Genetic characteristics of CV-A12 VP1 region and clinical manifestations of CV-A12-associated severe hand, foot and mouth disease in Qingdao

Abstract

Objective To investigate the molecular characteristics of coxsackievirus A12 (CV-A12) and to understand the clinical manifestations of severe hand, foot and mouth disease (HFMD) caused by CV-A12 in Qingdao. Methods Throat swabs of HFMD, herpangina and influenza-like cases from 2011 to 2016 were detected for enteroviruses (EVs) in Qingdao. Human rhabdomyosarcoma (RD) and human laryngeal carcinoma (Hep-2) cells were used for virus proliferation and CV-A12 strains were identified through a semi-nest RT-PCR. The full-length of VP1 gene of CV-A12 strains was sequenced and phylogenetically analyzed using MEGA7.0 software package. Clinical data of severe HFMD cases positive for CV-A12 were collected and analyzed. Results CV-A12-positive HFMD, herpangina and influenza-like cases accounted for 0.3%(18/6 798), 1.2%(2/169) and 0.1%(1/676) in Qingdao, respectively. Most of the HFMD caused by CV-A12 in children were mild before 2013 (84.6%, 11/13), while hospitalized severe cases with neurological symptoms (100%, 5/5) became more common after 2013. Phylogenetic analysis of the VP1 region revealed that CV-A12 strains worldwide could be divided into two genotypes, A and B. All of the CV-A12 strains successfully sequenced in Qingdao from 2011 to 2016 belonged to genotype B, and 88.9% (16/18) of them belonged to subgenotype B2. All hospitalized severe cases of CV-A12-caused HFMD after 2013 were associated with strains in branch B2b of subgenotype B2. Conclusion CV-A12 was one of the pathogens causing HFMD, herpangina and influenza-like illness in children in Qingdao. Strains of genotype B2 were the predominant CV-A12 strains circulating in Qingdao in recent years. CV-A12-caused HFMD might complicated by nervous system damage. Key words: Coxsackievirus A12; Severe hand, foot and mouth disease; Phylogenetic analysis