Rescue of Replication-Competent ZIKV Hidden in Placenta-Derived Mesenchymal Cells Long After the Resolution of the Infection

Abstract

The Zika virus (ZIKV) genome, its negative-strand viral proteins, and virus-like particles were detected in placenta-derived mesenchymal cells (MSCs), indicating that ZIKV persists after virus clearance from maternal blood and can be rescued by in vitro cultivation. We report for the first time the presence of replication-competent ZIKV in MSCs from an asymptomatic woman who acquired infection during pregnancy.

Keywords: Zika virus; mesenchymal cells; placenta; vertical transmission; viral reservoir.

Figure 1.

Characterization of Zika virus (ZIKV) infection of decidua-derived mesenchymal cells (dd-MSCs). A, Morphology of dd-MSCs (P0, 21 days post expansion (DPE)) observed by light microscope. Scale bar = 500 μm. B, ZIKV total-RNA and neg-RNA quantification in dd-MSCs cells and culture supernatants sampled at different days of P0 culture. C, Immunolocalization by confocal microscopy of the ZIKV glycoprotein, detected by anti-pan-flavi-specific IgG antibody (ZIKV, green) on dd-MSCs (day 3 of P0). Left panels: nuclear staining; middle panels: ZIKV-specific staining; right panels: merged images. The 2 higher rows show different microscopy fields; the lower row shows a higher magnification of the central row pictures. A dotted immunolabeling can be observed in the cytoplasm of positive cells. Scale bar = 100 μm. D, Ultrastructural analysis of dd-MSCs (day 3 of P0), assessed by transmission electron microscopy. The cultured cells show virus-like structures measuring approximately 40–50 nm in diameter in cytoplasmic vesicles close to the rough endoplasmic reticulum (arrows). The morphologic characteristics of the virus-like structures are consistent with viral particles of the Flaviviridae family. Scale bars = 200 μm. Abbreviations: ER, endoplasmic reticulum; M, mitochondrion.