Fulminant neurogenic pulmonary oedema with hand, foot, and mouth disease

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.

Antiviral effects of two Ganoderma lucidum triterpenoids against enterovirus 71 infection

Enterovirus 71 (EV71) is a major causative agent for hand, foot and mouth disease (HFMD), and fatal neurological and systemic complications in children. However, there is currently no clinical approved antiviral drug available for the prevention and treatment of the viral infection. Here, we evaluated the antiviral activities of two Ganoderma lucidum triterpenoids (GLTs), Lanosta-7,9(11),24-trien-3-one,15;26-dihydroxy (GLTA) and Ganoderic acid Y (GLTB), against EV71 infection. The results showed that the two natural compounds display significant anti-EV71 activities without cytotoxicity in human rhabdomyosarcoma (RD) cells as evaluated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cell proliferation assay. The mechanisms by which the two compounds affect EV71 infection were further elucidated by three action modes using Ribavirin, a common antiviral drug, as a positive control. The results suggested that GLTA and GLTB prevent EV71 infection through interacting with the viral particle to block the adsorption of virus to the cells. In addition, the interactions between EV71 virion and the compounds were predicated by computer molecular docking, which illustrated that GLTA and GLTB may bind to the viral capsid protein at a hydrophobic pocket (F site), and thus may block uncoating of EV71. Moreover, we demonstrated that GLTA and GLTB significantly inhibit the replication of the viral RNA (vRNA) of EV71 replication through blocking EV71 uncoating. Thus, GLTA and GLTB may represent two potential therapeutic agents to control and treat EV71 infection.

Phenotypic and genotypic characteristics of novel mouse cell line (NIH/3T3)-adapted human enterovirus 71 strains (EV71:TLLm and EV71:TLLmv)

Since its identification in 1969, Enterovirus 71 (EV71) has been causing periodic outbreaks of infection in children worldwide and most prominently in the Asia-Pacific Region. Understanding the pathogenesis of Enterovirus 71 (EV71) is hampered by the virus's inability to infect small animals and replicate in their derived in vitro cultured cells. This manuscript describes the phenotypic and genotypic characteristics of two selected EV71 strains (EV71:TLLm and EV71:TLLmv), which have been adapted to replicate in mouse-derived NIH/3T3 cells, in contrast to the original parental virus which is only able to replicate in primate cell lines. The EV71:TLLm strain exhibited productive infection in all primate and rodent cell lines tested, while EV71:TLLmv exhibited greater preference for mouse cell lines. EV71:TLLmv displayed higher degree of adaptation and temperature adaptability in NIH/3T3 cells than in Vero cells, suggesting much higher fitness in NIH/3T3 cells. In comparison with the parental EV71:BS strain, the adapted strains accumulated multiple adaptive mutations in the genome resulting in amino acid substitutions, most notably in the capsid-encoding region (P1) and viral RNA-dependent RNA polymerase (3D). Two mutations, E167D and L169F, were mapped to the VP1 canyon that binds the SCARB2 receptor on host cells. Another two mutations, S135T and K140I, were located in the VP2 neutralization epitope spanning amino acids 136-150. This is the first report of human EV71 with the ability to productively infect rodent cell lines in vitro.

Modeling and preventive measures of hand, foot and mouth disease (HFMD) in China

This paper concentrates on the HFMD data of China from March 2009 to December 2012. We set up a mathematical model to fit those data with the goodness of fit and obtain the optimal parameter values of the model. By the Chi-square test of statistical inference, the optimal parameter values of the model are reasonable. We obtained the basic reproductive number of the disease for each year, and it is larger than 1. Thus, we conclude that HFMD will persist in China under the current conditions, so we investigate the preventive measures to control the HFMD. If the preventive measures proposed in our paper were implemented, HFMD would be controlled quickly and the number of infections would decline rapidly over a period of time.

The gene expression profile of peripheral blood mononuclear cells from EV71-infected rhesus infants and the significance in viral pathogenesis

Enterovirus 71 (EV71) is the major pathogen responsible for fatal hand, foot and mouth disease (HFMD). Our previous work reported on an EV71-infected rhesus monkey infant model that presented with histo-pathologic changes of the central nervous system (CNS) and lungs. This study is focused on the correlated modulation of gene expression in the peripheral blood mononuclear cells (PBMCs) from EV71-infected rhesus monkey infants. The expression of more than 500 functional genes associated with multiple pathways was modulated. The expression of genes associated with immune inflammatory responses was up-regulated during the period from days 4 to 10 post-infection. The expression of two genes (TAC1 and IL17A), which play major roles in inflammatory reactions, was remarkably up-regulated during the infection period. Furthermore, a higher expression level of the TAC1 gene was identified in the CNS compared to the lungs, but a high expression level of the IL-17A gene was observed in the lungs and not in the CNS. The results of this study suggest at least two facts about EV71 infection, which are that: the TAC1 gene that encodes substance P and neurokinin-A is present in both PBMCs and the hypothalamus; and the up-regulation of IL-17A is sustained in the peripheral blood.

Preclinical evaluation of the immunogenicity and safety of an inactivated enterovirus 71 candidate vaccine

Human enterovirus 71 (EV71) is a significant cause of morbidity and mortality from Hand, Foot and Mouth Disease (HFMD) and neurological complications, particularly in young children in the Asia-Pacific region. There are no vaccines or antiviral therapies currently available for prevention or treatment of HFMD caused by EV71. Therefore, the development of therapeutic and preventive strategies against HFMD is of growing importance. We report the immunogenic and safety profile of inactivated, purified EV71 preparations formulated with aluminum hydroxide adjuvant in preclinical studies in mice and rabbits. In mice, the candidate vaccine formulations elicited high neutralizing antibody responses. A toxicology study of the vaccine formulations planned for human use performed in rabbits showed no vaccine-related pathological changes and all animals remained healthy. Based on these preclinical studies, Phase 1 clinical testing of the EV71 inactivated vaccine was initiated.

Autoprocessing: an essential step for expression and purification of enterovirus 71 3C(pro) in Escherichia coli

A gene encoding the 3BC of human enterovirus 71 (EV71) was cloned and inserted into a derivative of plasmid pET-32a(+) driven by T7 promoter. The expressed 3C protease (3C(pro)) autocatalytically cleaved itself from the recombinant protein Trx-3BC and the mature 3C(pro) partitioned in the soluble fraction of bacterial lysate. The 13-amino-acid peptide substrates with the junction of 3B/3C were used to verify the proteolysis activity of the purified 3C(pro). The EV71 3C(pro) had a Km value of 63 μM (measured by a continuous fluorescence assay). The other solid-phase activity assay of the EV71 3C(pro) was developed using HPLC to analyze the proteolytic products. The combination of two activity assays contributes to promote the identification of the specific inhibitors targeted to the EV71 3C(pro).

Enterovirus genotypes causing hand foot and mouth disease in Shanghai, China: a molecular epidemiological analysis

Background

A rapid expansion of hand, foot, and mouth disease (HFMD) outbreaks has occurred and caused deaths in China in recent years, but little is known about the other etiologic agents except enterovirus 71 (EV71) and coxsackievirus A 16 (CA16). The objective of this study is to determine the genotype compositions of enterovirus causing HFMD in Shanghai and identify any associations between enterovirus types and clinical manifestations.

Methods

Stool specimens were collected from patients hospitalized for treatment of HFMD, from May 2010 to April 2011. Enterovirus was detected by reverse transcription PCR and directly genotyped by sequencing the PCR products. Phylogenetic analysis was based on the VP1 partial gene.

Results

Of 290 specimens, 277 (95.5%) tested positive for enterovirus. The major genotypes were EV71 (63.8%), CA10 (9.0%), CA6 (8.3%), CA16 (6.9%), CA12 (2.4%), and CA4 (1.4%). The EV71 strains belonged to the C4a subtype and CA16 belonged to the B subtype. CA6 was closely related to strains detected in Japan, Taiwan and China, and CA10, CA12 and CA4 were phylogenetically similar to other strains circulating in China. Mean hospital stays and the prevalence of complications in patients with EV71 infection were higher than those in patients in CA6, CA10 or CA16 infection (P < 0.05 for all comparisons). Children with CA12 infection were the youngest, and most likely have the highest risk of complications when compared to the other non-EV71 infection groups.

Conclusions

This study demonstrated a diversified pathogen compositions attributing to HFMD and clinical symptoms differing in enterovirus genotypes. It deserves our attention as early identification of enterovirus genotypes is important for diagnosis and treatment of HFMD patients.

Milrinone therapy for enterovirus 71-induced pulmonary edema and/or neurogenic shock in children: a randomized controlled trial

OBJECTIVE

Enterovirus 71-induced brainstem encephalitis with pulmonary edema and/or neurogenic shock (stage 3B) is associated with rapid mortality in children. In a small pilot study, we found that milrinone reduced early mortality compared with historical controls. This prospective, randomized control trial was designed to provide more definitive evidence of the ability of milrinone to reduce the 1-week mortality of stage 3B enterovirus 71 infections.

DESIGN

Prospective, unicenter, open-label, randomized, controlled study.

SETTING

Inpatient ward of a large tertiary teaching hospital in Ho Chi Minh City, Vietnam.

PATIENTS

Children (≤ 18 yr old) admitted with proven enterovirus 71-induced pulmonary edema and/or neurogenic shock.

INTERVENTIONS

Patients were randomly assigned to receive intravenous milrinone (0.5 μg/kg/min) (n = 22) or conventional management (n = 19). Both groups received dopamine or dobutamine and intravenous immunoglobulin.

MEASUREMENTS AND MAIN RESULTS

The primary endpoint was 1-week mortality. The secondary endpoints included length of ventilator dependence and hospital stay and adverse events. The median age was 2 years with a predominance of boys in both groups. The 1-week mortality was significantly lower, 18.2% (4/22) in the milrinone compared with 57.9% (11/19) in the conventional management group (relative risk = 0.314 [95% CI, 0.12-0.83], p = 0.01). The median duration of ventilator-free days was longer in the milrinone treatment group (p = 0.01). There was no apparent neurologic sequela in the survivors in either group, and no drug-related adverse events were documented.

CONCLUSIONS

Milrinone significantly reduced the 1-week mortality of enterovirus 71-induced pulmonary edema and/or neurogenic shock without adverse effects. Further studies are needed to determine whether milrinone might be useful to prevent progression of earlier stages of brainstem encephalitis.

Comparative study of the cytokine/chemokine response in children with differing disease severity in enterovirus 71-induced hand, foot, and mouth disease

Background

Enterovirus 71 (EV71) infection can lead to a rapidly progressing, life-threatening, and severe neurological disease in young children, including the development of human hand, foot, and mouth disease (HFMD). This study aims to further characterize the specific immunological features in EV71–mediated HFMD patients presenting with differing degrees of disease severity.

Methodology

Comprehensive cytokine and chemokine expression were broadly evaluated by cytokine antibody array in EV71–infected patients hospitalized for HFMD compared to Coxsackievirus A16-infected patients and age-matched healthy controls. More detailed analysis using Luminex-based cytokine bead array was performed in EV71–infected patients stratified into diverse clinic outcomes. Additionally, immune cell frequencies in peripheral blood and EV71–specific antibodies in plasma were also examined.

Principal Findings

Expression of several cytokines and chemokines were significantly increased in plasma from EV71–infected patients compared to healthy controls, which further indicated that: (1) GM-CSF, MIP-1β, IL-2, IL-33, and IL-23 secretion was elevated in patients who rapidly developed disease and presented with uncomplicated neurological damage; (2) G-CSF and MCP-1 were distinguishably secreted in EV71 infected very severe patients presenting with acute respiratory failure; (3) IP-10, MCP-1, IL-6, IL-8, and G-CSF levels were much higher in cerebrospinal fluid than in plasma from patients with neurological damage; (4) FACS analysis revealed that the frequency of CD19⁺HLADR⁺ mature B cells dynamically changed over time during the course of hospitalization and was accompanied by dramatically increased EV71–specific antibodies. Our data provide a panoramic view of specific immune mediator and cellular immune responses of HFMD and may provide useful immunological profiles for monitoring the progress of EV71–induced fatal neurological symptoms with acute respiratory failure.

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.

Display of the Viral Epitopes on Lactococcus lactis: A Model for Food Grade Vaccine against EV71

In this study, we have developed a system for display of antigens of Enterovirus type 71 (EV71) on the cell surface of L. lactis. The viral capsid protein (VP1) gene from a local viral isolate was utilized as the candidate vaccine for the development of oral live vaccines against EV71 using L. lactis as a carrier. We expressed fusion proteins in E. coli and purified fusion proteins were incubated with L. lactis. We confirmed that mice orally fed with L. lactis displaying these fusion proteins on its surface were able to mount an immune response against the epitopes of EV71. This is the first example of an EV71 antigen displayed on the surface of a food grade organism and opens a new perspective for alternative vaccine strategies against the EV71. We believe that the method of protein docking utilized in this study will allow for more flexible presentations of short peptides and proteins on the surface of L. lactis to be useful as a delivery vehicle.

Clinical features and phylogenetic analysis of Coxsackievirus A9 in Northern Taiwan in 2011

Background

Coxsackievirus A9 (CA9) was one of the most prevalent serotype of enteroviral infections in Taiwan in 2011. After several patient series were reported in the 1960s and 1970s, few studies have focused on the clinical manifestations of CA9 infections. Our study explores and deepens the current understanding of CA9.

Methods

We analyzed the clinical presentations of 100 culture-proven CA9-infected patients in 2011 by reviewing their medical records and depicted the CA9 phylogenetic tree.

Results

Of the 100 patients with culture-proven CA9 infections, the mean (SD) age was 4.6 (3.4) years and the male to female ratio was 1.9. For clinical manifestations, 96 patients (96%) had fever and the mean (SD) duration of fever was 5.9 (3.4) days. Sixty one patients (61%) developed a skin rash, and the predominant pattern was a generalized non-itchy maculopapular rash without vesicular changes. While most patients showed injected throat, oral ulcers were found in only 19 cases (19%), among whom, 6 were diagnosed as herpangina. Complicated cases included: aseptic meningitis (n=8), bronchopneumonia (n=6), acute cerebellitis (n=1), and polio-like syndrome (n=1). Phylogenetic analysis for current CA9 strains is closest to the CA9 isolate 27-YN-2008 from the border area of mainland China and Myanmar.

Conclusions

The most common feature of CA9 during the 2011 epidemic in Taiwan is generalized febrile exanthema rather than herpangina or hand, foot, and mouth disease. Given that prolonged fever and some complications are possible, caution should be advised in assessing patients as well as in predicting the clinical course.

Excretion of enterovirus 71 in persons infected with hand, foot and mouth disease

BACKGROUND

Hand, foot and mouth disease (HFMD) is a common illness in young children. It also can be seen in adults occasionally. Enterovirus 71 (EV71), a pathogen that causes not only HFMD but also neurological complications and even death, has caused many HFMD outbreaks in China. However, till now the data about the duration of EV71 shedding is very limited.

RESULTS

A total of 136 throat swabs and fecal samples were collected from 27 children and 3 adults, which includs 7 close contacts, 9 mild cases and 14 severe cases,. The participants were divided into three groups namely, severe case group, mild case group and close contact group. All the samples were assayed with real-time polymerase chain reaction (PCR). Kruskal-Wallis Test was employed to compare the difference in duration of viral RNA shedding among three groups. The results showed that significant difference in duration of EV71 shedding was found among three groups (P < 0.01). The longest duration of EV71 shedding in fecal samples is 54 days and 30 days in throat swabs.

CONCLUSIONS

HFMD is characterized by extended excretion of EV71. Our results suggest that the duration of EV71 shedding is correlated with the severity of the disease. EV71 shedding through feces can persist more than 54 days. Prolonged virus shedding is a potential risk factor of proliferating HFMD epidemic.

Enterovirus infection in Korean children and anti-enteroviral potential candidate agents

Although most enterovirus infections are not serious enough to be life threatening, several enteroviruses such as enterovirus 71 are responsible for severe, potentially life-threatening disease. The epidemic patterns of enteroviruses occur regularly during the year, but they may change due to environmental shifts induced by climate change due to global warming. Therefore, enterovirus epidemiological studies should be performed continuously as a basis for anti-viral studies. A great number of synthesized antiviral compounds that work against enteroviruses have been developed but only a few have demonstrated effectiveness in vivo. No proven effective antiviral agents are available for enterovirus disease therapy. The development of a new antiviral drug is a difficult task due to poor selective toxicity and cost. To overcome these limitations, one approach is to accelerate the availability of other existing antiviral drugs approved for antiviral effect against enteroviruses, and the other way is to screen traditional medicinal plants.

Enteroviruses isolated from herpangina and hand-foot-and-mouth disease in Korean children

Hand-foot-and-mouth disease (HFMD) and herpangina are commonly prevalent illness in young children. They are similarly characterized by lesions on the skin and oral mucosa. Both diseases are associated with various enterovirus serotypes. In this study, enteroviruses from patients with these diseases in Korea in 2009 were isolated and analyzed. Demographic data for patients with HFMD and herpangina were compared and all enterovirus isolates were amplified in the VP1 region by reverse transcription-polymerase chain reaction and sequenced. Among the enterovirus isolates, prevalent agents were coxsackievirus A16 in HFMD and coxsackievirus A5 in herpangina. More prevalent months for HFMD were June (69.2%) and May (11.5%), and June (40.0%) and July (24.0%) for herpangina. Age prevalence of HFMD patients with enterovirus infection was 1 year (23.1%), 4 years (19.2%), and over 5 years (19.2%). However, the dominant age group of herpangina patients with enterovirus infection was 1 year (48.0%) followed by 2 years (28.0%). Comparison of pairwise VP1 nucleotide sequence alignment of all isolates within the same serotypes revealed high intra-type variation of CVA2 isolates (84.6–99.3% nucleotide identity). HFMD and herpangina showed differences in demographic data and serotypes of isolated enteroviruses, but there was no notable difference in amino acid sequences by clinical syndromes in multiple comparison of the partial VP1 gene sequence.

A case-control study of risk factors for severe hand-foot-mouth disease among children in Ningbo, China, 2010-2011

BACKGROUND

A small fraction of hand-foot-mouth disease (HFMD) progression from the onset of severity to fatality may be remarkably rapid. Early recognition of children at risk of severity is critical to increase treatment effectiveness and reduce acute mortality.

METHODS

A frequency-matched case-control study was conducted between January 2010 and June 2011 in Ningbo to identify risk factors associated with the occurrence of severity in children with HFMD. Data including demographic characteristics, clinical features, and laboratory test results were collected by trained interviewers through retrospective medical record review and/or face-to-face interviews with children's parents using a standardized questionnaire.

RESULTS

Eighty-nine cases with severe HFMD and 267 controls with mild HFMD were recruited in this study. Palm rashes (OR = 0.004, 95%CI = 0.000-0.039, p < 0.001), oral ulcers or herpes (OR = 0.001, 95%CI = 0.000-0.009, p < 0.001) were significantly associated with protection against severity, and an increased risk of severity was significantly associated with the presence of, e.g., a high fever of over 39°C for more than 3 days (OR = 2.217, 95%CI = 1.082-4.541, p = 0.030), leg trembling (OR = 29.008, 95%CI = 1.535-548.178, p = 0.025), papule rash (OR = 4.622, 95%CI = 1.110-19.252, p = 0.035), a raised WBC count > 10.8 × 10(9)/L (OR = 4.495, 95%CI = 1.311-15.415, p = 0.017), and human enterovirus 71 infection (OR = 39.172, 95%CI = 9.803-156.522, p < 0.001).

CONCLUSION

Clinicians should pay increased attention to children diagnosed as HFMD with the independent risk factors above.

Antiviral Ability of Kalanchoe gracilis Leaf Extract against Enterovirus 71 and Coxsackievirus A16

Pandemic infection or reemergence of Enterovirus 71 (EV71) and coxsackievirus A16 (CVA16) occurs in tropical and subtropical regions, being associated with hand-foot-and-mouth disease, herpangina, aseptic meningitis, brain stem encephalitis, pulmonary edema, and paralysis. However, effective therapeutic drugs against EV71 and CVA16 are rare. Kalanchoe gracilis (L.) DC is used for the treatment of injuries, pain, and inflammation. This study investigated antiviral effects of K. gracilis leaf extract on EV71 and CVA16 replications. HPLC analysis with a C-18 reverse phase column showed fingerprint profiles of K. gracilis leaf extract had 15 chromatographic peaks. UV/vis absorption spectra revealed peaks 5, 12, and 15 as ferulic acid, quercetin, and kaempferol, respectively. K. gracilis leaf extract showed little cytotoxicity, but exhibited concentration-dependent antiviral activities including cytopathic effect, plaque, and virus yield reductions. K. gracilis leaf extract was shown to be more potent in antiviral activity than ferulic acid, quercetin, and kaempferol, significantly inhibiting in vitro replication of EV71 (IC(50) = 35.88 μg/mL) and CVA16 (IC(50) = 42.91 μg/mL). Moreover, K. gracilis leaf extract is a safe antienteroviral agent with the inactivation of viral 2A protease and reduction of IL-6 and RANTES expressions.

Human SCARB2-mediated entry and endocytosis of EV71

Enterovirus (EV) 71 infection is known to cause hand-foot-and-mouth disease (HFMD) and in severe cases, induces neurological disorders culminating in fatality. An outbreak of EV71 in South East Asia in 1997 affected over 120,000 people and caused neurological disorders in a few individuals. The control of EV71 infection through public health interventions remains minimal and treatments are only symptomatic. Recently, human scavenger receptor class B, member 2 (SCARB2) has been reported to be a cellular receptor of EV71. We expressed human SCARB2 gene in NIH3T3 cells (3T3-SCARB2) to study the mechanisms of EV71 entry and infection. We demonstrated that human SCARB2 serves as a cellular receptor for EV71 entry. Disruption of expression of SCARB2 using siRNAs can interfere EV71 infection and subsequent inhibit the expression of viral capsid proteins in RD and 3T3-SCARB2 but not Vero cells. SiRNAs specific to clathrin or dynamin or chemical inhibitor of clathrin-mediated endocytosis were all capable of interfering with the entry of EV71 into 3T3-SCARB2 cells. On the other hand, caveolin specific siRNA or inhibitors of caveolae-mediated endocytosis had no effect, confirming that only clathrin-mediated pathway was involved in EV71 infection. Endocytosis of EV71 was also found to be pH-dependent requiring endosomal acidification and also required intact membrane cholesterol. In summary, the mechanism of EV71 entry through SCARB2 as the receptor for attachment, and its cellular entry is through a clathrin-mediated and pH-dependent endocytic pathway. This study on the receptor and endocytic mechanisms of EV71 infection is useful for the development of effective medications and prophylactic treatment against the enterovirus.

Detection of human enterovirus 71 and coxsackievirus A16 in children with hand, foot and mouth disease in China

The aims of the present study were to investigate the genetic characteristics of enterovirus 71 (EV71) and coxsackievirus A16 (CVA16) strains in China and to evaluate the relationship between the genotypes of CVA16 and EV71 and their geographical distribution. A total of 399 stool specimens were collected from children with symptoms of hand, foot and mouth disease (HFMD) in Zhejiang Province. The presence of enteroviruses was determined using reverse transcription-semi-nested PCR targeted to the VP1 gene of all human enteroviruses and DNA sequencing. EV71 and CVA16, the major etiological agents of HFMD, were detected in 38.4% (38/99) and 35.4% (35/99) of HEV-A species-positive cases, respectively. Based on the phylogenetic analysis of the VP1 gene, EV71 strains identified in this study belong to subgenotype C4, and CVA16 strains herein were classified into clusters B2a and B2b within the genotype B2. Taking into consideration other published data, we conclude that the genetic characteristics of enteroviruses in China reflect the pattern of the endemic circulation of the subgenotype C4 to EV71 and clusters B2a and B2b within genotype B2 to CVA16, which have been continuously circulating in China since 1997. This observation indicates that the genetic characteristics of enteroviruses in China seem to depend on their special geographical and climatical features allowing them to be sustained with little external effect.

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.

Molecular analysis of virulent determinants of enterovirus 71

Enterovirus 71 (EV71) is the most important causative agent of hand, foot and mouth disease (HFMD) in children. In most cases, it is a self-limiting illness. However some EV71 infectious cases can develop severe clinical outcomes, such as encephalitis, meningitis, poliomyelitis like paralysis, and even death. To identify the determinants of virulence, the deduced amino acid sequence of polyprotein and nucleotide sequence of 5′-NTR and 3′-NTR in 25 SC-EV71 strains (strains from severe cases) and 31 MC-EV71 strains (strains from mild cases) were analyzed. Results showed four amino acids on two positions (Gly^P710/Gln^P710/Arg^P710 and Glu^P729) on the DE and EF loop of VP1, one (Lys^P930) on the surface of protease 2A and four nucleotides on three positions (G^P272, U^P488 and A^P700/U^P700) in the 5'-NTR region are associated with EV71 virulent phenotype. Predicted secondary structure of RNA using the consensus sequence of 5'-NTR by RNAStructure showed the mutation of nucleotide at position 488 in strain BJ08-Z004-3 (position 491 in prototype strain BrCr) can result in the discrepancy of an additional pair of nucleotides and thus change the stability of the second structure of IRES. Fragment base content analysis showed that in the region 696 to 714 bp at the 5'-NTR, where the A^P700/U^P700 was located, the nucleotide constitution ratios differed significantly between SC-EV71 and MC-EV71 strains. In conclusion, comparative genomic analysis showed that virulence of EV71 strains are mainly determined by the amino acids on two positions of VP1, one position of protease 2A and the nucleotides on three positions in 5'-NTR.

The changing seroepidemiology of enterovirus 71 infection among children and adolescents in Singapore

BACKGROUND

Enterovirus 71 (EV71) has caused recurrent epidemics of hand, foot and mouth disease among children in Singapore. Between August 2008 and July 2010, we conducted a survey to estimate the seroprevalence of EV71 infection among children and adolescents aged 1-17 years. We compared our EV71 seroepidemiologic findings with a previous study conducted in 1996-1997.

METHODS

The survey involved the prospective collection of 1,200 residual sera from Singapore residents aged 1-17 years in two hospitals. Neutralizing antibodies to EV71 were detected by the microneutralization test. The geometric mean titer (GMT) of EV71 antibodies and 95% confidence intervals (CI) were calculated and compared by age groups. Statistical significance was taken as P < 0.05.

RESULTS

The overall EV71 antibody prevalence was 26.9% (95% CI: 24.5-29.5%). It increased significantly from 14.3% in children aged 1-6 years to 27.8% in those aged 7-12 years, and reached 38.8% in adolescents aged 13-17 years. The seroconversion rate differed by about 12% between the consecutive age groups. The GMT of EV71 antibodies was higher among primary school children aged 7-12 years in our study than that among the 6-12 year age group in the 1996-1997 study.

CONCLUSIONS

Higher antibody titers were observed in children aged 1-6 years than those in the other two age groups, indicating that most of the infections had been acquired during early childhood. EV71 infection is common among children and adolescents in Singapore, with 39% infected by the time they are in secondary school (13-17 years of age).

Annexin II binds to capsid protein VP1 of enterovirus 71 and enhances viral infectivity

Enterovirus type 71 (EV71) causes hand, foot, and mouth disease (HFMD), which is mostly self-limited but may be complicated with a severe to fatal neurological syndrome in some children. Understanding the molecular basis of virus-host interactions might help clarify the largely unknown neuropathogenic mechanisms of EV71. In this study, we showed that human annexin II (Anx2) protein could bind to the EV71 virion via the capsid protein VP1. Either pretreatment of EV71 with soluble recombinant Anx2 or pretreatment of host cells with an anti-Anx2 antibody could result in reduced viral attachment to the cell surface and a reduction of the subsequent virus yield in vitro. HepG2 cells, which do not express Anx2, remained permissive to EV71 infection, though the virus yield was lower than that for a cognate lineage expressing Anx2. Stable transfection of plasmids expressing Anx2 protein into HepG2 cells (HepG2-Anx2 cells) could enhance EV71 infectivity, with an increased virus yield, especially at a low infective dose, and the enhanced infectivity could be reversed by pretreating HepG2-Anx2 cells with an anti-Anx2 antibody. The Anx2-interacting domain was mapped by yeast two-hybrid analysis to VP1 amino acids 40 to 100, a region different from the known receptor binding domain on the surface of the picornavirus virion. Our data suggest that binding of EV71 to Anx2 on the cell surface can enhance viral entry and infectivity, especially at a low infective dose.

Hand foot and mouth disease due to enterovirus 71 in Malaysia

Hand foot and mouth disease is a febrile sickness complex characterized by cutaneous eruption (exanthem) on the palms and soles with simultaneous occurrence of muco-cutanous vesiculo-ulcerative lesions (enanthem) affecting the mouth. The illness is caused by a number of enteroviruses with coxsackievirus A16 and enterovirus 71 as the main causative agents. Human enterovirus 71 (EV71) belongs to the species Human enterovirus A under the genus Enterovirus within the family Picornaviridae. EV71 has been associated with an array of clinical diseases including hand foot and mouth disease (HFMD), aseptic meningitis, encephalitis and poliomyelitis-like acute flaccid paralysis. A large outbreak of HFMD due to highly neurovirulent EV71 emerged in Malaysia in 1997, and caused 41 deaths amongst young children. In late 2000, a recurrence of an outbreak of HFMD occurred in Malaysia with 8 fatalities in peninsular Malaysia. Outbreak of HFMD due to EV71 recurred in 2003 with an unknown number of cases and mortalities. A similar outbreak of HFMD with 2 recorded deaths in young children occurred in peninsular Malaysia in late 2005 and this was followed by a larger outbreak in Sarawak (Malaysian Borneo) with 6 reported fatalities in the early part of 2006. The current on-going outbreak of HFMD started in peninsular Malaysia in epidemiological week 12 of 2010. As with other HFMD outbreaks in Malaysia, both EV71 and CA16 were the main aetiological viruses isolated. In similarity with the HFMD outbreak in 2005, the isolation of CA16 preceded the appearance of EV71. Based on the VP1 gene nucleotide sequences, 4 sub-genogroups of EV71 (C1, C2, B3 and B4) co-circulated and caused the outbreak of hand, foot and mouth disease in peninsular Malaysia in 1997. Two sub-genogroups (C1 and B4) were noted to cause the outbreak in 2000 in both peninsular Malaysia and Sarawak. EV71 of sub-genogroup B5 with smaller contribution from sub-genogroup C1 caused the outbreak in 2003. In the 2005 outbreak, besides the EV71 strains of sub-genogroup C1, EV71 strains belonging to sub-genogroup B5 were isolated but formed a cluster which was distinct from the EV71 strains from the sub-genogroup B5 isolated in 2003. The four EV71 strains isolated from clinical specimens of patients with hand, foot and mouth disease in the Sarawak outbreak in early 2006 also belonged to sub-genogroup B5. Phylogenetic analysis of the VP1 gene suggests that the EV71 strains causing the outbreak in Sarawak could have originated from peninsular Malaysia. Epidemiological and molecular data since 1997 show the recurrence of HFMD due to EV71 in Malaysia every 2 to 4 years. In each of the past outbreaks, more than one sub-genogroup of the virus co-circulate.

Sustained high levels of interleukin-6 contribute to the pathogenesis of enterovirus 71 in a neonate mouse model

Enterovirus 71 (EV71) is the major causative agent of hand, foot, and mouth disease (HFMD) in young children and has been consistently associated with the most severe complications of the disease, including central nervous system inflammation and pulmonary edema. Increasing frequency and amplitude of EV71 outbreaks have raised awareness and concerns worldwide. Previous reports proposed that overwhelming virus replication combined with the induction of massive proinflammatory cytokines is responsible for the pathogenicity of EV71. Specifically, elevated interleukin-6 (IL-6) levels were observed consistently in patients and strongly correlated with disease severity. In this study, we show in the neonate mouse model that sustained high levels of IL-6 produced upon EV71 infection lead to severe tissue damage and eventually death of the animals. Administration of anti-IL-6 neutralizing antibodies after the onset of the clinical symptoms successfully improved the survival rates and clinical scores of the infected hosts. Compared to untreated infected controls, anti-IL-6-treated mice displayed reduced tissue damage, absence of splenic atrophy, and increased immune cell activation. In addition, markedly elevated systemic levels of IL-10 were measured in the protected animals. Furthermore, there was no significant difference in virus titers between anti-IL-6-treated mice and untreated mice, indicating that the anti-IL-6 antibody-mediated protection is independent of the virus load. Our findings thus demonstrate that IL-6 plays a major role in EV71-induced immunopathogenesis. As there is still neither vaccine nor treatment available against EV71, anti-IL-6 antibody treatment represents a potential therapeutic approach to providing protection from the most severe complications of the disease.

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.

Comparison of clinical features between coxsackievirus A2 and enterovirus 71 during the enterovirus outbreak in Taiwan, 2008: a children's hospital experience

BACKGROUND/PURPOSE

Coxsackievirus A2 (Cox A2) was the predominant serotype in the enterovirus outbreak in Taiwan, 2008. However, detailed clinical features of Cox A2 infection have not been reported. In this study, we compared Cox A2 with enterovirus 71 (EV71) in terms of clinical manifestation and epidemiology during the 2008 enterovirus outbreak in Taiwan.

METHODS

A total of 280 hospitalized patients (97 with culture-proven EV71 infection and 183 with culture-proven Cox A2 infection) in 2008 at the Chang Gung Children's Medical Center were enrolled in this study. Epidemiologic data, clinical manifestations, and outcomes for these patients were collected and compared.

RESULTS

Both Cox A2 and EV71 serotypes peaked in June and declined soon afterwards. Seventy-one percent of the patients were younger than 3 years of age. Both groups had the same male-to-female ratio of 1.6:1. Patients with EV71 infection had a significantly longer hospitalization period (4.1 vs. 3.0 days, p< 0.001). Fever, fever for more than 3 days with a temperature above 39 degrees C, lethargy, poor activity, poor appetite and a myoclonic jerk were significantly associated with EV71 infection. Fever, or fever with a temperature above 39 degrees C, febrile seizure, elevated white cell counts, and elevated serum C-reactive protein concentrations were significantly associated with Cox A2 infection. Most patients with EV71 infection presented with hand-foot-mouth disease (78.3%), while most Cox A2-infected patients presented with herpangina (83.6%). Central nervous system complications were found in 18.6% of EV71-infected children, but only in 1.1% of Cox A2-infected children. All the patients with Cox A2 infection showed total recovery. One patient with EV71 infection died from encephalitis with cardiopulmonary failure, and 6.2% of EV71-infected children had neurologic sequelae.

CONCLUSION

Both Cox A2 and EV71 serotypes accounted for the enterovirus outbreak in Taiwanese children in 2008. Compared with those infected by EV71, the children with Cox A2 infection mostly presented with herpangina, had fewer central nervous system complications, and had better overall outcome.

Risk factors for severe hand foot and mouth disease

BACKGROUND

Hand foot and mouth disease (HFMD) and herpangina are enteroviral infectious diseases caused mainly by Coxsackie virus A (CA) or enterovirus 71 (EV71). From 2000 to 2002, many complicated cases were reported in Japan, therefore a nationwide questionnaire survey was carried out to assess the situation. The subjects were patients with HFMD or herpangina, or other enterovirus infection from 2000 to 2002, who were either hospitalized over 24 h or who died. The response rates were 41.3% in 2000 and 2001 and 31.6% in 2002. The survey period included the year 2000, when HFMD epidemics due to EV71 occurred. To examine risk factors causing complications of enterovirus infection, severe cases of HFMD were focused on.

METHODS

HFMD cases in 2000 were divided into two groups according to severity: 'more severe' and 'less severe'. 'More severe' was defined as 'fatal, involving sequelae, or involving hospitalization for 7 days or longer'. Statistical analyses were conducted with Epi info version 3.3 and the association between risk factors and severity was estimated.

RESULTS

The number of patients with more severe and less severe cases was 96 and 103, respectively. There was no difference in sex, age, having siblings and family history between the two groups. There was a significant association between attending child care center and severe HFMD.

CONCLUSIONS

It is not clear why attending child care centers was associated with HFMD severity. Further study is needed.

Etiology and clinico-epidemiological profile of acute viral encephalitis in children of western Uttar Pradesh, India

OBJECTIVES

To study the etiology of viral encephalitis (VE) in the children of western Uttar Pradesh, India and to assess the clinico-epidemiological profile of these children in relation to VE.

METHODS

Both cerebrospinal fluid and serum samples were collected from pediatric patients suffering from encephalitis hospitalized at Jawaharlal Nehru Medical College, Aligarh from July 2004 to November 2006. Viral isolation was done on RD cells, HEp-2 cells, and Vero cells from the cerebrospinal fluid samples of children with suspected VE. A microneutralization test was performed for enterovirus 71. An enzyme immunoassay for IgM antibodies was performed for measles virus, mumps virus, varicella zoster virus, herpes simplex virus 1, and Japanese encephalitis virus.

RESULTS

Eighty-seven patients were enrolled in the study. The most common etiology of VE was enterovirus 71 (42.1%), followed by measles (21.1%), varicella zoster virus (15.8%), herpes simplex virus (10.5%), and mumps (10.5%). Japanese encephalitis virus was not found in any case. Enterovirus 71 infection caused significant morbidity in children; mortality occurred in 50%. A preponderance of cases occurred in December. In our study generalized convulsions along with altered sensorium were the significant findings in patients with VE.

CONCLUSIONS

Enterovirus 71, the major etiology of VE in our study, was associated with significant mortality and morbidity. Such studies should be conducted frequently to assess the role of emerging VE in different regions.

HLA-A33 is associated with susceptibility to enterovirus 71 infection

OBJECTIVE

Enterovirus 71 has caused large epidemics of disease, resulting in many fatalities and severe sequelae, in Taiwan and some other countries. In this study, host genetic factors were investigated to link susceptibility to and clinical severity of enterovirus 71 infections.

METHODS

We enrolled 219 enterovirus 71 case subjects and 97 control children. HLA typing was performed with sequence-specific primers, and polymorphisms of immune-related candidate genes were detected with polymerase chain reaction, followed by automated gene sequencing.

RESULTS

Of the 219 enterovirus 71 cases, 26% (56 of 219 cases) were uncomplicated cases, 74% (163 of 219 cases) were complicated cases, 57% (125 of 219 cases) were complicated cases with central nervous system involvement, and 17% (38 of 219 cases) involved cardiopulmonary failure after central nervous system involvement. Univariate analyses showed that tumor necrosis factor alpha promoter type II (-308 A allele), HLA-A33, and HLA-DR17 were significantly associated with enterovirus 71 susceptibility. Multivariate analysis demonstrated that HLA-A33 was the gene most significantly susceptible to enterovirus 71. HLA-A2 was associated with the development of cardiopulmonary failure.

CONCLUSIONS

HLA-A33, which is a common phenotype in Asian populations but is rare in white populations, was most significantly associated with enterovirus 71 infection, compared with the other candidate genes we studied, whereas HLA-A2 was significantly related to cardiopulmonary failure.

Antiviral activity of pyridyl imidazolidinones against enterovirus 71 variants

Pyridyl imidazolidinone is a novel class of capsid binder which can inhibit enterovirus 71 (EV71). In this study, we tested the susceptibility of six recombinant viruses with different single-site mutations in VP1. Eleven modified pyridyl imidazolidinones were synthesized and used to probe the interaction between these compounds and the EV71 VP1 protein. We found that the D31N or E98K mutant viruses were susceptible to bulkier compounds, which suggested that mutations at these two sites in VP1 may widen the hydrophobic pocket of VP1, allowing bulkier compounds to enter and interfere VP1-receptor binding. Additionally, the Y116H mutant was more resistant to pyridyl imidazolidinone compounds containing a methyl group in the central position of the hydrophobic linker. When a trifluoromethyl group was substituted for the methyl group in the middle of the linker chain, the inhibitory effect was totally abolished in the Y116H mutant, suggesting that the interaction between Tyr (Y) 116 of VP1 and the central position of the linker chain of pyridyl imidazolodinone is very important for drug efficacy. A V192M mutant was resistant to most of the derivatives, indicating that residue 192 is a key mutation for resistance to pyridyl imidazolidinone.

Outbreak of Neurologic Enterovirus Type 71 Disease: A Diagnostic Challenge

BACKGROUND

Similar to poliovirus, enterovirus type 71 (EV71) causes severe disease, including aseptic meningitis, encephalitis, acute flaccid paralysis, and acute cardiopulmonary dysfunction. Large epidemics of EV71 infection have been reported worldwide.

METHODS

After recognition of a cluster of cases of EV71 disease, we reviewed records of patients with EV71 disease who required hospitalization at The Children's Hospital in Denver, Colorado, from 2003 through 2005. The presence of enterovirus was detected by reverse-transcriptase polymerase chain reaction (PCR) and/or viral culture of specimens from multiple sources, and the virus was typed as EV71 using genetic sequencing.

RESULTS

Eight cases of EV71 disease were identified in both 2003 and 2005. Fifty-six percent of patients with EV71 disease were < or = 6 months of age (range, 4 weeks to 9 years). All 16 patients had EV71 central nervous system infection. Enterovirus PCR (EV-PCR) of cerebrospinal fluid specimens yielded positive results for only 5 (31.2%) of the 16 patients; all of these patients were < 4 months of age and had less severe disease. However, EV-PCR of upper respiratory tract specimens yielded positive results for 8 (100%) of 8 patients, and EV-PCR of lower gastrointestinal tract specimens yielded positive results for 7 (87.5%) of 8 patients.

CONCLUSIONS

An outbreak of neurologic EV71 disease occurred in Denver, Colorado, during 2003 and 2005. Likely, EV71 disease remains unrecognized in other parts of the United States, because EV-PCR of cerebrospinal fluid frequently yields negative results. EV-PCR of specimens from the respiratory and gastrointestinal tracts had higher diagnostic yields than did EV-PCR of cerebrospinal fluid. EV71 infection should be considered in young children presenting with aseptic meningitis, encephalitis, acute flaccid paralysis, or acute cardiopulmonary collapse. EV71 infection may be an underrecognized emerging disease in the United States.

Pathophysiological mechanism of lung injury in patients with leptospirosis

AIMS

Acute lung injury (ALI) is a serious clinical problem. We investigated the pathogenetic mechanisms of ALI caused by leptospirosis.

METHODS

The study included five cases of leptospirosis. We monitored the arterial pressure (AP) and heart rate (HR) and analysed the AP and HR variabilities for assessment of autonomic functions. Histopathological changes in the lung, brain, kidney, and liver were examined. In addition, we identified the expression of inducible nitric oxide synthase (iNOS) using immunohistochemical stain.

RESULTS

Five patients associated with leptospirosis died of ALI. Before death, severe hypotension and bradycardia occurred. Spectral analysis of AP and HR variabilities indicated decreased sympathetic drive with increased parasympathetic activity. Pathological examinations revealed alveolar haemorrhage and necrotic lesions in various organs. Immunohistochemical stain disclosed iNOS activity in multiple organs. Biochemical determinations indicated hypoxia, hyperglycaemia, increased nitrite/nitrate, methyl guanidine and other factors.

CONCLUSIONS

These changes suggest that leptospirosis causes severe hypotension and bradycardia accompanied by autonomic dysfunction. Finally, multiple organ failure and damage ensued. The pathogenesis of lung and organ injury may involve iNOS and NO production.

Passive protection against lethal enterovirus 71 infection in newborn mice by neutralizing antibodies elicited by a synthetic peptide

Enterovirus 71 (EV71) infections could lead to high mortalities and neither vaccine nor therapeutic treatment is available. We investigated vaccination with a synthetic peptide SP70 representing a neutralizing linear VP1 epitope of EV71 strain 41 (subgenogroup B4) and passive transfer of anti-SP70 antibodies to protect suckling Balb/c mice against EV71 infectivity. When the mouse anti-SP70 antisera with a neutralizing antibody titer of 1:32 were passively administered to one-day-old suckling mice which had been challenged with a lethal dose of 1000 TCID(50) per mouse, the neutralizing anti-SP70 antibodies were able to confer 80% in vivo protection. In contrast, suckling mice which did not receive any anti-SP70 antisera did not survive the viral challenge at day 21 postinfection. Histological examination and real-time RT-PCR assays revealed viral infiltration in small intestines of EV71-infected mice. Interestingly, anti-SP70 antibodies play a major role in the inhibition of EV71 replication in vivo and significantly reduced the viral titer. In conclusion, EV71-neutralizing antibodies elicited by the synthetic peptide SP70 were able to confer good in vivo passive protection against homologous and heterologous EV71 strains in suckling Balb/c mice.

DNA vaccine constructs against enterovirus 71 elicit immune response in mice

Background

Enterovirus 71 (EV71) is a major causative viral agent responsible for large outbreaks of hand, foot and mouth disease (HFMD), a common rash illness in children and infants. There is no effective antiviral treatment for severe EV71 infections and no vaccine is available. The objectives of this study were to design and construct a DNA vaccine against Enterovirus 71 using the viral capsid protein (VP1) gene of EV71 and to verify the functionality of the DNA vaccine in vitro and in vivo.

Methods

The VP1 gene of EV71 from two local outbreak isolates were amplified using PCR and then inserted into a eukaryotic expression vector, pVAX1. The 3.9 kb recombinant constructs were transformed into competent E. coli cells and the positive clones were screened and selected using PCR analysis, restriction digestion analysis and DNA sequencing. The constructs were then tested for protein expression in Vero cells. Subsequently, in the in vivo studies, female Balb/c mice were immunized with the DNA vaccine constructs. Enzyme Linked Immunosorbent Assay (ELISA) and virus neutralizing assay were performed to detect the presence of anti-VP1 IgG in mice and its neutralizing effect against the EV71.

Results

The pVAX1 vector was successfully cloned with the VP1 gene from each of the isolate (S2/86/1 and 410/4) in the correct orientation and in-frame. The DNA vaccine constructs with the VP1 gene were shown to be expressed in a cell-free in vitro expression system. The VP1 protein was successfully expressed in the mammalian cell line and was detected using RT-PCR, Indirect Immunofluorescence Assay (IFA) and western blotting. The anti-VP1 IgG levels in mice immunized with the DNA vaccine constructs increased after the first booster but declined following the second booster. The anti-VP1 IgG in the mice immunized with the DNA vaccine constructs exhibited neutralising activity against EV71.

Conclusion

The promising results obtained in the present study have prompted further testing to improve the expression and immunogenicity of this potential EV71 DNA vaccine.

Cerebrospinal fluid cytokines in enterovirus 71 brain stem encephalitis and echovirus meningitis infections of varying severity

Taiwan has experienced several outbreaks of enterovirus 71 (EV71) infections since 1998. This study examined the quantitative relationship between specific cytokines in the cerebrospinal fluid (CSF) and the severity of EV71 brain stem encephalitis (BE), and investigated whether the CSF cytokine response differed from that to uncomplicated echovirus meningitis (EM). The study included 57 children with EV71 BE, of whom 24 had isolated BE, 24 had autonomic nervous system (ANS) dysregulation, and nine had pulmonary oedema (PE), and 15 children with EM. All were confirmed by virus culture. Mean CSF glucose, total protein and lactate levels were increased significantly in association with the severity of EV71 BE. The mean CSF concentration of interleukin (IL)-1beta in children with EV71 PE was significantly higher than in those with isolated BE. IL-6 and interferon (IFN)-gamma levels were significantly higher for EV71 PE and ANS dysregulation than for isolated BE. In contrast, EM was associated with high levels of IL-1beta and low levels of IFN-gamma. Cytokines in the central nervous system, as well as in blood, appear to be involved in the pathogenesis of EV71 BE.

Heart rate variability monitoring in the detection of central nervous system complications in children with enterovirus infection

PURPOSE

Previous studies suggest the possibility of autonomic dysfunction in patients with complicated hand, foot, and mouth disease (HFMD) and herpangina. Heart rate variability (HRV), an index for autonomic nervous system, may be useful to detect disease progression.

MATERIALS AND METHODS

From 2001 to 2002, 66 patients (1-9 years old) were enrolled prospectively in either a control (20 patients) or disease (46 patients with HFMD or herpangina) group. The disease group was subdivided into stage I (fever only), stage II (with complications of encephalomyelitis), and stage III (with complications of encephalomyelitis as well as tachycardia, hyperglycemia, tachypnea, and hypertension or hypotension) groups. Data from electrocardiograms were transformed for HRV.

RESULTS

The HRV parameters generally decreased and the low frequency (LF)/high frequency ratio (HF) increased in the disease groups. Patients in disease group stage II had significantly lower parameters of HRV (triangular index, total power, LF power, and HF power) and higher LF/HF ratio than those in disease group stage I. With this trend, patients with stage III disease had extremely low HRV parameters. The inferred criteria of HRV (standard deviation of normal-to-normal interval <17 milliseconds and HF power <24 milliseconds(2)) to define stage III patients (sensitivity, 100%; specificity, 71.4%) were also useful to predict disease progression.

CONCLUSIONS

The HRV markedly decreased, most likely because of autonomic dysfunction, in patients with HFMD and herpangina when complicated with central nervous system involvement and cardiopulmonary failure and may be useful parameters to monitor disease progression.

Genetic diversity of enterovirus 71 associated with hand, foot and mouth disease epidemics in Japan from 1983 to 2003

BACKGROUND

Enterovirus 71 (EV71) is one of the major etiologic agents of hand, foot and mouth disease (HFMD). The surveillance data indicate that EV71 infection follows an epidemic mode of transmission, causing large outbreaks and then becoming quiescent for a few years.

METHODS

We investigated the genetic diversity of a total of 121 EV71 strains isolated from patients with HFMD in Fukushima, Japan, from 1983 to 2003 and compared their genetic relation with the 164 EV71 strains isolated in the world using phylogenetic analysis based on the VP4 sequence.

RESULTS

We observed EV71-related HFMD outbreaks in Fukushima in 1984, 1987, 1990, 1993, 1997, 2000 and 2003. Phylogenetic reconstruction of EV71 strains isolated in Fukushima demonstrated 8 genetically distinct clusters, including 6 subgroups previously designated as B-1, B-2 and 3, B-4, C-1, C-2, and C-3 and 2 subgroups newly designated as B-5 and C-4. Additional 2 indistinct clusters belonged to genogroup C and were named C-U1 and C-U2. Of those subgroups, B-1, C-U1, C-U2, C-2, B4, and C-4 and B-5 dominantly related to epidemics that occurred in the years 1984, 1987 and 1990, 1993, 1997, 2000 and 2003, respectively. EV71 strains derived from each outbreak in Fukushima formed a single cluster with those isolated during almost the same time period in other area of Japan and in other countries.

CONCLUSIONS

Our results suggested that the repeated EV71 outbreaks might be the result of the worldwide transmission of the newly introduced genetically divergent EV71 strains.

N-acetylcysteine abrogates acute lung injury induced by endotoxin

1. Acute lung injury (ALI) or acute respiratory distress syndrome is a serious clinical problem with high mortality. N-Acetylcysteine (NAC) is an anti-oxidant and a free radical scavenger. It has been reported recently that NAC ameliorates organ damage induced by endotoxin (lipopolysaccharide; LPS) in conscious rats. The present study was designed to evaluate the effects of NAC on LPS-induced ALI and other changes in anaesthetized rats. 2. Sprague-Dawley rats were anaesthetized with pentobarbital (40 mg/kg, i.p.). Endotracheal intubation was performed to provide artificial ventilation. Arterial pressure and heart rate were monitored. The extent of ALI was evaluated with the lung weight (LW)/bodyweight ratio, LW gain, exhaled nitric oxide (NO) and protein concentration in bronchoalveolar lavage (PCBAL). Haematocrit, white blood cells, plasma nitrate/nitrite, methyl guanidine (MG), tumour necrosis factor (TNF)-alpha and interleukin (IL)-1b were measured. Pathological changes in the lung were examined and evaluated. 3. Endotoxaemia was produced by injection of 10 mg/kg, i.v., LPS (Escherichia coli). Animals were randomly divided into three groups. In the vehicle group, rats received an i.v. drip of physiological saline solution (PSS) at a rate of 0.3 mL/h. The LPS group received an i.v. drip of PSS for 1 h, followed by LPS (10 mg/kg by slow blous injection, i.v., over 1-2 min). Rats in the LPS + NAC group received NAC by i.v. drip at a rate of 150 mg/kg per h (0.3 mL/h) for 60 min starting 10 min before LPS administration (10 mg/kg by slow blous injection, i.v., over 1-2 min). Each group was observed for a period of 6 h. 4. N-Acetylcysteine treatment improved the LPS-induced hypotension and leukocytopenia. It also reduced the extent of ALI, as evidenced by reductions in LW changes, exhaled NO, PCBAL and lung pathology. In addition, NAC diminished the LPS-induced increases in nitrate/nitrite, MG, TNF-a and IL-1b. 5. In another series of experiments, LPS increased the mortality rate compared with the vehicle group (i.v. drip of PSS at a rate of 0.3 mL/h) during a 6 h observation period. N-Acetylcysteine, given 10 min prior to LPS, significantly increased the survival rate. 6. The results of the present study suggest that NAC exerts a protective effect on the LPS-induced ALI. The mechanisms of action may be mediated through the reduction of the production of NO, free radicals and pro-inflammatory cytokines.

Status of cellular rather than humoral immunity is correlated with clinical outcome of enterovirus 71

We valuated specific cellular and humoral immune response of cases of enterovirus 71 (EV71) infection and correlated immune response with clinical outcome. After obtaining informed consent, we enrolled 30 EV71 cases including 7 cases with brainstem encephalitis plus pulmonary edema, 12 cases of CNS (CNS) involvement and 11 uncomplicated cases. We measured antibodies specific to EV71, lymphocyte proliferation response and EV71-stimulated cellular response of Th1/Th2 cytokines and chemokines. The 7 EV71 cases involving brainstem encephalitis plus pulmonary edema had a significantly lower phytohemagglutinin stimulation index than other cases (p = 0.04). After EV71 stimulation of peripheral mononuclear cells, there was a significant increase in cellular Th1 cytokine (gamma-interferon) and proinflammatroy cytokines. However, cases with pulmonary edema had significantly lower cellular gamma-interferon (p = 0.04), lower cellular IL-1beta (p = 0.04), lower cellular IL-6 (p = 0.04), lower cellular tumor necrosis factor-alpha response (p = 0.04), and lower cellular macrophage inflammatory protein-1alpha (p = 0.04) response compared with other cases. Their titers of EV71 neutralizing antibodies demonstrated no difference among cases. These results suggest lower EV71-specific cellular response may be associated with immunopathogenesis of EV71-related pulmonary edema.