Evolution, recombination and geographic spreading of global Coxsackievirus A6.

BACKGROUND: The increasing incidence of hand, foot, and mouth disease (HFMD) associated with Coxsackievirus A6 (CVA6) has become a very significant public health problem. The aim of this study is to investigate the recombination, geographic transmission, and evolutionary characteristics of the global CVA6. METHODS: From 2019 to 2022, 73 full-length CVA6 sequences were obtained from HFMD patients in China and analyzed in combination with 1032 published whole genome sequences. Based on this dataset, the phylogenetic features, recombinant diversity, Bayesian phylodynamic characteristics, and key amino acid variations in CVA6 were analyzed. RESULTS: The four genotypes of CVA6, A, D, E, and F, are divided into 24 recombinant forms (RFs, RF-A - RF-X) based on differences in the P3 coding region. The eastern China region plays a key role in the dissemination of CVA6 in China. VP1-137 and VP1-138 are located in the DE loop on the surface of the CVA6 VP1 protein, with the former being a highly variable site and the latter having more non-synonymous substitutions. CONCLUSIONS: Based on whole genome sequences, this study contributes to the CVA6 monitoring, early warning, and the pathogenic mechanism by studying recombination diversity, geographical transmission characteristics, and the variation of important amino acid sites.

Epidemiology of hand, foot and mouth disease and genomic surveillance of coxsackievirus A10 circulating in Zhejiang Province, China during 2017 to 2022.

BACKGROUND: Coxsackievirus A10 (CA10) is one of the etiological agents associated with hand, foot and mouth disease (HFMD). OBJECTIVES: We aimed to perform a retrospective analysis of the molecular epidemiological characteristics and genetic features of HFMD associated with CA10 infections in Zhejiang Province from 2017 to 2022. STUDY DESIGN: Epidemiologic features were summarized. Throat swab specimens were collected and tested. The VP1 regions were sequenced for genotyping. CA10 positive samples were isolated. Whole genomes of CA10 isolations were sequenced. Nucleotide and amino acid changes were characterized. Phylogenetic trees were constructed. RESULTS: The number of HFMD cases fluctuated from 2017 to 2022. Children aged below 3 years accounted for the majority (66.29%) and boys were more frequently affected than girls. Cases peaked in June. The positivity rate of HEV was 62.69%. A total of 90 strains of CA10 were isolated and 53 genomes were obtained. All CA10 in this study could be assigned to two genogroups, C (C2) and F (F1 and F3). CONCLUSION: The clinical manifestations of HFMD associated with HEV are complex and diverse. CA10 infection may be emerging as a new and major cause of HFMD because an upward trend was observed in the proportion of CA10 cases after the use of EV71 vaccines. Different genogroups of CA10 had different geographic distribution patterns. Surveillance should be strengthened and further comprehensive studies should be continued to provide a scientific basis for HFMD prevention and control.

Muscle destruction caused by coxsackievirus A10 in gerbils: Construction of a novel animal model for antiviral evaluation.

The morbidity and mortality of coxsackievirus A10 (CVA10)-associated hand, foot, and mouth disease (HFMD) have been increasing in recent years, while few studies on the vaccine and animal model of CVA10 have been reported. Here, we first established a CVA10-infected gerbil model and employed it to evaluate the immunoprotective effect of an inactivated CVA10 vaccine. The results showed that gerbils up to the age of 14 days were fully susceptible to CVA10, and all died within five days post-infection by intraperitoneal inoculation. Lethargy, wasting, hind-limb paralysis, and even death could be observed in the CVA10-infected gerbils. Pathological examination suggested that CVA10 has a strong tropism toward muscle tissue, and muscle bundle fracture and muscular fibers necrosis were observed in the limb muscles. Additionally, active immunization results showed that gerbils immunized with the inactivated CVA10 vaccine were 100 % protected from lethal CVA10 challenge. The antisera from vaccinated gerbils also showed high neutralizing titers against CVA10. Based on these results, the CVA10-infected gerbil model was a suitable tool for analyzing the pathogenesis of CVA10 and assessing the protective efficacy of CVA10 candidate vaccines.

[Isolation and sequencing of VP1 region of enterovirus 71 strains in Zhejiang, China].

OBJECTIVE: To study the gene characterization of enterovirus 71 (EV71) virus strains isolated from clinical specimens of children with hand-foot-and-mouth disease (HFMD) in Zhejiang province. METHODS: Virus were isolated from clinical samples including stool, throat swab and vesicle from patients with HFMD. The EV71 isolates were identified by microneutralization assay and reverse transcriptase PCR (RT-PCR) with specific primer pair for VP1 genes of EV71. Complete VP1 gene sequences (891 nucleotides) for recent 6 EV71 isolates were determined and compared with that of A, B, C genotype reference EV71 strains and 11 EV71 China isolates available from GeneBank by homogeneity and phylogenetic tree analyses. RESULTS: 9 strains of EV were isolated from 14 clinical specimens. Data from microneutralization and RT-PCR results indicated that all the strains belong to EV71. The nucleotide and amino acid homogeneity of these 6 Zhejiang strains with the representative isolates of A and B genotypes were 82.9%-85.5% and 94.9%-98.0% respectively; with the representative isolates of C were 89.2%-94.1% and 97.0%-99.0% respectively. There were 91.0%-92.2%, 90.2%-90.3%, 89.2%-89.5%, 96.7%-96.9% nucleotide, homology with representative strains of C1, C2, C3,C4 subgenotypes of EV71. The nucleotide homogeneity of these 6 EV71 isolated strains with 9 previously isolated Chinese strains appeared to be 93.8%-97.1%. These 6 EV71 isolated strains were within genotype C subgenogroup C4 in the phylogenetic tree. CONCLUSION: The recently identified EV71 isolates in Zhejiang province belonged to subgenogroup C4.