Replication of Severe Acute Respiratory Syndrome Coronavirus 2 in Human Respiratory Epithelium

Abstract

Currently, there are four seasonal coronaviruses associated with relatively mild respiratory tract disease in humans. However, there is also a plethora of animal coronaviruses which have the potential to cross the species border. This regularly results in the emergence of new viruses in humans. In 2002, severe acute respiratory syndrome coronavirus (SARS-CoV) emerged and rapidly disappeared in May 2003. In 2012, Middle East respiratory syndrome coronavirus (MERS-CoV) was identified as a possible threat to humans, but its pandemic potential so far is minimal, as human-to-human transmission is ineffective. The end of 2019 brought us information about severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emergence, and the virus rapidly spread in 2020, causing an unprecedented pandemic. At present, studies on the virus are carried out using a surrogate system based on the immortalized simian Vero E6 cell line. This model is convenient for diagnostics, but it has serious limitations and does not allow for understanding of the biology and evolution of the virus. Here, we show that fully differentiated human airway epithelium cultures constitute an excellent model to study infection with the novel human coronavirus SARS-CoV-2. We observed efficient replication of the virus in the tissue, with maximal replication at 2 days postinfection. The virus replicated in ciliated cells and was released apically. IMPORTANCE Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged by the end of 2019 and rapidly spread in 2020. At present, it is of utmost importance to understand the biology of the virus, rapidly assess the treatment potential of existing drugs, and develop new active compounds. While some animal models for such studies are under development, most of the research is carried out in Vero E6 cells. Here, we propose fully differentiated human airway epithelium cultures as a model for studies on SARS-CoV-2.

First contact: the role of respiratory cilia in host-pathogen interactions in the airways

“…Peer-reviewed, detailed studies of SARS-CoV2 pathobiology in AECs are limited due to its recent emergence and lack of antibody tools. Preliminary findings show that much like SARS-CoV, SARS-CoV2 can infect and replicate in ciliated AECs (134). Histology of lung biopsies from a 72-yr-old man with COVID-19 showed extensive damage to the airway epithelium, with loss of ciliated AECs and a denuded epithelium (217).…”

Adult Stem Cell-derived Complete Lung Organoid Models Emulate Lung Disease in COVID-19

“…We first asked how viral infectivity varies in the two models. Because multiple groups have shown the importance of the ciliated airway cells for infectivity (i.e., viral entry, replication and apical release (Hou et al, 2020;Hui et al, 2020;Milewska et al, 2020;Zhu et al, 2020)), as positive controls, we infected monolayers of human airway epithelia (see Fig S4F-I). AT2 cells, which express high levels of viral entry receptors ACE2 and TMPRSS2 (Fig 1A, Fig S1A) have been shown to be proficient in viral entry, but are least amenable to sustained viral release and infectivity (Hou et al, 2020;Hui et al, 2020).…”

Leveraging 3D Model Systems to Understand Viral Interactions with the Respiratory Mucosa

“…More generally, these systems have been widely used to assess viral cellular tropism [ 49 , 76 , 109 , 110 , 111 , 112 ], apical or basolateral sites of viral entry and release [ 53 , 76 , 109 , 113 ], and component cell type-specific responses to viral infection [ 71 , 72 ]. ALI Transwell models are also increasingly genetically tractable, further enabling the mechanistic dissection of specific host factors with regard to infection phenotypes.…”