Hepatitis C core and nonstructural 3 proteins trigger toll-like receptor 2-mediated pathways and inflammatory activation
Department of Medicine, Division of Gastroenterology; Department of Medicine, Division of Infectious Diseases and Immunology; Department of Molecular Genetics and Microbiology
Medical Subject Headings
Animals; Cell Line; Hepacivirus; Hepatitis C; Hepatitis C, Chronic; Humans; Inflammation; Kidney; Membrane Glycoproteins; Mice; Mice, Inbred C57BL; Mice, Knockout; Monocytes; Receptors, Cell Surface; Recombinant Proteins; Toll-Like Receptor 2; Toll-Like Receptors; Transfection; Viral Core Proteins; Viral Nonstructural Proteins
Gastroenterology | Immunology and Infectious Disease | Microbiology | Molecular genetics
BACKGROUND AND AIMS: Recent evidence suggests that toll-like receptors (TLRs) recognize certain viruses. We reported that hepatitis C virus (HCV) core and nonstructural 3 (NS3) proteins activate inflammatory pathways in monocytes. The aim of this study was to investigate the role of TLRs in innate immune cell activation by core and NS3 proteins.
METHODS: Human monocytes, human embryonic kidney cells transfected with TLR2, and peritoneal macrophages from TLR2, MyD88 knockout, and wild-type mice were studied to determine intracellular signaling and proinflammatory cytokine induction by HCV proteins.
RESULTS: HCV core and NS3 proteins triggered inflammatory cell activation via the pattern recognition receptor TLR2 and failed to activate macrophages from TLR2 or MyD88-deficient mice. HCV core and NS3 induced interleukin (IL)-1 receptor-associated kinase (IRAK) activity, phosphorylation of p38, extracellular regulated (ERK), and c-jun N-terminal (JNK) kinases and induced AP-1 activation. Activation of nuclear factor-kappaB by core and NS3 was associated with increased IkappaBalpha phosphorylation. TLR2-mediated cell activation was dependent on the conformation of core and NS3 proteins and required sequences in the regions of aa 2-122 in core and aa 1450-1643 in NS3. Although cellular uptake of core and NS3 proteins was independent of TLR2 expression, cell activation required TLR2. HCV core protein and TLR2 showed intracellular colocalization. The hyper-elevated TNF-alpha induction by TLR2 ligands in monocytes of HCV-infected patients was not due to increased TLR2 expression.
CONCLUSIONS: HCV core and NS3 proteins trigger inflammatory pathways via TLR2 that may affect viral recognition and contribute to activation of the innate immune system.
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Citation: Gastroenterology. 2004 Nov;127(5):1513-24.