Serum-derived IgG from coxsackievirus A6-infected patients can enhance the infection of peripheral blood mononuclear cells with coxsackievirus A6.

Coxsackievirus A6 (CV-A6) has recently emerged as an enterovirus causing Hand Foot and Mouth Disease with severe complications. The pathogenic mechanisms of CV-A6- associated Hand foot and Mouth disease are largely unknown. In this study, it was investigated whether serum and IgG from patients with CV-A6 infection can enhance the infection of PBMC with the virus. Serum samples were obtained from five children with CV-A6 infection confirmed by RT-PCR and seven controls. IgG was isolated from serum by using affinity chromatography columns. CV-A6 was incubated with serum or IgG from controls and patients then the mixtures were added to PBMC cultures. The levels of IFNα in supernatants were measured by ELISA, and the levels of intracellular viral RNA were measured by RT-qPCR. It has been observed that there is an anti-CV-A6 enhancing activity in serum and serum-derived immunoglobulin G of children with CV-A6 infection but not in those of uninfected controls. Whether this activity has implications in the pathogenesis of CV-A6 associated diseases should be investigated.