title: The gammaherpesviruses Kaposi's sarcoma-associated herpesvirus and murine gammaherpesvirus 68 modulate the Toll-like receptor-induced proinflammatory cytokine response.
abstract: The human pathogen Kaposi's sarcoma-associated herpesvirus (KSHV), the etiological agent of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease, establishes lifelong latency upon infection. Murine gammaherpesvirus 68 (MHV68) is a well-established model for KSHV. Toll-like receptors (TLRs) play a crucial role for the innate immune response to pathogens. Although KSHV and MHV68 are detected by TLRs, studies suggest they modulate TLR4 and TLR9 signaling, respectively. In this study, we show that in bone marrow-derived macrophages (BMDMs), MHV68 did not induce a detectable proinflammatory cytokine response. Furthermore, MHV68 abrogated the response to TLR2, -4, -7, and -9 agonists in BMDMs. Similarly to observations with MHV68, infection with KSHV efficiently inhibited TLR2 signaling in THP-1 monocytes. Using a KSHV open reading frame (ORF) library, we found that K4.2, ORF21, ORF31, and the replication and transcription activator protein (RTA)/ORF50 inhibited TLR2-dependent nuclear factor kappa B (NF-κB) activation in HEK293 TLR2-yellow fluorescent protein (YFP)- and Flag-TLR2-transfected HEK293T cells. Of the identified ORFs, RTA/ORF50 strongly downregulated TLR2 and TLR4 signaling by reducing TLR2 and TLR4 protein expression. Confocal microscopy revealed that TLR2 and TLR4 were no longer localized to the plasma membrane in cells expressing RTA/ORF50. In this study, we have shown that the gammaherpesviruses MHV68 and KSHV efficiently downmodulate TLR signaling in macrophages and have identified a novel function of RTA/ORF50 in modulation of the innate immune response.
  
  
  OBJECTIVE
  The Toll-like receptors (TLRs) are an important class of pattern recognition receptors of the innate immune system. They induce a potent proinflammatory cytokine response upon detection of a variety of pathogens. In this study, we found that the gammaherpesviruses murine gammaherpesvirus 68 (MHV68) and Kaposi's sarcoma-associated herpesvirus (KSHV) efficiently inhibit the TLR-mediated innate immune response. We further identified the KSHV-encoded replication and transcription activator protein (RTA) as a novel modulator of TLR signaling. Our data suggest that the gammaherpesviruses MHV68 and KSHV prevent activation of the innate immune response by targeting TLR signaling.
authors.affiliation: Helmholtz Centre for Infection Research, Braunschweig, Germany.
authors.forename: Kendra A
authors.initials: KA
authors.lastname: Bussey
authors.affiliation: Helmholtz Centre for Infection Research, Braunschweig, Germany.
authors.forename: Elisa
authors.initials: E
authors.lastname: Reimer
authors.affiliation: Helmholtz Centre for Infection Research, Braunschweig, Germany.
authors.forename: Helene
authors.initials: H
authors.lastname: Todt
authors.affiliation: Helmholtz Centre for Infection Research, Braunschweig, Germany.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Denker
authors.affiliation: Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany.
authors.forename: Antonio
authors.initials: A
authors.lastname: Gallo
authors.affiliation: Division of Molecular and Experimental Surgery, Department of Surgery, Universitätsklinikum Erlangen, Erlangen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Konrad
authors.affiliation: Helmholtz Centre for Infection Research, Braunschweig, Germany Institute for Laboratory Animal Science, Hannover Medical School, Hannover, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Ottinger
authors.affiliation: Research Unit Gene Vectors, Helmholtz Zentrum München-German Research Center for Environmental Health (GmbH), Munich, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Adler
authors.affiliation: Division of Molecular and Experimental Surgery, Department of Surgery, Universitätsklinikum Erlangen, Erlangen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Stürzl
authors.affiliation: Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany.
authors.forename: Wolfram
authors.initials: W
authors.lastname: Brune
authors.affiliation: Helmholtz Centre for Infection Research, Braunschweig, Germany Institute of Virology, Hannover Medical School, Hannover, Germany Melanie.Brinkmann@helmholtz-hzi.de.
authors.forename: Melanie M
authors.initials: MM
authors.lastname: Brinkmann
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000378:metabolism / Q000821:virology; D002460:Cell Line; D016207:Cytokines / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation / Q000235:genetics; D018142:Gammaherpesvirinae / Q000472:pathogenicity*; D015967:Gene Expression Regulation, Viral / Q000235:genetics; D057809:HEK293 Cells; D006566:Herpesviridae Infections / Q000235:genetics / Q000378:metabolism* / Q000821:virology; D019288:Herpesvirus 8, Human / Q000472:pathogenicity*; D006801:Humans; D007249:Inflammation / Q000235:genetics / Q000378:metabolism* / Q000821:virology*; D008264:Macrophages / Q000378:metabolism / Q000821:virology; D051379:Mice; D008810:Mice, Inbred C57BL; D009000:Monocytes / Q000378:metabolism / Q000821:virology; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D016366:Open Reading Frames / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics; D051193:Toll-Like Receptors / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism; D014775:Virus Activation / Q000235:genetics; D017735:Virus Latency / Q000235:genetics
chemical_list: D016207:Cytokines; D016328:NF-kappa B; D051193:Toll-Like Receptors; D015534:Trans-Activators; D014409:Tumor Necrosis Factor-alpha; D014764:Viral Proteins