Figure 3. Taste Bud and Sensory Fiber Architecture Are Disrupted in Postacute Sequelae of Coronavirus Disease 2019 That Can Resolve Spontaneously.

We followed a 37-year-old female (F) with multiple biopsies from 17 weeks postinfection through to full recovery by 67 weeks using hematoxylin and eosin and immunofluorescent (IF) staining on adjacent fungiform papillae for the taste receptor cells marker cytokeratin 8 (CK8, red) present on all taste cell receptors; the type II taste cell receptor marker, phospholipase C beta-2 (PLCβ2, yellow); the taste cell receptor subtype that also has angiotensin-converting enzyme 2 (Panels A and B); and the nerve fiber marker neurofilament heavy (NF-H, green) (Panels D and E). Panel C schema shows taste cell receptor cell types and their afferent nerve fibers. Taste buds are composed of discreet clusters of taste cell receptors that include type I, II (the most numerous cell type in human fungiform papillae), and III, as well as a few stem cells that differentiate into mature taste cell receptors. The white dotted lines (A1, B1, D1, and E1) outline taste buds, and grey dotted lines (D3, E1, and E3) delineate the epithelial layer from the lamina propria. Nerve fibers run between taste cell receptors in taste buds, converging in the plexus beneath the taste bud and, from there, relay tastant information to the brain. At 17 weeks, a solitary disordered taste bud in 1/8 fungiform papillae was present, and it contained just one type II taste cell receptor (Panel A). By 67 weeks, fungiform papillae contains normal-appearing taste buds and type II taste cell receptors, normal orientation of the basal cell layer (Panel B), and nerve fibers that were disrupted and lacking in the taste bud at 17 weeks (Panel D) were now reinnervating the taste buds as well as the fungiform papillae lamina propria (Panel E). Scale bars indicate 50 μm. PASC denotes postacute sequelae of coronavirus disease 2019.