Search tips
Search criteria

Results 1-16 (16)

Clipboard (0)

Select a Filter Below

Year of Publication
1.  Role of Vpma phase variation in Mycoplasma agalactiae pathogenesis 
Compared with other bacterial pathogens, the molecular mechanisms of mycoplasma pathogenicity are largely unknown. Several studies in the past have shown that pathogenic mycoplasmas are equipped with sophisticated genetic systems that allow them to undergo high-frequency surface antigenic variations. Although never clearly proven, these variable mycoplasma surface components are often implicated in host immune evasion and adaptation. Vpma surface lipoproteins of the ruminant pathogen Mycoplasma agalactiae are encoded on a genomic pathogenicity island–like locus and are considered as one of the well-characterized model systems of mycoplasma surface antigenic variation. The present study assesses the role of these phase-variable Vpmas in the molecular pathogenesis of M. agalactiae by testing the wild-type strain PG2 in comparison with the xer1-disrupted Vpma ‘phase-locked’ mutants in sheep infection models. The data clearly illustrate that although Xer1 recombinase is not a virulence factor of M. agalactiae and Vpma phase variation is not necessary for establishing an infection, it might critically influence the survival and persistence of the pathogen under natural field conditions, mainly due to a better capacity for dissemination and evoking systemic responses. This is the first study where mycoplasma ‘phase-locked’ mutants are tested in vivo to elucidate the role of phase variation during infection.
PMCID: PMC4510919  PMID: 22809092
Mycoplasma agalactiae; phase variation; variable surface lipoproteins; Vpma; phase-locked mutants; mastitis
2.  First steps towards the genetic manipulation of Mycoplasma agalactiae and Mycoplasma bovis using the transposon Tn4001mod 
Mycoplasma agalactiae and M. bovis rank amongst the most serious pathogenic mycoplasmas infecting small ruminants and cattle, respectively. Despite considerable advances made in Mycoplasma molecular genetics in the past decade, there is still a complete lack of genetic tools to assess the pathogenic mechanisms of these two species. Studies were undertaken to develop a genetic system for the analysis of potential virulence factors of these pathogens. Transposon Tn4001mod was successfully introduced into various chromosomal sites of M. agalactiae and M. bovis with an optimal frequency of 10−6 per viable colony-forming unit (CFU). This is the first report that demonstrates the amenability of these agents to transformation and to genetic manipulation. Furthermore, Tn4001 is implicated as the first potential genetic tool available for these ruminant pathogens.
PMCID: PMC4509485  PMID: 15715173
Mycoplasma; Transformation; Transposon; Genetics; Mutagenesis
3.  Generation of Highly Purified Human Cardiomyocytes from Peripheral Blood Mononuclear Cell-Derived Induced Pluripotent Stem Cells 
PLoS ONE  2015;10(5):e0126596.
Induced pluripotent stem (iPS) cells have an enormous potential for physiological studies. A novel protocol was developed combining the derivation of iPS from peripheral blood with an optimized directed differentiation to cardiomyocytes and a subsequent metabolic selection. The human iPS cells were retrovirally dedifferentiated from activated T cells. The subsequent optimized directed differentiation protocol yielded 30-45% cardiomyocytes at day 16 of differentiation. The derived cardiomyocytes expressed appropriate structural markers like cardiac troponin T, α-actinin and myosin light chain 2 (MLC2V). In a subsequent metabolic selection with lactate, the cardiomyocytes content could be increased to more than 90%. Loss of cardiomyocytes during metabolic selection were less than 50%, whereas alternative surface antibody-based selection procedures resulted in loss of up to 80% of cardiomyocytes. Electrophysiological characterization confirmed the typical cardiac features and the presence of ventricular, atrial and nodal-like action potentials within the derived cardiomyocyte population. Our combined and optimized protocol is highly robust and applicable for scalable cardiac differentiation. It provides a simple and cost-efficient method without expensive equipment for generating large numbers of highly purified, functional cardiomyocytes. It will further enhance the applicability of iPS cell-derived cardiomyocytes for disease modeling, drug discovery, and regenerative medicine.
PMCID: PMC4430251  PMID: 25970162
4.  A Novel Armed Oncolytic Measles Vaccine Virus for the Treatment of Cholangiocarcinoma 
Human Gene Therapy  2013;24(5):554-564.
Cholangiocarcinoma (CC) is curable only in early stages by complete surgical resection. Thus, in advanced disease stages in which a complete removal of the tumor mass is no longer possible and palliative chemotherapy achieves only modest success, therapeutics employing new methods of action are desperately needed. Oncolytic viruses employed in clinical studies have been shown to spread preferentially in cancer cells. Beyond that, virotherapeutic cell killing can be enhanced by virus-based expression of suicide genes. We engineered a measles vaccine virus (MeV) vector expressing super cytosine deaminase (SCD), a fusion protein of yeast cytosine deaminase and uracil phosphoribosyltransferase, which converts the prodrug 5-fluorocytosine (5-FC) to 5-fluorouracil (5-FU) and subsequently to 5-fluorouridine-monophosphate. This novel vector was evaluated using three different human-derived CC cell lines. In vitro, all CC cell lines were found to be permissive to MeV infection. Partial blocking of MeV-mediated oncolysis could be overcome by employment of the SCD transgene together with administration of 5-FC. In vivo, intratumoral application of SCD-armed MeV together with a systemic 5-FC treatment showed a significant reduction in tumor size in a TFK-1 xenograft mouse model when compared with virus-only treatment. In a second animal experiment employing a HuCCT1 xenograft tumor model, an enhanced SCD-armed MeV vector, in which the SCD transgene was expressed from a different genomic position, led not only to reduced tumor volumes, but also to a significant survival benefit. On the basis of these encouraging preclinical data on employment of SCD-armed MeV for the virotherapeutic treatment of chemotherapy-resistant CC, a clinical virotherapy trial is set up currently.
Lange and colleagues engineer a measles vaccine virus (MeV) vector expressing an enzyme that converts 5-fluorocytosine (5-FC) prodrug into 5-fluorouracil-monophosphate. Partial blocking of MeV-mediated oncolysis could be overcome by vector and 5–FC co-administration in cell lines. In vivo, intratumoral vector injection along with systemic 5–FC treatment resulted in significant tumor reduction in a xenograft mouse model.
PMCID: PMC3655633  PMID: 23550539
5.  Attenuated and Protease-Profile Modified Sendai Virus Vectors as a New Tool for Virotherapy of Solid Tumors 
PLoS ONE  2014;9(3):e90508.
Multiple types of oncolytic viruses are currently under investigation in clinical trials. To optimize therapeutic outcomes it is believed that the plethora of different tumor types will require a diversity of different virus types. Sendai virus (SeV), a murine parainfluenza virus, displays a broad host range, enters cells within minutes and already has been applied safely as a gene transfer vector in gene therapy patients. However, SeV spreading naturally is abrogated in human cells due to a lack of virus activating proteases. To enable oncolytic applications of SeV we here engineered a set of novel recombinant vectors by a two-step approach: (i) introduction of an ubiquitously recognized cleavage-motive into SeV fusion protein now enabling continuous spreading in human tissues, and (ii) profound attenuation of these rSeV by the knockout of viral immune modulating accessory proteins. When employing human hepatoma cell lines, newly generated SeV variants now reached high titers and induced a profound tumor cell lysis. In contrast, virus release from untransformed human fibroblasts or primary human hepatocytes was found to be reduced by about three log steps in a time course experiment which enables the cumulation of kinetic differences of the distinct phases of viral replication such as primary target cell infection, target cell replication, and progeny virus particle release. In a hepatoma xenograft animal model we found a tumor-specific spreading of our novel recombinant SeV vectors without evidence of biodistribution into non-malignant tissues. In conclusion, we successfully developed novel tumor-selective oncolytic rSeV vectors, constituting a new tool for virotherapy of solid tumors being ready for further preclinical and clinical development to address distinct tumor types.
PMCID: PMC3944018  PMID: 24598703
6.  Optical Detection and Virotherapy of Live Metastatic Tumor Cells in Body Fluids with Vaccinia Strains 
PLoS ONE  2013;8(9):e71105.
Metastatic tumor cells in body fluids are important targets for treatment, and critical surrogate markers for evaluating cancer prognosis and therapeutic response. Here we report, for the first time, that live metastatic tumor cells in blood samples from mice bearing human tumor xenografts and in blood and cerebrospinal fluid samples from patients with cancer were successfully detected using a tumor cell-specific recombinant vaccinia virus (VACV). In contrast to the FDA-approved CellSearch system, VACV detects circulating tumor cells (CTCs) in a cancer biomarker-independent manner, thus, free of any bias related to the use of antibodies, and can be potentially a universal system for detection of live CTCs of any tumor type, not limited to CTCs of epithelial origin. Furthermore, we demonstrate for the first time that VACV was effective in preventing and reducing circulating tumor cells in mice bearing human tumor xenografts. Importantly, a single intra-peritoneal delivery of VACV resulted in a dramatic decline in the number of tumor cells in the ascitic fluid from a patient with gastric cancer. Taken together, these results suggest VACV to be a useful tool for quantitative detection of live tumor cells in liquid biopsies as well as a potentially effective treatment for reducing or eliminating live tumor cells in body fluids of patients with metastatic disease.
PMCID: PMC3760980  PMID: 24019862
7.  Integrating Medical Humanities into a Pharmaceutical Care Seminar on Dementia 
Objective. To design, integrate, and assess the effectiveness of a medical humanities teaching module that focuses on pharmaceutical care for dementia patients.
Design. Visual and textual dementia narratives were presented using a combination of teacher and learner-centered approaches with the aim being to highlight patients’ and caregivers’ needs for empathy and counselling.
Assessment. As gauged from pre- and post-experience questionnaires, students highly rated this approach to teaching medical humanities. In-class presentations demonstrated students’ increased sensitivity to patient and caregiver needs, while objective learning outcomes demonstrated students’ increased knowledge and awareness.
Conclusions. Pharmacy students were open to and successfully learned from reading and discussing patient and caregiver narratives, which furthers the discussion on the value of integrating the medical humanities into the curricula of pharmacy and other health sciences.
PMCID: PMC3578329  PMID: 23459365
medical humanities; pharmaceutical care; Alzheimer’s disease; learning outcomes; evaluation; assessment
8.  Selective Protection of Human Liver Tissue in TNF-Targeting of Cancers of the Liver by Transient Depletion of Adenosine Triphosphate 
PLoS ONE  2012;7(12):e52496.
Tumor necrosis factor alpha (TNF) is able to kill cancer cells via receptor-mediated cell death requiring adenosine triphosphate (ATP). Clinical usage of TNF so far is largely limited by its profound hepatotoxicity. Recently, it was found in the murine system that specific protection of hepatocytes against TNF's detrimental effects can be achieved by fructose-mediated ATP depletion therein. Before employing this quite attractive selection principle in a first clinical trial, we here comprehensively investigated the interdependence between ATP depletion and TNF hepatotoxicity in both in vitro and ex vivo experiments based on usage of primary patient tissue materials.
Primary human hepatocytes, and both non-tumorous and tumorous patient-derived primary liver tissue slices were used to elucidate fructose-induced ATP depletion and TNF-induced cytotoxicity.
PHH as well as tissue slices prepared from non-malignant human liver specimen undergoing a fructose-mediated ATP depletion were both demonstrated to be protected against TNF-induced cell death. In contrast, due to tumor-specific overexpression of hexokinase II, which imposes a profound bypass on hepatocytic-specific fructose catabolism, this was not the case for human tumorous liver tissues.
Normal human liver tissues can be protected transiently against TNF-induced cell death by systemic pretreatment with fructose used in non-toxic/physiologic concentrations. Selective TNF-targeting of primary and secondary tumors of the liver by transient and specific depletion of hepatocytic ATP opens up a new clinical avenue for the TNF-based treatment of liver cancers.
PMCID: PMC3525543  PMID: 23272249
9.  Dynamics of Tumor Hypoxia in Response to Patupilone and Ionizing Radiation 
PLoS ONE  2012;7(12):e51476.
Tumor hypoxia is one of the most important parameters that determines treatment sensitivity and is mainly due to insufficient tumor angiogenesis. However, the local oxygen concentration in a tumor can also be shifted in response to different treatment modalities such as cytotoxic agents or ionizing radiation. Thus, combined treatment modalities including microtubule stabilizing agents could create an additional challenge for an effective treatment response due to treatment-induced shifts in tumor oxygenation. Tumor hypoxia was probed over a prolonged observation period in response to treatment with different cytotoxic agents, using a non-invasive bioluminescent ODD-Luc reporter system, in which part of the oxygen-dependent degradation (ODD) domain of HIF-1α is fused to luciferase. As demonstrated in vitro, this system not only detects hypoxia at an ambient oxygen concentration of 1% O2, but also discriminates low oxygen concentrations in the range from 0.2 to 1% O2. Treatment of A549 lung adenocarcinoma-derived tumor xenografts with the microtubule stabilizing agent patupilone resulted in a prolonged increase in tumor hypoxia, which could be used as marker for its antitumoral treatment response, while irradiation did not induce detectable changes in tumor hypoxia. Furthermore, despite patupilone-induced hypoxia, the potency of ionizing radiation (IR) was not reduced as part of a concomitant or adjuvant combined treatment modality.
PMCID: PMC3519688  PMID: 23251549
10.  MVP and vaults: a role in the radiation response 
Vaults are evolutionary highly conserved ribonucleoproteins particles with a hollow barrel-like structure. The main component of vaults represents the 110 kDa major vault protein (MVP), whereas two minor vaults proteins comprise the 193 kDa vault poly(ADP-ribose) polymerase (vPARP) and the 240 kDa telomerase-associated protein-1 (TEP-1). Additionally, at least one small and untranslated RNA is found as a constitutive component. MVP seems to play an important role in the development of multidrug resistance. This particle has also been implicated in the regulation of several cellular processes including transport mechanisms, signal transmission and immune responses. Vaults are considered a prognostic marker for different cancer types. The level of MVP expression predicts the clinical outcome after chemotherapy in different tumour types. Recently, new roles have been assigned to MVP and vaults including the association with the insulin-like growth factor-1, hypoxia-inducible factor-1alpha, and the two major DNA double-strand break repair machineries: non-homologous endjoining and homologous recombination. Furthermore, MVP has been proposed as a useful prognostic factor associated with radiotherapy resistance. Here, we review these novel actions of vaults and discuss a putative role of MVP and vaults in the response to radiotherapy.
PMCID: PMC3216873  PMID: 22040803
major vault protein; radiotherapy; prognosis; radiation response
11.  Efficient Colonization and Therapy of Human Hepatocellular Carcinoma (HCC) Using the Oncolytic Vaccinia Virus Strain GLV-1h68 
PLoS ONE  2011;6(7):e22069.
Virotherapy using oncolytic vaccinia virus strains is one of the most promising new strategies for cancer therapy. In this study, we analyzed for the first time the therapeutic efficacy of the oncolytic vaccinia virus GLV-1h68 in two human hepatocellular carcinoma cell lines HuH7 and PLC/PRF/5 (PLC) in cell culture and in tumor xenograft models. By viral proliferation assays and cell survival tests, we demonstrated that GLV-1h68 efficiently colonized, replicated in, and did lyse these cancer cells in culture. Experiments with HuH7 and PLC xenografts have revealed that a single intravenous injection (i.v.) of mice with GLV-1h68 resulted in a significant reduction of primary tumor sizes compared to uninjected controls. In addition, replication of GLV-1h68 in tumor cells led to strong inflammatory and oncolytic effects resulting in intense infiltration of MHC class II-positive cells like neutrophils, macrophages, B cells and dendritic cells and in up-regulation of 13 pro-inflammatory cytokines. Furthermore, GLV-1h68 infection of PLC tumors inhibited the formation of hemorrhagic structures which occur naturally in PLC tumors. Interestingly, we found a strongly reduced vascular density in infected PLC tumors only, but not in the non-hemorrhagic HuH7 tumor model. These data demonstrate that the GLV-1h68 vaccinia virus may have an enormous potential for treatment of human hepatocellular carcinoma in man.
PMCID: PMC3133637  PMID: 21779374
12.  Improved reproducibility in preparing precision-cut liver tissue slices 
Cytotechnology  2009;61(3):145-152.
Precision-cut liver tissue slices (PCLS) have been used for decades to study pharmacological metabolism as well as toxicology and efficacy of novel substances on primary material under standardized conditions. Slicing of primary liver tissue has been done using different slicing machines. Since there has been great variability in the results, we sought to compare the reproducibility of tissue slices generated using the newly developed Leica VT1200 S vibrating blade microtome with Vibrocheck (LV) and the Krumdieck tissue slicer (KD) which has been the standard apparatus for this application so far. Liver samples from five different species (human, pig, cattle, rat, mouse) were cut and the reproducibility of slice thickness was analyzed by cross sectioning the PCLS. The quality of the sliced tissue was determined via measurement of the ATP content. As a result, we found an improved accuracy and reproducibility of rat, mouse and human tissue slices using the new Leica vibrating blade microtome.
PMCID: PMC2825296  PMID: 20091220
Primary culture; Precision-cut liver slices (PCLS); Leica VT1200 S vibrating blade microtome; Krumdieck tissue slicer
13.  Upregulation of α7 Nicotinic Receptors by Acetylcholinesterase C-Terminal Peptides 
PLoS ONE  2009;4(3):e4846.
The alpha-7 nicotinic acetylcholine receptor (α7-nAChR) is well known as a potent calcium ionophore that, in the brain, has been implicated in excitotoxicity and hence in the underlying mechanisms of neurodegenerative disorders such as Alzheimer's disease. Previous research implied that the activity of this receptor may be modified by exposure to a peptide fragment derived from the C-terminal region of the enzyme acetylcholinesterase. This investigation was undertaken to determine if the functional changes observed could be attributed to peptide binding interaction with the α7-nAChR, or peptide modulation of receptor expression.
Methodology/Principal Findings
This study provides evidence that two peptides derived from the C-terminus of acetylcholinesterase, not only selectively displace specific bungarotoxin binding at the α7-nAChR, but also alter receptor binding properties for its familiar ligands, including the alternative endogenous agonist choline. Of more long-term significance, these peptides also induce upregulation of α7-nAChR mRNA and protein expression, as well as enhancing receptor trafficking to the plasma membrane.
The results reported here demonstrate a hitherto unknown relationship between the α7-nAChR and the non-enzymatic functions of acetylcholinesterase, mediated independently by its C-terminal domain. Such an interaction may prove valuable as a pharmacological tool, prompting new approaches for understanding, and combating, the process of neurodegeneration.
PMCID: PMC2654408  PMID: 19287501
14.  Phase-locked mutants of Mycoplasma agalactiae: defining the molecular switch of high-frequency Vpma antigenic variation 
Molecular Microbiology  2008;67(6):1196-1210.
Mycoplasma agalactiae, an important pathogen of small ruminants, exhibits antigenic diversity by switching the expression of multiple surface lipoproteins called Vpmas (Variable proteins of M. agalactiae). Although phase variation has been shown to play important roles in many host–pathogen interactions, the biological significance and the mechanism of Vpma oscillations remain largely unclear. Here, we demonstrate that all six Vpma proteins are expressed in the type strain PG2 and all undergo phase variation at an unusually high frequency. Furthermore, targeted gene disruption of the xer1 gene encoding a putative site-specific recombinase adjacent to the vpma locus was accomplished via homologous recombination using a replicon-based vector. Inactivation of xer1 abolished further Vpma switching and the ‘phase-locked’ mutants (PLMs) continued to steadily express only a single Vpma product. Complementation of the wild-type xer1 gene in PLMs restored Vpma phase variation thereby proving that Xer1 is essential for vpma inversions. The study is not only instrumental in enhancing our ability to understand the role of Vpmas in M. agalactiae infections but also provides useful molecular approaches to study potential disease factors in other ‘difficult-to-manipulate’ mycoplasmas.
PMCID: PMC2268961  PMID: 18248580
15.  Artificial neural networks allow the use of simultaneous measurements of Alzheimer Disease markers for early detection of the disease 
Previous studies have shown that in platelets of mild Alzheimer Disease (AD) patients there are alterations of specific APP forms, paralleled by alteration in expression level of both ADAM 10 and BACE when compared to control subjects. Due to the poor linear relation among each key-element of beta-amyloid cascade and the target diagnosis, the use of systems able to afford non linear tasks, like artificial neural networks (ANNs), should allow a better discriminating capacity in comparison with classical statistics.
To evaluate the accuracy of ANNs in AD diagnosis.
37 mild-AD patients and 25 control subjects were enrolled, and APP, ADM10 and BACE measures were performed. Fifteen different models of feed-forward and complex-recurrent ANNs (provided by Semeion Research Centre), based on different learning laws (back propagation, sine-net, bi-modal) were compared with the linear discriminant analysis (LDA).
The best ANN model correctly identified mild AD patients in the 94% of cases and the control subjects in the 92%. The corresponding diagnostic performance obtained with LDA was 90% and 73%.
This preliminary study suggests that the processing of biochemical tests related to beta-amyloid cascade with ANNs allows a very good discrimination of AD in early stages, higher than that obtainable with classical statistics methods.
PMCID: PMC1198261  PMID: 16048651
16.  [alpha]-Secretase ADAM10 as well as [alpha]APPs is reduced in platelets and CSF of Alzheimer disease patients. 
Molecular Medicine  2002;8(2):67-74.
BACKGROUND: Members of membrane-bound disintegrin metalloproteinases (ADAMs) were shown to be capable of cleaving amyloid precursor protein (APP) at the alpha-cleavage site in different cell systems. One of the candidate alpha-secretases identified in this family is ADAM10. The present study addresses the following major questions: 1) Are the levels of an alpha-secretase candidate (i.e., ADAM10) reduced in accessible cells of Alzheimer Disease (AD) patients? 2) Are ADAM10 levels in the peripheral cells of AD patients related to a concomitant decrease in alpha APPs? MATERIALS AND METHODS: Western Blot analysis of ADAM10 is performed on platelet homogenates from 33 sporadic AD patients and on 26 age-matched control subjects. Moreover, the levels of alpha-secretase metabolite (alpha APPs) are tested both in platelets and cerebrospinal fluid (CSF) of the same pool of subjects by means of Western blot with a specific antibody. RESULTS: A significant decrease of platelet ADAM10 levels is observed in patients affected by probable AD when compared to control subjects and this is paralleled by a reduced level of alpha APPs released from platelets. Moreover, in the same pool of AD patients, alpha APPs levels were reduced concomitantly in CSF. CONCLUSIONS: ADAM10 is expressed in platelets. A reduced level of ADAM10 is observed in platelets obtained from AD patients compared to age-matched controls. Further, in the same pool of AD patients, a qualitatively and quantitatively similar decrease in alpha APPs is present both in thrombin-activated platelets and CSF, thus suggesting that alterations of APP processing might occur both in the neuronal compartment and peripheral cells.
PMCID: PMC2039975  PMID: 12080182

Results 1-16 (16)