Plant-produced human recombinant erythropoietic growth factors support erythroid differentiation in vitro

Clinically available red blood cells (RBCs) for transfusions are at high demand, but in vitro generation of RBCs from hematopoietic stem cells requires significant quantities of growth factors. Here, we describe the production of four human growth factors: erythropoietin (EPO), stem cell factor (SCF), interleukin 3 (IL-3), and insulin-like growth factor-1 (IGF-1), either as non-fused proteins or as fusions with a carrier molecule (lichenase), in plants, using a Tobacco mosaic virus vector-based transient expression system. All growth factors were purified and their identity was confirmed by western blotting and peptide mapping. The potency of these plant-produced cytokines was assessed using TF1 cell (responsive to EPO, IL-3 and SCF) or MCF-7 cell (responsive to IGF-1) proliferation assays. The biological activity estimated here for the cytokines produced in plants was slightly lower or within the range cited in commercial sources and published literature. By comparing EC50 values of plant-produced cytokines with standards, we have demonstrated that all four plant-produced growth factors stimulated the expansion of umbilical cord blood-derived CD34+ cells and their differentiation toward erythropoietic precursors with the same potency as commercially available growth factors. To the best of our knowledge, this is the first report on the generation of all key bioactive cytokines required for the erythroid development in a cost-effective manner using a plant-based expression system.

A convenient method for preparation of an engineered mouse interleukin-3 analog with high solubility and wild-type bioactivity

Mouse interleukin-3 (mIL-3) is a critical cytokine regulator of myeloid cell differentiation, survival and activation, and consequently this cytokine has become a key reagent for hematological studies in the laboratory. Although bacterial expression has been used for the preparation of recombinant mIL-3 for more than 20 years, the resultant cytokine is known to exhibit poor solubility, be prone to aggregation, and may contain mispaired disulfide bonds. As a result, little structural characterization of mIL-3 has been possible to date. In the present work, we describe a convenient, inexpensive, and scalable protocol for preparing an mIL-3 analog with wild-type bioactivity from Escherichia coli via a simple purification scheme. This analog is typically expressed at >1 mg/l of shaking Super broth culture and, owing to solubility >5 mg/ml, structural studies in solution by nuclear magnetic resonance spectroscopy are feasible for mIL-3 for the first time.

Evaluation of refolding conditions for a human recombinant fusion cytokine protein, promegapoietin-1a

Conditions to obtain correctly folded PMP-1a (promegapoietin-1a), an engineered fusion IL-3 (interleukin-3) and thrombopoietin receptor agonist from recombinant Escherichia coli IBs (inclusion bodies), were defined to generate sufficient amounts of protein for evaluation as a potential therapeutic compound. Several ionic and non-ionic detergents, as well as the chaotrope urea, in combination with selected additives, were screened for their ability to dissolve IB protein and promote formation of monomeric, oxidized protein. Upon dissolution, soluble aggregates constituted 50-60% of total protein in detergent-solubilized IBs depending on the level of detergent used, whereas use of urea increased aggregation to approx. 70%. Subsequent addition of 5 mM cysteine or DTT (dithiothreitol) reduced the levels of aggregation, but never lower than approx. 20%. Refolds from detergent-solubilized IBs with or without organic modifiers characteristically produced multiple persistent misfolded species. However, the addition of a 12:1 molar excess of cystine (cystine/DTT) to urea-dissolved IBs containing DTT, followed by dilution, promoted the formation of correctly oxidized, disulfide-paired PMP-1a monomer with minimal misfolds present. Thus treatment of urea-dissolved proteins with thiol-group-containing additives and control of dilution, pH, protein concentration and order of addition were able to produce a maximum refold efficiency of 40-50% of correctly paired protein monomer.

Expression and purification of the recombinant diphtheria fusion toxin DT388IL3 for phase I clinical trials

A genetically engineered fusion toxin targeted to acute myeloid leukemia (AML) blasts was designed with the first 388 amino acid residues of diphtheria toxin with an H-M linker fused to human interleukin-3. The cDNA was subcloned in the pRK bacterial expression plasmid and used to transform BLR (DE3) Escherichia coli. A single transformed colony was grown in Superbroth with ampicillin; bacteria were centrifuged at an OD(650) of 1.3; master cell bank aliquots of bacteria in 30% glycerol/Superbroth were frozen and stored at -80 degrees C. Master cell bank bacteria were diluted 1500-fold into Superbroth and recombinant protein was induced with 1 mM IPTG at an OD(650) of 0.6. After two additional hours of fermentation, inclusion bodies were isolated, washed, and denatured in guanidine hydrochloride and dithioerythritol. Recombinant protein was refolded by diluted 100-fold in cold buffer with arginine and oxidized glutathione. After dialysis, purified protein was obtained after anion-exchange, size exclusion on FPLC, and polymyxin B affinity chromatography. The final material was filter sterilized, aseptically vialed, and stored at -80 degrees C. Seventy-five 3-L bacterial culture preparations were made and pooled for the AT-1 batch (568 mL) and twenty-four 3-L bacterial culture preparations were made and pooled for the AT-2 batch (169 mL). The final product was characterized by Coomassie Plus protein assay, Coomassie-stained SDS-PAGE, limulus amebocyte lysate endotoxin assay, human AML TF/H-ras cell cytotoxicity assay, sterility, tandem mass spectroscopy, IL3 receptor binding affinity, ADP ribosylation activity, inhibition of normal human CFU-GM, disulfide bond analysis, immunoblots, peptide mapping, stability, HPLC TSK3000, N-terminal sequencing, E. coli DNA contamination, C57BL/6 mouse toxicity, cynomolgus monkey toxicity, and immunohistochemistry. Yields were 25.7+/-5.6 mg/L bacterial culture of denatured fusion toxin. After refolding and chromatography, final yields were 20+/-11% or 5 mg/L. Vialed product was sterile. Batches were in 0.25 M sodium chloride/5 mM Tris, pH 8, and had protein concentrations of 1.8-1.9 mg/mL. Purity by SDS-PAGE was 99+/-1%. Aggregates by HPLC were <1 %. Potency revealed a 48 h IC(50) of 6-8 pM on TF/H-ras cells. Endotoxin levels were 1 eu/mg. The remaining chemical and biologic assays confirmed the purity, composition, and functional activities of the molecule. The LD(10) in mice was 250 microg/kg/day every other day for six doses. The MTD in monkeys was 60 microg/kg/day every other day for six doses. Drug did not react with tested frozen human tissue sections by immunohistochemistry. There was no evidence of loss of solubility, proteolysis aggregation, or loss of potency over 6 months at -80 and -20 degrees C. Further, the drug was stable at 4 and 25 degrees C in the plastic syringe and administration tubing for 24 h and at 37 degrees C in human serum for 24 h. The synthesis of this protein drug should be useful for production for clinical phase I/II clinical trials and may be suitable for other diphtheria fusion toxins indicated for clinical development.

[Methods of preparation of recombinant proteins-cytokines. IV. Renaturation of recombinant human interleukin-3]

Renaturation of recombinant human interleukin-3 produced as inclusion bodies in the transformed cells of Escherichia coli was studied and optimized. Importance was shown of removing from the protein solution the hydrophobic cellular components causing irreversible aggregation of the protein under renaturation conditions. An effect of pH on the secondary structure of the denatured protein was revealed by CD spectroscopy. It was thereby found that at pH 8.5, which is the optimal value for denaturation, the protein has the secondary structure most close to the native one. The isolation according to the scheme proposed allows preparation of interleukin-3 in 50% yield with 99% purity and biological activity 2 x 10(7) U/mg.

Expression, purification, refolding, and characterization of recombinant human interleukin-13: utilization of intracellular processing

Interleukin-13 (IL-13) is a pleiotropic cytokine that elicits both proinflammatory and anti-inflammatory immune responses. Recent studies underscore its role in several diseases, including asthma and cancer. Solution studies of IL-13 and its soluble receptors may facilitate the design of antagonists/agonists which would require milligram quantities of specifically labeled protein. A synthetic gene encoding human IL-13 (hIL-13) was inserted into the pMAL-c2 vector with a cleavage site for the tobacco etch virus (TEV) protease. Coexpression of the fusion protein and TEV protease led to in vivo cleavage, resulting in high levels of hIL-13 production. hIL-13, localized to inclusion bodies, was purified and refolded to yield approximately 2 mg per liter of bacteria grown in minimal media. Subsequent biochemical and biophysical analysis of both the unlabeled and (15)N-labeled protein revealed a bioactive helical monomer. In addition, the two disulfide bonds were unambiguously demonstrated to be Cys29-Cys57 and Cys45-Cys71 by a combined proteolytic digestion and mass spectrometric analysis.

Diphtheria toxin fused to human interleukin-3 is toxic to blasts from patients with myeloid leukemias

Leukemic blasts from patients with acute phase chronic myeloid leukemic and refractory acute myeloid leukemia are highly resistant to a number of cytotoxic drugs. To overcome multi-drug resistance, we engineered a diphtheria fusion protein by fusing human interleukin-3 (IL3) to a truncated form of diphtheria toxin (DT) with a (G4S)2 linker (L), expressed and purified the recombinant protein, and tested the cytotoxicity of the DTLIL3 molecule on human leukemias and normal progenitors. The DTLIL3 construct was more cytotoxic to interleukin-3 receptor (IL3R) bearing human myeloid leukemia cell lines than receptor-negative cell lines based on assays of cytotoxicity using thymidine incorporation, growth in semi-solid medium and induction of apoptosis. Exposure of mononuclear cells to 680 pM DTLIL3 for 48 h in culture reduced the number of cells capable of forming colonies in semi-solid medium (colony-forming units leukemia) > or =10-fold in 4/11 (36%) patients with myeloid acute phase chronic myeloid leukemia (CML) and 3/9 (33%) patients with acute myeloid leukemia (AML). Normal myeloid progenitors (colony-forming unit granulocyte-macrophage) from five different donors treated and assayed under identical conditions showed intermediate sensitivity with three- to five-fold reductions in colonies. The sensitivity to DTLIL3 of leukemic progenitors from a number of acute phase CML patients suggests that this agent could have therapeutic potential for some patients with this disease.

New fusion protein systems designed to give soluble expression in Escherichia coli

Three native E. coli proteins-NusA, GrpE, and bacterioferritin (BFR)-were studied in fusion proteins expressed in E. coli for their ability to confer solubility on a target insoluble protein at the C-terminus of the fusion protein. These three proteins were chosen based on their favorable cytoplasmic solubility characteristics as predicted by a statistical solubility model for recombinant proteins in E. coli. Modeling predicted the probability of soluble fusion protein expression for the target insoluble protein human interleukin-3 (hIL-3) in the following order: NusA (most soluble), GrpE, BFR, and thioredoxin (least soluble). Expression experiments at 37 degrees C showed that the NusA/hIL-3 fusion protein was expressed almost completely in the soluble fraction, while GrpE/hIL-3 and BFR/hIL-3 exhibited partial solubility at 37 degrees C. Thioredoxin/hIL-3 was expressed almost completely in the insoluble fraction. Fusion proteins consisting of NusA and either bovine growth hormone or human interferon-gamma were also expressed in E. coli at 37 degrees C and again showed that the fusion protein was almost completely soluble. Starting with the NusA/hIL-3 fusion protein with an N-terminal histidine tag, purified hIL-3 with full biological activity was obtained using immobilized metal affinity chromatography, factor Xa protease cleavage, and anion exchange chromatography.

Characterization of the isoforms of PIXY321, a granulocyte-macrophage-colony stimulating factor-interleukin-3 fusion protein, separated by preparative isoelectric focusing on immobilized pH gradients

We present here the purification and the characterization of the isoforms of PIXY321, a genetically engineered fusion of granulocyte-macrophage-colony stimulating factor and interleukin-3 expressed in yeast. The isoforms of PIXY321 were isolated using preparative isoelectric focusing (IEF) on immobilized pH gradients. Analysis of the collected fractions on analytical IEF gels showed that PIXY321 was resolved into four discrete isoforms of isoelectric point (pI) 5.0, 5.1, 5.2 and 5.3 with excellent yields. Subsequent analysis of purified isoforms of PIXY321 by peptide mapping and mass spectrometry linked the microheterogeneity of the original molecule to three parameters, the presence of deamidated residues, charged glycans and the pattern of O-linked glycosylation along the peptide sequence. This last parameter emphasizes the role of conformational aspects as key factors influencing the apparent isoelectric point of protein isoforms.

Characterization of the microheterogeneities of PIXY321, a genetically engineered granulocyte-macrophage colony-stimulating factor/interleukin-3 fusion protein expressed in yeast

PIXY321, a human cytokine analog genetically engineered by the fusion of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3), was expressed in yeast under the control of the alcohol dehydrogenase 2 (ADH2) promoter and the alpha-mating factor expression system. To provide the material necessary for the evaluation of PIXY321 in clinical trials, the production was scaled up to the 1200-1 scale and the PIXY321 molecule isolated by four successive steps of ion-exchange chromatography. Multiple heterogeneities, due to the presence of different patterns of glycosylation as well as multiple amino acid sequences at both N and C termini, were characterized on the purified molecule using complementary analytical techniques including electrophoresis, liquid chromatography and electrospray mass spectrometry. Four different N-terminal sequences were identified but simplified to a reproducible ratio of two sequences, the mature form and a form starting at Ala3, by adjustment of the process conditions. Molecules lacking 1-6 residues at the C-terminus were identified and their relative frequencies quantified. Amino acid modifications, such as three oxidized Met residues at positions 79, 141 and 187 and one deamidated Asn residue at position 176, were detected at low level. Microheterogeneities in glycosylation were characterized on four different sites, one located in the GM-CSF portion and three in the IL-3 portion of the molecule. The sites were shown to be differentially occupied and to carry 0-10 mannose residues according to their location in the sequence. Precise measurement of the heterogeneities at the molecular level were used to tune the process conditions and ensure reproducibility of the clinical product between lots.

Glycosylation does not affect in-vitro biological activity of interleukin-3

Murine interleukin-3 is secreted by activated T cells in three major molecular mass classes, which differ from one another in the extent of their N-linked glycosylation. Experiments were performed to determine whether carbohydrate content of different IL-3 glycoforms will affect their biological activity. IL-3 produced by activated T cells was biosynthetically labeled with 35S-methionine and the three major IL-3 glycoforms forms, with M(r) values of 22,000, 28,000 and 36,000, were purified using antibody affinity chromatography and preparative SDS-PAGE. Portions of these IL-3 glycoforms were enzymatically deglycosylated with N-glycanase and the bioactivity of each IL-3 glycoform and the corresponding deglycosylated fraction was compared in cell proliferation assays. The amount of 35S-label present in the samples was used as an index of protein amount so that equivalent concentrations of the various IL-3 forms could be compared. Our results indicate that the three major glycoforms have identical specific activity and that removal of N-linked carbohydrate does not change the specific in-vitro activity of IL-3. In addition to the three major glycoforms, small amounts of non-glycosylated IL-3 were also recovered from the affinity purified T-cell derived material. Using again the level of incorporated 35S as reference point, no difference in bioactivity compared with glycosylated IL-3 was detected. There is potential heterogeneity in IL-3 receptor complexes present on the many different cell types responsive to IL-3. We therefore tested whether the three IL-3 glycoforms differed in their interaction with various IL-3 responsive cell lines.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification of the murine interleukin 3 receptor

In this report we describe the purification of the murine interleukin 3 receptor (mIL-3R) to apparent homogeneity using a two-step procedure involving biotinylated mIL-3 (B-mIL-3) and affinity binding to immobilized antiphosphotyrosine and streptavidin agarose (SA). Purification was monitored using an assay for detergent solubilized-mIL-3Rs that utilized unglycosylated 125I-mIL-3 and concanavalin A (ConA)-Sepharose beads. The final material consisted of a 140-kDa tyrosine and serine phosphorylated protein that was greater than 98% pure as assessed by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis of either [35S]methionine-labeled, silver-stained, or radioiodinated preparations. Characterization of the purified receptor revealed that it migrated identically under reducing and nonreducing conditions in SDS gels, possessed 10 kDa of N-linked carbohydrate, and was cleaved upon storage at 4 degrees C to a 70-kDa form. These properties suggested that the purified mIL-3R was identical to that identified by cross-linking studies. The KD of the purified receptor was 1-5 nM, similar to estimates obtained using intact normal mouse bone marrow cells and mIL-3-dependent cell lines. The two-step purification procedure also isolated a 120-kDa serine phosphorylated but nontyrosine phosphorylated mIL-3R species. Apart from phosphorylation differences, the 140- and 120-kDa species were apparently identical, yielding, after alkaline phosphatase treatment, the same molecular mass on SDS gels and similar chymotryptic peptide maps. Amino acid sequences and composition data obtained from the more abundant and more stable serine phosphorylated 120-kDa mIL-3R, further purified by SDS-polyacrylamide gel electrophoresis, suggested that the purified mIL-3R may be identical to the predicted sequence of the recently isolated cDNA clone AIC2A. This was further suggested by comparing chymotryptic maps of the 120-kDa mIL-3R with the Aic2A protein and using antibodies corresponding to the amino and carboxyl termini of the AIC2A cDNA product. However, the Aic2A protein, when expressed on the surface of COS or 3T3 cells or following detergent solubilization and partial purification with biotinylated mIL-3 and SA, displayed a substantially lower affinity for mIL-3.

[Isolation of recombinant interleukin-3 produced by E. coli]

A synthetic gene coding for human interleukin-3 (hIL3) was cloned in the plasmid pTE2IL3, the gene expression being controlled by the phage fd PVIII promotor and the phage T7 gene 10 translational enhancer. Under constitutive biosynthesis conditions in E. coli, the accumulation of recombinant hIL3 (in the inclusion bodies) was up to 30-40% of the total cell protein. An effective procedure of the hIL3 isolation is suggested. The hIL3 was solubilized in 5 M guanidinium chloride, renaturated and purified to homogeneity by a single chromatographic step. The protein's yield was 34 mg/g wet cells. The isolated hIL3 showed a specific biological activity.

Purification and characterization of natural human interleukin-3

The human interleukin-3 gene was cloned in 1986 and the biochemical and biological properties of recombinant human interleukin-3 (rhuIL-3) protein were described. In this report we compare rhuIL-3 with nonrecombinant, natural huIL-3, purified from the supernatant of the human T cell leukemia line Jurkat. The main purification step, affinity chromatography, using a selected monoclonal anti-huIL-3 antibody, resulted in an approximately 40,000-fold enrichment of huIL-3. Combination of this step with ion-exchange and reverse-phase chromatography yielded natural huIL-3 of high purity (greater than 98%). A highly sensitive and specific sandwich ELISA, comprising two epitope-mapped monoclonal anti-huIL-3 antibodies, was used to quantitate huIL-3 during purification. Amino acid sequence determination revealed that the 38 N-terminal amino acids of Jurkat-derived huIL-3 are identical to the published sequence deduced from human fetal liver genomic DNA but differ in one residue from that derived from human T cell clones. The degree of glycosylation of Jurkat-derived huIL-3 was similar to Chinese hamster ovary cell-expressed rhuIL-3. Natural huIL-3 showed very similar biological activities to rhuIL-3 in proliferation and receptor binding assays utilizing huIL-3 responsive primary cells and cell lines, as well as in the human bone marrow colony assay.

Production of Human Interleukin-3 Using Industrial Microorganisms

We expressed a cDNA encoding the multicolony stimulating factor interleukin-3 in a variety of cell types, including bacteria, yeast and mammalian cells. After evaluation of the advantages and disadvantages of each potential system, we designed a production and purification scheme using Bacillus licheniformis. The purification consists of hydrophobic interaction chromatography, two steps of ion exchange chromatography and gel filtration. The purified and formulated product entered clinical trials in November 1989.

A simple three-step purification procedure for interleukin 3 involving absorption to fixed cells

We have found that treatment of B6SUtA1 cells with 0.01% glutaraldehyde transformed them into mechanically resistant spheres, thereby making it possible to use these high interleukin 3 (IL-3) receptor-bearing cells as a solid phase reagent suitable for the large scale purification of murine IL-3 (mIL-3). Using this technique, mIL-3 was purified from serum-free pokeweed mitogen-stimulated spleen cell-conditioned medium (PWM-SCCM) approximately 16,000-fold using absorption to B6SUtA1 cells, Sephadex G75 superfine chromatography, and reverse phase high performance liquid chromatography on a C18 column. The overall yield was 16%. The final product consisted of two proteins with molecular weights of 19.5 and 16.5 kd. Both species possessed mIL-3-like activity. N-glycanase treatment of the purified preparation converted all of the 19.5-kd material into the lower molecular weight species, suggesting that the two species represented different glycosylated states of mIL-3 produced by activated T cells. This was confirmed by competition studies that showed that excess pure Escherichia coli-derived recombinant mIL-3, but not granulocyte-macrophage colony-stimulating factor (GM-CSF), could prevent the binding of both species of the PWM-SCCM-derived material to B6SUtA1 cells.

A calcium-dependent antibody for identification and purification of recombinant proteins

We report a straightforward methodology for purification of recombinant proteins by incorporating a short hydrophilic peptide marker segment at their N-termini. A calcium-dependent antibody that reacts primarily with the first three amino acids of this peptide segment was used to affinity purify the fusion proteins in a single chromatographic step. The marker peptide could subsequently be removed by proteolysis with the enzyme enterokinase.

Partial purification of a mast cell growth-enhancing activity and its separation from IL-3 and IL-4

A growth factor acting synergistically with IL-3 on thiol-sensitive "mucosal type" bone marrow-derived mast cell lines, and therefore termed mast cell growth enhancing activity, is present in PWM stimulated spleen cell conditioned medium. Mast cell growth enhancing activity can be partially purified and completely separated from IL-3, IL-4, and IL-5, and for the most part from IL-6 and GM-CSF using strong cation exchange and Procion red affinity chromatography. Mast cell growth enhancing activity binds to Con A-Sepharose and can be digested with trypsin and chymotrypsin. It shows a Mr ranging from 37 to 43 kDa under nonreducing SDS-PAGE and a main isoelectric point ranging from 6.2 to 7.3.

Heterogeneity in human interleukin-3 receptors. A subclass that binds human granulocyte/macrophage colony stimulating factor

125I-Labeled recombinant human interleukin-3 (IL-3) was used to study the characteristics and distribution of receptors for IL-3 on human cells. Receptors were found on primary monocytes, on some strains of KG-1 cells, and on pre-B cell lines. Binding was rapid at 37 degrees C, while requiring several hours to reach equilibrium at 4 degrees C. Equilibrium binding studies indicated that IL-3 bound to a single class of high affinity receptor (less than 500 receptors/cell) with a Ka of approximately 1 x 10(10) M-1. Inhibition studies revealed that human granulocyte/macrophage colony stimulating factor partially inhibited the binding of 125I-IL-3 to human monocytes but not JM-1 cells. Additional analysis showed that on KG-1 cells, both IL-3 and GM-CSF partially competed specific binding of heterologous radiolabeled ligand, with approximately equivalent capacities. This competition occurred at both 37 and 4 degrees C. These results suggest heterogeneity in the binding sites for IL-3 and GM-CSF in which a subset of receptors binds only IL-3, a subset only GM-CSF, and another subset can bind both, all with high affinity. Additional heterogeneity was suggested by equilibrium binding of 125I-IL-3 to KG-1 cells which revealed a biphasic Scatchard plot containing a low affinity component not observed on monocytes and JM-1 cells.

Interleukin-3 down-regulates its own receptor

To gain insight into the mechanisms involved in regulating murine interleukin-3 (mIL-3) receptor expression, we have examined the effects of mIL-3 and murine granulocyte-macrophage colony-stimulating factor (mGM-CSF) on mIL-3 receptor internalization and re-expression and studied the relationship between mIL-3 cell surface receptor density and growth factor sensitivity. As a source of cells for our studies, we used a B6SUtA clone, B6SUtA1, which grows equally well in mIL-3 or mGM-CSF when supplemented with 20% fetal calf serum (FCS) in RPMI 1640. Intracellular processing studies carried out in the presence and absence of methylamine suggested that mIL-3 is cleaved at two specific sites before its complete digestion within lysosomes. However, unlike its ligand, cycloheximide studies indicated that internalized mIL-3 receptors are recycled to the cell surface. When B6SUtA1 cells were continuously passaged in mIL-3, cell populations allowed to exhaust the mIL-3 in the medium (high density cells) expressed more than ten times (ie, approximately 100,000/cell) the mIL-3 receptor number of those growing exponentially at low cell concentrations (low density cells). Since the high density cells were no larger than the low density cells, the marked increase in mIL-3 receptor number per cell reflects a true up-regulation of receptor expression. A kinetic analysis of this up-regulation revealed that it begins within one hour of mIL-3 exhaustion. Moreover, proliferation assays with these two cell populations, using 3H-thymidine incorporation, suggested that the high density cells were 30-fold more responsive to mIL-3. However, when B6SUtA1 cells were passaged in mGM-CSF, there was no difference in mIL-3 receptor number between high density and low density cells (ie, approximately 100,000/cell). Identical studies carried out with another mIL-3 dependent cell line, 32D C3, demonstrated that this phenomenon was not unique to B6SUtA1 cells.

Micropreparative capillary zone electrophoresis of recombinant human interleukin-3

Micropreparative capillary zone electrophoresis of recombinant human interleukin-3 (rhIL-3) in untreated fused silica is presented. Results show that nanogram quantities of rhIL-3 can be collected off the capillary and then identified by amino acid sequencing and SDS-gel electrophoresis.

The roles of factors from lung in murine megakaryocytopoiesis

The roles of factors from mouse lung in stimulating murine megakaryocytopoiesis were examined. Conditioned medium from normal mice was found to contain interleukin 3 (IL-3) activity in addition to granulocyte-macrophage colony-stimulating factor (GM-CSF) and megakaryocyte potentiator (Mk-potentiator). The Mk-potentiator activity of mouse lung-conditioned medium (MLCM) was found to be immunologically distinct from IL-3. Biochemical separation of MLCM showed Mk-potentiator activity with an activity profile distinct from IL-3 and GM-CSF. When titrated, Mk-potentiator was the major activity enhancing megakaryocyte colony formation in MLCM. By contrast, at high concentrations of MLCM, all factors were present and may play a role in megakaryocyte colony growth and development.

Capillary zone electrophoresis separation of recombinant human interleukin-3 and related proteins

Zone electrophoresis separations of human recombinant interleukin-3 (rh IL-3) and related proteins in untreated fused silica capillaries are presented. Results using pH 9 CHES buffer show that rh IL-3 is easily separated from a common carrier, human serum albumin, in a commercial preparation.

Keratinocyte-derived interleukin 3

Interleukin 3 (IL 3) initially was described as a cytokine which is produced by murine T lymphocytes and has multicolony stimulating factor (CSF) activity, activates mast cells and induces the proliferation of hematopoietic stem cell lines. In addition to T cells murine keratinocytes also produce an IL 3-like factor which according to its biological, biochemical and antigenic properties is indistinguishable from murine T cell IL 3. Moreover, by Northern blot analysis murine keratinocytes were found to express mRNA homologous to T cell IL 3 cDNA. Similarly, human keratinocytes have been shown to release an IL 3-like cytokine which also enhances the activity of natural killer cells and stimulates the release of oxygen radicals by granulocytes. However, human IL 3 mRNA could not yet be detected in human epidermal cells or epidermoid carcinoma cell lines. These findings indicate that human keratinocyte IL 3 appears to be distinct from T cell IL 3. Nevertheless, the exact nature of this cytokine remains to be clarified by sequence analysis and gene cloning. Through the production of these cytokines with IL 3-like capacity keratinocytes may participate in the regulation of the activity of different hematopoietic cells and thereby turn on early nonspecific host defense mechanisms against transformed cells and various harmful microbial organisms.

Multiple glycosylated forms of T cell-derived interleukin 3 (IL-3). Heterogeneity of IL-3 from physiological and nonphysiological sources

Interleukin 3 (IL-3) derived from mouse T cells was biosynthetically labeled with either [35S]methionine or [3H]mannose, affinity-purified using various anti-IL-3 antibodies, and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Autoradiography revealed the same three major bands with Mr values of 21,500-22,500, 27,000-31,000, and 32,000-36,000, irrespective of whether the anti-IL-3 antibody had been directed to the N or C termini of the IL-3 polypeptide. Bioassay of eluates from the gels confirmed that all three bands exhibited IL-3 bioactivity. IL-3 produced from two nonphysiological sources, the myelomonocytic leukemia WEHI-3B or Cos 7 cells that had been transfected with an IL-3 cDNA clone, had in each case a different pattern of microheterogeneity. Treatment with either tunicamycin or N-glycanase resulted in IL-3 running as one band with Mr 16,000, corresponding to its 140-amino acid polypeptide chain. No evidence for proteolytic processing was detected. These results show that the Mr heterogeneity of IL-3 was highly dependent on the cellular source and is due to N-linked glycosylation.

Production of recombinant human colony stimulating factors in yeast

Efficient yeast expression and purification systems for production of recombinant human GM-CSF, IL-3 and G-CSF have been established. Though yeast-derived production of recombinant CSFs (through the use of secretion based system) allows for generation of native molecules which can then be readily separated from fermentation broth, in many instances, natural cDNAs have had to be altered to allow for efficient expression, as well as production of a less heterogeneous product. In the case of CSFs described herein, beneficial mutations (made through site-directed mutagenesis) have included elimination of potential N-linked glycosylation sites, removal of KexII protease recognition sites (notably alterations in dibasic sequences) and elimination of extraneous cysteine residues which might complicate isolation of a homogeneous product due to intermolecular disulfide bonding.

Keratinocyte-derived granulocyte/macrophage colony-stimulating factor induces DNA synthesis by peritoneal macrophages

Keratinocytes have been demonstrated to produce a number of cytokines, including growth factors such as the CSF IL-3. Circulating blood monocytes and some elicited macrophages retain a significant proliferative potential in response to colony-stimulating activity. Because a macrophage response is prominent in a variety of cutaneous immune reactions, we have studied the ability of conditioned media (CM) from a transformed murine keratinocyte cell line (PAM 212) and from normal murine keratinocytes to induce growth of peritoneal macrophages. CM from both normal and transformed keratinocyte cultures induces [3H]thymidine incorporation by thioglycollate-elicited, but not resident, peritoneal macrophages. IEF of PAM 212 CM reveals peaks of activity at pI 4.8 and less than or equal to 4.2. Analysis of CM by reversed-phase HPLC demonstrates active fractions that elute at 46 to 48% and 53 to 55% acetonitrile. The Mr of the 46 to 48% acetonitrile factor is 25 to 30 kDa by gel filtration HPLC. Polyclonal anti-granulocyte/macrophage (GM) CSF antibody blocks the induction of macrophage [3H]thymidine incorporation by factors with pI 4.8 and eluting at 46 to 48% acetonitrile but does not reduce the activity of crude CM or the factor eluting at 53 to 55% acetonitrile. Based on both physiochemical criteria and antibody neutralization, keratinocytes produce GM-CSF. Keratinocyte-derived factors, including GM-CSF, may play an important role in regulating cutaneous macrophage responses.

Histamine-producing cell-stimulating activity. A biological activity shared by interleukin 3 and granulocyte-macrophage colony-stimulating factor

The histamine-producing cell-stimulating factor (HCSF) was first described as a lymphokine which is produced during secondary mixed leukocyte culture and which induces increased histamine synthesis by murine hematopoietic cells. It has been shown that it is different from interleukin 3 (IL 3), despite the fact that pure IL 3 expresses HCSF activity. Our results provide evidence that this factor (constitutively produced by the P388 D1 cell line) is identical with granulocyte-macrophage colony-stimulating factor (GM-CSF) i.e.: (a) physiochemical properties of HCSF and GM-CSF, such as molecular weight, isoelectric charge, hydrophobicity and behavior during affinity chromatography, are indistinguishable and both activities coelute during all biochemical purification procedures; (b) increased bone marrow cell histamine synthesis induced by P388 D1-derived HCSF is inhibited by anti-GM-CSF antiserum; (c) the GM-CSF cDNA probe hybridizes with a poly(A)+RNA from P388 D1 cells while no hybridizing signal was obtained with poly(A)+RNA from WEHI-3 and from P815 cells. On the other hand, the IL 3 cDNA probe hybridizes with a 1.0-kb poly(A)+RNA from WEHI-3 but not with those from P388 D1 and P815. Moreover, well known sources of GM-CSF, such as lung conditioned medium and semi-purified GM-CSF from phytohemagglutinin-induced supernatant of the murine T lymphoma LBRM-33-5 A4 (preparation devoid of IL 3), as well as recombinant murine GM-CSF, induce increased histamine synthesis by hematopoietic cells. All these results demonstrate that, in our culture conditions, the P388 D1 cell line spontaneously produces GM-CSF which is responsible for the P388 D1-induced HCS activity. Consequently, the latter is a property shared by the two distinct hematopoietic growth factors acting on the less committed cells, i.e. IL 3 and GM-CSF, whereas M-CSF or G-CSF are unable to induce histamine production. Interestingly, IL-4 which is known to support established mast cell line proliferation cannot induce HCS activity. In addition, none of the other cytokines tested, such as IL 1, IL 2, interferons or tumor necrosis factor can express HCS activity. This expression seems to be a specific property of IL 3 and GM-CSF.

Role of carbohydrate in the function of human granulocyte-macrophage colony-stimulating factor

cDNA clones for the human hematopoietic regulator granulocyte-macrophage colony-stimulating factor (hGM-CSF) were isolated from a lamba gt11 cDNA library prepared from RNA of COS cells transiently expressing the gene for hGM-CSF. As the RNA was a rich source of hGM-CSF mRNA, approximately 0.1% of the clones of this library contained hGM-CSF sequences. All of the clones analyzed were full length and were correctly processed. When subcloned into an expression vector and transfected into COS cells, the cDNA clones direct the synthesis of higher levels of the growth factor than the gene from which they were derived. The cDNA for native hGM-CSF was used to generate structural mutants which lack N-linked carbohydrate, O-linked carbohydrate, or both. Although the mutant proteins had differing specific activities, the nonglycosylated forms reproduce many, if not all, of the physiologic functions of authentic hGM-CSF. The role of carbohydrate in the secretion and function of hGM-CSF is discussed.

Characterization of recombinant human granulocyte-colony-stimulating factor produced in mouse cells

Mouse C127I cells were transformed with a chimeric plasmid consisting of bovine papillomavirus DNA and human granulocyte-colony-stimulating factor (G-CSF) cDNA placed under the control of the SV40 early promoter. The transformed cells secreted constitutively a high level of human G-CSF, 10-20 micrograms/ml in a low-serum medium. The secreted G-CSF has been purified to homogeneity by a two-step procedure including gel filtration and hydrophobic column chromatography. The purified recombinant G-CSF runs as a single band with an apparent Mr of 19,000 on a polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. This value corresponds to that of the native human G-CSF purified from the medium conditioned by human carcinoma CHU-2 cells. The recombinant human G-CSF was as active as native G-CSF in vitro in supporting proliferation of mouse NFS-60 cells and stimulating colony formation from human as well as mouse bone marrow cells. When the recombinant human G-CSF was subcutaneously administrated into mice, a remarkable stimulation of granulopoiesis and splenomegaly was observed.

Multilineage synergistic activity produced by a murine adherent marrow cell line

We reported previously that a cell line (TC-1) derived from adherent marrow cells produced colony-stimulating factor 1 (CSF-1) and a separate activity that acts synergistically with CSF-1 to stimulate giant macrophage colonies. We now report that an activity in TC-1 conditioned media (CM) separate from CSF-1 also synergizes multilineage colony formation by pure interleukin 3 (IL 3) and a crude source of granulocyte-macrophage colony-stimulating activity (GM-CSA) (murine lung-conditioned media). IL 3-induced megakaryocyte colony formation is also synergized. The CSF-1-dependent synergistic activity is not blocked by antibodies to IL 3 and is characterized as a nondialyzable (mol wt cutoff 3,000), heat-stable (56 degrees C, 30') activity that binds to DE-52 cellulose under conditions in which IL 3 does not. This material has an apparent mol wt of approximately 200,000 by Sephadex G100 chromatography, and the bulk of it binds to Concanavalin A (Con A) and elutes off with alpha-methyl mannoside, indicating that it is a glycoprotein. As reported separately, these purified active fractions also have a pre-B cell-inducing activity. In addition, a non-IL 3 activity stimulates proliferation of the factor-dependent cell lines FDC-P1 and DA-1. These data indicate that an adherent marrow cell line produces a growth factor(s) that synergizes with IL 3, GM-CSA, and CSF-1 and induces pre-B cell formation. This may be an important regulator of early multilineage lymphohemopoiesis.

Purification and properties of bacterially synthesized human granulocyte-macrophage colony stimulating factor

Human granulocyte-macrophage colony stimulating factor (GM-CSF) has been synthesized in high yield using a temperature inducible plasmid in Escherichia coli. The human GM-CSF is readily isolated from the bacterial proteins because of its differential solubility and chromatographic properties. The bacterially synthesized form of the human GM-CSF contains an extra methionine residue at position 1, but otherwise it is identical to the polypeptide predicted from the cDNA sequence. The specific activity of 2.9 X 10(7) units/mg of protein for purified bacterially synthesized human GM-CSF indicates that despite the lack of glycosylation, the molecule is substantially in its native conformation. This molecule stimulated the same number and type of both seven- and 14-day human bone marrow colonies as the CSF alpha preparation from human placental conditioned medium. Human GM-CSF had no activity on murine bone marrow or murine leukemic cells. There was no detectable, direct stimulation of adult human erythroid burst forming units (BFU-E) by the bacterially synthesized human GM-CSF. Although impure preparations containing native human GM-CSF (eg, human placental conditioned medium) stimulated the formation of mixed colonies, even in the presence of erythropoietin, the bacterially synthesized human GM-CSF failed to stimulate the formation of mixed colonies from adult human bone marrow cells. The bacterially synthesized human GM-CSF increased N-formyl-methionyl-leucyl-phenylalanine (FMLP)-induced superoxide production and lysozyme secretion. Antibody-dependent cytotoxicity and phagocytosis by human neutrophils was stimulated by the bacterially synthesized human GM-CSF and eosinophils were also activated in the antibody-dependent cytotoxicity assay.

Granulocyte colony-stimulating factor and differentiation-induction in myeloid leukemic cells

The granulocyte colony-stimulating factor (G-CSF) belongs to a family of hemopoietic growth factors regulating the production of granulocytes and macrophages. Murine G-CSF stimulates the proliferation and differentiation of precursors of neutrophilic granulocytes and is also able to stimulate the functional activities of mature neutrophils. Among the hemopoietic growth factors, G-CSF has an outstanding capacity to induce terminal differentiation and suppression of self-renewal in myeloid leukemic cells. Murine and human G-CSF's show complete biological cross-reactivity across species and bind equally well to G-CSF receptors of either species. Specific receptors for G-CSF exist on all normal neutrophilic cells and have not been lost in the generation of primary human myeloid leukemias. This data indicates that G-CSF may be a useful reagent in the treatment of myeloid leukemia, in hemopoietic regeneration and in increasing resistance against infections.

Human granulocyte-macrophage colony-stimulating factor purified from a Hodgkin's tumor cell line

Human granulocyte-macrophage colony-stimulating factor (GM-CSF) was purified from 3 liters of serum-free conditioned medium of the Hodgkin's tumor cell line L428 KSA. The conditioned medium contained a high specific activity of 2.5 X 10(5) units of total colony-stimulating factor per mg protein. Colony-stimulating factor activity was determined by colony formation by human fetal liver cells or mouse bone marrow cells. The latter bioassay discriminated colony-stimulating factor 1, a subclass specific for monocyte/macrophage production, and G-CSF, specific for granulopoiesis, from GM-CSF. The starting material contained predominantly GM-CSF with CSF-1 and G-CSF constituting 10% and 12%, respectively, of the total activity. A seven-stage purification scheme was employed. The first stage involved concentration by batch chromatography on calcium phosphate gel. Subsequent stages involved gel filtration on Ultrogel AcA44, affinity chromatography on concanavalin A-Sepharose, batch chromatography on calcium phosphate gel and high-performance liquid chromatography on C1 reversed-phase (TSK TMS-250), gel permeation and C8 reversed-phase columns. The purified material showed a single disperse band, having an Mr of 30,000, by silver staining on sodium dodecyl sulfate polyacrylamide gel electrophoresis. An amino-terminal sequence of 20 amino acids was determined in a gas-phase sequencer with 500 ng of purified material. The sequence was identical to that predicted from the cDNA sequence. It was active on human fetal liver cells with half-maximum colony formation at 1 X 10(-12) M, but was not active on mouse bone narrow cells.