Altered cellular but not humoral reactions in children with complicated enterovirus 71 infections in Taiwan

Pathogenesis and Preventive Tactics of Immune-Mediated Non-Pulmonary COVID-19 in Children and Beyond

The COVID-19 pandemic has evolved to immune escape and threatened small children and the elderly with a higher severity and fatality of non-pulmonary diseases. These life-threatening non-pulmonary COVID-19 diseases such as acute necrotizing encephalopathies (ANE) and multisystem inflammatory syndrome in children (MIS-C) are more prevalent in children. However, the mortality of multisystem inflammatory syndrome in adults (MIS-A) is much higher than that of MIS-C although the incidence of MIS-A is lower. Clarification of immunopathogenesis and genetic susceptibility of inflammatory non-pulmonary COVID-19 diseases would provide an appropriate guide for the crisis management and prevention of morbidity and fatality in the ongoing pandemic. This review article described three inflammatory non-pulmonary COVID-19 diseases including (1) meningoencephalitis (ME), (2) acute necrotizing encephalopathies (ANE), and (3) post-infectious multisystem inflammatory syndrome in children (MIS-C) and in adults (MIS-A). To prevent these life-threatening non-pulmonary COVID-19 diseases, hosts carrying susceptible genetic variants should receive prophylactic vaccines, avoid febrile respiratory tract infection, and institute immunomodulators and mitochondrial cocktails as early as possible.

The Bottlenecks of Preparing Virus Particles by Size Exclusion for Antibody Generation

Enterovirus 71 (EV71) is the major etiological agent contributing to the development of hand-foot-mouth disease (HFMD). There are not any global available vaccines or antibody drugs against EV71 released yet. In this study, we perform the virus immunization in a cost-effective and convenient approach by preparing virus particles from size exclusion and immunization of chicken. Polyclonal yolk-immunoglobulin (IgY) was simply purified from egg yolk and monoclonal single-chain variable fragments (scFv) were selected via phage display technology with two scFv libraries containing 6.0 × 106 and 1.3 × 107 transformants. Specific clones were enriched after 5 rounds of bio-panning and four identical genes were classified after the sequence analysis. Moreover, the higher mutation rates were revealed in the CDR regions, especially in the CDR3. IgY showed specific binding activities to both EV71-infected and Coxsackievirus 16-infected cell lysates and high infectivity inhibitory activity of EV71. However, while IgY detected a 37 kDa protein, the selected scFv seemingly detected higher size proteins which could be cell protein instead of EV71 proteins. Despite the highly effective chicken antibody generation, the purity of virus particles prepared by size exclusion is the limitation of this study, and further characterization should be carried out rigorously.

Role of Non-Coding RNA in Neurological Complications Associated With Enterovirus 71

Enterovirus 71 (EV71) is the main pathogenic virus that causes hand, foot, and mouth disease (HFMD). Studies have reported that EV71-induced infections including aseptic meningitis, acute flaccid paralysis, and even neurogenic pulmonary edema, can progress to severe neurological complications in infants, young children, and the immunosuppressed population. However, the mechanisms through which EV71 causes neurological diseases have not been fully explored. Non-coding RNAs (ncRNAs), are RNAs that do not code for proteins, play a key role in biological processes and disease development associated with EV71. In this review, we summarized recent advances concerning the impacts of ncRNAs on neurological diseases caused by interaction between EV71 and host, revealing the potential role of ncRNAs in pathogenesis, diagnosis and treatment of EV71-induced neurological complications.

Immunopathogenesis of Different Emerging Viral Infections: Evasion, Fatal Mechanism, and Prevention

Different emerging viral infections may emerge in different regions of the world and pose a global pandemic threat with high fatality. Clarification of the immunopathogenesis of different emerging viral infections can provide a plan for the crisis management and prevention of emerging infections. This perspective article describes how an emerging viral infection evolves from microbial mutation, zoonotic and/or vector-borne transmission that progresses to a fatal infection due to overt viremia, tissue-specific cytotropic damage or/and immunopathology. We classified immunopathogenesis of common emerging viral infections into 4 categories: 1) deficient immunity with disseminated viremia (e.g., Ebola); 2) pneumocytotropism with/without later hyperinflammation (e.g., COVID-19); 3) augmented immunopathology (e.g., Hanta); and 4) antibody-dependent enhancement of infection with altered immunity (e.g., Dengue). A practical guide to early blocking of viral evasion, limiting viral load and identifying the fatal mechanism of an emerging viral infection is provided to prevent and reduce the transmission, and to do rapid diagnoses followed by the early treatment of virus neutralization for reduction of morbidity and mortality of an emerging viral infection such as COVID-19.

IFI27 as a potential indicator for severe Enterovirus 71-infected hand foot and mouth disease

The pathogenesis of Enterovirus 71 (EV71)-induced severe hand foot and mouth disease (HFMD) has not yet been clearly established. Further study into the mechanisms underlying host immune responses to EV71 infection and identifying important predictors will be crucial to antiviral treatment and early recognition of severe HFMD. The present study establishes that T help (Th)1 type, Th2 type, and Th17 type cytokine levels in serum of peripheral blood from patients with severe HFMD is higher than in peripheral blood from healthy subjects. The most significant increase occurred as the IL-6. In order to identify the important molecules in peripheral blood mononuclear cells (PBMCs) from severe HFMD patients, we performed transcriptome sequencing analysis of PBMC from severe HFMD patients and compared them to healthy controls. Interferon α-inducible protein 27 (IFI27) and cluster of differentiation 27 (CD27) were found to be the most significant differentially expressed gene. Finally, IFI27 was proved to be present at higher levels in patients with severe HFMD than in patients with mild HFMD. Our results suggest that IFI27 may be an indicator of the severity of cases EV71-induced HFMD.

Enterovirus and Encephalitis

Enterovirus-induced infection of the central nervous system (CNS) results in acute inflammation of the brain (encephalitis) and constitutes a significant global burden to human health. These viruses are thought to be highly cytolytic, therefore normal brain function could be greatly compromised following enteroviral infection of the CNS. A further layer of complexity is added by evidence showing that some enteroviruses may establish a persistent infection within the CNS and eventually lead to pathogenesis of certain neurodegenerative disorders. Interestingly, enterovirus encephalitis is particularly common among young children, suggesting a potential causal link between the development of the neuroimmune system and enteroviral neuroinvasion. Although the CNS involvement in enterovirus infections is a relatively rare complication, it represents a serious underlying cause of mortality. Here we review a selection of enteroviruses that infect the CNS and discuss recent advances in the characterization of these enteroviruses with regard to their routes of CNS infection, tropism, virulence, and immune responses.

Pathogenesis of hand-foot-mouth disease caused by enterovirus 71

Hand-foot-mouth disease (HFMD) is a global infectious disease. The infected population is mainly infants and young children. Enterovirus 71 (EV71) is the main pathogen. In addition to HFMD, EV71 infection can also affect the nervous system and other organs, resulting in aseptic meningitis, brainstem encephalitis, and poliomyelitis-like paralysis, causing serious harm to children's health. At present, the pathogenesis of HFMD caused by EV71 is still unclear, and there is no effective treatment. In this paper, we discuss the factors influencing EV71 infection from the aspects of virus gene recombination and spontaneous mutation, host genes, and receptor sites, review the pathogenesis of HFMD caused by EV71 based on the study findings from animal infection models, and explore the main problems in the study of pathogenesis of this condition, in order to provide reference for the prevention and treatment of HFMD and for the development of new drugs or effective vaccines for EV71 infection.

Characterization of inflammatory cytokine profiles in cerebrospinal fluid of hand, foot, and mouth disease children with enterovirus 71-related encephalitis in Hangzhou, Zhejiang, China

Enterovirus 71 (EV71) is an important etiological agent of hand, foot, and mouth disease (HFMD), which can also lead to severe neurological complications (eg, encephalitis) in young children. Although a series of reports on EV71 infection have been published, the pathogenic mechanism of EV71 infection is still not fully understood.We evaluated the cerebrospinal fluid (CSF) levels of the inflammatory cytokines interleukin (IL)-8, IL-1β, IL-6, IL-10, tumor necrosis factor (TNF)-α, and IL-12p70 in 88 children with EV71-related encephalitis and 19 children with febrile convulsion (FC) with the use of commercial cytometric bead array kits.The levels of IL-8, IL-1β, IL-6, and IL-10 in CSF were significantly higher in encephalitis group when compared with those observed in FC group, while no significant changes were noted in the levels of TNF-α and IL-12p70. In addition, significant and positive correlations among CSF IL-8, IL-1β, IL-6, and IL-10 were observed in encephalitis group. Furthermore, receiver operator characteristic analysis determined a cut-off value of 10.62 pg/mL for IL-6 to discriminate encephalitis patients from FCs with the sensitivity and specificity of 89.8% and 84.2%, respectively. Moreover, logistic regression analyses revealed that IL-6 was an independent predictor of EV71-related encephalitis (odds ratio = 23.241, P < .001).Our results indicate that 4 inflammatory cytokines (IL-8, IL-1β, IL-6, and IL-10) play important roles in the pathogenesis of EV71 infection. IL-6 may be used for the evaluation of EV71-related encephalitis and as a potential therapy candidate for EV71 infection.

Effectiveness of EV-A71 vaccination in prevention of paediatric hand, foot, and mouth disease associated with EV-A71 virus infection requiring hospitalisation in Henan, China, 2017-18: a test-negative case-control study

BACKGROUND

Inactivated monovalent enterovirus A71 (EV-A71) vaccines are now available in China to reduce the substantial public health burden of hand, foot, and mouth disease. However, post-licensure monitoring of vaccine effectiveness is important. We did an observational test-negative study of EV-A71 vaccine effectiveness.

METHODS

Children with hand, foot, and mouth disease who were admitted to Henan Children's Hospital (Zhengzhou, China) within 7 days of illness onset were invited to participate in this test-negative case-control study. Participant vaccination history with EV-A71, including the number of doses received and the date of each dose of vaccination, was elicited from parents or legal guardians of participants with a standardised questionnaire. Children must have received two doses before hospitalisation to be counted as fully vaccinated. Patients who had received a single dose before hospitalisation were classified as partly vaccinated. Children who had received no EV-A71 vaccine before hospitalisation were classified as unvaccinated. Throat swabs and stool samples collected from patients were tested by RT-PCR to identify EV-A71 and other enteroviruses. The primary outcome of the study was paediatric hand, foot, and mouth disease associated with EV-A71 requiring hospitalisation. We estimated vaccine effectiveness with conditional logistic regression models adjusted for potential confounders.

FINDINGS

Between Feb 15, 2017, and Feb 15, 2018, we enrolled 1803 children aged 6-71 months with hand, foot, and mouth disease. 234 (13%) children tested positive for EV-A71, 1529 (85%) tested positive for other enteroviruses-528 (29%) were positive for Coxsackievirus (CV)-A6 and 342 (19%) were positive for CV-A16-and 29 (2%) tested negative for all enteroviruses. 11 (1%) children with neither throat swab nor stool testing results were excluded from further analyses. Overall vaccine effectiveness was estimated to be 85·4% (95% CI 53·2 to 95·4) for fully vaccinated children and 63·1% (13·1 to 84·3) for partly vaccinated children. The vaccine effectiveness for full vaccination was estimated to be 91·1% (35·1 to 98·8) among non-severe cases compared with 73·3% (-32·6 to 94·6) in severe cases. The vaccine effectiveness for partial vaccination was 77·9% (4·3 to 94·9) in children aged 24-71 months and 40·8% (-71·1 to 79·5) in children aged 6-23 months. We found no significant association between full or partial vaccination and CV-A6 or CV-A16-related hand, foot, and mouth disease.

INTERPRETATION

EV-A71 vaccination was effective in preventing non-severe hand, foot, and mouth disease associated with EV-A71 virus infection in children aged 6-71 months, and we found evidence that one dose of vaccination provided partial protection for children aged 24-71 months. Introduction of multivalent vaccines could further reduce the burden of hand, foot, and mouth disease.

FUNDING

The National Science Fund for Distinguished Young Scholars.

Genetic and Environmental Interaction in Type 1 Diabetes: a Relationship Between Genetic Risk Alleles and Molecular Traits of Enterovirus Infection?

PURPOSE OF REVIEW

We provide an overview of the current knowledge regarding the natural history of human type 1 diabetes (T1D) and the documented associations between virus infections (in particular the enteroviruses) and disease development. We review studies that examine whether T1D-specific risk alleles in genes involved in the function of the immune system can alter susceptibility to virus infections or affect the magnitude of the host antiviral response. We also highlight where the major gaps in our knowledge exist and consider possible implications that new insights gained from the discussed gene-environment interaction studies may bring.

RECENT FINDINGS

A commonality between several of the studied T1D risk variants studied is their role in modulating the host immune response to viral infection. Generally, little support exists indicating that the risk variants increase susceptibility to infection and moreover, they usually appear to predispose the immune system towards a hyper-reactive state, decrease the risk of infection, and/or favor the establishment of viral persistence. In conclusion, although the current number of studies is limited, this type of research can provide important insights into the mechanisms that are central to disease pathogenesis and further describe how genetic and environmental factors jointly influence the risk of T1D development. The latter may provide genetic markers that could be used for patient stratification and for the selection of method(s) for disease prevention.

Self-assembled nanovehicle-mediated co-encapsulation of inactivated EV71 virus and CpG oligonucleotides elicits potent anti-EV71 humoral and cellular immune protective responses

Inactivated vaccines are widely used for prevention of viral disease. Both humoral and cellular immune responses have been shown to play important roles in the control and clearance of virus infections. CpG motif containing oligodeoxynucleotides (ODN) have recently gained considerable interest and been used as vaccine adjuvant due to their potent abilities to modulate host immune response. In this study, CpG-ODN adjuvant and inactivated viral particles of enterovirus 71 (EV71) were co-encapsulated into nanoparticles (NP) generated by using protamine sulfate (PS) and carboxymethyl β-glucan (CMG) through a self-assembly approach. The administration of EV71 nanovaccine elicited not only specific anti-EV71 neutralizing antibody response, but also cellular immune response characterized by strong productions of IFN-α and IFN-γ. The results suggest that CMG/PS-based nanovehicles hold a great potential to be a novel platform for nanovaccine development against viral disease.

Immunocompetent and Immunodeficient Mouse Models for Enterovirus 71 Pathogenesis and Therapy

Enterovirus 71 (EV71) is a global health threat. Children infected with EV71 could develop hand-foot-and-mouth disease (HFMD), encephalitis, paralysis, pulmonary edema, and death. At present, no effective treatment for EV71 is available. We reviewed here various mouse models for EV71 pathogenesis and therapy. Earlier studies relied on the use of mouse-adapted EV71 strains. To avoid artificial mutations arising de novo during the serial passages, recent studies used EV71 clinical isolates without adaptation. Several human receptors for EV71 were shown to facilitate viral entry in cell culture. However, in vivo infection with human SCARB2 receptor transgenic mice appeared to be more limited to certain strains and genotypes of EV71. Efficacy of oral infection in these transgenic models is extremely low. Intriguingly, despite the lack of human receptors, immunodeficient neonatal mouse models can still be infected with EV71 clinical isolates via oral or intraperitoneal routes. Crossbreeding between SCARB2 transgenic and stat1 knockout mice generated a more sensitive and user-friendly hybrid mouse model. Infected hybrid mice developed a higher incidence and earlier onset of CNS disease and death. Different pathogenesis profiles were observed in models deficient in various arms of innate or humoral immunity. These models are being actively used for antiviral research.

T Cell Immunity To Enterovirus 71 Infection In Humans And Implications For Vaccine Development

Enterovirus 71 (EV-A71) is one of the major pathogens causing hand, foot and mouth disease (HFMD). Some strains can lead to neurological disease and fatality in children. Up to date, there is no FDA-approved vaccine to prevent severe HFMD and mortality. Although the inactivated vaccine has advanced to production in China, lack of long-term protection and the requirement of multiple boosters have necessitated the development of other types of vaccines. Recent studies indicate that cellular and not humoral immunity determines the clinical outcome of EV-A71 infections. High levels of cytokines such as IL-1β, IL-6, IL-10 and IFN-γ tend to correlate with clinical severity in patients with pulmonary edema and encephalitis. The live attenuated vaccine may serve as the preferred choice as it can induce excellent humoral and cellular immunity as well as live-long immunity. Expression of certain HLA alleles such as TNF-α promoter type II (-308 allele), HLA-A33 and HLA-DR17 responses have been linked to severe HFMD. However, the high variability of MHC genes could restrict T cell recognition and be a major obstacle in the design of peptide vaccines. Hence, the development of a T cell universal vaccine (incorporating both CD4⁺ and CD8⁺ T cell epitopes) that induces broad, multifunctional and cross-reactive CD8⁺ T cell responses maybe desirable.

Clinical Features and Peripheral Blood T Lymphocyte Subsets in Hand, Foot, and Mouth Disease According to Different Pathogens

OBJECTIVE

To investigate the changes in lymphocyte subsets that are caused by infection with different pathogens in children with hand, foot, and mouth disease.

METHODS

T lymphocyte subsets were measured in the patients' peripheral blood, and serum, throat swab, and fecal samples were tested for enterovirus.

RESULTS

Fecal and throat swab samples exhibited similar positive detection rates, and were significantly more likely to be positive, compared to serum samples (P < 0.01). The EV71-positive group exhibited significantly lower CD4 + TM cell counts (QR: 1.058), compared to the CD4 + TM cell counts in the CoxA16-positive group (QR: 1.391; P < 0.05).

CONCLUSIONS

Throat swab and fecal samples exhibited significantly higher positive detection rates, compared to serum samples. In addition, EV71-infected children exhibited significantly lower CD4+ T-cell counts, compared to CoxA16-infected children, which suggests that EV71 infection may be associated with a poorer prognosis.

The Current Status of the Disease Caused by Enterovirus 71 Infections: Epidemiology, Pathogenesis, Molecular Epidemiology, and Vaccine Development

Enterovirus 71 (EV71) infections have a major public health impact in the Asia-Pacific region. We reviewed the epidemiology, pathogenesis, and molecular epidemiology of EV71 infection as well as EV71 vaccine development. Previous studies were found using the search terms "enterovirus 71" and "epidemiology" or "pathogenesis" or "molecular epidemiology" or "vaccine" in Medline and PubMed. Articles that were not published in the English language, manuscripts without an abstract, and opinion articles were excluded from the review. The reported epidemiology of cases caused by EV71 infection varied from country to country; seasonal variations in incidence were observed. Most cases of EV71 infection that resulted in hospitalization for complications occurred in children less than five years old. The brainstem was the most likely major target of EV71 infection. The emergence of the EV71 epidemic in the Asia-Pacific region has been associated with the circulation of different genetic lineages (genotypes B3, B4, C1, C2, and C4) that appear to be undergoing rapid evolutionary changes. The relationship between the gene structure of the EV71 virus and the factors that ensure its survival, circulation, and evasion of immunity is still unknown. EV71 infection has emerged as an important global public health problem. Vaccine development, including the development of inactivated whole-virus live attenuated, subviral particles, and DNA vaccines, has been progressing.

Association of Chemotactic Chemokine Ligand 5 Polymorphisms with the Risk of Developing Severe Enterovirus 71 Infection

Respiratory damage is a main manifestation of severe Enterovirus 71 (EV71) infection. Polymorphisms of -403G/A (rs2107538), -28C/G (rs2280788), and In1.1T/C (rs2280789) in chemotactic chemokine ligand 5 (CCL5) have linked with many respiratory diseases. In this study, we explored the possible correlation of CCL5 polymorphisms with severe EV71 infection. Blood samples were obtained from 87 children hospitalized for EV71 infection. Fifty-seven healthy children were enrolled as asymptomatic controls. Genotype and allele frequencies were analyzed by logistic regression analysis. There were statistically significant differences in polymorphisms of CCL5 -403G/A and In1.1T/C for dominant model (P = 0.016; P = 0.027) and additive model (P = 0.010; P = 0.019) between patients with severe EV71 infection and asymptomatic controls. With ordinal logistic regression model analysis, statistically significant differences were found between polymorphisms of CCL5 (-403G/A) (P = 0.034) with the severity of EV71 infection after adjusting for age. The frequency of A-C-C haplotype was significantly higher in EV71 infection patients than controls (P = 0.032). These results suggest that CCL5 -403G/A and In1.1T/C polymorphisms may contribute to severe EV71 infection and individuals with haplotype of A-C-C may exhibit higher risk of developing severe EV71 infection. These findings may provide insights into pathogenic and protective mechanisms of severe EV71 infection.

Immunologic Characterization of Cytokine Responses to Enterovirus 71 and Coxsackievirus A16 Infection in Children

Viral encephalitis is a serious complication of hand, foot, and mouth disease (HFMD), but characteristics of cytokines response in enterovirus 71 (EV-71) and/or coxsackievirus A16 (CV-A16) associated HFMD with or without viral encephalitis remained unclear.We performed a multigroup retrospective study and compared the serum cytokines concentrations among 16 encephalitis patients infected with EV-71 and CV-A16, 24 encephalitis patients with single EV-71 infection, 34 mild HFMD patients with EV-71 infection, 18 mild HFMD patients with CV-A16 infection, and 39 healthy control subjects.Serum levels of interleukin (IL)-4, IL-5, IL-22, and IL-23 were significantly higher in encephalitis patients than in HFMD-alone patients when adjusting for age and sex; IL-2, tumor necrosis factor (TNF)-α, IL-4, IL-22, and IL-1β were significantly higher in HFMD-alone patients of EV-71 infection than in CV-A16 infected HFMD patients; cerebrospinal fluid level of IL-6 was lower in the EV-71/CV-A16 associated encephalitis than that in the EV-71 alone associated encephalitis patients.Over or low expression of the cytokines cascade in HFMD patients appears to play an important role in the elicitation of the immune response to EV-71 and CV-A16. These data will be used to define a cytokine profile, which might help to recognize HFMD patients with the high risk of developing encephalitis.

Recombinant adeno-vaccine expressing enterovirus 71-like particles against hand, foot, and mouth disease

Enterovirus 71 (EV71) and coxsackieviruses (CV) are the major causative agents of hand, foot and mouth disease (HFMD). There is not currently a vaccine available against HFMD, even though a newly developed formalin-inactivated EV71 (FI-EV71) vaccine has been tested in clinical trial and has shown efficacy against EV71. We have designed and genetically engineered a recombinant adenovirus Ad-EVVLP with the EV71 P1 and 3CD genes inserted into the E1/E3-deleted adenoviral genome. Ad-EVVLP were produced in HEK-293A cells. In addition to Ad-EVVLP particles, virus-like particles (VLPs) formed from the physical association of EV71 capsid proteins, VP0, VP1, and VP3 expressed from P1 gene products. They were digested by 3CD protease and confirmed to be produced by Ad-EVVLP-producing cells, as determined using transmission electron microscopy and western blotting. Mouse immunogenicity studies showed that Ad-EVVLP-immunized antisera neutralized the EV71 B4 and C2 genotypes. Activation of VLP-specific CD4+ and CD8+/IFN-γ T cells associated with Th1/Th2-balanced IFN-ɣ, IL-17, IL-4, and IL-13 was induced; in contrast, FI-EV71 induced only Th2-mediated neutralizing antibody against EV71 and low VLP-specific CD4+ and CD8+ T cell responses. The antiviral immunity against EV71 was clearly demonstrated in mice vaccinated with Ad-EVVLP in a hSCARB2 transgenic (hSCARB2-Tg) mouse challenge model. Ad-EVVLP-vaccinated mice were 100% protected and demonstrated reduced viral load in both the CNS and muscle tissues. Ad-EVVLP successfully induced anti-CVA16 immunities. Although antisera had no neutralizing activity against CVA16, the 3C-specific CD4+ and CD8+/IFN-γ T cells were identified, which could mediate protection against CVA16 challenge. FI-EV71 did not induce 3C-mediated immunity and had no efficacy against the CVA16 challenge. These results suggest that Ad-EVVLP can enhance neutralizing antibody and protective cellular immune responses to prevent EV71 infection and cellular immune responses against CV infection.

A Potent Virus-Specific Antibody-Secreting Cell Response to Acute Enterovirus 71 Infection in Children

BACKGROUND

Enterovirus 71 (EV71) remains a leading pathogen for acute infectious diseases in children, especially in Asia. The cellular basis for establishing a virus-specific antibody response to acute EV71 infections is unclear in children.

METHODS

We studied the magnitude of virus-specific antibody-secreting B cells (ASCs) and its relationship with serological response, clinical parameters, and virological parameters among children with laboratory-confirmed EV71 infection.

RESULTS

A potent EV71 genogroup B- and virus-specific ASC response was detected in the first week of illness among genotype B5 EV71-infected children. The cross-reactive EV71-specific ASC response to genogroup C viral antigens composed about 10% of the response. The EV71-specific ASC response in children aged ≥3 years produced immunoglobulin G predominantly, but immunoglobulin M was predominant in younger children. Proliferation marker was expressed by the majority of circulating ASCs in the acute phase of EV71 infection. Virus-specific ASC responses significantly correlated with throat viral load, fever duration, and serological genogroup-specific neutralization titer.

CONCLUSIONS

The presence of a virus-specific ASC response serves an early cellular marker of an EV71-specific antibody response. Further detailed study of EV71-specific ASCs at the monoclonal level is crucial to delineate the specificity and function of antibody immunity in children.

Risk factors for critical disease and death from hand, foot and mouth disease

BACKGROUND

There has been a high mortality and morbidity rate of critical and fatal patients from hand, foot and mouth disease (HFMD) in China in recent. Causes for development of critical and fatal disease remain unclear.

METHODS

We performed a case-control study to assess the association between use of drugs and development of critical disease and death from HFMD.

RESULTS

We found that glucocorticoids treatment was associated with a greater incidence of severe HFMD, whereas andrographolides treatment was associated with a protective effect when they are used for treatment within 48 hours after onset or before being diagnosed as critical.

CONCLUSIONS

We recommend that glucocorticoids should not be used for mild HFMD and andrographolides should undergo clinical trials for treatment of enterovirus 71 infections.

Delivery of human EV71 receptors by adeno-associated virus increases EV71 infection-induced local inflammation in adult mice

Enterovirus71 (EV71) is now recognized as an emerging neurotropic virus in Asia and one major causative agent of hand-foot-mouth diseases (HFMD). However potential animal models for vaccine development are limited to young mice. In this study, we used an adeno-associated virus (AAV) vector to introduce the human EV71 receptors P-selectin glycoprotein ligand-1 (hPSGL1) or a scavenger receptor class-B member-2 (hSCARB2) into adult ICR mice to change their susceptibility to EV71 infection. Mice were administered AAV-hSCARB2 or AAV-hPSGL1 through intravenous and oral routes. After three weeks, expression of human SCARB2 and PSGL1 was detected in various organs. After infection with EV71, we found that the EV71 viral load in AAV-hSCARB2- or AAV-hPSGL1-transduced mice was higher than that of the control mice in both the brain and intestines. The presence of EV71 viral particles in tissues was confirmed using immunohistochemistry analysis. Moreover, inflammatory cytokines were induced in the brain and intestines of AAV-hSCARB2- or AAV-hPSGL1-transduced mice after EV71 infection but not in wild-type mice. However, neurological disease was not observed in these animals. Taken together, we successfully infected adult mice with live EV71 and induced local inflammation using an AAV delivery system.

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.

Dominant CD4-dependent RNA-dependent RNA polymerase-specific T-cell responses in children acutely infected with human enterovirus 71 and healthy adult controls

Human enterovirus 71 (EV71) is one of the major causes of hand, foot and mouth disease (HFMD), which leads to significant mortality in infected children. A prophylactic vaccine is urgently needed. However, little is known about the protective T-cell immunity in individuals infected with the EV71 virus. In this study, we performed a comprehensive ex vivo interferon-γ ELISPOT analysis in 31 children infected with EV71 as well as in 40 healthy adult controls of the CD4(+) and CD8(+) T-cell responses to overlapping peptides spanning the VP1 structural protein and RNA-dependent RNA polymerase (RdRp) non-structural protein. EV71-specific CD4 T-cell responses were detected in most of the acute patients and were mostly CD4-dependent RdRp-specific responses. CD8-dependent VP1 and RdRp-specific responses were also detected in a small proportion of recently infected children. There was no significant association between the strength of the T-cell responses and disease severity observed during the acute EV71 infection phase. Interestingly, an RdRp-specific, but no VP1-specific, CD4-dependent T-cell response was detected in 30% of the adult controls, and no T-cell responses were detected in healthy children. In addition, 24 individual peptides containing potential T-cell epitope regions were identified. The data suggest that CD4-dependent RdRp-specific T-cell responses may play an important role in protective immunity, and the epitopes identified in this study should provide valuable information for future therapeutic and prophylactic vaccine design as well as basic research.

Seroepidemiology and molecular epidemiology of enterovirus 71 in Russia

Enterovirus 71 (EV71) is an emerging human pathogen causing massive epidemics of hand, foot and mouth disease with severe neurological complications in Asia. EV71 also circulates in Europe, however it does not cause large outbreaks. The reason for distinct epidemiological patterns of EV71 infection in Europe and Asia and the risk of EV71 epidemic in Europe and Russia remain unknown. Seroepidemiology of EV71 and molecular epidemiology of occasional EV71 isolates were studied to explore circulation of EV71 in Russia. In six regions of Russian Federation, seroprevalence of EV71 in sera collected in 2008 ranged from 5% to 20% in children aged 1-2 years and from 19% to 83% in children aged 3-5 years. The seroprevalence among elder children was significantly higher (41-83% vs. 19-27%) in Asian regions of Russia. EV71 strains identified in Russia in 2001-2011 belonged to subtypes C1 and C2, while genotype C4 that was causing epidemics in Asia since 1998 emerged in 2009 and became dominant in 2013.

A polymorphism in melanoma differentiation-associated gene 5 may be a risk factor for enterovirus 71 infection

Enterovirus 71 (EV71) infection has a wide variety of clinical manifestations, from no symptoms to fatal disease. Host immune response may be a determinant of disease severity. We investigated the association of polymorphisms in three pattern recognition receptor (PRR) genes-toll-like receptor 3 (TLR3) (rs3775291), retinoic acid-inducible gene I (RIG-I) (rs10813831) and melanoma differentiation-associated gene 5 (MDA5) (rs1990760)-with the severity of EV71 infection. Polymorphisms of candidate genes in 87 EV71-infected patients and 57 asymptomatic controls were detected. Binary logistic regression analysis revealed statistically significant differences in polymorphism of MDA5 (rs1990760) between patients with severe EV71 infection and asymptomatic controls in an additive model (OR 0.424, 95% CI 0.213-0.845, p 0.015) and a dominant model (OR 0.256, 95% CI 0.103-0.635, p 0.003). Polymorphism of MDA5 (rs1990760) (OR 0.399, 95% CI 0.199-0.798, p 0.009) was found to be associated with the severity of EV71 infection with the analysis of ordinal logistic regression. These results indicated the association between MDA5 (rs1990760) polymorphism and an increased risk of a severe EV71 infection in Chinese children, which offers potential for investigating the innate immune mechanism of EV71 infection and identifying at-risk infants, for whom a preventive strategy may reduce the severity of EV71 infection.

A novel finding for enterovirus virulence from the capsid protein VP1 of EV71 circulating in mainland China

Enterovirus 71 (EV71) is a neurotropic virus that causes various clinical manifestations in young children, ranging from asymptomatic to fatal. Different pathotypes of EV71 notably differ in virulence. Several virulence determinants of EV71 have been predicted. However, these reported virulence determinants could not be used to identify the EV71 strains of subgenotype C4, which mainly circulate in China. In this study, VP1 sequences of 37 EV71 strains from severe cases (SC-EV71) and 192 EV71 strains from mild cases (MC-EV71) in mainland China were analyzed to determine the potential virulence determinants in the capsid protein VP1 of EV71. Although most SC-EV71 strains belonged to subgenotype C4a, no specific genetic lineages in C4a were correlated with EV71 virulence. Interestingly, amino acid substitutions at nine positions (H22Q, P27S, N31S/D, E98K, E145G/Q, D164E, T240A/S, V249I, and A289T) were detected by aligning the VP1 sequences of the SC-EV71 and MC-EV71 strains. Moreover, both the constituent ratios of the conservative or mutated residues in the MC-EV71 and SC-EV71 strains and the changes in the VP1 3D structure resulting from these mutations confirmed that the conservative residues (22H, 249V, and 289A) and the mutated residues (27S, 31S/D, 98K, 145G/Q, 164E, and 240A/S) might be potential virulence determinants in VP1 of EV71. Furthermore, these results led to the hypothesis that VP1 acts as a sandwich switch for viral particle stabilization and cellular receptors attachment, and specific mutations in this protein can convert mild cases into severe cases. These findings highlight new opportunities for diagnostic and therapeutic interventions.

Association of functional polymorphisms in the MxA gene with susceptibility to enterovirus 71 infection

Myxovirus resistance A (MxA) is an antiviral protein induced by type I interferons α and β (IFN-α and IFN-β) that can inhibit virus replication. We examined whether the MxA polymorphisms were related to the risk and severity of enterovirus 71 (EV71) infection in Chinese populations. The MxA C-123A and G-88T polymorphisms were genotyped in two independent case–control populations in China by polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP) analysis. Multivariate logistic regression analysis was used to calculate adjusted odds ratios (ORs) and 95 % confidence intervals (95 % CIs). MxA messenger RNA was quantified by real-time quantitative PCR in peripheral blood mononuclear cells (PBMCs) from 45 healthy children and 19 patients with EV71 infection. Significantly decreased susceptibility to EV71 infection was observed for the -123A allele and -88T allele carriers, with ORs (95 % CIs) estimated as 0.56 (0.39–0.81) and 0.64 (0.47–0.88), respectively, in the northern population. This association was confirmed in the southern population, with ORs (95 % CIs) estimated as 0.58 (0.38–0.89) and 0.67(0.47–0.95), respectively. The A_-123T_-88 haplotype was also significantly associated with lower risk of EV71 infection in both the northern (OR = 0.62; 95 % CI = 0.44–0.85) and the southern population (OR = 0.63; 95 % CI = 0.43–0.92). Furthermore, we observed higher MxA messenger RNA levels in IFNβ1a-stimulated PBMCs from the -123A or -88T allele carriers compared with that from nocarriers. Our findings suggest that polymorphisms in the MxA promoter may play a role in mediating the susceptibility to EV71 infection in Chinese population.

VP2 dominated CD4+ T cell responses against enterovirus 71 and cross-reactivity against coxsackievirus A16 and polioviruses in a healthy population

Enterovirus 71 (EV71)-associated hand-foot-mouth disease has become a major threat to public health in the Asia-Pacific region. Although T cell immunity is closely correlated with clinical outcomes of EV71 infection, little is known about T cell immunity baseline against EV71 and T cell immunogenecity of EV71 Ags in the population, which has restricted our understanding of immunoprotection mechanisms. In this study, we investigated the cellular immune responses against the four structural Ags of EV71 and determined the immunohierarchy of these Ags in healthy adults. A low frequency of EV71-responsive T cells was detected circulating in peripheral blood, and broad T cell immune responses could be identified in most of the subjects after in vitro expansion. We demonstrated that the VP2 Ag with broad distribution of immunogenic peptides dominates T cell responses against EV71 compared with VP1, VP3, and VP4. Furthermore, the responses were illuminated to be mainly single IFN-γ-secreting CD4(+) T cell dependent, indicating the previous natural acute viral infection of the adult population. Conservancy analysis of the immunogenic peptides revealed that moderately variant peptides were in the majority in coxsackievirus A16 (CV-A16) whereas most of the peptides were highly variant in polioviruses. Less efficient cross-reactivity against CV-A16 might broadly exist among individuals, whereas influences derived from poliovirus vaccination would be limited. Our findings suggest that the significance of VP2 Ag should be addressed in the future EV71-responsive immunological investigations. And the findings concerning the less efficient cross-reactivity against CV-A16 and limited influences from poliovirus vaccination in EV71-contacted population would contribute to a better understanding of immunoprotection mechanisms against enteroviruses.

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.

lncRNA expression signatures in response to enterovirus 71 infection

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

Seroepidemiology of human enterovirus71 and coxsackievirusA16 in Jiangsu province, China

Background

The major etiology of hand, foot and mouth disease (HFMD) is infection with human enterovirus A (HEV-A). Among subtypes of HEV-A, coxsackievirusA16 (CoxA16) and enterovirus 71 (EV71) are major causes for recurrent HFMD among infants and children in Jiangsu Province, mainland China. Here, we analyzed maternal antibodies between prenatal women and their neonates, to determine age-specific seroprevalence of human EV71 and CoxA16 infections in infants and children aged 0 to 15 years. The results may facilitate the development of immunization against HFMD.

Methods

This study used cross-section of 40 pairs of pregnant women and neonates and 800 subjects aged 1 month to 15 years old. Micro-dose cytopathogenic effects measured neutralizing antibodies against EV71 and CoxA16. Chi-square test compared seroprevalence rates between age groups and McNemar test, paired-Samples t-test and independent-samples t-test analyzed differences of geometric mean titers.

Results

A strong correlation between titers of neutralizing antibody against EV71 and CoxA16 in prenatal women and neonates was observed (r_EV71 = 0.67, r_CoxA16 = 0.56, respectively, p < 0.05). Seroprevalence rates of anti-EV71 antibody gradually decreased with age between 0 to 6 months old, remained low between 7 to 11 months (5.0–10.0%), and increased between 1 and 4 years (22.5–87.5%). Age-specific seroprevalence rates of anti-EV71 antibody stabilized in >80% of children between 5 to 15 years of age. However, seroprevalence rates of anti-CoxA16 antibody were very low (0.0–13.0%) between 0 to 6 months of age, gradually increased between 7 months to 4 years (15.0–70.0%), and stabilized at 54.0% (108/200) between 5 to 15 years. Seroprevalence rates against EV71 and CoxA16 were low under 1 year (0.0–10.0%), and showed an age dependent increase with high seroprevalence (52.5–62.5%) between 4 and10 years of age.

Conclusions

Concomitant infection of EV71 and CoxA16 was common in Jiangsu Province. Therefore, development of bivalent vaccine against both EV71 and CoxA16 is critical. The optimal schedule for vaccination may be 4 to11 months of age.

A pilot study on cytotoxic T lymphocyte-4 gene polymorphisms in urinary schistosomiasis

Urinary schistosomiasis is caused by the digenetic trematode Schistosoma haematobium, characterized by accumulation of eggs in the genitourinary tract. Cytotoxic T-lymphocyte antigen 4 (CTLA-4) can play an important role in parasitic infection due to its major role as a negative regulator of T-cell activation and proliferation. This study was performed in patients with schistosomiasis and healthy controls to analyze the allele and genotype frequencies of four CTLA-4 gene polymorphisms. The CTLA-4 gene was amplified using Taqman real-time polymerase chain reaction, and allele and genotypes of 49 patients with schistosomiasis were analyzed using allelic discrimination analysis followed by subsequent direct sequencing. The results were compared with healthy control subjects. The frequencies of CTLA-4 rs733618 A allele at position -1722 (p=0.001), rs11571316 C allele at position -1577 (p<0.001), and rs231775 A allele at position +49 (p=0.002) in the patient group were significantly higher than the control group. The rs733618 AA genotype (p=0.001), rs11571316 CC genotype (p<0.001), and rs231775 AA genotype (p=0.007) were also significantly overrepresented. Meanwhile, rs733618 AG genotype (p=0.001), rs11571316 CT genotype (p=0.02), and rs231775 GG genotype (p=0.029) were significantly decreased in the patients with schistosomiasis, as compared with the controls. No significant difference was observed in both allele and genotype of rs16841252. The results of this study suggest that the rs733618, rs11571316, and rs231775 polymorphisms in the CTLA-4 gene may influence susceptibility to schistosomiasis infection in the Gabonese children.

Association of interleukin 10 and interferon gamma gene polymorphisms with enterovirus 71 encephalitis in patients with hand, foot and mouth disease

Enterovirus 71 (EV71) is one of the common causative agents of hand, foot and mouth disease (HFMD), and is associated with several outbreaks with neurological complications including encephalitis. This study investigated the polymorphisms of interferon gamma (IFN-γ)+874 T/A and interleukin 10 (IL-10)-1082 G/A in 65 Chinese patients with EV71 encephalitis and 113 Chinese HFMD patients without complications. The polymorphisms of IFN-γ+874 T/A and IL-10-1082 G/A were determined by polymerase chain reaction (PCR)-amplification refractory mutation system (ARMS) and PCR-sequence-specific primer (SSP) analysis, respectively. The IFN-γ + 874 A allele was observed with significantly greater frequency in patients with EV71 encephalitis (76.2%) compared with HFMD patients without complications (61.1%, p < 0.01). Similarly, the IL-10 - 1082 A allele was observed with significantly greater frequency in patients with EV71 encephalitis (86.2%) compared with HFMD patients without complications (77.0%, p < 0.05). IFN-γ + 874 A and IL-10 - 1082 A alleles are associated with susceptibility to EV71 encephalitis in Chinese patients.

A non-mouse-adapted enterovirus 71 (EV71) strain exhibits neurotropism, causing neurological manifestations in a novel mouse model of EV71 infection

Enterovirus 71 (EV71) is a neurotropic pathogen that has been consistently associated with the severe neurological forms of hand, foot, and mouth disease. The lack of a relevant animal model has hampered our understanding of EV71 pathogenesis, in particular the route and mode of viral dissemination. It has also hindered the development of effective prophylactic and therapeutic approaches, making EV71 one of the most pressing public health concerns in Southeast Asia. Here we report a novel mouse model of EV71 infection. We demonstrate that 2-week-old and younger immunodeficient AG129 mice, which lack type I and II interferon receptors, are susceptible to infection with a non-mouse-adapted EV71 strain via both the intraperitoneal (i.p.) and oral routes of inoculation. The infected mice displayed progressive limb paralysis prior to death. The dissemination of the virus was dependent on the route of inoculation but eventually resulted in virus accumulation in the central nervous systems of both animal groups, indicating a clear neurotropism of the virus. Histopathological examination revealed massive damage in the limb muscles, brainstem, and anterior horn areas. However, the minute amount of infectious viral particles in the limbs from orally infected animals argues against a direct viral cytopathic effect in this tissue and suggests that limb paralysis is a consequence of EV71 neuroinvasion. Together, our observations support that young AG129 mice display polio-like neuropathogenesis upon infection with a non-mouse-adapted EV71 strain, making this mouse model relevant for EV71 pathogenesis studies and an attractive platform for EV71 vaccine and drug testing.

Significant elevation of B cells at the acute stage in enterovirus 71-infected children with central nervous system involvement

A feature of the large outbreak of human enterovirus 71 (EV71)-associated hand-foot-and-mouth (HFMD) disease in China in 2008 was that severe cases presented with encephalitis. This study was performed to evaluate the immunophenotypic characteristics of patients with neurological involvement. Twenty-one patients with encephalitis and 14 with uncomplicated HFMD were recruited. Age-matched healthy volunteers were enrolled as controls. Peripheral lymphocyte subsets were analyzed by use of 3-colour flow cytometry, and the quantitative determination of plasma immunoglobulin (Ig) levels was also monitored. Comparisons between severe and mild cases demonstrated significant elevations of B cells and IgG levels and corresponding general decreases in natural killer (NK) cells and T lymphocytes in severe cases at the acute stage of infection (p < 0.01 for all). During the convalescent phase, rapid recoveries of B cells and IgG to the normal levels were observed, which appeared to be accompanied by an increase in EV71-specific neutralizing antibody titres. In summary, our data demonstrate that elevated B cells and IgG might be associated with neurological manifestations in EV71 infection.

Virology, epidemiology, pathogenesis, and control of enterovirus 71

First isolated in California, USA, in 1969, enterovirus 71 (EV71) is a major public health issue across the Asia-Pacific region and beyond. The virus, which is closely related to polioviruses, mostly affects children and causes hand, foot, and mouth disease with neurological and systemic complications. Specific receptors for this virus are found on white blood cells, cells in the respiratory and gastrointestinal tract, and dendritic cells. Being an RNA virus, EV71 lacks a proofreading mechanism and is evolving rapidly, with new outbreaks occurring across Asia in regular cycles, and virus gene subgroups seem to differ in clinical epidemiological properties. The pathogenesis of the severe cardiopulmonary manifestations and the relative contributions of neurogenic pulmonary oedema, cardiac dysfunction, increased vascular permeability, and cytokine storm are controversial. Public health interventions to control outbreaks involve social distancing measures, but their effectiveness has not been fully assessed. Vaccines being developed include inactivated whole-virus, live attenuated, subviral particle, and DNA vaccines.

Combined peptides of human enterovirus 71 protect against virus infection in mice

Human enterovirus 71 (EV71) is a cause of hand, foot and mouth disease (HMFD) in children under 6 years old, and could cause serious neurological complications in some patients. Numerous large outbreaks of EV71 caused HMFD have occurred recently in Asia, especially in China. The cross-reactivity of EV71 with human brain tissue was observed and the cross-reactivity inducing regions were identified in previously study, which suggested that there were two regions in structural proteins of virus should be avoided in the vaccine. Six peptides without cross-reactivity were selected and combined into three vaccine candidates and applied in further evaluation in neonatal mice. The Vac6 comprising the peptides of P(70-159), P(140-249), P(324-443) and P(746-876) of the structural proteins could provide effective protection on pups against virus infection, as shown in viral copies detection and histopathology examination. Immunohistochemical staining results indicated that Vac6 had no cross-reactivity with human brain tissues. Our results suggested that Vac6 could have potential clinical value against EV71 epidemics caused mainly by C4 strains in the mainland of China.

Recent advances in research on human enterovirus 71

Over the past decade, Human enterovirus (HEV)71 has emerged as a highly significant cause of viral encephalitis in the south-east Asian region. A pattern of increased epidemic activity has been observable since 1997, the cause of which is unclear. Ongoing investigations into the molecular basis of HEV71 infection and virulence, in particular viral translation and replication, have confirmed similarities between HEV71 and other enteroviruses, including the prototype species Poliovirus, but more work is required in this field. Although several putative receptors for HEV71 have been identified, it remains likely that other, as yet unidentified, receptors exist. Work in several established animal models for HEV71 infection has confirmed the protective efficacy of several inactivated vaccines. As more information emerges regarding the molecular processes involved in HEV71 infection, further advances may lead to the development of more effective antiviral treatments and, ultimately, a vaccine protection strategy.

Glucocorticoid and pyrazolone treatment of acute fever is a risk factor for critical and life-threatening human enterovirus 71 infection during an outbreak in China, 2008

BACKGROUND

Human enterovirus 71 (HEV71) causes outbreaks of life-threatening diseases throughout the world. The genesis of these severe diseases is unknown.

METHODS

During an outbreak of HEV71 infection, we investigated risk factors for critical illness. We developed a modified pediatric index of mortality (mPIM) incorporating heart rate, temperature, white blood cell count, respiratory rate, chest infiltrates, skin color, reflexes, responsiveness, and mobility. We calculated the mPIM for 103 patients (22 deaths) using complete scoring criteria in the medical record. In a case-control study, we compared cases (mPIM > or =10 or death) with controls (mPIM = 0-9) by drugs received within 96 hours after onset of fever, initial temperature, age, and nutritional anthropometry.

RESULTS

About 66% (68/103) of the patients with an mPIM score (28 cases and 40 controls) had data on initial exposures. About 50% of the 28 cases and 18% of the 40 controls received an injection to treat fever during the first 96 hours after onset (Odds ratio [OR] = 7.0, 95% confidence interval [CI]: 1.8-28). Injections containing exclusively glucocorticoids (OR = 4.8, 95% CI: 1.2-21) or pyrazolones (OR = 4.1, 95% CI: 0.91-19, P = 0.047) were risk factors for severe HEV71 infection. About 25% of cases and 5% of controls received both drugs parenterally while 7% of cases and 30% of controls received neither (OR = 21, 95% CI: 1.8-305). Conversely, cases and controls had identical average initial temperature, and did not differ significantly by age, sex, nutritional measurements, use of other drugs, or timeliness of medical care received.

CONCLUSION

Fever treatment with glucocorticoids and/or pyrazolones is a risk factor for life-threatening HEV71 infection.

Clinical and etiological characteristics of enterovirus 71-related diseases during a recent 2-year period in Korea

Human enterovirus 71 (EV 71) has caused large-scale outbreaks of hand-foot-and-mouth disease (HFMD), particularly in the Asian-Pacific region. In this study, we report a major outbreak of EV 71 infection in Korea and describe the clinical differences between EV 71 and non-EV 71 enterovirus infections. We prospectively enrolled patients with suspected viral infections during a recent 2-year period through a nationwide surveillance system. We identified 719 patients with suspected HFMD or herpangina using real-time PCR and genotyping based on VP1 sequence analysis. The major pathogen causing HFMD changed substantially from 2008 to 2009, with EV 71 becoming the most common cause of HFMD in Korea in 2009. We successfully identified the enteroviral genotypes for 218 of the 719 patients. Patients with EV 71 infections tended to be younger than those with non-EV 71 enteroviral infections and presented with HFMD and meningoencephalitis. In addition, the occurrence of fever, headache, and neck stiffness was significantly higher in patients with EV 71 infections. Multivariable analysis showed that for patients presenting with HFMD, fever, or a sore throat, each covariate was independently associated with EV 71 infection; the adjusted odds ratios (with 95% confidence intervals in parentheses) for these variables were 31.86 (10.04 to 101.09), 4.76 (1.71 to 13.25), and 0.18 (0.04 to 0.77), respectively. Our results indicate that EV 71 was a major cause of HFMD in Korea during the study period. In addition, we found that clinical symptoms may be helpful in the early identification of patients with EV 71 infections.

An emerging recombinant human enterovirus 71 responsible for the 2008 outbreak of hand foot and mouth disease in Fuyang city of China

Hand, foot and mouth disease (HFMD), a common contagious disease that usually affects children, is normally mild but can have life-threatening manifestations. It can be caused by enteroviruses, particularly Coxsackieviruses and human enterovirus 71 (HEV71) with highly variable clinical manifestations. In the spring of 2008, a large, unprecedented HFMD outbreak in Fuyang city of Anhui province in the central part of southeastern China resulted in a high aggregation of fatal cases. In this study, epidemiologic and clinical investigations, laboratory testing, and genetic analyses were performed to identify the causal pathogen of the outbreak. Of the 6,049 cases reported between 1 March and 9 May of 2008, 3023 (50%) were hospitalized, 353 (5.8%) were severe and 22 (0.36%) were fatal. HEV71 was confirmed as the etiological pathogen of the outbreak. Phylogenetic analyses of entire VP1 capsid protein sequence of 45 Fuyang HEV71 isolates showed that they belong to C4a cluster of the C4 subgenotype. In addition, genetic recombinations were found in the 3D region (RNA-dependent RNA polymerase, a major component of the viral replication complex of the genome) between the Fuyang HEV71 strain and Coxsackievirus A16 (CV-A16), resulting in a recombination virus. In conclusion, an emerging recombinant HEV71 was responsible for the HFMD outbreak in Fuyang City of China, 2008.

Human enterovirus 71 and hand, foot and mouth disease

Hand, foot and mouth disease (HFMD) is generally a benign febrile exanthematous childhood disease caused by human enteroviruses. The route of transmission is postulated to be faeco-oral in developing areas but attributed more to respiratory droplet in developed areas. Transmission is facilitated by the prolonged environmental survival of these viruses and their greater resistance to biocides. Serious outbreaks with neurological and cardiopulmonary complications caused by human enterovirus 71 (HEV-71) seem to be commoner in the Asian Pacific region than elsewhere in the world. This geographical predilection is unexplained but could be related to the frequency of intra- and inter-typic genetic recombinations of the virus, the host populations' genetic predisposition, environmental hygiene, and standard of healthcare. Vaccine development could be hampered by the general mildness of the illness and rapid genetic evolution of the virus. Antivirals are not readily available; the role of intravenous immunoglobulin in the treatment of serious complications should be investigated. Monitoring of this disease and its epidemiology in the densely populated Asia Pacific epicentre is important for the detection of emerging epidemics due to enteroviruses.

Enterovirus 71: epidemiology, pathogenesis and management

Enterovirus 71 (EV71) has emerged as a major cause of neurological threat in the world following the eradication of poliovirus. Most EV71 infections commonly result in hand-foot-mouth disease or herpangina, and some cases are associated with brainstem encephalitis and acute flaccid paralysis. Mortality was high in EV71 brainstem encephalitis complicated with pulmonary edema, particularly in children below 5 years of age. Destruction of vasomotor in the brainstem by EV71 produces autonomic nervous system dysregulation prior to the pulmonary edema. The pulmonary edema is the result of increased pulmonary vascular permeability caused by the direct brainstem lesions and/or a systemic inflammatory response syndrome produced by the release of cytokines and chemokines. There is currently no specific antiviral agent to treat or vaccine to prevent EV71 diseases. Treating severe EV71 brainstem encephalitis patients with intravenous IgG and milrinone is associated with significantly decreased mortality by attenuated sympathetic activity and cytokine production.

Diseases caused by enterovirus 71 infection

The purpose of this review was to explore the epidemiology, pathogenesis, virology, and management of enterovirus 71 (EV71) infection. Published literature was surveyed by Medline using the keyword "EV71." The reported incidence of cases of hand-foot-mouth disease/herpangina varied from year to year; seasonal variations in incidence were observed, with a peak in incidence during the summer season. Most cases of hand-foot-mouth disease/herpangina hospitalized for complications occurred in children less than 5 years old. The brainstem was the most likely major target of EV71 infection. Different enteroviruses cocirculate in the community annually. The emergence of the EV71 epidemic in the Asia Pacific region has been associated with the circulation of 5 genetic lineages (genotypes B3, B4, C1, C2, C4) that appear to be undergoing rapid evolutionary changes. The relationship between the gene structure of the EV71 virus and the factors that ensure its survival, ease of transmission, and evasion of immunity is still unclear. EV71 central nervous system involvement causes serious clinical illness, death, and long-term neurologic and psychiatric disorders in young children. EV71 infection has emerged as an important public health problem. Vaccine development is recommended for the prevention of EV71 infection in the future.

Sialylated glycans as receptor and inhibitor of enterovirus 71 infection to DLD-1 intestinal cells

Background

Many viruses recognize specific sugar residues, particularly sulfated or sialylated glycans, as the infection receptors. A change of sialic acid (2-6)-linked galactose (SA-α2,6Gal) to SA-α2,3Gal determines the receptor for avian flu infection. The receptor for enterovirus 71 (EV71) infection that frequently causes fatal encephalitis in Asian children remains unclear. Currently, there is no effective vaccine or anti-virus agent for EV71 infection. Using DLD-1 intestinal cells, this study investigated whether SA-linked glycan on DLD-1 intestinal cells was a receptor for EV71, and whether natural SA-linked sugars from human milk could block EV71 infection.

Results

EV71 specifically infected DLD-1 intestinal cells but not K562 myeloid cells. Depletion of O-linked glycans or glycolipids, but not N-linked glycans, significantly decreased EV71 infection of DLD-1 cells. Pretreatment of DLD-1 cells with sialidase (10 mU, 2 hours) significantly reduced 20-fold EV71 replication (p < 0.01). Taken together, these results suggest that SA-linked O-glycans and glycolipids, but not N-glycans, on DLD-1 cells were responsible for EV71 infection. Purified SA-α2,3Gal and SA-α2,6Gal from human milk significantly inhibited EV71 infection of DLD-1 cells, indicating terminal SA-linked glycans could be receptors and inhibitors of EV71 infection.

Conclusion

This is the first in the literature to demonstrate that EV71 uses SA-linked glycans as receptors for infection, and natural SA-linked glycans from human milk can protect intestinal cells from EV71 infection. Further studies will test how a SA-containing glycan can prevent EV71 in the future.