimulation. The inhibitory effect of EV 71 on type I IFN production was attributed to the viral protein 3C, which was confirmed using over-expression systems in both mice and RAW264.7 cells. The 3C over-expression, however, did not interfere with poly (I:C)-induced proinflammatory cytokine production. These findings indicate that EV 71 can hamper the host innate defense by blocking selectively type I IFN synthesis through the 3C viral protein.

Co-detection in the pathogenesis of severe hand-foot-mouth disease

It still needs to be elucidated whether co-detection of EV71 with other intestinal tract viruses plays a role in the pathogenesis of severe hand-foot-mouth disease (HFMD). A total of 680 stool specimens collected from clinically diagnosed mild and severe-HFMD patients were tested for EV71, CA16, norovirus, bocavirus and rotavirus. The results showed that EV71 was significantly associated with severe-HFMD patients. Co-detection of EV71 with norovirus and rotavirus was also significantly associated with severe-HFMD patients: The OR (95 % CI) value was 6.466 (2.735, 15.283) and 7.561 (3.560, 16.057), p < 0.001, respectively. Co-detection of EV71 with rotavirus or norovirus is probably associated with severe HFMD.

CD4 T-cell-independent antibody response reduces enterovirus 71 lethality in mice by decreasing tissue viral loads

Enterovirus 71 (EV71) has induced fatal encephalitis in hundreds of thousands of infants and young children in the Asia-Pacific region since the past decade. Lymphocyte and antibody responses have been suspected to aggravate EV71-induced neurological symptoms, so anti-inflammatory agents have been used to treat patients with neurological symptoms. In the present study, we found that mice deficient in CD4⁺ T cells were resistant to EV71 infection as wild-type mice, whereas mice deficient in B cells were highly susceptible to viral infection. Compensation of CD4 T-cell function by other immune cells was not likely, because wild-type mice depleted of CD4⁺ T cells were also resistant to viral infection. Infected CD4 T-cell-deficient mice produced virus-specific neutralizing antibodies, IgM and IgG. Moreover, adoptive transfer of the virus-specific antibody produced by infected CD4 T-cell-deficient mice protected B-cell-deficient mice from infection by reducing tissue viral loads. Collectively, our results show that the CD4 T-cell-independent antibody response promotes the survival of EV71-infected mice and suggest great potential for the use of vaccines and neutralizing antibodies to reduce fatal symptoms in patients.