To use severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pseudovirus containing spike protein (S) particles and expressing Luciferase luciferase and GFP fluorescent proteins to infect K18-hACE2 transgenic mice, to explore the establishment and evaluation of a usable animal model, and to provide ideas for the subsequent screening of effective drug targets.

(1) Twelve K18-hACE2 transgenic mice were randomly divided into control and model groups. The mice in the model group were given 50 μL of 1×10⁹PFU/each viral solution by pipette drops, and those in the control group were given an equal amount of empty vector viral solution. (2) On the 3rd day after modeling, Luciferase in vivo fluorescence was observed and the samples were collected. The lung tissue GFP was observed under fluorescence microscopy. The lung tissue pathology was observed under light microscope. The lung tissue ultrastructure was observed under transmission electron microscope. S protein expression in lung tissue was detected by qPCR. The levels of interleukin 6 (IL-6) and interleukin 10 (IL-10) in serum were detected by ELISA. Western Blot assay was used for angiotensin converting enzyme 2 (ACE2) protein expression in lung tissue.

(1) In vivo imaging revealed a large fluorescence area in the nasopharynx and both lungs of the model mice, a large amount of green fluorescence in frozen sections of lung tissue, and pathological changes in lung histopathological sections and ultramicroscopic findings, while no fluorescence expression or pathological changes were observed in the lungs of the control mice. (2) S protein mRNA expression was seen in the lungs of the model mice (P<0.01). (3) Compared with those of the control mice, the expression of IL-6 in the serum of the model mice was increased and the expression of IL-10 was decreased (P<0.01). IL-6 expression was increased and IL-10 expression was decreased in the serum of mice in the model group compared with those in the control group (P<0.01). (4)　ACE2 receptor content was decreased in lung tissues of the mice in the model group compared to that in the control group (P<0.01).

In this study, a model of SARS-CoV-2 pseudovirus infection in hACE2 transgenic mice was established and evaluated, and the optimization study of the model still needs to be followed up for further improvement.