Poxvirus dsDNA genomes differentially activate AIM2 or NLRP3 inflammasomes in human primary cells

Area of Science:

• Immunology
• Molecular Biology
• Virology

Background:

• The innate immune system detects cytosolic DNA as a sign of infection.
• Studies on DNA sensing and inflammasome activation have primarily used mouse models and cell lines.
• Human primary cell responses to cytosolic DNA remain less understood.

Purpose of the Study:

• To investigate inflammasome activation in human primary cells upon cytosolic DNA detection.
• To identify the specific inflammasome sensors involved in DNA-triggered responses in different human cell types.
• To develop tools for dissecting inflammasome assembly.

Main Methods:

• Utilized engineered viruses encoding a caspase-1 reporter (caspase-1^CARD-EGFP).
• Generated and characterized nanobodies against the AIM2 inflammasome sensor.
• Employed engineered vaccinia virus expressing bivalent AIM2 nanobodies in primary human macrophages, keratinocytes, and monocytes.

Main Results:

• Released viral genomes from vaccinia and monkeypox viruses induced robust inflammasome assembly in human primary cells.
• AIM2-specific nanobodies inhibited AIM2 inflammasome assembly by blocking Pyrin domain polymerization.
• AIM2 nucleated inflammasomes in primary human macrophages and keratinocytes.
• CD14⁺ monocytes were found to assemble NLRP3 inflammasomes in response to viral DNA.

Conclusions:

• DNA-triggered inflammasome activation is regulated in a cell-type-specific manner in humans, with AIM2 and NLRP3 acting as key sensors.
• This resolves discrepancies between mouse and human inflammasome activation studies.
• AIM2-specific nanobodies provide valuable tools for studying and potentially targeting AIM2 inflammasome-mediated diseases.