title: Murine Gammaherpesvirus 68 Pathogenesis Is Independent of Caspase-1 and Caspase-11 in Mice and Impairs Interleukin-1β Production upon Extrinsic Stimulation in Culture.
abstract: Gammaherpesviruses establish lifelong infections that are associated with the development of cancer. These viruses subvert many aspects of the innate and adaptive immune response of the host. The inflammasome, a macromolecular protein complex that controls inflammatory responses to intracellular danger signals generated by pathogens, is both activated and subverted during human gammaherpesvirus infection in culture. The impact of the inflammasome response on gammaherpesvirus replication and latency in vivo is not known. Caspase-1 is the inflammasome effector protease that cleaves the proinflammatory cytokines interleukin-1β (IL-1β) and IL-18. We infected caspase-1-deficient mice with murine gammaherpesvirus 68 (MHV68) and observed no impact on acute replication in the lung or latency and reactivation from latency in the spleen. This led us to examine the effect of viral infection on inflammasome responses in bone marrow-derived macrophages. We determined that infection of macrophages with MHV68 led to a robust interferon response but failed to activate caspase-1 or induce the secretion of IL-1β. In addition, MHV68 infection led to a reduction in IL-1β production after extrinsic lipopolysaccharide stimulation or upon coinfection with Salmonella enterica serovar Typhimurium. Interestingly, this impairment occurred at the proIL-1β transcript level and was independent of the RTA, the viral lytic replication and transcription activator. Taken together, MHV68 impairs the inflammasome response by inhibiting IL-1β production during the initial stages of infection.
  
  
  OBJECTIVE
  Gammaherpesviruses persist for the lifetime of the host. To accomplish this, they must evade recognition and clearance by the immune system. The inflammasome consists of proteins that detect foreign molecules in the cell and respond by secreting proinflammatory signaling proteins that recruit immune cells to clear the infection. Unexpectedly, we found that murine gammaherpesvirus pathogenesis was not enhanced in mice lacking caspase-1, a critical inflammasome component. This led us to investigate whether the virus actively impairs the inflammasome response. We found that the inflammasome was not activated upon macrophage cell infection with murine gammaherpesvirus 68. Infection also prevented the host cell inflammasome response to other pathogen-associated molecular patterns, indicated by reduced production of the proinflammatory cytokine IL-1β upon bacterial coinfection. Taken together, murine gammaherpesvirus impairment of the inflammatory cytokine IL-1β in macrophages identifies one mechanism by which the virus may inhibit caspase-1-dependent immune responses in the infected animal.
authors: Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, USA Molecular and Cellular Biology Program, Stony Brook University, Stony Brook, New York, USA.
authors: Brandon
authors: B
authors: Cieniewicz
authors: Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, USA Molecular and Cellular Biology Program, Stony Brook University, Stony Brook, New York, USA.
authors: Qiwen
authors: Q
authors: Dong
authors: Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
authors: Gang
authors: G
authors: Li
authors: Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
authors: James C
authors: JC
authors: Forrest
authors: Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
authors: Bryan C
authors: BC
authors: Mounce
authors: Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
authors: Vera L
authors: VL
authors: Tarakanova
authors: Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, USA Molecular and Cellular Biology Program, Stony Brook University, Stony Brook, New York, USA.
authors: Adrianus
authors: A
authors: van der Velden
authors: Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, USA Molecular and Cellular Biology Program, Stony Brook University, Stony Brook, New York, USA laurie.krug@stonybrook.edu.
authors: Laurie T
authors: LT
authors: Krug
mesh_terms: D000818:Animals; D020170:Caspase 1 / Q000172:deficiency / Q000378:metabolism*; D020169:Caspases / Q000378:metabolism*; D053471:Caspases, Initiator; D006566:Herpesviridae Infections / Q000276:immunology / Q000473:pathology*; D058847:Inflammasomes / Q000378:metabolism*; D007372:Interferons / Q000378:metabolism; D053583:Interleukin-1beta / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000276:immunology; D008168:Lung / Q000821:virology; D008264:Macrophages; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018144:Rhadinovirus / Q000276:immunology* / Q000502:physiology; D012486:Salmonella typhimurium / Q000276:immunology; D013154:Spleen / Q000821:virology; D014412:Tumor Virus Infections / Q000276:immunology / Q000473:pathology*; D014775:Virus Activation; D017735:Virus Latency; D014779:Virus Replication
chemical_list: D058847:Inflammasomes; D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D007372:Interferons; C101136:Casp4 protein, mouse; D020169:Caspases; D053471:Caspases, Initiator; D020170:Caspase 1