key: cord-0860385-9pzmr1n0
authors: Varga, Zsuzsanna; Flammer, Andreas J; Steiger, Peter; Haberecker, Martina; Andermatt, Rea; Zinkernagel, Annelies; Mehra, Mandeep R; Scholkmann, Felix; Schüpbach, Reto; Ruschitzka, Frank; Moch, Holger
title: Electron microscopy of SARS-CoV-2: a challenging task – Authors' reply
date: 2020-05-19
journal: Lancet
DOI: 10.1016/s0140-6736(20)31185-5
sha: 170277bcac952ea843a2c5ff9a1e846541bd8033
doc_id: 860385
cord_uid: 9pzmr1n0

nan

The framework of endotheliitis provides an explanation for the unique predilection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in those in dividuals with hypertension, diabetes, or established cardiovascular disease, a group known to have pre-existing endothelial dysfunction. COVID-19-endotheliitis could also explain impaired microcirculatory function across different organs and the frequently observed prothrombotic state with in-situ clot formation. Endothelial infection and injury by SARS-CoV-1 has been shown. 2 Our demonstration of viral particles using electron microscopy (EM) is supported by several reports independently describing ultrastructural round virus-like particles in the setting of a SARS-CoV-2 infection. [3] [4] [5] [6] We demonstrated tubulo-reticular structures in the immediate vicinity of the spherical particles that are strikingly identical to SARS-CoV-1-associated membrane changes described by Goldsmith and colleagues in 2004. 7 In our EM thinsection images, the virus-like particles were relatively large (mean diameter 180 nm [SD 10]). How ever, subsequent analysis of more EM images has revealed a mean particle size of 67 nm (SD 15 nm, median 65 nm, 95% CI 41-102; n=33). Zhu and colleagues 5 noted that SARS-CoV-2 virions ranged from "about 60 to 140 nm". In another recent study, 6 virus-like particles in patients with confirmed SARS-CoV-2 infection were 70-110 nm in diameter. By comparison, SARS-CoV-1 viral particles analysed with the same technique (ultrathin EM imaging) were 50-80 nm in diameter. [7] [8] [9] [10] Goldsmith and colleagues have studied coronavirus isolates grown in cell culture, whereas our EM data of virus-like particles were obtained from a post-mortem kidney allograft obtained during autopsy. Since most other recent reports of patients with COVID-19 also describe post mortem findings, it remains unclear to what extent tissue type (cell culture, fresh biopsy material, or autopsy material), time to fixation, and post mortal autolysis alter subcellular structures in preparation for EM. This notwithstanding, these observed particles in patients with COVID-19 should be best designated as virus-like particles because definitive assign ment of these structures as SARS-CoV-2 virions requires immuno-EM.

Investigations with vascular organoids that preceded our observations 1 showed that SARS-CoV-2 can infect human blood vessels via the ACE2 pathways, providing the first and direct evidence that the virus can indeed invade human vasculature. 11 Our findings have also been confirmed in descriptions of renal tropism of SARS-CoV-2, with detection of SARS-CoV-2 protein in human glomerular endothelial and epithelial cells. 12 Importantly, our demonstration of virus cell infection in the kidney and endotheliitis 1 points to a general host inflammatory response causing hyperinflammation as a principal participant in the vascular pathology of COVID-19. Endothelial cell dysfunction, which might subsequently induce a prothrombotic state, could thus explain the vascular microcirculatory complications seen in different organs in patients with COVID-19.

Endothelial cell infection and endotheliitis in COVID-19

Molecular pathology in the lungs of severe acute respiratory syndrome patients

Renal histopathological analysis of 26 postmortem findings of patients with COVID-19 in China

Collapsing glomerulopathy in a COVID-19 patient

A novel coronavirus from patients with pneumonia in China

Post-mortem examination of COVID19 patients reveals diffuse alveolar damage with severe capillary congestion and variegated findings of lungs and other organs suggesting vascular dysfunction

Ultrastructural characterization of SARS coronavirus

Modern uses of electron microscopy for detection of viruses

Immunohistochemical, in situ hybridization, and ultrastructural localization of SARS-associated coronavirus in lung of a fatal case of severe acute respiratory syndrome in Taiwan

The life cycle of SARS coronavirus in Vero E6 cells

Inhibition of SARS-CoV-2 infections in engineered human tissues using clinical-grade soluble human ACE2

Multiorgan and renal tropism of SARS-CoV-2