A surrogate assay for measuring Coxsackievirus A6 neutralizing antibodies.

Coxsackievirus A6 (CV-A6) is one of pathogens causing hand, foot and mouth disease (HFMD) and becomes a new challenge to HFMD control. In this study, we first built a single-round pseudovirus infection system for CV-A6, and then developed a pseudovirus luciferase assay (PVLA) for anti-CV-A6 neutralizing antibody (NtAb) quantification. Since cytopahtic effect (CPE) is considered as the gold standard test for anti-enterovirus NtAb detection, a comparison study has been performed using 318 clinical serum samples, as measured both by PVLA and CPE. The sensitivity and specificity of PVLA was 94.9% (95% CI between 90.8-97.5%) and 92.7% (95% CI between 86.6-96.6%), respectively. Statistical analysis revealed that PVLA and CPE were highly correlated (spearman r = 0.931, P < 0.0001) and in good agreement (94.0%, 95% CI between 90.8-96.4%), showing that PVLA could be used as a surrogate assay for anti-CV-A6 NtAb detection and served as a valuable tool for CV-A6 vaccine evaluation and CV-A6 epidemiological surveillance.