Characterization of enterovirus 71 and coxsackievirus A16 isolated in hand, foot, and mouth disease patients in Guangdong, 2010

Testosterone Promotes the Intestinal Replication and Dissemination of Coxsackievirus B3 in an Oral Inoculation Mouse Model

Enteroviruses initiate infection in the gastrointestinal tract, and sex is often a biological variable that impacts pathogenesis. Previous data suggest that sex hormones can influence the intestinal replication of Coxsackievirus B3 (CVB3), an enterovirus in the Picornaviridae family. However, the specific sex hormone(s) that regulates intestinal CVB3 replication is poorly understood. To determine if testosterone promotes intestinal CVB3 replication, we orally inoculated male and female Ifnar^-/- mice that were treated with either placebo or testosterone-filled capsules. Following oral inoculation, we found that the testosterone-treated male and female mice shed significantly more CVB3 in their feces than did the placebo-treated mice, indicating that testosterone enhances intestinal replication. Similarly, testosterone enhanced viral dissemination in both sexes, as we observed higher viral loads in peripheral tissues following infection. Further, the testosterone-treated male mice also had a higher mortality rate than did the testosterone-depleted male mice. Finally, we observed that testosterone significantly affected the immune response to CVB3. We found that testosterone broadly increased proinflammatory cytokines and chemokines while decreasing the number of splenic B cells and dendritic cells following CVB3 infection. Moreover, while testosterone did not affect the early CD4 T cell response to CVB3, testosterone reduced the activation of CD8 T cells. These data indicate that testosterone can promote intestinal CVB3 replication and dissemination while also impacting the subsequent viral immune response. IMPORTANCE Biological sex plays a significant role in the outcomes of various infections and diseases. The impact of sex hormones on the intestinal replication and dissemination of Coxsackievirus B3 remains poorly understood. Using an oral inoculation model, we found that testosterone enhances CVB3 shedding and dissemination in male and female mice. Further, testosterone can alter the immune response to CVB3. This work highlights the role of testosterone in CVB3 pathogenesis and suggests that sex hormones can impact the replication and dissemination of enteric viruses.

Development and evaluation of an inactivated Coxsackievirus A16 vaccine in gerbils

Coxsackievirus A16 (CVA16) is one of the major pathogens responsible for human hand, foot, and mouth disease (HFMD), which has threatened the health of young children, particularly in Asia-Pacific nations. Vaccination is an effective strategy for protecting children from CVA16 infection. However, there is currently no licensed CVA16 vaccine for use in humans. In this study, we isolated a high-growth CVA16 virus strain in MRC-5 cells and developed an MRC-5-adapted vaccine candidate strain termed CVA16-393 via two rounds of plaque purification. The CVA16-393 strain was grouped into the B1b subgenotype and grew to a titre of over 10⁷ TCID₅₀/ml in MRC-5 cells. The VP1 gene region of this strain, which contains the major neutralizing epitopes, displayed high stability during serial passages. The inactivated whole-virus vaccine produced by the CVA16-393 strain induced an effective neutralizing antibody response in Meriones unguiculatus (gerbils) after two doses of intraperitoneal inoculation. One week after the booster immunization, the geometric mean titres of the neutralizing antibodies for the 10246, 40812TXT, 11203SD, TJ-224 and CA16-194 strains from different regions of China were 137.8, 97.8, 113.4, 64.1 and 122.3, respectively. A CVA16 vaccine dose above 25 U was also able to provide 100% cross-protection against lethal challenges with these five clinical strains in gerbils. Immunization at a one-week interval could maintain a high level of neutralizing antibody titres for at least 8 weeks. Thus, the vaccine produced by this CVA16-393 strain might be promising.

Dynamic changes of viral load and the duration of viral shedding in patients with hand, foot and mouth disease: a protocol for longitudinal study

Background

The duration of virus shedding is necessary for determining the infectious period. But there were few quantitative studies on the changes of viral load and the law of the viral shedding in hand foot and mouth disease (HFMD) patients has not yet been clarified.

Methods

This study will prospectively recruit coxsackievirus A10 (CV-A10), coxsackievirus A16 (CV-A16) and coxsackievirus A6 (CV-A6) infected inpatients from January 2022 to December 2022. A series of samples and questionnaire information will be collected regularly to establish the dynamic function relationship between time and viral load changes and a Bayesian multilevel model will be constructed to clarify the evolvement rules which reflect the dynamic changes of viral load and the duration of viral shedding in patients with HFMD.

Discussion

The results of this study is expected to further clarify the evolvement rules which reflect the dynamic changes of viral load and the duration of viral shedding in HFMD patients under the influence of related factors. It can also provide important evidence for the scientific definition of the infectious period and isolation period of HFMD in China.

Co-circulation of coxsackieviruses A-6, A-10, and A-16 causes hand, foot, and mouth disease in Guangzhou city, China

Background

Hand, foot, and mouth disease (HFMD) is a common infectious disease occurring in children under 5 years of age worldwide, and Enterovirus A71 (EV-A71) and Coxsackievirus A16 (CVA-16) are identified as the predominant pathogens. In recent years, Coxsackievirus A6 (CVA-6) and Coxsackievirus A10 (CVA-10) have played more and more important role in a series of HFMD outbreaks. This study aimed to understand the epidemic characteristics associated with HFMD outbreak in Guangzhou, 2018.

Methods

The clinical and laboratory data of 1220 enterovirus-associated HFMD patients in 2018 were analysed in this study. Molecular diagnostic methods were performed to identify its serotypes. Phylogenetic analyses were depicted based on the complete VP1 gene.

Results

There were 21 enterovirus serotypes detected in Guangzhou in 2018. Three serotypes of enterovirus, CVA-6 (364/1220, 29.8%), CVA-10 (305/1220, 25.0%), and CVA-16 (397/1220, 32.5%), were identified as the causative pathogens and accounted for 87.3% among all 1220 HFMD patients. In different seasons, CVA-6 was the predominant pathogen of HFMD during autumn, and CVA-10 as well as CVA-16 were more prevalent in summer. Patients infected by CVA-6, CVA-10 or CVA-16 showed similar clinical features and laboratory characteristics, and the ratios of severe HFMD were 5.8, 5.9, and 1.5% in the three serotypes. Phylogenetic analyses of VP1 sequences showed that the CVA-6, CVA-10, and CVA-16 sequences belonged to the sub-genogroup E2, genogroup E, and genogroup B1, respectively.

Conclusions

CVA-6, CVA-10, and CVA-16 were the predominant and co-circulated serotypes in Guangzhou China, 2018, which should be the new target for prevention and control of HFMD. Our findings provide useful information for diagnosis, treatment, and prevention of HFMD.

Coxsackievirus A16 in a 1-Day-Old Mouse Model of Central Nervous System Infection Shows Lower Neurovirulence than Enterovirus A71

Coxsackievirus A16 (CV-A16) and enterovirus A71 (EV-A71) are the major causes of hand, foot and mouth disease in young children. Although less so with CV-A16, both viruses are associated with serious neurological syndromes, but the differences between their central nervous system infections remain unclear. We conducted a comparative infection study using clinically-isolated CV-A16 and EV-A71 strains in a 1-day-old mouse model to better understand the neuropathology and neurovirulence of the viruses. New serotype-specific probes for in situ hybridization were developed and validated to detect CV-A16 and EV-A71 RNA in infected tissues. Demonstration of CV-A16 virus antigens/RNA, mainly in the brainstem and spinal cord neurons, confirmed neurovirulence, but showed lower densities than in EV-A71 infected animals. A higher lethal dose₅₀ for CV-A16 suggested that CV-A16 is less neurovirulent. Focal virus antigens/RNA in the anterior horn white matter and adjacent efferent motor nerves suggested that neuroinvasion is possibly via retrograde axonal transport in peripheral motor nerves.

Acarbose, as a potential drug, effectively blocked the dynamic metastasis of EV71 from the intestine to the whole body

Enterovirus 71 (EV71) is one of the main pathogens causing hand-foot-and-mouth disease (HFMD). The nose and mouth are usually the main infection entries of EV71 virus. However, its dynamic transport pathway from mouth to the whole body remains unknown. The reveal of this physiological mechanism in vivo will help to understand its transport direction, find its key proliferation nodes, and develop new preventive strategies. We trained a new strain of GFP-EV71 virus to be susceptible to mice brain by intracranial injection of mice. The adapted virus was oral-administrated to suckling mice. Then, the dynamic distributions of the virus in vivo were detected by living image system and fluorescence quantitation polymerase chain reaction (qPCR). We figured out the dynamic pathway of EV71 transport in vivo from intestine to peripheral tissue, then to the other organs. Small intestine was identified as a gateway for EV71 infection in vivo. Ileum was proved to be the main part of proliferation and transport of EV71 in small intestine of mice. EV71 was verified to enter small intestinal villus of mice through the infection of small intestinal epithelial cell. Acarbose displayed a good preventive effect on EV71 infection both in vivo and in vitro. Acarbose possibly decreased the intestinal infection of EV71 by blocking the receptor-binding sites on the surface of EV71 virion or by inhibiting various glycolic receptors on the cell surface. Thus, acarbose and its analogue may be the potential medicines to prevent EV71 infection.

Related Enteric Viruses Have Different Requirements for Host Microbiota in Mice

Accumulating evidence suggests that intestinal bacteria promote enteric virus infection in mice. For example, previous work demonstrated that antibiotic treatment of mice prior to oral infection with poliovirus reduced viral replication and pathogenesis. Here, we examined the effect of antibiotic treatment on infection with coxsackievirus B3 (CVB3), a picornavirus closely related to poliovirus. We treated mice with a mixture of five antibiotics to deplete host microbiota and examined CVB3 replication and pathogenesis following oral inoculation. We found that, as seen with poliovirus, CVB3 shedding and pathogenesis were reduced in antibiotic-treated mice. While treatment with just two antibiotics, vancomycin and ampicillin, was sufficient to reduce CVB3 replication and pathogenesis, this treatment had no effect on poliovirus. The quantity and composition of bacterial communities were altered by treatment with the five-antibiotic cocktail and by treatment with vancomycin and ampicillin. To determine whether more-subtle changes in bacterial populations impact viral replication, we examined viral infection in mice treated with milder antibiotic regimens. Mice treated with one-tenth the standard concentration of the normal antibiotic cocktail supported replication of poliovirus but not CVB3. Importantly, a single dose of one antibiotic, streptomycin, was sufficient to reduce CVB3 shedding and pathogenesis while having no effect on poliovirus shedding and pathogenesis. Overall, replication and pathogenesis of CVB3 are more sensitive to antibiotic treatment than poliovirus, indicating that closely related viruses may differ with respect to their reliance on microbiota.IMPORTANCE Recent data indicate that intestinal bacteria promote intestinal infection of several enteric viruses. Here, we show that coxsackievirus, an enteric virus in the picornavirus family, also relies on microbiota for intestinal replication and pathogenesis. Relatively minor depletion of the microbiota was sufficient to decrease coxsackievirus infection, while poliovirus infection was unaffected. Surprisingly, a single dose of one antibiotic was sufficient to reduce coxsackievirus infection. Therefore, these data indicate that closely related viruses may differ with respect to their reliance on microbiota.

Estimation of the reproduction number and identification of periodicity for HFMD infections in northwest China

Repeated outbreaks of Hand, foot and mouth disease (HFMD) infections have been observed in recent decades and dominated by various enteroviral serotypes. In particular, enterovirus 71 (EV-A71), coxsackievirus A16 (CV-A16) and coxsackievirus A6 (CV-A6) dominated the prevalence of HFMD infections alternatively in recent years with various outbreak sizes in Baoji, a city of Shaanxi Province in Northwest China. Estimating the reproduction number for various enteroviruses serotypes in northwest China (north temperate zone) and identification of cyclicity of HFMD infections are therefore an issue of great importance for future epidemics prediction and control. The basic/effective reproduction numbers for EV-A71, CV-A16 and CV-A6 were estimated based on daily new cases in 2010, 2011 and 2018, respectively, in which the corresponding pathogen dominated the epidemic. Two different methods based on serial interval were adopted and the basic reproduction number were estimated to be in the range of (1.33, 1.46) for CV-A16, (1.20, 1.29) for EV-A71, and (1.38, 1.59) for CV-A6, respectively. The estimated daily effective reproduction numbers significantly fluctuated before June or after July but varied mildly in (0.5,2) in around June to July for three serotypes. The weekly effective reproduction number for HFMD was estimated based on weekly new cases from year 2010 to 2018, and in most years it peaked in the range of (1.6,2.0) in February to March as well as in the range of (1.0,1.2) in September to October. The wavelet analysis based on the time series of HFMD cases from 2008 to 2018 showed obvious annual and semi-annual cyclicity, while the inter-annual cycles are infeasible. In this study we found that CV-A6 shows the greatest transmission ability among these three pathogens while EV-A71 exhibits the weakest ability of transmission, and moreover, the estimated values of basic reproduction number in northwest China are lower than those in Singapore, Hongkong and Guangdong, which may be due to different climatic circumstances.

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.

Longitudinal study on enterovirus A71 and coxsackievirus A16 genotype/subgenotype replacements in hand, foot and mouth disease patients in Thailand, 2000-2017

BACKGROUND

Enterovirus A71 (EV-A71) and coxsackievirus A16 (CV-A16) are the major causative agents of hand, foot and mouth disease (HFMD) worldwide, particularly in the Asia-Pacific region. Several strains have emerged, circulated, and faded out over time in recent decades. This study investigated the EV-A71 and CV-A16 circulating strains and replacement of genotypes/subgenotypes in Thailand during the years 2000-2017.

METHODS

The complete VP1 regions of 92 enteroviruses obtained from 90 HFMD patients, one asymptomatic adult contact case, and one encephalitic case were sequenced and investigated for serotypes, genotypes, and subgenotypes using a phylogenetic analysis.

RESULTS

The 92 enterovirus isolates were identified as 67 (72.8%) EV-A71 strains comprising subgenotypes B4, B5, C1, C2, C4a, C4b and C5, and 25 (27.2%) CV-A16 strains comprising subgenotypes B1a and B1b. Genotypic/subgenotypic replacements were evidenced during the study period. EV-A71 B5 and C4a have been the major circulating strains in Thailand for more than a decade, and CV-A16 B1a has been circulating for almost two decades.

CONCLUSIONS

This study provides chronological data on the molecular epidemiology of EV-A71 and CV-A16 subgenotypes in Thailand. Subgenotypic replacement frequently occurred with EV-A71, but not CV-A16. Monitoring for viral genetic and subgenotypic changes is important for molecular diagnosis, vaccine selection, and vaccine development.

Molecular epidemiology and clinical features of hand, foot and mouth disease in northern Thailand in 2016: a prospective cohort study

Background

Hand, foot and mouth disease (HFMD) is a major communicable disease in children ≤6 years old, particularly in several countries in the Asia-Pacific Region, including Thailand. HFMD impacts public health and the economy, especially in northern Thailand.

Methods

A prospective cohort study was conducted to estimate the incidence rate and to identify the serotype and clinical features of HFMD among children in northern Thailand. A validated questionnaire and throat swab were used for data collection. Polymerase chain reaction (PCR) was used to detect human enterovirus and identify its serotypes. Participants were recruited from 14 hospitals in two provinces in northern Thailand, specifically, Chiang Rai and Pha Yao Province, between January 1, 2016, and December 31, 2016. Chi-square or Fisher’s exact test was used to detect the associations of signs and symptoms with HFMD serotype. Logistic regression was used to detect the associations of variables with a positive enterovirus at alpha = 0.05.

Result

In total, 612 children aged ≤6 years from Chiang Rai and Pha Yao Province who were diagnosed with HFMD by a throat swab were recruited for the analysis. Approximately half of the cohort was male (57.2%), 57.5% was aged < 2 years, and 57.5% lived in rural areas. The incidence rate was 279.72/100,000 person-years in Chiang Rai Province and 321.24 per 100,000 person-years in Pha Yao Province. Additionally, 42.5% of children were positive for human enterovirus; among these children, 56.1% were positive for enterovirus-A (EV-A), 17.7% were positive for coxsackievirus (CV), and 26.2% were positive for other human RNA enteroviruses. During the study period, 21 distinct outbreaks of HFMD were recognized. Four to five patients (total 92 patients) were selected from each outbreak for identifying its serotype; enterovirus-A71 (EV-A71) was detected in 34.8% of HFMD cases, coxsackievirus-A16 (CV-A16) in 26.1%, coxsackivirus-A6 (CV-A6) in 15.2%, coxsackievirus-A10 (CV-A10) in 10.9%, coxsackievirus-A4 (CV-A4) in 2.2%, coxsackievirus-B2 (CV-B2) in 2.2%, human rhinovirus in 2.2%, and unknown serotype in 6.4%. Multivariable analysis demonstrated that a history of breastfeeding for ≤6 months was associated with a higher chance of enterovirus infection than a history of breastfeeding > 6 months, and children who had mother who worked as farmers, daily wage employees, and unprofessional skilled jobs had a greater chance of enterovirus infection than those who had unemployed mothers. Coxsackievirus-infected children had a higher rate of rashes on the buttocks, knee, and elbow and fever but a lower rate of lethargy and malaise than EV-A71-infected children.

Conclusions

EV-A71 is a major cause of HFMD in children < 6 years old in northern Thailand, but rash, fever, and mouth ulcers are mostly found in participants with coxsackievirus infection. Breastfeeding should be promoted during early childhood for at least 6 months to prevent HFMD particularly those mother who are working in unprofessional skill jobs.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3560-4) contains supplementary material, which is available to authorized users.

Large-scale HFMD epidemics caused by Coxsackievirus A16 in Bangalore, India during 2013 and 2015

Hand foot and mouth disease (HFMD) is a relatively unreported disease in India. This study was undertaken to characterize the enterovirus type/s associated with two unexpectedly-massive epidemics that occurred in Bangalore, India in 2013 and 2015. Stool samples of 229 children with HFMD living in Northern and Southern areas of Bangalore were tested by RT-PCR; 189 (82.5%) were enterovirus positive. The Indian CV-A16 strains exhibited 98-99% sequence identity with those reported in France and China in the 5' untranslated region. BLAST and phylogenetic analyses of complete genomes of representative Indian isolates revealed that the 2015 epidemic was predominated by an inter-species recombinant between CV-A16 and coxsackievirus B5. The 2013 epidemic was primarily caused by nonrecombinant strains. The CV-A16 strains circulated in India since 2007 and phylogeographic analyses indicated imported cases in France and China. In conclusion, CV-A16-associated HFMD epidemics should be recognized as an emerging public health problem in India.

Prevalence of enteroviruses in healthy populations and excretion of pathogens in patients with hand, foot, and mouth disease in a highly endemic area of southwest China

Etiological carriers and the excretion of the pathogens causing hand, foot, and mouth disease (HFMD) in healthy persons, patients, and asymptomatic persons infected with HFMD as ongoing infection sources may play an important role in perpetuating and spreading epidemics of HFMD. The aims of this study were to determine the carrier status of EV-A71 and CV-A16 in healthy populations, as well as the duration of EV-A71 and CV-A16 shedding in the stools of HFMD patients in an epidemic area of southwest China. A cross-sectional study and a follow-up study were conducted in three HFMD endemic counties of Yunnan Province. Six hundred sixty-seven healthy subjects were recruited to participate in the cross-sectional study, and two stool specimens were collected from each subject. Among the healthy subjects, 90 (13.5%) tested positive for viral isolation, but neither EV-A71 nor CV-A16 was detected in healthy individuals. Of the 150 patients with probable HFMD, 55.3% (83/150) tested positive for viral isolation with presented serotypes such as EV-A71 (51.81%, 43/83), CV-A16 (32.53%, 27/83), other EVs (13.25%, 11/83), and mixed EV-A71 and CV-A16 (2.41%, 2/83). The longest duration of EV-A71 and CV-A16 shedding in stool specimens from patients with HFMD was >46 days after onset. The positive rate of EV-A71 in the stool specimens of confirmed patients dropped to 50% by the end of the third week, and the same occurred with CV-A16 by the end of approximately the seventh week after onset. Although carriers of major causative agents of HFMD in healthy populations are fewer in number, the prolonged shedding of pathogens in patients with HFMD may serve as an important factor in perpetuating and spreading HFMD epidemics.

Human picornaviruses associated with neurological diseases and their neutralization by antibodies

Picornaviruses are the most commonly encountered infectious agents in mankind. They typically cause mild infections of the gastrointestinal or respiratory tract, but sometimes also invade the central nervous system. There, they can cause severe diseases with long-term sequelae and even be lethal. The most infamous picornavirus is poliovirus, for which significant epidemics of poliomyelitis were reported from the end of the nineteenth century. A successful vaccination campaign has brought poliovirus close to eradication, but neurological diseases caused by other picornaviruses have increasingly been reported since the late 1990s. In this review we focus on enterovirus 71, coxsackievirus A16, enterovirus 68 and human parechovirus 3, which have recently drawn attention because of their links to severe neurological diseases. We discuss the clinical relevance of these viruses and the primary role of humoral immunity in controlling them, and summarize current knowledge on the neutralization of such viruses by antibodies.

Sex-Dependent Intestinal Replication of an Enteric Virus

Coxsackievirus is an enteric virus that initiates infection in the gastrointestinal tract before disseminating to peripheral tissues to cause disease, but intestinal factors that influence viral replication are understudied. Furthermore, a sex bias for severe sequelae from coxsackievirus infections has been observed in humans. While mouse models mimicking human pathogenesis have been well characterized, many of these experiments use intraperitoneal injection of coxsackievirus to infect mice, bypassing the intestine. In light of recent studies identifying intestinal factors, such as the microbiota, that alter enteric viral replication, we sought to investigate coxsackievirus replication within the intestine. Here, we orally infected mice with coxsackievirus B3 (CVB3) and found that CVB3 replication in the intestine is sex dependent. CVB3 replicated efficiently in the intestine of male mice but not female mice. Additionally, we found that the type I interferon response and sex hormones can alter both viral replication and lethality. Overall, these data suggest that sex and the immune response play a vital role in CVB3 replication in the intestine and should be considered in light of the sex bias observed in human disease.IMPORTANCE Sex bias in severe sequelae from enteric viral infections has been observed. Since viruses have evolved to achieve optimal levels of fitness in their environmental niches, it is imperative to study viruses at the site of initial replication. Here, we used an oral inoculation system for CVB3, which follows the natural route of infection in the gastrointestinal tract. We found that sex can influence the replication of CVB3 in the intestine. Additionally, the type I interferon response and sex hormones alter both CVB3 intestinal replication and lethality. Overall this work highlights the fact that sex should be considered in investigations of enteric viral replication and pathogenesis.

The Epidemiology of Hand, Foot and Mouth Disease in Asia: A Systematic Review and Analysis

CONTEXT

Hand, foot and mouth disease (HFMD) is a widespread pediatric disease caused primarily by human enterovirus 71 (EV-A71) and Coxsackievirus A16 (CV-A16).

OBJECTIVE

This study reports a systematic review of the epidemiology of HFMD in Asia.

DATA SOURCES

PubMed, Web of Science and Google Scholar were searched up to December 2014.

STUDY SELECTION

Two reviewers independently assessed studies for epidemiologic and serologic information about prevalence and incidence of HFMD against predetermined inclusion/exclusion criteria.

DATA EXTRACTION

Two reviewers extracted answers for 8 specific research questions on HFMD epidemiology. The results are checked by 3 others.

RESULTS

HFMD is found to be seasonal in temperate Asia with a summer peak and in subtropical Asia with spring and fall peaks, but not in tropical Asia; evidence of a climatic role was identified for temperate Japan. Risk factors for HFMD include hygiene, age, gender and social contacts, but most studies were underpowered to adjust rigorously for confounding variables. Both community-level and school-level transmission have been implicated, but their relative importance for HFMD is inconclusive. Epidemiologic indices are poorly understood: No supporting quantitative evidence was found for the incubation period of EV-A71; the symptomatic rate of EV-A71/Coxsackievirus A16 infection was from 10% to 71% in 4 studies; while the basic reproduction number was between 1.1 and 5.5 in 3 studies. The uncertainty in these estimates inhibits their use for further analysis.

LIMITATIONS

Diversity of study designs complicates attempts to identify features of HFMD epidemiology.

CONCLUSIONS

Knowledge on HFMD remains insufficient to guide interventions such as the incorporation of an EV-A71 vaccine in pediatric vaccination schedules. Research is urgently needed to fill these gaps.

Epidemiological and genetic analysis of hand-foot-mouth disease by enterovirus A71 in Taizhou, P. R. China, between 2010 and 2013

Out of a population of 1,098 enteroviruses (EVs)-positive hand, foot, and mouth disease (HFMD) specimens, 352 were screened positive for EV-A71-accounting for 32.1% of all EV-positive specimens. This percentage denotes EV-A71 as the second major serotype of enteroviruse among HFMD suffers in Taizhou. An epidemic outbreak of EV-A71 among HFMD children was found in Taizhou in the second quarter of 2012. Phylogeny analysis based on the VP1 complete sequences leads us to find a sub-clade (designated TZ1-1) of EV-A71 circulating in Taizhou, whose emergence might be correlated with the epidemic outbreak. This correlation was further supported by the followed two analyses (namely skyline plot of population history and birth-death SIR simulation of epidemic history). And more importantly, at a positively selected site of VP1 caspid, a mutation of N31D was found to be a synapomorphy of TZ1-1 and its occurrence might be correlated with the epidemic outbreak. J. Med. Virol. 89:782-790, 2017. © 2016 Wiley Periodicals, Inc.

Outbreak of hand, foot, and mouth disease caused by coxsackievirus A6 in a Juku in Fengtai District, Beijing, China, 2015

An outbreak of hand, foot, and mouth disease (HFMD) that occurred in a Juku in Fengtai District, Beijing, China, in 2015 was monitored by the China Information System for Disease Control and Prevention. Epidemiological investigation showed that 11 cases occurred from two classes in the preschool art training department in the Juku. Coxsackievirus A6 (CV-A6) was identified as the causative pathogen of the outbreak via sequences analysis of products of real-time reverse-transcription polymerase chain reaction (RT-PCR) and nested RT-PCR. Phylogenetic analysis showed that CV-A6 strains isolated in this study clustered with epidemic strains isolated in China since 2013. The outbreak ended quickly with effective measures. This event indicates that continuous surveillance of HFMD etiological agents other than enterovirus 71 and coxsackievirus A16 is necessary.

Molecular epidemiology of human enterovirus 71 at the origin of an epidemic of fatal hand, foot and mouth disease cases in Cambodia

Human enterovirus 71 (EV-A71) causes hand, foot and mouth disease (HFMD). EV-A71 circulates in many countries and has caused large epidemics, especially in the Asia-Pacific region, since 1997. In April 2012, an undiagnosed fatal disease with neurological involvement and respiratory distress occurred in young children admitted to the Kantha Bopha Children's Hospital in Phnom Penh, Cambodia. Most died within a day of hospital admission, causing public panic and international concern. In this study, we describe the enterovirus (EV) genotypes that were isolated during the outbreak in 2012 and the following year. From June 2012 to November 2013, 312 specimens were collected from hospitalized and ambulatory patients and tested by generic EV and specific EV-A71 reverse transcription PCR. EV-A71 was detected in 208 clinical specimens while other EVs were found in 32 patients. The VP1 gene and/or the complete genome were generated. Our phylogenetic sequencing analysis demonstrated that 80 EV-A71 strains belonged to the C4a subgenotype and 3 EV-A71 strains belonged to the B5 genotype. Furthermore, some lineages of EV-A71 were found to have appeared in Cambodia following separate introductions from neighboring countries. Nineteen EV A (CV-A6 and CV-A16), 9 EV B (EV-B83, CV-B3, CV-B2, CV-A9, E-31, E-2 and EV-B80) and 4 EV C (EV-C116, EV-C96, CV-A20 and Vaccine-related PV-3) strains were also detected. We found no molecular markers of disease severity. We report here that EV-A71 genotype C4 was the main etiological agent of a large outbreak of HFMD and particularly of severe forms associated with central nervous system infections. The role played by other EVs in the epidemic could not be clearly established.

MA104 Cell line presents characteristics suitable for enterovirus A71 isolation and proliferation

Enterovirus A71 (EV-A71), one of the most important causative agents of hand, foot and mouth disease (HFMD) in children, can lead to severe clinical outcomes, even death. However, the infection spectrum of EV-A71 in different cell lines remains unknown. Therefore, in this study, the biological characteristics of EV-A71 Subgroup C4 in different cell lines were investigated. To this end, the infectivity of EV-A71Jinan1002 isolated from children with severe HFMD was assessed in 18 different host cell lines. It was found that the MA104 cell line displayed biological characteristics suitable for EV-A71 Subgroup C4 strain isolation and proliferation; indeed, it was found that a broad spectrum of cell lines can be infected by EV-A71Jinan1002. Among the screened cells, four cell lines (HEK293, RD, MA104 and Marc145) produced high 50% tissue culture infective dose (TCID50 ) values calculated in viral proliferations (ranged from 10(7.6) to 10(7.8) ); the TCID50 being negatively associated with the time to appearance of CPE. Proliferation curves demonstrated that EV-A71Jinan1002 amplifies more efficiently in MA104, Hep-2 and RD cells. Remarkably, the virus isolation rate was much higher in MA104 cells than in RD cells. Thus this study, to our knowledge, is for the first to explore the infection spectrum of EV-A71 subgroup C4 in such a large number of different cell lines. Our data provide useful reference data for facilitating further study of EV-A71.

Genomic features of coxsackievirus A6 correlate with herpangina and hand, foot and mouth disease

Aim: To study the genomic factors of coxsackievirus A6 (CVA6) correlated with herpangina and hand, foot and mouth disease (HFMD). Materials & methods: Complete genome of CVA6 strains and HFMD causing enteroviruses were enrolled for genomic comparisons. Results: Recombinations in the nonstructural P2-P3 region appeared to correlate with HFMD causing pathogenicity. Among nonrecombinant CVA6 strains, a markedly nucleotide diversity in 3C-3UTR was observed between herpangina and HFMD causing CVA6. Synonymous mutations take an important role in the evolution of CVA6 3C-3UTR region, as limited amino acid variations were resulted from the high nucleotide diversity. Key amino acid mutations at positions 168–170 of 3D protein were correlated with the differences in viral pathogenicities. Conclusion: These findings provide insights into viral genomic features correlated with CVA6 pathogenicities.

Serum cholinesterase: a potential assistant biomarker for hand, foot, and mouth disease caused by enterovirus 71 infection

Background

Hand, foot, and mouth disease (HFMD) caused by enterovirus 71 (EV71) is a potentially life-threatening infectious disease that commonly occurs in children. Diagnosis of HFMD caused by EV71 largely depends on clinical manifestations and rare serological biomarkers used to identify children suffering from HFMD. Serum cholinesterase (SChE) activity has frequently been reported as a potential biomarker for solid central nervous system tumors, chronic heart failure, and liver cirrhosis. However, its potential value in the diagnosis of neurotropic virus infections, such as HFMD caused by EV71, remains to be determined.

Findings

In our study, 220 children hospitalized with HFMD caused by EV71, 34 inpatients infected with coxsackievirus A16 (CVA16), and 43 undefined enterovirus-infected HFMD inpatients were recruited at the Anhui Provincial Children’s Hospital between January 2011 and December 2012. SChE activity was measured. The non-parametric Mann–Whitney U test showed that SChE activity in children diagnosed with HFMD caused by EV71 was significantly higher than in healthy controls (p < 0.001), as well as in children with upper respiratory tract infections (p = 0.011), bronchopneumonia (p < 0.001), septicemia (p < 0.001), amygdalitis (p < 0.001), and appendicitis (p < 0.001). In addition, higher SChE activity was observed in male inpatients with HFMD caused by EV71 (47.7 % positivity) compared to female inpatients (26.1 % positivity) (chi-square test, p = 0.002). In our study, no significant differences in SChE levels were observed among different ages (up to 120 months) (r = -0.112, p > 0.05). An important finding was that SChE activity declined in the recovery phase of HFMD caused by EV71 compared to the acute phase (p < 0.001).

Conclusions

Elevated SChE activity was observed in patients with severe HFMD caused by EV71. Therefore, SChE might be a potential assistant biomarker for the diagnosis of HFMD caused by EV71 in children.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-016-0124-y) contains supplementary material, which is available to authorized users.

Protein microarray-mediated detection of antienterovirus antibodies in serum

Objective

To utilize prokaryotic gene expression and protein microarray to develop and evaluate a sensitive, accurate protein microarray assay for detecting antienterovirus antibodies in serum samples from patients with hand, foot and mouth disease (HFMD). Enterovirus 71 (EV71) and coxsackievirus A16 (CA16), two common causative agents for HFMD, were used for assay development.

Methods

Serum was collected from patients with HFMD and healthy controls. EV71 and CA16 VP1 and VP3 genes were expressed in transfected Escherichia coli; the resultant VP1 and 3 proteins were used in a microarray assay for human serum EV71 and CA16 immunoglobulin (Ig) M and IgG. To validate the microarray assay, serum samples were tested for EV71 IgM using enzyme-linked immunosorbent assay (ELISA).

Results

Out of 50 patients with HFMD, EV71 IgM and CA16 IgM was detected in 80% and 44% of serum samples, respectively, using protein microarray, and EV71 IgM was detected in 78% of samples using ELISA. Protein microarray and ELISA showed 100% specificity for EV71-IgM detection.

Conclusion

The protein microarray assay developed in the present study shows potential as a sensitive technique for detecting EV71 IgM in serum samples from patients with HFMD.

Clinical and Etiological Characteristics of Atypical Hand-Foot-and-Mouth Disease in Children from Chongqing, China: A Retrospective Study

BACKGROUND

Hand-foot-and-mouth disease (HFMD) is a disease that had similar manifestations to chickenpox, impetigo, and measles, which is easy to misdiagnose and subsequently causes delayed therapy and subsequent epidemic. To date, no study has been conducted to report the clinical and epidemiological characteristics of atypical HFMD.

METHODS

64 children with atypical HFMD out of 887 HFMD children were recruited, stool was collected, and viral VP1 was detected.

RESULTS

The atypical HFMD accounted for 7.2% of total HFMD in the same period (64/887) and there were two peaks in its prevalence in nonepidemic seasons. Ten children (15.6%) had manifestations of neurologic involvement, of whom 4 (6.3%) were diagnosed with severe HFMD and 1 with critically severe HFMD, but all recovered smoothly. Onychomadesis and desquamation were found in 14 patients (21.9%) and 15 patients (23.4%), respectively. The most common pathogen was coxsackievirus A6 (CV-A6) which accounted for 67.2%, followed by nontypable enterovirus (26.6%), enterovirus 71 (EV-A71) (4.7%), and coxsackievirus A16 (A16) (1.5%).

CONCLUSIONS

Atypical HFMD has seasonal prevalence. The manifestations of neurologic involvement in atypical HFMD are mild and usually have a good prognosis. CV-A6 is a major pathogen causing atypical HFMD, but not a major pathogen in Chongqing, China.

Epidemiologic and etiologic characteristics of hand, foot, and mouth disease in Chongqing, China between 2010 and 2013

Hand, foot, and mouth disease (HFMD) has become very common in children, with widespread occurrence across China. The aim of this study was to investigate the epidemiologic and etiologic characteristics of HFMD, including etiologic variations in Chongqing, China. An epidemiologic investigation was based on 3,472 patients who presented with HFMD manifestations and were admitted at the Children's Hospital of Chongqing Medical University between 2010 and 2013. Fecal specimens from 830 patients were analyzed by nested RT-PCR to identify the enterovirus pathogens, and the molecular characterization of HFMD was illustrated by phylogenetic tree analysis. The results of this study indicate that the peak of the HFMD epidemic in Chongqing between 2010 and 2013 occurred between April and July each year. The median age of onset was 2.24 years old, and children under the age of five accounted for 96.4% of all the HFMD cases; the male-to-female ratio was 1.89:1. Enterovirus 71 accounted for a major proportion of the isolated strains every year, including the majority (74%) of severe cases. However, the proportion of Coxsackie A (CV-A) 6 infections increased from 2.11% in 2010 to 16.36% in 2013, while the proportion of CV-A16 infections decreased from 31.23% in 2010 to 4.67% in 2013. Molecular epidemiologic study showed that all enterovirus 71 strains belonged to subgenotype C4a, whereas all CV-A16 strains belonged to genotype B1, including subgenotype B1a and subgenotype B1b.

Characterization of VP1 gene of coxsackievirus A16 prevalent among hand foot mouth disease suffered children in Taizhou, P. R. China, between 2010 and 2013

A total of 453 strains of Coxsackievirus A16 (CV-A16) were screened out of 1,509 hand-foot-mouth disease (HFMD) samples collected in Taizhou during the period from 2010 to 2013. And between first quarter of 2011 and first quarter of 2013, an outbreak of CV-A16 was found among the HFMD sufferers in Taizhou. Phylogenic analysis of VP1 sequences indicated a major CV-A16 sub-group in Taizhou, whose change pattern of effective population sizes was found to be similar to the pattern of the actual percentage changes of CV-A16 during the outbreak over the same period. More importantly, the sub-group all displayed a Leu (L) to Met (M) mutation at site-23 of capsid VP1 which might be correlated with the outbreak of CV-A16 in Taizhou.

Is a multivalent hand, foot, and mouth disease vaccine feasible?

Enterovirus A infections are the primary cause of hand, foot and mouth disease (HFMD) in infants and young children. Although enterovirus 71 (EV-A71) and coxsackievirus A16 (CV-A16) are the predominant causes of HFMD epidemics worldwide, EV-A71 has emerged as a major neurovirulent virus responsible for severe neurological complications and fatal outcomes. HFMD is a serious health threat and economic burden across the Asia-Pacific region. Inactivated EV-A71 vaccines have elicited protection against EV-A71 but not against CV-A16 infections in large efficacy trials. The current development of a bivalent inactivated EV-A71/CV-A16 vaccine is the next step toward that of multivalent HFMD vaccines. These vaccines should ultimately include other prevalent pathogenic coxsackieviruses A (CV-A6 and CV-A10), coxsackieviruses B (B3 and B5) and echovirus 30 that often co-circulate during HFMD epidemics and can cause severe HFMD, aseptic meningitis and acute viral myocarditis. The prospect and challenges for the development of such multivalent vaccines are discussed.

Update of enterovirus 71 infection: epidemiology, pathogenesis and vaccine

Enterovirus 71 (EV71) is a neurotropic human pathogen that is the causative agent of hand foot and mouth disease (HFMD), herpangina and brain stem encephalitis. Recurrent EV71 epidemics of various scales have occurred in the Asia-Pacific region. Several specific cell surface molecules serve as the receptors for EV71. Identification of the receptors is an important step to understand EV71 disease. Cytokines, lymphocytes and monocytes contribute significantly to EV71 pathogenesis. The interaction of EV71 and receptors may be associated with the cytokines immunopathogenesis. Some animal models have been established and aim to explore the pathogenesis of EV71 infections. EV71 antibodies can neutralize or enhance infection at subneutralizing levels. These results are important for EV71 vaccine and therapeutics design. Several clinical trials of human inactivated EV71 vaccine have recently been completed. The purpose of this review is to summarize recent discoveries about the epidemiology and pathogenesis of EV71 and provide insights into human vaccine development.

Prevalence of enteroviruses in children with and without hand, foot, and mouth disease in China

Background

To determine the prevalence of human enteroviruses (HEVs) among healthy children, their parents, and children with hand, foot, and mouth disease (HFMD).

Methods

We conducted a case–control study that included throat samples from 579 children with HFMD and from 254 healthy controls. Throat samples from 49 households (98 parents and 53 healthy children) were also analyzed. Phylogenetic analysis was carried out to study genetic relationships of EV71 strains.

Results

The HEV positive rate in HFMD patients was significantly higher than that in healthy controls (76.0% vs. 23.2%, P < 0.001). The EV71 (43.7% vs. 15.0%, P < 0.001), CVA16 (18.0% vs. 2.8%, P < 0.001), and CVA10 (5.7% vs. 0.8%, P = 0.001) serotypes were significantly overrepresented in HFMD patients in comparison to healthy children. Other HEV serotypes were detected with comparable frequency in cases and controls. The HEV positive rate in severe HFMD patients was significantly higher than that in mild group (82.1% vs. 73.8%, P = 0.04). The EV71 (55.0% vs. 39.7%, P = 0.001) and CVA16 (11. 9% vs. 20.0%, P = 0.024) positive rate differed significantly between severe and mild HFMD patients. Other HEV serotypes were detected with comparable frequency between severe and mild HFMD patients. Among 49 households, 22 households (44.9%) had at least 1 family member positive for HEV. Children had significantly higher HEV positive rate than adult (28.3% vs. 14.3%, P = 0.037). The HEV positive rate was similar between mothers and fathers (12.24% vs. 16.32%, P = 0.56). The VP1 sequences of EV71 from HFMD patients and healthy children were nearly identical and all were clustered in the same clade, C4a.

Conclusions

Our study demonstrated the co-circulation of multiple HEV serotypes in children with and without HFMD during epidemic. Our study deserves the attention on HFMD control.