Donor height in combination with islet donor score improves pancreas donor selection for pancreatic islet isolation and transplantation

To maximize the islet isolation yield for successful islet transplantation, the key task has been to identify an ideal pancreas donor. Since implementation of the islet donor score in donor selection, we have consistently obtained higher islet yields and transplantation rates. In this study, we tested whether assessing donor height as an independent variable in combination with the donor score could improve the pancreas donor selection. Donor and islet isolation information (n = 22) were collected and studied between 2011 and 2012. Pearson correlation analysis was used in statistical analysis. Donor height as an independent variable was significantly correlated to the weight of the pancreas, pre-Islet Equivalents (pre-IEQ), post-IEQ, and IDS (P < .05). When donor with height of 179 cm ± 3 was selected in combination with IDS > 80, the clinical islet transplantation rate reached 80%.

Application of Digital Image Analysis to Determine Pancreatic Islet Mass and Purity in Clinical Islet Isolation and Transplantation

Pancreatic islet mass, represented by islet equivalent (IEQ), is the most important parameter in decision making for clinical islet transplantation. To obtain IEQ, the sample of islets is routinely counted under a microscope and discarded thereafter. Islet purity, another parameter in islet processing, is routinely assessed by estimation only. In this study, we validated our digital image analysis (DIA) system by using the software of Image Pro Plus and a custom-designed Excel template to assess islet mass and purity to better comply with current good manufacturing practice (cGMP) standards. Human islet samples (60 collected from a single isolation and 24 collected from 12 isolations) were captured as calibrated digital images for the permanent record. Seven trained technicians participated in determination of IEQ and purity by the manual counting method (manual image counting, Manual I) and DIA. IEQ count showed statistically significant correlations between the Manual I and DIA in all sample comparisons (r > 0.819 and p < 0.0001). A statistically significant difference in IEQ between Manual I and DIA was not found in all sample groups (p > 0.05). In terms of purity determination, statistically significant differences between assessment and DIA measurement were found in high-purity 100-µl samples (p < 0.005) and low-purity 100-µl samples (p < 0.001) of the single isolation. In addition, islet particle number (IPN) and the IEQ/IPN ratio did not differ statistically between Manual I and DIA. In conclusion, the DIA used in this study is a reliable technique to determine IEQ and purity. Islet sample preserved as a digital image and results produced by DIA can be permanently stored for verification, technical training, and information exchange among islet centers. Therefore, DIA complies better with cGMP requirements than the manual counting method. We propose DIA as a quality control tool to supplement the established standard manual method for islet counting and purity estimation.

Chronic pancreatitis and primary sclerosing cholangitis--first report of intrahepatic autologous islet transplantation

BACKGROUND

We are reporting first successful intrahepatic autologous islet transplantation after total pancreatectomy in a patient with chronic pancreatitis and primary sclerosing cholangitis.

METHODS

Total pancreatectomy and subsequent islet autotransplantation were performed in a 16-year-old boy with intractable pain due to chronic pancreatitis in the setting of ulcerative colitis and primary sclerosing cholangitis (PSC). Liver biopsy revealed PSC with focal bridging fibrosis. The pancreas was surgically removed and digested, and islets were isolated, highly purified, and infused intraportally.

RESULTS

Over 18-month follow-up, the patient did not show progression of chronic liver disease or signs of portal hypertension. Magnetic resonance cholangiopancreatography revealed no new changes, and liver biopsy did not show progression of the periportal fibrosis. Pain medication was weaned over 12 months at which time glycemic control was excellent without exogenous insulin supplementation. HbgA1c was 5.9. Fifteen months after the procedure, stimulation with a mixed meal led to a fourfold increase of serum C-peptide and an eightfold increase of insulin level.

CONCLUSION

Pancreatic autologous islets can be successfully transplanted into a liver affected by PSC without compromising hepatic or graft function. Durability of the procedure may be limited in the future by the natural course of the liver injury caused by PSC.

Engraftment of human adipose derived stem cells delivered in a hyaluronic acid preparation in mice

PURPOSE

To evaluate the implant of human adipose derived stem cells (ADSC) delivered in hyaluronic acid gel (HA), injected in the subcutaneous of athymic mice.

METHODS

Control implants -HA plus culture media was injected in the subcutaneous of the left sub scapular area of 12 athymic mice. ADSC implants: HA plus ADSC suspended in culture media was injected in the subcutaneous, at the contra lateral area, of the same animals. With eight weeks, animals were sacrificed and the recovered implants were processed for extraction of genomic DNA, and histological study by hematoxilin-eosin staining and immunufluorescence using anti human vimentin and anti von Willebrand factor antibodies.

RESULTS

CONTROLS

Not visualized at the injection site. An amorphous substance was observed in hematoxilin-eosin stained sections. Human vimentin and anti von Willebrand factor were not detected. No human DNA was detected. ADSC implants - A plug was visible at the site of injection. Fusiform cells were observed in sections stained by hematoxilin- eosin and both human vimentin and anti von Willebrand factor were detected by immunofluorescence. The presence of human DNA was confirmed.

CONCLUSION

The delivery of human adipose derived stem cells in preparations of hyaluronic acid assured cells engraftment at the site of injection.

Calcium-activated and voltage-gated potassium channels of the pancreatic islet impart distinct and complementary roles during secretagogue induced electrical responses

Glucose-induced β-cell action potential (AP) repolarization is regulated by potassium efflux through voltage gated (Kv) and calcium activated (K(Ca)) potassium channels. Thus, ablation of the primary Kv channel of the β-cell, Kv2.1, causes increased AP duration. However, Kv2.1(-/-) islet electrical activity still remains sensitive to the potassium channel inhibitor tetraethylammonium. Therefore, we utilized Kv2.1(-/-) islets to characterize Kv and K(Ca) channels and their respective roles in modulating the β-cell AP. The remaining Kv current present in Kv2.1(-/-) β-cells is inhibited with 5 μM CP 339818. Inhibition of the remaining Kv current in Kv2.1(-/-) mouse β-cells increased AP firing frequency by 39.6% but did not significantly enhance glucose stimulated insulin secretion (GSIS). The modest regulation of islet AP frequency by CP 339818 implicates other K(+) channels, possibly K(Ca) channels, in regulating AP repolarization. Blockade of the K(Ca) channel BK with slotoxin increased β-cell AP amplitude by 28.2%, whereas activation of BK channels with isopimaric acid decreased β-cell AP amplitude by 30.6%. Interestingly, the K(Ca) channel SK significantly contributes to Kv2.1(-/-) mouse islet AP repolarization. Inhibition of SK channels decreased AP firing frequency by 66% and increased AP duration by 67% only when Kv2.1 is ablated or inhibited and enhanced GSIS by 2.7-fold. Human islets also express SK3 channels and their β-cell AP frequency is significantly accelerated by 4.8-fold with apamin. These results uncover important repolarizing roles for both Kv and K(Ca) channels and identify distinct roles for SK channel activity in regulating calcium- versus sodium-dependent AP firing.

Isolation of a highly myogenic CD34-negative subset of human skeletal muscle cells free of adipogenic potential

The differentiation of multipotent cells into undesirable lineages is a significant risk factor when performing cell therapy. In muscular diseases, myofiber loss can be associated with progressive fat accumulation that is one of the primary factors leading to decline of muscular strength. Therefore, to avoid any contribution of injected multipotent cells to fat deposition, we have searched for a highly myogenic but nonadipogenic muscle-derived cell population. We show that the myogenic marker CD56, which is the gold standard for myoblast-based therapy, was unable to separate muscle cells into myogenic and adipogenic fractions. Conversely, using the stem cell marker CD34, we were able to sort two distinct populations, CD34(+) and CD34(-), which have been thoroughly characterized in vitro and in vivo using an immunodeficient Rag2(-/-)gamma(c) (-/-) mouse model of muscle regeneration with or without adipose deposition. Our results demonstrate that both populations have equivalent capacities for in vitro amplification. The CD34(+) cells and CD34(-) cells exhibit equivalent myogenic potential, but only the CD34(-) population fails to differentiate into adipocytes in vitro and in vivo after transplantation into regenerative fat muscle. These data indicate that the muscle-derived cells constitute a heterogeneous population of cells with various differentiation potentials. The simple CD34 sorting allows isolation of myogenic cells with no adipogenic potential and therefore could be of high interest for cell therapy when fat is accumulated in diseased muscle.

Human multipotent adipose-derived stem cells differentiate into functional brown adipocytes

In contrast to the earlier contention, adult humans have been shown recently to possess active brown adipose tissue with a potential of being of metabolic significance. Up to now, brown fat precursor cells have not been available for human studies. We have shown previously that human multipotent adipose-derived stem (hMADS) cells exhibit a normal karyotype and high self-renewal ability; they are known to differentiate into cells that exhibit the key properties of human white adipocytes, that is, uncoupling protein two expression, insulin-stimulated glucose uptake, lipolysis in response to beta-agonists and atrial natriuretic peptide, and release of adiponectin and leptin. Herein, we show that, upon chronic exposure to a specific PPARgamma but not to a PPARbeta/delta or a PPARalpha agonist, hMADS cell-derived white adipocytes are able to switch to a brown phenotype by expressing both uncoupling protein one (UCP1) and CIDEA mRNA. This switch is accompanied by an increase in oxygen consumption and uncoupling. The expression of UCP1 protein is associated to stimulation of respiration by beta-AR agonists, including beta3-AR agonist. Thus, hMADS cells represent an invaluable cell model to screen for drugs stimulating the formation and/or the uncoupling capacity of human brown adipocytes that could help to dissipate excess caloric intake of individuals.

The influence of auranofin, a clinically established antiarthritic gold drug, on bone metabolism: analysis of its effects on human multipotent adipose-derived stem cells, taken as a model

Auranofin is a gold-based antiarthritic drug in clinical use for more that 25 years. However, in spite of a long established use, its specific effects on bone metabolism are still greatly controversial. We have analyzed in vitro the actions of auranofin on human multipotent adipose-derived stem (hMADS) cells, used as a model for bone metabolism, since these cells were reported to undergo osteogenesis both in vitro and in vivo. Cytotoxicity of auranofin on hMADS cells, differentiated into osteoblasts, was initially assessed. Thereafter, the consequences of exposure to nontoxic but clinically relevant auranofin concentrations were analyzed by monitoring the seleno-protein glutathione peroxidase 3 or alkaline phosphatase, a characteristic biomarker of osteogenesis. Notably, we found that chronic treatment with auranofin alters only weakly the levels of alkaline phosphatase, thus implying an overall modest effect on osteogenesis. In contrast, auranofin turned out to greatly affect glutathione peroxidase 3 activity. The possible medical implications of these findings are discussed.

Characterization of human mesenchymal stem cell secretome at early steps of adipocyte and osteoblast differentiation

Background

It is well established that adipose tissue plays a key role in energy storage and release but is also a secretory organ and a source of stem cells. Among different lineages, stem cells are able to differentiate into adipocytes and osteoblasts. As secreted proteins could regulate the balance between both lineages, we aimed at characterizing the secretome of human multipotent adipose-derived stem cell (hMADS) at an early step of commitment to adipocytes and osteoblasts.

Results

A proteomic approach, using mono-dimensional electrophoresis and tandem mass spectrometry, allowed us to identify a total of 73 proteins at day 0 and day 3 of adipocyte and osteoblast differentiation. Analysis of identified proteins showed that 52 % corresponded to classical secreted proteins characterized by a signal peptide, that 37 % previously described in the extracellular compartment were devoid of signal peptide and that 11 % neither exhibited a signal peptide nor had been previously described extracellularly. These proteins were classified into 8 clusters according to their function. Quantitative analysis has been performed for 8 candidates: PAI-1, PEDF, BIGH3, PTX3, SPARC, ENO1, GRP78 and MMP2. Among them, PAI-1 was detected at day 0 and day 3 of osteoblast differentiation but never in adipocyte secretome. Furthermore we showed that PAI-1 mRNA was down-regulated in the bone of ovariectomized mice.

Conclusion

Given its regulation during the early events of hMADS cell differentiation and its status in ovariectomized mice, PAI-1 could play a role in the adipocyte/osteoblast balance and thus in bone diseases such as osteoporosis.

Human adipose tissue-derived multipotent stem cells differentiate in vitro and in vivo into osteocyte-like cells

Cell-based therapies are used to treat bone defects. We recently described that human multipotent adipose-derived stem (hMADS) cells, which exhibit a normal karyotype, self renewal, and the maintenance of their differentiation properties, are able to differentiate into different lineages. Herein, we show that hMADS cells can differentiate into osteocyte-like cells. In the presence of a low amount of serum and EGF, hMADS cells express specific molecular markers, among which alkaline phosphatase, CBFA-1, osteocalcin, DMP1, PHEX, and podoplanin and develop functional gap-junctions. When loaded on a hardening injectable bone substitute (HIBS) biomaterial and injected subcutaneously into nude mice, hMADS cells develop mineralized woven bone 4 weeks after implantation. Thus hMADS cells represent a valuable tool for pharmacological and biological studies of osteoblast differentiation in vitro and bone development in vivo.

Constitutive activation of STAT proteins in the HDLM-2 and L540 Hodgkin lymphoma-derived cell lines supports cell survival

Survival and proliferation of Hodgkin lymphoma (HL) cells are influenced by many cytokines produced by different cell types in the lymph node microenvironment. STAT, family of transcription factors, are key mediators of cytokine signaling and their perturbation contributes to various human diseases. Electrophoretic mobility shift and phosphoprotein immunoblotting analyses were used to study STAT activation in HL cell lines. We thus observed high levels of constitutively activated STAT1, 3, 5 and 6 in HDLM-2 and L540 cells, which could be correlated with JAK kinase activation. In contrast KM-H2 cells did not display STAT activation. Preventing constitutive STAT activation by specific JAK kinases inhibitors induced apoptosis of HL cell lines and was associated with a strong decrease in the expression of the anti-apoptotic genes IAP-1, IAP-2, Bcl-xL, Bfl1 and Traf1. Silencing of JAKs by specific siRNAs also induced apoptosis of HL cells. Altogether, these results suggest that aberrant STAT activation in Hodgkin cells may promote cell survival and as a consequence facilitate oncogenic transformation.

Delta-interacting protein A, a new inhibitory partner of CCAAT/enhancer-binding protein beta, implicated in adipocyte differentiation

CCAAT/enhancer-binding protein beta (C/EBP beta) is expressed early during the adipocyte differentiation program and plays an important role in this process. In an attempt to identify novel proteins that interact with C/EBP beta, we performed a yeast two-hybrid screen with a preadipocyte cDNA library and identified a new co-regulator, delta-interacting protein A (DIPA). DIPA mRNA is expressed during adipocyte differentiation of clonal cell lines. DIPA interacts with C/EBP beta and -delta proteins in intact cells and inhibits their transcriptional activity but not that of C/EBP alpha. Stable overexpression of DIPA in preadipocytes partially inhibits adipocyte differentiation, whereas its gene silencing enhances this process. DIPA and C/EBP beta co-localize in the nucleus, and overexpression of DIPA in preadipocytes results in a partial inhibition of the mitotic clonal expansion which is critical for differentiation. Thus, DIPA is a novel partner of C/EBP beta that down-regulates early events of adipogenesis.

Ras and p53 intracellular targeting with recombinant single-chain Fv (scFv) fragments: a novel approach for cancer therapy?

Intracellular expression of recombinant antibodies allows one to interfere with the functions of oncogenic molecules expressed in various cell compartments and has therefore a vast clinical potential in cancer therapy. We inhibited the functions of oncogenic Ras mutant forms by intracellular expression of a neutralizing single-chain antibody (scFv). In vitro studies indicated that the scFv is expressed in the cytosol of Xenopus laevis oocytes and of tumor cells, blocks ras-mediated activation processes, and induces tumor cell death. In vivo studies performed using scFv cDNA inserted into an adenoviral vector showed that the scFv dramatically affects tumor growth. Second, intracellular expression of scFvs directed against p53 indicated that these antibody fragments can be successfully targeted to cell nucleus, bind p53, and partially restore the transcriptional activity of p53 mutants in human tumor cells. Thus, intracellular scFvs directed against oncogenic molecules may represent a new class of antitumor agents.

Carcinoembryonic antigen (CEA)-specific T-cell activation in colon carcinoma induced by anti-CD3 x anti-CEA bispecific diabodies and B7 x anti-CEA bispecific fusion proteins

Two bispecific recombinant molecules, an anti-CD3 x anti-carcinoembryogenic antigen (CEA) diabody and a B7 x anti-CEA fusion protein, were tested for their capacity to specifically activate T cells in the presence of CEA-expressing colon carcinoma cells. T-cell activation by the anti-CD3 x anti-CEA diabody required close contact to CEA-positive cells and resulted in diabody-mediated cytotoxicity against the target cells. Additionally, CD28-mediated costimulation in combination with anti-CD3 x anti-CEA diabodies induced activation of autologous T cells in CEA-positive primary colon carcinoma specimens, as determined by flow cytometry. The high specificity of the bispecific diabody approach could be further enhanced by the use of B7 x anti-CEA fusion proteins because the costimulatory CD28-signaling to the T cells strictly depended on the expression of CEA on the target cells. We demonstrate that displaying engagement sites for the T-cell antigens CD3 and CD28 on the surface of colon carcinoma cells is a suitable way to activate and retarget T cells in a highly tumor-specific manner. For clinical purposes, B7 x anti-tumor-associated antigen (TAA) fusion proteins, which are equally effective but more specific compared with anti-CD28 monoclonal anti-bodies, thus may improve the tumor specificity of anti-CD3 x anti-TAA bispecific antibodies. Furthermore, B7-negative tumors can be converted into B7-positive tumors by B7 x anti-TAA fusion proteins without the need for B7 gene transfer to the malignant cells.

A tumor specific single chain antibody dependent gene expression system

The design of conditional gene expression systems restricted to given tissues or cellular types is an important issue of gene therapy. Systems based on the targeting of molecules characteristic of the pathological state of tissues would be of interest. We have developed a synthetic transcription factor by fusing a single chain antibody (scFv) directed against p53 with the bacterial tetracycline repressor as a DNA binding domain. This hybrid protein binds to p53 and can interact with a synthetic promoter containing tetracycline-operator sequences. Gene expression can now be specifically achieved in tumor cells harboring an endogenous mutant p53 but not in a wild-type p53 containing tumor cell line or in a non-transformed cell line. Thus, a functional transactivator centered on single chain antibodies can be expressed intracellularly and induce gene expression in a scFv-mediated specific manner. This novel class of transcriptional transactivators could be referred as 'trabodies' for transcription-activating-antibodies. The trabodies technology could be useful to any cell type in which a disease related protein could be the target of specific antibodies.

Intracellular expression and functional properties of an anti-p21Ras scFv derived from a rat hybridoma containing specific lambda and irrelevant kappa light chains

A rat single-chain Fv (Y238 scFv) was derived from the Y13-238 monoclonal antibody, a non-neutralizing anti-Ras antibody. The Y13-238 hybridoma expresses two functional light chains. N-terminus microsequencing of these chains showed the presence of the Y3 Ag1.2.3 Vkappa chain derived from the rat fusion partner and of a rat Vlambda chain. Primers designed for rat Vlambda amplification allowed the cloning of a functional scFv that could bind p21Ras. The kinetics of interaction of purified Y238 scFv with the p21Ras protein was evaluated by BIAcore with a NTA sensor chip and gave an apparent affinity constant in the nanomolar range (K(D)=4.58+/-0.63 nM). Immunoprecipitation experiments of Y238 scFv expressed in Xenopus laevis oocytes confirmed the specificity of the scFv for the Ras protein. Y238 scFv could be intracellularly expressed in oocytes and in mammaliam cells without adverse effect on the Ras signalling cascade. This scFv was therefore used as control in experiments where another anti-Ras scFv (Y259 scFv, derived from the neutralizing anti-Ras mAb Y13-259) blocked the Ras pathway in vitro and led to tumor regression in a nude mouse model [Cochet, O., Kenigsberg, M., Delumeau, I., Virone-Oddos, A., Multon, M.C., Fridman, W.H., Schweighoffer, F., Teillaud, J.L., Tocqué, B., 1998. Intracellular expression of an antibody fragment-neutralizing p21 ras promotes tumor regression. Cancer Res. 58, 1170-1176.]. Finally, BIAcore analyses indicated that the epitopes recognized by Y238 and Y259 scFvs are not overlapping and allowed a more precise definition of the Y13-238 epitope.

Intracellular expression of an antibody fragment-neutralizing p21 ras promotes tumor regression

Mutated ras genes are found in a large number of human tumors and, therefore, constitute one of the primary targets for cancer treatment. Microinjection of the neutralizing anti-Ras monoclonal antibody Y13-259 was previously reported to induce transient phenotypic reversion of ras-transformed rodent fibroblasts in vitro. We have prepared a single-chain Fv fragment (scFv) derived from Y13-259, and here, we show that intracellular expression of the scFv led to the specific inhibition of the Ras signaling pathway in Xenopus laevis oocytes and NIH3T3 fibroblasts. Moreover, neutralizing Ras with the scFv specifically promoted apoptosis in vitro in human cancer cells but not in untransformed cells. As a step toward cancer gene therapy, we finally demonstrated that intratumor transduction of HCT116 colon carcinoma cells with the anti-Ras scFv using an adenoviral vector elicited sustained tumor regression in nude mice.

A new set of monoclonal antibodies against human Fc gamma RII (CD32) and Fc gamma RIII (CD16): characterization and use in various assays

Four mouse anti-human Fc gamma RII (CD32) (6C4, 2B2, 3D3, 93.4) (IgG1, kappa) and one anti-human Fc gamma RIII (CD16) (7.5.4) IgG1, kappa) MAbs were raised. An in vitro switch variant, 7.5.4Sw50 (IgG2b, kappa), was also derived from the 7.5.4 MAb. 6C4, 2B2, and 3D3 MAbs bind both Fc gamma RIIa and Fc gamma RIIb isoforms. Two of them (6C4 and 2B2 MAbs) allow a complete blockade of the binding of immune complexes to Fc gamma RII. All three MAbs immunoprecipitate the receptor and bind both its glycosylated and nonglycosylated forms. The fourth anti Fc gamma RII MAb, 93.4, directed against the intracellular region of Fc gamma RIIa1/2, allows its detection by Western blotting only when it is not phosphorylated. The 7.5.4 MAb binds both Fc gamma RIIIa and Fc gamma RIIIb, can be used in Western blotting and does not inhibit aggregated IgG binding. ELISA using IV.3 (anti-Fc gamma RIIa1/2)/6C4 and 3G8 (anti-Fc gamma RIIIa/b)/7.5.4Sw50 MAb pairs make it possible to detect soluble Fc gamma RIIa1/2 and Fc gamma RIII, with a sensitivity of 200 pg/mL and 1 ng/mL, respectively. Surface plasmon resonance analyses indicated that the KD of two of the three anti-Fc gamma RII and of the anti-Fc gamma RIII are in the same order of magnitude (6C4: 0.78 nM, 2B2: 0.28 nM, 7.5.4: 0.47 nM). The anti-Fc gamma RII 3D3 MAb exhibits an off-rate constant higher than the 6C4 and 2B2 MAbs and a KD of 2.19 nM.

Epitope mapping and tight-binding inhibition with monoclonal antibodies directed against Escherichia coli glucosamine 6-phosphate synthase

In the present work, we attempt to identify inhibitory monoclonal antibodies directed against Escherichia coli glucosamine-6P synthase (GlmS) and to localize the corresponding epitopes to better understand the topology of the enzyme during catalysis. Four of the 15 monoclonal antibodies have been shown to be specific for the native form of the enzyme and 2 of them, 505.1 and 522.2, strongly inhibit the glucosamine synthase activity. Kinetic analysis of 505.1 antibody behavior revealed a tight-binding inhibition with a Ki = 40 +/- 20 pM, a value which is four orders of magnitude lower than the best active site-directed inhibitor reported so far. The reactivity of all the monoclonal antibodies with 601 overlapping octapeptides covering the entire sequence of GlmS was tested by enzyme-linked immunosorbent assay for precise epitope mapping. Four linear epitopes specific for the denatured protein and one present in both native and denatured enzyme were defined by this approach. Neither 505.1 nor 522.2 was directed against linear epitopes. However, evidence for the binding of 505.1 at the glutamine catalytic site was shown by using site-directed mutants of GlmS as well as by competition experiments with an irreversible inhibitor. The mAb 105.1, which recognizes the octapeptide containing the sequence RWATHG conserved among the six glucosamine-6P synthases reported so far, allowed the detection of the human enzyme.

Phage libraries for generation of clinically useful antibodies

Insertion of antibody genes into filamentous bacteriophage makes it possible to generate and screen libraries of 10(7) or more antibodies. Each phage expresses an antibody on its surface and contains the corresponding antibody gene. Genes that encode antibodies with desired characteristics are readily selected and their antibodies expressed as soluble proteins in Escherichia coli. We used this system to produce an antibody to carcinoembryonic antigen with higher affinity and better tumour specificity than antibodies currently in use.

Coordinated regulation of amino sugar-synthesizing and -degrading enzymes in Escherichia coli K-12

The intracellular concentration of the enzyme glucosamine-6-phosphate synthase, encoded by the gene glmS in Escherichia coli, is repressed about threefold by growth on the amino sugars glucosamine and N-acetylglucosamine. This regulation occurs at the level of glmS transcription. It is not due just to the presence of intracellular amino sugar phosphates, because mutations which derepress the genes of the nag regulon (coding for proteins involved in the uptake and metabolism of N-acetylglucosamine) also repress the expression of glmS in the absence of exogenous amino sugars.

Monoclonal antibodies against bacterial glucosamine 6-phosphate synthase: production and use for structural studies

Fifteen mouse x rat hybridoma cell lines producing rat monoclonal antibodies (MAbs) directed to Escherichia coli Glucosamine 6-P Synthase (GlmS) were established and characterized. Most of them (13/15) are IgG2a while 2 were typed as IgG1. Their Kaff ranged from 1.5 x 10(6) to 9.6 x 10(8) M-1 as determined by Beatty et al. (1). The epitopes recognized by these MAbs were assigned to one of the two catalytical domains of the enzyme (CT1 and CT2) as demonstrated both by ELISA and Western-blotting using purified GlmS proteolytic fragments. The binding of the MAbs on either the native or denatured forms of GlmS, CT1 and CT2 was further analyzed by competitive immunoassay and most of the MAbs were found to bind preferentially to the denatured proteins. The study of the antigenic topography of GlmS by competitive radioimmunoassay demonstrated the existence of at least 10 independent epitopes on GlmS, divided into three groups. The first one (3/15) includes MAbs whose binding was not inhibited by any of the other MAbs. The second group (9/15) is comprised of MAbs that exhibit reciprocal binding inhibitory activity while the third group includes MAbs (3/15) presenting asymmetric inhibitory activity. Finally, since most of the isolated antibodies (10/15) bind to the 27 kDa amino-terminal glutamine binding domain (CT2), the capacity of these MAb to interfere with the associated glutaminase activity was analyzed.