Adaptation of SARS-CoV-2 in BALB/c mice for testing vaccine efficacy

Laboratory wild type mouse strains are not susceptible for SARS-CoV-2 infection. To obtain a mouse-adapted virus, BALB/c mice were inoculated with SARS-CoV-2, and newly obtained virus from infected lung was further inoculated to next animals. Total 6 mouse passages resulted in the production of mouse-adapted strain (MASCp6).  Five nucleotide mutations were identified in the MASCp6, in which an amino acid mutation in the spike protein (N501Y) was found. The N501Y locates in the receptor binding domain, strongly indicates that this may be important for the recognition of mouse ACE2 receptor. This virus-infected animal model is very effective for the evaluation of vaccine against SARS-CoV-2 infection using small animals.