Induction of the Inflammasome by the SARS-CoV-2 Accessory Protein ORF9b, Abrogated by Small-Molecule ORF9b...

Area of Science:

• Virology
• Immunology
• Drug Discovery

Background:

• Viral accessory proteins are key to immune evasion and inflammatory pathogenesis.
• The SARS-CoV-2 accessory protein ORF9b's role in inflammasome activation was previously unclear.

Purpose of the Study:

• To investigate the role of SARS-CoV-2 accessory proteins in inflammasome activation.
• To develop small molecules targeting ORF9b to counteract its inflammatory effects.

Main Methods:

• Activation of caspase-1 in A549 and THP-1 cells by SARS-CoV-2 accessory proteins.
• In silico design and experimental validation of small molecules inhibiting ORF9b homodimerization.
• Assessment of cytokine release and type I interferon signaling restoration.

Main Results:

• ORF9b, unlike other SARS-CoV-2 accessory proteins, potently activated inflammasome-dependent caspase-1.
• Designed small molecules inhibited ORF9b homodimerization, mitochondrial eviction, and caspase-1 activation.
• These compounds restored type I interferon signaling and reduced cytokine release.

Conclusions:

• ORF9b is a potent activator of the inflammasome, contributing to SARS-CoV-2 pathogenesis.
• First-in-class small molecules targeting ORF9b show therapeutic potential for mitigating coronavirus-induced inflammation and immune suppression.