Characterization of Coxsackievirus A6 Strains Isolated From Children With Hand, Foot, and Mouth Disease

Abstract

Coxsackievirus A6 (CVA6) is a key pathogen causing hand, foot and mouth disease (HFMD). However, there are currently no specific antiviral drugs or vaccines for treating infections caused by CVA6. In this study, human rhabdomyosarcoma (RD), African green monkey kidney (Vero), and human embryonic lung diploid fibroblast (KMB17) cells were used to isolate CVA6 from 327 anal swab and fecal samples obtained during HFMD monitoring between 2009 and 2017. The VP1 genes of the isolates were sequenced and genotyped, and the biological characteristics of the representative CVA6 strains were analyzed. A total of 37 CVA6 strains of the D3 gene subtypes were isolated from RD cells, all of which belonged to the epidemic strains in mainland China. Using the adaptive culture method, 10 KMB17 cell-adapted strains were obtained; however, no Vero cell-adapted strains were acquired. Among the KMB17 cell-adapted strains, only KYN-A1205 caused disease or partial death in suckling mice, and its virulence was stronger than its RD cell-adapted strain. The pathogenic KYN-A1205 strain caused strong tropism to the muscle tissue and led to pathological changes, including muscle necrosis and nuclear fragmentation in the forelimb and hindlimb. Sequence analysis demonstrated that the KYN-A1205 strain exhibited multiple amino acid mutations after KMB17 cell adaptation. Moreover, it showed strong pathogenicity, good immunogenicity and genetic stability, and could be used as an experimental CVA6 vaccine candidate.

Clinical characteristics of 68 children with atypical hand, foot, and mouth disease caused by coxsackievirus A6: a single-center retrospective analysis

“…Similar to the other members of the Picornaviridae family, CV-A6 has a single-stranded, positive-sense RNA genome. It can be segregated into 4 genotypes, designated as A, B, C, and D, and further subdivided into the B1 and B2, C1 and C2, and D1, D2, and D3 subgenotypes (15). In recent years, the D3 and E2 strains have become prevalent in China, France, Spain, Japan, and other countries to varying degrees (16,17).…”

A mouse-adapted CVA6 strain exhibits neurotropism and triggers systemic manifestations in a novel murine model

“…Our results suggest that CVA6 exhibits a strong muscle tropism, which may be one of the direct causes of paralysis and inability to obtain breast milk in newborn mice, thus accelerating their death. Previous studies confirmed that skeletal muscle was the most important site for CVA6 virus replication [ 20 , 28 , 39 , 47 ]. Other studies have suggested that skeletal muscle is the leading site for the replication of Enterovirus infection, providing the source of virus for CNS infection [ 48 , 49 ].…”

“…Therefore, establishing animal models with typical clinical symptoms is one of the important steps to understanding the pathogenesis of CVA6 infection and the development of vaccines, therapeutic antibodies, and antiviral drugs. Recently, several animal models [ 20 , 27 , 28 , 39 ] have been reported to evaluate vaccines and antiviral drugs and study the pathogenesis. However, those CVA6 animal models differ from our model in several important respects, namely the dose and route of inoculation, the strain of laboratory mice used, and, critically, the virus strain used.…”

Surveillance, epidemiology, and impact of the coronavirus disease 2019 interventions on the incidence of enterovirus infections in Nanchang, China, 2010–2022

“…Clinical manifestations of HFMD include mild to severe rash, herpangina, pulmonary edema, circulatory disturbances, meningitis, aseptic encephalitis, and even death ( Wang et al, 1999 ; Solomon et al, 2010 ). Since 2012, outbreaks associated with CVA6 have been frequently reported in Europe, Japan and some developed regions of China ( Feng et al, 2015 ; Kanbayashi et al, 2017 ; Kamau et al, 2021 ; Liu et al, 2021 ; Tomba Ngangas et al, 2022 ). From then on, CVA6 has been gradually predominant in most areas of China since 2013 ( He et al, 2021 ; Liu et al, 2021 ).…”

“…Since 2012, outbreaks associated with CVA6 have been frequently reported in Europe, Japan and some developed regions of China ( Feng et al, 2015 ; Kanbayashi et al, 2017 ; Kamau et al, 2021 ; Liu et al, 2021 ; Tomba Ngangas et al, 2022 ). From then on, CVA6 has been gradually predominant in most areas of China since 2013 ( He et al, 2021 ; Liu et al, 2021 ). Our former study found CVA6 increasingly predominated in local HFMD cases, and EV-A71 was no longer detected from HFMD surveillance after 2 years EV-A71 vaccine promotion and implementation ( He et al, 2021 ).…”