Facilitating Mouse Studies of Post-acute Sequelae of COVID-19 (PASC)

ABSTRACT

COVID-19, caused by SARS-CoV-2, and its chronic form, Post-Acute Sequelae of COVID-19 (PASC), remain significant public health concerns. Transgenic mice are an effective model for acute COVID-19 research, but PASC studies are currently lacking due to the prohibitive costs of performing such studies in an Animal Biosafety Level 3 (ABSL-3) containment setting. The goal of this study was to determine the natural timing of clearance of the SARS-CoV-2 virus from mice and establish a protocol for transfer of animals from ABSL- 3 to ABSL-2 for PASC studies. We hypothesized that infected mice would clear viral infection by approximately 3 to 4 wk postinfection (WPI). Six- to 18-wk-old, B6.Cg-Tg(K18-ACE2)2Prlmn/J (hACE2) mice (N = 48/sex) were intranasally inoculated with a pre-alpha strain of SARS-CoV-2 in an ABSL-3 containment setting. Environmental samples, oral swabs, and fecal samples were collected weekly up to 8 wk postinoculation and cohorts of surviving mice were necropsied at 4, 7, and 8 WPI when lung and brain were collected. Viral loads in all samples were quantified via RT-qPCR. Survival was significantly affected by sex, with males more susceptible (P = 0.002), but not age (P = 0.005). SARS-CoV-2 viral RNA copies were present in the lungs of mice at 4, 7, and 8 WPI, indicating that the mice had not yet cleared infection by the culmination of the study and raising the possibility of persistent infection.