Preferential apical infection of intestinal cell monolayers by SARS-CoV-2 is associated with damage to cellular barrier integrity: Implications for the physiopathology of COVID-19
SARS-CoV-2 can infect different organs, including the intestine. In Caco-2 intestinal cell line, SARS-CoV-2 modulates the ACE2 receptor expression and affects the expression of molecules involved in intercellular junctions. To further explore the possibility that the intestinal epithelium serves as an alternative infection route for SARS-CoV-2, we used a model of polarised intestinal cell monolayers grown on the polycarbonate membrane of Transwell inserts, inoculated with the virus either in the upper or lower chamber of culture. In both polarised Caco-2 cell monolayers and co-culture Caco-2/HT29 cell monolayer, apical SARS-CoV-2 inoculation was found to be much more effective in establishing infection than basolateral inoculation. In addition, apical SARS-CoV-2 infection triggers monolayer degeneration, as shown by histological examination, measurement of trans-epithelial electronic resistance, and cell adhesion molecule expression. During this process, the infectious viruses reach the lower chamber, suggesting either a transcytosis mechanism from the apical side to the basolateral side of cells, a paracellular trafficking of the virus after damage to intercellular junctions in the epithelial barrier, or both. Taken together, these data highlight a preferential tropism of SARS-CoV-2 for the apical side of the human intestinal tract and suggests that infection via the intestinal lumen leads to a systemic infection.