title: Dual role for inflammasome sensors NLRP1 and NLRP3 in murine resistance to Toxoplasma gondii.
abstract: Induction of immunity that limits Toxoplasma gondii infection in mice is critically dependent on the activation of the innate immune response. In this study, we investigated the role of cytoplasmic nucleotide-binding domain and leucine-rich repeat containing a pyrin domain (NLRP) inflammasome sensors during acute toxoplasmosis in mice. We show that in vitro Toxoplasma infection of murine bone marrow-derived macrophages activates the NLRP3 inflammasome, resulting in the rapid production and cleavage of interleukin-1β (IL-1β), with no measurable cleavage of IL-18 and no pyroptosis. Paradoxically, Toxoplasma-infected mice produced large quantities of IL-18 but had no measurable IL-1β in their serum. Infection of mice deficient in NLRP3, caspase-1/11, IL-1R, or the inflammasome adaptor protein ASC led to decreased levels of circulating IL-18, increased parasite replication, and death. Interestingly, mice deficient in NLRP1 also displayed increased parasite loads and acute mortality. Using mice deficient in IL-18 and IL-18R, we show that this cytokine plays an important role in limiting parasite replication to promote murine survival. Our findings reveal T. gondii as a novel activator of the NLRP1 and NLRP3 inflammasomes in vivo and establish a role for these sensors in host resistance to toxoplasmosis.
  
  
  OBJECTIVE
  Inflammasomes are multiprotein complexes that are a major component of the innate immune system. They contain "sensor" proteins that are responsible for detecting various microbial and environmental danger signals and function by activating caspase-1, an enzyme that mediates cleavage and release of the proinflammatory cytokines interleukin-1β (IL-1β) and IL-18. Toxoplasma gondii is a highly successful protozoan parasite capable of infecting a wide range of host species that have variable levels of resistance. We report here that T. gondii is a novel activator of the NLRP1 and NLRP3 inflammasomes in vivo and establish a role for these sensors in host resistance to toxoplasmosis. Using mice deficient in IL-18 and IL-18R, we show that the IL-18 cytokine plays a pivotal role by limiting parasite replication to promote murine survival.
authors.forename: Gezahegn
authors.initials: G
authors.lastname: Gorfu
authors.forename: Kimberly M
authors.initials: KM
authors.lastname: Cirelli
authors.forename: Mariane B
authors.initials: MB
authors.lastname: Melo
authors.forename: Katrin
authors.initials: K
authors.lastname: Mayer-Barber
authors.forename: Devorah
authors.initials: D
authors.lastname: Crown
authors.forename: Beverly H
authors.initials: BH
authors.lastname: Koller
authors.forename: Seth
authors.initials: S
authors.lastname: Masters
authors.forename: Alan
authors.initials: A
authors.lastname: Sher
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Leppla
authors.forename: Mahtab
authors.initials: M
authors.lastname: Moayeri
authors.forename: Jeroen P J
authors.initials: JP
authors.lastname: Saeij
authors.forename: Michael E
authors.initials: ME
authors.lastname: Grigg
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000172:deficiency / Q000276:immunology*; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000172:deficiency / Q000276:immunology*; D002352:Carrier Proteins / Q000235:genetics / Q000276:immunology*; D060467:Disease Resistance; D005260:Female; D058847:Inflammasomes / Q000276:immunology*; D008264:Macrophages / Q000276:immunology / Q000469:parasitology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D059208:Parasite Load; D016019:Survival Analysis; D014122:Toxoplasma / Q000276:immunology*; D014124:Toxoplasmosis, Animal / Q000276:immunology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; D058847:Inflammasomes; C529636:NALP1 protein, mouse; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C492716:Nlrp3 protein, mouse