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Heiner Wedemeyer

Publications and source records attributed to Heiner Wedemeyer.

33 records · Page 2Linked to original sources
PubMed2004

Immunoregulation of dendritic and T cells by alpha-fetoprotein in patients with hepatocellular carcinoma.

BACKGROUND/AIMS: Novel immunotherapeutic and other strategies are being explored for the treatment of hepatocellular carcinoma (HCC). Alpha-fetoprotein (AFP) may be a target antigen for immunotherapy. Little is known, however, about the immunobiology of AFP. Therefore, the impact of AFP on dendritic cells (DC), CD4+ and CD8+ T cells was studied in detail. METHODS: Immune cells from peripheral blood of 27 HCC patients were studied using FACS, ELISPOT, and proliferation assays. RESULTS: The in vitro generation, maturation, and T cell stimulatory capacity of DCs were not altered by AFP up to concentrations of 20 microg/ml. Higher AFP concentrations (> 20 microg/ml) resulted in phenotypic changes on DCs without impairing their capacity to stimulate CD4+ T cells. Frequencies and function of DCs and AFP specific T cells were not reduced in HCC patients independent on serum AFP levels. Finally, T lymphocytic infiltrations in the liver were not dependent on AFP serum levels. CONCLUSIONS: These studies clearly demonstrate that (i) DC-based immunotherapeutic approaches are a promising approach for HCC treatment and (ii) AFP-reactive T cell clones have not been deleted from the human T cell repertoire establishing AFP as a potential target for T cell based immunotherapy of HCC.

Aged↗
PubMed2004

Short-term antiviral efficacy of BILN 2061, a hepatitis C virus serine protease inhibitor, in hepatitis C genotype 1 patients.

BACKGROUND AND AIMS: Novel, potent, and well-tolerated hepatitis C virus (HCV) drugs are needed. BILN 2061 is a potent and specific inhibitor of HCV serine protease in vitro. Preclinical toxicology data and studies in healthy volunteers supported the administration of BILN 2061 to patients with HCV infection. METHODS: The antiviral efficacy, pharmacokinetics, and tolerability of 25, 200, and 500 mg BILN 2061 twice daily given as monotherapy for 2 days in 31 patients infected with chronic genotype 1 HCV infection and with minimal liver fibrosis (Ishak score of 0-2) were assessed in a placebo-controlled, double-blind pilot study. In 2 subsequent placebo-controlled studies of similar design, 200 mg BILN 2061 twice daily was administered for 2 days to 10 patients with advanced liver fibrosis (Ishak score of 3 or 4) and to 10 patients with compensated cirrhosis (Ishak score of 5 or 6). RESULTS: Viral RNA reductions of 2-3 log 10 copies/mL were achieved in most of the patients. There was a trend toward a higher number of patients receiving 500 mg BILN 2061 achieving a viral RNA reduction > or =3 log(10) copies/mL as compared with patients receiving 25 mg BILN 2061. Advanced fibrosis or compensated cirrhosis did not affect the antiviral efficacy of BILN 2061. BILN 2061 was well tolerated in all studies. CONCLUSIONS: BILN 2061 is a well-tolerated and very active compound that reduced serum viral RNA concentrations after 2 days of treatment in patients infected with genotype 1 HCV independent of the degree of fibrosis. Nevertheless, further clinical trials are on hold pending resolution of animal toxicity issues.

Antiviral Agents↗
PubMed2004

Hepatitis C virus mutation affects proteasomal epitope processing.

The high incidence of hepatitis C virus (HCV) persistence raises the question of how HCV interferes with host immune responses. Studying a single-source HCV outbreak, we identified an HCV mutation that impaired correct carboxyterminal cleavage of an immunodominant HLA-A2-restricted CD8 cell epitope that is frequently recognized by recovered patients. The mutation, a conservative HCV nonstructural protein 3 (NS3) tyrosine to phenylalanine substitution, was absent in 54 clones of the infectious source, but present in 15/21 (71%) HLA-A2-positive and in 11/24 (46%) HLA-A2-negative patients with chronic hepatitis C. In order to analyze whether the mutation affected the processing of the HLA-A2-restricted CD8 cell epitope, mutant and wild-type NS3 polypeptides were digested in vitro with 20S constitutive proteasomes and with immunoproteasomes. The presence of the mutation resulted in impaired carboxyterminal cleavage of the epitope. In order to analyze whether impaired epitope processing affected T cell priming in vivo, HLA-A2-transgenic mice were infected with vaccinia viruses encoding either wild-type or mutant HCV NS3. The mutant induced fewer epitope-specific, IFN-gamma;-producing and fewer tetramer(+) cells than the wild type. These data demonstrate how a conservative mutation in the flanking region of an HCV epitope impairs the induction of epitope-specific CD8(+) T cells and reveal a mechanism that may contribute to viral sequence evolution in infected patients.

Amino Acid Sequence↗
PubMed2003

Inhibition of hepatitis B virus replication in vivo by nucleoside analogues and siRNA.

BACKGROUND & AIMS: Hepatitis B virus (HBV) causes acute and chronic infections that may result in severe liver diseases. Animal models to study new treatment options in vivo have several drawbacks. Therefore, we were interested to establish a new small animal model in which HBV replication and especially new treatment options can be studied easily. METHODS: Naked DNA of an HBV replication competent vector was transferred via tail vein into NMRI mice. HBV replication was studied in serum and liver of the animals. HBV replication was modulated by treatment through siRNA and nucleoside analogues. RESULTS: Tail vein transfer of a HBV replication competent construct resulted in expression of HBV-specific transcripts in the liver, and up to 10% of hepatocytes became HBc- and HBsAg-positive. HBeAg, HBsAg, and viral DNA could be detected in the serum of the animals, followed by the induction of HBV-specific cellular immune responses. Nucleoside treatment of the mice resulted in reduced polymerase activity in the liver. Additionally, siRNA transfer in the animals led to a significant reduction of HBsAg and/or eventually HBeAg expression, which was dependent on the localization of the complementary sequence in the HBV genome. CONCLUSIONS: We have established a mouse model to study HBV replication and to investigate new and existing treatment approaches in vivo. Interestingly, siRNA seems a promising innovative treatment option to inhibit specifically HBV replication in vivo.

Adenine↗
PubMed2002

Peptide-beta2-microglobulin-MHC fusion molecules bind antigen-specific T cells and can be used for multivalent MHC-Ig complexes.

Recombinant soluble MHC molecules are widely used for visualization, activation and inhibition of antigen-specific immune responses. Using a genetic approach, we have generated two novel peptide-beta2-microglobulin-MHC constructs. We have linked the MHC molecule with the peptide of interest, without limiting the recognition by the cognate TCR. This molecule can also be joined with the IgG heavy chain resulting in a dimeric MHC-Ig fusion protein. These molecules bind antigen-specific T cells with high specificity and sensitivity, therefore, providing a valuable tool for detection as well as enrichment of antigen-specific T cells.

Animals↗
PubMed2002

Impaired effector function of hepatitis C virus-specific CD8+ T cells in chronic hepatitis C virus infection.

The cellular immune response contributes to clearance of hepatitis C virus (HCV) and persists for decades after recovery from infection. The immunological basis for the inefficiency of the cellular immune response in chronically infected persons is not known. Here, we used four HLA-A2 tetramers, specific for two HCV core and two HCV NS3 epitopes, to investigate at the single-cell level effector function and phenotype of HCV-specific CD8+ T cells in 20 chronically infected and 12 long-term recovered patients. Overall, HCV-specific, tetramer+ T cells were more frequently found in PBMCs of chronically infected patients than in those of recovered patients. However, when compared with HCV-tetramer+ T cells of recovered patients, they displayed an impaired proliferative capacity. As a result of the impaired proliferative capacity, HCV-specific T cell lines derived from chronically infected patients displayed less peptide-specific cytotoxicity than those from recovered patients. In addition, proliferation and ex vivo IFN-gamma production of HCV-tetramer+ cells, but not influenza-virus-specific T cells, were defective in chronically infected patients and could not be restored by in vitro stimulation with peptide and IL-2. At least three distinct phenotypes of HCV-specific CD8+ T cells were identified and associated with certain functional characteristics. In addition, impairment of proliferative, cytokine, and cytotoxic effector functions of tetramer+ T cells in viremic patients was associated with weak ex vivo HCV-specific CD4+ T cell responses. Thus, the defective functions of HCV-specific CD8+ T cells might contribute to viral persistence in chronically infected patients, and knowledge on their reversibility may facilitate the development of immunotherapeutic vaccines.

Adult↗
PubMed2002

Treatment of chronic hepatitis C with PEGylated interferon and ribavirin.

Treatment with interferon alfa combined with ribavirin is successful in approximately 40% to 45% of patients with chronic hepatitis C viral infection (HCV). However, response rates are disappointing in patients who are difficult to treat, such as those infected with HCV genotype 1, high viral load, or advanced liver fibrosis. In addition, low tolerability and significant side effects of therapy frequently lead to dose reduction and treatment discontinuation, decreasing response rates further. Thus, investigation of new treatment options and innovations for chronic HCV infection are vital. This review describes recent advances in the treatment of HCV infection with PEGylated interferon (interferon modified with polyethylene glycol [PEG] ) combined with ribavirin.

Antiviral Agents↗
PubMed2002

Polyethylene glycol-interferon: current status in hepatitis C virus therapy.

In chronic hepatitis C infection, combination therapy with interferon (IFN)-alpha and ribavirin leads to sustained virological response rates of 40-45%. However, treatment outcome is still disappointing in patients infected with hepatitis C virus (HCV) genotype 1, high viral load or advanced liver fibrosis. Due to significant side-effects of therapy, dose reductions and discontinuations of therapy are frequent and lead to further decreased response rates. The development of modified IFN is the latest step to improve treatment options for chronic hepatitis C. Conjugation of the polymer polyethylene glycol (PEG) to IFN extends half-life in comparison to conventional IFN and thereby increases antiviral activity. It allows once-weekly dosing and increases sustained response rates without changing the safety profile. The PEG-IFN monotherapy is twice as effective as IFN-alpha three times weekly. The combination of PEG-interferon and ribavirin improves the overall sustained response rates to 54-56% and represents the new standard therapy for patients with chronic hepatitis C infection in most patients.

Antiviral Agents↗
PubMed2002

Autoimmune hepatitis and overlap syndromes.

Autoimmune hepatitis is a well-established chronic liver disease. It primarily affects women, is characterized by circulating autoantibodies and elevated gammaglobulins and is associated with extrahepatic immune-mediated syndromes. Treatment regimens have remained unchanged for a number of years because of the high efficacy of steroid monotherapy, or combination therapy of azathioprine and steroids. In approximately 90% of patients remission of the disease is reached by medical therapy, which is usually administered lifelong because long-term remission after drug withdrawal is achieved in only 17% of patients. In 10% of patients treatment failure is observed. The challenge of remission induction involves the use of transplant immunosuppressants such as cyclosporine, mycophenolate moffetil, and tacrolimus. The challenge of maintenance therapy minimizing steroid side-effects involves the evaluation of topical steroids and the use of azathioprine monotherapy. Overlap syndromes occur in approximately 20% of autoimmune liver diseases. The diagnosis is broadly based on serological, biochemical, clinical and histological parameters. Most common are the overlap of autoimmune hepatitis and primary biliary cirrhosis, as well as autoimmune hepatitis with primary sclerosing cholangitis. These yet incompletely defined syndromes are an important differential diagnosis in the difficult-to-treat patient with autoimmune hepatitis.

Hepatitis, Autoimmune↗