Abstract
Contemporaneous Zika virus (ZIKV) strains can cause congenital Zika syndrome (CZS). Current ZIKV clinical laboratory testing strategies are limited and include IgM serology (which may wane 12 weeks after initial exposure) and nucleic acid testing (NAT) of maternal serum, urine, and placenta for (+) strand ZIKV RNA (which is often transient). The objectives of this study were to determine if use of additional molecular tools, such as quantitative PCR and microscopy, would add to the diagnostic value of current standard placental ZIKV testing in cases with maternal endemic exposure and indeterminate testing. ZIKV RNA was quantified from dissected sections of placental villi, chorioamnion sections, and full cross-sections of umbilical cord in all cases examined. Quantitation with high-resolution automated electrophoresis determined relative amounts of precisely verified ZIKV (74-nt amplicons). In order to localize and visualize stable and actively replicating placental ZIKV in situ, labeling of flaviviridae glycoprotein, RNA ISH against both (+) and (−) ZIKV-specific ssRNA strands, and independent histologic examination for significant pathologic changes were employed. We demonstrate that the use of these molecular tools added to the diagnostic value of placental ZIKV testing among suspected cases of congenital Zika syndrome with poorly ascribed maternal endemic exposure.
Highlights
Zika virus (ZIKV) is a mosquito-borne (Aedes genus) arbovirus of the Flaviviridae family
We present four recent cases of gravidae who were at risk for endemic ZIKV infection preconception and/or during pregnancy, but with varying instances of delayed or indeterminate testing using current standard testing
A schematic summary of each case and representative fetal images are provided in Figures 1 and 2, raebsnpoercmtiavleploys.tnIantalFbigrauinrean1d aheaddetimaialegdingtiamreedlienpeictbedy inwFeiegkurse o3.f Kgeeysatantdiopnersdisetpenict tpsostthneatapleriod of residenciemiangiangZfiIKndVinegsnidneclmudice vaernetar,icaunlodmteigmaliynwgiothfaebnsetrnyt cianvtuomthseepUtu.mS.p, epllousciitdiuvme,apnrdomniengenattithvierdmaternal laboratovryenttreisctleinwgit,haonudt opbsetrruticntieonntatptohseilteivveel osfotnheofgorraamphenicoffiMnodnirnog, asn. dAdllifftuessetiwnhgitde empaitctetreadndincoFripguusre 1 was performcOeadnllooinspuhamthcvalolimnluiimccaeelxloalasmsb,wtahintehdimntfuhalnutitpshldeadseupbbii-lccatetsenrtcaimul creorteelornbstoumsbteaaptneondudsayrlmedsaitolennssotdcinoungles,sisuatletoinnltigzwitnhiteghlcaFotDenrgaAel nvaietpnatplrZircoilkevase. d ZIKV nucleic acid testing (NAT)
Summary
Zika virus (ZIKV) is a mosquito-borne (Aedes genus) arbovirus (arthropod-borne virus) of the Flaviviridae family. As the virus spread eastward, Yap Island became endemic in 2007, followed by epidemics in French Polynesia, New Caledonia, the Cook Islands, and Easter Island in 2013 and 2014 [1,2]. By 2014, ZIKV had reached the Americas with the initial outbreaks occurring in the Caribbean and South America and broadening to include vast swathes across the Western Hemisphere as of late 2018 (https://www.cdc.gov/zika/geo/index.html) (accessed on 1 December 2018). The virus is geographically spread as a result of human travel from endemic regions, alongside human-to-human transmission via sexual intercourse, blood transfusions, and via vertical maternal-fetal transmission [2,3,4,5]. No other flavivirus is known to cause disseminated fetal neural malformations in humans, worldwide concern for latent viral disease was raised following several case reports demonstrating persistent ZIKV RNA in the amniotic fluid, placenta, and fetal neural tissue weeks to months after initial maternal infection [3,4]
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