A SCID mouse-human lung xenograft model of SARS-CoV-2 infection

SARS-CoV-2 infection, which is responsible for the current COVID-19 pandemic, can cause lifethreatening pneumonia, respiratory failure and even death.Characterizing SARS-CoV-2 pathogenesis in primary human target cells and tissues is crucial for developing vaccines and therapeutics.However, given the limited access to clinical samples from COVID-19 patients, there is a pressing need for in vitro/in vivo models to investigate authentic SARS-CoV-2 infection in primary human lung cells or tissues with mature structures.The present study was designed to evaluate a humanized mouse model carrying human lung xenografts for SARS-CoV-2 infection in vivo.Methods: Human fetal lung tissue surgically grafted under the dorsal skin of SCID mice were assessed for growth and development after 8 weeks.Following SARS-CoV-2 inoculation into the differentiated lung xenografts, viral replication, cell-type tropism and histopathology of SARS-CoV-2 infection, and local cytokine/chemokine expression were determined over a 6-day period.The effect of IFN-α treatment against SARS-CoV-2 infection was tested in the lung xenografts.Results: Human lung xenografts expanded and developed mature structures closely resembling normal human lung.SARS-CoV-2 replicated and spread efficiently in the lung xenografts with the epithelial cells as the main target, caused severe lung damage, and induced a robust pro-inflammatory response.IFN-α treatment effectively inhibited SARS-CoV-2 replication in the lung xenografts.Conclusions: These data support the human lung xenograft mouse model as a useful and biological relevant tool that should facilitate studies on the pathogenesis of SARS-CoV-2 lung infection and the evaluation of potential antiviral therapies.