Fig. 4.

U87.ACE2⁺ cells actively replicate wild-type SARS-CoV-2. A). U87 and U87.ACE2⁺ cells were exposed to different doses of SARS-CoV-2 (Wuhan strain). Samples were collected at 16 h post infection and 5,000–6,000 cells were analyzed by flow cytometry. Cells were stained for intracellular nucleoprotein (N) expression. Dot plots show N expression in noninfected (lower left quadrant) and infected (lower right quadrant) cells. The numbers in each quadrant refer to the distribution of the cells (i.e., percentage of total cell population). The dot plot in grey (left panel) represents the noninfected cell control. B). U87.ACE2⁺ cells were exposed to SARS-CoV-2 (20A.EU2 strain; MOI 5) for 1 h (indicated by grey boxed V). Next, cells were washed extensively to remove unbound virus and were given fresh medium. Supernatant was collected at the indicated time points and a duplex RT-qPCR was performed to quantify the copy numbers of the N and E genes. The dotted horizontal line refers to the background signal. For each sample, the average (mean ± SD) of two technical replicates is given (n = 2), plotted on a log₁₀ scale.