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Updated: Nov 30, 2025
Activation and Measurement of NLRP3 Inflammasome Activity Using IL-1β in Human Monocyte-derived Dendritic Cells
Published on: May 22, 2014
Influenza A viruses limit NLRP3-NEK7-complex formation and pyroptosis in human macrophages
Inês Boal-Carvalho1, Béryl Mazel-Sanchez1, Filo Silva1
1Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland.
Abstract:
Pyroptosis is a fulminant form of macrophage cell death, contributing to release of pro-inflammatory cytokines. In humans, it depends on caspase 1/4-activation of gasdermin D and is characterized by the release of cytoplasmic content. Pathogens apply strategies to avoid or antagonize this host response. We demonstrate here that a small accessory protein (PB1-F2) of contemporary H5N1 and H3N2 influenza A viruses (IAV) curtails fulminant cell death of infected human macrophages. Infection of macrophages with a PB1-F2-deficient mutant of a contemporary IAV resulted in higher levels of caspase-1 activation, cleavage of gasdermin D, and release of LDH and IL-1β. Mechanistically, PB1-F2 limits transition of NLRP3 from its auto-repressed and closed confirmation into its active state. Consequently, interaction of a recently identified licensing kinase NEK7 with NLRP3 is diminished, which is required to initiate inflammasome assembly.
Insights
Influenza A virus protein PB1-F2 prevents excessive macrophage death during infection. This protein limits inflammasome activation, reducing the release of inflammatory molecules and cell lysis.
Area of Science:
- Immunology
- Virology
- Cell Biology
Background:
- Pyroptosis is a programmed cell death pathway in macrophages, crucial for releasing pro-inflammatory cytokines.
- Pathogens often evolve mechanisms to evade or suppress host immune responses like pyroptosis.
- Influenza A virus (IAV) infection can trigger pyroptosis, a process vital for immune defense.
Purpose of the Study:
- To investigate the role of the influenza A virus accessory protein PB1-F2 in modulating host cell death pathways.
- To elucidate the molecular mechanisms by which PB1-F2 influences pyroptosis in human macrophages.
Main Methods:
- Infection of human macrophages with wild-type and PB1-F2-deficient influenza A virus strains (H5N1, H3N2).
- Assessment of pyroptosis markers, including caspase-1 activation, gasdermin D cleavage, and release of LDH and IL-1β.
- Analysis of NLRP3 inflammasome activation and its interaction with NEK7 kinase.
Main Results:
- Influenza A virus protein PB1-F2 significantly reduces pyroptosis in infected human macrophages.
- Macrophages infected with PB1-F2-deficient IAV exhibited heightened caspase-1 activation, gasdermin D cleavage, and release of LDH and IL-1β.
- PB1-F2 was found to inhibit the transition of NLRP3 from an auto-repressed to an active state, thereby limiting NEK7 interaction and inflammasome assembly.
Conclusions:
- The influenza A virus protein PB1-F2 acts as a virulence factor by suppressing pyroptosis.
- PB1-F2's mechanism involves preventing NLRP3 inflammasome activation through impaired NEK7 licensing.
- Targeting PB1-F2 could represent a novel therapeutic strategy against influenza A virus infections.
