Complement Activation Contributes to Severe Acute Respiratory Syndrome Coronavirus Pathogenesis.

Area of Science:

• Immunology
• Virology
• Pathogenesis

Background:

• Severe acute respiratory syndrome coronavirus (SARS-CoV) infection can lead to acute respiratory distress syndrome (ARDS), characterized by immune-driven pathologies.
• The complement system is a key component of the innate immune response, crucial for host defense against various pathogens.

Purpose of the Study:

• To investigate the role of the complement system in SARS-CoV-induced lung pathology and disease severity.
• To determine if complement activation contributes to protective or detrimental outcomes during SARS-CoV infection.

Main Methods:

• Utilized a mouse model of SARS-CoV infection (C57BL/6J mice).
• Employed mice deficient in C3 (C3^-/-) to assess the impact of complement absence on disease progression.
• Quantified viral loads, immune cell infiltration (neutrophils, monocytes), respiratory dysfunction, weight loss, cytokine/chemokine levels, and lung pathology.

Main Results:

• SARS-CoV-infected C3^-/- mice showed significantly reduced weight loss and respiratory dysfunction compared to controls, despite equivalent lung viral loads.
• Absence of C3 led to markedly fewer neutrophils and inflammatory monocytes in the lungs.
• Reduced lung pathology and lower systemic and local cytokine/chemokine levels were observed in C3^-/- mice.

Conclusions:

• The complement system acts as a significant mediator of SARS-CoV-induced disease, promoting inflammation rather than controlling viral replication.
• Complement activation drives a systemic inflammatory response, contributing to the immunopathology of SARS-CoV infection.
• Inhibiting complement signaling presents a potential therapeutic avenue for managing SARS-CoV disease.