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Sabine Mihm

Publications and source records attributed to Sabine Mihm.

8 recordsLinked to original sources
PubMed2006

Interleukin-29 uses a type 1 interferon-like program to promote antiviral responses in human hepatocytes.

Interleukin-28A (IL-28A), IL-28B and IL-29 are a family of class II cytokines that stimulate antiviral responses through a heterodimeric receptor that is distinct from the type I interferon (IFN) receptor. To better understand how this newly described family of cytokines regulates the antiviral state, we compared various cellular responses elicited by IL-29 and IFN-alpha. Here we show that these cytokines stimulate similar patterns of signal transducer and activator of transcription 1 (STAT-1), -2, -3, and -5 phosphorylation and nearly identical patterns of gene expression when analyzed in two distinct cell types by microarray analysis. Interestingly, the IL-29 receptor is preferentially expressed on primary hepatocytes within normal liver and pegylated forms of IL-29 and IFN-alpha induced equivalent 2'5' oligoadenylate synthetase (OAS) and MX1 gene expression in this cell type. Pegylated IL-29 also produced a significant reduction in human hepatitis B and hepatitis C viral load in vitro and reduced the cytopathic effect caused by the fully replicating flavivirus, West Nile virus. In conclusion, IL-29 and IFN-alpha stimulate identical antiviral responses despite their utilization of different receptors. This fact, combined with significant receptor expression in hepatitis virus-infected livers, suggests that IL-29 may have therapeutic value against chronic viral hepatitis in human patients.

Animals↗
PubMed2006

Interferon regulatory factor-1 promoter polymorphism and the outcome of hepatitis C virus infection.

OBJECTIVE: Interferon-alpha (IFN-alpha), an important mediator for the host's innate antiviral defense system, has been approved for the treatment of persistent viral infections. We investigated whether two functional polymorphisms in genes involved in IFN-alpha signaling and effector functions are associated with the natural outcome of hepatitis C virus (HCV) infection and the responsiveness of chronic hepatitis C patients to IFN-alpha therapy. METHODS: Forty-four individuals who had resolved HCV infection spontaneously and 147 patients who developed chronic hepatitis C were analyzed for functional single nucleotide polymorphisms in the promoter regions of the interferon regulatory factor-1 (IRF-1) and myxovirus resistance protein-1 (MxA) genes at positions -300 and -88, respectively. RESULTS: With regard to -300 IRF-1 or -88 MxA genotype distributions or minor allele frequencies, individuals who spontaneously resolved the infection displayed no significant difference compared with those with chronic infections. Among patients with chronic infections, however, the -300AA IRF-1 genotype, associated with a higher IRF-1 transcriptional activity, was absent in patients with chronic HCV genotype 3a infections, with one exception. In contrast to expectations, -300AA IRF-1 individuals with HCV genotype 3a infection were not represented in higher numbers among those with self-limited infections. Regarding IFN-alpha therapy, -300AA IRF-1 chronic hepatitis C genotype 1 patients tend to respond more often than those with the other IRF-1 genotypes. CONCLUSION: Our findings suggest the possibility that the -300AA IRF-1 genotype is associated with outcome in patients with HCV genotype 3 infection. In addition, in HCV genotype-1-infected patients, this genotype appears associated with response to therapy.

Adult↗
PubMed2005

Treatment of genotype 2 and 3 chronic hepatitis C virus-infected patients.

AIM: Before pegylated interferon alpha (IFN) was introduced for the therapy of chronic hepatitis C virus (HCV)-induced hepatitis, conventional thrice weekly IFN therapy was supplemented by ribavirin. Also, at that time, higher and more frequent doses of IFN were expected to be more effective than the standard regimen of 3 MU thrice weekly. As ribavirin significantly increases side effects and negatively influences the quality of life particularly in young patients, we started a prospective non-randomized study with a daily IFN-2a monotherapy as an initial treatment for chronic hepatitis C. METHODS: Forty-six consecutive chronic HCV-infected patients received 3 MU IFN-2a per day as an initial treatment. Patients with genotype 2 or 3 (n = 12) were treated for 24 wk, and patients with genotypes other than 2 or 3 (n = 34) for 48 wk. Treatment outcome was followed up for 48 wk after the end of treatment (EOT). Virological response was defined as the absence of detectable serum HCV-RNA. Patients without virological response at 12 wk after the start of treatment received low-dose ribavirin (10 mg(kg/d)) additionally. RESULTS: During treatment, three genotype 3 patients were excluded from the study due to incompliance. The remaining patients (n = 9) infected with genotype 2 or 3 showed an initial virological response rate of 100%. Six patients (66.7%) were still found to be virus-free at the end of follow-up period. In these patients, initial virological response was evident already after 2 wk of treatment. In contrast, initial virological response occurred first after 4 wk of treatment in the three patients who relapsed (33.3%). In comparison, patients infected with genotypes other than 2 or 3 (n = 34) showed an initial virological response rate of only 23.5% (n = 8), and even in combination with ribavirin a sustained virological response (SVR) rate of only 11.8% (n = 4) could be achieved. CONCLUSION: In chronic HCV-infected patients with genotype 2 or 3, a SVR can be expected after 24 wk of daily dose IFN-2a treatment without ribavirin, if initial virological response develops early. This finding is worth to be confirmed in a prospective randomized study with pegylated IFN.

Adult↗
PubMed2004

Interferon type I gene expression in chronic hepatitis C.

Hepatitis C virus (HCV) frequently causes chronic liver disease. The cause of viral persistence might be an inappropriate type I interferon (IFN) induction. To analyze the host's IFN response in chronic hepatitis C, we measured the transcription level of type I IFN genes as well as type I IFN-regulated genes in liver tissue and corresponding blood samples from patients with chronic hepatitis C, nonviral liver diseases, and a suspected but later excluded liver disease. Competitive and real-time RT-PCR assays were used to quantify the messenger RNA (mRNA) levels of all known IFN-alpha, IFN-beta, and IFN-lambda genes and those of some IFN-regulated genes. We failed to detect any hepatic type I IFN mRNA induction, although liver tissue of chronic hepatitis C patients contained high numbers of some type I IFN-inducible effector mRNA molecules. Analysis of peripheral blood samples, however, showed a clear type I IFN induction. Parallel experiments employing HCV replicon cell lines revealed that replication of HCV RNA is not sufficient to induce any type I IFN nor to induce directly type I IFN-regulated genes such as MxA. In conclusion, our data provide evidence for the absence of an induction of type I IFN genes by HCV in the human liver and argue for a further development of type I IFN-based therapies.

Adolescent↗
PubMed2003

Ribavirin inhibits DNA, RNA, and protein synthesis in PHA-stimulated human peripheral blood mononuclear cells: possible explanation for therapeutic efficacy in patients with chronic HCV infection.

The treatment of choice for patients infected chronically with HCV is the combination of IFN-alpha and ribavirin. Monotherapy with ribavirin leads to a clinical and histological improvement, but its exact mechanism of action is unknown. Therefore, the effect of ribavirin on synthesis of inflammatory cytokines and on apoptosis in stimulated peripheral blood mononuclear cells (PBMCs) was investigated. PBMCs were isolated from the blood of HCV infected patients and from healthy volunteers. The effect of ribavirin on IFN-gamma and IL-1beta release in the supernatant of unstimulated and phytohemagglutinin (PHA) stimulated PBMCs was investigated by enzyme linked immunosorbent assay (ELISA). The effect on total DNA, RNA, and protein synthesis was analyzed by measurement of 3H-thymidine, 3H-uridine and 3H-leucine incorporation into cellular macromolecules. Ribavirin led to a dose-dependent decrease of the IFN-gamma but an increase of IL-1beta release into the supernatant of PHA-stimulated PBMCs. At the same time, a dose-dependent decrease of total DNA, RNA, and protein synthesis in cultures of PHA-stimulated PBMCs was demonstrated. These effects could be compensated by the addition of equimolar amounts of guanosine. The rate of apoptotic CD45+ and CD14+ cells in PBMCs cultures increased in a dose-dependent manner. Our data suggest that ribavirin administration to chronically HCV-infected patients could lead to a decrease of the synthesis of proinflammatory cytokines (e.g., IFN-gamma) by an inhibition of total DNA-, RNA-, and protein-synthesis and by induction of apoptosis in the cells of the inflammatory infiltrate. Furthermore, ribavirin could influence the synthesis of viral particles in the hepatocytes.

Antimetabolites↗
PubMed2003

Expression of the chemokine IP-10 correlates with the accumulation of hepatic IFN-gamma and IL-18 mRNA in chronic hepatitis C but not in hepatitis B.

The pathogenesis of hepatitis C virus-induced chronic liver disease is still poorly understood. Previous studies revealed enhanced hepatic expression of the Th1 prototype cytokine IFN-gamma in individuals with chronic hepatitis C. In accordance with several animal models of experimentally induced hepatitis, a Th1 lymphocyte driven inflammatory process, which involves newly infiltrated as well as resident monocytes/macrophages, has been proposed. An involvement of the interferon-gamma-inducible chemokine IP-10, which is chemoattractive for stimulated Th1 cells and monocytes, is also suggested. Using an HBV transgenic mouse model, a reduction of hepatic infiltration and liver disease was achieved recently by administration of antibodies directed against the interferon-gamma-inducible chemokine Mig and against IP-10. In the present study, expression of IP-10 was investigated both in serum and in the liver of patients with chronic hepatitis C and hepatitis B. Patients with liver diseases of non-viral etiologies served as controls. IP-10 expression was highest in hepatitis C. In chronic hepatitis C, but not in chronic hepatitis B nor in liver disorders unrelated to viral infections, IP-10 expression was strongly correlated with the amount of transcripts for IFN-gamma and to the amount of transcripts for the constitutively expressed macrophage derived cytokine IL-18. Hepatic inflammatory activity, however, was found to be associated more closely with IFN-gamma than with IP-10 or IL-18 mRNA expression. The data support the hypothesis that IP-10 is responsible for the recruitment of Th cells and monocytes in chronic hepatitis C, and suggest that its role in chronic hepatitis B is less determining. Moreover, they deliver additional support for the view that IFN-gamma still has to be considered as a mediator that determines the outcome of inflammation, e.g., via its ability to activate IL-18 expressing cells and to initiate a delayed type hypersensitivity reaction.

Adolescent↗
PubMed2002

Interferon-gamma inhibits replication of subgenomic and genomic hepatitis C virus RNAs.

Persistent infection with hepatitis C virus (HCV) is a major cause of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. All treatments known so far rely on the antiviral activity of interferon alfa (IFN-alpha) that is given alone or in combination with ribavirin. Unfortunately, only a fraction of the patients clear the virus during therapy and for those who do not respond there is currently no alternative treatment. Selectable subgenomic HCV RNAs (replicons) have been recently used to investigate the effect of IFN-alpha on HCV replication. However, it has not yet been analyzed whether other cytokines also play a role in the innate immune response against HCV. Here we show that IFN-gamma inhibits protein synthesis and RNA replication of subgenomic and genomic HCV replicons. We further show that the inhibitory action of IFN-gamma does not rely on the production of nitric oxide or the depletion of tryptophan. In conclusion, our results suggest that cytotoxic T cells and natural killer cells may contribute to HCV clearance not only by cell killing but also by producing IFN-gamma, thereby enhancing the intracellular inhibition of viral replication.

Hepacivirus↗