3D visualization of SARS-CoV-2 infection and receptor distribution in Syrian hamster lung lobes display distinct spatial arrangements

Abstract

SARS-CoV-2 attaches to angiotensin-converting enzyme 2 (ACE2) to gain entry into cells after which the spike protein is cleaved by the transmembrane serine protease 2 (TMPRRS2) to facilitate viral-host membrane fusion. ACE2 and TMPRRS2 expression profiles have been analyzed at the genomic, transcriptomic, and single-cell RNAseq level, however, biologically relevant protein receptor organization in whole tissues is still poorly understood. To describe the organ-level architecture of receptor expression, related to the ability of ACE2 and TMPRRS2 to mediate infectivity, we performed a volumetric analysis of whole Syrian hamster lung lobes. Lung tissue of infected and control animals were stained using antibodies against ACE2 and TMPRRS2, combined with fluorescent spike protein and SARS-CoV-2 nucleoprotein staining. This was followed by light-sheet microscopy imaging to visualize expression patterns. The data demonstrates that infection is restricted to sites with both ACE2 and TMPRRS2, the latter is expressed in the primary and secondary bronchi whereas ACE2 is predominantly observed in the terminal bronchioles and alveoli. Conversely, infection completely overlaps at these sites where ACE2 and TMPRSS2 co-localize.

Oral administration of S-217622, a SARS-CoV-2 main protease inhibitor, decreases viral load and accelerates recovery from clinical aspects of COVID-19

“…Samples for whole imaging analysis were prepared following the method of iDISCO as previously described with minor modifications 39 . Lung tissues at 4 dpi were fixed in 3.7% formaldehyde in PBS.…”

Using in vivo animal models for studying SARS-CoV-2

“…Transcriptomic results suggested that transmembrane serine protease 2 is expressed in higher concentrations and is more widely distributed than ACE2. Only in places where both coexisted, pulmonary middle lobe, tertiary bronchioles, and in places at the interface between bronchioles and alveoli, infection was observed [ 93 ].…”