TJP1 and COVID-19: We further examined the intestinal barrier, and found zona occludens 1 (ZO-1) expression in intestine was decreased in spike RBD-Fc stimulated mice compared with control (Figure 1D), which was consistent with the increased level of LPS, a plasma biomarker of intestinal barrier injury, in severe COVID-19 patients compared with non-severe ones (Figure 1E, p < 0.01).