Mucociliary Transport Deficiency in Syrian Hamsters with SARS-CoV-2

RATIONALE: SARS-CoV-2 causes COVID-19 disease and infects respiratory epithelial cells, but how it affects ciliated cell function and the mucociliary transport apparatus is unknown. Abnormal mucociliary function could predispose to COVID-19 progression and/or secondary infection. Micro-optical coherence tomography (μOCT) is a novel method to simultaneously visualize and quantify the functional microanatomy of airways. Here, we established a hamster model of COVID-19 and evaluated their tracheas by μOCT. METHODS: Adult golden Syrian hamsters were inoculated intranasally with 3.2 × 105 (high dose, HD, N=4) or 3.2 × 104 (low dose, LD, N=4) plaque-forming units of SARS-CoV-2 (WA/1 strain). Clinical signs were monitored daily, nasal brushes collected intermittently, and hamsters were euthanized seven days (D7) after inoculation. Tracheas were imaged by μOCT, nasal washes and bronchial alveolar lavage fluid (BALF) from right lung lobes were collected for quantitation of viral load by qRT-PCR, and left lungs were inflated with and fixed in 10% neutral buffered formalin for histological analysis. Age-matched hamsters were used as uninfected controls (N=5). RESULTS: SARS-CoV-2 hamsters lost weight through D7 in dose-dependent fashion (-11% in HD vs. -4% in LD, p=0.02) and HD hamsters showed moderate lethargy. Nasal brushes on D4 and nasal washes on D7 contain 105-106 genome copies of virus while BALF on D7 was less than 104 genome copies and intermittently detected in LD. Histology demonstrated patchy and multifocal interstitial pneumonia (type II pneumocyte hyperplasia and mononuclear cell infiltrate), with ∼20% area affected in HD that was more variable in LD. Functional microanatomy of tracheas revealed diminished area of active ciliary beating (control 18 ± 2 vs. LD 7 ± 1%, p=0.0002, control vs. HD 9 ± 1%, p=0.001), reduced ciliary beat frequency (control 10.88 ± 0.70 vs. LD 8.83 ± 0.34 Hz, p=0.01, control vs. HD 8.26 ± 0.33 Hz, p=0.001), and decreased periciliary liquid depth (control 6.41 ± 0.18 vs. HD 5.61± 0.12 μ m, p=0.027). Mucociliary transport rate was diminished (control 0.84 ± 0.19 vs. LD 0.48 ± 0.16 vs. HD 0.37 ± 0.13 mm/min) although not statistically significant. Additional cohorts are in progress. CONCLUSION: SARS-Cov-2 infected hamsters exhibit reduced body weight, high viral load, and histopathological injury through 7 days. SARS-CoV-2 caused functional deficits of the mucociliary transport apparatus, consistent with early findings in COVID-19 patients (see Vijaykumar et al.). Abnormal ciliated cell function is important to SARS-CoV-2 pathogenesis, and may help monitor progression and represent a treatment opportunity for COVID-19.