Development of standard methods for Zika virus propagation, titration, and purification

The emergence of Zika virus (ZIKV) infection has stimulated several research groups to study and collaborate to understand virus biology and pathogenesis. These efforts may assist with the development of antiviral drugs, vaccines and diagnostic tests, as well as to promote advancements in public health policies. Here, we aim to develop standard protocols for propagation, titration, and purification of ZIKV strains, by systematically testing different cell types, kinetics, multiplicity of infection and centrifugation protocols. ZIKV produces a productive infection in human, non-human primate, and rodents-derived cell lines, with different efficacies. The highest yield of ZIKV-AFR and ZIKV-BR infectious progeny was obtained at 7days post infection in C6/36 cells (7×10⁷ and 2×10⁸ PFU/ml, respectively). However, high titers of ZIKV-AFR could be obtained at earlier time points in Vero cells (2.5×10⁷PFU/ml at 72hpi), whereas ZIKV-BR titers reached 10⁸ PFU/ml at 4dpi in C6/36 cells. High yield of purified virus was obtained by purification through a discontinuous sucrose gradient. This optimized procedure will certainly contribute to future studies of virus structure and vaccine development. Beyond the achievement of efficient virus propagation, the normalization of these protocols will also allow different laboratories around the world to better compare and discuss data regarding different features of ZIKV biology and disease, contributing to more efficient collaborations and progression in ZIKV research.