title: Immune effects of R848: evidences that suggest an essential role of TLR7/8-induced, Myd88- and NF-κB-dependent signaling in the antiviral immunity of Japanese flounder (Paralichthys olivaceus).
abstract: The imidazoquinoline compound R848 is a specific agonist of toll-like receptor (TLR) 7/TLR8 that has been used as an immunostimulant in humans against viral diseases. Although R848-induced immune response has been reported in teleost fish, the relevant mechanism is not clear. In this study, we investigated the antiviral potential and the signaling pathway of R848 in a model of Japanese flounder (Paralichthys olivaceus). We found that R848 was able to inhibit the replication of megalocytivirus, stimulated the proliferation of peripheral blood leukocytes (PBL), enhanced the expression of immune genes, and reduced apoptosis of PBL. When endosomal acidification was blocked by chloroquine (CQ), R848-mediated antiviral activity and immune response were significantly reduced. Likewise, inhibition of Myd88 activation markedly impaired the pro-proliferation and anti-apoptosis effect of R848. Cellular study showed that cultured founder cells treated with R848 exhibited augmented NF-κB activity, which, however, was dramatically reduced in the presence of CQ and Myd88 inhibitor. Furthermore, when NF-κB was inactivated, the effect of R848 on cell proliferation and apoptosis was significantly decreased. Taken together, these results indicate that R848 is an immunostimulant with antiviral property in a teleost species, and that the immune response of R848 is mediated by, most likely, TLR7/TLR8 signaling pathway, in which Myd88 and NK-κB play an essential role.
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, China.
authors.forename: Zhi-Xia
authors.initials: ZX
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, China. Electronic address: lsun@qdio.ac.cn.
authors.forename: Li
authors.initials: L
authors.lastname: Sun
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D005393:Fish Diseases / Q000276:immunology / Q000378:metabolism / Q000821:virology; D005432:Flounder / Q000276:immunology / Q000821:virology; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects / Q000276:immunology; D054884:Host-Pathogen Interactions / Q000187:drug effects / Q000276:immunology; D007093:Imidazoles / Q000276:immunology / Q000494:pharmacology; D007370:Interferon Type I / Q000235:genetics; D007497:Iridoviridae / Q000276:immunology / Q000502:physiology; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D053594:Myeloid Differentiation Factor 88 / Q000276:immunology / Q000378:metabolism; D016328:NF-kappa B / Q000276:immunology / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D051199:Toll-Like Receptor 7 / Q000819:agonists / Q000276:immunology; D051200:Toll-Like Receptor 8 / Q000819:agonists / Q000276:immunology; D019562:Viral Load / Q000187:drug effects
chemical_list: D007093:Imidazoles; D007370:Interferon Type I; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; C402365:resiquimod; D051199:Toll-Like Receptor 7; D051200:Toll-Like Receptor 8
keywords: Antiviral immunity; Myd88; NK-κB; R848; Teleost; Toll-like receptor