Production and characterization of Zika virus RNA reference reagents as a response to a public health emergency.

BACKGROUNDThe emergence of Zika virus (ZIKV) in 2015 to 2016 created a global public health crisis and an urgent need for accurate detection assays. Nucleic acid testing (NAT) is the most specific and sensitive technology for early detection of ZIKV. Various NAT protocols have been created, but until recently, assessment of assay performance and comparative studies were hampered by the lack of available standards and reference reagents. STUDY DESIGN AND METHODSThe Center for Biologics Evaluation and Research/Food and Drug Administration responded to this crisis with the generation of two ZIKV-RNA reference reagents (ZIKV-RRs) for use in the development, validation, and assessment of performance of ZIKV-NAT assays. These reagents were produced from heat-inactivated (HI) ZIKV culture supernatant stock from two strains (PRVABC59 and FSS13025) diluted in dialyzed, defibrinated human plasma and lyophilized for evaluation in collaborative studies. The liquid, HI stock had been shared with the Paul-Ehrlich-Institute (Germany) and were included in the collaborative validation studies for the World Health Organization International Standard for ZIKV (WHO ZIKV IS). RESULTSNAT-detectable units (NDUs)/mL were determined in a collaborative study that led to the assignment of 5.77 log NDUs/mL for PRVABC59 and 5.54 log NDUs/mL for FSS13025 as the final concentrations of the FDA ZIKV-RRs. CONCLUSIONWe have established well-characterized reference reagents for ZIKV to facilitate evaluation of existing NAT assays and development of novel ZIKV assays which are correlated to that of the First WHO ZIKV IS. Vials of the ZIKV-RRs are available to qualified organizations upon request.