UNIPROT:P43026 - FACTA Search

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Query: UNIPROT:P43026 (lipopolysaccharide)
62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Interleukin-12 and -18 (IL-12 and IL-18) are known to enhance the cytotoxic T-lymphocyte response synergistically, but their precise involvement in hepatitis C virus (HCV) infection is not well known, especially for IL-18. Enzyme-linked immunosorbent assay (ELISA) was used to study the production of these cytokines in plasma and peripheral blood mononuclear cells (PBMCs) stimulated by lipopolysaccharide (LPS) of patients infected chronically with HCV before initiation of antiviral therapy. Fifty-six patients and 40 healthy controls were evaluated. Patients infected with genotype 1 or with genotype other than genotype 1 HCV had significantly a high production of plasma IL-12 compared with controls (P < 0.05). However, patients infected with genotype 1 HCV had lower levels of PBMC IL-18 than were founded in the controls (P < 0.05); plasma IL-18 also tended to be lower in this group of patients than in the controls, although nonsignificantly. Plasma IL-18 was related to hepatic histological activity (P < 0.05). The data suggest a relationship between these two cytokines and some features of HCV infection, so that their respective production in relation to the outcome of the infection deserves further study.
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PMID:Production of interleukin-18 and interleukin-12 in patients suffering from chronic hepatitis C virus infection before antiviral therapy. 1279 21

Hepatitis C virus (HCV) chronic infection is characterized by low or undetectable cellular immune responses against HCV antigens. Some studies have suggested that HCV proteins manipulate the immune system by suppressing the specific antiviral T-cell immunity. We have previously reported that the expression of HCV core and E1 proteins (CE1) in dendritic cells (DC) impairs their ability to prime T cells in vitro. We show here that immunization of mice with immature DC transduced with an adenovirus encoding HCV core and E1 antigens (AdCE1) induced lower CD4(+)- and CD8(+)-T-cell responses than immunization with DC transduced with an adenovirus encoding NS3 (AdNS3). However, no differences in the strength of the immune response were detected when animals were immunized with mature DC subsequently transduced with AdCE1 or AdNS3. According to these findings, we observed that the expression of CE1 in DC inhibited the maturation caused by tumor necrosis factor alpha or CD40L but not that induced by lipopolysaccharide. Blockade of DC maturation by CE1 was manifested by a lower expression of maturation surface markers and was associated with a reduced ability of AdCE1-transduced DC to activate CD4(+)- and CD8(+)-T-cell responses in vivo. Our results suggest that HCV CE1 proteins modulate T-cell responses by decreasing the stimulatory ability of DC in vivo via inhibition of their physiological maturation pathways. These findings are relevant for the design of therapeutic vaccination strategies in HCV-infected patients.
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PMID:Hepatitis C virus structural proteins impair dendritic cell maturation and inhibit in vivo induction of cellular immune responses. 1451 36

In chronic hepatitis B virus (HBV) infection, immune responses to hepatitis B core antigen (HBcAg) are weak. Interleukin (IL)-10 is a potent immunosuppressive cytokine which we reported recently to be secreted in response to HBcAg by peripheral blood mononuclear cells (PBMCs) from patients with chronic HBV infection or healthy controls. Using an enzyme-linked immunospot assay, we compared the ability of HBcAg to stimulate IL-10 production by PBMC with that of lipopolysaccharide (LPS), phytohaemagglutinin-P and hepatitis C virus-derived antigens in 16 patients with chronic HBV infection and six healthy controls. Frequencies of IL-10 spot-forming cells (SFC) in response to HBcAg were comparable to those obtained with LPS in patients with chronic HBV infection. Frequencies of IL-10 SFC in response to HBcAg or to LPS were significantly higher in patients with chronic HBV infection than in healthy controls. IL-10 SFC in response to HBcAg consisted of 26-35% T cells, 62-70% monocytes and less than 1% B cells in patients with chronic HBV infection. Only monocytes contributed to IL-10 production in controls. Frequencies of HBcAg stimulated IL-10 SFC representing T cells and monocytes were significantly higher in patients with elevated serum alanine aminotransferase (ALT) and detectable HBV DNA than in patients with normal ALT and undetectable HBV DNA. The potent ability of HBcAg to stimulate IL-10 production by PBMC may contribute importantly to immune tolerance toward HBV.
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PMID:Hepatitis B core antigen stimulates interleukin-10 secretion by both T cells and monocytes from peripheral blood of patients with chronic hepatitis B virus infection. 1500 79

Dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN) is a type II C-type lectin that functions as an adhesion receptor and mediates binding and internalization of pathogens such as virus (human immunodeficiency virus, hepatitis C), bacteria (Mycobacterium), fungi, and parasites. DC-SIGN expression in vivo is primarily restricted to interstitial dendritic cells (DC) and certain tissue macrophages. We now report that leukemic THP-1 cells, widely used as a model for monocyte-macrophage differentiation, express very low basal levels of DC-SIGN and that DC-SIGN expression in THP-1 cells is regulated during differentiation. Differentiation-inducing agents (phorbol ester, bryostatin) conveyed THP-1 cells with the ability to up-regulate DC-SIGN mRNA levels and cell surface expression in response to interleukin-4 (IL-4) or IL-13. DC-SIGN up-regulation required a functional JAK-STAT signaling pathway, was inhibited in the presence of lipopolysaccharide (LPS) or tumor necrosis factor-alpha (TNF-alpha), and conferred THP-1 cells with increased pathogen recognition and T cell stimulatory capabilities. The up-regulation of DC-SIGN on THP-1 cells resembles its inducible expression on monocytes and macrophages, where DC-SIGN expression is also induced by IL-4/IL-13 and negatively regulated by TNF-alpha, LPS, and vitamin D(3). These results point to THP-1 cells as a useful cellular system to characterize the pathogen-binding capabilities of DC-SIGN and to dissect the molecular mechanisms that control its regulated and tissue-specific expression in myeloid dendritic cells, and the results suggest that DC-SIGN constitutes a marker for both DC and alternatively activated macrophages.
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PMID:Regulated expression of the pathogen receptor dendritic cell-specific intercellular adhesion molecule 3 (ICAM-3)-grabbing nonintegrin in THP-1 human leukemic cells, monocytes, and macrophages. 1507 Sep 1

The current study was designed to investigate the immune status in hepatitis C virus (HCV) patients with persistently normal alanine transferase activity (ALT) (patients with normal alanine transferase). For this purpose, serum levels and lipopolysaccharide (LPS)-induced IFN-gamma, IL12 p70, IL12 p40 and IL-10 as well as NK cell activity were assayed in six patients with normal ALT, 22 HCV-infected individuals with chronic hepatitis (CH), 13 cases of liver cirrhosis (LC) and 26 age-matched controls. Cytokine production was assayed with the whole blood induction method. IFN-gamma levels were significantly lower in patients with HCV-infected chronic hepatitis and liver cirrhosis than in controls ( [Formula: see text], [Formula: see text] and [Formula: see text] pg/ml, respectively, [Formula: see text] ). However, IFN-gamma production in those individuals with normal ALT was not reduced ( [Formula: see text] pg/ml). Although variation was observed, four of the six patients showed moderate to strong IFN-gamma production. No intergroup differences were observed for IL12 p70, IL12 p40 and IL-10 production and NK cell activity. Our results suggest that preserved IFN-gamma production in patients with normal ALT, in contrast to the reduction in chronic hepatitis and liver cirrhosis, may be related to a slow rate of disease progression.
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PMID:Production of IFN-gamma and IL-12 by peripheral whole blood is maintained in hepatitis C virus patients with persistently normal alanine transferase activity; A preliminary report. 1516 29

Despite advances in treatment strategies for hepatitis C virus (HCV), a significant proportion of patients fail to achieve viral clearance following treatment with pegylated interferon (IFN)-alpha plus ribavirin. Many of these individuals show elevated levels of tumor necrosis factor (TNF)-alpha compared with normal controls, and recent data have implicated this cytokine in the negative regulation of IFN-alpha. Although a therapeutic opportunity for TNF-alpha antagonists might exist for reducing inflammation in chronic HCV disease, further exploration is required to identify the key mediators of responsiveness to IFN-alpha. In particular, the interplay should be clarified between host response factors [e.g. IFN-alpha, IFN-gamma, suppressor of cytokine signaling (SOCS), TNF-alpha and others] and pathogen-associated molecular patterns [PAMPs, e.g. lipopolysaccharide (LPS) and CpG DNA] in HCV disease; this information might guide future therapies aimed at improving IFN-alpha responsiveness.
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PMID:What is disrupting IFN-alpha's antiviral activity? 1528 83

Hepatitis C virus (HCV) is remarkably efficient at establishing persistent infection, suggesting that it has evolved one or more strategies aimed at evading the host immune response. T cell responses, including interferon-gamma production, are severely suppressed in chronic HCV patients. The HCV core protein has been previously shown to circulate in the bloodstream of HCV-infected patients and inhibit host immunity through an interaction with gC1qR. To determine the role of the HCV core-gC1qR interaction in modulation of inflammatory cytokine production, we examined interleukin (IL)-12 production, which is critical for the induction of interferon-gamma synthesis, in lipopolysaccharide-stimulated human monocyte/macrophages. We found that core protein binds the gC1qR displayed on the cell surface of monocyte/macrophages and inhibits the production of IL-12p70 upon lipopolysaccharide stimulation. This inhibition was found to be selective in that HCV core failed to affect the production of IL-6, IL-8, IL-1beta, and tumor necrosis factor alpha. In addition, suppression of IL-12 production by core protein occurred at the transcriptional level by inhibition of IL-12p40 mRNA synthesis. Importantly, core-induced inhibition of IL-12p40 mRNA synthesis resulted from impaired activation of AP-1 rather than enhanced IL-10 production. These results suggest that the HCV core-gC1qR interaction may play a pivotal role in establishing persistent infection by dampening TH1 responses.
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PMID:Hepatitis C virus core selectively suppresses interleukin-12 synthesis in human macrophages by interfering with AP-1 activation. 1529 84

The mechanisms of alcohol-induced immunosuppression include defects in innate and adaptive immune responses. Monocytes and dendritic cells (DCs) link innate and adaptive immune responses as they recognize viral antigens and induce antigen-specific T-cell activation. We investigated the effects of alcohol on antigen-presenting cell functions. Acute alcohol consumption by healthy volunteers (vodka, 2 ml/kg) resulted in significantly reduced antigen-presenting cell function of monocyte-derived DCs. Reduced allostimulatory capacity of DCs treated with alcohol in vitro correlated with decreased co-stimulatory molecule (B7.1 and B7.2) expression, as well as with reduced interleukin (IL)-12 and increased IL-10 concentrations, in mixed lymphocyte cultures. Dendritic cells recognize viral antigens in hepatitis C virus (HCV) infection, and HCV disease is accelerated in alcohol-dependent individuals. For patients with chronic HCV infection, we found reduced allostimulatory capacity of myeloid DCs. Furthermore, DC function was reduced by in vitro alcohol treatment of DCs obtained from HCV-infected patients, supporting the suggestion that viral factors and alcohol may interact to doubly suppress DC functions. We found that induction of maturation with lipopolysaccharide could not fully ameliorate the reduced DC allostimulatory capacity caused by alcohol treatment, HCV infection, or their combination. In addition, soluble factors in the supernatants obtained from mixed lymphocyte cultures containing alcohol-treated DCs or DCs obtained from HCV-infected patients could transfer inhibition of T-cell proliferation in cultures containing DCs obtained from healthy volunteers. Anti-IL-10 neutralizing antibody ameliorated the reduced mixed lymphocyte reaction containing DCs obtained from HCV-infected patients, whereas exogenous IL-12, but not anti-IL-10, treatment ameliorated the reduced T-cell proliferation induced by alcohol treatment of DCs obtained from healthy volunteers. Our results support the suggestion that both acute alcohol intake and in vitro alcohol treatment inhibit DC antigen-presenting cell function and support the hypothesis that viral factors interact with alcohol to reduce DC functions in HCV infection.
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PMID:Inhibition of antigen-presenting cell functions by alcohol: implications for hepatitis C virus infection. 1559 93

Hepatitis C virus (HCV) induces inflammatory signals, leading to hepatitis, hepatocellular carcinomas, and lymphomas. The mechanism of HCV involvement in the host's innate immune responses has not been well characterized. In this study, we analyzed expression and regulation of the entire panel of toll-like receptors (TLRs) in human B cells following HCV infection in vitro. Among all of the TLRs (TLRs 1 to 10) examined, only TLR4 showed an altered expression (a three- to sevenfold up-regulation) after HCV infection. Peripheral blood mononuclear cells from HCV-infected individuals also showed a higher expression level of TLR4 compared with those of healthy individuals. HCV infection significantly increased beta interferon (IFN-beta) and interleukin-6 (IL-6) secretion from B cells, particularly after lipopolysaccharide stimulation. The increased IFN-beta and IL-6 production was mediated by TLR4 induction, since the introduction of the small interfering RNA against TLR4 specifically inhibited the HCV-induced cytokine production. Among all of the viral proteins, only NS5A caused TLR4 induction in hepatocytes and B cells. NS5A specifically activated the promoter of the TLR4 gene in both hepatocytes and B cells. In conclusion, HCV infection directly induces TLR4 expression and thereby activates B cells, which may contribute to the host's innate immune responses.
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PMID:Hepatitis C virus induces toll-like receptor 4 expression, leading to enhanced production of beta interferon and interleukin-6. 1637 88

The role of peripheral dendritic cells (DCs) in hepatitis C virus (HCV) infection is unclear. To determine if persistent infection exerts an inhibitory pressure on HCV-specific innate responses, we analyzed DC function in blood through quantification of cell-associated HCV RNA levels in conjunction with multiparametric flow cytometry analysis of pathogen recognition receptor-induced cytokine expression. Independently of the serum viral load, fluorescence-activated cell sorter-purified total DCs had a wide range of cell-associated HCV genomic RNA copy numbers (mean log(10), 5.0 per 10(6) cells; range, 4.3 to 5.8). Here we report that for viremic patients with high viral loads in their total DCs, the myeloid DC (MDC) subset displayed impaired expression of interleukin-12 (IL-12) and tumor necrosis factor alpha (TNF-alpha) but normal IL-6 or chemokine CCL3 expression in response to poly(I:C) and lipopolysaccharide (LPS). IL-6-expressing cells from this subgroup of viremic patients demonstrated a significant increase (sixfold more) in TNF-alpha(-) IL-12(-) cell frequency compared to healthy donors (mean, 38.8% versus 6.5%; P < 0.0001), indicating a functional defect in a subpopulation of cytokine-producing MDCs ( approximately 6% of MDCs). Attenuation of poly(I:C) and LPS innate sensing was HCV RNA density dependent and did not correlate with viremia or deficits in circulating MDC frequencies in HCV-infected patients. Monocytes from these patients were functionally intact, responding normally on a per-cell basis following stimulation, independent of cell-associated HCV RNA levels. Taken together, these data indicate that detection of HCV genomic RNA in DCs and loss of function in the danger signal responsiveness of a small proportion of DCs in vivo are interrelated rather than independent phenomena.
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PMID:Poly(I:C) and lipopolysaccharide innate sensing functions of circulating human myeloid dendritic cells are affected in vivo in hepatitis C virus-infected patients. 1737 21

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