Developing human in vitro models for SARS-CoV-2 infection to more closely resemble the in vivo situation.

Abstract

The SARS-CoV-2 pandemic has taken over 4 million lives over the world and impacted countless others. Despite therapeutic strategies and vaccines being developed, cases continue to rise and the end of the pandemic seems to be far from now. For this reason, new insights into the biology of SARS-CoV-2 and new strategies to manage and fight the virus are urgently needed. In vitro models are a useful way to study SARS-CoV-2 biology in high throughput and simple systems. Currently, the golden standard to study in vitro SARS-CoV-2 infection is the monkey kidney cell line Vero E6, which is not directly translatable because of the difference in species and has been recorded to cause divergent evolution. This problem could be overcome with human immortalized cell lines or primary cell models, however, both cell lines and primary cell models show low permissiveness to infection. In this project and report, we optimized the infection ratios of immortalized cell lines by transducing them with SARS-CoV-2 receptor Ace2 and protease TMPRSS2. Transduction led to a higher permissiveness to infection as well as virus production, suggesting that these transduced immortalized cell lines can be used for further SARS-CoV-2 research as well as virus production for academic research purposes. In addition to the immortalized cell lines, we optimized the use of organoids and Air Liquid Interface (ALI) cultured cells derived from primary human airway cell samples for SARS-CoV-2 infection experiments. Furthermore, we showed that flow cytometry can be used to identify different cell populations within the ALI cultures using only the forward and side scatter. Taken together, the results show that there is a lot to be gained in translatability when it comes to in vitro models.