Fig. 4: A PASC mouse model.

a Schematic showing time points used to analyse long-term SARS-CoV-2 driven disease (PASC). Mice were infected intranasally with SARS-CoV-2 P21 and euthanised between 1 and 3 months post-infection (mpi). b–m 9-14 week-old mice were challenged intranasally with either mock (DMEM only) or P21 and monitored daily for b percent weight change relative to initial weight and c percent of animals reaching humane endpoint requiring euthanasia (results are representative of 6 independent experiments; n_mock = 11, n_pasc = 10 animals per group, mean ± SD). Organs were collected for: d Haematoxylin and eosin (H&E) and immunohistochemistry (IHC) staining of fixed lungs. Markers used for each cell type are indicated in brackets and images are representative from 5 animals per group. Scale bar (top) = 5 mm and (bottom) = 100 µm. e Blinded scoring of H&E-stained lung sections was performed. The lung was assessed for the presence of inflammatory foci and haemorrhage, with pathology scored on a scale from 0 to 5. A score of 0 indicated no detectable pathology, while a score of 5 represented extensive pathology; n_mock = 8, n_1mpi = 9, n_3mpi = 13 animals per group; Mean values ± SEM. f Positive area of Picrosirius red staining was quantified relative to total lung area; n_mock = 4, n_1mpi = 7, n_3mpi = 6 animals per group. g Lungs of mock and PASC animals were taken at 45 days post-infection (dpi) for bulk proteomics analysis. 1D annotation enrichment analysis of proteins changing in lungs post-infection compared to mock is shown (significance was set to Benjamini Hochberg FDR < 0.02). n_mock = 4, n_pasc = 5 animals per group. h Histological analysis of H&E-stained hearts. Scale bar = 1 mm. i Quantification of right ventricle area (n_mock=8, n_1mpi = 5, n_3mpi = 6 animals per group.; Mean ± SEM). j Histological analysis of H&E-stained intestines. k Total histological score of the small (n_mock=7, n_1mpi = 8, n_3mpi = 10 animals per group) and large intestines (n_mock=8 n_1mpi = 6, n_3mpi = 7 animals per group; mean values ± SEM). l IHC of fixed brains at 45 dpi, stained with IBA-1 (microglia). Scale bar = 50 µm. m Quantification of the projection area of cells positive for IBA-1 staining in the hippocampus (n = 5 animals per group; >18 cells were counted per mouse; violin plots show median and quartiles). P-values are indicated above the graph and were determined by e Mixed effect analysis with Tukey’s multiple comparison tests (f, i, k) One-way ANOVA with Tukey’s multiple comparisons tests f,I,k and m nested one-way ANOVA. Source data are provided as a Source Data file. Figure 4a Partially created in BioRender⁹⁴.