Figure 7.
SARS-CoV-2 replicates efficiently in the brain of mice and can cause CNS-specific lethality.(A–C) Mice expressing human ACE2 under the K18 promoter (K18-hACE2) were infected with SARS-CoV-2 intranasally, and brains of the mice were collected on days 2, 4, and 7 hpi for qPCR (A) or plaque assay (B). (C–E) iDISCO+ whole brain immunolabeling against the nucleocapsid protein of SARS-CoV-2 7 d after an intranasal infection, shown as 300-µm projection planes.(C) Dorsal, ventral, and sagittal projections showing widespread distribution of the virus in the forebrain with patches of high viral density in the cortex (arrow). The virus is not detected in the cerebellum, except for the pial meninges and DCNs. (D) 300-µm-deep projection planes in the cortex showing cortical patches of viral expression (arrowhead), reduced infection of the cells in layer 4, and expression in pyramidal neurons (arrow).(E) ClearMap analysis of the infected cells distribution (n = 3), registered to the Allen Brain Atlas, showing wide distribution of the virus across brain regions, with a few regions with lower densities, among which are dentate gyrus (DG), globus pallidus internal segment (GPi), CA3 hippocampal region, cortical layer 4, and ventromedial hypothalamus (VMH). (F and G) Analysis of the vascular network using ClearMap and iDISCO+ 7 d after intranasal infection by mapping of the vascular network with colabeling of the N protein. Planes at the level of the nose somatosensory cortex are shown. (F) Control uninfected brains. Branch point densities (top panel) peak in controls at layer 4. The density of radially oriented vessels (middle panel) peaks in layers 1, 2, and 3 while decreasing in layers 4, 5, and 6. (G) Brain 7 d after infection. Expression of the N viral protein by neural cells is shown at the level of the nose somatosensory cortex (300-µm projection plane and mapped densities). While branch point densities of vessels still show a peak in layer 4, the normal radial organization of the vessels is not measured in the nose region (arrowhead). Representative render of the vascular graph shows a decrease in vessel orientations in control layers 2 and 3.(H) Schematic of experiment for I and J. Adeno-associated viruses coding for human ACE2 (AAV-hACE2) were injected into the cisterna magna or intratracheally to induce brain-specific or lung-specific expression of hACE2. Brain hACE2–expressing mice were infected with SARS-CoV-2 intraventricularly, and lung hACE2–expressing mice were infected with SARS-CoV-2 intranasally.(I and J) Weight loss curve (I) and survival curve (J) of mice infected with SARS-CoV-2 in the lung (blue) and the brain (red and orange; blue, n = 10; red, n = 4; orange, n = 4). Experiments were performed twice for reproducibility. Scale bars = 1 mm (A and C), 200 µm (B), and 500 µm (D and E). CB, cerebellum; DCN, deep cerebellar nuclei; IC, inferior colliculus; SC, superior colliculus; SN, substantia nigra (reticulata or compacta); SS, somatosensory cortex, nose of barrel field.

SARS-CoV-2 replicates efficiently in the brain of mice and can cause CNS-specific lethality. (A–C) Mice expressing human ACE2 under the K18 promoter (K18-hACE2) were infected with SARS-CoV-2 intranasally, and brains of the mice were collected on days 2, 4, and 7 hpi for qPCR (A) or plaque assay (B). (C–E) iDISCO+ whole brain immunolabeling against the nucleocapsid protein of SARS-CoV-2 7 d after an intranasal infection, shown as 300-µm projection planes.(C) Dorsal, ventral, and sagittal projections showing widespread distribution of the virus in the forebrain with patches of high viral density in the cortex (arrow). The virus is not detected in the cerebellum, except for the pial meninges and DCNs. (D) 300-µm-deep projection planes in the cortex showing cortical patches of viral expression (arrowhead), reduced infection of the cells in layer 4, and expression in pyramidal neurons (arrow).(E) ClearMap analysis of the infected cells distribution (n = 3), registered to the Allen Brain Atlas, showing wide distribution of the virus across brain regions, with a few regions with lower densities, among which are dentate gyrus (DG), globus pallidus internal segment (GPi), CA3 hippocampal region, cortical layer 4, and ventromedial hypothalamus (VMH). (F and G) Analysis of the vascular network using ClearMap and iDISCO+ 7 d after intranasal infection by mapping of the vascular network with colabeling of the N protein. Planes at the level of the nose somatosensory cortex are shown. (F) Control uninfected brains. Branch point densities (top panel) peak in controls at layer 4. The density of radially oriented vessels (middle panel) peaks in layers 1, 2, and 3 while decreasing in layers 4, 5, and 6. (G) Brain 7 d after infection. Expression of the N viral protein by neural cells is shown at the level of the nose somatosensory cortex (300-µm projection plane and mapped densities). While branch point densities of vessels still show a peak in layer 4, the normal radial organization of the vessels is not measured in the nose region (arrowhead). Representative render of the vascular graph shows a decrease in vessel orientations in control layers 2 and 3.(H) Schematic of experiment for I and J. Adeno-associated viruses coding for human ACE2 (AAV-hACE2) were injected into the cisterna magna or intratracheally to induce brain-specific or lung-specific expression of hACE2. Brain hACE2–expressing mice were infected with SARS-CoV-2 intraventricularly, and lung hACE2–expressing mice were infected with SARS-CoV-2 intranasally.(I and J) Weight loss curve (I) and survival curve (J) of mice infected with SARS-CoV-2 in the lung (blue) and the brain (red and orange; blue, n = 10; red, n = 4; orange, n = 4). Experiments were performed twice for reproducibility. Scale bars = 1 mm (A and C), 200 µm (B), and 500 µm (D and E). CB, cerebellum; DCN, deep cerebellar nuclei; IC, inferior colliculus; SC, superior colliculus; SN, substantia nigra (reticulata or compacta); SS, somatosensory cortex, nose of barrel field.

This Feature Is Available To Subscribers Only

or Create an Account

Close Modal
Close Modal