Abstract
The global urgency to uncover medical countermeasures to combat the COVID-19 pandemic caused by the severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) has revealed an unmet need for robust tissue culture models that faithfully recapitulate key features of human tissues and disease. Infection of the nose is considered the dominant initial site for SARS-CoV-2 infection and models that replicate this entry portal offer the greatest potential for examining and demonstrating the effectiveness of countermeasures designed to prevent or manage this highly communicable disease. Here, we test an air–liquid-interface (ALI) differentiated human nasal epithelium (HNE) culture system as a model of authentic SARS-CoV-2 infection. Progenitor cells (basal cells) were isolated from nasal turbinate brushings, expanded under conditionally reprogrammed cell (CRC) culture conditions and differentiated at ALI. Differentiated cells were inoculated with different SARS-CoV-2 clinical isolates. Infectious virus release into apical washes was determined by TCID50, while infected cells were visualized by immunofluorescence and confocal microscopy. We demonstrate robust, reproducible SARS-CoV-2 infection of ALI-HNE established from different donors. Viral entry and release occurred from the apical surface, and infection was primarily observed in ciliated cells. In contrast to the ancestral clinical isolate, the Delta variant caused considerable cell damage. Successful establishment of ALI-HNE is donor dependent. ALI-HNE recapitulate key features of human SARS-CoV-2 infection of the nose and can serve as a pre-clinical model without the need for invasive collection of human respiratory tissue samples.
Highlights
Over the past 15 years, 90% of novel medical countermeasures that showed promise in preclinical animal and cell line models failed in human clinical trials: 50% for lack of efficacy, 30% for toxicity [1,2]
To evaluate ALI-human nasal epithelium (HNE) culture as a model for SARS-CoV-2 infection, turbinate brush samples were collected from adult and child donors and infected with SARS-CoV-2 clinical isolates (Table 1)
The failure to translate from a pre-clinical model to human clinical trial raises the cost per new drug to $US2.8 billion [1,2]
Summary
Over the past 15 years, 90% of novel medical countermeasures that showed promise in preclinical animal and cell line models failed in human clinical trials: 50% for lack of efficacy, 30% for toxicity [1,2]. The toxicity was not detected in non-human primates, the closest animal model to humans. This failure rate continues to this day. Human adult stem cell-derived organoids fill the gap between animal and cell line pre-clinical models, and human clinical trials. Studies by the Clevers [9] and Estes [10] laboratories exemplified the power of tissue stem cell derived organoids for modelling lung (respiratory syncytial virus (RSV)) and gut (human noroviruses (HuNoVs)) infection, respectively. In a similar vein, induced pluripotent stem (iPS) cell derived organoids proved invaluable for understanding the pathogenesis of Zika virus (ZIKV) in the brain [11,12]. The advantages that these human organoids provide in modelling human viral infectious diseases remained largely overlooked in preference for decades old virus culture systems
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