Biological characteristics of coxsackievirus A6 clinical isolates

Abstract

Objective To analyze the biological characteristics of clinical isolates of coxsackievirus A6 (CVA6), a pathogen of hand, foot and mouth disease (HFMD), and to provide reference for vaccine development. Methods CVA6 strains were isolated from 21 stool and throat swab specimens of patients with HFMD in Yunnan Province and then identified. Their growth characteristics, plaque morphology and virulence to suckling mice were analyzed. Results Five CVA6 strains, named CVA6-129, CVA6-113, CVA6-57, CVA6-94 and CVA6-162, were isolated and all belonged to D3 subtype. Only the CVA6-129 strain could proliferate rapidly in Vero and KMB17 cells and the proliferation peaked 30 h after inoculation. The infectious titer of the CVA6-129 strain was 7.54 lgCCID50 (50% cell culture infective dose)/ml in KMB17 cells. Different morphologies of plaques were formed by the CVA6-129 strain in Vero and KMB17 cells at the same time points, which were small and round with clear edges in Vero cells, and large and irregular with blurry edges in KMB17 cells. Suckling mice were susceptible to CVA6 via intramuscular and intraperitoneal injection. The most common symptoms in infected suckling mice were reduced mobility, hind limb paralysis and quadriplegia. CVA6 infection could result in death in severe cases. Conclusions This study isolated five CVA6 strains from a number of clinical samples of suspected HFMD cases, of which the CVA6-129 strain showed potential as a vaccine candidate. Key words: Coxsackievirus A6 (CVA6); Hand, foot and mouth disease (HFMD); Vaccine; Biological characteristics