SARS-CoV-2 causes chronic lung inflammation and impaired respiratory capacity in aged Roborovski dwarf hamsters

Roborovski dwarf hamsters are permissive for SARS-CoV-2 infection and progress to acute viral pneumonia with profound lung tissue injury, recapitulating hallmarks of severe COVID-19 in vulnerable patient groups such as older adults. In this study, we established dwarf hamster whole body plethysmography and assessed disease severity and propensity for long-term compromise of lung recovery from severe COVID-19-like disease in young, adult, and aged animals. Aged dwarf hamsters infected intranasally with variant of concern (VOC) omicron BA.4 experienced more severe clinical signs, carried a higher lung virus load, and had a greater risk of succumbing to infection. Resting airway hypersensitivity was transiently increased in aged, but not young, dwarf hamsters 3-4 days post infection (dpi). Pharmacologically induced respiratory distress revealed compromised lung capacity in animals of both age groups at peak disease. Aged animals showed impaired respiratory function for 45 days, mounted a weaker antiviral response, and developed chronic pneumonia with lasting tissue damage. Treatment of acute disease with approved antivirals, paxlovid-like nirmatrelvir+ritonavir or molnupiravir, prevented long-term respiratory sequelae in aged animals. Nirmatrelvir+ritonavir fully suppressed transient respiratory distress and mediated complete survival of aged animals. This study shows a high positive correlation between host age and SARS-CoV-2 disease severity in dwarf hamsters, establishes a model for chronic pneumonia with impaired respiratory capacity in at-risk hosts, and demonstrates benefit of antiviral therapy of acute disease for long-term respiratory health. Author SummaryIn the COVID-19 pandemic, the frequency of chronic respiratory insufficiency after acute SARS-CoV-2 infection was positively linked to patient age. Roborovski dwarf hamsters recapitulate hallmarks of life-threatening COVID-19 in at-risk patients that present with acute respiratory failure and prolonged respiratory incapacitation. In this study, we monitored disease progression and lung function in young and aged dwarf hamsters infected with a VOC omicron isolate and assessed the effect of antiviral treatment on long-term lung function. We established a strong correlation between host age and SARS-CoV-2 disease severity in dwarf hamsters, identified a high propensity of aged animals to develop chronic lung inflammation, and demonstrated a long-term loss of respiratory capacity in the subset of aged animals that survived the acute infection. Antiviral treatment suppressed the development of late sequelae and preserved lung function. These results have important implications for effective SARS-CoV-2 management in aged hosts at high risk of developing severe viral pneumonia with long-term impaired lung function.