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Biomedical subjects

Thomas Berg

Publications and source records attributed to Thomas Berg.

At least 19 recordsLinked to original sources
PubMed2006

Persistence of a sexually transmitted highly resistant HIV-1: pol quasispecies evolution over 33 months in the absence of treatment.

The evolution of a sexually transmitted multiresistant HIV-1 in a linked transmission chain was followed for 33 months to assess its potential to persist in the absence of treatment. The multiresistant HIV reverted slowly to wild type in reverse transcriptase (positions 44, 67, 74, 118) rendering the virus only susceptible to lamivudine/emtricitabine. Persistence of the replication-competent resistant HIV increases its potential to spread further and strengthens the importance of resistance testing in newly infected patients.

Adult↗
PubMed2006

Gender-dependent association of CTLA4 polymorphisms with resolution of hepatitis C virus infection.

BACKGROUND/AIMS: A vigorous T-cell response is essential for the resolution of HCV infection. It is modified by co-stimulatory molecules that attenuate T-lymphocyte responses by binding to CTLA4. We investigated whether CTLA4 single nucleotide polymorphisms are associated with the resolution of infection or with the course of disease. METHODS: We enrolled 127 individuals with self-limited and 947 patients with chronic HCV infection, of whom 560 were treated with interferon-alpha-based therapies, and 200 healthy controls. We analyzed CTLA4 polymorphisms -318C>T and +49A>G by melting curve analysis and reconstructed haplotypes. RESULTS: CTLA4 haplotypes were distributed differently between men but not women with self-limited and chronic infection (p=0.043) but were not predictive of the stage of fibrosis in chronic carriers. Haplotypes were distributed differently between male but not female end-of-treatment responders and non-responders (p=0.025). The influence of CTLA4 haplotypes was more pronounced in "hard-to-treat" situations, i.e., treatment with interferon-alpha monotherapy or infection with HCV genotypes 1/4. Logistic regression analysis confirmed gender-specific risk factors for a virological non-response. CONCLUSIONS: CTLA4 polymorphisms are associated with the resolution of HCV infection. This study underlines the role of an efficient T-cell response in the clearance of HCV and sheds light on a gender-dependent difference of immune regulation.

Adolescent↗
PubMed2006

Combination of tenofovir and lamivudine versus tenofovir after lamivudine failure for therapy of hepatitis B in HIV-coinfection.

OBJECTIVE: At present sequential monotherapy for chronic hepatitis B with hepatitis B virus (HBV)-polymerase inhibitors is clinical practice. It is unknown to date whether combination therapy with lamivudine plus tenofovir could be superior to sequential therapy with tenofovir after the occurrence of lamivudine resistance. METHODS: We conducted a multicenter, 1: 2 matched pair analysis comparing patients with HBV/HIV-coinfection starting an antiretroviral regimen including tenofovir plus lamivudine with patients who had highly replicative, lamivudine resistant HBe-antigen positive chronic hepatitis B and started with tenofovir as the only active HBV polymerase inhibitor subsequent to lamivudine. RESULTS: At baseline patients on tenofovir plus lamivudine (n = 25) had a median HBV DNA of 5.9 x 10(7) copies/ml compared to 1.37 x 10(8) copies/ml in the tenofovir arm (n = 50; P = 0.32). A sustained undetectable HBV DNA < 1000 copies/ml was achieved in 19/25 (76%) patients on tenofovir plus lamivudine and in 42/50 (84%) on tenofovir (P = 0.53). A loss of HBe-antigen was observed in 9/25 (36%) patients on tenofovir plus lamivudine and in 12/50 (24%) patients on tenofovir (P = 0.29). HBs-antigen loss was found in 1/25 (4%) and 3/50 (6%) patients. CONCLUSIONS: In this cohort of HBV/HIV-coinfected individuals, full HBV DNA suppression was achieved in the majority of patients independent of treatment allocation. Loss of HBe- and HBs-antigen was not different between the two study arms. Over a median treatment period of 116 weeks tenofovir was as effective as tenofovir plus lamivudine. Longer treatment periods may be needed to evaluate potential benefits of first-line combination therapy for chronic hepatitis B.

Adenine↗
PubMed2006

Induction of interleukin-6 by hepatitis C virus core protein in hepatitis C-associated mixed cryoglobulinemia and B-cell non-Hodgkin's lymphoma.

PURPOSE: Chronic hepatitis C carries the risk to develop mixed cryoglobulinemia (MC) and B-cell non-Hodgkin's lymphoma (B-NHL), possibly because viral antigens stimulate the host's inflammatory response via extracellular pattern recognition receptors (PRR). To clarify this issue, we studied whether recognition of hepatitis C virus (HCV) proteins by PRR is involved in the pathogenesis of HCV-associated MC or B-NHL. EXPERIMENTAL DESIGN: Peripheral blood mononuclear cells of patients with HCV-associated B-NHL (n = 12), MC (n = 14), uncomplicated hepatitis C (n = 12), and healthy volunteers (n = 12) were incubated with the recombinant HCV proteins E2, core, and NS3 to study induction of cytokine production, stimulation of B-cell proliferation, and immunoglobulin secretion. In addition, serum levels of interleukin-6 (IL-6) were measured by ELISA. RESULTS: HCV core was the only studied protein, which induced production of IL-6 and IL-8 in CD14(+) cells. IL-6 induction was mediated via Toll-like receptor 2 (TLR2) and lead to increased B-cell proliferation in vitro. TLR2 expression on monocytes and IL-6 serum concentrations were increased in all groups of HCV-infected patients compared with healthy controls and were highest in MC (P < 0.05). CONCLUSIONS: Increased secretion of IL-6 via stimulation of TLR2 by HCV core protein may play a role in the pathogenesis of hepatitis C-associated MC and B-NHL.

Adult↗
PubMed2006

Treatment of patients with recurrent hepatitis C after liver transplantation with peginterferon alfa-2B plus ribavirin.

BACKGROUND: Recurrent hepatitis C virus (HCV) after liver transplantation (OLT) is a major cause of graft loss in HCV-positive patients. In this study, we evaluated the efficacy and safety of pegylated interferon alfa-2b (peginterferon) and ribavirin treatment for recurrent HCV after OLT and analyzed the influence of antiviral treatment on the histological course of recurrent hepatitis. METHODS: Twenty-five patients with recurrent HCV (genotype 1 n=20 and 2-4 n=5) received peginterferon (1 mg/kg/weekly) and ribavirin (600 mg) for 48 weeks. Viral load prior to treatment was below 1,000,000 (IU/ml) in 11 of 25 patients. Sustained antiviral response was defined as undetectable HCV-RNA in serum 6 months after stopping of therapy. All patients underwent liver biopsy prior to treatment and after 72 weeks. RESULTS: Seventeen of 25 patients became HCV-RNA-negative after treatment (68%). Sustained virologic response (SVR) was achieved in 9/25 (36%) patients. Liver specimen showed increase of fibrosis from 1.7 to 2.0 within 72 weeks. Side effects like neutropenia (60%) and anemia (36%) were treated with G-CSF, erythropoietin, and dose reduction of peginterferon and ribavirin. CONCLUSIONS: The use of peginterferon is safe and effective in patients with recurrent HCV. Treatment of side effects, especially neutropenia or anemia, helped to maintain antiviral therapy. Despite a viral response of 68% during treatment, the patients showed further progress of recurrent hepatitis in liver specimen.

Adult↗
PubMed2006

Coupling of imaging NEXAFS with secondary ion mass spectrometry for the chemical and isotopic analysis of presolar cosmic grains.

We present first results of the combination of imaging photoemission electron spectroscopy with imaging mass spectrometry. Imaging NEXAFS was combined with TOF-SIMS in order to perform a spatially resolved chemical and isotopic analysis of microscopic grain samples. Imaging NEXAFS was used for the nondestructive lateral characterization of mineral phases prior to isotopically resolved mass analysis by imaging TOF-SIMS. This novel approach was demonstrated by performing a chemical and isotopic analysis of the rare presolar grain fraction present in the Murchison meteorite.

Journal Article↗
PubMed2006

Enzyme replacement therapy in alpha-mannosidosis guinea-pigs.

alpha-Mannosidosis is a lysosomal storage disorder caused by deficient activity of lysosomal alpha-mannosidase and is characterised by massive accumulation of mannose-containing oligosaccharides in affected individuals. Patients develop behaviour and learning difficulties, skeletal abnormalities, immune deficiency and hearing impairment. Disease in alpha-mannosidosis guinea-pigs resembles the clinical, histopathological, biochemical and molecular features of the human disease. We have used the guinea-pig model to investigate efficacy of enzyme replacement therapy as a treatment for alpha-mannosidosis. Intravenous recombinant human lysosomal alpha-mannosidase, administered at a dose of 1mg/kg, was cleared from circulation with a half-life of 53 h, with significant enzyme activity (1.4x normal levels) detected in circulation one week post-injection. alpha-Mannosidase administered to alpha-mannosidosis guinea-pigs at 1mg/kg (onset at birth or approximately 30 days) and 10mg/kg (at birth) was distributed widely amongst tissues, including to capillary depleted brain. By monitoring with tandem mass spectrometry, enzyme replacement therapy was found to be effective in reducing stored substrates in peripheral tissues at both dose rates, and in brain by up to 39% at the 10mg/kg dose, compared with untreated alpha-mannosidosis controls. Reductions of up to 60% of urinary mannose containing oligosaccharides were also observed. No histological improvements were seen in the brain at either dose, however marked decreases in lysosomal vacuolation in liver, kidney, spleen and endocrine pancreas, as well as a significant reduction in trigeminal ganglion neurons were observed. Multiple injections of 1mg/kg recombinant enzyme in alpha-mannosidosis guinea-pigs induced a very rapid humoral immune response precluding long-term intravenous treatment.

Animals↗
PubMed2006

A degradation-sensitive anionic trypsinogen (PRSS2) variant protects against chronic pancreatitis.

Chronic pancreatitis is a common inflammatory disease of the pancreas. Mutations in the genes encoding cationic trypsinogen (PRSS1) and the pancreatic secretory trypsin inhibitor (SPINK1) are associated with chronic pancreatitis. Because increased proteolytic activity owing to mutated PRSS1 enhances the risk for chronic pancreatitis, mutations in the gene encoding anionic trypsinogen (PRSS2) may also predispose to disease. Here we analyzed PRSS2 in individuals with chronic pancreatitis and controls and found, to our surprise, that a variant of codon 191 (G191R) is overrepresented in control subjects: G191R was present in 220/6,459 (3.4%) controls but in only 32/2,466 (1.3%) affected individuals (odds ratio 0.37; P = 1.1 x 10(-8)). Upon activation by enterokinase or trypsin, purified recombinant G191R protein showed a complete loss of trypsin activity owing to the introduction of a new tryptic cleavage site that renders the enzyme hypersensitive to autocatalytic proteolysis. In conclusion, the G191R variant of PRSS2 mitigates intrapancreatic trypsin activity and thereby protects against chronic pancreatitis.

Base Sequence↗
PubMed2006

Early monotherapy with pegylated interferon alpha-2b for acute hepatitis C infection: the HEP-NET acute-HCV-II study.

Early treatment of acute hepatitis C with interferon alpha-2b for 24 weeks prevents chronic infection in almost all patients. Because pegylated interferons have replaced conventional interferon in the therapy of chronic hepatitis C, the aim of this study was to analyze the efficacy of an early treatment of acute hepatitis C with peginterferon alpha-2b. Between February 2001 and February 2004, 89 individuals with acute HCV infection were recruited at 53 different centers in Germany. Patients received 1.5 microg/kg peginterferon alpha-2b for 24 weeks; treatment was initiated after a median of 76 days after infection (range 14-150). End-of-treatment response and sustained virological response were defined as undetectable HCV RNA at the end of therapy and after 24 weeks of follow-up, respectively. In the total study population, virological response was 82% at the end of treatment and 71% at the end of follow-up. Of 89 individuals, 65 (73%) were adherent to therapy, receiving 80% of the interferon dosage within 80% of the scheduled treatment duration. End-of-treatment and sustained virological response rates in this subpopulation were 94% and 89%, respectively. A maximum alanine aminotransferase level of more than 500 U/L prior to therapy was the only factor associated with successful treatment. In conclusion, in acute HCV infection, early treatment with peginterferon alpha-2b leads to high virological response rates in individuals who are adherent to treatment. The high number of dropouts underlines the importance of thorough patient selection and close monitoring during therapy. Thus, future studies should identify factors predicting spontaneous viral clearance to avoid unnecessary therapy.

Acute Disease↗
PubMed2006

Tenofovir for patients with lamivudine-resistant hepatitis B virus (HBV) infection and high HBV DNA level during adefovir therapy.

Incomplete virological response to adefovir dipivoxil (ADV) has been observed in patients with lamivudine-resistant hepatitis B virus (HBV) infection and may be associated with developing resistance and disease progression. We therefore investigated whether the efficacy of viral suppression could be improved by replacing ADV with tenofovir disoproxil fumarate (TDF). Twenty patients with chronic HBV infection (18 HBeAg+), viral breakthrough during lamivudine therapy, and persistent viral replication (>10(4) copies/mL) after 15 months of ADV monotherapy (range 4-28 months) were treated with TDF 300 mg daily and were retrospectively analyzed. A screening for nucleoside/nucleotide analogue resistance mutations within the HBV polymerase gene was performed in all patients by direct sequencing. Within a median of 3.5 months, application of TDF led to undetectable HBV DNA in 19 of 20 patients, as demonstrated by suppression of HBV DNA below the detection limit of 400 copies/mL. Initially elevated ALT levels had normalized in 10 of 14 patients by the end of follow-up (median 12 months, range 3-24 months). Four patients lost HBeAg, after 3, 4, 5, and 16 months, and one patient seroconverted to anti-HBs after 16 months of TDF therapy. Lamivudine-associated mutations (rtV173L, rtL180M, rtM204V/I) could be detected in 6 patients at baseline of TDF, but this obviously did not influence the response. ADV-resistant mutations were not detected. No side effects were reported. In conclusion, these preliminary observations strongly suggest that TDF might be a highly effective rescue drug for HBV-infected patients with altered responsiveness to treatment with lamivudine and ADV.

Adenine↗
PubMed2006

Influence of donor/recipient HLA-matching on outcome and recurrence of hepatitis C after liver transplantation.

The aim of this study was to analyze the effect of human leukocyte antigen (HLA) matching on outcome, severity of recurrent hepatitis C and risk of rejection in hepatitis C positive patients after liver transplantation (LT). In a retrospective analysis, 165 liver transplants in patients positive for hepatitis C virus (HCV) with complete donor/recipient HLA typing were reviewed for recurrence of HCV and outcome. Follow-up ranged from 1 to 158 months (median, 74.5 months). Immunosuppression consisted of either cyclosporine-A- or tacrolimus-based quadruple induction therapy including or an interleukin 2-receptor antagonist. Protocol liver biopsies were performed after 1, 3, 5, 7, and 10 years and staged according to the Scheuer scoring system. The overall 1-, 5-, and 10-year graft survival figures were 81.8%, 69.11 and 62%, respectively. There was no correlation in the study population between number of HLA mismatches and graft survival. The number of rejection episodes increased significantly in patients with more HLA mismatches (P < 0.05). In contrast to this, the fibrosis progression was significantly faster in patients with 0-5 HLA mismatches compared to patients with a complete HLA mismatch. In conclusion, HLA matching did not influence graft survival in patients after LT for end-stage HCV infection, however, despite less rejection episodes, the fibrosis progression increased in patients with less HLA mismatches within the first year after LT.

Brain Death↗
PubMed2006

A structural account of phonological paraphasias.

The aim of this study is to develop a partial theory of phonological paraphasias which has some cross-syndrome and cross-linguistic validity. It is based on the distinction between content and structural units and emphasizes the role of the latter. The notion of structure holds the key to an understanding of the differences among the following three types of data: slips of the tongue, slips of the pen (defined as errors committed by healthy, competent adults), and paraphasias. A comparison of these three data types reveals that slips of the pen and paraphasias display striking similarities whereas slips of the tongue stand apart. This pattern emerges very clearly in an analysis of nine empirical effects all of which are found to be of a structural nature. On the basis of these results, it is argued that both the written output of normals and the oral output of aphasics are generated under a reduced structural representation (i.e., weak activation of structural nodes). However, the reasons for the diminished sensitivity to structure are not the same in the two modalities. While the impoverished structural representation is a likely consequence of the relatively slow production rate in writing, it may stem from an impaired transmission of activation among structural nodes in aphasia. By contrast, the normal speaking process occurs under the sway of a full-fledged structural representation. Hence, slips of the tongue are highly sensitive to structural effects.

Aphasia↗
PubMed2006

Extended treatment duration for hepatitis C virus type 1: comparing 48 versus 72 weeks of peginterferon-alfa-2a plus ribavirin.

BACKGROUND & AIMS: The treatment of patients infected with hepatitis C virus (HCV) type 1 remains a challenge necessitating innovative strategies to improve treatment outcome. The extension of treatment duration beyond 48 weeks is one possible strategy to address this problem. METHODS: The efficacy and safety of 48 weeks (group A, N = 230) vs 72 weeks (group B, N = 225) of treatment with pegylated-interferon-alfa-2a (180 microg/wk) plus ribavirin (800 mg/day) were studied in treatment-naive patients with HCV type 1 infection. On-treatment and sustained virologic response (SVR) 24 weeks after stopping treatment was assessed by qualitative reverse-transcription polymerase chain reaction (sensitivity 50 IU/mL). RESULTS: Overall, no significant differences could be observed in the treatment outcome between both groups. End-of-treatment and SVR rates in groups A and B were 71% vs 63% and 53% vs 54%, respectively. Patients with undetectable HCV-RNA levels already at weeks 4 and 12 had excellent SVR rates ranging from 76% to 84% regardless of treatment group, whereas patients shown to be still HCV-RNA positive at week 12 achieved significantly higher SVR rates when treated for 72 instead of 48 weeks (29% vs 17%, P = .040). A particular benefit from extended treatment duration was seen in patients with low-level viremia (<6000 IU/mL) at week 12. The frequency and intensity of adverse events was similar between the 2 groups. CONCLUSIONS: Extended treatment duration generally is not recommended in HCV type 1 infection and should be reserved only for patients with slow virologic response defined as HCV-RNA positive at week 12 but negative at week 24.

Adult↗
PubMed2006

Demonstration of PDC-E1 subunits as major antigens in the complement-fixing fraction M4 and re-evaluation of PDC-E1-specific antibodies in PBC patients.

BACKGROUND: Primary biliary cirrhosis (PBC) is characterized by the presence of antimitochondrial antibodies (AMA). Autoantibodies specific for the mitochondrial M4 antigen can be detected by a complement fixation test (CFT) but not by immunoblotting. The aim of this study was to elucidate the identity of the M4 antigen. PATIENTS AND METHODS: M4 proteins were purified by affinity chromatography using IgG fractions of PBC marker sera being CFT positive (n=5) or negative (n=5) and identified by Western blotting, silver staining and sequence analysis. Further, a cohort of 57 PBC patients was tested for the reactivity to M4 and pyruvate dehydrogenase complex (PDC). RESULTS: Two AMA patterns of the marker sera were visualized: CFT-positive sera were defined as PDC-E2(+)/E1(+) and the CFT-negative sera as PDC-E2(+)/E1(-). The major proteins in the M4 fraction could be related to the PDC-E1 subunits. A clear-cut association between anti-M4 reactivity in the CFT and the reactivity to both PDC subunits could also be documented in the cohort of 57 PBC patients showing anti-PDC-E1alpha and E1beta antibodies at a frequency of 74% and 67%. CONCLUSIONS: CFT reactivity against M4 antigens could be preferentially identified as a reaction against PDC-E1. As PDC-E1 subunits as compared with PDC-E2 lack lipoyl-binding sites, they probably have to be considered as an independent and important target.

Aged↗
PubMed2005

Assistance of microbial glycolipid antigen processing by CD1e.

Complexes between CD1 molecules and self or microbial glycolipids represent important immunogenic ligands for specific subsets of T cells. However, the function of one of the CD1 family members, CD1e, has yet to be determined. Here, we show that the mycobacterial antigens hexamannosylated phosphatidyl-myo-inositols (PIM6) stimulate CD1b-restricted T cells only after partial digestion of the oligomannose moiety by lysosomal alpha-mannosidase and that soluble CD1e is required for this processing. Furthermore, recombinant CD1e was able to bind glycolipids and assist in the digestion of PIM6. We propose that, through this form of glycolipid editing, CD1e helps expand the repertoire of glycolipidic T cell antigens to optimize antimicrobial immune responses.

Acylation↗
PubMed2005

Prevention of hepatitis B recurrence after liver transplantation.

The reults of orthotopic liver transplantation (OLT) for hepatitis B virus (HBV) related liver disease are significantly influenced by the HBV recurrence rate. Complete eradication of hepatitis B is rarely possible after liver transplantation and hepatic and extrahepatic reservoirs are a continuous latent source of HBV recurrence. Therefore an adequate prophylaxis is mandatory. By introduction of long term passive immunoprophylaxis the recurrence rate could be markedly reduced and survival rates significantly improved. Due to the approval of antiviral drugs, especially lamivudine as the first approved antiviral agent against HBV, new prophylactic options, including combination prophylaxis, have been introduced. This modern antiviral managemant improved the outcome of hepatitis B patients after liver transplantation. The Results after OLT are nowadays reported to be as good or in a recent UNOS database report even better than in non-HBV patients. The type of recommended prophylaxis has undergone modifications within the last years and is still subject to changes due to the ongoing development of antiviral agents. In addition, due to high costs of hepatitis immunoglobulin alternatives such as prophylaxis with nucleos(t)ide analogues or vaccination are increasingly investigated. In the following, current strategies of reinfection prophylaxis and future perspectives are reviewed.

Antiviral Agents↗