Molecular characteristics of hand, foot, and mouth disease for hospitalized pediatric patients in Yunnan, China

Molecular characterization of a novel clade echovirus 3 isolated from patients with hand-foot-and-mouth disease in southwest China

Echovirus 3 (E3) belongs to the species Enterovirus B. Currently, three nearly whole-genome sequences of E3 are available in GenBank in China. In this study, we determined the whole genomic sequences of six E3 strains isolated from the stools of patients with hand-foot-and-mouth disease in Southwest China in 2022. Their nucleotide and amino acid sequences shared 82.1%-86.4% and 96.6%-97.2% identity with the prototype Morrisey strain, respectively, and showed 87.1% and 97.2% mutual identity. The six E3 strains are not clustered with other Chinese strains and formed a novel subgenotype (C6) with the recent American and British strains. Recombination analyses revealed that intertype recombination had occurred in the 2 C and 3D regions of the six E3 strains with coxsackieviruses B5 and B4, respectively. This study augments the nearly whole-genome sequences of E3 in the GenBank database and extends the molecular characterization of this virus in China.

TMEM173 rs7447927 genetic polymorphism and susceptibility to severe enterovirus 71 infection in Chinese children

INTRODUCTION

This study was designed to explore the association between the TMEM173 polymorphism (rs7447927) and the severity of enterovirus 71 (EV71) infection among Chinese children.

METHODS

The TMEM173 polymorphism was identified in EV71-infected patients (n = 497) and healthy controls (n = 535) using the improved multiplex ligation detection reaction (iMLDR). The interferon-α (IFN-α) serum levels were detected using enzyme linked immunosorbent assay (ELISA).

RESULTS

The frequencies of the GG genotype and G allele of TMEM173 rs7447927 in the mild EV71 infection and severe EV71 infection groups were markedly higher than those in the control group. The GG genotype and G allele frequencies in severely infected EV71 patients were significantly higher than those in mildly infected EV71 patients. Severely infected EV71 patients with the GG genotype had higher white blood cell counts (WBC), and C-reactive proteins (CRP), and blood glucose (BG) levels, longer fever duration, higher vomiting frequency, spirit changes, and electroencephalography (EEG) abnormalities. IFN-α serum concentration in severely infected patients was significantly higher than in the mildly infected group. The IFN-α concentration in the GG genotype was significantly higher compared with those in the GC and CC genotypes in severe cases.

CONCLUSIONS

The TMEM173 rs7447927 polymorphism was associated with EV71 infection susceptibility and severity. The G allele and GG genotype are susceptibility factors in the development of severe EV71 infection in Chinese children.

Co-infection and enterovirus B: post EV-A71 mass vaccination scenario in China

BACKGROUND

Hand, foot, and mouth disease (HFMD) is a common child infectious disease caused by more than 20 enterovirus (EV) serotypes. In recent years, enterovirus A71 (EV-A71) has been replaced by Coxsackievirus A6 (CV-A6) to become the predominant serotype. Multiple EV serotypes co-circulate in HFMD epidemics, and this study aimed to investigate the etiological epidemic characteristics of an HFMD outbreak in Kunming, China in 2019.

METHODS

The clinical samples of 459 EV-associated HFMD patients in 2019 were used to amplify the VP1 gene region by the three sets of primers and identify serotypes using the molecular biology method. Phylogenetic analyses were performed based on the VP1 gene.

RESULTS

Three hundred and forty-eight cases out of 459 HFMD patients were confirmed as EV infection. Of these 191 (41.61%) were single EV infections and 34.20% had co-infections. The EVs were assigned to 18 EV serotypes, of which CV-A6 was predominant (11.33%), followed by CV-B1 (8.93%), CV-A4 (5.23%), CV-A9 (4.58%), CV-A 16 (3.49%) and CV-A10 and CVA5 both 1.96%. Co-infection of CV-A6 with other EVs was present in 15.25% of these cases, followed by co-infection with CV-A16 and other EVs. The VP1 sequences used in the phylogenetic analyses showed that the CV-A6, CV-B1 and CV-A4 sequences belonged to the sub-genogroup D3 and genogroups F and E, respectively.

CONCLUSION

Co-circulation and co-infection of multiple serotypes were the etiological characteristic of the HFMD epidemic in Kunming China in 2019 with CV-A-6, CV-B1 and CV-A4 as the predominant serotypes. This is the first report of CV-B1 as a predominant serotype in China and may provide valuable information for the diagnosis, prevention and control of HFMD.

Association of the IRAK4 rs4251545 genetic polymorphism with severity of enterovirus-71 infection in Chinese children

INTRODUCTION

This study aimed to explore the association between the IRAK4 polymorphism rs4251545 and the severity of enterovirus 71 (EV71) infection in Chinese children.

METHODS

We analyzed the IRAK4 polymorphism rs4251545 in 617 EV71-infected patients and 410 controls using the improved multiplex ligation detection reaction. IRAK4 mRNA expression was tested by qRT-PCR. Serum concentrations of IL-6 and NF-κB were detected using ELISA.

RESULTS

The frequencies of the GA + AA genotype and A allele in the mild EV71 infection group and in the severe EV71 infection group were significantly higher than those in the normal control group. The frequency of the GA + AA genotype and A allele in severely infected EV71 patients was markedly higher than that in mildly infected EV71 patients. IRAK4 mRNA expression in mildly infected EV71 patients and severely infected patients was significantly higher than that in the control group. IRAK4 mRNA expression in GA + AA genotypes in both mild and severe EV71 infection groups was significantly higher than that in patients with the GG genotype. IL-6 concentration and the ratio of IL-6/NF-κB in severe EV71 cases were significantly lower in patients with the GA + AA genotype than in those with the GG genotype. The ratio of IL-6/NF-κB was distinctly higher in severely infected EV71 patients than in mildly infected and control subjects.

CONCLUSIONS

The IRAK4 polymorphism rs4251545 was associated with the susceptibility and severity of EV71 infection. The A allele is a susceptible factor in the development of severe EV71 infection in Chinese children.

A hSCARB2-transgenic mouse model for Coxsackievirus A16 pathogenesis

Background

Coxsackievirus A16 (CA16) is one of the neurotropic pathogen that has been associated with severe neurological forms of hand, foot, and mouth disease (HFMD), but its pathogenesis is not yet clear. The limited host range of CA16 make the establishment of a suitable animal model that can recapitulate the neurological pathology observed in human HFMD more difficult. Because the human scavenger receptor class B, member 2 (hSCARB2) is a cellular receptor for CA16, we used transgenic mice bearing human SCARB2 and nasally infected them with CA16 to study the pathogenicity of the virus.

Methods

Coxsackievirus A16 was administered by intranasal instillation to groups of hSCARB2 transgenic mice and clinical signs were observed. Sampled at different time-points to document and characterize the mode of viral dissemination, pathological change and immune response of CA16 infection.

Results

Weight loss and virus replication in lung and brain were observed in hSCARB2 mice infected with CA16, indicating that these animals could model the neural infection process. Viral antigens were observed in the alveolar epithelia and brainstem cells. The typical histopathology was interstitial pneumonia with infiltration of significant lymphocytes into the alveolar interstitial in lung and diffuse punctate hemorrhages in the capillaries of the brainstem. In addition, we detected the expression levels of inflammatory cytokines and detected high levels of interleukin IL-1β, IL-6, IL-18, and IFN-γ in nasal mucosa, lungs and brain tissues.

Conclusions

The hSCARB2-transgenic mice can be productively infected with CA16 via respiratory route and exhibited a clear tropism to lung and brain tissues, which can serve as a model to investigate the pathogenesis of CA16 associated respiratory and neurological disease.

Comparison of coxsackievirus A12 genome isolated from patients with different symptoms in Yunnan, Southwest China

Aim: Coxsackievirus A12 (CVA12) mainly causes hand–foot–mouth disease (HFMD) or herpangina (HA). Thus, the genomic characteristics of CVA12 isolates from Southwest China, especially the discrepancy between CVA12-HFMD and CVA12-HA were analyzed. Patients & methods: The full-length genome sequences of CVA12-HFMD and CVA12-HA were obtained and phylogenetic, nucleotide mutation, amino acid substitution and recombinant analyses were performed. Results: All CVA12 were closest to the Netherlands (2013) and have possibly recombined in the capsid coding region (P1) with other HEV-A. In the coding region, 54 base mutation result in 11 nonsynonymous mutations and four of them were identical mutations between CVA12-HFMD and CVA12-HA. Conclusion: Whether the presence of four consistent nonsynonymous mutation sites affect the virulence of the CVA12 deserves further study.

Seroprevalence of EV-A71 neutralizing antibodies following the 2011 epidemic in HCMC, Vietnam

Enterovirus-A71 (EV-A71) cyclically causes hand-foot-mouth disease (HFMD) epidemics in Asian children. An EV-A71 epidemic occurred in Southern Vietnam in 2011, but its scale is not clear. We collected residual sera from non-HFMD Vietnamese inpatients in 2012–2013 to determine seroprevalence of EV-A71 neutralizing antibodies, and measured cross-reactive neutralizing antibody titers against three EV-A71 genogroups. About 23.5% of 1-year-old children in Southern Vietnam has been infected by EV-A71, and the median age of infection was estimated to be 3 years. No significant antigenic variation could be detected among the three EV-A71 genogroups. The high seroprevalence of EV-A71 neutralizing antibody in children living in southern Vietnam indicates the necessity of introducing EV-A71 vaccines in southern Vietnam, particularly for children under 6 months of age. Moreover, it is critical to understand EV-A71 disease burden for formulating national vaccination policy.

Enterovirus-A71 (EV-A71), a member of the enterovirus genus, is a virulent pathogen causing neurological complications. EV-A71 mainly spreads through oral-fecal or oral-oral transmission, as well as respiratory droplets. EV-A71 outbreaks have cyclically occurred throughout some Asian countries since 1997, with millions of people affected. The presence of serum neutralizing antibodies to EV-A71 can represent the prevalence of previous EV-A71 infections and seroprevalence studies are widely used to understand prevalence of infectious diseases. The results of our study demonstrate that about 50% of young children under 3 years of age were infected during the 2011 epidemic in southern Vietnam. The high seroprevalence of EV-A71 neutralizing antibody in children living in southern Vietnam indicates the necessity of introducing EV-A71 vaccines, particularly for children under 6 months of age. Moreover, it is critical to understand EV-A71 disease burden for formulating national vaccination policy in the future.

A neonatal murine model of coxsackievirus A4 infection for evaluation of vaccines and antiviral drugs

Coxsackievirus A4 (CVA4) infection can cause hand, foot and mouth disease (HFMD), an epidemic illness affecting neonatal and paediatric cohorts, which can develop to severe neurological disease with high mortality. In this study, we established the first ICR mouse model of CVA4 infection for the evaluation of inactivated vaccines and antiviral drug screening. The CVA4 YT226R strain was selected to infect the neonatal mice and three infectious factors were optimized to establish the infection model. The 3-day-old neonatal mice exhibited clinical symptoms such as hind limb paralysis and death. The severe inflammatory reactions were closely related to the abnormal expression of the acute phase response proinflammatory cytokine IL-6 and an imbalance in the IFN-γ/IL-4 ratio. Importantly, the inactivated CVA4 whole-virus vaccine induced humoral immune responses in adult females and the maternal antibodies afforded mice complete protection against lethal dose challenges of homologous or heterologous CVA4 strains. Both IFN-α2a and antiserum inhibited the replication of CVA4 and increased the survival rates of neonatal mice during the early stages of infection. This neonatal murine model of CVA4 infection will be useful for the development of prophylactic and therapeutic vaccines and for screening of antiviral drugs targeting CVA4 to decrease morbidity and mortality.

Non-polio enteroviruses among healthy children in the Philippines

BACKGROUND

Enteroviruses (EVs) are most commonly associated with either mild or asymptomatic infections, however, the presence of silent carriers in the community has been proven to play a crucial role in the spread of diseases such as hand, foot, and mouth disease (HFMD) that records high incidence in Asia Pacific region. In the Philippines, limited information is available on the etiology and prevalence of enterovirus outside the Acute Flaccid Paralysis (AFP) surveillance, thus, a study to determine the baseline prevalence of Non-Polio Enteroviruses (NPEVs) among healthy Filipino children was conducted.

METHODS

A descriptive, cross-sectional study was performed to determine the prevalence of NPEV among healthy children under 6 years old in the Philippines. Duplicate stool samples were collected from 360 healthy children residing in three major urban cities in the country. Virus isolation and polymerase chain reaction were performed to identify enteroviruses present in the samples. To determine if the results of the study are comparable to the AFP surveillance data, the results of the study were compared to the prevalence and isolation rate among AFP cases of the similar cases collected the same year.

RESULTS

Prevalence of enteroviruses among healthy children was found to be at 24.7%. Comparing the NPEV rates from the study and AFP surveillance of similar age and the same year of collection, there was no significant difference in NPEV case prevalence. The study identified a total of 19 different enterovirus serotypes with majority belonging to species Enterovirus B (EV-B).

CONCLUSION

The study was able to establish a baseline NPEV case prevalence of 24.7% among healthy children aged under 6 years old in three major urban sites in the Philippines. The high isolation of NPEV among healthy children signifies continuous fecal-oral transmission of enteroviruses in the community.

VP1 of Enterovirus 71 Protects Mice Against Enterovirus 71 and Coxsackievirus B3 in Lethal Challenge Experiment

Enterovirus and Coxsackievirus are the major viruses that cause hand, foot, and mouth disease (HFMD) outbreaks worldwide. Several studies have shown the potential of viral envelope protein 1 (VP1) on providing protective effects from viral strains of different genotypes. However, whether VP1 has the cross-protection in Enteroviruses or Coxsackievirus has not been studied in-depth. In this study, the vp1 gene of Enterovirus 71 (EV71) and Coxsackievirus B3 (CB3) was inserted into the vector pET22b (+) to form the respective expression plasmids pEVP1 or pCVP1, and then transformed into Escherichia coli strain BL21 (DE3). The recombinant EVP1 or CVP1 protein was overexpressed successfully and effectively purified to homogeneity. Then, we identified that EVP1 and CVP1 protein could generate effectively specific humoral immunity and cellular immunity in mice, what's more, we determined the cross-protection of VP1 between EV71 and CB3 in a murine model. The results showed that immunization with EVP1 could effectively induce specific IgG and secretory IgA against CVP1 and the sera from EVP1-immunized mice could neutralize CB3 with mean titers 1:440. In contrast, no measurable neutralizing antibodies to EV71 were detected in CVP1-immunized mice. Then, newborn BALB/C mice, whose mother was immunized with EVP1 or CVP1, were administered with different lethal doses of EV71 or CB3. The EVP1 immunized group showed a 90% protective efficacy for a CB3 dosage of 120 LD₅₀, but the CVP1 immunized group showed no significantly different protective efficacy against 15 LD₅₀ of EV71 compared with the BSA immunized group. Hence, EVP1 is a promising subunit vaccine candidate against Enterovirus 71 and Coxsackievirus B3 caused HFMD.

Epidemiological study on hand, foot and mouth disease in Tongzhou District, Beijing, 2013-2017

Objective

To study the epidemiological characteristics of hand, foot and mouth disease (HFMD) in Tongzhou District, Beijing between 2013 and 2017.

Methods

Data on HFMD infections from 1 January 2013 to 31 December 2017 were collected from the Notifiable Infectious Diseases Reporting Information System and analysed. Serotyping of enteroviruses from samples from patients with HFMD was undertaken using reverse transcription–polymerase chain reaction.

Results

A total of 15 341 patients with HFMD were reported and 32 patients (0.2%) were classified as having severe HFMD. The annual mean incidence rate of HFMD was 219.3/100 000 of the general population. The incidence and case-severity rates of HFMD generally decreased between 2013 and 2017. In the floating migrant population, the incidence and cases-severity rates of HFMD were significantly higher than in the local population. The peak incidence and severity-case rates were at 2 years of age and > 90% of patients were ≤5 years. Enterovirus A71 and Coxsackievirus A16 were the predominant pathogens in 2013–2017.

Conclusions

During the 5-year period 2013–2017, the incidence rate and case-severity rate of HFMD generally decreased in Tongzhou District, Beijing. The floating migrant population and children ≤5 years of age were at the highest risk of HFMD.

A potential therapeutic neutralization monoclonal antibody specifically against multi-coxsackievirus A16 strains challenge

Coxsackievirus A16 (CA16) has caused worldwide epidemics of hand, foot and mouth disease (HFMD), particularly in infants and pre-school children. Currently, there are no vaccines or antiviral drugs available for CA16-associated disease. In this study, a CA16-specific monoclonal antibody (MAb) NA11F12 was derived with an epidemic CA16 strain (GenBank no. JX127258). NA11F12 was found to have high cross-neutralization activity against different CA16 subgenotypes but not EV71 using RD cells. The neutralizing titers of NA11F12 ranged from 1:1024 to 1:12288 against A, B1, B2 and C subgenotypes of CA16 and was less than 8 against EV71 strain. In the neonatal mouse model, a single treatment of NA11F12 showed effective protection with a dose- and time-dependent relationship against lethal challenge by CA16 strain (GenBank no. JX481738). At day 1 post-infection, administering more than 0.1 μg/g of NA11F12 could protect 100% newborn mice from mobility and mortality challenged by CA16. With dose of 10 μg/g of NA11F12, a single administration fully protected mice against CA16-associated disease within 4 days post-infection. And there were 80% and 60% mice protected by administering NA11F12 at day 5 post-infection and day 6 post-infection when the control mice had shown clinical symptoms for 1- and 2-day, respectively. Immunohistochemical and histological analysis confirmed that NA11F12 significantly prohibited CA16 VP1 expression in various tissues and prevented CA16-induced necrosis. In conclusion, a CA16-specific MAb NA11F12 with high cross-neutralization activity was identified, which could effectively protect lethal CA16 challenge in mice. It could be a potential therapeutic MAb against CA16 in the future.