title: Activation of nucleotide oligomerization domain 2 (NOD2) by human cytomegalovirus initiates innate immune responses and restricts virus replication.
abstract: Nucleotide-binding oligomerization domain 2 (NOD2) is an important innate immune sensor of bacterial pathogens. Its induction results in activation of the classic NF-κB pathway and alternative pathways including type I IFN and autophagy. Although the importance of NOD2 in recognizing RNA viruses has recently been identified, its role in sensing DNA viruses has not been studied. We report that infection with human cytomegalovirus (HCMV) results in significant induction of NOD2 expression, beginning as early as 2 hours post infection and increasing steadily 24 hours post infection and afterwards. Infection with human herpesvirus 1 and 2 does not induce NOD2 expression. While the HCMV-encoded glycoprotein B is not required for NOD2 induction, a replication competent virion is necessary. Lentivirus-based NOD2 knockdown in human foreskin fibroblasts (HFFs) and U373 glioma cells leads to enhanced HCMV replication along with decreased levels of interferon beta (IFN-β) and the pro-inflammatory cytokine, IL8. NOD2 induction in HCMV-infected cells activates downstream NF-κB and interferon pathways supported by reduced nuclear localization of NF-κB and pIRF3 in NOD2 knockdown HFFs. Stable overexpression of NOD2 in HFFs restricts HCMV replication in association with increased levels of IFN-β and IL8. Similarly, transient overexpression of NOD2 in U373 cells or its downstream kinase, RIPK2, results in decreased HCMV replication and enhanced cytokine responses. However, overexpression of a mutant NOD2, 3020insC, associated with severe Crohn's disease, results in enhanced HCMV replication and decreased levels of IFN-β in U373 cells. These results show for the first time that NOD2 plays a significant role in HCMV replication and may provide a model for studies of HCMV recognition by the host cell and HCMV colitis in Crohn's disease.
authors.affiliation: Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Arun
authors.initials: A
authors.lastname: Kapoor
authors.affiliation: Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, Maryland, United States of America.
authors.forename: Michael
authors.initials: M
authors.lastname: Forman
authors.affiliation: Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Ravit
authors.initials: R
authors.lastname: Arav-Boger
mesh_terms: D002460:Cell Line; D016207:Cytokines / Q000378:metabolism; D003587:Cytomegalovirus / Q000502:physiology* / Q000528:radiation effects; D003586:Cytomegalovirus Infections / Q000276:immunology; D005347:Fibroblasts / Q000378:metabolism / Q000528:radiation effects / Q000821:virology; D055785:Gene Knockdown Techniques; D006564:Herpesviridae / Q000502:physiology / Q000528:radiation effects; D006801:Humans; D007113:Immunity, Innate / Q000528:radiation effects; D018836:Inflammation Mediators / Q000378:metabolism; D007372:Interferons / Q000378:metabolism; D007700:Kinetics; D008297:Male; D050505:Mutant Proteins / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D053473:Nod2 Signaling Adaptor Protein / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014466:Ultraviolet Rays; D014759:Viral Envelope Proteins / Q000378:metabolism; D038301:Virus Inactivation / Q000528:radiation effects; D014779:Virus Replication / Q000502:physiology* / Q000528:radiation effects
chemical_list: D016207:Cytokines; D018836:Inflammation Mediators; D050505:Mutant Proteins; D016328:NF-kappa B; C429018:NOD2 protein, human; D053473:Nod2 Signaling Adaptor Protein; D012333:RNA, Messenger; D014759:Viral Envelope Proteins; C040495:glycoprotein B, Simplexvirus; D007372:Interferons