Specific primer amplification of the VP1 region directed by 5' UTR sequence analysis: enterovirus testing and identification in clinical samples from hand-foot-and-mouth disease patients

Molecular epidemiology of enteroviruses associated with hand, foot, and mouth disease in South India from 2015 to 2017

Hand, foot, and mouth disease (HFMD) is a common childhood infection caused by human enteroviruses and is clinically characterised by fever with vesicular rash on the hands, feet, and mouth. While enterovirus A71 (EV-A71) and coxsackievirus A16 (CVA16) were the major etiological agents of HFMD in India earlier, the data on recently circulating enteroviruses associated with HFMD are sparse. Here, we describe the molecular epidemiology of enteroviruses associated with HFMD in South India from 2015 to 2017. We used archived enterovirus real-time reverse transcription (RT) PCR-positive vesicle swab and/or throat swab specimens from clinically suspected HFMD cases collected from four secondary-care hospitals in South India between July 2015 and December 2017. PCR amplification and sequencing were done based on the 5’VP1, 3’VP1, VP2, or 5´NCR regions to identify enterovirus types. Genetic diversity among enteroviruses was inferred by phylogenetic analysis. Of the 107 enterovirus RNA real-time RT-PCR-positive HFMD cases, 69 (64%) were typed as CVA6, 16 (15%) were CVA16, and one (1%) was CVA10, whereas in 21 (20%) cases, the virus was not typeable by any of the methods used in the study. The majority of HFMD cases (89, 83%) were in children less than five years old, while 11 (10.3%) were in adults. 5’VP1 yielded the maximum number of enteroviruses genotyped, and phylogenetic analysis showed that the CVA6 strains belonged to subclade D3, while the subclades of CVA16 and CVA10 were B1c and D, respectively. The predominant etiological agent of HFMD in South India during 2015-2017 was CVA6, followed by CVA16 and CVA10.

Evolutionary Relationships of Ljungan Virus Variants Circulating in Multi-Host Systems across Europe

The picornavirus named 'Ljungan virus' (LV, species Parechovirus B) has been detected in a dozen small mammal species from across Europe, but detailed information on its genetic diversity and host specificity is lacking. Here, we analyze the evolutionary relationships of LV variants circulating in free-living mammal populations by comparing the phylogenetics of the VP1 region (encoding the capsid protein and associated with LV serotype) and the 3D^pol region (encoding the RNA polymerase) from 24 LV RNA-positive animals and a fragment of the 5' untranslated region (UTR) sequence (used for defining strains) in sympatric small mammals. We define three new VP1 genotypes: two in bank voles (Myodes glareolus) (genotype 8 from Finland, Sweden, France, and Italy, and genotype 9 from France and Italy) and one in field voles (Microtus arvalis) (genotype 7 from Finland). There are several other indications that LV variants are host-specific, at least in parts of their range. Our results suggest that LV evolution is rapid, ongoing and affected by genetic drift, purifying selection, spillover and host evolutionary history. Although recent studies suggest that LV does not have zoonotic potential, its widespread geographical and host distribution in natural populations of well-characterized small mammals could make it useful as a model for studying RNA virus evolution and transmission.

Epidemiological and molecular characteristics of circulating CVA16, CVA6 strains and genotype distribution in hand, foot and mouth disease cases in 2017 to 2018 from Western India

Hand, Foot, and Mouth disease (HFMD) is a mild exanthematous and febrile disease occurs in children aged ≤10 years old. The present study highlights clinical, epidemiological characteristics, distribution of enterovirus (EV) types, and sub genotypes in HFMD cases reported during 2017 to 2018 in Western India. A total of 93 clinical samples collected from 68 HFMD cases were included. The presence of EV-RNA was determined by 5'UTR based nested reverse transcription polymerase chain reaction followed by molecular typing, sub genotyping by VP1/2A junction or VP1, full VP1 gene amplification, and phylogenetic analysis. The study reports 80.64% (75/93) EV positivity and 94.66% (71/75) typing rate, with a predominant circulation of CVA16 and CVA6 strains. Sequence analysis revealed the presence of coxsackievirus (CV)A16 (57.7%), CVA6 (40.8%), and Echo1 (1.4%) strains. EV infections were predominantly observed in children aged 1 to 3 years old (43.9%). Although cases were reported throughout the year, peaked in July (15.8%) and August (24.6%) months and persisted till September (19.3%). All the CVA16 and CVA6 positive strains were genotyped using full VP1 gene amplification. All CVA16 Indian strains (n = 41) were clustered with rarely reported B1c sub genotype and CVA6 strains (n = 29) with E2 sub-lineage. The study highlights the genetic characteristics of circulating CVA16, CVA6, and Echo1 strains in HFMD cases from Western India. The emergence of CVA16 B1c genotype and sub-lineage E2 of CVA6 strains and their constant circulation further demands systemic surveillance studies on HFMD from different parts of India to facilitate the rapid diagnosis of CVA16 and CVA6 strains using the molecular and serological based approach and for intervention strategies.

Sporadic hand, foot, and mouth disease cases associated with non-C4 enterovirus 71 strains in Xiamen, China, from 2009 to 2018

Enterovirus 71 (EV71) has caused large hand, foot, and mouth disease (HFMD) epidemics among young children, and EV71 infection is the leading cause of severe HFMD cases and deaths. In mainland China, the prevalence and risk factors of non-C4 EV71 strains are still unclear. In this study, we monitored non-C4 strains over a 10-year HFMD epidemiological surveillance period in Xiamen. The 5’UTR and VP1 coding region of EV71 strains were amplified by RT-nested PCR and sequenced. Thirty-two non-C4 EV71 strains were identified during 2009-2018. This study provides important information about the prevalence of EV71 in China that will be applicable for development of vaccines and diagnostic reagents as well as establishment of policies for HFMD prevention and control.

Epidemical and etiological study on hand, foot and mouth disease following EV-A71 vaccination in Xiangyang, China

Coxsackievirus A6 (CV-A6) and Coxsackievirus A10 (CV-A10) have been emerging as the prevailing serotypes and overtaking Enterovirus A71 (EV-A71) and Coxsackievirus A16 (CV-A16) in most areas as main pathogens of hand, foot and mouth disease (HFMD) in China since 2013. To investigate whole etiological spectrum following EV-A71 vaccination of approximate 40,000 infants and young children in Xiangyang, enteroviruses were serotyped in 4415 HFMD cases from October 2016 to December 2017 using Real Time and conventional PCR and cell cultures. Of the typeable 3201 specimen, CV-A6 was the predominant serotype followed by CV-A16, CV-A10, CV-A5, CV-A2 and EV-A71 with proportions of 59.54%, 15.31%, 11.56%, 4.56%, 3.78% and 3.03%, respectively. Other 12 minor serotypes were also detected. The results demonstrated that six major serotypes of enteroviruses were co-circulating, including newly emerged CV-A2 and CV-A5. A dramatic decrease of EV-A71 cases was observed, whereas the total cases remained high. Multivalent vaccines against major serotypes are urgently needed for control of HFMD.

Non-polio enterovirus infections in children with central nervous system disorders in Shanghai, 2016-2018: Serotypes and clinical characteristics

BACKGROUND

Non-polio enrerovirus causes a wide spectrum of neurologic syndromes. The epidemiological and clinical profiles of non-polio enrerovirus-associated central nervous system infections vary by regions and over year.

OBJECTIVES

This study aimed to understand the prevalence, serotypes and clinical characteristics of enterovirus-associated aseptic meningitis, encephalitis and meningo-encephalitis in children in Shanghai during 2016-2018.

METHODS

We collected the clinical data and the cerebrospinal fluid specimens from the pediatric patients with aseptic meningitis, encephalitis and meningo-encephalitis during 2016-2018. The nested RT-PCR and sequencing were performed to identify enterovirus and serotypes.

RESULTS

A total of 424 patients were included in this study and their non-duplicated cerebrospinal fluid specimens were collected during the acute stage of illness. Based on PCR assay, enterovirus was detected in 272 (64.15 %) patients, of whom, the ratio of male to female subjects was 1.99, and the mean age was 5.71 ± 3.55 years (range: 0.03-16 years). There were 17 serotypes identified. Echovirus 30 (24.63 %), Coxsackievirus A10 (20.96 %), Coxsackievirus A6 (18.01 %) accounted for 63.6 %, followed by Coxsackievirus B5 (7.72 %), Echovirus 6 (5.88 %), and other serotypes (22.8 %). Of the 10 (3.68 %) critically severe patients, all had refractory seizure, 8 required mechanical ventilation, 7 survivors had recurrent attacks of epilepsy and 3 abandoned treatment; Coxsackievirus A10, Echovirus 9, Coxsackievirus A2, Coxsackievirus A6 and Echovirus 6 were identified.

CONCLUSIONS

Non-polio enterovirus is the major pathogen causing aseptic meningitis, encephalitis and meningo-encephalitis in Chinese children and can cause life-threatening encephalitis and severe sequelae.

Hand, Foot, and Mouth Disease Caused by Coxsackievirus A6: A Preliminary Report from Istanbul

Hand, foot, and mouth disease (HFMD) is caused by various serotypes of Enterovirus genus. Coxsackievirus A16 (CV-A16) and enterovirus A71 (EV-A71) were known to be the only responsible agents for these epidemics; however, this opinion was challenged after the detection that coxsackievirus A6 (CV-A6) was the responsible species for the outbreak in Finland in 2008. HFMD is frequently seen in Turkey, and no detailed study on its clinical and microbiological epidemiology has previously been reported. The present study addresses this question. Twenty-seven patient samples collected between 2015 and 2017 were included in the study. Typing was conducted by RT-PCR and the sequencing applied directly to patient's samples and as well as to the viral cultures with pan-enterovirus and serotype-specific primers. The presence of Enterovirus in 12 of 27 HFMD samples was shown with RT-PCR. The causative agent for three of these 12 samples was CV-A16, one of the most frequent two serotypes around the world, and the remaining nine samples was CV-A6. The findings of the study are relevant since it pertains to the molecular epidemiology of HFMD in Turkey, a gateway country where different serotypes might be circulating and transmitted. The findings also support the notion that CV-A6 cases are rising in number, which has caused more severe clinical features and widespread rashes in recent outbreaks.

Hand, foot, and mouth disease (HFMD) is caused by various serotypes of Enterovirus genus. Coxsackievirus A16 (CV-A16) and enterovirus A71 (EV-A71) were known to be the only responsible agents for these epidemics; however, this opinion was challenged after the detection that coxsackievirus A6 (CV-A6) was the responsible species for the outbreak in Finland in 2008. HFMD is frequently seen in Turkey, and no detailed study on its clinical and microbiological epidemiology has previously been reported. The present study addresses this question. Twenty-seven patient samples collected between 2015 and 2017 were included in the study. Typing was conducted by RT-PCR and the sequencing applied directly to patient’s samples and as well as to the viral cultures with pan-enterovirus and serotype-specific primers. The presence of Enterovirus in 12 of 27 HFMD samples was shown with RT-PCR. The causative agent for three of these 12 samples was CV-A16, one of the most frequent two serotypes around the world, and the remaining nine samples was CV-A6. The findings of the study are relevant since it pertains to the molecular epidemiology of HFMD in Turkey, a gateway country where different serotypes might be circulating and transmitted. The findings also support the notion that CV-A6 cases are rising in number, which has caused more severe clinical features and widespread rashes in recent outbreaks.

Hand, Foot, and Mouth Disease Caused by Coxsackievirus A6: A Preliminary Report from Istanbul

Hand, foot, and mouth disease (HFMD) is caused by various serotypes of Enterovirus genus. Coxsackievirus A16 (CV-A16) and enterovirus A71 (EV-A71) were known to be the only responsible agents for these epidemics; however, this opinion was challenged after the detection that coxsackievirus A6 (CV-A6) was the responsible species for the outbreak in Finland in 2008. HFMD is frequently seen in Turkey, and no detailed study on its clinical and microbiological epidemiology has previously been reported. The present study addresses this question. Twenty-seven patient samples collected between 2015 and 2017 were included in the study. Typing was conducted by RT-PCR and the sequencing applied directly to patient’s samples and as well as to the viral cultures with pan-enterovirus and serotype-specific primers. The presence of Enterovirus in 12 of 27 HFMD samples was shown with RT-PCR. The causative agent for three of these 12 samples was CV-A16, one of the most frequent two serotypes around the world, and the remaining nine samples was CV-A6. The findings of the study are relevant since it pertains to the molecular epidemiology of HFMD in Turkey, a gateway country where different serotypes might be circulating and transmitted. The findings also support the notion that CV-A6 cases are rising in number, which has caused more severe clinical features and widespread rashes in recent outbreaks.

Hand, foot, and mouth disease associated with coxsackievirus A10: more serious than it seems

INTRODUCTION

Hand, foot, and mouth disease (HFMD) is a common viral childhood illness, that has been a severe public health concern worldwide, particularly in the Asia-Pacific region. According to epidemiological data of HFMD during the past decade, the most prevalent causal viruses were enterovirus (EV)-A71, coxsackievirus (CV)-A16, CV-A6, and CV-A10. The public health burden of CV-A10-related diseases has been underestimated as their incidence was lower than that of EV-A71 and CV-A16 in most HFMD outbreaks. However, cases of CV-A10 infection are more severe, and its genome is more variable, which has alerted the research community worldwide. Areas covered: In this paper, studies on the epidemiology, laboratory diagnosis, clinical manifestations, molecular epidemiology, seroepidemiology, animal models of CV-A10, and vaccines and antiviral strategies against this genotype are reviewed. In addition, the genetic evolution of circulating strains was analyzed. Expert opinion: Multivalent vaccines against EV-A71, CV-A16, CV-A6, and CV-A10 should be a next-step HFMD vaccine strategy.

Persistence of infectious Enterovirus within free-living amoebae - A novel waterborne risk pathway?

Free-living amoebae (FLA) are phagocytic protozoa found in natural and engineered water systems. They can form disinfectant-resistant cysts, which can harbor various human pathogenic bacteria, therefore providing them with a means of environmental persistence and dispersion through water distribution and other engineered water systems. The association of FLA with human viruses has been raised, but the limited data on the persistence of infectious virions within amoebae leaves this aspect unresolved. Enteroviruses can cause a wide range of illness and replicate in human respiratory and gastrointestinal tracts, both of which could be exposed through contact with contaminated waters if virus detection and removal are compromised by virion internalization in free-living protozoa. This is especially problematic for high-risk contaminants, such as coxsackieviruses, representative members of the Enterovirus genus that are likely infectious at low doses and cause a variety of symptoms to a vulnerable portion of the population (particularly infants). To investigate Enterovirus persistence within free-living amoebae we co-cultured an infectious clinical coxsackievirus B5 (CVB5) isolate, with the commonly reported tap water amoeba Vermamoeba vermiformis, after which we tracked virus localization and persistence in co-culture over time through a combination of advanced imaging, molecular and cell culture assays. Our results clearly demonstrate that infectious CVB5 can persist in all life stages of the amoebae without causing any visible injury to them. We also demonstrated that the amoeba generated vesicles containing virions that were expelled into the bulk liquid surroundings, a finding previously described for FLA-bacteria interactions, but not for FLA and human pathogenic viruses. Therefore, our findings suggest that the ability of CVB5 to persist in V. vermiformis could be a novel waterborne risk pathway for the persistence and dispersion of infectious human enteric viruses through water systems.

Amplification and next generation sequencing of near full-length human enteroviruses for identification and characterisation from clinical samples

More than 100 different enterovirus (EV) genotypes infect humans and contribute to substantial morbidity. However, current methods for characterisation of full-length genomes are based on Sanger sequencing of short genomic regions, which are labour-intensive and do not enable comprehensive characterisation of viral populations. Here, we describe a simple and sensitive protocol for the amplification and sequencing of near full-length genomes of human EV species using next generation sequencing. EV genomes were amplified from 89% of samples tested, with C_t values ranging between 15.7 and 39.3. These samples included 7 EV-A genotypes (CVA2, 5–7, 10, 16 and EV71), 19 EV-B genotypes (CVA9, CVB1-6, ECHO3, 4, 6, 7, 9, 11, 16, 18, 25, 29, 30, and EV69), 3 EV-C genotypes (CVA19 and PV2, 3) and 1 EV-D genotype (EV70). We characterised 70 EVs from 58 clinical stool samples and eight reference strains, with a minimum of 100X depth. We found evidence of co-infection in four clinical specimens, each containing two distinct EV genotypes (CVB3/ECHO7, CVB3/ECHO18 and ECHO9/30). Characterisation of the complete genome provided conclusive genotyping of EVs, which can be applied to investigate the intra-host virus evolution of EVs, and allows further identification and investigation of EV outbreaks.

An emerging and expanding clade accounts for the persistent outbreak of Coxsackievirus A6-associated hand, foot, and mouth disease in China since 2013

Enterovirus (EV)-A71 and Coxsackievirus (CV)-A16 have historically been the major pathogens of hand, foot, and mouth disease (HMFD) in China; however, CV-A6， which had previously received little attention, became the predominant pathogen in 2013, and has remained one of the common pathogens since then. In this work, we conducted a molecular epidemiology study of CV-A6-associated HFMD in Xiamen from 2009 to 2015. The data showed CV-A6 pandemics had a certain periodicity rather than occurring randomly. Evolution analysis based on near-complete VP1 nucleotide sequences showed subgenotype D5 lineage 4 strains account for the persistent outbreak of CV-A6-associated HFMD in China since 2013. Alignment analysis revealed eight candidate amino acid substitutions in VP1, which may provide useful information for the research of CV-A6 virulence enhancement. This study contributed to elucidating the circulation patterns and genetic characteristics of CV-A6 in China; however, further surveillance and intervention in CV-A6 epidemics is recommended.

Epidemiological surveillance of hand, foot and mouth disease in Shanghai in 2014-2016, prior to the introduction of the enterovirus 71 vaccine

Hand, foot, and mouth disease (HFMD) is mainly epidemic in China and Southeast Asian countries. A novel enterovirus 71 vaccine has been available in China for preventing severe HFMD since 2016. Knowledge of the dynamic epidemiology of HFMD in different regions is necessary for appropriate intervention strategies. This study focused on the citywide surveillance data on the epidemiology and etiology of HFMD in Shanghai during 2014–2016. In these 3 years, the total numbers of reported HFMD cases were 65,018, 39,702, and 57,548, respectively; the numbers of severe cases (case-severity ratios) were 248 (0.38%), 35 (0.09%), and 59 (0.10%), respectively. Children <6 years old accounted for 86.65% to 89.34% of HFMD cases and 91.53 to 97.14% of severe cases. EV-A71 caused all three fatal cases. In severe cases, the detection rate of EV-A71 was 77.82% in 2014, 100% in 2015 and 98.31% in 2016. In uncomplicated inpatient cases, the detection rates of EV-A71, CV-A16, CV-A6, and CV-A10 were, respectively, 43.40, 22.10, 30.73, and 1.89% in 2014; 28.52, 6.46, 53.61, and 7.98% in 2015; and 31.79, 14.15, 44.55, and 4.64% in 2016. In mild community cases, the detection rates of EV-A71, CV-A16, CV-A6, and CV-A10 were, respectively, 25.78, 41.64, 22.93, and 1.78% in 2014; 17.41, 21.23, 50.99, and 3.15% in 2015; and 18.92, 27.84, 45.11, and 1.64% in 2016. Among the cluster outbreaks, the most common pathogen was CV-A16 in 2014 (50.69%) and 2015 (38.10%) and CV-A6 in 2016 (36.30%). These findings show that HFMD outbreaks remained at a high level in Shanghai during 2014–2016. CV-A6 was emerging as the most common pathogen causing HFMD.

Genetic characterization of enterovirus strains identified in Hand, Foot and Mouth Disease (HFMD): Emergence of B1c, C1 subgenotypes, E2 sublineage of CVA16, EV71 and CVA6 strains in India

Hand, Foot and Mouth disease (HFMD) is a common childhood disease and caused due to Enterovirus-A (EV-A), EV-B and EV-C species worldwide. Cases of HFMD were reported from, Ahmedabad (Gujarat, 2012) and Pune (Maharashtra, 2013-2014) in India. The present study highlights the identification of EV strains (CVA16, CVA6, CVA4 and Echo12), characterization of subgenotypes of CVA16, CVA6 strains during 2012-14 and CVA16, CVA6, EV71 strains reported from the earlier study (2009-10) in HFMD cases from India. A total 158 clinical specimens collected from 64 HFMD cases (2012-2014) were included in the study. EV detection was carried out by 5'NCR based RT-PCR, molecular typing and subgenotyping was by VP1/2A junction or VP1, full VP1 gene amplification respectively followed by phylogenetic analysis. The present study reports 63.92% (101/158) EV positivity by RT-PCR. Ninety four of the 101 (93.06%) EV positive strains were amplified by VP1/2A junction or VP1 regions. Sequence analysis revealed the presence of CVA16 (61.7%), CVA6 (34.04%), CVA4 and Echo12 (4.3%). A total of 114 EV positive strains were genotyped using full and partial VP1 region. All CVA16 Indian strains (n=70) clustered with rarely reported B1c subgenotype, CVA6 (n=43) and EV71 (n=1) strains clustered with sub-lineage E2 and C1 subgenotypes respectively. In summary, the study reports genetic characterization of CVA16, CVA6, CVA4 and Echo12 strains in HFMD cases from India. Circulation of B1c subgenotype of CVA16, E2 sub-lineage of CVA6 and C1 subgenotype of EV 71 strains in HFMD cases were reported for the first time from India. This study helps to understand the genotype distribution, genetic diversity of EV strains associated with HFMD from Eastern, Western and Southern regions in India.

Severe hand, foot and mouth disease associated with Coxsackievirus A10 infections in Xiamen, China in 2015

BACKGROUND

Coxsackievirus A10 (CV-A10) is one of the etiological agents associated with hand, foot and mouth disease (HFMD) and usually causes mild cases. During 2009-2014, no severe cases caused by CV-A10 was reported in Xiamen, China, however, an increase in cases was seen in 2015.

OBJECTIVES

We aimed to perform a retrospective molecular epidemiological analysis of HFMD associated with CV-A10 infections in Xiamen.

STUDY DESIGN

CV-A10 VP1 (n=41) capsid and full-length or near full-length genomes (n=14) were sequenced. Phylogenetic trees were constructed based on these sequences and other reference sequences and nucleotide and amino acid changes were characterized.

RESULTS

From 2009-2014, no laboratory-confirmed CV-A10 infections associated with severe cases were identified, however, in 2015, 39% (7/18) of severe HFMD cases were CV-A10 infections. Sequence analysis of severe and non-severe CV-A10 HFMD cases determined that severe cases predominantly clustered with an emerging clade E lineage A strain which contained 4 nucleotide changes in 5' UTR and 5 amino acid substitutions in structural and non-structural proteins.

CONCLUSIONS

The results indicate CV-A10 infection may be emerging as a new and major cause of severe HFMD and CV-A10 surveillance should be increased and considered in HFMD prevention and control strategies.

Epidemics and aetiology of hand, foot and mouth disease in Xiamen, China, from 2008 to 2015

Over the past 8 years, human enteroviruses (HEVs) have caused 27 227 cases of hand, foot and mouth disease (HFMD) in Xiamen, including 99 severe cases and six deaths. We aimed to explore the molecular epidemiology of HFMD in Xiamen to inform the development of diagnostic assays, vaccines and other interventions. From January 2009 to September 2015, 5866 samples from sentinel hospitals were tested using nested reverse transcription PCR that targeted the HEV 5' untranslated region and viral protein 1 region. Of these samples, 4290 were tested positive for HEV and the amplicons were sequenced and genotyped. Twenty-two genotypes were identified. Enterovirus 71 (EV71) and coxsackieviruses A16, A6 and A10 (CA16, CA6 and CA10) were the most common genotypes, and there were no changes in the predominant lineages of these genotypes. EV71 became the most predominant genotype every 2 years. From 2013, CA6 replaced CA16 as one of the two most common genotypes. The results demonstrate the vast diversity of HFMD pathogens, and that minor genotypes are able to replace major genotypes. We recommend carrying-out long-term monitoring of the full spectrum of HFMD pathogens, which could facilitate epidemic prediction and the development of diagnostic assays and vaccines.

A novel inactivated enterovirus 71 vaccine can elicit cross-protective immunity against coxsackievirus A16 in mice

Hand, foot, and mouth disease (HFMD) is a highly contagious disease that mainly affects infants and children. Enterovirus 71 (EV71) and coxsackievirus A16 (CA16) are the major pathogens of HFMD. Two EV71 vaccines were recently licensed in China and the administration of the EV71 vaccines is believed to significantly reduce the number of HFMD-related severe or fatal cases. However, a monovalent EV71 vaccine cannot cross-protect against CA16 infection, this may result in that it cannot effectively control the overall HFMD epidemic. In this study, a chimeric EV71, whose VP1/210-225 epitope was replaced by that of CA16, was constructed using a reverse genetics technique to produce a candidate EV71/CA16 bivalent vaccine strain. The chimeric EV71 was infectious and showed similar growth characteristics as its parental strain. The replacement of the VP1/210-225 epitope did not significantly affect the antigenicity and immunogenicity of EV71. More importantly, the chimeric EV71 could induce protective immunity against both EV71 and CA16, and protect neonatal mice against either EV71 or CA16 lethal infections, the chimeric EV71 constructed in this study was shown to be a feasible and promising candidate bivalent vaccine against both EV71 and CA16. The construction of a chimeric enterovirus also provides an alternative platform for broad-spectrum HFMD vaccines development.

Changes in enterovirus serotype constituent ratios altered the clinical features of infected children in Guangdong Province, China, from 2010 to 2013

Background

Enterovirus (EV)-related hand, foot, and mouth disease/herpangina (HFMD/HA) has been prevalent in Guangdong Province, China, since 2010.

Methods

Clinical data for EV-related HFMD/HA inpatients admitted to the Department of Paediatrics of Zhujiang Hospital from 2010 to 2013 were retrospectively reviewed. The corresponding EV serotypes were also determined by reverse transcription-polymerase chain reaction or BLAST analysis of the sequenced partial lengths of the viral protein1/5′-untranslated region.

Results

A total of 867 eligible inpatients admitted during 2010–2013 were included in the study. Of these, the serotype of the responsible EV was successfully identified in 824 cases. The incidence of enterovirus 71 (EV71) infection amongst pediatric HFMD/HA inpatients decreased dramatically from 55.5 % in 2010 to 8.1 % in 2013, with a similar decrease recorded for coxsackievirus A16 (CVA16). However, the incidence of non-EV71/CVA16 infection increased from 30.0 % in 2010 to 83.8 % in 2013. We noted that the types of infection caused by different EV serotypes varied: EV71 was responsible for 100 % of the paralysis cases (26/26), 84.6 % of the deaths (11/13), and 84.1 % of cases with severe central nervous system involvement (SCNSI) (74/88); echovirus contributed to 16.4 % of the deaths (2/13) and 4.4 % of the SCNSI cases; and coxsackievirus accounted for only 2.2 % of the SCNSI cases (2/90). The clinical features of HFMD/HA cases varied greatly during the time period examined, with drastic changes in the hospitalization rates (45.1, 63.7, 36.4, and 19.1 % for 2010, 2011, 2012, and 21013, respectively), mortality rates (2.3, 0.9, 2.5, and 0.0 %, respectively), paralysis (5.1, 1.2, 5.4, and 0.0 %, respectively), SCNSI (16.8, 7.1, 12.7, and 2.2 %, respectively), and acute respiratory infection (21.1, 22.0, 45.9, and 59.0 %, respectively).

Conclusions

The incidences of infection caused by different EV serotypes, along with the clinical features of HFMD/HA cases, changed drastically in Guangdong Province, China, from 2010 to 2013, with the biggest changes observed in 2013. The changed constituent ratios of the different EV serotypes might therefore be responsible for the differences in the observed clinical features of HFMD/HA during this period.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1690-0) contains supplementary material, which is available to authorized users.

Development of a highly sensitive real-time nested RT-PCR assay in a single closed tube for detection of enterovirus 71 in hand, foot, and mouth disease

Enterovirus 71 (EV71) is one of the major causative agents of outbreaks of hand, foot, and mouth disease (HFMD). A commercial TaqMan probe-based real-time PCR assay has been widely used for the differential detection of EV71 despite its relatively high cost and failure to detect samples with a low viral load (Ct value > 35). In this study, a highly sensitive real-time nested RT-PCR (RTN RT-PCR) assay in a single closed tube for detection of EV71 in HFMD was developed. The sensitivity and specificity of this assay were evaluated using a reference EV71 stock and a panel of controls consisting of coxsackievirus A16 (CVA16) and common respiratory viruses, respectively. The clinical performance of this assay was evaluated and compared with those of a commercial TaqMan probe-based real-time PCR (qRT-PCR) assay and a traditional two-step nested RT-PCR assay. The limit of detection for the RTN RT-PCR assay was 0.01 TCID₅₀/ml, with a Ct value of 38.3, which was the same as that of the traditional two-step nested RT-PCR assay and approximately tenfold lower than that of the qRT-PCR assay. When testing the reference strain EV71, this assay showed favorable detection reproducibility and no obvious cross-reactivity. The testing results of 100 clinical throat swabs from HFMD-suspected patients revealed that 41 samples were positive for EV71 by both RTN RT-PCR and traditional two-step nested RT-PCR assays, whereas only 29 were EV71 positive by qRT-PCR assay.

An epidemic of coxsackievirus B3 infection in infants and children in Jiangsu Province, China: a prospective cohort study

To investigate the epidemiological data on coxsackievirus B3 (CVB3) infection and its incidence in infants and children, a prospective cohort study was carried out from 2012 to 2014 in Jiangsu Province, China. According to the results of seropositive rates and NTAb titers of CVB3, an epidemic of CVB3 infection was found, and a dynamic change in CVB3 neutralizing antibody was also observed. One case was recorded with CVB3-associated hand, foot and mouth disease (HFMD), and the isolates belonged to the CVB3 D2 subtype. Our data help us to better understand the epidemic characteristics of CVB3 infection in infants and children.

Enterovirus-related diarrhoea in Guangdong, China: clinical features and implications in hand, foot and mouth disease and herpangina

Background

A series of complications caused by enteroviruses, including meningitis, encephalitis, acute flaccid paralysis, acute cardiopulmonary failure, respiratory infection, and myocardial injury have been reported in hand, foot and mouth disease/herpangina (HFMD/HA). However, the complication of diarrhoea caused by enteroviruses has been neglected, and a summary of its clinical features and impact on HFMD/HA is unavailable.

Methods

We included inpatients with HFMD/HA admitted to the Paediatric Department of Zhujiang Hospital during 2009–2012. We summarised and compared clinical data for cases with and without diarrhoea, and determined enterovirus serotypes by reverse transcriptase polymerase chain reaction and genotyping based on a partial-length fragment of viral protein 1 or the 5’-untranslated region.

Results

There were 804 inpatients with HFMD/HA and 28 (3.5 %) presented with diarrhoea. Gastrointestinal symptoms were mild in most cases of diarrhoea (82.1 %), with high prevalence of no dehydration (82.1 %), short duration of diarrhoea (78.6 %) and watery stools (75.0 %). The prevalence of multi-organ dysfunction syndrome (10.7 vs 0.40 %) (p = 0.001), hepatic injury (14.3 vs 3.4 %) (p = 0.019), myocardial injury (21.4 vs 6.1 %) (p = 0.002) and convulsion (21.4 vs 7.2 %) (p = 0.016) was significantly higher in the diarrhoea than no diarrhoea group. There was no significant difference between the two groups regarding prevalence of death, altered consciousness, paralysis, central nervous system involvement, or acute respiratory infection.

Conclusions

Most patients with diarrhoea caused by enteroviruses circulating in Guangdong Province in 2009–2012 had mild or moderate gastrointestinal symptoms. Although enterovirus-related diarrhoea caused additional multi-organ dysfunction syndrome, hepatic injury and myocardial injury in children with HFMD/HA, timely intervention efficiently reduced disease severity and improved outcome.

Development and evaluation of rapid point-of-care tests for detection of Enterovirus 71 and Coxsackievirus A16 specific immunoglublin M antibodies

Two colloidal gold immunochromatographic assays (CGIAs) for detection of EV71- and CA16- immunoglobulin M (IgM) were developed and evaluated. A total of 1465 sera collected from children with hand, foot, and mouth disease (HFMD), non-HFMD patients and healthy children. The sensitivity of IgM CGIA tests for EV71 and CA16 were 97.6% (330/338) and 91.6% (296/323) respectively, compared to those who were viral RNA positive by PCR. Their performances were comparable to those of commercial ELISA kits, with agreement of 98.1% for EV71-IgM and 97.3% for CA16-IgM. In addition, for EV71- and CA16-IgM CGIAs, the results of whole blood samples were 99.6% (248/249) and 100% (191/191) concordant to those with serum samples, respectively. As rapid point-of-care (POC) tests, the two CGIAs were suitable to be used in community clinic units, especially in resource-poor areas and will facilitate the control of 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.

Etiology of Multiple Non-EV71 and Non-CVA16 Enteroviruses Associated with Hand, Foot and Mouth Disease in Jinan, China, 2009-June 2013

Hand, foot, and mouth disease (HFMD) is an infectious disease caused by human enterovirus 71 (EV71), coxsackievirus A16 (CVA16) and other enteroviruses. It is of interest that other enteroviruses associated with HFMD in Jinan have been rarely reported. The aim of the present study is to detect and characterize the circulating serotypes of non-EV71 and non-CVA16 enteroviruses associated with HFMD in Jinan city, Shandong province, China. A total of 400 specimens were collected from clinically diagnosed HFMD cases in Jinan from January 2009 to June 2013. All specimens were infected with non-EV71 and non-CVA16 enteroviruses previously confirmed by RT-PCR or real-time PCR according to the protocols at that time. The GeXP-based multiplex RT-PCR assay (GeXP assay) was performed to investigate the pathogen spectrum of 15 enteroviruses (coxsackieviruses A4, A5, A6, A9, A10, A16; coxsackieviruses B1, B3, B5; Echoviruses 6, 7, 11, 13, 19 and EV71) infections associated with HMFD. For GeXP assay negative samples, reverse transcription nested PCR (nested RT-PCR) based on the 5’ -untranslated region (5’- UTR) sequence and phylogenetic analysis were conducted to further explore the etiology of multiple enteroviruses. The results showed that a total of twenty serotypes of enteroviruses (including EV71 and CVA16) were identified by GeXP assay and nested RT-PCR. The most circulating twelve serotypes of enteroviruses with HFMD in Jinan from 2009 to June 2013 were EV71, CVA16, CVA10, CVA6, CVA12, CVA2, Echo3, CVA4, CVA9, CVB1, CVB3 and Echo6. CVA10 and CVA6 were the most prevalent pathogens other than EV71 and CVA16 in Jinan and their most prevalent seasons were spring and summer, and a slight increase was observed in autumn and early winter. It should be noted that mixed-infections were identified by GeXP assay and the phylogenetic tree clearly discriminated the multiple pathogens associated with HFMD. Our results thus demonstrate that there was a clear lack of a reliable testing method for EV71 and CVA16 and multiple non-EV71 and non-CVA16 enteroviruses associated with HFMD were present in Jinan. The GeXP assay combined with nested RT-PCR based on 5’-UTR region could meet the need for the national surveillance of multiple enteroviruses or the investigation of epidemic outbreaks triggered by enteroviruses in the future.

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.

Epidemiological and etiological characteristics of hand, foot, and mouth disease in Wuhan, China from 2012 to 2013: outbreaks of coxsackieviruses A10

Hand-foot-mouth disease (HFMD) is a common infectious disease which often occurs in young children. It is caused by enteroviruses, most commonly enterovirus71 (EV71) and Coxsackievirus A16 (CVA16). The present study focuses on the molecular epidemiology of the pathogen of HFMD in the Wuhan region of China during the period 2012 to 2013. A total of 463 viruses were isolated from throat swab of 3,208 HFMD patients and analyzed by quantitative RT-PCR with all sets of specific primers for EV71, CVA16, and pan-enterovirus. Of the 463 viruses, 111 (21.2%) were EV71, 52 (9.6%) were CVA16, and 300 (69.2%) were pan-enterovirus. In pan-enterovirus isolations 190 (52.8%) were CVA10, 50 (13.9%) were CVA4, 30 were CB2, 17 were CB3, 13 were CB5 identified by VP4 gene sequencing. Eleven EV71 isolates were complete genome sequenced and phylogenetic analysis revealed that the EV71 strains that circulated in Wuhan belonged to the C4 subgenotype. Among the 190 CVA10 isolations, 187 CVA10 strains have the same nucleotide sequence, the other three CVA10 strains belongs to another type of nucleotide sequence. Phylogenetic analysis based on 19 CVA10 isolations suggested that they belonged to the clade of Chinese strains, but form different clusters isolated from Japan, Europe. This study showed that EVA71 and CVA16 were detected as the predominant viruses (>60%) in 2012 and the total reported HFMD cases attained a peak in June and July. In contrast, CVA10 was also detected during April 2012 and replaced EVA71 and CVA16 as the major HFMD-associated pathogen from May 2013.

Phylogenetic analysis of the major causative agents of hand, foot and mouth disease in Suzhou City, Jiangsu province, China, in 2012-2013

Hand, foot and mouth disease (HFMD) is a serious public health problem that has emerged over the past several decades. Pathogen detection by the Chinese national HFMD surveillance system has focused mainly on enterovirus 71 (EV71) and coxsackievirus A16 (CA16). Therefore, epidemiological information regarding the other causative enteroviruses is limited. To identify the pandemic enterovirus in Suzhou, Jiangsu province, China, clinical samples from patients with HFMD were collected from 2012 to 2013 and analyzed. The results revealed that CA16 was the most dominant HFMD pathogen in 2012, whereas CA6 and CA10 were the dominant pathogens in 2013. Phylogenetic analysis revealed that the C4a sub-genogroup of EV71 and the B1a and B1b sub-genogroups of CA16 continued to evolve and circulate in Suzhou. The CA6 strains were assigned to six genotypes (A–F) and the CA10 strains were assigned to seven genotypes (A–G), with clear geographical and temporal distributions. All of the CA6 strains in Suzhou belonged to genogroup F, and there were several lineages circulating in Suzhou. All of the CA10 strains in Suzhou belonged to genogroup G, and they had the same genetic origin. Co-infections of EV71/CA16 and CA6/CA10 were found in the samples, and bootscan analysis of 5′-untranslated regions (UTRs) revealed that some CA16 strains in Suzhou had genetic recombination with EV71. This property might allow CA16 to alter its evolvability and circulating ability. This study underscores the need for surveillance of CA6 and CA10 in the Yangtze River Delta and East China.

Echovirus 7 associated with hand, foot, and mouth disease in mainland China has undergone a recombination event

To investigate the evolution of echovirus 7 (Echo7) strains and the relationship between Echo7 strains and the prototype strain Wallace, phylogenetic analysis of Echo7 strains prevailing in mainland China was performed. The Echo7 strain, DH22G/JS/2012 was isolated from a 32-month-old boy who was clinically diagnosed with HFMD. The complete genome sequence of this isolate was determined after the virus was propagated in cell culture. Phylogenetic analysis showed that the subgroups B1 and C1 prevailed in mainland China from 1998 to 2012 and that the subgroup B2 began to circulate in mainland China in 2009. The result of Simplot analysis showed that the Echo7 strain DH22G/JS/2012 is a recombinant coxsackievirus B4 (CVB4) that circulated in mainland China in 2010.

A one-step, triplex, real-time RT-PCR assay for the simultaneous detection of enterovirus 71, coxsackie A16 and pan-enterovirus in a single tube

The recent, ongoing epidemic of hand, foot, and mouth disease (HFMD), which is caused by enterovirus infection, has affected millions of children and resulted in thousands of deaths in China. Enterovirus 71 (EV71) and coxsackie A16 (CA16) are the two major distinct pathogens for HFMD. However, EV71 is more commonly associated with neurologic complications and even fatalities. Therefore, simultaneously detecting and differentiating EV71 and CA16 specifically from other enteroviruses for diagnosing HFMD is important. Here, we developed a one-step, triplex, real-time RT-PCR assay for the simultaneous detection of EV71, CA16, and pan-enterovirus (EVs) in a single tube with an internal amplification control. The detection results for the serially diluted viruses indicate that the lower limit of detection for this assay is 0.001–0.04 TCID₅₀/ml, 0.02 TCID₅₀/ml, and 0.001 TCID₅₀/ml for EVs, EV71, and CA16, respectively. After evaluating known HFMD virus stocks of 17 strains of 16 different serotypes, this assay showed a favorable detection spectrum and no obvious cross-reactivity. The results for 141 clinical throat swabs from HFMD-suspected patients demonstrated sensitivities of 98.4%, 98.7%, and 100% for EVs, EV71, and CA16, respectively, and 100% specificity for each virus. The application of this one-step, triplex, real-time RT-PCR assay in clinical units will contribute to HFMD surveillance and help to identify causative pathogen in patients with suspected HFMD.

Development of an enzyme-linked immunosorbent spot assay to measure serum-neutralizing antibodies against coxsackievirus B3

Coxsackievirus B3 (CVB3) is the most common pathogen that induces acute and chronic viral myocarditis in children. The cytopathic effect (CPE)-based neutralization test (Nt-CPE) and the plaque reduction neutralization test (PRNT) are the most common methods for measuring neutralizing antibody titers against CVB3 in blood serum samples. However, these two methods are inefficient for CVB3 vaccine clinical trials, which require the testing of a large number of serum specimens. In this study, we developed an efficient neutralization test based on the enzyme-linked immunospot (Nt-ELISPOT) assay for measuring CVB3-neutralizing antibodies. This modified ELISPOT assay was based on the use of a monoclonal antibody against the viral capsid protein VP1 to detect the cells that are infected with CVB3, which, after immunoperoxidase staining, are counted as spots using an automated ELISPOT analyzer. Using the modified ELISPOT assay, we characterized the infection kinetics of CVB3 and divided the infection process of CVB3 on a cluster of cells into four phases. The stability of the Nt-ELISPOT was then evaluated. We found that over a wide range of infectious doses (10(2) to 10(6.5)× 50% tissue culture infectious dose [TCID(50)] per well), the neutralizing titers of the sera were steady as long as they were tested during the log phase or the first half of the stationary phase of growth of the spots. We successfully shortened the testing period from 7 days to approximately 20 h. We also found that there was a good correlation (R(2) = 0.9462) between the Nt-ELISPOT and the Nt-CPE assays. Overall, the Nt-ELISPOT assay is a reliable and efficient method for measuring neutralizing antibodies in serum.

Detection and distribution of culturable Human Enteroviruses through environmental surveillance in Milan, Italy

AIMS

Human Enteroviruses (HEVs) infections have a significant impact on public health, being implicated in outbreaks of meningitis, encephalitis, hand-foot-mouth disease and other acute and chronic manifestation. In the strategic plan for poliomyelitis eradication, the environmental surveillance of poliovirus (PV) has been identified by the World Health Organization (WHO) as an activity that can complement the surveillance of polio. Having wastewater samples available for PV surveillance allows us to study nonpolio enteroviruses (NPEVs) circulating in the study population, which are widely spread.

METHODS AND RESULTS

This study was carried out according to the WHO guidelines for environmental surveillance of PV and analysed the circulation of PV and NPEVs through the isolation of viruses in cell cultures in Milan area; from 2006 to 2010, 321 wastewater samples were collected, regularly over time, at the inlet of three diverse waste water treatment plants (WWTPs). Culturable HEVs were isolated in 80% of sewage samples: all isolates belonged to the HEV-B group and those circulating more intensely were CVB5 and Echo 6, while CVB4 was the predominant serotype found in 2010. In this study, two type 2 PVs were isolated, both characterized as Sabin like.

CONCLUSION

Environmental monitoring of HEVs in Milan has proved to be an interesting tool to investigate the circulation and distribution of viruses.

SIGNIFICANCE AND IMPACT OF THE STUDY

The detection of PV and other NPEV could be predictive of possible re-emergence of these viruses with an impact on public health. NPEV monitoring could also be a powerful public health tool to investigate the possible role of NPEV in different clinical manifestations.