Listeria monocytogenes engineered to activate the Nlrc4 inflammasome are severely attenuated and are poor inducers of protective immunity

Proc Natl Acad Sci U S A. 2011 Jul 26;108(30):12419-24. doi: 10.1073/pnas.1019041108. Epub 2011 Jul 11.

Abstract

Inflammasomes are intracellular multiprotein signaling complexes that activate Caspase-1, leading to the cleavage and secretion of IL-1β and IL-18, and ultimately host cell death. Inflammasome activation is a common cellular response to infection; however, the consequences of inflammasome activation during acute infection and in the development of long-term protective immunity is not well understood. To investigate the role of the inflammasome in vivo, we engineered a strain of Listeria monocytogenes that ectopically expresses Legionella pneumophila flagellin, a potent activator of the Nlrc4 inflammasome. Compared with wild-type L. monocytogenes, strains that ectopically secreted flagellin induced robust host cell death and IL-1β secretion. These strains were highly attenuated both in bone marrow-derived macrophages and in vivo compared with wild-type L. monocytogenes. Attenuation in vivo was dependent on Nlrc4, but independent of IL-1β/IL-18 or neutrophil activity. L. monocytogenes strains that activated the inflammasome generated significantly less protective immunity, a phenotype that correlated with decreased induction of antigen-specific T cells. Our data suggest that avoidance of inflammasome activation is a critical virulence strategy for intracellular pathogens, and that activation of the inflammasome leads to decreased long-term protective immunity and diminished T-cell responses.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Apoptosis / immunology
  • Apoptosis Regulatory Proteins / deficiency
  • Apoptosis Regulatory Proteins / genetics*
  • Apoptosis Regulatory Proteins / immunology*
  • CARD Signaling Adaptor Proteins
  • Calcium-Binding Proteins / deficiency
  • Calcium-Binding Proteins / genetics*
  • Calcium-Binding Proteins / immunology*
  • Cytoskeletal Proteins / immunology
  • Female
  • Flagellin / genetics
  • Flagellin / immunology
  • Genetic Engineering
  • Host-Pathogen Interactions / immunology
  • Immunity, Cellular
  • Immunity, Innate
  • Immunization
  • Inflammasomes / genetics*
  • Inflammasomes / immunology*
  • Legionella pneumophila / genetics
  • Legionella pneumophila / immunology
  • Listeria monocytogenes / genetics*
  • Listeria monocytogenes / immunology*
  • Listeria monocytogenes / pathogenicity
  • Listeriosis / immunology
  • Listeriosis / prevention & control
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Neutrophils / immunology
  • T-Lymphocytes / immunology
  • Virulence / genetics
  • Virulence / immunology

Substances

  • Apoptosis Regulatory Proteins
  • CARD Signaling Adaptor Proteins
  • Calcium-Binding Proteins
  • Cytoskeletal Proteins
  • Inflammasomes
  • Ipaf protein, mouse
  • Pycard protein, mouse
  • Flagellin