Epidemiological and genetic characteristics of EV71 in hand, foot, and mouth disease in Guangxi, southern China, from 2010 to 2015

Emerging concerns of blood-brain barrier dysfunction caused by neurotropic enteroviral infections

Enteroviruses (EVs), comprise a genus in the Picornaviridae family, which have been shown to be neurotropic and can cause various neurological disorders or long-term neurological condition, placing a huge burden on society and families. The blood-brain barrier (BBB) is a protective barrier that prevents dangerous substances from entering the central nervous system (CNS). Recently, numerous EVs have been demonstrated to have the ability to disrupt BBB, and further lead to severe neurological damage. However, the precise mechanisms of BBB disruption associated with these EVs remain largely unknown. In this Review, we focus on the molecular mechanisms of BBB dysfunction caused by EVs, emphasizing the invasiveness of enterovirus A71 (EVA71), which will provide a research direction for further treatment and prevention of CNS disorders.

Phylogeographic dynamics and molecular characteristics of Enterovirus 71 in China

Enterovirus 71 (EV71) and coxsackievirus (CV-A16) are the major etiological agents of hand, foot and mouth disease (HFMD). This report reviewed the full-length genomic sequences of EV71 identified in different provinces of China between 1998 and 2019 (a total of 312) in addition to eight worldwide reference genomes to address the genomic evolution and genetic events. The main prevalent EV71 strians in China are C4 genotypes, co-circulating with a few A, B5, C1, and C2 subgenotypes. A new emerging subgenotype in China was identified and classified as B6 genotype. Phylogeographic analysis revealed multiple branches, where a Jiangsu strain 2006-52-9 (GenBank ID: KP266579.1) was linked to different subgenotypes through multiple long mutant branches, including the CV-A16 viruses through the A genotype. Furthermore, identification of 28 natural recombination events suggests that the emergence of new genotypes are associated with intratypic recombination involving EV71 strains and intertypic recombination between EV71 and CV-A16 strains. Compared with the structural proteins, the non-structural proteins of EV71 seem to be highly variable with the highest variable regions of peptidase C3 (3C protein), P2A, and the N-terminus of RNA-dependent RNA polymerase. This study updates the phylogenetic and phylogeographic information of EV71 and provides clues to the emergence of new genotypes of EV71 based on genetics.

Factors related to the mortality risk of severe hand, foot, and mouth diseases (HFMD): a 5-year hospital-based survey in Guangxi, Southern China

BACKGROUND

To understand the factors influencing clinical outcomes of severe hand, foot, and mouth diseases (HFMD), and to provide scientific evidence for reducing the mortality risk of severe HFMD.

METHODS

From 2014 to 2018, children diagnosed with severe HFMD cases in Guangxi, China, were enrolled in this hospital-based study. The epidemiological data obtained through face-to-face interviews with the parents and guardians. Univariate and multivariate logistics regression models were used to analyze the factors influencing the clinical outcomes of severe HFMD. The impact of the EV-A71 vaccination on inpatient mortality was analyzed by a comparison approach.

RESULTS

A total of 1565 severe HFMD cases were enrolled in this survey, including 1474 (94.19%) survival cases and 91 (5.81%) death cases. The multivariate logistic analysis demonstrated that HFMD history of playmates in the last three months, first visit to the village hospital, time from the first visit to admission less than two days, no correct diagnosis for HFMD at the first visit, and having no rash symptoms were the independent risk factors for severe HFMD cases (all p < 0.05). While EV-A71 vaccination was a protective factor (p < 0.05). The EV-A71 vaccination group versus the non-vaccination group showed 2.23% of death in the vaccination group and 7.24% of death in the non-vaccination group. The EV-A71 vaccination protected 70.80% of the death of severe HFMD cases, with an effective index of 4.79.

CONCLUSIONS

The mortality risk of severe HFMD in Guangxi was related to playmates had HFMD history in last 3 months, hospital grade, EV-A71 vaccination, patients visit hospital previously, and rash symptom. EV-A71 vaccination can significantly reduce mortality among severe HFMD. The findings are of great significance for the effective prevention and control of HFMD in Guangxi, southern China.

Long-term effects of weather condition and air pollution on acute hemorrhagic conjunctivitis in China: A nationalwide surveillance study in China

BACKGROUND

Global climate change could have potential impact on enterovirus (EV)-induced infectious diseases. However, the environmental factors promoting acute hemorrhagic conjunctivitis (AHC) circulation remain inconclusive. This study aimed to quantify the relationship between the environment and AHC.

METHODS

We retrieved the monthly counts and incidence of AHC, meteorological variables and air quality in mainland China between 2013 and 2018. Exposure risks were evaluated by multivariate distributed lag nonlinear models.

RESULTS

A total of 219,599 AHC cases were reported in 31 provinces of China, predominantly in southern and central China, seasonally increased in summer. AHC incidence increased by 7% between 2013 and 2018, from 2.6873 to 2.7570 per 100,000 people. A moderate positive correlation was seen between AHC and monthly mean temperature, relative humidity (RH) and precipitation. Each unit increment was associated with a relative risk for AHC of 1.058 at 17°-32 °C at lag 0 months, 1.017 at 65-71% RH at lag 1.4 months, and 1.039 at 400-569 mm at lag 2.4 months. By contrast, a negative correlation was seen between monthly ambient NO₂ and AHC.

CONCLUSION

Long-term exposure to higher mean temperature, RH and precipitation were associated with an increased risk of AHC. The general public, especially susceptible populations, should pay close attention to weather changes and take protective measures in advance to any AHC outbreak as the above situations occur.

First seroepidemiological investigation of human enterovirus 71 in Iran

Background and Objectives:

Human Enterovirus 71 (EV-A71) is the causative agent for many dermal to neurological diseases especially polio-like paralysis outbreaks around the world. This study, the first of this kind in Iran, aimed to find neutralizing antibodies against EV-A71 in serum of healthy individuals in different age groups based on neutralization test (NT).

Materials and Methods:

In this cross-sectional study, 547 serum samples were collected from healthy individuals who were referring for routine checkup tests (aged from under 6 months to over 31 years old) to Imam-Khomeini Hospital in Tehran during January-December 2015. Serum samples were examined by NT in cell culture to detect neutralizing antibodies against EV-A71. In the next step, some of the positive samples were subjected to complete titration to determine the exact titer of anti-EV-A71 antibodies.

Results:

Of 547 samples, 310 (56.7%) were positive for EV-A71 neutralizing antibody. The presence of the antibody increased with age (p<0.001), and there was a significant statistical relationship between sex and the presence of antibody (p=0.009).

Conclusion:

Our results demonstrated an apparent but limited circulation of EV-A71 in our society. After the worldwide eradication of poliovirus, EV-A71 which can cause polio-likes syndrome, might be the new challenge for our health care system as regard more in depth research is however needed.

Viral determinants that drive Enterovirus-A71 fitness and virulence

Hand, Foot and Mouth Disease (HFMD) is usually a self-limiting, mild childhood disease that is caused mainly by Coxsackie virus A16 (CVA16) and Enterovirus A71 (EV-A71), both members of the Picornaviridae family. However, recurring HFMD outbreaks and epidemics due to EV-A71 infection in the Western Pacific region, and the propensity of EV-A71 strains to cause severe neurological complications have made this neurotropic virus a serious public health concern in afflicted countries. High mutation rate leading to viral quasispecies combined with frequent intra- and inter-typic recombination events amongst co-circulating EV-A71 strains have contributed to the great diversity and fast evolution of EV-A71 genomes, making impossible any accurate prediction of the next epidemic strain. Comparative genome sequence analyses and mutagenesis approaches have led to the identification of a number of viral determinants involved in EV-A71 fitness and virulence. These viral determinants include amino acid residues located in the structural proteins of the virus, affecting attachment to the host cell surface, receptor binding, and uncoating events. Critical residues in non-structural proteins have also been identified, including 2C, 3A, 3C proteases and the RNA-dependent RNA polymerase. Finally, mutations altering key secondary structures in the 5’ untranslated region were also found to influence EV-A71 fitness and virulence. While our current understanding of EV-A71 pathogenesis remains fragmented, these studies may help in the rational design of effective treatments and broadly protective vaccine candidates.

MicroRNAs miR-18a and miR-452 regulate the replication of enterovirus 71 by targeting the gene encoding VP3

MicroRNAs (miRNAs) are crucial in the process of host-pathogen interaction. In this study, we established a screening system for miRNAs of target genes to detect the effect of miRNAs on Enterovirus 71 (EV71) replication in rhabdomyosarcoma (RD) cells. A 3'-untranslated region (UTR) dual-luciferase assay was performed to confirm putative miRNA targets in EV71 genome. Firstly, 13 fragments of EV71 genome were inserted into the vector pMIR, and luciferase activities were analyzed to identify the putative miRNAs of target genes. The expression of the reporter protein was significantly downregulated in cells transfected with the vector containing gene VP3. Then we screened for miRNAs that might target to VP3 through online analysis software. In addition, Western blot, real-time PCR, virus titration, and morphological changes were considered to examine the effects of miRNAs on virus replication. The results suggested that miR-18a and miR-452 repress the reproduction of EV71 virus by binding to VP3. Moreover, EV71 infection also affected the expression of endogenous miR-18a and miR-452. In addition, no significant cytotoxic effects were observed. The results from this study suggest that the intracellular miRNAs may play vital roles in the host-virus interaction.

The changes in the epidemiology of hand, foot, and mouth disease after the introduction of the EV-A71 vaccine

Three inactive monovalent EV-A71 vaccines have been launched in China since 2016, which may change the HFMD pathogen spectrum and epidemiological trend. Using notifications from the national surveillance system, we analyzed the epidemiological character profiles and the possible pathogen replacement. The proportion of HFMD cases aged 0-12 months decreased from 23.0% to 15.3% between 2013-2015 and 2017-2019 (p < 0.01). EV-A71 among laboratory-confirmed severe cases in 2013-2015 (62.8%) transformed to other EVs (67.2%) in 2017-2019. The age distribution of EV-A71 infection shifted to the older. The cumulative coverage of the EV-A71 vaccine for children aged six months to five years in Guangxi has increased, while in severe cases, the positive rate declined. After gradually expanded vaccination, EV-A71 associated incidence rate, case-severity rate has decreased, and other serotypes are becoming dominant. Thus, bivalent even polyvalent vaccines are urgently needed to control HFMD.

A 10-Day-Old Murine Model of Coxsackievirus A6 Infection for the Evaluation of Vaccines and Antiviral Drugs

Coxsackievirus A6 (CVA6) is recognized as a major enterovirus type that can cause severe hand, foot, and mouth disease and spread widely among children. Vaccines and antiviral drugs may be developed more effectively based on a stable and easy-to-operate CVA6 mouse infection model. In this study, a wild CVA6-W strain was sub-cultured in newborn mice of different ages (in days), for adaptation. Therefore, a CVA6-A mouse-adapted strain capable of stably infecting the mice was generated, and a fatal model was built. As the result indicated, CVA6-A could infect the 10-day-old mice to generate higher levels of IFN-γ, IL-6, and IL-10. The mice infected with CVA6-A were treated with IFN-α1b at a higher dose, with complete protection. Based on this strain, an animal model with active immunization was built to evaluate antiviral protection by active immunization. The three-day-old mice were pre-immunized with inactivated CVA6 thereby generating IgM and IgG antibodies within 7 days that enabled complete protection of the pre-immunized mice following the CVA6 virus challenge. There were eight mutations in the genome of CVA6-A than in that of CVA6-W, possibly attributed to the virulence of CVA6 in mice. Briefly, the CVA6 infection model of the 10-day-old mice built herein, may serve as an applicable preclinical evaluation model for CVA6 antiviral drugs and vaccine study.

Molecular Epidemiological Study of Hand, Foot, and Mouth Disease in a Kindergarten-Based Setting in Bangkok, Thailand

Hand, foot, and mouth disease (HFMD) is a contagious childhood illness and annually affects millions of children aged less than 5 years across the Asia–Pacific region. HFMD transmission mainly occurs through direct contact (person-to-person) and indirect contact with contaminated surfaces and objects. Therefore, public health measures to reduce the spread of HFMD in kindergartens and daycare centers are essential. Based on the guidelines by the Department of Disease Control, a school closure policy for HFMD outbreaks wherein every school in Thailand must close when several HFMD classrooms (more than two cases in each classroom) are encountered within a week, was implemented, although without strong supporting evidence. We therefore conducted a prospective cohort study of children attending five kindergartens during 2019 and 2020. We used molecular genetic techniques to investigate the characteristics of the spreading patterns of HFMD in a school-based setting in Bangkok, Thailand. These analyses identified 22 index cases of HFMD (symptomatic infections) and 25 cases of enterovirus-positive asymptomatic contacts (24 students and one teacher). Enterovirus (EV) A71 was the most common enterovirus detected, and most of the infected persons (8/12) developed symptoms. Other enteroviruses included coxsackieviruses (CVs) A4, CV-A6, CV-A9, and CV-A10 as well as echovirus. The pattern of the spread of HFMD showed that 45% of the subsequent enteroviruses detected in each outbreak possessed the same serotype as the first index case. Moreover, we found a phylogenetic relationship among enteroviruses detected among contact and index cases in the same kindergarten. These findings confirm the benefit of molecular genetic assays to acquire accurate data to support school closure policies designed to control HFMD infections.

Enterovirus-A71 exploits peripherin and Rac1 to invade the central nervous system

Enterovirus-A71 (EV-A71) has been associated with severe neurological forms of hand, foot, and mouth disease (HFMD). EV-A71 infects motor neurons at neuromuscular junctions (NMJs) to invade the central nervous system (CNS). Here, we investigate the role of peripherin (PRPH) during EV-A71 infection, a type III intermediate neurofilament involved in neurodegenerative conditions. In mice infected with EV-A71, PRPH co-localizes with viral particles in the muscles at NMJs and in the spinal cord. In motor neuron-like and neuroblastoma cell lines, surface-expressed PRPH facilitates viral entry, while intracellular PRPH influences viral genome replication through interactions with structural and non-structural viral components. Importantly, PRPH does not play a role during infection with coxsackievirus A16, another causative agent of HFMD rarely associated with neurological complications, suggesting that EV-A71 ability to exploit PRPH represents a unique attribute for successful CNS invasion. Finally, we show that EV-A71 also exploits some of the many PRPH-interacting partners. Of these, small GTP-binding protein Rac1 represents a potential druggable host target to limit neuroinvasion of EV-A71.

Two cases of hand, foot and mouth disease caused by enterovirus A71 after vaccination

BACKGROUND

Enterovirus A71 (EVA71) is one of the main pathogens causing hand, foot and mouth disease (HFMD). In China, the proportion of cases of HFMD caused by EVA71 is known to be significantly lower following EVA71 vaccination; however, infection with EVA71 can still occur after vaccination.

METHODS

The complete genomic sequences of EVA71-KM18A and KM18B (from two rare cases of EVA71 infection following vaccination) were obtained. Phylogenetic analysis, nucleotide mutation analysis, recombinant analysis and comparative analysis of amino acid mutations were performed.

RESULTS

Phylogenetic analysis determined that the EVA71 strains belonged to the C4a subgenotype. The KM18A and KM18B strains were highly similar to the vaccine strains. For the KM18B strain, there were some obvious homologous recombination signals in the 5'non-coding region, region 2A, region 2C and region 3D. Amino acid mutations were observed in the SP55 (position 729) and 71-6 (position 500) conformational neutralizing epitopes of the KM18A and KM18B strains.

CONCLUSIONS

These amino acid mutations may affect the SP55 and 71-6 conformational neutralizing epitopes and change their spatial conformation, thereby weakening vaccine effectiveness.

Leading Enterovirus Genotypes Causing Hand, Foot, and Mouth Disease in Guangzhou, China: Relationship with Climate and Vaccination against EV71

(1) Background: Assignment of pathogens to the correct genus, species, and type is vital for controlling infectious epidemics. However, the role of different enteroviruses during hand, foot, and mouth disease (HFMD) epidemics and the major contributing factors remain unknown. (2) Methods: HFMD cases from 2016 to 2018 in Guangzhou, China were collected. The relationship between HFMD cases and genotype frequency, as well as the association between genotype frequency and climate factors, were studied using general linear models. We transformed the genotype frequency to the isometric log-ratio (ILR) components included in the model. Additionally, vaccination rates were adjusted in the climate-driven models. (3) Results: We observed seasonal trends in HFMD cases, genotype frequency, and climate factors. The model regressing case numbers on genotype frequency revealed negative associations with both the ILRs of CAV16 (RR = 0.725, p < 0.001) and EV71 (RR = 0.421, p < 0.001). The model regressing genotype frequency on driven factors showed that the trends for EV71 proportions were inversely related to vaccination rate (%, β = -0.152, p = 0.098) and temperature (°C, β = -0.065, p = 0.004). Additionally, the trends for CVA16 proportions were inversely related to vaccination rate (%, β = -0.461, p = 0.004) and temperature (°C, β = -0.068, p = 0.031). The overall trends for genotype frequency showed that EV71 decreased significantly, while the trends for CVA16 increased annually. (4) Conclusions: Our findings suggest a potential pathway for climate factors, genotype frequency, and HFMD cases. Our study is practical and useful for targeted prevention and control, and provides environmental-based evidence.

The Role of APOBECs in Viral Replication

Apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC) proteins are a diverse and evolutionarily conserved family of cytidine deaminases that provide a variety of functions from tissue-specific gene expression and immunoglobulin diversity to control of viruses and retrotransposons. APOBEC family expansion has been documented among mammalian species, suggesting a powerful selection for their activity. Enzymes with a duplicated zinc-binding domain often have catalytically active and inactive domains, yet both have antiviral function. Although APOBEC antiviral function was discovered through hypermutation of HIV-1 genomes lacking an active Vif protein, much evidence indicates that APOBECs also inhibit virus replication through mechanisms other than mutagenesis. Multiple steps of the viral replication cycle may be affected, although nucleic acid replication is a primary target. Packaging of APOBECs into virions was first noted with HIV-1, yet is not a prerequisite for viral inhibition. APOBEC antagonism may occur in viral producer and recipient cells. Signatures of APOBEC activity include G-to-A and C-to-T mutations in a particular sequence context. The importance of APOBEC activity for viral inhibition is reflected in the identification of numerous viral factors, including HIV-1 Vif, which are dedicated to antagonism of these deaminases. Such viral antagonists often are only partially successful, leading to APOBEC selection for viral variants that enhance replication or avoid immune elimination.

Beclin1 Binds to Enterovirus 71 3D Protein to Promote the Virus Replication

Enterovirus 71 (EV71) is the main pathogen causing hand-foot-mouth disease (HFMD) in infants and children, which can also lead to severe neurological diseases and even death. Therefore, understanding the replication mechanism of EV71 is of great significance for the prevention and control of EV71-induced diseases. Beclin1 (BECN1, a mammalian homologue of ATG6 in yeast) is an important core protein for the initiation and the normal process of autophagy in cells. In addition to its involvement in autophagy, Beclin1 has also been reported to play an important role in cancer and innate immune signaling pathways. However, the role of Beclin1 in EV71 replication remains elusive. Here, we primarily found that Beclin1 facilitates EV71 replication in human rhabdomyosarcoma (RD) cells and the autophagy was actually induced, but Beclin1 was not significantly affected at either mRNA level or protein level during early EV71 infection. Further studies discovered that Beclin1 could interacts with EV71 non-structural protein 3D mainly through its evolutionary conserved domain (ECD) and coiled-coiled domain (CCD), thus promoting the replication of EV71 in human rhabdomyosarcoma (RD) cells and human astroglioma (U251) cells. Collectively, we reveal a novel regulatory mechanism associated with Beclin1 to promote EV71 replication, thus providing a potential therapeutic target for the prevention and control of EV71-associated diseases.

Enterovirus 71 Infection Shapes Host T Cell Receptor Repertoire and Presumably Expands VP1-Specific TCRβ CDR3 Cluster

Enterovirus 71 (EV71) has become an important public health problem in the Asia-Pacific region in the past decades. EV71 infection might cause neurological and psychiatric complications and even death. Although an EV71 vaccine has been currently approved, there is no effective therapy for treating EV71-infected patients. Virus infections have been reported to shape host T cell receptor (TCR) repertoire. Therefore, understanding of host TCR repertoire in EV71 infection could better the knowledge in viral pathogenesis and further benefit the anti-viral therapy development. In this study, we used a mouse-adapted EV71 (mEV71) model to observe changes of host TCR repertoire in an EV71-infected central nervous system. Neonate mice were infected with mEV71 and mouse brainstem TCRβ repertoires were explored. Here, we reported that mEV71 infection impacted host brainstem TCRβ repertoire, where mEV71 infection skewed TCRβ diversity, changed VJ combination usages, and further expanded specific TCRβ CDR3 clones. Using bioinformatics analysis and ligand-binding prediction, we speculated the expanded TCRβ CDR3 clone harboring CASSLGANSDYTF sequence was capable of binding cleaved EV71 VP1 peptides in concert with major histocompatibility complex (MHC) molecules. We observed that mEV71 infection shaped host TCRβ repertoire and presumably expanded VP1-specific TCRβ CDR3 in mEV71-infected mouse brainstem that integrated EV71 pathogenesis in central nervous system.

Spatial-temporal variation and risk factor analysis of hand, foot, and mouth disease in children under 5 years old in Guangxi, China

BACKGROUND

Hand, foot and mouth disease (HFMD) incidence is a critical challenge to disease control and prevention in parts of China, particularly Guangxi. However, the association between socioeconomic factors and meteorological factors on HFMD is still unclear.

METHODS

This study applied global and local Moran's I to examine the spatial pattern of HFMD and series analysis to explore the temporal pattern. The effects of meteorological factors and socioeconomic factors on HFMD incidence in Guangxi, China were analyzed using GeoDetector Model.

RESULTS

This study collected 45,522 cases from 87 counties in Guangxi during 2015, among which 43,711 cases were children aged 0-4 years. Temporally, there were two HFMD risk peaks in 2015. One peak was in September with 7890 cases. The other appeared in May with 4687 cases of HFMD. A high-risk cluster was located in the valley areas. The tertiary industry, precipitation and second industry had more influence than other risk factors on HFMD incidence with explanatory powers of 0.24, 0.23 and 0.21, respectively. The interactive effect of any two risk factors would enhance the risk of HFMD.

CONCLUSIONS

This study suggests that precipitation and tertiary industry factors might have stronger effects on the HFMD incidence in Guangxi, China, compared with other factors. High-risk of HFMD was identified in the valley areas characterized by high temperature and humidity. Local government should pay more attention and strengthen public health services level in this area.

Spatial-temporal heterogeneity of hand, foot and mouth disease and impact of meteorological factors in arid/ semi-arid regions: a case study in Ningxia, China

Background

The incidence of hand, foot and mouth disease (HFMD) varies over space and time and this variability is related to climate and social-economic factors. Majority of studies on HFMD were carried out in humid regions while few have focused on the disease in arid/semi-arid regions, more research in such climates would potentially make the mechanism of HFMD transmission clearer under different climate conditions.

Methods

In this paper, we explore spatial-temporal distribution of HFMD in Ningxia province, which has an arid/semi-arid climate in northwest China. We first employed a Bayesian space-time hierarchy model (BSTHM) to assess the spatial-temporal heterogeneity of the HFMD cases and its relationship with meteorological factors in Ningxia from 2009 to 2013, then used a novel spatial statistical software package GeoDetector to test the spatial-temporal heterogeneity of HFMD risk.

Results

The results showed that the spatial relative risks in northern part of Ningxia were higher than those in the south. The highest temporal risk of HFMD incidence was in fall season, with a secondary peak in spring. Meteorological factors, such as average temperature, relative humidity, and wind speed played significant roles in the spatial-temporal distribution of HFMD risk.

Conclusions

The study provide valuable information on HFMD distribution in arid/semi-arid areas in northwest China and facilitate understanding of the concentration of HFMD.

[Association of interleukin-10 gene polymorphism with enterovirus 71 infection in children]

OBJECTIVE

To study the association of interleukin-10 (IL-10) -1082A/G, -819C/T, and -592C/A polymorphisms with IL-10 level and the severity of enterovirus 71 (EV71) infection in children.

METHODS

A total of 137 children with hand-foot-mouth disease due to EV71 infection were enrolled as EV71 infection group, which was further divided into mild group with 91 children and severe group with 46 children, and 122 healthy children who underwent physical examination were enrolled as healthy control group. Related clinical data were collected. ELISA was used to measure the serum level of IL-10, and polymerase chain reaction-restriction fragment length polymorphism was used to analyze IL-10 -1082A/G, -819C/T and -592C/A polymorphisms.

RESULTS

Compared with the healthy control group, the children with EV71 infection had significantly higher frequency of -1082 AA genotype and A allele (P<0.05). Among the children with EV71 infection, the severe group had significantly higher frequency of -1082 AA genotype and A allele than the mild group (P<0.05), while there was no significant difference in the distribution of IL-10 -819C/T and IL-10 -592C/A polymorphisms between the two groups (P>0.05). The severe group had a significantly higher serum level of IL-10 than the mild group and the healthy control group. IL-10 -1082 AA genotype, -819 TT genotype, and -592 AA genotype were associated with the low expression of IL-10 (P<0.05). As for haplotype, the EV71 infection group had a significantly lower frequency of GCC haplotype than the healthy control group (P<0.05). In the severe group, the children with ATA haplotype had a significantly lower IL-10 level than those with other haplotypes, and the children with GCC haplotype had a significantly higher IL-10 level than those with other haplotypes (P<0.05). There was no significant difference in IL-10 level between children with different haplotypes in the mild group and the healthy control group (P>0.05).

CONCLUSIONS

IL-10 gene polymorphisms are associated with IL-10 expression and the severity of EV71 infection in children.

APOBEC3G is a restriction factor of EV71 and mediator of IMB-Z antiviral activity

Enterovirus 71 (EV71), a single-stranded positive-sense RNA virus, is the causative agent of hand, foot, and mouth disease (HFMD), for which no effective antiviral therapy is currently available. Apolipoprotein B messenger RNA-editing enzyme catalytic polypeptide-like 3G (APOBEC3G or A3G) is a cytidine deaminase that inhibits the replication of several viruses, such as human immunodeficiency virus-1, hepatitis B virus and hepatitis C virus. In our efforts toward understanding the antiviral spectrum and mechanism of A3G, we found that ectopic expression of A3G inhibited EV71 replication, whereas knockdown of endogenous A3G expression promoted EV71 replication. Moreover, inhibition of EV71 replication by IMB-Z, a N-phenylbenzamide derivative, is associated with increased levels of intracellular A3G, but reducing the level of A3G by RNA interference diminished the antiviral activity of IMB-Z. Mechanistically, we obtained evidence suggesting that the cytidine deaminase activity is not required for A3G inhibition of EV71 replication. Instead, we demonstrated that A3G can interact with viral 3D RNA-dependent RNA polymerase (RdRp) and viral RNA and be packaged into progeny virions to reduce its infectivity. Taken together, our results indicate that A3G is a cellular restriction factor of EV71 and mediator of the antiviral activity of IMB-Z. Pharmacological induction and/or stabilization of A3G is a potential therapeutic approach to treat diseases caused by EV71 infection, such as HFMD.

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.

Seroprevalence of antibodies to enterovirus 71 and coxsackievirus A16 among people of various age groups in a northeast province of Thailand

BACKGROUND

Hand, foot and mouth disease (HFMD) is endemic among population of young children in Thailand. The disease is mostly caused by enterovirus 71 (EV71) and coxsackievirus A16 (CA16).

METHODS

This study conducted serosurveillance for neutralizing (NT) antibodies to EV71 subgenotypes B5 and C4a, and to CA16 subgenotypes B1a and B1b, in 579 subjects of various ages using a microneutralization assay in human rhabdomyosarcoma (RD) cells. These test viruses were the major circulating subgenotypes associated with HFMD in Thailand during the study period.

RESULTS

We found that the levels of seropositivity against all 4 study viruses were lowest in the age group of 6-11 months, i.e., 5.5% had antibody to both EV71 subgenotypes, while 14.5% and 16.4% had antibody to CA16 subgenotypes B1a and B1b, respectively. The percentages of subjects with antibodies to these 4 viruses gradually increased with age, but were still less than 50% in children younger than 3 years. These laboratory data were consistent with the epidemiological data collected by the Ministry of Public Health which showed repeatedly that the highest number of HFMD cases was in children aged 1 year. Analyses of amino acid sequences of the test viruses showed 97% identity between the two subgenotypes of EV71, and 99% between the two subgenotypes of CA16. Nevertheless, the levels of seropositivity and antibody titer against the two subgenotypes of EV71 and of CA16 were not significantly different.

CONCLUSIONS

This study clearly demonstrated NT antibody activity across EV71-B5 and EV71-C4a subgenotypes, and also across CA16-B1a and CA16-B1b subgenotypes. Moreover, there were no significant differences by gender in the seropositive rates and antibody levels to any of the 4 virus subgenotypes.