Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07K—PEPTIDES
  • C07K14/00—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
  • C07K14/435—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans
  • C07K14/52—Cytokines; Lymphokines; Interferons
  • C07K14/53—Colony-stimulating factor [CSF]
  • C07K14/535—Granulocyte CSF; Granulocyte-macrophage CSF

Definitions

• the present invention relates to a method for purifying granulocyte-macrophage colony-stimulating factor (GM-CSF), particularly human GM-CSF.
• GM-CSF granulocyte-macrophage colony-stimulating factor
• the method of this invention provides for a particular series of purification steps which result in GM-CSF with high specific biological activity, high electrophoretic purity and a low level of pyrogens or other contaminants.
• Circulating blood cells are constantly replaced by newly developed cells.
• Replacement blood-cells are formed in a process termed hematopoiesis , in which at least eight mature blood cell lineages are produced: red blood cells (erythrocytes), macrophages (monocytes), eosinophilic granulocytes, megakaryocytes (platelets), neutrophilic granulocytes, basophilic granulocytes (mast cells), T lymphocytes, and B lymphocytes [see Burgess and Nicola, Growth Factors and Stem Cells (Acc.dem.ic Press, New York, 1983)].
• CSFs colony stimulating factors
• glycoproteins are so named because of the in vivo and in vitro assays used to detect their presence.
• Techniques for the clonal culture of hematopoietic cells in semisolid culture medium have been especially important in the development of in vitro assays.
• individual progenitor cells i.e., cells developmentally committed to a particular -lineage, but still capable of proliferation
• GM-CSF Complementary DNAs
• cDNAs Complementary DNAs
• GM-CSF Complementary DNAs
• cDNAs Complementary DNAs
• GM-CSF Complementary DNAs
• non-recombinant GM-CSF has been purified from culture supernatants of the Mo cell line (described in U.S. Patent 4,438,032), and the first sixteen amino acids from the N-terminus have been sequenced [Gasson et al. , Science, Vol. 226, pgs. 1339- 1342 (1984)].
• heterogeneity of the nucleotide sequence and amino acid sequence has been observed. For example, at the amino acid level both threonine and isoleucine have been observed at position 100 with respect to the N-terminal alanine, suggesting that several allelic forms, or polymorphs, of GM-CSF may exist within human populations.
• total mRNA is extracted from cells (e.g., a nontransformed human T cell source) producing polypeptides exhibiting the desired activity.
• the double-stranded cDNAs can be constructed from this total mRNA by using primer-initiated reverse transcrip ⁇ tion to make first the complement of each mRNA sequence, and then by priming for second strand synthesis. Subsequently, the cDNAs can be cloned by joining them to suitable plasmids or bacteriophage vectors through complementary homopolymeric tails or cohesive ends created with linker segments containing appropriate restriction sites, and then transforming a suitable host.
• a wide range of expression systems i.e., host/ expression-vector combinations
• host/expression-vector combinations can be used to produce the proteins purified by the process of this invention.
• Possible types of host cells include, but are not limited to, bacterial, yeast, insect, mammalian and the like.
• the present invention comprises a unique series of chromatographic steps which purify GM-CSF to more than 55% homogeneity, with the retention of biological activity, and in good yield.
• the procedure is composed of sequential anion- exchange, dye-ligand affinity, gel filtration and reversed-phase chromatography.
• the anion exchange column is used to remove proteases from the supernatant obtained after the host cells are killed and filtered off.
• Quaternary aminoethyl, mixed a ine or other intermediate base resins or weak base resins such as p-amino benzyl cellulose are particularly useful.
• Quaternary aminoethyl is a preferred anion exchange resin.
• the quaternary aminoethyl may be attached to a cross-linked dextran, cellulose, agarose or acrylic support.
• the dye-ligand affinity column is used to remove hydrophobic impurities.
• a typical column comprises a triazinyl dye such as Procion Red HE-3B on an agarose support (e.g., Matrex Gel Red A, manufactured by Amicon Corp., Scientific Systems Division, Danvers, MA).
• Gel filtration is used to separate high and low molecular weight impurities.
• a particularly useful filtration gel is a cross-linked dextran-based gel, identified by the trademark SEPHADEX G-100, manufactured by Pharmacia Fine Chemicals (Piscataway, N.J.).
• SEPHADEX G-100 cross-linked dextran-based gel
• the resin has a fractionation molecular weight range of 4,000 to 150,000 for globular proteins and peptides and 1,000 to 100,000 polysaccha ides.
• Other commercially available resins having cut-off ranges of from about 1,000 to about 200,000 for proteins may also be used.
• Reversed phase chromatography e.g. fast protein liquid chromatography (FPLC) and high pressure liquid chromatography (HPLC) has been found to be the only procedure capable of removing GM-CSF-related proteins identifiable on electrophoresis with no apparent denaturation of GM-CSF.
• Any C4 or C8 column may .be used, for example, PRORPC-C8 (manufactured by Pharmacia) for •FPLC and Dynamax-C4 or Dynamax-C8 (manufactured by Rainin Instruments Co., oburn, MA) for HPLC.
• the present invention relates to the purification of proteins having the sequence of the cDNA insert of clone pcD-human-GM-CSF illustrated below, which has been deposited with the American Type Culture Collection, Rockville, Maryland, under accession number 39923.
• Protein concentration is determined * at each stage by a Coomassie blue binding assay . pH measurements may vary by _+_ 0.2 pH units and conductivity measurements may vary by _+_ 3 mS . If the expected degree of purification is not achieved in any chromatographic procedure , eluted fractions may be re chroma tographed on the same type of column or, alternatively, recycled through, a previous step or a previous series of steps . An ammonium sulfate precipitation and/or ultraf iltration step may be performed to concentrate and/or store the protein, as e.g. in Stage III below .
• Cells are killed, for example by adjusting to •pH 2.0 (or less) by sequential additions of suitable acids, e.g. by adding 85% phosphoric acid to pH 4.5 and 50% trichloroacetic acid to pH 2.0. Substantially all of the suspension liquid is removed from the cells and discarded, a second suspension of the treated cells is prepared, said second suspension is neutralized, and the GM-CSF-containing liquid is separated from the suspended cells, e.g. by filtration through a 0.2 ⁇ membrane. The conductivity of the extract is then adjusted to 15-20 mS by addition of water. A low conductivity is required to minimize the amount of dilution required to allow GM-CSF to bind to the QAE column.
• suitable acids e.g. by adding 85% phosphoric acid to pH 4.5 and 50% trichloroacetic acid to pH 2.0.
• a second suspension of the treated cells is prepared, said second suspension is neutralized, and the GM-CSF-containing liquid is separated from the suspended cells, e
• the neutralized extract is adjusted to pH 7.5 with sodium hydroxide or hydrochloric acid, as appropriate.
• the conductivity of the neutralized extract is adjusted to 5-10 mS by addition of deionized water.
• the QAE column or other suitable anion exchange column is equilibrated with at least 2-3 column volumes of suitable pH 7.5 buffer, e.g. 20 mM Tris-HCl.
• the extract containing GM-CSF is applied to the column at a loading of not greater than 20 mg per ml of resin.
• the column is eluted with 10-20 column volumes of a gradient of sodium chloride in the range of 0-0.5 M dissolved in the same buffer in which the column was equilibrated.
• the combined fractions from the anion exchange (e.g. QAE) column are diluted with deionized water to a conductivity of 5-10 mS and loaded onto a dye-ligand affinity column, e.g. Procion Red HE3B attached to an agarose support, which had been previously equilibrated with 2-3 column volumes of appropriate pH 7.5 buffer, e.g. 20 mM Tris-HCl.
• the amount of protein loaded onto the column should not exceed 10 mg per ml of gel.
• the column is washed with 3-4 column volumes of the equilibration buffer. Elution is performed with between 5 and 15 volumes of a gradient of sodium chloride or other appropriate salt from 0 to 0.75 M dissolved in the equilibration buffer.
• the fractions to be employed in Stage IV are combined on the basis of SDS-PAGE.
• the solution is concentrated by ultrafiltration employing a 3,000-5,000 molecular weight cut-off membrane.
• the final protein concentration should be 1.0 mg/ml or greater.
• Ammonium sulfate is added to a final concentration of 60-70%.
• the precipitate is collected by centrifugation and then washed once with 20 mM Tris-HCl, pH 7.5, or other suitable buffer containing the same concentration of ammonium sulfate as employed for precipitation. The precipitate is collected by centrifugation and dissolved in the same buffer.
• Stage V Gel Filtration Chromatography
• the redissolved ammonium sulfate precipitate may be clarified by centrifugation, if required.
• the solution is filtered through a 0.2 u filter and charged onto a gel filtration column such as a Sephadex G-100 column equilibrated with an appropriate buffer at pH 7.5, e.g. 20 mM Tris-HCl.
• the amount of protein loaded onto the column should not exceed 3 mg per ml of gel.
• the column is eluted with the same buffer. Fractions for stage VI are combined based on SDS-PAGE.
• the combined fractions from the gel filtration are passed through a 0.2 ⁇ filter and applied to a reversed-phase column, e.g., FPLC or HPLC columns.
• a reversed-phase column e.g., FPLC or HPLC columns.
• the column is equilibrated with an acidic solution such as 0.1% trifluoroacetic acid (TFA) and elution is performed with a gradient of 0-100% of an inert solvent such as acetonitrile dissolved in the acidic solution.
• Fractions are combined based on SDS-PAGE.
• the solution is lyophilized and the dried powder is dissolved in a buffer solution at pH 7.2, e.g., 20 mM sodium phosphate.
• the solution from Stage VI is dialyzed against a buffer at pH 7.2, e.g., 20 mM sodium phosphate. Two changes of buffer are performed with a minimum of 4-5 hours between changes. If required, the dialyzed solution is concentrated by ultrafiltration using a 3,000-5,000 molecular weight cut-off membrane to a protein concentration of at least 1.0 mg/ml.
• the solution of purified GM-CSF is passed through a 0.2 ⁇ filter and stored frozen at about -20°C or below. Following is a specific example of GM-CSF purification. Roman numerals correspond to some of the Stages of the general description above.
• the neutralized protein extract was adjusted to pH 7.5 with sodium hydroxide. The extract was then diluted approximately 2-fold with cold deionized water to reach a final conductivity of 8 S.
• a 6.5 liter column (BIOPROCESS 252/15, manufactured by Pharmacia) was equilibrated with 3 column volumes of 20 mM Tris.HCl, pH 7.5. Extract (50 liters) was applied to the column at a loading of 8.6 mg protein per ml of resin.
• the column was eluted at a flow of 400 ml/ in, first with 30 liters of equilibration buffer, and then with 70 liters of a linear gradient established between 35 liters of 20 mM Tris.HCl, pH 7.5 and 35 liters of 20 mM Tris.HCl, pH 7.5 containing 0.4 M NaCl. Fractions (4-5 liters) were combined based on gel electrophoresis (SDS-PAGE) and the pooled protein (2.0 grams) was chromatographed in Stage III.
• the combined fractions from the QAE column were concentrated by ultrafiltration (3,000-5,000 molecular weight cut-off membrane) to 1 liter, and then diluted 5- fold with cold deionized water to a conductivity of 8 mS.
• This pool (5 liters) was then loaded at a ratio of 6.7 mg/ml onto a 300 ml Matrex Gel Red A column which had previously been equilibrated with three column volumes of 20 mM Tris.HCl, pH 7.5.
• the column was then washed with 600 ml of equilibrating buffer, and the 2.0 gram load was eluted using a linear gradient established between 1.5 liters of 20 mM Tris.HCl, pH 7.5 and 1.5 liters of 20 mM Tris.HCl, pH 7.5 containing 0.75 M NaCl.
• the fractions were combined based on gel electrophoresis, and the fractions (1.5 liters containing 1.12 gram of protein) were concentrated by ultrafiltration in Stage IV.
• the 1.5 liter eluate of the dye ligand chromatography contained 0.75 mg/ml. Ultrafiltration of this pool was performed in an Amicon high-output stainless steel stirred cell (Model 2000). A YM-5 membrane (150 mm) (Amicon) was used with a flow rate of 10 ml/min., 80 PSI and 4°C. The sample was concentrated to a volume of 75 ml and 10-15 mg/ml. Following the ultrafiltration, the sample was filtered through a .22 ⁇ cellulose nitrate membrane. Ammonium sulfate was added to a final concentration of 60% (390 mg/ml).
• the solution was held at 4°C without mixing for 2 hours, and then centrifuged at 4,000 rpm for 45 min at 4°C.
• the precipitate was collected, and resuspended in one liter of 20 mM Tris.HCl, pH 7.5 containing 60% saturated ammonium sulfate at 4°C.
• the sample was centrifuged at 4,000 rpm for 45 min at 4°C.
• the redissolved ammonium sulfate pellet was charged onto a 2 liter column at a flow rate of 2 ml/min. A loading ratio of 0.5 mg of protein per ml of resin was used and the sample was eluted with the equilibrating buffer, 20 mM Tris.HCl, pH 7.5. Fractions were combined based on gel electrophoresis (SDS-PAGE), and the 300 ml volume containing 350 mg of protein was frozen at -20°C until it was applied to the reversed- phase column. Stage VI. Reversed-Phase Column Chromatography
• the combined fractions of the gel filtration column were passed through a 0.2 ⁇ filter and applied onto a 20 ml PRORPC-C2/C8 (Pharmacia) column at a flow rate of 2.5 ml/min.
• the column had previously been equilibrated with solvent containing 0.1% TFA in water.
• Four identical chromatographies (100 mg per run) were performed. Sample was eluted using a linear gradient between 35% acetonitrile, 0.1% TFA and 100% acetonitrile, 0.1% TFA over a 125 min. time period. Fractions were combined based on SDS-PAGE. The solution was lyophilized, and the dried powder was dissolved in 20 mM sodium phosphate, pH 7.2.
• the pool from the reversed-phase column was dialysed against three changes of 20 mM sodium phosphate buffer, pH 7.2. The solution was then sterile-filtered through a 0.2 ⁇ filter and frozen at -20°C.

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