Fig. 2.

Detection of SARS-CoV-2 proteins in nasopharyngeal swab cell preparations. A Hematoxylin and eosin stain demonstrates the large, flat pink squamous cells (arrows) and the more elongate grey glandular cells (box) (Panel A). An intense signal for covid-19 spike protein was seen in the glandular cells and not the squamous cells (panel B; signal brown due to DAB). Cilia were rarely seen in infected cells (ciliocytophthoria). The strong signal indicates high viral copy number that facilitates immunohistochemistry detection. Co-expression for epithelial membrane antigen (panel C, signal red) and spike protein (panel D, signal green) documented that signal was in glandular cells (panel E, merged signal yellow). Co-expression of spike and envelope proteins of SARS-CoV-2 (panel F, RGB image) documented localization of each protein to glandular cells with negative squamous cells two weeks after full recovery (panel G, signal yellow). No signal was seen in oral swabs of positive cases (panel H). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)