Disruption of Adaptive Immunity Enhances Disease in SARS-CoV-2 Infected Syrian Hamsters

Animal models recapitulating human COVID-19 disease, especially with severe disease, are urgently needed to understand pathogenesis and evaluate candidate vaccines and therapeutics. Here, we develop novel severe disease animal models for COVID-19 involving disruption of adaptive immunity in Syrian hamsters. Cyclophosphamide (CyP) immunosuppressed or RAG2 knockout (KO) hamsters were exposed to SARS-CoV-2 by the respiratory route. Both the CyP-treated and RAG2 KO hamsters developed clinical signs of disease that were more severe than in immunocompetent hamsters, notably weight loss, viral loads, and fatality ( RAG2 KO only). Disease was prolonged in transiently immunosuppressed hamsters and uniformly lethal in RAG2 KO hamsters. We evaluated the protective efficacy of a neutralizing monoclonal antibody and found that pretreatment, even in immunosuppressed animals, limited infection. Our results suggest that functional B and/or T cells are not only important for the clearance of SARS-CoV-2, but also play an early role in protection from acute disease. One Sentence Summary An antibody targeting the spike protein of SARS-CoV-2 limits infection in immunosuppressed Syrian hamster models. ### Competing Interest Statement The authors have declared no competing interest.