Repeated cleaning of protein A affinity column with sodium hydroxide

Protein A attached to an affinity adsorbent was shown to be remarkably resistant to 0.5 M NaOH. Even repeated treatments gave only a small decrease in functional capacity and no adverse effect on leakage of the protein A into the eluate. This simple cleaning procedure should be useful in applications where antibodies need to be purified free from the risk of contamination with endotoxins or micro-organisms, e.g., for in vivo therapy, either in clinical trials or experimental animals. It can also prevent cross-contamination when the same protein A adsorbent is used for different batches of antibody.

Single-step recovery of a secreted recombinant protein by expanded bed adsorption

We have used an expanded bed adsorption procedure for efficient recovery of a recombinant fusion protein, directly from a crude fermentor broth without prior cell removal. The fusion protein was designed to have a relatively low isoelectric point (pI) to allow anionic exchange adsorption at pH 5.5 where most Escherichia coli host proteins are not adsorbed. The gene product was secreted to the culture medium of the E. coli host cells in high yields (550 mg/l). The separation of cells and the concentration and recovery of the fusion protein could therefore be achieved by a single unit operation. The yield after the expanded bed adsorption exceeded 90 percent. Furthermore, the significant volume reduction by the expanded bed adsorption, enabled efficient and straight-forward polishing of the product by a subsequent affinity chromatography step, for removal of contaminating DNA and pyrogenic compounds to levels acceptable for regulatory authorities. An overall yield exceeding 90 percent was maintained after the affinity chromatography polishing step. The procedure outlined here is suitable for large-scale bioprocesses and allows efficient removal of cells, host proteins, contaminating DNA and endotoxins.

An expression system for secretion and purification of a genetically engineered thermostable chimera of protein A and alkaline phosphatase

A chimera between gene segments of Protein A and a mutated alkaline phosphatase (lysine328 mutated to alanine) of Escherichia coli has been constructed. This chimeric gene was cloned in a T7 promoter-based IPTG-inducible expression vector. The chimeric protein was expressed in E. coli and was efficiently secreted into the periplasm, from which it could be easily purified by a combination of ion-exchange and gel permeation chromatography. The purified chimera was found to be thermostable and exhibited both IgG binding and high alkaline phosphatase activity. It was used as a probe in enzyme-linked immunosorbent assays and results indicate that it is a promising substitute for secondary antibodies in enzyme-linked immunoassays.

Bacteriophage surface display of an immunoglobulin-binding domain of Staphylococcus aureus protein A

As a model system for the optimization of separation ligands by bacteriophage surface display, we have constructed a phage surface expression system for a single immunoglobulin-binding domain of Protein A of Staphylococcus aureus. Protein A domain B is genetically fused to the gpIII adsorption protein of the filamentous bacteriophage M13, and hence displayed on the phage surface. Phage displaying the Protein A domain are selectively retained on human IgG-sepharose. Retention is due to specific Protein A-IgG interactions, as demonstrated by competitive inhibition by soluble Protein A or polyclonal human IgG. Polyclonal goat IgG, which is known to bind less well to Protein A than does human IgG, inhibits phage adsorption less effectively. Phage expressing Protein A can be purified in a few rounds of selective adsorption from a vast excess of wild type phage. Diverse libraries constructed by mutagenesis of this construct will allow massive screening of mutant forms of Protein A for alterations in binding and elution properties. We anticipate that phage display will prove to be a widely-applicable method of identification and optimization of affinity ligands for separations.

Determination of the human liver UDP-glucuronosyltransferase 2B4 domains involved in the binding of UDP-glucuronic acid using photoaffinity labeling of fusion proteins

The interactions between UDP-glucuronic acid and two human liver UDP-glucuronosyltransferase 2B4 peptides (14-150 and 299-446) purified from E. coli as Staphylococcus aureus protein A fusion proteins have been investigated. Photoaffinity labeling with azidonucleotides ([beta-32P]5N3UDP-Glucuronic acid and [beta-32P]5N3UDP-Glucose) and competition experiments with UDP-glucuronic acid and structurally related compounds emphasized the presence of a specific UDP binding site between amino acids 299 and 446. Moreover, competition experiments strongly suggested an interaction between the amino terminal part of the protein and glucuronic acid. It would involve an electrostatic bond in the binding of the cosubstrate via the carboxyl group of UDP-glucuronic acid and a positively charged amino acid of the N-terminal domain of the enzyme.

An improved strategy for determining resonance assignments for isotopically enriched proteins and its application to an engineered domain of staphylococcal protein A

Sequence-specific resonance assignments provide the basis for interpreting multidimensional NMR spectra and for determining 3D structures of proteins from these data. We have developed an improved strategy for determining these sequence-specific NMR assignments in small proteins and applied this method in determining proton and nitrogen resonance assignments for an 8.2-kDa engineered domain (the Z-domain) of the cell wall protein A of Staphylococcus aureus. First, HCCNH-TOCSY [Lyons, B. A. & Montelione, G.T. (1993) J. Magn. Reson. 101B, 206] data were used together with 2D 2QF-COSY, TOCSY, and 15N-HSQC data to identify amino acid spin systems. Most asparagine and glutamine spin systems were also identified uniquely from these triple-resonance data. Next, complementary HCC(CO)-NH-TOCSY [Montelione, G. T., et al. (1992) J. Am. Chem. Soc. 114, 10975] data were used to identify sequential connections from the aliphatic H alpha, H beta, H gamma, H delta, and H epsilon resonances of residue i to the amide and nitrogen resonances of residue i + 1. By combined analysis of HCCNH-TOCSY and HCC(CO)NH-TOCSY spectra we have determined most of the proton and nitrogen resonance assignments for the Z-domain. This represents the first example of the use of this triple-resonance technique to determine extensive resonance assignments in a small protein.

The membrane binding C-terminus of protein A from Staphylococcus aureus affects its cellular localization and causes structural deformation when expressed in Escherichia coli

Protein A from Staphylococcus aureus is a powerful diagnostic reagent and has several uses in human disease therapy. Expression in non-pathogenic Escherichia coli containing recombinant plasmids coding for this protein has increased its availability, but can reduce the stability of the plasmid-bearing host. By employing immune electron microscopy, we have determined that E. coli containing stable plasmids coding for a truncated version of protein A, without the membrane binding site, secrete this protein through the cytoplasmic membrane and into the periplasmic space, where it accumulates. E. coli containing unstable plasmids, however, which code for the complete protein including the membrane-binding site, target the protein into the cytoplasmic membrane. This accumulation of protein A in the E. coli cytoplasmic membrane inhibits the formation of septa between dividing cells and results in aberrant elongated, multi-chromosomal forms.

Immobilization and recovery of fusion proteins and B-lymphocyte cells using magnetic separation

A new approach to facilitate immobilization and affinity purification of recombinant proteins and selected human B lymphocytes has been developed. Using magnetic beads with attached DNA containing the Escherichia coli lac operator, fusion proteins comprising the DNA-binding lac repressor could be affinity-purified and recovered by gentle elution conditions, such as with a lactose analogue or by enzymatic means using either deoxyribonuclease (DNase) or restriction endonucleases. The results show for the first time that a DNA-binding protein can be used for affinity purification of fusion proteins as exemplified by the specific and gentle recovery of beta-galactosidase and alkaline phosphatase from bacterial lysates using immunomagnetic separation. The approach was further extended to cell separation by the efficient recovery and elution of human CD37 B lymphocytes from peripheral blood.

Fusions to the 5' end of a gene encoding a two-domain analogue of staphylococcal protein A

A novel gene fusion system has been constructed for fusions to the 5' end of gene zz, encoding a two-domain analogue of staphylococcal protein A designated ZZ. Four different genes were fused to the 5' end of zz, and their gene products were analyzed. One of the genes encodes a protein located intracellularly in Escherichia coli and the other three genes encode gene products destined for secretion across the cytoplasmic membrane by the presence of an amino terminal signal sequence. After production in E. coli, the fusion proteins were purified in a single step by IgG-affinity chromatography. The purified ZZ fusions could be used directly for amino terminal sequencing to confirm the start of translation of the intracellular product and the processing of the signal peptide of the translocated products. This is the first example of ZZ fusions to the C-terminus of gene products. To simplify the general use of fusions to the 5' end of zz, a new plasmid vector was constructed containing a multi restriction enzyme cloning linker and the lacZ' gene which enables screening for production in alpha-complementing supE strains of E. coli on indicator plates.

Affinity purification of antibodies using immobilized FB domain of protein A

A continuous method for the efficient digestion of protein A into active fragments (FB, Mr = 7000) using immobilized trypsin was developed. These fragments originate from almost identical five-repeated monovalent Fc-binding units of 58 residues each. The fragments obtained were found to be similar to the recently described genetically engineered fragment B. Antibody-binding characteristics of the FB domain and also of intact protein A, immobilized on to adipic dihydrazide-modified Eupergit CB6200 beads, were investigated. Based on the experimental data obtained, a high-performance liquid chromatographic column containing C30N Eupergit C-immobilized FB domain was prepared and its performance in antibody purification was compared with that of Eupergit C-immobilized intact protein A.

A modified vector for the controlled high-level overproduction of staphylococcal protein A fusion proteins in the periplasm of Escherichia coli

A vector encoding the Staphylococcal protein A was modified by cloning the spa gene, including its signal peptide-encoding sequence, downstream of the translation initiation sites of the phage lambda cro gene and under the control of the temperature-inducible phage lambda pR promoter. The expression from this construct was studied using the Escherichia coli phoA gene as a reporter gene after fusion to the spa gene. Determination of alkaline phosphatase activity, 1 h after temperature induction of expression at 42 degrees C, revealed an 800-fold increase over host strain background level. The presence of the alternating selectable markers on the described vector, pHEMa153, which are essential for efficient oligonucleotide-directed construction of mutations by the gapped duplex DNA method, allows the construction of recombinant and mutated forms of Staphylococcal protein A fusion proteins and efficient expression of spa gene fusions without changing the vector system.

Influenza C virus infection in France

Little is known of the epidemiology of influenza C virus infections in western Europe and of the exact role of this agent in acute viral respiratory infections. Several tests may be used for detecting antibodies against this agent but the significance of their respective results is not clear. A total of 301 samples of serum was collected from persons aged from 4 months to 88 years living in France in 1988. The samples were tested for the presence of antibodies to influenza C virus by haemagglutination-inhibition (HI) tests and ELISA. The specificity of the results was checked by immunoblotting and by antibody absorption with staphylococcal protein A. Significant HI activity was found in 61% of the 301 samples tested, titres ranging from 20-320; 70% were positive by ELISA with titres ranging from 500 to 32,000. The population tested was divided into four age groups: 0-15 years; 16-30 years; 31-50 years and 51-88 years. The highest rates for positive samples were found in the 16-30 year group (76 and 79% by HI tests and ELISA respectively) as well as significant HI and ELISA geometric mean titres. Positive samples were less common in young children (46 and 50% by HI tests and ELISA respectively) and in the oldest group (44 and 54% respectively). The 31-50 years age group formed an intermediate class. The high prevalence of antibody as well as the significant titres indicate intense circulation of influenza C virus, especially among young adults.

Biologically active and amidated cecropin produced in a baculovirus expression system from a fusion construct containing the antibody-binding part of protein A

A synthetic antibody-binding part derived from protein A from Staphylococcus aureus was used as a fusion partner in a eukaryotic expression system employing Autographa californica nuclear polyhedrosis as a vector. This, in conjunction with an efficient signal sequence, facilitated the purification of the antibacterial peptide cecropin A from the medium of Spodoptera frugiperda cells infected with a recombinant virus. In order to increase further the concentrations of fusion protein, Trichoplusia ni larvae were used as host. Cecropin A could be obtained after cleavage of the fusion protein with CNBr. Biological activity as well as the correct structure including the C-terminal amide group was shown using electrophoresis with detection of antibacterial proteins and mass spectroscopy.

Immunoassay to measure staphylococcal protein A in the presence of murine immunoglobulins

Immunoassays designed to measure low concentrations of staphylococcal protein A are subject to varying degrees of interference by excess IgG. We have developed an enzyme-linked immunosorbent assay (ELISA) that overcomes this problem by analyzing IgG-containing protein A samples in solutions buffered at pH 3.5. Under these carefully selected conditions, protein A is absorbed efficiently by solid-phase chicken anti-protein A antibodies, but protein A-IgG complexes are largely dissociated. The assay has a protein A detection limit of 0.1 ng/ml, and the response is unaffected by 0.25 mg/ml murine IgG. The method should be useful for determining protein A contamination levels in antibodies purified by affinity chromatography on immobilized protein A resins.

A two-cycle immunoprecipitation procedure for reducing nonspecific protein contamination

A two-cycle immunoprecipitation procedure is described that markedly reduces nonspecific protein contamination occurring during the precipitation of hepatic lipase from rat H4 hepatoma cells. In this method, the precipitation of immune complexes during both cycles is achieved by utilizing a sodium dodecyl sulfate (SDS)-washed preparation of lyophilized Staphylococcus aureus cells (Staph A); this washed preparation effectively removes Staph A contaminants without compromising the ability to bind immune complexes. Following initial immunoprecipitation of the antigen, the Staph A/IgG/antigen complex containing coprecipitated nonspecific proteins was dissociated with SDS. Triton X-100 was added to the dissociated immunoprecipitate at a concentration (by weight) of at least 5 parts Triton X-100 to 1 part SDS. A second cycle of immunoprecipitation was then initiated by addition of fresh antibody, followed by Staph A precipitation of immune complexes and analysis by SDS-polyacrylamide gel electrophoresis. The two-cycle procedure is shown to be reproducible and suitable for the quantitative determination of relative amounts of hepatic lipase. The procedure described here is generally applicable to the immunoprecipitation of other antigens.

Expression in Escherichia coli of the genes coding for reaction center subunits from Rhodobacter sphaeroides: wild-type proteins and fusion proteins containing one or four truncated domains from Staphylococcus aureus protein A at the carboxy-terminus

Gene cassettes were constructed containing Rhodobacter sphaeroides puhA, pufM and pufL sequences with synthetic 5' ends for production in Escherichia coli of the H, M and L subunits of the photosynthetic reaction center. In addition, gene cassettes coding for fusion proteins with proteinase recognition site(s) between the amino-terminal part of H, M or L subunits, and the carboxy-terminal part consisting of one (B') or four (D'ABC') domains of Staphylococcus aureus protein A were constructed. A modified expression vector pDS12/RBSII containing the T5 promoter PN25, the lac operator, and a newly inserted E. coli lipoprotein ribosome-binding site was used. Inducible synthesis of plasmid-encoded polypeptides was accompanied by reduced growth. The products comigrated with R. sphaeroides reaction center subunits H, M and L. They were identified by Western blot experiments using antibodies raised against reaction center proteins. The hybrid protein containing the reaction center H subunit fused to the single domain B' was not detected by nonspecific antisera. In contrast, the three fusion proteins containing domains D'ABC' were identified using nonspecific antisera. This indicated that domains D'ABC' were sufficient to bind to the Fc part of IgG molecules, whereas domain B' was not sufficient. This property was used to purify all three fusion proteins with domains D'ABC' by affinity chromatography from the membrane fraction of E. coli cells.

Preparation of a genetically fused protein A/luciferase conjugate for use in bioluminescent immunoassays

The genes encoding staphylococcal protein A and bacterial luciferase (Vibrio harveyi) were fused in-frame in order to obtain a general marker enzyme for bioluminescent immunoassays. Two constructs were made where protein A was ligated to the first and the 12th amino acid residue, respectively, of the N terminus of the beta subunit of luciferase. Only the first fusion protein encoding the entire beta subunit was able to form an enzymatically active luciferase complex when expressed together with the alpha subunit. The fusion of protein A to luciferase did not notably alter the emitted wavelength spectrum or its stability to urea treatment. The fusion protein was found to retain at least 50% of the specific bioluminescent activity compared to native luciferase. In preliminary tests, this hybrid protein was shown to be useful in bioluminescent immunoassays.

[The comparative characteristics of the immunomodulating properties of protein A from Staphylococcus aureus of different origins]

The immunomodulating properties of highly purified staphylococcal protein A and its analog obtained by gene engineering techniques have been compared with those of commercial preparations. The comparison has shown that the differences observed in this investigation may be explained by the presence of admixtures of staphylococcal nature in commercial preparations. The preparations of highly purified staphylococcal and recombinant protein A stimulate humoral immune response and the processes of phagocytosis and do not show mitogenic activity with respect to T cells. The conclusion on the identity of the immunomodulating activity of the preparations of natural and recombinant protein A has been made.

Interaction between heat shock protein DnaK and recombinant staphylococcal protein A

When a protein derived from the immunoglobulin G (IgG)-binding domains of staphylococcal protein A was expressed in Escherichia coli and recovered from cell extract by IgG affinity chromatography, the 69-kilodalton heat shock protein DnaK was found to be copurified. DnaK could be selectively eluted from the IgG column by ATP or by lowering the pH to 4.7. Protein A could subsequently be eluted by lowering the pH to 3.2. Thus, this procedure allows a one-step purification of both DnaK and protein A from cell extract. In vitro experiments with pure DnaK and protein A revealed that DnaK did not interfere with the IgG-binding properties of protein A but associated with its unfolded C-terminal in a salt-resistant manner. In addition, a specific interaction between DnaK and denaturated casein was found.

Isolations of protein A and protein G from the bacterial surface

Ten tested cultures each of Staphylococcus aureus (S. aureus) and of Streptococcus belonging to serological group G bound human IgG to a high extent. Protein A could be solubilized from strain Cowan I of S. aureus by lysozyme, mutanolysine, hydroxylammoniumchloride, hot acid extraction or lysostaphin and subsequently purified by affinity chromatography on human IgG-sepharose. The purified protein A preparation had molecular weights between 29,000 and 63,000 D and inhibited binding of 125I-labeled human IgG to S. aureus Cowan I. Protein G could be solubilized from strain 26540 of the G-streptococci with lysozyme or hot acid extraction and purified by affinity chromatography on human IgG-sepharose. The purified protein G revealed a molecular weight of 67,000 D and inhibited binding of human IgG to the G-streptococci.

Composite affinity sorbents and their cleaning in place

Making large-scale affinity sorbents that are reusable under acceptable hygienic conditions implies specific treatments for cleaning in place with known aqueous solutions of chemical agents. However, common agents such as sodium hydroxide are frequently considered too drastic for the stability of macromolecular biologically active immobilized ligands. According to a large series of trials, it was found that only a mixture of sodium hydroxide and ethanol was actually effective in sterilizing a sorbent in a single step. When hydroxide or an ethanol-acetic acid mixture were used alone, they were not totally efficient in the inactivation of sporulated Bacillus subtilis. Conversely, they were efficient when used sequentially. All these solutions were able to remove pyrogens from chromatographic sorbents. As the sterilizing solutions contained a certain amount of ethanol, the most suitable chromatographic affinity sorbents had to be based on an incompressible matrix. When washing an affinity silica sorbent that had proteins as ligands with solutions such as sodium hydroxide, ethanol-acetic acid or ethanol-sodium hydroxide, it was found that certain sorbents were able to tolerate the treatments without a noticeable decrease in their biochemical activity.