Summary
There are no known cures or vaccines for COVID-19, the defining pandemic of this era. Animal models are essential to fast track new interventions and nonhuman primate (NHP) models of other infectious diseases have proven extremely valuable. Here we compare SARS-CoV-2 infection in three species of experimentally infected NHPs (rhesus macaques, baboons, and marmosets). During the first 3 days, macaques developed clinical signatures of viral infection and systemic inflammation, coupled with early evidence of viral replication and mild-to-moderate interstitial and alveolar pneumonitis, as well as extra-pulmonary pathologies. Cone-beam CT scans showed evidence of moderate pneumonia, which progressed over 3 days. Longitudinal studies showed that while both young and old macaques developed early signs of COVID-19, both groups recovered within a two-week period. Recovery was characterized by low-levels of viral persistence in the lung, suggesting mechanisms by which individuals with compromised immune systems may be susceptible to prolonged and progressive COVID-19. The lung compartment contained a complex early inflammatory milieu with an influx of innate and adaptive immune cells, particularly interstitial macrophages, neutrophils and plasmacytoid dendritic cells, and a prominent Type I-interferon response. While macaques developed moderate disease, baboons exhibited prolonged shedding of virus and extensive pathology following infection; and marmosets demonstrated a milder form of infection. These results showcase in critical detail, the robust early cellular immune responses to SARS-CoV-2 infection, which are not sterilizing and likely impact development of antibody responses. Thus, various NHP genera recapitulate heterogeneous progression of COVID-19. Rhesus macaques and baboons develop different, quantifiable disease attributes making them immediately available essential models to test new vaccines and therapies.
Competing Interest Statement
RC, Jr is funded by Regeneron, Inc. This funder had no role, however, in the design and execution of the experiments and the interpretation of data. The authors declare that no other financial conflict of interest exists. This work was primarily supported by a philanthropic award to Texas Biomed Coronavirus Working Group; a SNPRC Pilot study award to LDG, RC, JP, LM and JBT; an award to RC, Jr from Regeneron Pharmaceuticals, (contract # 2020_004110) in part with federal funds from the Department of Health and Human Services; Office of the Assistant Secretary for Preparedness and Response; Biomedical Advanced Research and Development Authority, under Contract No. HHSO100201700020C; and institutional NIH awards P51OD111033 and U42OD010442. Some members of the Regeneron team provided direct scientific help and are thus coauthors on this paper. However, the views expressed here are those of the authors and do not necessarily represent the views or official position of the funding agencies.
Footnotes
Abbreviations: COVID-19, Coronavirus disease 2019; SARS-CoV-2, Severe Acute Respiratory Syndrome Coronavirus-2; BAL, bronchoalveolar lavage; PFU, Plaque Forming Unit; CRP, C-reactive protein; CXR, thoracic radiograph; NHP, nonhuman primate; PBMC, peripheral blood mononuclear cell; dpi, days post-infection.
