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  • Articles  (52)
  • American Society of Hematology  (38)
  • American Geophysical Union  (9)
  • Blackwell Science Ltd  (5)
  • 2005-2009  (33)
  • 2000-2004  (19)
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  • Articles  (52)
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  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Enteropathogenic Escherichia coli (EPEC), like many bacterial pathogens, use a type III secretion system to deliver effector proteins across the bacterial cell wall. In EPEC, four proteins, EspA, EspB, EspD and Tir are known to be exported by a type III secretion system and to be essential for ‘attaching and effacing’ (A/E) lesion formation, the hallmark of EPEC pathogenicity. EspA was recently shown to be a structural protein and a major component of a large, transiently expressed, filamentous surface organelle which forms a direct link between the bacterium and the host cell. In contrast, EspB is translocated into the host cell where it is localized to both membrane and cytosolic cell fractions. EspA and EspB are required for translocation of Tir to the host cell membrane suggesting that they may both be components of the translocation apparatus. In this study, we show that EspB co-immunoprecipitates with the EspA filaments and that, during EPEC infection of HEp-2 cells, EspB localizes closely with EspA. Using a number of binding assays, we also show that EspB can bind and be copurified with EspA. Nevertheless, binding of EspA filaments to the host cell membranes occurred even in the absence of EspB. These results suggest that following initial attachment of the EspA filaments to the target cells, EspB is delivered into the host cell membrane and that the interaction between EspA and EspB may be important for protein translocation.
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  • 2
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The type III secretion system (TTSS) is a macromolecular structure that spans the cell wall of Gram-negative bacterial pathogens, enabling delivery of virulence effector proteins directly to the membranes and cytosol of host eukaryotic cells. TTSS consists of a conserved needle complex (NC) that is composed of sets of inner and outer membranes rings connected by a periplasmic rod. Enteropathogenic Escherichia coli (EPEC) is an extracellular diarrhoeagenic pathogen that uses TTSS to induce actin polymerization and colonizes the intestinal epithelium. In EPEC, EscJ is predicted to be targeted to the periplasm, in a sec-dependent manner, and to bridge the TTSS membrane-associated rings. In this study we determined the global fold of EscJ using Nuclear Magnetic Resonance spectroscopy. We show that EscJ comprises two subdomains (D1 – amino acid residues 1–55 in the mature protein, and D2 – amino acid residues 90–170), each comprising a three-stranded β-sheet flanked by two α-helices. A flexible region (residues 60–85) couples the structured regions D1 and D2. Periplasmic overexpression of EscJD1 and EscJD2 in a single escJ mutant bacterium failed to restore protein secretion activity, suggesting that the flexible linker is essential for the rod function. In contrast, periplasmic overexpression of EscJD1 and EscJD2 in the same wild-type bacterium had a dominant-negative phenotype suggesting defective assembly of the TTSS and protein translocation.
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  • 3
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Enteropathogenic Escherichia coli (EPEC), an important cause of infantile diarrhoea in the developing world, disrupts host cell microvilli, causes actin rearrangements and attaches intimately to the host cell surface. This characteristic phenotype, referred to as the attaching and effacing (A/E) effect, is encoded on a 36 kb pathogenicity island called the locus of enterocyte effacement (LEE). The LEE includes genes involved in type III secretion and translocation, the eae gene encoding an outer membrane adhesin known as intimin, the tir gene for the translocated intimin receptor, a regulator and various genes of unknown function. Among this last group is sepL. To determine the role of SepL in EPEC pathogenesis, we constructed and tested a non-polar sepL mutant. We found that this sepL mutant is deficient for A/E and that it secretes markedly reduced quantities of those proteins involved in translocation (EspA, EspB and EspD), but normal levels of those proteins presumed to be effectors (Tir, EspF and EspG). Despite normal levels of secretion, the mutant strain was unable to translocate EspF and Tir into host cells and formed no EspA filaments. Fractionation studies revealed that SepL is a soluble cytoplasmic protein. Yeast two-hybrid and affinity purification studies indicated that SepL interacts with the LEE-encoded protein SepD. In contrast to SepL, we found that SepD is required for type III secretion of both translocation and effector proteins. Together, these results demonstrate that SepL has a unique role in type III secretion as a functional component of the translocation system that interacts with an essential element of the secretion machinery.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 49 (2003), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The type III secretion system (TTSS) is a modular apparatus assembled by many pathogenic Gram-negative bacteria and is designed to translocate proteins through the bacterial cell wall into the eukaryotic host cell. The conserved components of the TTSS comprise stacks of rings spanning the inner and outer bacterial membrane and a narrow, needle-like structure projecting outwards. The TTSS of enteropathogenic E. coli is unique in that one of the translocator proteins, EspA, polymerizes to form an extension to the needle complex which interacts with the host cell. In this study we present the 3D structure of EspA filaments to c. 26 Å resolution determined from electron micrographs of negatively stained preparations by image processing. The structure comprises a helical tube with a diameter of 120 Å enclosing a central channel of 25 Å diameter through which effector proteins may be transported. The subunit arrangement corresponds to a one-start helix with 28 subunits present in five turns of the helix and an axial rise of 4.6 Å per subunit. This is the first report of a 3D structure of a filamentous extension to the TTSS.
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  • 5
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Map is an enteropathogenic Escherichia coli (EPEC) protein that is translocated into eukaryotic cells by a type III secretion system. Although not required for the induction of attaching and effacing (A/E) lesion formation characteristic of EPEC infection, translocated Map is suggested to disrupt mitochondrial membrane potential, which may impact upon subsequent functions of the organelle such as control of cell death. Before secretion, many effector proteins are maintained in the bacterial cytosol by association with a specific chaperone. In EPEC, chaperones have been identified for the effector proteins translocated intimin receptor (Tir) and EspF, and for the translocator proteins EspB and EspD. In this study, we present evidence that the Tir-specific chaperone, CesT, also performs a chaperone function for Map. Using a combination of biochemical approaches, we demonstrate specific interaction between CesT and Map. Similar to other chaperone–effector pairings, binding is apparent at the amino-terminus of Map and is indicated to proceed by a similar mechanism to CesT:Tir interaction. Map secretion from a cesT mutant strain (SE884) is shown to be reduced and, importantly, its translocation from this strain after infection of HEp-2 cells is almost totally abrogated. Although other chaperones are reported to have a bivalent binding specificity, CesT is the first member of its family that chaperones more than one protein for translocation.
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  • 6
    Publication Date: 2009-11-20
    Description: Abstract 3403 Poster Board III-291 Autologous PSCT remains standard treatment in younger patients (pts) with multiple myeloma. However, relapse is the major cause of treatment failure. Several studies have reported improved progression-free survival (PFS) and possibly overall survival with thalidomide alone or in combination with steroid and chemotherapy as maintenance/consolidation therapy post autologous PSCT. We performed a phase II study investigating the role of sequential velcade/thalidomide/dexamethasone (VTD) as maintenance therapy post single PSCT. The objectives were to examine the toxicities of prolonged course of sequential VTD, CR rate, PFS and overall survival following single autologous PSCT. Within 4-8 weeks of autologous PSCT using melphalan 200mg/m2, pts received weekly velcade (vel) at 1.3mg/m2 /wk x 3 weeks with 1 week rest and dexamethasone (dex) at 40mg/d x 4 d for 6 months, followed by thalidomide (thal) at 50 -200mg/d and dexamethasone (dex) at 40mg/dx4 d for 6 more months. Single agent thalidomide was then continued until disease progression. Twenty-eight pts have been enrolled. Median age is 54 years (29-66). Median time from diagnosis is 7.9 mo. (4.2 – 145). Disease stage at diagnosis; by Salmon-Durie (II/III 6/22) and by ISS (I/II/III 11/9/7/missing data in 1 pt). Pts received induction treatment with thal/dex (14), velcade based (15) and revlimid based regimens (7). Median B2M at enrollment is 1.75 mg/L (1.14 -5.3). Disease status at enrollment; CR (7) VGPR (9), PR (11), SD (1). Three pts have chromosome 13 abnormalities (1 pt by karyotype and 2 pts by FISH). Results: All pts have undergone transplant. Four pts were unable to start planned maintenance therapy due to development of grade II or more neuro toxicities (3), and persistent thrombocytopenia (1) after PSCT. Twenty-four pts started maintenance vel/dex within 4-8 weeks of PSCT. Nine pts have completed 6 months of vel/dex. Two pts stopped vel/dex because of low WBC (1) or PN (1). With a median F/U of 5.2 mo. (1.2 -17.3) nine of 28 pts (33%) have achieved CR post PSCT and six out of 11 evaluable pts (55%) have achieved CR after vel/dex. Six out of 9 pts (66%) who have completed 6 mo. of vel/dex achieved CR. Two out of 9 pts (22%) have upgraded their response with vel/dex. Four pts have completed 6 month of thal/dex and are beyond 1 year post PSCT. Two out of 4 pts remain in CR at one year post PSCT. One pt is in PR and 1 pt has progressed. Two pts could not complete thal/dex phase of therapy because of relapse (1) and grade III GI toxicity (1). Three pts have relapsed of whom 1 pt died of relapsed myeloma (leptomeningeal disease). No grade IV toxicity has been noted. Grade III toxicities have occurred in 4 pts; low platelet (1), fatigue (1), mood alteration (1), GI (severe constipation) (1). Thirteen pts have peripheral neuropathy (PN). Ten pts had PN grade I at enrollment. Only 3 pts have developed PN on the study and all are grade I - II. Median velcade dose is 1.3 mg /m2/wk and thalidomide dose is 100mg /d. Conclusion: Prolonged sequential velcade/thalidomide/dexamethasone maintenance therapy post single autologous PSCT is well tolerated with no severe peripheral neuropathy. Fifty-five percent of pts have achieved CR and 22% have upgraded their response after six months of velcade/dexamethasone therapy suggesting this is an active and well tolerated maintenance strategy post PSCT. Disclosures: Sahebi: Celgene: Honoraria; Millennium Pharmaceutical: Research Funding. Off Label Use: The use of bortezomib(Velcade)in combination with thalidomide and dexamethasone is investigated as maintenance therapy post autologuous stem cell transplant in patients with multiple myeloma.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
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  • 7
    Publication Date: 2005-11-16
    Description: E1496 is a phase III trial designed to evaluate the ability of 2 years (yr) of maintenance rituximab (MR) to prolong progression-free survival (PFS) after CVP (cyclophosphamide 1 G/m2 day [d] 1, vincristine 1.4 mg/m2 [max = 2 mg] d 1, prednisone 100 mg/m2 d 1–5) chemotherapy in stage III–IV follicular grade 1 and 2 and small lymphocytic lymphoma. After CVP treatment to maximum response, (6–8 cycles), stable and responding patients (pt) were randomized to MR (375 mg/m2 weekly x 4) every 6 months x 4 or observation (OBS). Stratification factors included histology, response and residual disease after CVP. With 3-yr median follow-up, survivals (from time of randomization, one-sided logrank p values) for all pt (n=304) favored MR for PFS (p = 3 x 10–8; hazard rate {HR} = 0.38 [0.28;0.54, 95% confidence intervals]) and OS (p = 0.09; HR = 0.66 [0.36–1.22]). Because the large majority of pt have FL and because rituximab efficacy is notably greater in FL, we focused in this report on the 237 FL pt. Median age was 58 yr, 65% were stage IV, 64% had marrow disease, 64% had high tumor burden and 37% had high-risk disease by the follicular lymphoma prognostic index. PFS after randomization was significantly longer for MR vs OBS (p = 3 x 10-7; HR = 0.39 [0.27;0.57]). The estimated PFS at 4 yr (~4.5 yr after start of treatment) was 56% for MR vs 33% for OBS. Differences in PFS were significant within the predefined strata and the differences were most significant in favor of MR for pt with high initial tumor burden and minimal residual disease after CVP. Overall survival was superior for MR (p = 0.03; HR = 0.51 [0.25;1.04]. Estimated OS at 4 yr (~4.5 years after start of treatment) was 88% for MR vs 72% for OBS. Of 33 deaths, 21 occurred on the OBS arm. These data demonstrate that maintenance rituximab not only significantly delays disease progression in FL compared with OBS but that a substantial proportion of patients treated with MR remain disease-free at 4 years after the completion of CVP. These are the first data to strongly suggest a survival benefit with a therapy that includes rituximab and CVP and the first to strongly suggest a survival benefit with maintenance rituximab in FL.
    Print ISSN: 0006-4971
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  • 8
    Publication Date: 2008-11-16
    Description: Fludarabine and rituximab are commonly used in combination in the treatment of Waldenstrom’s macroglobulinemia (WM), though long term outcome of this regimen remains to be defined. We therefore examined the outcome of 43 WM patients treated on a clinical trial whose eligibility included 〈 2 prior therapies, and no previous nucleoside analogue or rituximab treatment. Therapy consisted of 6 cycles (25 mg/m2/day for 5 days) of fludarabine and 8 infusions (375 mg/m2/week) of rituximab over 31 weeks. 43 patients were enrolled with a median age of 61, and median prior therapies of 0. Responses were: CR (n=2); VGPR (n=14); PR (n=21); MR (n=4); for an overall and major response rate of 95.3% and 86.0%, respectively. At best response, median bone marrow disease involvement declined from 55% to 5% (p
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  • 9
    Publication Date: 2003-01-15
    Description: Overexpression of Bcl-2 is a potential mechanism for chemoresistance in acute leukemia and has been associated with unfavorable clinical outcome. We hypothesized that down-regulation of Bcl-2 would restore chemosensitivity in leukemic cells. To test this hypothesis, we performed a phase 1 study of G3139 (Genasense, Genta, Berkeley Heights, NJ), an 18-mer phosphorothioate Bcl-2 antisense, with fludarabine (FL), cytarabine (ARA-C), and granulocyte colony-stimulating factor (G-CSF) (FLAG) salvage chemotherapy in patients with refractory or relapsed acute leukemia. Twenty patients with refractory or relapsed acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL) were enrolled. G3139 was delivered by continuous infusion on days 1 to 10. FLAG chemotherapy was administered on days 5 to 10. Common side effects of this combination included fever, nausea, emesis, electrolyte imbalance, and fluid retention that were not dose limiting. Plasma pharmacokinetics of G3139 demonstrated steady-state concentration (Css) within 24 hours. Of the 20 patients, 9 (45%) had disease response, 6 (5 AML, 1 ALL) with complete remission (CR) and 3 (2 AML and 1 ALL) with no evidence of disease but failure to recover normal neutrophil and/or platelet counts or to remain in remission for at least 30 days (incomplete remission). Bcl-2 mRNA levels were down-regulated in 9 of the 12 (75%) evaluable patients. This study demonstrates that G3139 can be administered safely with FLAG chemotherapy and down-regulate its target, Bcl-2. The encouraging clinical and laboratory results justify the current plans for a phase 3 study in previously untreated high-risk AML (ie, age at least 60 years).
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  • 10
    Publication Date: 2004-11-16
    Description: Background: Although complete remission rates for AML are near 70% with combination induction and consolidation chemotherapy, most patients will relapse and die from the disease or treatment complications. New agents with unique mechanisms are needed. One such class of therapeutics are fusion proteins consisting of protein synthesis inactivating peptide toxins fused to tumor cell selective ligands. DT388-IL3 is one such fusion protein. Rationale: In preclinical studies, DT388-IL3 was cytotoxic to the IL3 receptor expressing leukemia cell lines but not toxic to IL3 receptor negative cell lines. This agent was less toxic to normal progenitors and not toxic to early hematopoietic stem cells. The majority of AML progenitors overexpress IL3 receptors. Animal model work in mice bearing human leukemia cells has demonstrated anti-leukemia efficacy which is dose dependent with this agent. Toxicities in monkeys include vascular leak syndrome and pancytopenia observed only at the highest doses. The MTD in monkeys was estimated at 60mcg/kg/day. We report preliminary data on the use of DT388-IL3 fusion protein in humans from an ongoing phase I trial. Pharmacokinetics; clinical and immune response to this novel fusion protein are also being followed. Patients and Methods: Patients with refractory AML were eligible. The first dose level was qd M-W-F X six doses of DT388-IL3 at 4mcg/kg/day with dose escalation planned for subsequent patients. Patients with progression of disease or unacceptable study drug toxicity were to be removed from the study. Toxicity was graded according to NCI CTCAE version 3.0. Three patients have been treated with DT388-IL3. Serum samples were collected and will be assayed for anti-DT388-IL3 antibodies prior to and after treatment. Blood samples were obtained to measure circulating levels of active DT388-IL3 and its half life. Patient blasts were also collected prior to treatment for later analysis of expression of IL3 receptors. Result: Two patients tolerated the treatment schedule(of six doses) without any significant toxicities. Mild fever, headaches, nausea were noted. Both of these patients had progression of disease-one during treatment and one on day 15 bone marrow biospy. The above mentioned patients died secondary to disease complications at 2 weeks and 18 weeks after their last dose of the study agent respectively. DT388-IL3 levels on these two patients post infusion were below the the reliable detectable limits of the assay. The third patient became febrile and hypotensive after the first dose. The hypotension persisted and she did not receive any further doses. This patient is alive 5 weeks later with supportive care alone. DT388-IL3 levels following this patient’s dose are as follows: 2min post infusion 34.3ng/ml, 30min post infusion 1.9ng/ml, 60min post infusion 0.075ng/ml, 120min post infusion 0.003ng/ml, 240min post infusion undetectable. Conclusion: Preclinical/animal studies suggest that DT388-IL3 has anti-leukemia efficacy. Preliminary data from our ongoing phase I trial reveals minimal study agent related toxicity and no life threatening complications at this first dose level. Dose escalation is planned as per protocol.
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