Purification and Characterization of Human Interleukin–1 Expressed in Escherichia coli

Preparation of Soluble Proteins from Escherichia coli

Purification of human IL-1β is used in this unit as an example of the preparation of a soluble protein from E. coli. Bacteria containing IL-1β are lysed, and IL-1 β in the resulting supernatant is purified by anion-exchange chromatography, salt precipitation, and cation-exchange chromatography, and then concentrated. Finally, the IL-1 β protein is applied to a gel-filtration column to separate it from remaining higher- and lower-molecular-weight contaminants, the purified protein is stored frozen or is lyophilized. The purification protocol described is typical for a protein that is expressed in fairly high abundance (i.e., >5% total protein) and accumulates in a soluble state. In addition, the purification procedure serves as an example of how to use classical protein purifications methods, which may also be used in conjunction with the affinity-based methods now more commonly used.

Preparation of soluble proteins from Escherichia coli

Purification of human IL-1beta is used in this unit as an example of the preparation of soluble proteins from E. coli. Bacteria containing IL-1beta are lysed, and IL-1 beta in the resulting supernatant is purified by anion-exchange chromatography, salt precipitation and cation-exchange chromatography, and then concentrated. Finally, the IL-1 beta protein is applied to a gel-filtration column to separate it from remaining higher- and lower-molecular-weight contaminants, the purified protein is stored frozen or is lyophilized. The purification protocol described is typical for a protein that is expressed in fairly high abundance (i.e., >5% total protein) and accumulates in a soluble state.

Inclusion bodies and purification of proteins in biologically active forms

Even though recombinant DNA technology has made possible the production of valuable therapeutic proteins, its accumulation in the host cell as inclusion body poses serious problems in the recovery of functionally active proteins. In the last twenty years, alternative techniques have been evolved to purify biologically active proteins from inclusion bodies. Most of these remain only as inventions and very few are commercially exploited. This review summarizes the developments in isolation, refolding and purification of proteins from inclusion bodies that could be used for vaccine and non-vaccine applications. The second section involves a discussion on inclusion bodies, how they are formed, and their physicochemical properties. In vivo protein folding in Escherichia coli and kinetics of in vitro protein folding are the subjects of the third and fourth sections respectively. The next section covers the recovery of bioactive protein from inclusion bodies: it includes isolation of inclusion body from host cell debris, purification in denatured state alternate refolding techniques, and final purification of active molecules. Since purity and safety are two important issues in therapeutic grade proteins, the following three sections are devoted to immunological and biological characterization of biomolecules, nature, and type of impurities normally encountered, and their detection. Lastly, two case studies are discussed to demonstrate the sequence of process steps involved.

Effects of interleukin-1 alpha on ovarian carcinoma in patients with recurrent disease

The aim of this study was to evaluate the safety and the biological effects of interleukin (IL-1 alpha) in patients' with recurrent ovarian carcinoma treated with carboplatin. In this phase I study, IL-1 alpha was administered by a continuous intravenous infusion at doses ranging 0.1-10 micrograms/m2 every 24 h for 4 days (96 h) 3 weeks before the first dose of carboplatin (400 mg/m2) in patients with potentially platinum-sensitive ovarian cancer. The maximum tolerated dose was 3 microgram/m2/day. Dose-limiting effects at 10 micrograms/m2/day were fever, chills, hypotension and fluid retention. Minor but objective antitumour effects were observed in 2 of 18 patients. 4 patients (including 1 with a minor response) had a decrease of the CA-125 serum level ranging from 33 to 39%. The trial design precluded evaluation of the duration of response to single-agent IL-1 alpha. Based on this trial design, there is evidence of minor antitumour effect to a single course of IL-1 alpha dose given prior to chemotherapy.

Expression and purification of recombinant ovine interleukin-1 beta from Escherichia coli

An expression vector bearing the gene segment encoding the mature form of ovine interleukin-1 beta (OvIL-1 beta) was constructed. This vector provided a rapid method for obtaining Escherichia coli derived recombinant OvIL-1 beta (rOvIL-1 beta) using the expression plasmid pGEX-2T. The level of expression of fusion protein in the soluble fraction was approximately 20% of the total accumulated proteins. Affinity purification by glutathione-Sepharose yielded a fusion protein and subsequent thrombin cleavage of this material yielded rOvIL-1 beta. The specific activity of the purified recombinant protein was 10(3)-10(4) times higher than the fusion protein. The rOvIL-1 beta was 10-100 times more potent than human interleukin-1 beta (HuIL-1 beta) in an ovine thymocyte proliferation assay, although they were of equal potency in the NOB-1/CTLL assay. This simple purification method, which produces purified rOvIL-1 beta with a high specific activity (approximately 10(8) U mg-1), will now make it possible to evaluate the in vivo effects of IL-1 beta in sheep.

Renaturation of recombinant proteins produced as inclusion bodies

Expression of recombinant proteins in Escherichia coli often results in the formation of insoluble inclusion bodies. Within the last few years specific methods and strategies have been developed to prepare active proteins from these inclusion bodies. These methods include (i) isolation of inclusion bodies after disintegration of cells by mechanical forces and purification by washing with detergent solutions or low concentrations of denaturant, (ii) solubilization of inclusion bodies with high concentrations of urea or guanidine-hydrochloride in combination with reducing reagents, and (iii) renaturation of the proteins including formation of native disulphide bonds. Renatured and native disulphide bond formation are accomplished by (a) either air oxidation, (b) glutathione reoxidation starting from reduced material, or (c) disulphide interchange starting from mixed disulphides containing peptides. The final yield of renatured proteins can be increased by adding low concentrations of denaturant during renaturation.

Monoclonal antibody 1994-01 (also known as ALVA 42) reported to recognize type II IL-1 receptor is specific for HLA-DR alpha and beta chains

Monoclonal antibody (MAb) 1994-01 has been reported to bind to the human type II Interleukin 1 (IL-1) receptor and in so doing block IL-1 binding in vitro and certain IL-1 mediated responses in vivo. While this antibody binds to a type II IL-1 receptor positive cell line, it can be shown that it does not bind to the type II IL-1 receptor. By direct expression cloning, we have identified two gene products, both of which are required for binding of this antibody. The two proteins are the alpha and beta subunits of the MHC class II antigen HLA-DR.

Cloning, expression and characterization of ovine interleukins 1 alpha and beta

Ovine interleukin 1 alpha (IL-1 alpha) c-DNA, obtained by polymerase chain reaction, has been cloned into pTZ18R and pTZ19R. The resulting DNA sequence shows close homology with the bovine sequence. The derived amino-acid sequence shows conserved motifs similar to those observed in all species studied so far. No signal peptide is seen. Northern blots of RNA from lipopolysaccharide (LPS)-stimulated ovine alveolar macrophages show IL-1 beta m-RNA to be produced earlier than and to be more transient than IL-1 alpha m-RNA. c-DNAs coding for the IL-1 alpha proprotein and IL-1 alpha and IL-1 beta mature proteins have been cloned and expressed in the yeast Ty-VLP system as fusion proteins. The resultant IL-1 protein preparations, cleaved from their fusion partners by the action of activated coagulation Factor Xa, are 80-95% pure and show biological activity in standard thymocyte co-mitogen and cartilage degradation assays for IL-1. Some species specificity is observed in that sheep thymocytes are more responsive to ovine rIL-1 than are mouse thymocytes. The presence of a Factor Xa cleavage site in the IL-1 alpha proprotein suggests that Factor Xa may be involved in the processing of ovine IL-1 alpha to its mature form.

Purification of interleukin-1 beta converting enzyme, the protease that cleaves the interleukin-1 beta precursor

We have purified the IL-1 beta converting enzyme from the THP-1 cell line using standard chromatographic techniques and obtained the N-terminal amino acid sequence of this novel protein. After stimulation of THP-1 cells with lipopolysaccharide, hydroxyurea, and silica, the protease was solubilized by multiple freeze/thawing. The protein was purified by ion-exchange chromatography, affinity chromatography on blue agarose, gel filtration, and chromatofocusing. The molecular weight of the protein is approximately 22,000 Da and the pI is between 7.1 and 6.8. The overall yield for this procedure was 16% of the activity found in the initial cell lysates. An antiserum raised against a peptide based on the N-terminus was used to precipitate the protease, confirming our identification of the 22,000-Da protein as the IL-1 beta converting enzyme.

Use of a dual-origin temperature-controlled amplifiable replicon for optimization of human interleukin-1 beta synthesis in Escherichia coli

A new dual-replicon recombinant plasmid, pPR53-tsr, has been constructed; it is a derivative of the expression vector pPR-TGATG-1 [Mashko et al., Gene 88 (1990) 121-126]. In contrast to its progenitor, pPR53-tsr is a low-copy-number (low-Cop) plasmid amplifiable in temperature-dependent fashion. In addition to both the replicon and the par locus from plasmid pSC101, providing segregational stability and a low Cop at 28 degrees C, the new plasmid contains a mutant ColE1 replicon whose RNAII is synthesized under the control of the pL promoter. The presence of a thermolabile repressor, cIts857, allows the thermo-inducible amplification of pPR53-tsr; the increased plasmid Cop is estimated at approx. 200 per genome 6 h after thermal induction at 42 degrees C. Thus, pPR53-tsr can be used as a donor of the thermo-inducible dual-replicon fragment for recombinant plasmids. Here, we employ such an approach for optimization of production of human interleukin-1 beta (hIL-1 beta) in Escherichia coli at a high level. The thermo-induced level of recombinant hIL-1 beta (re-hIL-1 beta) biosynthesis was around 9% of total cellular protein when the dual-replicon high-Cop vector was used. A method based on acidification of the water-soluble protein fraction to pH 4.0 has been developed that allows for the isolation of 80%-pure re-hIL-1 beta. The homogeneous material was obtained by two subsequent hydrophobic sorbent chromatographies. The protein yield ranged between 3-5 mg of re-hIL-1 beta/g of wet cells. The re-hIL-1 beta specific activity was about 2 x 10(8) units/mg, coinciding with that of the authentic hIL-1 beta.

High level expression of interleukin-1 beta in a recombinant Escherichia coli strain for use in a controlled bioreactor

A recombinant bacterial strain for the large scale production of human interleukin-1 beta (IL-1 beta) was constructed. The lambda Pr and the tryptophan systems were compared for efficiency of transcription and regulation. The efficiency of IL-1 protein production from these constructs was analyzed. Enhanced protein synthesis was achieved by the fusion of lambda Pr promoter sequences with trp leader sequences which included the trp RBS. A strain (JM101) was selected for use as a host and tested in a one liter bioreactor. A growth and induction regimen was established for use in bioreactors which results in the accumulation of 0.75-0.95 g l-1 of recombinant IL-1.

Secretion of N-glycosylated human recombinant interleukin-1 alpha in Saccharomyces cerevisiae

We have expressed fragments of the cDNA coding for mature human interleukin-1 alpha (hIL-1 alpha) in Saccharomyces cerevisiae. Mature hIL-1 alpha contains one potential N-linked glycosylation site that is not recognized in mammalian cells. Translational fusions to either one of three yeast signal sequences resulted in secretion of bioactive, N-glycosylated hIL-1 alpha. The extent of glycosylation was significantly reduced using the alpha-factor signal sequence, which itself contains three N-linked glycosylation sites known to be core glycosylated. N-glycosylation has no effect on biological specific activity.

Human recombinant interleukin-1 beta isolated from Escherichia coli by simple osmotic shock

A synthetic gene coding for the C-terminal 153 amino acids of the human interleukin-1 beta (IL-1 beta) was used to produce large quantities of recombinant IL-1 beta in Escherichia coli. The expression of the synthetic gene was under the control of an inducible promoter. The recombinant protein was released from the cells by an osmotic shock. This procedure did not lyse the cells. The IL-1 beta that represented 90% of the total extracted protein was purified to homogeneity by a single chromatographic step. Sequence analysis revealed a heterogeneous N-terminal sequence resulting from the cleavage of the N-terminal methionine in 50% of the molecules and of both the N-terminal methionine and alanine in the other 50%. This recombinant IL-1 beta had a specific activity of 1.3 x 10(8) international units per mg.

Comparison of biological and immunological activities of human monocyte-derived interleukin 1 beta and human recombinant interleukin 1 beta

Recombinant human interleukin 1 beta (rhIL-1 beta) and supernatants of Escherichia coli lipopolysaccharides-stimulated human monocyte (Mo) cultures, containing native human IL-1 beta (nhIL-1 beta), demonstrate significant differences when tested in the mouse co-stimulatory thymocyte (lymphocyte activating factor [LAF]) assay. The aims of the present study were to investigate this characteristic difference between rhIL-1 beta and Mo culture supernatants (Mo supernatants), and to compare the biological and the immunological activity of preparations of rhIL-1 beta and nhIL-1 beta during each step of an identical purification procedure. The biological activity of rhIL-1 beta/nhIL-1 beta preparations was characterized by the use of the LAF assay and the rat islet insulin release assay. An IL-1 beta enzyme-linked immunosorbent assay (ELISA) was established in order to compare the biological and immunological responses of the IL-1 beta preparations. We report that the significant difference between rhIL-1 beta and supernatants of Mo cultures, which was only demonstrable in the LAF assay, is due to the presence of interleukin 6 (IL-6) in the Mo supernatants. We describe a simple cation exchange chromatography separating nhIL-1 beta and IL-6 of Mo supernatants. The highly purified rhIL-1 beta possessing the correct amino-terminal sequence and nhIL-1 beta have identical biological and immunological activities demonstrating a specific biological activity (SBA) of 3 x 10(2) U/ng IL-1 beta. Thus, we have no indications of secondary or tertiary structural differences between rhIL-1 beta and purified nhIL-1 beta. In contrast, both in the LAF assay and in the rat islet insulin release assay the SBA of an amino-extended rhIL-1 beta form, Met-Glu-Ala-Glu-rhIL-1 beta, was only 1-2% of the SBA of rhIL-1 beta, suggesting that structural changes were introduced into the molecule by the amino-terminal extension. In the present study we have demonstrated that systematic combined testing of IL-1 beta preparations in two different biological assays and an immunological assay is useful for the characterization and comparison of the activity of recombinant and native IL-1 beta preparations purified by the use of exactly the same procedures.

Heterologous protein export in Escherichia coli: influence of bacterial signal peptides on the export of human interleukin 1 beta

Expression plasmids carrying the coding sequence of mature human interleukin 1 beta (IL 1 beta) linked either to a Met start codon, or fused to different efficient Escherichia coli secretion signal sequences, have been constructed. In the latter case, we used signal peptides derived either from an outer membrane protein (OmpA) or from a periplasmic protein (PhoA). The synthesis of IL1 beta from these fusions was investigated in an otherwise strictly isogenic context using identical conditions of derepression and culture media. The Met-IL1 beta fusion produced a soluble cytoplasmic protein which could be released from the cells by osmotic shock whereas the OmpA and PhoA fusions were always insoluble. The extent of sOmpA-IL1 beta maturation was found to vary from 50 to 100%, mainly depending on the medium used, whereas no significant maturation of the signal peptide could be detected in the case of the sPhoA-IL1 beta fusion. Immuno-electron microscopy revealed that the sOmpA-IL1 beta fusion was targeted to the inner membrane, whereas the sPhoA-IL1 beta fusion remained within the cytoplasm and thus did not appear to enter the secretion pathway. Amplifying the E. coli signal peptidase lep gene on a multicopy plasmid did not improve signal peptide removal from sOmpA-IL1 beta. Moreover, these E. coli secretion vectors allowed us to produce, in high levels, IL1 beta fragments which otherwise could not be stably accumulated within the cytoplasmic compartment.

One-step immunoaffinity purification of bioactive human recombinant IL-1 beta with a monoclonal antibody directed to a well-exposed domain of the protein

A monoclonal antibody (mAb) specific for human recombinant IL-1 beta (hu rIL-1 beta) was produced by immunizing BALB/c mice with hu rIL-1 beta purified with classical methods. This mAb recognizes an epitope within the highly hydrophylic fragment spanning amino acid 133-147. The affinity constant of this mAb towards IL-1 beta was determined by RIA. An affinity column was prepared by covalent binding of the mAb to Sepharose CL-4B. The column was capable of selectively binding hu rIL-1 beta produced in Escherichia coli directly from crude homogenates. The IL-1 beta protein yield was higher than 90% with a very good recovery of IL-1 beta biological activity. Moreover, the immunosorbent retained at least two thirds of its IL-1 beta-binding capacity after 20 cycles of purification.

Isolation and characterization of biologically active murine interleukin-1 alpha derived from expression of a synthetic gene in Escherichia coli

A murine interleukin-1 alpha (mIL-1 alpha) gene coding for amino acids 115 to 270 of the precursor protein (Lomedico, P.T., Gubler, U., Hellmann, C.P., Dukovich, M., Giri, J.G., Pan, Y.E., Collier, K., Semionow, R., Chua, A.O. and Mizel, S.B. (1984) Nature 312, 458-462) was chemically synthesized and expressed in Escherichia coli. mIL-1 alpha, in the form of insoluble inclusion bodies, accounted for approx. 30% of total cellular protein produced by the recombinant strain. A simple isolation protocol was developed in which inclusion body material was first solubilized in 3 M guanidine hydrochloride, and the mIL-1 alpha was then simultaneously purified and allowed to fold to its active conformation by dialysis against distilled water. This procedure yielded pure, biologically active mIL-1 alpha with 41% recovery of the mIL-1 alpha present in the guanidine hydrochloride extract. The purified preparation had the expected amino acid composition, a molar absorptivity of 28,200 M-1.cm-1 and a pI of 5.2. No methionyl-mIL-1 alpha was detected by N-terminal sequence analysis, and the endotoxin level was less than 10 pg per micrograms of mIL-1 alpha. The specific biological activity was 3.10(7) units/mg in a co-mitogenic thymocyte proliferation assay. In addition to full-length mIL-1 alpha, the preparation contained N-terminally truncated mIL-1 alpha species (mainly des-4 and des-6 amino acid forms). The truncated species were isolated and found to have the same biological activity as the complete polypeptide. Thus, the active fragment of mIL-1 alpha appears to consist of a proteinase-sensitive N-terminal region which is not essential for activity, and a proteinase-resistant core which harbors the essential determinants of its cytokine function.

Recombinant anaerobic maize aldolase: overexpression, characterization, and metabolic implications

Complementary DNA sequence of anaerobically induced cytoplasmic maize aldolase was expressed under control of the tac promoter sequence in Escherichia coli using the pKK223-3 plasmid as a vehicle. Levels of recombinant protein expressed exceeded 20 mg of soluble aldolase per liter of culture. The purified recombinant enzyme displayed the expected molecular weight and tetrameric subunit assembly on the basis of mobilities on denaturing electrophoretic gels and gel filtration, respectively. Sequencing of the NH2 terminus and amino acid composition analysis of the recombinant protein including COOH-terminal peptides agreed with the cDNA sequence. Partial kinetic characterization based on product inhibition studies was consistent with the ordered uni-bi reaction mechanism expected of aldolases. Turnover with respect to substrates Fru-1,6-P2 and Fru-1-P by the recombinant enzyme is the highest reported to date for class I aldolases. Fru-1,6-P2 cleavage rate by recombinant cytoplasmic maize enzyme is three times greater than that of the chloroplast enzyme. Fru-1-P cleavage is 8-fold greater than that of the rabbit liver isozyme and 20-fold greater than that of the rabbit muscle isozyme to which maize aldolase exhibits the greatest homology. The implications of such a high Fru-1-P turnover on carbohydrate utilization under anaerobiosis is discussed.

A two step purification of recombinant human interleukin-1 beta expressed in E. coli

Recombinant human interleukin-1 beta has been expressed in high yield using E. coli with a cDNA clone obtained from SKhep1RNA. The rIL-1 beta is purified to apparent homogeneity using freeze-thaw extractions followed by hydrophobic interaction chromatography over phenyl Sepharose. The procedure can provide pure rIL-1 beta (up to 15 mg per liter of E. coli culture) without the use of denaturants and if desired, in the absence of column chromatographic steps. Purity is defined by the presence of a single band on 1-D polyacrylamide gels and a single spot on 2-D polyacrylamide gels. The purified protein exhibits a biological activity of 1 x 10(7) units/mg in a fibroblast proliferation assay and is shown to cross-react with rabbit anti-human IL-1 beta sera.

Interleukin-1 immunoreactive innervation of the human hypothalamus

Interleukin-1 (IL-1) is a cytokine that mediates the acute phase reaction. Many of the actions of IL-1 involve direct effects on the central nervous system. However, IL-1 has not previously been identified as an intrinsic component within the brain, except in glial cells. An antiserum directed against human IL-1 beta was used to stain the human brain immunohistochemically for IL-1 beta-like immunoreactive neural elements. IL-1 beta-immunoreactive fibers were found innervating the key endocrine and autonomic cell groups that control the central components of the acute phase reaction. These results indicate that IL-1 may be an intrinsic neuromodulator in central nervous system pathways that mediate various metabolic functions of the acute phase reaction, including the body temperature changes that produce the febrile response.

High-cell density fermentation studies of recombinant Escherichia coli strains expressing human interleukin-1 beta

A high-productivity process has been developed for the production of mature human interleukin-1 beta (IL-1 beta) from recombinant Escherichia coli strains. Conditions were found that allow high IL-1 beta expression levels in high cell density cultures. Improved fed-batch fermentation strategies are described which include maintenance of glucose and acetate concentrations below 1 g/l and sparging the fermentor with an O2-enriched air supply. Using the E. coli tryptophan promoter control of transcription, a 2.2 g/l production level of IL-1 beta was achieved in E. coli B at cell densities of 55 g dry weight per litre. Another genetic construction involving the bacteriophage lambda cIts-PR expression cassette allowed a similar IL-1 beta production level (1.9 g/l) in E. coli E103S, albeit at a lower cell density (30 g/l). A simplified procedure allowing the purification of fully active IL-1 beta is also presented.