Fig. 5: S glycoprotein-like protrusions were found on microvilli and plasma membrane of infected cells.

a An uninfected goblet cell (GC) next to an infected ciliated cell (CC) that has viral-containing compartments (VC) (endosome (En) and basal bodies (BB) were also visible). The goblet cell is identifiable by the mucin-containing secretory granules (Mu) and the junction between the two cells false coloured with a red line. When looking at the microvilli from the goblet cell shown in (a) and at higher magnification (b), the membrane is smooth. Conversely, the plasma membrane of the microvilli of the infected ciliated cell (a) and at higher magnification (c), is not smooth and has protrusions (blue arrowheads). d The microvilli of a non-infected ciliated cell are smooth. e High magnification images of the boxed regions (f, g) show infected cultured human airway epithelial cells where viral particles can be seen attached to the cell surface. The viral S glycoprotein (red arrowheads) has a similar profile to the cell surface protrusions (blue arrowheads). h–j Cells acquired from a nasal brushing of an infected patient show the presence of viral particles (red arrowheads). I, j At higher magnification protrusions are seen at the cell surface and on microvilli (blue arrowheads). Scale bars (a) 400 nm, (b–g) 100 nm, and (h–j) 200 nm.