cGAS Restricts PRRSV Replication by Sensing the mtDNA to Increase the cGAMP Activity

Area of Science:

• Immunology
• Virology
• Molecular Biology

Background:

• Porcine reproductive and respiratory syndrome virus (PRRSV) causes significant global economic losses in the swine industry.
• Innate immune responses, particularly RNA receptors, are crucial for detecting PRRSV.
• The role of DNA sensors, like cyclic GMP-AMP synthase (cGAS), in PRRSV infection remains largely unknown.

Purpose of the Study:

• To investigate the function of the innate immune DNA sensor cGAS during PRRSV infection.
• To elucidate the molecular mechanisms by which cGAS influences PRRSV replication and innate immunity.

Main Methods:

• Western blot analysis to assess protein expression.
• Virus titer assays to quantify viral load.
• Mitochondrial DNA (mtDNA) detection and co-localization studies with cGAS.

Main Results:

• cGAS overexpression suppressed PRRSV replication, while cGAS knockout enhanced viral titer and nucleocapsid protein expression.
• PRRSV infection induced mitochondrial damage, leading to cytoplasmic leakage of mtDNA.
• Cytoplasmic mtDNA co-localized with cGAS, increasing cyclic GMP-AMP (cGAMP) activity and demonstrating an anti-PRRSV effect.

Conclusions:

• cGAS restricts PRRSV replication by sensing leaked mtDNA in the cytoplasm, thereby increasing cGAMP activity.
• This study reveals a novel mechanism for cGAS-STING pathway involvement in RNA virus infection.
• Findings provide insights into innate immunity against PRRSV and potential therapeutic targets.