Enterovirus 71 infection: An experience in Korea, 2009

Prospective, Cross-Sectional Study Finds No Common Viruses in Cerebrospinal Fluid of Children with Pseudotumor Cerebri

Pseudotumor cerebri (PTC) in children is a rare condition whose underlying cause remains largely unknown. No study has yet systematically examined viral infection as a cause of PTC. The current study aimed to characterize PTC in children and investigate the possible role of acute viral infection of the central nervous system in its pathogenesis. A prospective, cross-sectional study was conducted in three centers in Israel. Participants were 50 children aged 0.5-18 years, of whom 27 had a definitive diagnosis of pseudotumor cerebri (the study group) and 23 comprised a control. Data collected included clinical presentation, imaging, treatment, ophthalmic findings, and cerebrospinal fluid (CSF) analysis. Using the ALLPLEX^TM meningitis panel, real-time polymerase chain reaction (PCR) was used to test for the presence of 12 common viruses. PTC patients (mean age 12 ± 4.3 years; 14 males, 13 females) had mean opening pressure of 41.9 ±10.2 mmH2O. All PTC patients had papilledema, and 25 (93%) had PTC symptoms. No viruses were found in the PTC group, while in the control group, one patient tested positive for Epstein-Barr virus and another for human herpesvirus type 6. Overall, in our study, PTC was not found to be associated with the presence of viruses in CSF.

Does enterovirus 71 urge for effective vaccine control strategies? Challenges and current opinion

Enterovirus 71 (EV71) is an infectious virus affecting all age groups of people around the world. It is one of the major aetiologic agents for HFMD (hand, foot and mouth disease) identified globally. It has led to many outbreaks and epidemics in Asian countries. Infection caused by this virus that can lead to serious psychological problems, heart diseases and respiratory issues in children younger than 10 years of age. Many studies are being carried out on the pathogenesis of the virus, but little is known. The host immune response and other molecular responses against the virus are also not clearly determined. This review deals with the interaction between the host and the EV71 virus. We discuss how the virus makes use of its proteins to affect the host's immunity and how the viral proteins help their replication. Additionally, we describe other useful resources that enable the virus to evade the host's immune responses. The knowledge of the viral structure and its interactions with host cells has led to the discovery of various drug targets for the treatment of the virus. Additionally, this review focusses on the antiviral drugs and vaccines developed by targeting various viral surface molecules during their infectious period. Furthermore, it is asserted that the improvement of prevailing vaccines will be the simplest method to manage EV71 infection swiftly. Therefore, we summarise numerous vaccines candidate for the EV71, such as the use of an inactivated complete virus, recombinant VP1 protein, artificial peptides, VLPs (viral-like particles) and live attenuated vaccines for combating the viral outbreaks promptly.

Cross-Antigenicity between EV71 Sub-Genotypes: Implications for Vaccine Efficacy

Enterovirus A-71 (EV71) is a global, highly contagkkious pathogen responsible for severe cases of hand-food-mouth-disease (HFMD). The use of vaccines eliciting cross neutralizing antibodies (NTAbs) against the different circulating EV71 sub-genotypes is important for preventing HFMD outbreaks. Here, we tested the cross-neutralizing activities induced by EV71 genotype/sub-genotype A, B0-B4, C1, C2, C4, and C5 viruses using rats. Differences were noted in the cross-neutralization of the 10 sub-genotypes tested but there were generally good levels of cross-neutralization except against genotype A virus, against which neutralization antibody titres (NTAb) where the lowest with NTAbs being the highest against sub-genotype B4. Moreover, NTAb responses induced by C4, B4, C1, and C2 viruses were homogenous, with values of maximum/minimum NTAb ratios (MAX/MIN) against all B and C viruses ranging between 4.0 and 6.0, whereas MAX/MIN values against B3 and A viruses were highly variable, 48.0 and 256.0, respectively. We then dissected the cross-neutralizing ability of sera from infants and children and rats immunized with C4 EV71 vaccines. Cross-neutralizing titers against the 10 sub-genotypes were good in both vaccinated infants and children and rats with the MAX/MIN ranging from 1.8–3.4 and 5.1–7.1, respectively, which were similar to those found in naturally infected patients (2.8). Therefore, we conclude that C4 EV71 vaccines can provide global protection to infants and children against HFMD caused by different sub-genotypes.

Safety Comparison of Two Enterovirus 71 (EV71) Inactivated Vaccines in Yiwu, China

The safety of two kinds of post-marketing enterovirus 71 (EV71) vaccine in China was evaluated in this study. Fourteen vaccination clinics were randomly assigned in a 1:1 ratio, and both children in two groups were administered according to a two-dose schedule (on a 0 and 28 day schedule). Written informed consent was obtained, and recipients in this study were observed for 30 min after inoculation in the clinic, and then followed via phone or on-site follow-up at day 3 and 30. No severe EV71-associated adverse event was reported. No significant difference was noticed between Group Sinovac and Group CAMS (χz = 0.346, p = 0.556). There was no significant difference in the occurrence of adverse events among recipients aged less than 24 months; however, the proportion of adverse events was higher in Group CAMS than in Group Sinovac among the subjects aged 24-35 months (5.3% vs. 2.5%, p < 0.001). The two kinds of EV71 vaccines showed satisfactory safety. Adverse events after vaccination were normal and acceptable.

An adult gerbil model for evaluating potential coxsackievirus A16 vaccine candidates

A suitable animal model of CVA16 infection is crucial in order to understand its pathogenesis and to help develop antiviral vaccines or screen therapeutic drugs. The neonatal mouse model has a short sensitivity period to CA16 infection, which is a major limitation. In this study, we demonstrate that adult (60-day-old) gerbils are susceptible to CVA16 infection at high doses (10^8.0 TCID₅₀). A clinical isolate strain of CVA16 was inoculated intraperitoneally into adult gerbils, which subsequently developed significant clinical symptoms, including hind limb weakness, paralysis of one or both hind limbs, tremors, and eventual death from neurological disorders. Real-time RT-PCR revealed that viral loads in the spinal cord and brainstem were higher than those in other organs/tissues. Histopathological changes, such as neuronal degeneration, neuronal loss, and neuronophagia, were observed in the spinal cord, brainstem, and heart muscle, along with necrotizing myositis. Gerbils receiving both prime and boost immunizations of alum adjuvant inactivated vaccine exhibited no clinical signs of disease or mortality following challenge by CVA16, whereas 80% of control animals showed obvious clinical signs, including slowness, paralysis of one or both hind limbs, and eventual death, suggesting that the CVA16 vaccine can fully protect gerbils against CVA16 challenge. These results demonstrate that an adult gerbil model provides us with a useful tool for studying the pathogenesis and evaluating antiviral reagents of CVA16 infection. The development of this animal model would also be conducive to screening promising CVA16 vaccine candidates as well as further vaccination evaluation.

Multifactorial analysis of opsoclonus-myoclonus syndrome etiology ("Tumor" vs. "No tumor") in a cohort of 356 US children

BACKGROUND

Pediatric opsoclonus-myoclonus syndrome (OMS) presents a paradox of etiopathogenesis: A neuroblastic tumor (NB) is found in only one half of the cases, the others are ascribed to infections or designated as idiopathic.

METHOD

From an IRB-approved observational study of 356 US children with OMS, secondary analysis of "etiology" and related factors was performed on a well-characterized cohort. The "Tumor" (n = 173) and "No Tumor" groups (n = 183), as defined radiologically, were compared according to multiple factors considered potentially differentiating. Data were analyzed retrospectively using parametric and nonparametric tests as indicated.

RESULTS

Patients with NB were not distinguishable by prodromal symptoms, OMS onset age, gender, race/ethnicity, OMS severity, rank order of neurological sign appearance, or geographic distribution. Various CSF immunologic biomarker abnormalities of OMS did not vary in the presence or absence of a detectable tumor: frequency of six lymphocyte subsets, or concentrations of 18 cytokines/chemokines, cytokine antagonists, chemokine receptors, cell adhesion molecules, or neuronal/glial markers. Prior responsiveness to conventional immunotherapy was not contingent on tumor/no tumor designation.

CONCLUSIONS

Multiple convergent factors provide compelling empirical evidence and rationalize the concept that OMS is one neurological disorder, regardless of apparent etiology. Limitations to the current clinical etiologic classifications as paraneoplastic, parainfectious/post-infectious, and idiopathic etiology require antigen-based biological solutions to tease out the molecular pathophysiology of viral/tumoral mechanisms. Systematic studies, regardless of presumed etiology, will be necessary to find the highest-yield combination of imaging approaches, screening for infectious agents, and new biomarkers. Two testable hypotheses for future research are presented.

Immunopathogenesis and Virus-Host Interactions of Enterovirus 71 in Patients with Hand, Foot and Mouth Disease

Enterovirus 71 (EV71) is a global infectious disease that affects millions of people. The virus is the main etiological agent for hand, foot, and mouth disease with outbreaks and epidemics being reported globally. Infection can cause severe neurological, cardiac, and respiratory problems in children under the age of 5. Despite on-going efforts, little is known about the pathogenesis of EV71, how the host immune system responds to the virus and the molecular mechanisms behind these responses. Moreover, current animal models remain limited, because they do not recapitulate similar disease patterns and symptoms observed in humans. In this review the role of the host-viral interactions of EV71 are discussed together with the various models available to examine: how EV71 utilizes its proteins to cleave host factors and proteins, aiding virus replication; how EV71 uses its own viral proteins to disrupt host immune responses and aid in its immune evasion. These discoveries along with others, such as the EV71 crystal structure, have provided possible targets for treatment and drug interventions.

An inactivated hand-foot-and-mouth disease vaccine using the enterovirus 71 (C4a) strain isolated from a Korean patient induces a strong immunogenic response in mice

Enterovirus 71 (EV71) is a major causative agent of hand-foot-and-mouth disease (HFMD) frequently occurring in children. HFMD induced by EV71 can cause serious health problems and has been reported worldwide, particularly in the Asia-Pacific region. In this study, we assessed the immunogenicity of a formalin-inactivated HFMD vaccine using an EV71 strain (FI-EV71 C4a) isolated from a Korean patient. The vaccine candidate was evaluated in mice to determine the vaccination doses and vaccine schedules. BALB/c mice were intramuscularly administered 5, 10, or 20 μg FI-EV71 vaccine, followed by a booster 2 weeks later. EV71-specific antibodies and neutralizing antibodies were induced and maintained until the end of the experimental period in all vaccinated groups. To determine the effectiveness of adjuvant for the EV71 vaccine, three adjuvants, i.e., aluminium hydroxide gel, monophosphoryl lipid A, and polyinosinic-polycytidylic acid, were administered separately with the FI-EV71 vaccine to mice via the intramuscular route. Mice administered the FI-EV71 vaccine formulated with all three adjuvants induced a significantly increased antibody response compared with that of the single adjuvant groups. The vaccinated group with triple adjuvants exhibited more rapid induction of EV71-specific and neutralizing antibodies than the other groups. These results suggested that the role of adjuvant in inactivated vaccine was important for eliciting effective immune responses against EV71. In conclusion, our results showed that FI-EV71 was a potential candidate vaccine for prevention of EV71 infection.

Increased Intracranial Pressure in the Setting of Enterovirus and Other Viral Meningitides

Increased intracranial pressure due to viral meningitis has not been widely discussed in the literature, although associations with Varicella and rarely Enterovirus have been described. Patients with increased intracranial pressure and cerebrospinal fluid analysis suggestive of a viral process are sometimes classified as having atypical idiopathic intracranial hypertension (IIH). However, a diagnosis of IIH requires normal cerebrospinal fluid, and therefore in these cases an infection with secondary intracranial hypertension may be a more likely diagnosis. Here seven patients are presented with elevated intracranial pressure and cerebrospinal fluid suggestive of viral or aseptic meningitis. Of these, 1 had Enterovirus and the remainder were diagnosed with nonspecific viral meningitis. These data suggest that viral meningitis may be associated with elevated intracranial pressure more often than is commonly recognized. Enterovirus has previously been associated with increased intracranial pressure only in rare case reports.

Children's Caregivers and Public Playgrounds: Potential Reservoirs of Infection of Hand-foot-and-mouth Disease

Hand-foot-and-mouth disease (HFMD) is a common infectious disease, which has led to millions of clinical cases and hundreds of deaths every year in China. This study aimed to exploring the effects on HFMD transmission of children’s caregivers and public area, as well as trying to locate the potential reservoirs of infections in primary cases. Total children’s 257 samples (98 children’s caregivers and 159 environmental samples) were tested for the presence of universal enterovirus, enterovirus 71, coxsackie virus A6 and A16 by real-time fluorescence quantitative polymerase chain reaction (qPCR). 5.84% (15/257, 95% confidence interval [CI]: 2.98%, 8.70%) of total samples had positive results of enterovirus. The enterovirus positive rates of children’s caregiver samples and environmental samples were respectively 7.14% (7/98, 95% CI: 2.04%, 12.24%), and 5.03% (8/159, 95% CI: 1.63%, 8.43%); 7.61% (7/92, 95% CI: 2.21%, 13.01%) of wiping samples from playgrounds and 1.49% (1/67, 95% CI: 0, 7.00%) of air samples in indoor market places had positive result of enterovirus. High positive rates of enterovirus in children’s caregivers and from playgrounds indicated that they would be potential reservoirs of HFMD infection, as children might be infected via contacting with asymptomatic-infected individuals or exposure of contaminated surface of public facilities.

Gan-Lu-Siao-Du-yin, a prescription of traditional Chinese medicine, inhibited enterovirus 71 replication, translation, and virus-induced cell apoptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Gan-Lu-Siao-Du-yin (GLSDY) is a prescription of traditional Chinese medicine. GLSDY contains 11 ingredients and is commonly used for endemic diseases. Enterovirus 71 (EV71) is an endemic disease that can cause meningoencephalitis with mortality and neurologic sequelae without any effective management. It is unknown whether GLSDY is effective against EV71 infection.

AIM OF THE STUDY

To test the hypothesis that GLSDY can protect cell from EV71-induced injury.

MATERIALS AND METHODS

Effects of a hot water extract of GLSDY on EV71 were tested in human foreskin fibroblast cells (CCFS-1/KMC) and human rhabdomyosarcoma cells (RD cells) by plaque reduction assay and flow cytometry respectively. Inhibition of viral replication was further examined by reverse quantitative RT-PCR (qRT-PCR). Its effect on viral protein translation and virus-induced apoptosis were examined by western blot.

RESULTS

GLSDY was dose-dependently effective against EV71 infection (p<0.0001) in both CCFS-1/KMC cells and RD cells. GLSDY was highly effective when supplemented after viral inoculation (P<0.0001) with an IC50 of 8.7μg/mL. GLSDY inhibited viral RNA replication (P<0.0001), formation of viral structural proteins (VP0, VP1, VP2 and VP3) and non-structural proteins (protease 2B and 3AB). Furthermore, 300μg/mL GLSDY is effective to inhibit virus-induced apoptosis possibly through direct inhibition of caspase-8 and indirectly by inhibition of Bax.

CONCLUSIONS

GLSDY is cheap and readily available to manage EV71 infection by inhibiting viral replication, viral protein formations, and EV71-induced apoptosis.

Genetic evolution of Human Enterovirus A71 subgenotype C4 in Shenzhen, China, 1998-2013

BACKGROUND

Human Enterovirus A71 (EV-A71) is one of the severest enteroviruses that causes hand, foot, and mouth disease (HFMD) among children. This study identified the mutations of EV-A71 VP1 amino acid residues over a number of years and explored the possible association of identified mutations and HFMD epidemic outbreaks in Shenzhen, China.

METHODS

A total of 3760 stool specimens were collected from HFMD patients by Shenzhen Centers for Disease Control and Prevention (CDC) between 1998 and 2013. In total 289 VP1 strains were sequenced in this study, and amino acids mutation frequency was calculated. There were 2040 China nationwide sequences downloaded from Genebank as replication data.

RESULTS

In our samples, 1036 subjects (27.6%) were EV-A71 infected. Three amino acid positions on VP1 protein were found to have high mutation prevalence. These are Q22H, S283T, and A289H. Site 22 showed a fast mutation fixation in the year 2008, at the time of the large scale epidemic outbreak in Shenzhen. Analysis of the nationwide data replicated the same trend of mutation prevalence of the three sites.

CONCLUSION

The switching from Q to H on site 22 of the EV-A71 VP1 strain might be associated with the HFMD outbreak in Shenzhen in 2008. The identified amino acid sites 22, 283 and 289 provided information for developing anti-viral drugs against EV-A71 in the future.

EV71 vaccine, a new tool to control outbreaks of hand, foot and mouth disease (HFMD)

On December 3rd 2015, the China Food and Drug Administration (CFDA) approved the first inactivated Enterovirus 71 (EV71) whole virus vaccine for preventing severe hand, foot and mouth disease (HFMD). As one of the few preventive vaccines for children's infectious diseases generated by the developing countries in recent years, EV71 vaccine is a blessing to children's health in China and worldwide. However, there are still a few challenges facing the worldwide use of EV71 vaccine, including the applicability against various EV71 pandemic strains in other countries, international requirements on vaccine production and quality control, standardization and harmonization on different pathogen monitoring and detecting methods, etc. In addition, the affordability of EV71 vaccine in other countries is a factor to be considered in HFMD prevention. Therefore, with EV71 vaccine commercially available, there is still a long way to go before reaching effective protection against severe HFMD after EV71 vaccines enter the market. In this paper, the bottlenecks and prospects for the wide use of EV71 vaccine after its approval are evaluated.

Two-year efficacy and immunogenicity of Sinovac Enterovirus 71 vaccine against hand, foot and mouth disease in children

OBJECTIVES

To evaluate the efficacy and immunogenicity of the Sinovac Enterovirus 71 (EV71) vaccine for up to two years.

METHODS

We did a follow-up study of our initial randomized trial in 10,077 participants, who were randomized to receive EV71 vaccine or placebo in a 1:1 ratio and followed for 14 months. The extended follow-up study lasted for another 12 months and EV71-associated hand, foot, and mouth disease (HFMD) was the primary endpoint.

RESULTS

The EV71 vaccine showed an efficacy of 95.1% (95%CI 63.6, 99.3) against EV71-associated HFMD during the extended follow-up and an overall efficacy of 94.7% (95%CI 87.8, 97.6) for two years. The EV71 vaccine elicited a sustained high level of neutralizing antibodies in participants, and no serious adverse event was judged to be related to the vaccination.

CONCLUSION

The Sinovac EV71 vaccine could provide a sustained high protection against EV71-associated HFMDs for up to 2 years.

Cytokine responses and correlations thereof with clinical profiles in children with enterovirus 71 infections

BACKGROUND

Severe complications associated with EV71 infections caused many infants death. However, the pathogenesis of EV71 infection in the severe cases remained poorly understood.

METHODS

In this study we collected plasma and cerebrospinal fluid (CSF) specimens drawn in the acute and/or recovery phases from EV71-infected individuals, and plasma specimens from healthy children served as normal controls. We compared the levels of cytokines and chemokines determined by a Luminex-based cytokine bead array.

RESULTS

The plasma levels of IL-1β and IL-6 were significantly higher in severe and critical cases than in mild patients and normal controls. Higher plasma levels of IL-6, IL-10, and IL-8 were evident in critical than severe cases. The CSF levels of IL-6, IL-8, and IP-10 were higher, and that of RANTES lower (compared to plasma), in severe and critical patients. Significantly lower CSF levels of cytokines and chemokines were recorded in the recovery than the acute phase in severe and critical cases treated with intravenous immunoglobulin (IVIG) and glucocorticoids. Only the CSF levels of IL-6, IP-10, and IL-8 were significantly correlated with white blood cell counts, and absolute neutrophil and monocyte counts, in severe cases. Furthermore, the CSF levels of IL-6 were correlated with temperature in both cases.

CONCLUSIONS

These data indicate that a major cytokine response and inflammation, in both plasma and the CNS, are features of disease caused by EV71 infection. Systemic inflammation caused by EV71 infection exacerbated the deterioration of the disease, and resulted in the disease progression to the critical illness stage.

Validation and utilization of an internally controlled multiplex Real-time RT-PCR assay for simultaneous detection of enteroviruses and enterovirus A71 associated with hand foot and mouth disease

Background

Hand foot and mouth disease (HFMD) is a disease of public health importance across the Asia-Pacific region. The disease is caused by enteroviruses (EVs), in particular enterovirus A71 (EV-A71). In EV-A71-associated HFMD, the infection is sometimes associated with severe manifestations including neurological involvement and fatal outcome. The availability of a robust diagnostic assay to distinguish EV-A71 from other EVs is important for patient management and outbreak response.

Methods

We developed and validated an internally controlled one-step single-tube real-time RT-PCR in terms of sensitivity, linearity, precision, and specificity for simultaneous detection of EVs and EV-A71. Subsequently, the assay was then applied on throat and rectal swabs sampled from 434 HFMD patients.

Results

The assay was evaluated using both plasmid DNA and viral RNA and has shown to be reproducible with a maximum assay variation of 4.41 % and sensitive with a limit of detection less than 10 copies of target template per reaction, while cross-reactivity with other EV serotypes was not observed. When compared against a published VP1 nested RT-PCR using 112 diagnostic throat and rectal swabs from 112 children with a clinical diagnosis of HFMD during 2014, the multiplex assay had a higher sensitivity and 100 % concordance with sequencing results which showed EVs in 77/112 (68.8 %) and EV-A71 in 7/112 (6.3 %). When applied to clinical diagnostics for 322 children, the assay detected EVs in throat swabs of 257/322 (79.8 %) of which EV-A71 was detected in 36/322 (11.2 %) children. The detection rate increased to 93.5 % (301/322) and 13.4 % (43/322) for EVs and EV-A71, respectively, when rectal swabs from 65 throat-negative children were further analyzed.

Conclusion

We have successfully developed and validated a sensitive internally controlled multiplex assay for rapid detection of EVs and EV-A71, which is useful for clinical management and outbreak control of HFMD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-015-0316-2) contains supplementary material, which is available to authorized users.

Massive pulmonary hemorrhage in enterovirus 71-infected hand, foot, and mouth disease

Hand, foot, and mouth disease (HFMD) is an acute, mostly self-limiting infection. Patients usually recover without any sequelae. However, a few cases are life threatening, especially those caused by enterovirus 71 (EV71). A 12-month-old boy was admitted to a primary hospital with high fever and vesicular lesions of the mouth, hands, and feet. After 3 days, he experienced 3 seizure episodes and was referred to our hospital. On admission, he was conscious and his chest radiograph was normal. However, 6 hours later, he suddenly lost consciousness and had developed a massive pulmonary hemorrhage that continued until his death. He experienced several more intermittent seizures, and diffuse infiltration of both lung fields was observed on chest radiography. Intravenous immunoglobulin, dexamethasone, cefotaxime, leukocyte-depleted red blood cells, fresh frozen plasma, inotropics, vitamin K, and endotracheal epinephrine were administered. The patient died 9 hours after intubation, within 3 days from fever onset. EV71 subgenotype C4a was isolated retrospectively from serum and nasopharyngeal swab by real-time reverse transcription-polymerase chain reaction. Here, we report a fatal case of EV71-associated HFMD with sudden-onset massive pulmonary hemorrhage and suspected encephalitis.

Performance of reversed transcription loop-mediated isothermal amplification technique detecting EV71: a systematic review with meta-analysis

Human enterovirus 71 (EV71) is the major etiological agent of hand, foot and mouth disease (HFMD), which is a common infectious disease in young children. Studies in the past have shown that reversed transcription loop-mediated isothermal amplification (RT-LAMP) was a rapid approach for the detection of EV71 in HFMD. This meta-analysis study is to evaluate the diagnostic role of RT-LAMP in detecting EV71 infection. A comprehensive literature research of PubMed, Embase, Wan Fang Data, and Chinese National Knowledge Infrastructure databases was conducted on articles aiming at the diagnostic performance of RT-LAMP in EV71 detection published before February 10, 2014. Data from selected studies were pooled to yield the summary sensitivity, specificity, positive and negative likelihood ratio (PLR, NLR), diagnostic odds ratio (DOR), and receiver operating characteristic (SROC) curve by using STATA VERSION 12.0 software. Ten studies including a total of 907 clinical samples were of high quality in this meta-analysis. Overall, the pooled sensitivity, specificity, PLR, NLR, DOR, and the area under the SROC curve was 0.99 (0.97, 1.00), 0.97 (0.94, 1.00), 5.90 (95% CI: 3.90-8.94), 0.20 (95% CI: 0.14-0.29), and 1.00 (95% CI: 0.99-1.00), respectively. The univariate analysis of potential variables showed some changes in the diagnostic performance, but none of the differences reached statistical significance. Despite inter-study variability, the test performance of RT-LAMP was consistent with real-time RT-PCR in detecting EV71. This meta-analysis suggests that RT-LAMP is a useful diagnostic tool with high sensitivity and specificity for detecting EV71.

Ocular Pathology: Role of Emerging Viruses in the Asia-Pacific Region-A Review

The role of viral infections in ocular pathology varies greatly, involving all the components of the eye. Some viruses like herpes simplex, herpes zoster, adenovirus, enterovirus 70, influenza virus, human immunodeficiency virus, and cytomegalovirus are well-known for their role in ocular pathology. In recent years, emerging and resurging viral infections represent an important public health problem. The Asia-Pacific region has witnessed a number of pandemic and epidemic outbreaks caused by these viruses during the last 2 decades. The number of ocular complications being reported in patients of these viral infections has also increased significantly during this period. Ophthalmologists and physicians should be aware of ocular manifestations of newly emerging or resurging viral diseases. We conducted a review of the literature published during the last 20 years with the objectives of finding out outbreaks of emerging and reemerging viruses in the Asia-Pacific region and finding out any ocular involvement in these viral infections. An iterative search of the MEDLINE and the Google databases was made using the search terms emerging virus, ocular manifestations, ocular complications, Chikungunya, Dengue, Japanese encephalitis, West Nile fever, Kyasanur forest disease, Rift valley fever, Hantavirus, Henipavirus, Influenza virus, Enterovirus 71, and Asia-Pacific region, separately and with reported ocular involvement in combination. This review article discusses the epidemiology and the systemic and ocular manifestations of all emerging viral infections with reported ocular involvement in the Asia-Pacific region.

Important roles of public playgrounds in the transmission of hand, foot, and mouth disease

Intra-home and kindergarten transmissions were the reported major modes of hand, foot, and mouth disease (HFMD) transmission in preschool children. However, infection at home is not common and 65–80% of cases do not attend preschool. We conducted a matched case-control study to explore the role of public playgrounds in the transmission of HFMD in addition to direct and indirect exposure to HFMD patients. We used 156 hospital source cases and 156 community source controls. Univariate analysis was followed by conditional logistic regression with attributable fraction computed. Adjusted odds ratios were 11·70 [95% confidence interval (CI) 1·26–109·40] for having HFMD cases in the same class, 14·19 (95% CI 3·55–56·74) for having HFMD cases within the 20 nearest neighbourhoods, 6·03 (95% CI 2·84–12·80) for exposure to public playgrounds, 2·13 (95% CI 1·05–4·32) for finger sucking and 0·29 (95% CI 0·11–0·78) for hand washing with soap before meals. The attributable fractions for the first four risk factors were 6·4%, 20·9%, 57·2% and 27·5%, respectively, while the population prevented fraction for hand washing with soap before meals was 18·7%. Based on our findings, hand washing with soap should be advocated. Health education could include topics which underline the precautions which need to be taken and the advice given regarding avoiding the use of public playgrounds during epidemic periods, especially when children have been getting sick.

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

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

A case of myocarditis following neonatal meningitis caused by coxsackievirus B1 in spite of intravenous immunoglobulin treatment

Enteroviral infection is one of the most common neonatal infections, and most patients recover without complications. This report describes a neonate who experienced meningitis followed by myocarditis. A 4-day-old boy was admitted with fever, diagnosed with enteroviral meningitis and treated with intravenous immunoglobulin (IVIG). However, myocarditis was subsequently diagnosed in spite of IVIG treatment, and coxsackievirus B1 (CXB1) was revealed as a cause. A left ventricular aneurysm persisted even though the patient recovered with repeated high-dose IVIG treatment and cardiac supportive care. This report describes a rare case where myocarditis developed several days after a diagnosis of CXB1 meningitis in spite of IVIG treatment. It is important to pay attention to the patient's clinical condition until the end of the second viremia of enterovirus and to consider high-dose IVIG treatment when treating enteroviral infections for neonates.

Development of enterovirus 71 vaccines: from the lab bench to Phase III clinical trials

The widespread epidemics of enterovirus 71 (EV71) seriously affected the Western Pacific Region. Young children, especially those younger than 3 years are the most susceptible population to the EV71-associated diseases. Several Asian countries have begun to focus on the research and development of EV71 vaccines. Five inactivated whole-virus EV71 candidate vaccines (three were manufactured in mainland China based on a C4 genotype strain, one in Taiwan based on a B4 genotype strain and one in Singapore based on a B2 genotype strain) have been assessed in clinical trials. Three candidate vaccines developed in mainland China have already completed Phase III clinical trials recently. The tested EV71 vaccine could provide good efficacy, satisfactory safety, and high immunogenicity. Thus, inactivated EV71 vaccines are expected to become the first available vaccines against EV71 in the near future.

Human rhinoviruses and enteroviruses in influenza-like illness in Latin America

Background

Human rhinoviruses (HRVs) belong to the Picornaviridae family with high similarity to human enteroviruses (HEVs). Limited data is available from Latin America regarding the clinical presentation and strains of these viruses in respiratory disease.

Methods

We collected nasopharyngeal swabs at clinics located in eight Latin American countries from 3,375 subjects aged 25 years or younger who presented with influenza-like illness.

Results

Our subjects had a median age of 3 years and a 1.2:1.0 male:female ratio. HRV was identified in 16% and HEV was identified in 3%. HRVs accounted for a higher frequency of isolates in those of younger age, in particular children < 1 years old. HRV-C accounted for 38% of all HRVs detected. Phylogenetic analysis revealed a high proportion of recombinant strains between HRV-A/HRV-C and between HEV-A/HEV-B. In addition, both EV-D68 and EV-A71 were identified.

Conclusions

In Latin America as in other regions, HRVs and HEVs account for a substantial proportion of respiratory viruses identified in young people with ILI, a finding that provides additional support for the development of pharmaceuticals and vaccines targeting these pathogens.

Patterns of polymorphism and divergence in the VP1 gene of enterovirus 71 circulating in the Asia-Pacific region between 1994 and 2013

Enterovirus 71 has been implicated in several outbreaks of hand, foot and mouth disease in the Asia-Pacific region. The present study aimed to achieve comprehensive evolutionary dynamic aspects of EV71 during 1994-2013, based on phylogenetic analyses of the VP1 sequences. The results indicated that 4 genotypes, namely C4, C1, C2 and B4 are the predominant strains, especially in Southeast Asian countries. No common ancestor was shared in different countries. Fourteen sites of substitutions were detected in the VP1 gene sequences; including the most common sites related to neutralization at position V249I [47.1% (189/401)] and A289T [42.6% (171/401)]. However, the sites Q22H and Q22R associated with increased virulence were recognized only in 13.7% (55/401) and 18% (72/401), respectively. None of the above mutations seemed to become fixed because the ratio of Ka/Ks was greater than 1.0. Mutations K43E, A58T, S184T, and T240S could possibly change the spatial structure. Two mutations, G145E and T240S, could obviously affect the hydrophobicity of VP1 and thus alter the EV71 immunoreactivity. In conclusion, the VP1 gene of EV71 strains circulating in the Asia-Pacific region during 1994-2013, showed polymorphisms and divergence with very slow evolution rate, which may be one of the reasons for periodic outbreaks in this area.

Development of a sandwich ELISA for the quantification of enterovirus 71

Since 2008, enterovirus 71 (EV71) has been responsible for high-mortality seasonal epidemics of hand, foot and mouth disease in China. Currently many groups in the world are in the process of developing EV71 vaccines to combat this deadly disease. We have developed three EV71-specific monoclonal antibodies, and in this study we report the establishment of a fast and cost-effective sandwich ELISA kit for measurement of virus concentration in EV71 vaccines using a pair of mouse anti-EV71 monoclonal antibodies. The system is specific for EV71 virus, with no cross-reactivity to coxsackievirus A16, H1N1, rabies, and hepatitis A. Using a reference EV71 vaccine standard, the sensitivity of the assay kit was determined to be 0.82 U/ml, with a linear range between 3.75 and 120 U/ml.

Complete genome sequencing and analysis of six enterovirus 71 strains with different clinical phenotypes

Background

Hand, foot and mouth diseases (HFMD) caused by enterovirus 71(EV71) presents a broad spectrum of clinical manifestations ranging from mild febrile disease to fatal neurolocal disease. However, the mechanism of virulence is unknown.

Methods

We isolated 6 strains of EV71 from HFMD patients with or without neurological symptoms, and sequenced the whole genomes of the viruses to reveal the virulence factors of EV71.

Results

Phylogenetic tree based on VP1 region showed that all six strains clustered into C4a of C4 sub-genotype. In the complete polypeptide, 298 positions were found to be variable in all strains, and three of these positions (Val^P814/Ile^P814 in VP1, Val^P1148/Ile^P1148 in 3A and Ala ^P1728/Cys ^P1728/Val ^P1728 in 3C) were conserved among the strains with neurovirulence, but variable in strains without neurovirulence. In the 5^′-UTR region, it showed that the first 10 nucleotides were mostly conserved, however from the 11th nucleotide, nucleotide insertions and deletions were quite common. The secondary structure prediction of 5^′-UTR sequences showed that two of three strains without neurovirulence (SDLY11 and SDLY48) were almost the same, and all strains with neurovirulence (SDLY96, SDLY107 and SDLY153) were different from each other. SDLY107 (a fatal strain) was found different from other strains on four positions (C^P241/T^P241, A^P571/T^P571, C^P579/T^P579 in 5^′-UTR and T^P7335/C^P7335 in 3^′-UTR).

Conclusions

The three positions (Val^P814/Ile^P814 in VP1, Val^P1148/Ile^P1148 in 3A and Ala ^P1728/Cys ^P1728/Val ^P1728 in 3C), were different between two phenotypes. These suggested that the three positions might be potential virulent positions. And the three varied positions were also found to be conserved in strains with neurovirulence, and variable in strains without neurovirulence. These might reveal that the conservation of two of the three positions or the three together were specific for the strains with neurovirulence. Varation of secondary structure of 5^′-UTR, might be correlated to the changes of viral virulence. SDLY107 (a fatal strain) was found different from other strains on four positions, these positions might be related with death.

Progress on the research and development of human enterovirus 71 (EV71) vaccines

Enterovirus 71 (EV71) infections, which can cause severe complications, have become one of the serious public health issues in the Western Pacific region and China. To date, a number of pharmaceutical companies and institutes have initiated the research and development of EV71 vaccines as a countermeasure. As is the case with innovative vaccine development, there are several critical bottlenecks in EV71 vaccine development that must be overcome before the clinical trials, including the selection of vaccine strain, standardization of the procedure for quantifying neutralizing antibody (NTAb) and antigen, establishment and application of a reference standard and biological standards, development of animal models for the evaluation of protective efficacy, and identification of the target patient population. To tackle these technical obstacles, researchers in Mainland of China have conducted a series of studies concerning the screening of vaccine strains and the establishment of criteria, biological standards and detection methods, thereby advancing EV71 vaccine development. This review summarizes recent worldwide progress on the quality control and evaluation of EV71 vaccines.

Comparative analysis of the immunogenicity and protective effects of inactivated EV71 vaccines in mice

Background

Enterovirus 71 (EV71) is the major causative agent of hand, foot, and mouth disease (HFMD). Three inactivated EV71 whole-virus vaccines of different strains developed by different manufacturers in mainland China have recently entered clinical trials. Although several studies on these vaccines have been published, a study directly comparing the immunogenicity and protective effects among them has not been carried out, which makes evaluating their relative effectiveness difficult. Thus, properly comparing newly developed vaccines has become a priority, especially in China.

Methods and Findings

This comparative immunogenicity study was carried out on vaccine strains (both live and inactivated), final container products (FCPs) without adjuvant, and corresponding FCPs containing adjuvant (FCP-As) produced by three manufacturers. These vaccines were evaluated by neutralizing antibody (NAb) responses induced by the same or different dosages at one or multiple time points post-immunization. The protective efficacy of the three vaccines was also determined in one-day-old ICR mice born to immunized female mice. Survival rates were observed in these suckling mice after challenge with 20 LD₅₀ of EV71/048M3C2. Three FCP-As, in a dose of 200 U, generated nearly 100% NAb positivity rates and similar geometric mean titers (GMTs), especially at 14–21 days post-inoculation. However, the dynamic NAb responses were different among three vaccine strains or three FCPs. The FCP-As at the lowest dose used in clinical trials (162 U) showed good protective effects in suckling mice against lethal challenge (90–100% survival), while the ED₅₀ of NAb responses and protective effects varied among three FCP-As.

Conclusions

These studies establish a standard method for measuring the immunogenicity of EV71 vaccines in mice. The data generated from our mouse model study indicated a clear dose-response relationship, which is important for vaccine quality control and assessment, especially for predicting protective efficacy in humans when combined with future clinical trial results.

Excessive proinflammatory cytokine and chemokine responses of human monocyte-derived macrophages to enterovirus 71 infection

BACKGROUND

The levels of proinflammatory cytokine or chemokine in blood and cerebrospinal fluid are thought to be one of predictors for clinical severity of enterovirus 71 (EV71) infection, yet the cellular sources or signalling mechanism remain undefined. Here, we focused on the response of human primary monocyte-derived macrophages (MDMs) to EV71 virus and its possible mechanisms.

METHODS

Human primary MDMs were infected by EV71 virus in vitro. Infectivity and viral replication were assayed, and cytokine responses were determined by Cytometric Bead Array(CBA) analysis. The relative changes of Toll-like receptors, retinoic acid-inducible gene I (RIG-I) and melamoma differentiation associated gene 5 (MDA5) mRNA expression were detected by real-time RT-PCR.

RESULTS

Effective infection and viral replication were detected in EV71-infected MDMs. The titters of progeny virus released from EV71-infected MDMs gradually increased from 6-h to 48-h point of infection (POI.). Proinflammatory cytokines: IL-1, IL-6, TNF-α but not IFN-α and γ were induced in MDMs by EV71. EV71 infection significantly increased the release of IL-8, IP-10 and RANTES at 12-h or 24-h POI. Upregulation of TLR2, TLR7 and TLR8 mRNA expression rather than TLR3, TLR4, TLR6, TLR9, TLR10, RIG-I, MDA5 were found at different time points in EV71-infected MDMs.

CONCLUSIONS

Our findings suggested that macrophages are not only the important target cells but also the effectors during EV71 infection, and they may play an important role in the pathogenesis of EV71 infection. And the proinflammatory cytokine and chemokine responses in EV71-infected MDMs may be mediated by the activation of differential pattern of TLRs.

Hand, foot and mouth disease in Yunnan Province, China, 2008-2010

This study was done to assess the epidemic features of hand, foot and mouth disease in Yunnan Province. Surveillance data from the beginning of 2008 through the end of 2010 were analyzed to conduct the demographic data of patients and morbidity as well as the estimation between possible risk factors for severe or fatal cases. Of the 75109 cases reported, laboratory tests confirmed 3691 cases. Thus, the average annual incidence proportion was 55 per 100000 population with a total case fatality rate of 0.04%. A seasonal peak was observed in May, along with a smaller winter peak in 2010. Most severe and fatal cases were caused by enterovirus 71. It is demonstrated that most of the severe and fatal cases occurred in very young children and that delayed access to health care led to the higher likelihood of serious illness.