Figure 1

Figure 1

Intranasal delivery of SARS-CoV-2 S RDB protein causes severe histological damage in the adult zebrafish OO that recovers after 2 weeks. H&E stains of zebrafish OO paraffin sections. (A) Control vehicle treated OO. (B) 3 h; (C) 1 d; (D) 3 d; (E) 5 d; (F) 2 w post intranasal delivery of SARS-CoV-2 S RDB protein (r-Spike) or controls (Poly(I:C) and an off-target His-tagged recombinant protein). Images are representative of n=10 sections per animal and N=3-5 fish per experimental group. Asterisk denotes edemic spaces in the olfactory lamellae, mostly in the lamina propria. He: hemorrhages. Arrow heads: apical loss of olfactory sensory neurons. Black Arrow: Necrotic lamella. (G) Immunofluorescence image of an AB zebrafish OO cryosection from an adult OMP:lynRFP animal 15 min after I.N SARS-CoV-2 S RBD administration stained with a rabbit IgG isotype control as primary antibody. Scale: 20μm. (H) Immunofluorescence image of an OMP:lynRFP zebrafish OO stained with anti-His antibody (green) 15 min post I.N. delivery of recombinant His-tagged SARS-CoV-2 S RBD. (I) Immunofluorescence of an AB zebrafish OO stained with anti-His antibody (red) 15 min post I.N. delivery of SARS-CoV-2 S RBD shows puncta of anti-His staining when zoomed in on non-sensory epithelium; Scale = 5μm. Ax: OSN axon bundles; NC: nasal cavity; LP: lamina propria. Scale: 20μm. Cell nuclei are stained with DAPI (blue). (J) Mean width of the olfactory lamina propria in each treatment group. (K) Mean percent of olfactory lamellar surface covered by healthy cilia in each treatment group. (L) Expression of ace2 in OO and OB tissue of untreated adult AB zebrafish (N =3) as measured by RT-qPCR. Expression levels were normalized to rps11 as the house-keeping gene. Quantifications in J&K were performed in ImageJ; error bars represent S.E.M. J&K statistics were done by one-way ANOVA followed by a Tukey’s post hoc comparison. * P-value<0.05, ** P-value<0.01, **** P-value<0.0001.