Human convalescent plasma protects K18-hACE2 mice against severe respiratory disease.

SARS-CoV-2 is the causative agent of COVID-19 and human infections have resulted in a global health emergency. Small animal models that reproduce key elements of SARS-CoV-2 human infections are needed to rigorously screen candidate drugs to mitigate severe disease and prevent the spread of SARS-CoV-2. We and others have reported that transgenic mice expressing the human angiotensin-converting enzyme 2 (hACE2) viral receptor under the control of the Keratin 18 (K18) promoter develop severe and lethal respiratory disease subsequent to SARS-CoV-2 intranasal challenge. Here we report that some infected mice that survive challenge have residual pulmonary damages and persistent brain infection on day 28 post-infection despite the presence of anti-SARS-COV-2 neutralizing antibodies. Because of the hypersensitivity of K18-hACE2 mice to SARS-CoV-2 and the propensity of virus to infect the brain, we sought to determine if anti-infective biologics could protect against disease in this model system. We demonstrate that anti-SARS-CoV-2 human convalescent plasma protects K18-hACE2 against severe disease. All control mice succumbed to disease by day 7; however, all treated mice survived infection without observable signs of disease. In marked contrast to control mice, viral antigen and lesions were reduced or absent from lungs and absent in brains of antibody-treated mice. Our findings support the use of K18-hACE2 mice for protective efficacy studies of anti-SARS-CoV-2 medical countermeasures (MCMs). They also support the use of this system to study SARS-CoV-2 persistence and host recovery.

Development of a coronavirus disease 2019 nonhuman primate model using airborne exposure.

Airborne transmission is predicted to be a prevalent route of human exposure with SARS-CoV-2. Aside from African green monkeys, nonhuman primate models that replicate airborne transmission of SARS-CoV-2 have not been investigated. A comparative evaluation of COVID-19 in African green monkeys, rhesus macaques, and cynomolgus macaques following airborne exposure to SARS-CoV-2 was performed to determine critical disease parameters associated with disease progression, and establish correlations between primate and human COVID-19. Respiratory abnormalities and viral shedding were noted for all animals, indicating successful infection. Cynomolgus macaques developed fever, and thrombocytopenia was measured for African green monkeys and rhesus macaques. Type II pneumocyte hyperplasia and alveolar fibrosis were more frequently observed in lung tissue from cynomolgus macaques and African green monkeys. The data indicate that, in addition to African green monkeys, macaques can be successfully infected by airborne SARS-CoV-2, providing viable macaque natural transmission models for medical countermeasure evaluation.