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Rainer Haas

Publications and source records attributed to Rainer Haas.

86 records · Page 5Linked to original sources
PubMed2002

Fast and reliable titration of recombinant adeno-associated virus type-2 using quantitative real-time PCR.

In this study, a quantitative real-time PCR (qPCR) was developed to determine genomic rAAV-2 titers using the Light-Cycler technology. Since the CMV promoter is the most commonly used promoter in gene therapeutic approaches, primers were designed which hybridize with the human CMV promoter sequence. PCR products were detected by the addition of SYBR green. qPCR of a 5 log spanning serial dilution of the vector plasmid containing one CMV promoter per plasmid molecule yielded a high amplification efficiency of 1.99 per cycle. To quantify the copy number of viral genomes, the qPCR curves of adeno-associated virus type 2 (AAV-2) samples were related to a standard curve assessed by the 5 log spanning serial vector plasmid dilution (0.01-100 pg DNA). For validation of the method, rAAV-2 preparations were analyzed by a standard method and qPCR in parallel. As standard method, flow cytometry was used for titration of infectious viral particles on HeLa cells using the Enhanced Green Fluorescent Protein as a marker. A significant correlation was found between the results obtained by flow cytometry and the results from the qPCR over a 5 log range (r=0.85, P<0.0001). The mean ratio between infectious rAAV-2 particles titrated via flow cytometry and genomic copies of rAAV-2 measured by qPCR of the same sample was 1:253. The higher titers found by qPCR might be due to multiple transduction of a single cell or to non-infectious particles generated during rAAV-2 preparation. In conclusion, qPCR is a fast and reliable method for determination of rAAV-2 titers and might be a powerful tool for standardization of rAAV-2 preparations particularly in the context of clinical studies.

Cytomegalovirus↗
PubMed2002

Reliable engraftment, low toxicity, and durable remissions following allogeneic blood stem cell transplantation with minimal conditioning.

OBJECTIVE: Allogeneic blood stem cell transplantation (BSCT) can cure patients with hematologic malignancies by high-dose chemotherapy and allogeneic graft-vs-tumor (GvT) reactions. To avoid high-dose conditioning and evaluate engraftment, toxicity, and GvT reactions, we treated a group of high-risk patients with a minimal intensive conditioning regimen followed by allogeneic BSCT. MATERIALS AND METHODS: Thirty-four patients with lymphoma (11), myeloma (10), chronic myeloid leukemia (4), myelodysplastic syndrome (5), and acute myeloid leukemia (4) were treated with fludarabine (3 x 30 mg/m(2)) and 200 cGy total-body irradiation followed by the infusion of peripheral blood stem cells from related (28) or unrelated (6) donors. Cyclosporine or tacrolimus and mycophenolate mofetile were given posttransplant. Most patients had advanced disease, were intensively pretreated, and had contraindications against conventional myeloablative transplantation. RESULTS: Thirty-two patients (94%) had engraftment of donor cells. Patients with lymphatic malignancies developed complete donor chimerism significantly faster than patients with myeloid malignancies (p < 0.05). Clinical responses were observed in 16 of 27 patients (59%) who had active disease at transplantation. Of 7 patients who were treated in remission, 5 remain free of disease. After a median follow-up of 325 days (range 100-844) 22 patients are alive (65%, 14 CR, 4 PR, 4 PD). Two patients (6%) died of treatment-related complications and 10 patients (29%) died of progressive disease. Acute graft-vs-host-disease (GvHD) of grade II or more developed in 17 patients (50%). Chronic GvHD is present in 10 of 22 patients (45%) who are alive beyond day 100. CONCLUSIONS: Toxicity and survival in this group of high-risk patients are superior to those expected with conventional allogeneic transplantation. GvT reactions frequently occur in conjunction with GvHD and can induce durable remissions in patients with advanced hematologic malignancies.

Adult↗
PubMed2002

Grb2 is a key mediator of helicobacter pylori CagA protein activities.

CagA delivered from Helicobacter pylori into gastric epithelial cells undergoes tyrosine phosphorylation and induces host cell morphological changes. Here we show that CagA can interact with Grb2 both in vitro and in vivo, which results in the activation of the Ras/MEK/ERK pathway and leads to cell scattering as well as proliferation. Importantly, this ability of CagA is independent from the tyrosine phosphorylation, which occurs within the five repeated EPIYA sequences (PY region) of CagA. However, the PY region appears to be indispensable for the Grb2 binding and induction of the cellular responses. Thus, intracellular CagA via its binding to Grb2 may act as a transducer for stimulating growth factor-like downstream signals which lead to cell morphological changes and proliferation, the causes of H. pylori-induced gastric hyperplasia.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Inhibition of angiogenesis in vitro by alphav integrin-directed antisense oligonucleotides.

The integrin alpha v beta 3 plays a central role in angiogenesis. In this study, we used antisense oligodeoxyribonucleotides (ONs) directed against the alpha v subunit of alpha v beta 3 to inhibit integrin expression. Ten ON sequences, which were selected by systematic alignment of computer-predicted secondary structures of alpha v mRNA, were transfected into human umbilical vein endothelial cells (HUVECs). Following stimulation by PMA, five antisense ONs significantly inhibited alpha v mRNA and protein expression in activated HUVEC at a concentration of 0.05 mciroM with complete prevention of PMA-induced alpha v up-regulation by the most potent antisense ON. Inhibition of alpha v expression was associated with significant inhibition of migration of HUVEC by 28% and had no effect on proliferation and apoptosis. Moreover, transfection of antisense ON inhibited the formation of tube-like structures of HUVEC in Matrigel by 44%. In a cell culture model of angiogenesis consisting of a co-culture of endothelial cells with fibroblasts, transfection of antisense ONs resulted in an inhibition of tube formation of 61%. In conclusion, alpha v antisense ONs are potent inhibitors of angiogenesis in vitro. They might, therefore, be a therapeutic alternative to antagonists, which directly bind to alpha v integrins, and might be useful for the treatment of malignant tumors and hematological malignancies.

Apoptosis↗
PubMed2002

Activation of Helicobacter pylori CagA by tyrosine phosphorylation is essential for dephosphorylation of host cell proteins in gastric epithelial cells.

Helicobacter pylori type I strains harbour the cag pathogenicity island (cag-PAI), a 37 kb sequence,which encodes the components of a type IV secretion system. CagA, the first identified effector protein of the cag-PAI, is translocated into eukaryotic cells and tyrosine phosphorylated (CagAP-tyr) by a host cell tyrosine kinase. Translocation of CagA induces the dephosphorylation of a set of phosphorylated host cell proteins of unknown identity. CagA proteins of independent H. pylori strains vary in sequence and thus in the number and composition of putative tyrosine phosphorylation motifs (TPMs). The CagA protein of H. pylori strain J99 (CagAJ99) does not carry any of three putative tyrosine phosphorylation motifs (TPM-A, TPM-B or TPM-C) predicted by the MOTIF algorithm in CagA proteins. CagA,n is not tyrosine phosphorylated and is inactive in the dephosphorylation of host cell proteins. By site-specific mutagenesis,we introduced a TPM-C into CagA,. by replacing a single lysine with a tyrosine. This slight modification resulted in tyrosine phosphorylation of CagAJ99 and host cell protein dephosphorylation. In contrast, the removal of the indigenous TPM-C from CagAP12 did not abolish its tyrosine phosphorylation, suggesting that further phosphorylated sites are present in CagAP12. By generation of hybrid CagA proteins, a phosphorylation of the most N-terminal TPM-A could be excluded. Our data suggest that tyrosine phosphorylation at TPM-C is sufficient, but not exclusive,to activate translocated CagA. Activated CagAPtr might either convert into a phosphatase itself or activate a cellular phosphatase to dephosphorylate cellular phosphoproteins and modulate cellular signalling cascades of the host.

Amino Acid Motifs↗
PubMed2002

Bendamustine in the treatment of chronic lymphocytic leukemia: results and future perspectives.

Chronic lymphocytic leukemia (CLL) occurs predominantly in elderly patients. The treatment options for patients with CLL have increased with the introduction of purine analogs, and promising results have been reported with fludarabine and cladribine when these agents are used in newly diagnosed and relapsed disease. Monoclonal antibodies such as alemtuzumab and rituximab are also clinically active in CLL. The use of purine analogs in combination with monoclonal antibodies may provide additional treatment options and this strategy is being studied in patients with relapsed and refractory CLL. Bendamustine is an alkylating agent with properties of a purine analog and is a promising agent in the treatment of CLL. Bendamustine reduces the number of circulating B lymphocytes by over 90% and shows only partial cross-resistance with other alkylating agents, making it an ideal candidate for the treatment of CLL and for use in combination with other alkylating agents. Bendamustine monotherapy can be given to patients whose disease is refractory to standard therapies. The results of a trial using bendamustine as a salvage treatment in patients with relapsed or refractory, heavily pretreated CLL are discussed here. Bendamustine 100 mg/m(2) (days 1 and 2) was found to be an effective treatment for older patients with advanced CLL, with 14 of 21 patients responding. Complete hematologic remission was achieved in six of 21 patients and a further eight patients achieved a partial hematologic remission. The main toxicities were hematologic; nonhematologic side effects were mild and uncommon.

Aged↗
PubMed2002

Role of the alpAB proteins and lipopolysaccharide in adhesion of Helicobacter pylori to human gastric tissue.

The attachment of the bacterial pathogen Helicobacter pylori (H. pylori) to gastric epithelial cells is commonly believed to be required for an efficient and persistent colonization of the human stomach as well as for host cell trans-membrane signaling. In the past, several putative adhesins were postulated, including the outer membrane proteins AlpAB and the bacterial lipopolysaccharide (LPS) presenting oligomeric Lewis x (Le(x)) sugar components. We investigated the AlpAB-mediated and the Le(x)-dependent binding by knockout mutagenesis in one distinct strain, H. pylori P1. We show here that the mutagenesis of either alpA and/or alpB dramatically reduced the adherence of H. pylori P1 to a given gastric biopsy section. None of these mutations influenced the surface exposure of the Le(x) antigen, suggesting that the assembly and/or presentation of LPS is independent of the AlpAB outer membrane proteins. However, a truncation of the LPS O-side chain by a galE mutation abolished the presentation of the Le(x) epitope. This Le(x)-negative strain did not show any significant reduction in its binding capacity to the gastric tissue, when compared with the corresponding wild-type strain. From these data we conclude that the AlpAB-specific adherence is independent of the composition of the LPS and that the oligomeric Le(x) structure does not confer binding to the gastric biopsy material used in this study. As the adhesion properties of our H. pylori strain P1 vary in dependence on the respective biopsy donor it is assumed that the surface-exposed Le(x) epitope recognizes a different host cell receptor than AlpAB, which was probably not present in the tissue sections used in this study.

Adhesins, Bacterial↗
PubMed2002

CagA tyrosine phosphorylation and interleukin-8 induction by Helicobacter pylori are independent from alpAB, HopZ and bab group outer membrane proteins.

In several studies Helicobacter pylori type I strains (cag-positive strains) have been described to translocate their CagA protein into epithelial cells, where it is tyrosine-phosphorylated. The intimate contact allows a Cag-dependent bacteria-to-cell signaling inducing the secretion of the chemokine interleukin-8. Although a contact between the bacterial and the eukaryotic cell is known to be necessary for these signal transduction events the bacterial adhesin and the cellular receptor are unknown, so far. In this study, we investigated the influence of several outer membrane proteins associated with adherence on CagA translocation and IL-8 induction. The quantitative assessment of a cag deletion mutant strain binding to epithelial cells revealed that the Cag secretion apparatus is not primarily necessary for attachment. In contrast, the knockout mutation of the adherence-associated alpAB locus significantly reduced the binding capacity in two independent strains. Despite this partial adherence defect, the alpAB mutation did not affect CagA translocation and IL-8 induction. The mutagenesis of the bab group genes hp317, hp896 and hp1243 in H. pylori 26695 did not influence the Cag-dependent signaling either. No causative linkage could be found between the production of the outer membrane proteins HopZ, OipA or seven additional outer membrane proteins and CagA translocation or IL-8 induction.

Adhesins, Bacterial↗
PubMed2002

Essential role of ferritin Pfr in Helicobacter pylori iron metabolism and gastric colonization.

The reactivity of the essential element iron necessitates a concerted expression of ferritins, which mediate iron storage in a nonreactive state. Here we have further established the role of the Helicobacter pylori ferritin Pfr in iron metabolism and gastric colonization. Iron stored in Pfr enabled H. pylori to multiply under severe iron starvation and protected the bacteria from acid-amplified iron toxicity, as inactivation of the pfr gene restricted growth of H. pylori under these conditions. The lowered total iron content in the pfr mutant, which is probably caused by decreased iron uptake rates, was also reflected by an increased resistance to superoxide stress. Iron induction of Pfr synthesis was clearly diminished in an H. pylori feoB mutant, which lacked high-affinity ferrous iron transport, confirming that Pfr expression is mediated by changes in the cytoplasmic iron pool and not by extracellular iron. This is well in agreement with the recent discovery that iron induces Pfr synthesis by abolishing Fur-mediated repression of pfr transcription, which was further confirmed here by the observation that iron inhibited the in vitro binding of recombinant H. pylori Fur to the pfr promoter region. The functions of H. pylori Pfr in iron metabolism are essential for survival in the gastric mucosa, as the pfr mutant was unable to colonize in a Mongolian gerbil-based animal model. In summary, the pfr phenotypes observed give new insights into prokaryotic ferritin functions and indicate that iron storage and homeostasis are of extraordinary importance for H. pylori to survive in its hostile natural environment.

Animals↗
PubMed2002

Characterization of two cryptic Helicobacter pylori plasmids: a putative source for horizontal gene transfer and gene shuffling.

Many Helicobacter pylori isolates carry cryptic plasmids of extremely variable size. In this study we analyzed two H. pylori plasmids, pHel4 and pHel5, from H. pylori strains P8 and P29, respectively. Plasmid pHel4 consists of 10,970 bp, constituting 15 putative open reading frames (ORFs), whereas pHel5 consists of 18,291 bp, constituting 17 ORFs. The findings that both plasmids encode a conserved RepA protein and that both have an origin of replication containing an iteron place them in the group of theta plasmids. In pHel4, the products of the overlapping orf4C, orf4D, orf4E, and orf4F sequences are homologous to MobA, MobB, MobC, and MobD, encoded by colicinogenic plasmids, suggesting that pHel4 might be mobilizable. A further putative operon consists of orf4B and orf4A, the products of which are homologous to microcin C7 (MccC7) biosynthesis and secretion proteins MccB and MccC, respectively. Plasmid pHel5 carries putative genes encoding proteins with homology to an endonuclease and gene products of an H. pylori chromosomal plasticity zone. Both plasmids contain repeat sequences, such as the previously identified R2 repeat, which are considered preferred recombination sites. In pHel4, a new repeat sequence (R4 repeat), which seems to act as a hot spot for site-specific recombination, was identified. All H. pylori plasmids characterized so far have a modular structure. We suggest a model that explains the existing plasmids by insertions and deletions of genetic elements at the repeat sequences. A genetic exchange between plasmids and the bacterial chromosome, combined with plasmid mobilization, might add a novel mechanism to explain the high genetic macrodiversity within the H. pylori population.

Amino Acid Sequence↗
PubMed2002

Discrimination between cases of duodenal ulcer and gastritis on the basis of putative virulence factors of Helicobacter pylori.

The BabA, cagA, and vacA statuses of 827 Helicobacter pylori isolates were used in logistic regression models to discriminate duodenal ulcer from gastritis. Only BabA was a candidate for a universal virulence factor, but the low c statistic value (0.581) indicates that none of these factors were helpful in predicting the clinical presentation.

Adhesins, Bacterial↗
PubMed2002

Stem cell dose and tumorbiologic parameters as prognostic markers for patients with metastatic breast cancer undergoing high-dose chemotherapy with autologous blood stem cell support.

We report on the prognostic significance of tumorbiologic parameters and CD34(+) cell dose in 120 patients with metastatic breast cancer (MBC) who received high-dose chemotherapy (HDCT) with autologous blood stem cell transplantation as first-line treatment. Her2/neu, p53, Ki67, and bcl-2 protein expression were studied using immunohistochemical staining on formalin-fixed, paraffin-embedded primary tumor sections. DNA content of tumor cells (DNA-index) and tumor cell proliferation (S-phase fraction) were measured by DNA flow cytometry. The relationship between these parameters and the CD34(+) cell dose and progression free (PFS) and overall survival (OS) was analyzed. With a median follow-up period of 40 months (range, 7-89 months), no more than two metastatic sites (relative risk [RR] = 3.84 [95% confidence interval (CI) 1.49-10]; p =.005) and hyperploidy (RR = 2.58 [95% CI 1.26-5.26]; p =.009) were independent predictors of longer PFS according to multivariate analysis. Independent prognostic factors of longer OS included one or two metastatic sites (RR = 4.16 [95% CI 1.96-4.16]; p <.001), a positive combined hormone receptor status (RR = 2.45 [95% CI 1.45-4.14]; p =.001) and a high number of infused stem cells (>7.8 x 10(6) CD34(+) cells per kg body weight) (RR = 2.0 [95% CI 1.17-3.42]; p =.01). In conclusion, positive hormone receptors, < or =2 metastatic sites, high DNA-index and high CD34(+) cell dose (>7.8 x 10(6) CD34(+) cells per kg) are predictors for a favorable outcome after autotransplantation for MBC. Our observation might indicate a favorable effect of HDCT in MBC patients with overexpression of Her2/neu who might have a worse prognosis when treated with conventional chemotherapy.

Adult↗
PubMed2002

Rituximab reduces the number of peripheral blood B-cells in vitro mainly by effector cell-mediated mechanisms.

BACKGROUND AND OBJECTIVES: The humanized CD20 mono- clonal antibody, rituximab, has significant anti-tumor activity in patients with B-cell non-Hodgkin's lymphoma and induces depletion of B-cells in vivo. It was the objective of this study to define the contribution of the different mechanisms of action of rituximab on primary normal and malignant B-cells. DESIGN AND METHODS: Primary human B-lymphocytes and effector cell fractions were isolated from peripheral blood of normal donors using an immunomagnetic separation technique. Blood samples from 20 patients with chronic lymphocytic leukemia (CLL) were studied and the B-lymphoblastoid Daudi cell line was used as a control. B-cells were cultured in the presence or absence of rituximab adding a secondary hyper-crosslinking antibody, serum as source of complement or different effector cell fractions. The cells were analyzed by immunofluorescence staining and flow cytometry. RESULTS: In contrast to the B-lymphoblastoid Daudi cell line, the number of highly purified normal peripheral blood CD19+ cells was only minimally affected by rituximab in the presence of autologous serum. A significant reduction in the number of B-cells was observed when mononuclear cells from peripheral blood were added back. To identify the cell type which mediates this effect, CD3+ T-cells, CD56+ cells, and CD14+ monocytes were added to selected CD22+ B-cells. A marked B-cell decrease was only observed in the presence of CD56+ and CD14+ cells in an effector to target ratio of 10:1. The experiments with mononuclear cells from patients with CLL showed a B-cell reduction by rituximab, which was significantly enhanced following addition of granulocyte-macrophage colony-stimulating factor (GM-CSF). INTERPRETATION AND CONCLUSIONS: These data support the important role of cell-mediated mechanisms in the B-cell-depleting action of rituximab and suggest that pre-treatment with GM-CSF could improve the response to rituximab in patients with CLL.

Antibodies, Monoclonal↗