SARS-CoV-2 Reverse Genetics Reveals a Variable Infection Gradient in the Respiratory Tract

Area of Science:

• Virology
• Immunology
• Pathogenesis

Background:

• The transmission routes and reasons for varied COVID-19 severity are unclear.
• Limited cross-neutralization exists between SARS and COVID-19 patient sera.
• Understanding SARS-CoV-2 entry and spread is crucial for developing interventions.

Purpose of the Study:

• To investigate the pathogenesis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
• To explore the role of angiotensin-converting enzyme 2 (ACE2) expression in SARS-CoV-2 infection.
• To understand the initial site of infection and spread within the respiratory tract.

Main Methods:

• Generated GFP and luciferase reporter viruses for SARS-CoV-2.
• Used high-sensitivity RNA in situ hybridization to map ACE2 expression.
• Analyzed autopsied COVID-19 lung tissues and conducted pulmonary epithelial cell cultures.

Main Results:

• Highest ACE2 expression was found in the nasal cavity, decreasing down the respiratory tract.
• SARS-CoV-2 infection showed a gradient, with higher infection in proximal than distal lung cultures.
• Autopsies revealed focal lung disease and infected ciliated cells in airways and type 2 pneumocytes in alveoli.

Conclusions:

• Nasal susceptibility to SARS-CoV-2 is highlighted, suggesting potential aspiration-mediated seeding to the lungs.
• Reporter viruses and findings provide tools for studying virus-host interactions and immunity.
• This research offers insights into host susceptibility and the pathogenesis of SARS-CoV-2 infection.