Replication of ZIKV-Nluc in cell culture. (A) IFA of E protein expression in Vero cells infected with the purified ZIKV-Nluc virus at an MOI of 0.05. (B) Nluc activities of infected Vero lysates by the purified ZIKV-Nluc virus at different times post infection at an MOI of 0.001, 0.01, 0.1, and 1, respectively. (C) Growth curves of the purified ZIKV-Nluc virus determined by immunostaining plaque assay at an MOI of 0.01. (D) Linear correlation between viral titres and Nluc signal values of the purified ZIKV-Nluc virus in vitro. Data represent the mean ± SD analysed by Student's t-test (two tailed) (*, P < 0.05; **, P < 0.01; ***, P < 0.001).