Fig. 3. The sfRNA facilitates ZIKV replication in hCOs and viral infection of neural progenitors.

(A) Morphology of hCOs infected with WT and sfRNA-deficient ZIKV at DIV15. Scale bars, 500 μm. (B) Viral titers in culture supernatants from hCOs infected with WT and sfRNA-deficient ZIKV are shown in (A). The 14- to 15-day-old organoids were infected with 10⁴ FFU of ZIKV. Viral titers were determined by a foci-forming assay. Values are the means from three independent organoid differentiation experiments, each containing five to six organoids per group ±SD. Statistical analyses are shown in table S7. (C and D) Infection efficiency of WT and sfRNA-deficient ZIKV in hCOs. (E and F) Localization of ZIKV replication in cells expressing markers of neural progenitors (Sox2) and mature neurons (NeuN). Cerebral organoids at DIV15 and DIV30 were infected with WT or xrRNA2′ ZIKV and sectioned at 3 dpi. The images in (C) and (E) are representative from three independent experiments (independent organoid differentiation) that all showed similar results. Mann-Whitney U tests were used in (D) and (F). All tests are two-sided.