Résilience - COVID-19 - Résilience - Coronavirus disease 2019

Human colonic organoids as a model to study SARS-CoV-2 variants infection – Organovir

Human colonic organoids as a model to study SARS-CoV-2 variants infection

New SARS-CoV-2 variants raised particular concerns worldwide due to their high transmissibility rates. The rapid emergence of such variants highlights the urgent need to develop highly relevant and standardized experimental models to study critical aspects of SARS-Cov-2 variant infection and replication but also to screen therapeutic candidates. In this respect, human intestinal organoids have emerged as a valuable model to study host-pathogen interactions, including SARS-CoV-2 infection.

Ability of SARS-CoV-2 variants to enter and replicate inside epithelial cells as compared to the parental strain taking human colonic organoids as a model

Our proposal aims to monitor the ability of SARS-CoV-2 variants of concern, including South Africa, United Kingdom and Brazil ones, to infect human colonic organoid-derived cell monolayers, a model of choice to study host pathogen interaction in a standardized and reproducible way closely mimicking the in vivo situation. Our proposal also aims to study the response of the colonic epithelium to these variants and the impact of this response on the infection process. Finally, our project will perform a first drug screening of therapeutic candidates known to interfere with infection by the SARS-CoV-2 parental strain.

Healthy colonic organoids are seeded and differentiated in multiwell plates with inserts or imaging chambers to generate human colonic organoid-derived cell monolayers closely mimicking mature and diversified colonic epithelial cells. Infection with SARS-CoV-2 parental strain and four variants are performed with or without prior treatment with drugs or interferons. Culture supernatants are collected to determine infectious virus production levels and cytokine secretion by the epithelium. Colonoids are processed either for qRT PCR to analyse viral RNA and interferon production by the epithelium or for spectral confocal microscopy to quantify viral entry, replication and to characterize infected cells and their physiological status.

We will determine the differences in entry, replication and infectious virus particles production of SARS-CoV-2 parental and variants strains. We will also analyse changes in the immune defence mechanisms initiated by the colonic epithelium to the different variants and the impact of this response on the infection process. Finally, we will determine the influence of interferons and SARS-CoV-2 entry inhibitors on the ability of the variants to infect human organoïd-derived cell monolayers.

This project will provide a model to assess the ability of SARS-CoV-2 variants to enter and replicate in colonic epithelial cells and the capability of these cells to defend themselves. It will also provide a proof of concept of the usefullness of the human colonic organoid to perform drug screening and identify or confirm therapeutic candidates that interfere with SARS-CoV-2 infection. Therefore, our project will not only further the understanding of SARS-CoV-2 variant infection and the immune response of the intestinal epithelium, but also contribute to the search for effective drugs against these infections.
Importantly, our experimental model will also allow in the future to rapidly assess the invasion mechanisms of other pathogens, the defence mechanisms of the colonic epithelium against these pathogens as well as to identify potential therapeutic candidates for other types of enteric infections, which is crucial in the case of rapidly spreading pathogens such as SARS-CoV-2.

None at present

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes the coronavirus disease 19 (COVID-19) with symptoms ranging from mild respiratory illness to severe lung injury, multi-organ failure and ultimately death. Although SARS-CoV-2 primarily infects the lungs, gastrointestinal symptoms are frequently observed and are associated with worse COVID-19 outcomes, underlying the need to also study the infection of the intestinal mucosa. New recently identified SARS-CoV-2 variants raised particular concerns worldwide due to their high transmissibility rates. They all bear mutations in the Spike protein that binds to host cells and allows virus entry. The rapid emergence of such variants highlights the urgent need to develop highly relevant and standardized experimental models to study critical aspects of SARS-CoV-2 variant infection and replication but also to screen therapeutic candidates and assess whether drugs known to affect SARS-CoV-2 parental strain entry and replication are still efficient on these variants. Our proposal aims to monitor the ability of SARS-CoV-2 variants of concern, including South Africa, United Kingdom and Brazil ones, to infect human colonic organoid-derived cell monolayers, a model of choice to study host pathogen interaction in a standardized and reproducible way closely mimicking the in vivo situation. Our proposal also aims to study the immune response of the colonic epithelium to these variants and the impact of this response on the infection process. Finally, our project will be useful to perform a first drug screening of therapeutic candidates known to interfere with infection by the SARS-CoV-2 parental strain. In conclusion, our project will help to understand how the SARS-CoV-2 mutations affect entry and replication of the virus, and defence mechanisms of the intestinal epithelium as well as virus resistance to therapeutic candidates or to interferons. In addition, our experimental model will allow to quickly investigate other potential therapeutic candidates for other types of enteric infections, which is crucial in case of rapidly spreading pathogens, such as SARS-CoV-2.

Project coordination

Hugues Lelouard (Centre National de la Recherche Scientifique-Centre d'Immunologie de Marseille-Luminy)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

CNRS-CIML Centre National de la Recherche Scientifique-Centre d'Immunologie de Marseille-Luminy
CRCM Centre de recherche en cancérologie de Marseille
MEPHI Microbes Evolution Phylogénie et Infections

Help of the ANR 79,520 euros
Beginning and duration of the scientific project: April 2021 - 12 Months

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