An arthropod-borne virus, Zika virus (ZIKV), has recently emerged as a major human pathogen. Associated with complications during perinatal development and Guillain-Barré syndrome in adults, ZIKV raises new challenges for understanding the molecular determinants of flavivirus pathogenesis. This underscores the necessity for the development of a reverse genetic system based on an epidemic ZIKV strain. Here, we describe the generation and characterization in cell cultures of an infectious cDNA clone of ZIKV isolated from the 2015 epidemic in Brazil. The cDNA-derived ZIKV replicated efficiently in a variety of cell lines, including those of both neuronal and placental origin. We observed that the growth of cDNA-derived virus was attenuated compared to the growth of the parental isolate in most cell lines, which correlates with substantial differences in sequence heterogeneity between these viruses that were determined by deep-sequencing analysis. Our findings support the role of genetic diversity in maintaining the replicative fitness of viral populations under changing conditions. Moreover, these results indicate that caution should be exercised when interpreting the results of reverse-genetics experiments in attempts to accurately predict the biology of natural viruses. Finally, a Vero cell-adapted cDNA clone of ZIKV was generated that can be used as a convenient platform for studies aimed at the development of ZIKV vaccines and therapeutics.

No abstract

An improved quantitative multiplex one-step RT-PCR (qmosRT-PCR) for simultaneous identification and quantitation of all three serotypes of poliovirus is described. It is based on using serotype-specific primers and fluorescent TaqMan oligonucleotide probes. The assay can be used for high-throughput screening of samples for the presence of poliovirus, poliovirus surveillance and for evaluation of virus shedding by vaccine recipients in clinical trials to assess mucosal immunity. It could replace conventional methods based on cell culture virus isolation followed by serotyping. The assay takes only few hours, and was found to be simple, specific, sensitive and has large quantitative linearity range. In addition, the method could be used as readout in PCR-based poliovirus titration and neutralization assays.