Characteristic and quantifiable COVID-19 like abnormalities in CT- and PET/CT-1 imaged lungs of SARS-CoV-2 infected crab eating macaques (Macaca fascicularis)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is causing an exponentially increasing number of coronavirus disease 19 (COVID-19) cases globally. Prioritization of medical countermeasures for evaluation in randomized clinical trials is critically hindered by the lack of COVID-19 animal models that enable accurate, quantifiable, and reproducible measurement of COVID-19 pulmonary disease free from observer bias. We first used serial computed tomography (CT) to demonstrate that bilateral intrabronchial instillation of SARS CoV-2 into crab-eating macaques (Macaca fascicularis) results in mild-to-moderate lung abnormalities qualitatively characteristic of subclinical or mild-to-moderateCOVID-19 (e.g., ground-glass opacities with or without reticulation, paving, or alveolar consolidation, peri-bronchial thickening, linear opacities) at typical locations (peripheral>central, posterior and dependent, bilateral, multi-lobar). We then used positron emission tomography (PET) analysis to demonstrate increased FDG uptake in the CT-defined lung abnormalities and regional lymph nodes. PET/CT imaging findings appeared in all macaques as early as 2 days post exposure, variably progressed, and subsequently resolved by 6-12 days post exposure. Finally, we applied operator-independent, semi-automatic quantification of the volume and radiodensity of CT abnormalities as a possible primary endpoint for immediate and objective efficacy testing of candidate medical countermeasures.

Finding an Alternative Approach when Critical Medical Supplies Are in Short Supply during the COVID-19 Pandemic

The COVID-19 pandemic has created shortages of various medical supplies, in addition to personal protective equipment that threaten to delay or prevent the timely initiation of important studies. At the height of the pandemic, researchers at the National Institute of Allergy and Infectious Diseases, Integrated Research Facility were working to develop a nonhuman primate (NHP) model for COVID-19. Computed tomography (CT) of the lungs is a critical component of these studies. This procedure involves placing intubated NHPs on a ventilator circuit to allow a breath hold to be performed on the animal during the chest CT. A pediatric-sized heat moisture exchanger (viral/bacterial) filter is placed on the endotracheal tube to prevent contamination of the ventilator circuit on the anesthesia machine. When planning and scheduling these studies, we learned the filters were not available or were backordered depending on the vendor. The filters are normally used once and discarded, but we quickly realized the supply would run out if we did not receive a new shipment. A plan was devised to reuse filters on noninfected animals or sterilize filters using ethylene oxide (EtO) gas after each use on virus-exposed animals before reusing the same filter on the same animal. After sterilization, a portable gas leak detector was used to check each filter for residual EtO. The first set of filters requiring gas sterilization still had low levels of residual EtO (2.6-2.9 ppm) after overnight aeration in the BSC. An additional 24-h aeration period brought the EtO level to 0.0 ppm. After each gas sterilization, the integrity of the filter was evaluated with a handheld particle counter capable of counting particles as small as 0.3 μm. There were no particles detected which indicated the filtration integrity remained intact for particles ≥ 0.3 μm. We describe the procedures we employed to sterilize these filters and determine if they would be safe and effective for reuse. These procedural modifications allowed critically important research to find an animal model for COVID-19 to continue without compromising animal welfare.