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. 2024 Jan 30;15:889. doi: 10.1038/s41467-024-45075-8

Fig. 1. Omicron BA.1 exhibits superior replicative fitness relative to early SARS-CoV-2 and Delta in primary human nasal epithelial cells.

Fig. 1

A Primary human nasal epithelial cells (pooled from three human donors) were cultured as undifferentiated, submerged monolayers and challenged with SARS-CoV-2. Cells were fixed and permeabilized for confocal immunofluorescence microscopy. Acetylated tubulin levels were determined by anti-AcTub immunofluorescence, ACE2 levels were determined by anti-ACE2 immunofluorescence, and DAPI was used to stain nuclei. 3D reconstructions of xy and yz fields are shown. Scale bars = 10 µm. Cartoon made with Biorender.com. B Primary human nasal epithelial cells (pooled from three donors) or C human small airway (lung) epithelial cells (pooled from three donors) were challenged with replication-competent SARS-CoV-2 WA1 or Omicron BA.1 at an MOI of 0.05. Total cellular RNA was extracted, and viral ORF1a was quantified by RT-qPCR at the indicated time points. Relative viral RNA abundance compared to actin was determined by the 2(−ΔΔCT) method. ORF1a abundance of WA1 at 24 h post inoculation was set to 1. D Virus replication in primary human nasal epithelial cells was measured by detecting ORF1a levels with RT-qPCR at 24 h post inoculation with WA1, Delta, or BA.1 at an MOI of 0.05. E As in D, except that primary human nasal epithelial cells were treated with remdesivir (10 µM) or DMSO prior to and during inoculation with WA1, Delta, or BA.1. ORF1 abundance of each virus treated with DMSO was set to 1. All results are represented as means plus standard error from three independent infections (symbols represent biological replicates). Statistically significant differences (*P < 0.05) between the indicated condition and the corresponding data point of WA.1 or DMSO were determined by the student’s unpaired two-sided t test (exact p values from left to right: B 0.0002, 0.0001, 0.0001; C 0.0434; E 0.0001, 0.0017, 0.0002) or one-way ANOVA adjusted for multiple comparisons (D 0.96, 0.004). Refer to Supporting Dataset 1 for non-normalized data. Source data are provided as a Source Data file.