West Nile/Zika Virus Chimeras for Inactivated Zika Vaccine and Diagnostic Assay Development

Zika virus (ZIKV) is a flavivirus primarily transmitted by infected Aedes mosquitoes. Infection with ZIKV during pregnancy can affect the fetus causing microcephaly, neurological complications, and other birth defects. Adults are also at risk of developing Guillain-Barre syndrome and other neurological disorders from ZIKV infection. In response to the 2015-2016 Zika outbreak, CDC researchers developed new Zika virus chimeras that can be used for inactivated Zika vaccine candidates and faster Zika antibody (Ab) neutralization assay testing. CDC scientists successfully engineered cDNA clones for the chimeric constructs based on a West Nile (WN) Virus NY99 genetic backbone and recovered three fast-growth chimeric WN/Zika viruses. These chimeric viruses replicate significantly faster and produce a more uniform virus population than the parental wild-type Zika virus from cell culture. Future research will include inactivated vaccine efficacy testing in mouse models. Preliminary data shows that the WN/Zika chimeras reduce the gold standard plaque neutralization reduction Ab assay testing time from 6 to 4 days. The chimeric constructs also include reporter genes for diagnostic use with automated plate readers. The reporter chimeric virus permits direct live-image based cell cytometry analysis for an easy, fast, and high throughput micro-neutralization Ab assay within 24 hours without any cell overlay, cell detaching, cell fixation, or staining process.