(1100) Major congenital malformation in an experimental mouse model of COVID-19

We recently reported the first-ever case of maternal second-trimester SARS-CoV-2 infection resulting in severe neonatal brain damage and associated placental abnormalities (Pediatrics, 2023). We, therefore, explored whether we could induce major congenital malformation (MCM) in our established murine hepatitis coronavirus (MHV-1) mouse model of COVID-19 using a high viral load.

Study Design:

Pregnant A/J mice (N=26, Jackson Laboratories, ME, USA) were divided into 2 groups: Group 1, control (CON), pregnant mice without virus inoculation (N=14), and Group 2, pregnant mice which were inoculated at day 15 of pregnancy (equivalent to second trimester in humans) with 5000 PFU MHV-1 intranasally (N=12) (Viruses, 2021). On days 20 and 21 of pregnancy (expected delivery timepoint), pups delivered spontaneously, and were collected from CON and MHV-1-infected pregnant mice. Clinical evaluation was performed on the mother and pups for MCM, and the MCM and survival rates for the pups were calculated. Data were analyzed by unpaired t-test (two-tailed) using GraphPad 9.5.1 software. Four independent examiners performed clinical evaluation postnatally.

Results:

CON mice had higher live birth rates compared to MHV-1 infected mice (39/62, 62.9% in CON, vs. 5/12, 41.6% in MHV-1, p< 0.008) (Fig. 1). MHV-1 infected mice pups had MCM when compared to no MCM in the CON group (7/12, 58.3% in MHV-1-infected vs. 0/62, 0% in CON, p< 0.0001). In the MHV-1 infected group (N=12), pups with MCM were all stillborn (6/6, 100%), compared to stillborn pups without MCM (1/7, 14.3%, p< 0.0001) (Fig. 1). Interestingly, of the 6 MCM, there were 3 cases central nervous system malformations (brain/face, craniothoracopagus twinning, and neural tube defect), and 2 abdominal wall defects (gastroschisis/omphalocele).

Conclusion:

Our findings strongly suggest that MCM can be induced in the second trimester in our established MHV-1 mouse model of COVID-19, which replicates both acute and long COVID in Biosafety Level 2 conditions. Our model is useful to evaluate pathophysiology in COVID and affords an opportunity to evaluate therapeutic agents.