Development and Application of a Reverse Genetics System for Zika Virus

Zika virus (ZIKV) has emerged in many regions of the world, with infection outcomes spanning from no apparent illness to crippling nervous system disease. ZIKV and its close relatives, West Nile virus, Japanese encephalitis virus, dengue virus, and yellow fever virus are primarily transmitted by mosquitoes. Three ZIKVs were selected: MR-766 (Uganda, 1947), P6-740 (Malaysia, 1966), and PRVABC-59 (Puerto Rico, 2015), whose place of origin and time of isolation differ substantially. Stable, complementary DNA (cDNA) copies of the three ZIKV RNA genomes were cloned to examine the significance of viral and host genetic variations in directing ZIKV infection outcomes. Using a new toolbox for ZIKV genome engineering and protein analysis, combined with various cell culture and mouse infection model systems, the following were determined: (1) Genome-wide landscape of viral gene products and their related species, with several immuno-reactive gene products identified in the case of all three cloned ZIKVs. (2) Viral replicability in cultured cells, varied significantly depending on the virus strain and host cell type, with one cow cell line being resistant to ZIKV infection. (3) Virus induced neurological disease in mice, differed dramatically depending on the virus dose and strain, mouse age and strain, route of infection, and presence or absence of immune system components. Overall, the findings demonstrate the impact of the viral and host genetic backgrounds on the ability of ZIKV to replicate and cause disease. The ZIKV strain-specific characterizations and molecular instruments described will provide multiple avenues for developing and testing medical countermeasures