title: EBV latent membrane protein 1 is a negative regulator of TLR9.
abstract: EBV infects most of the human population and is associated with a number of human diseases including cancers. Moreover, evasion of the immune system and chronic infection is an essential step for EBV-associated diseases. In this paper, we show that EBV can alter the regulation and expression of TLRs, the key effector molecules of the innate immune response. EBV infection of human primary B cells resulted in the inhibition of TLR9 functionality. Stimulation of TLR9 on primary B cells led to the production of IL-6, TNF-α, and IgG, which was inhibited in cells infected with EBV. The virus exerts its inhibitory function by decreasing TLR9 mRNA and protein levels. This event was observed at early time points after EBV infection of primary cells, as well as in an immortalized lymphoblastoid cell line. We determined that the EBV oncoprotein latent membrane protein 1 (LMP1) is a strong inhibitor of TLR9 transcription. Overexpression of LMP1 in B cells reduced TLR9 promoter activity, mRNA, and protein levels. LMP1 mutants altered in activating the NF-κB pathway prevented TLR9 promoter deregulation. Blocking the NF-κB pathway recovered TLR9 promoter activity. Mutating the NF-κB cis element on the TLR9 promoter restored luciferase transcription in the presence of LMP1. Finally, deletion of the LMP1 gene in the EBV genome abolished the ability of the virus to induce TLR9 downregulation. Our study describes a mechanism used by EBV to suppress the host immune response by deregulating the TLR9 transcript through LMP1-mediated NF-κB activation.
authors.affiliation: International Agency for Research on Cancer, Lyon, France.
authors.forename: Ikbal
authors.initials: I
authors.lastname: Fathallah
authors.forename: Peggy
authors.initials: P
authors.lastname: Parroche
authors.forename: Henri
authors.initials: H
authors.lastname: Gruffat
authors.forename: Claudia
authors.initials: C
authors.lastname: Zannetti
authors.forename: Hanna
authors.initials: H
authors.lastname: Johansson
authors.forename: Jiping
authors.initials: J
authors.lastname: Yue
authors.forename: Evelyn
authors.initials: E
authors.lastname: Manet
authors.forename: Massimo
authors.initials: M
authors.lastname: Tommasino
authors.forename: Bakary S
authors.initials: BS
authors.lastname: Sylla
authors.forename: Uzma A
authors.initials: UA
authors.lastname: Hasan
mesh_terms: D001402:B-Lymphocytes / Q000276:immunology / Q000821:virology; D002460:Cell Line; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000276:immunology*; D020031:Epstein-Barr Virus Infections / Q000276:immunology; D004854:Herpesvirus 4, Human / Q000276:immunology*; D006801:Humans; D057131:Immune Evasion; D007113:Immunity, Innate; D009856:Oncogene Proteins, Viral / Q000502:physiology; D051217:Toll-Like Receptor 9 / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics*; D014158:Transcription, Genetic / Q000276:immunology; D014763:Viral Matrix Proteins / Q000502:physiology*
chemical_list: C037662:EBV-associated membrane antigen, Epstein-Barr virus; D009856:Oncogene Proteins, Viral; C495371:TLR9 protein, human; D051217:Toll-Like Receptor 9; D014763:Viral Matrix Proteins