阅读说明：本技术 突变的免疫球蛋白结合多肽 (Mutated immunoglobulin-binding polypeptides ) 是由 G.罗德里戈 M.安德 G.鲍伦 T.布杰克曼 于 2014-07-08 设计创作，主要内容包括：本发明公开了碱性稳定性改进的多肽,所述多肽包含由SEQ ID NO 1或SEQ ID NO 2指定的葡萄球菌A蛋白(SpA)的B或C结构域或由SEQ ID NO 3指定的Z蛋白的突变体,其中至少9位的谷氨酰胺残基突变成天冬酰胺以外的氨基酸。本发明还公开了所述多肽的多聚体以及包含所述多聚体或多肽的分离基质。(The present invention discloses polypeptides with improved alkaline stability comprising a mutant of the B or C domain of staphylococcal protein A (SpA) designated by SEQ ID NO 1 or SEQ ID NO2 or of the protein Z designated by SEQ ID NO 3 wherein at least the glutamine residue at position 9 is mutated to an amino acid other than asparagine. Multimers of the polypeptides and separation matrices comprising the multimers or polypeptides are also disclosed.)

1. A polypeptide with improved alkaline stability comprising a mutant of the B or C domain of staphylococcal protein a (SpA) designated by SEQ ID NO 1 or SEQ ID NO2 or protein Z designated by SEQ ID NO 3 wherein at least the glutamine residue at position 9 is mutated to an amino acid other than asparagine.

2. The polypeptide of claim 1, wherein at least the glutamine residue at position 9 is mutated to an amino acid other than asparagine, proline or cysteine, such as to alanine.

3. The polypeptide of any one of the preceding claims, wherein the amino acid residue at position 23 is threonine or alanine.

4. The polypeptide of any one of the preceding claims, wherein the amino acid residue at position 3 is alanine and/or the amino acid residue at position 6 is aspartic acid.

5. The polypeptide of any one of the preceding claims, wherein at least one, such as both, of the amino acid residues in positions 3 and 6 is asparagine.

6. The polypeptide of any one of the preceding claims, wherein the serine residue at position 33 is mutated to an amino acid other than asparagine, glutamine, proline or cysteine, such as to lysine, or wherein the amino acid residue at position 33 is serine.

7. A polypeptide according to any one of the preceding claims wherein the glutamine residue at position 10 is mutated to an amino acid other than asparagine, glutamine, proline or cysteine, for example to alanine, or wherein the amino acid residue at position 10 is glutamine.

8. The polypeptide of any one of the preceding claims, wherein the glutamine residue at position 32 is mutated to an amino acid other than asparagine, glutamine, proline or cysteine, such as to alanine, or wherein the amino acid residue at position 32 is glutamine.

9. The polypeptide of any one of the preceding claims, wherein the glutamine residue at position 40 is mutated to an amino acid other than asparagine, glutamine, proline or cysteine, such as to alanine or valine, or wherein the amino acid residue at position 40 is glutamine.

10. The polypeptide of any one of the preceding claims, wherein the glutamine residue at position 55 is mutated to an amino acid other than asparagine, glutamine, proline or cysteine, such as to alanine, serine or glutamic acid, or wherein the amino acid residue at position 55 is glutamine.

11. The polypeptide of any one of the preceding claims, wherein the amino acid residue at position 26 is glutamine, or wherein the glutamine residue at position 26 is mutated to an amino acid other than asparagine, glutamine, proline, cysteine, alanine, or threonine.

12. The polypeptide of any one of the preceding claims, wherein the glutamic acid residue at position 47 is mutated to an amino acid other than asparagine, glutamine, proline or cysteine, or wherein the amino acid residue at position 47 is glutamic acid.

13. The polypeptide of claim 12, wherein the glutamic acid residue at position 47 is mutated to an alanine or a threonine.

14. The polypeptide of any one of the preceding claims, wherein the glutamic acid residue at position 15 is mutated to an amino acid other than asparagine, glutamine, proline or cysteine, or wherein the amino acid residue at position 15 is glutamic acid.

15. The polypeptide of claim 14, wherein the glutamic acid residue at position 15 is mutated to a lysine.

16. The polypeptide of any one of the preceding claims, wherein the asparagine residue at position 21 is mutated to an amino acid other than glutamine, proline or cysteine, such as to aspartic acid, or wherein the amino acid residue at position 21 is asparagine.

17. The polypeptide of any one of the preceding claims, wherein the aspartic acid residue at position 36 is mutated to an amino acid other than glutamine, proline or cysteine, or wherein the amino acid at position 36 is aspartic acid.

18. The polypeptide of claim 17, wherein the aspartic acid residue at position 36 is mutated to an alanine or a threonine.

19. The polypeptide of any one of the preceding claims, wherein the mutation is selected from the group consisting of: Q9A, Q9A, E15K, Q9A, E47T, Q9A, D36T, Q9A, D36A and Q9T, E47T.

20. The polypeptide of any one of the preceding claims, comprising or consisting essentially of a sequence selected from the group consisting of: SEQ ID NO 6, SEQ ID NO 7, SEQ ID NO 8, SEQ ID NO 9, SEQ ID NO 10, SEQ ID NO20, SEQ ID NO 25, SEQ ID NO 26 and SEQ ID NO 27.

21. A multimer comprising or essentially consisting of a plurality of polypeptide units as defined in any one of the preceding claims.

22. The multimer of claim 21, wherein the polypeptide units are linked by an element comprising up to 15 amino acids.

23. The multimer of claim 21 or 22, which is a dimer, trimer, tetramer, pentamer or hexamer.

24. The polypeptide or multimer of any of the preceding claims, further comprising one or more coupling elements selected from a cysteine residue, a plurality of lysine residues, and a plurality of histidine residues at the C-terminus or N-terminus.

25. A nucleic acid or vector encoding the polypeptide or multimer of any of the preceding claims.

26. An expression system comprising the nucleic acid or vector of claim 25.

27. A separation matrix wherein a plurality of polypeptides or multimers of any of claims 1-24 are coupled to a solid support.

28. The separation matrix of claim 27, wherein the polypeptide or multimer is coupled to the solid support via a thioether bond.

29. The separation matrix of claim 28 or 29, wherein the solid support is a polysaccharide.

30. A method of isolating immunoglobulins wherein a separation matrix according to any one of claims 27-29 is used.

31. The method of claim 30, comprising the steps of:

a) contacting a liquid sample comprising immunoglobulins with a separation matrix according to any one of claims 27-29,

b) the separation matrix is washed with a washing liquid,

c) eluting the immunoglobulin from the separation matrix with an eluent, and

d) the separation matrix is washed with a wash solution.

32. The method of claim 31, wherein the cleaning solution is alkaline, e.g., pH 13-14.

33. The method of claim 31 or 32, wherein the cleaning solution comprises 0.1-1.0M NaOH or KOH, such as 0.5-1.0M NaOH or KOH.

34. The method of any one of claims 31-33, wherein steps a) -d) are repeated at least 10 times, such as at least 50 times or 50-200 times.

Background

Immunoglobulins represent the most prevalent biopharmaceutical product in global manufacturing and development. The high commercial demand and the consequent value of this particular therapeutic market has led to an emphasis on pharmaceutical companies to maximize the productivity of their respective mAb production processes while controlling the associated costs.

Affinity chromatography is used in most cases as one of the key steps in the purification of these immunoglobulin molecules (e.g., monoclonal or polyclonal antibodies). One particularly interesting class of affinity reagents are proteins capable of specifically binding to the invariant part of an immunoglobulin molecule, the interaction being independent of the antigen binding specificity of the antibody. The reagents can be used extensively for affinity chromatography recovery of immunoglobulins from different samples such as, but not limited to, serum or plasma preparations or cell culture derived stocks. An example of such a protein is staphylococcal protein a, which contains domains capable of binding to the Fc and Fab portions of IgG immunoglobulins from different species.

Staphylococcal protein a (SpA) -based reagents are widely used in biotechnology fields, such as affinity chromatography for detection or quantification, and for capture and purification of antibodies, due to their high affinity and selectivity. Currently, SpA-based affinity media are probably the most widely used affinity media for the isolation of monoclonal antibodies and fragments thereof from different samples including industrial cell culture supernatants. Thus, various matrices comprising protein A-ligands are commercially available, e.g., in the form of native protein A (e.g., protein A SEPHAROSE;, GEHealthcare, Uppsala, Sweden), and also include recombinant protein A (e.g., rProtein A-SEPHAROSE;, GEHealthcare). More specifically, genetic manipulation is performed in commercially available recombinant protein A products in order to facilitate their attachment to a support.

These applications, like other affinity chromatography applications, require extensive attention to specifically remove contaminants. The contaminants may for example be non-eluting molecules adsorbed on the stationary phase or matrix in a chromatographic analysis procedure, such as unwanted biomolecules or microorganisms including for example proteins, carbohydrates, lipids, bacteria and viruses. Removal of the contaminants from the matrix is typically performed after the first elution of the desired product to regenerate the matrix prior to subsequent use. The removal typically involves a procedure known as clean-in-place (CIP) in which an agent capable of eluting the contaminants from the stationary phase is used. One such agent commonly used is an alkaline solution passed through the stationary phase. The most widely used cleaning and disinfecting agent at present is NaOH, the concentration of which can range from 0.1 up to e.g. 1M, depending on the degree and nature of the contamination. This strategy is associated with exposing the substrate to a pH value in excess of 13. For many affinity chromatography matrices containing proteinaceous affinity ligands, the alkaline environment is a very harsh condition and leads to reduced capacity due to the instability of the ligand to the high pH involved.

Much research has therefore focused on developing engineered protein ligands that exhibit improved ability to tolerate alkaline pH values. For example, Susanne et al (Susanne Gulich, Martin Linhult, Per-ke Nygren, Mathia Uhlen, Sophia Hober, Journal of Biotechnology 80 (2000), 169-. Mutants of ABD were made by tulich et al in which all 4 asparagine residues were replaced by leucine (1 residue), aspartic acid (2 residues) and lysine (1 residue). Furthermore, G ü lich et al report that their mutants show target protein binding properties similar to the native protein, and that affinity columns containing engineered ligands show higher binding capacities after repeated exposure to alkaline conditions compared to columns prepared using the parent non-engineered ligand. Thus, it is concluded herein that all 4 asparagine residues can be substituted without any significant effect on structure and function.

Recent studies have demonstrated changes that also allow protein a (SpA) to exert similar properties. U.S. patent application publication US 2005/0143566 discloses that when at least one asparagine residue is mutated to an amino acid other than glutamine or aspartic acid, the mutation confers increased chemical stability at pH values up to about 13-14 compared to the parent SpA, e.g., the B domain of SpA or protein Z, a synthetic construct derived from the B domain of SpA (US 5,143,844). The authors show that when these mutated proteins are used as affinity ligands, the separation medium can better withstand the washing procedure with alkaline agents as expected. Other mutations of protein a domains aimed at improving alkaline stability are also disclosed in WO 2008/039141, JP 2006304633A, EP 1992692a1, EP2202310a2, WO 2010/110288, WO 2012/086660 and WO 2012/083425. However, the mutations available today are still sensitive to alkaline pH and NaOH concentrations are usually limited to 0.1M during washing, which means that complete washing is difficult to achieve. Higher NaOH concentrations can improve cleaning, resulting in unacceptable loss of capacity.

There is therefore still a need in the art to obtain separation matrices containing protein ligands with further improved stability towards alkaline cleaning procedures.

Summary of The Invention

One aspect of the present invention is to provide polypeptides with improved alkaline stability. This is achieved using a polypeptide as defined in claim 1.

One advantage is improved alkaline stability relative to the parent polypeptide. Another advantage is the highly selective binding to immunoglobulins and other Fc-containing proteins.

A second aspect of the invention is to provide multimers comprising multiple polypeptides with improved alkaline stability. This is achieved using the multimers defined in the claims.

A third aspect of the invention is to provide a nucleic acid or vector encoding a polypeptide or multimer with improved alkaline stability. This is achieved using a nucleic acid or vector as defined in the claims.

A fourth aspect of the invention is to provide an expression system capable of expressing a polypeptide or multimer with improved alkaline stability. This is achieved using the expression system as defined in the claims.

A fifth aspect of the present invention is to provide a separation matrix capable of selectively binding immunoglobulins and other Fc-containing proteins and exhibiting improved alkaline stability. This is achieved using a separation matrix as defined in the claims.

A sixth aspect of the invention is to provide an efficient and economical method for isolating immunoglobulins or other Fc-containing proteins. This is achieved using the method defined in the claims.

Further suitable embodiments of the invention are described in the dependent claims.

Definition of

The terms "antibody" and "immunoglobulin" are used interchangeably herein, and are understood to also include fragments of antibodies, fusion proteins comprising antibodies or antibody fragments, and conjugates comprising antibodies or antibody fragments.

The terms "Fc binding polypeptide" and "Fc binding protein" refer to a polypeptide or protein, respectively, capable of binding to the crystallizable portion (Fc) of an antibody, including, for example, protein a and protein G or any fragment or fusion protein thereof that retains the binding properties described.

Brief Description of Drawings

Figure 1 shows the results of the base stability of mutant or non-mutant monomeric Zvar (seq id NO 4) polypeptide variants coupled to SPR biosensor chips from example 1.

Fig. 2 shows an enlargement of fig. 1 of the polypeptide variant with the highest alkali stability.

Detailed description of the embodiments

In one aspect, the invention discloses polypeptides comprising or essentially consisting of one or more mutants of the B or C domain of staphylococcal protein a (SpA) designated by SEQ ID NO 1 or SEQ ID NO2 or the Z protein designated by SEQ ID NO 3 or SEQ ID NO 4 wherein at least the glutamine residue at position 9 is mutated to an amino acid other than asparagine. Seq id NO 4 represents a variant of the Z protein with mutations N3A, N6D, N23T, herein designated Zvar. Mutations in Q9 in these domains confer improved base stability compared to the parent domain/polypeptide without impairing immunoglobulin binding properties. Thus, the polypeptide may also be described as an Fc-or immunoglobulin-binding polypeptide.

In some embodiments, the glutamine residue at least position 9 of SEQ ID NOs 1-4 is mutated to an amino acid other than asparagine, proline or cysteine, for example to alanine. This has the following advantages: no deamidation sensitive asparagine was introduced, the chain conformation was not disturbed by the introduction of proline and no sites for disulfide bonds were introduced. The Q9 mutation (e.g., Q9A mutation) may be the only mutation or the polypeptide may further comprise other mutations, for example in at least one of positions N3, N6, Q10, E15, H18, N21, N23, N28, G/a29, D36, Q/V40, a/K42, N/E43, L/I44, E47, Q55 and P57. In one or more of these positions, the original amino acid residue may be substituted with, for example, an amino acid other than asparagine, proline or cysteine. The original amino acid residue may be substituted with, for example, alanine, valine, threonine, serine, lysine, or aspartic acid.

In certain embodiments, the amino acid residue at position 23 is threonine or alanine.

In some embodiments, the amino acid residue at position 3 is alanine and/or the amino acid residue at position 6 is aspartic acid. In certain embodiments, at least one of the amino acid residues at positions 3 and 6 is asparagine.

In certain embodiments, the serine residue at position 33 is mutated to an amino acid other than asparagine, glutamine, proline or cysteine, for example to lysine. In an alternative embodiment, the amino acid residue at position 33 is serine.

In some embodiments, the glutamine residue at position 10 is mutated to an amino acid other than asparagine, glutamine, proline or cysteine, for example to alanine. In an alternative embodiment, the amino acid residue at position 10 is glutamine.

In certain embodiments, the glutamine residue at position 32 is mutated to an amino acid other than asparagine, glutamine, proline or cysteine, for example to alanine. In an alternative embodiment, the amino acid residue at position 32 is glutamine.

In some embodiments, the glutamine residue at position 40 is mutated to an amino acid other than asparagine, glutamine, proline or cysteine, for example to alanine or valine. In an alternative embodiment, the amino acid residue at position 40 is glutamine.

In certain embodiments, the glutamine residue at position 55 is mutated to an amino acid other than asparagine, glutamine, proline or cysteine, for example to alanine, serine or glutamic acid. In an alternative embodiment, the amino acid residue at position 55 is glutamine.

In some embodiments, the amino acid residue at position 26 is glutamine. It appears that the alkaline stability of the polypeptide with the Q9 mutation is better when Q26 is not mutated to threonine or alanine. In alternative embodiments, the amino acid residue at position 26 may be mutated to an amino acid other than asparagine, glutamine, proline, cysteine, threonine, or alanine.

In certain embodiments, the glutamic acid residue at position 15 is mutated to an amino acid other than asparagine, glutamine, proline, or cysteine. In a specific embodiment, the glutamic acid residue at position 15 is mutated to a lysine. This accidental mutation further improves the alkaline stability of the polypeptide having the Q9 mutation. In an alternative embodiment, the amino acid residue at position 15 is glutamic acid.

In some embodiments, the glutamic acid residue at position 47 is mutated to an amino acid other than asparagine, glutamine, proline, or cysteine, for example to alanine or threonine. In an alternative embodiment, the amino acid residue at position 47 is glutamic acid.

In some embodiments, the asparagine residue at position 21 is mutated to an amino acid other than glutamine, proline, or cysteine, for example to aspartic acid. In an alternative embodiment, the amino acid residue at position 21 is asparagine.

In certain embodiments, the aspartic acid residue at position 36 is mutated to an amino acid other than glutamine, proline, or cysteine. In a specific embodiment, the aspartic acid residue at position 36 is mutated to an alanine or threonine. In an alternative embodiment, the amino acid at position 36 is aspartic acid.

In some embodiments, the mutation is selected from Q9A, Q9A, E15K, Q9A, E47T, Q9A, D36T, Q9A, D36A and Q9T, E47T. These mutations provide particularly high alkaline stability.

In certain embodiments, the polypeptide comprises a sequence selected from the group consisting of: SEQ ID NO 6, SEQ ID NO 7, SEQ ID NO 8, SEQ ID NO 9, SEQ ID NO 10, SEQ ID NO20, SEQ ID NO 21, SEQ ID NO 22 and SEQ ID NO 23, and further SEQ ID NO 25, SEQ ID NO 26 and SEQ ID NO 27. It may be defined, for example, by a sequence selected from SEQ ID NOs 6-10 and 20-23, but may also comprise other amino acid residues C-terminal and/or N-terminal.

In a second aspect, the invention discloses or consists essentially of a multimer comprising a plurality of polypeptide units as defined in any of the embodiments disclosed above. The multimer may be, for example, a dimer, trimer, tetramer, pentamer, or hexamer. It can be a homomultimer in which all units in the multimer are the same, or it can be a heteromultimer in which at least one unit is different from the other units. Advantageously, all units in the multimer are base-stable, e.g., by comprising the mutations disclosed above. The polypeptides may each be directly linked by a peptide bond between the C-and N-termini of the polypeptide. Alternatively, two or more units in a multimer may be linked by an element comprising an oligomeric or polymeric species, e.g., an element comprising up to 15 or 30 amino acids, e.g., 1-5, 1-10, or 5-10 amino acids. The nature of the linkage may preferably not destabilize the spatial conformation of the protein unit. This can be achieved, for example, by avoiding the presence of proline in the linkage. Furthermore, the linkage should preferably also be sufficiently stable in alkaline environments so that the properties of the mutated protein unit are not impaired. For this reason, it is advantageous if the linkage does not contain asparagine. It may also be advantageous if the linkage does not contain glutamine. The multimer may further comprise a plurality of amino acid residues at the N-terminus, which result from the cloning process or constitute residues from the cleaved signal transduction sequence. The number of other amino acid residues may be, for example, 15 or less, such as 10 or less, or 5 or less. As a specific example, the multimer may comprise an AQ sequence at the N-terminus.

In some embodiments, the polypeptides and/or multimers disclosed above further comprise one or more coupling elements at the C-terminus or N-terminus selected from the group consisting of a cysteine residue, a plurality of lysine residues, and a plurality of histidine residues. The coupling element may be, for example, a single cysteine at the C-terminus. The coupling element may be directly linked to the C-terminus or N-terminus, or it or they may be linked by a linker comprising up to 15 amino acids, for example 1-5, 1-10 or 5-10 amino acids. Such a sequence stretch (strech) is also preferably sufficiently stable in an alkaline environment so that the properties of the mutein are not impaired. For this purpose, it is advantageous if the sequence segments do not contain asparagine. It may also be advantageous if the sequence stretch does not contain glutamine. An advantage of having a C-terminal cysteine is that end-point coupling of the protein can be achieved by reaction of the cysteine thiol group with electrophilic groups on the support. This provides excellent mobility of the coupled protein important for binding capacity.

In a third aspect, the invention discloses a nucleic acid encoding a polypeptide or multimer of any of the embodiments disclosed above. Thus, the invention includes all forms of the nucleic acid sequences of the invention, such as RNA and DNA encoding polypeptides or multimers. The invention includes vectors, such as plasmids, which in addition to the coding sequence, also contain the signal sequences required for expression of the polypeptides or multimers of the invention. In one embodiment, the vector comprises nucleic acids encoding the multimers of the invention, wherein the individual nucleic acids encoding each unit may have homologous or heterologous DNA sequences.

In a fourth aspect, the present invention discloses an expression system comprising the nucleic acid or vector disclosed above. The expression system can be, for example, a gram-positive or gram-negative prokaryotic host cell system, such as E.coli (E.coli) modified to express a polypeptide or multimer of the inventionE. coli) Or Bacillus (Bacillus sp.). In an alternative embodiment, the expression system is a eukaryotic host cell system, such as a yeast, e.g., Pichia pastoris (R.pastoris) ((R))Pichea pastoris) Or Saccharomyces cerevisiae (Saccharomy cescerevisiae)。

In a fifth aspect, the present invention discloses a separation matrix wherein a plurality of polypeptides or multimers of any of the embodiments disclosed above are coupled to a solid support. The matrix can be used for the isolation of immunoglobulins or other Fc-containing proteins and, due to the improved alkaline stability of the polypeptides/multimers, the matrix can withstand highly alkaline conditions upon washing, which is necessary for long-term reuse in bioprocess isolation environments.

As the skilled person will appreciate, the expressed polypeptide or multimer should be purified to an appropriate extent before being immobilized on a support. Such purification methods are well known in the art, and the immobilization of protein-based ligands to a support is readily performed using standard methods. Suitable methods and supports are discussed in more detail below.

The solid support of the matrix of the invention may be of any suitable well-known kind. Conventional affinity separation matrices are often of an organic nature and are based on polymers that expose a hydrophilic surface to the aqueous medium used, i.e., hydroxyl (-OH), carboxyl (-COOH), formylamino (-CONH)₂Possibly in N-substituted form), amino (-NH)₂Possibly in substituted form), oligoethyleneoxy or polyethyleneoxy groups are exposed to the exterior thereof, if present, and also to the interior surface. The solid support may suitably be porous. Porosity can be expressed as the Kav or Kd value (fraction of pore volume achievable with a particular size of probe molecule), as measured, for example, by reverse size exclusion chromatography, according to the methods described in the Gel Filtration Principles and methods (Gel Filtration Principles and methods), Pharmacia LKB Biotechnology 1991, pages 6-13. Both Kd and Kav values are always within the range of 0-1 by definition. The Kav value may advantageously be in the range of 0.6-0.95, e.g.0.7-0.90 or 0.6-0.8, as measured with dextran having a Mw of 110 kDa as probe molecule. The advantage is that the support has a large part of the pores capable of holding both the polypeptide/multimer of the invention and the immunoglobulin bound to the polypeptide/multimer and providing mass transport (mass transport) of the immunoglobulin to and from the binding site.

The polypeptide or multimer may be attached to the support by conventional coupling techniques using, for example, thiol, amino and/or carboxyl groups present on the ligand. Diepoxides, epichlorohydrin, CNBr, N-hydroxysuccinimide (NHS), and the like are well known coupling reagents. Between the support and the polypeptide/multimer, molecules called spacers can be introduced, which improve the availability of the polypeptide/multimer and facilitate the chemical coupling of the polypeptide/multimer to the support. Alternatively, the polypeptide/multimer may be attached to the support by non-covalent bonding (e.g., physisorption or biospecific adsorption).

In some embodiments, the matrix comprises 5-20, such as 5-15 mg/ml, 5-11 mg/ml or 6-11 mg/ml of said polypeptide or multimer coupled to said support. The amount of polypeptide/multimer coupled can be controlled by the concentration of the polypeptide/multimer used during the coupling process, the coupling conditions used, and/or the pore structure of the support used. In general, the absolute binding capacity of the matrix increases with the amount of polypeptide/multimer coupled, at least up to the point where the pore becomes significantly narrowed by the coupled polypeptide/multimer. The relative binding capacity per mg of conjugated polypeptide/multimer will decrease at high conjugation levels, yielding the cost benefit optimum in the range specified above.

In certain embodiments, the polypeptide or multimer is coupled to the support via a thioether bond. Methods for performing such couplings are well known in the art and are readily performed by those skilled in the art using standard techniques and equipment. Thioether linkages are flexible and stable and are generally suitable for use in affinity chromatography. Especially when the thioether bond is through a terminal or near-terminal cysteine residue on the polypeptide or multimer, the mobility of the coupled polypeptide/multimer is increased, which provides improved binding capacity and binding kinetics. In some embodiments, the polypeptide/multimer is coupled via a C-terminal cysteine provided on the above-described protein. This allows efficient coupling of the cysteine thiol group with electrophilic groups (e.g. epoxy groups, halohydrin groups etc.) on the support, resulting in thioether bridge coupling.

In certain embodiments, the support comprises a polyhydroxy polymer, such as a polysaccharide. Examples of polysaccharides include, for example, dextran, starch, cellulose, pullulan (pululan), agar, agarose, and the like. Polysaccharides are inherently hydrophilic, have a low degree of non-specific interactions, they provide a high content of reactive (activatable) hydroxyl groups, and they are generally stable to alkaline cleaning solutions used in bioprocessing.

In some embodiments, the support comprises agar or agarose. The supports used in the present invention can be readily prepared according to standard methods, such as reverse suspension gelation (S Hjerten: Biochim Biophys Acta 79(2), 393-398 (1964)). Alternatively, the base matrix is a commercially available product, such as SEPHAROSE ™ FF (GE healthcare). In one embodiment which is particularly advantageous for large scale separations, the use of the method described in US6602990 or US7396467 (which are herein incorporated by reference in their entirety) makes the support suitable for increasing its rigidity, and thus makes the matrix more suitable for high flow rates.

In certain embodiments, a support (e.g., a polysaccharide or agarose support) is crosslinked, for example, with hydroxyalkyl ether crosslinks (crosslinks). The crosslinking agent which produces the crosslinking may be, for example, an epihalohydrin such as epichlorohydrin, a diepoxide such as butanediol diglycidyl ether, an allylating agent such as allyl halide or allyl glycidyl ether. Crosslinking is advantageous for the rigidity of the support and improves chemical stability. The hydroxyalkyl ether cross-links are stable to alkali and do not cause significant non-specific adsorption.

Alternatively, the solid support is based on synthetic polymers such as polyvinyl alcohol, polyhydroxyalkyl acrylates, polyhydroxyalkyl methacrylates, polyacrylamides, polymethacrylamides, and the like. In the case of hydrophobic polymers, such as matrices based on divinyl and monovinyl-substituted benzenes, the surface of the matrix is often hydrophilised to expose the hydrophilic groups defined above to the surrounding aqueous liquid. Such multimers are readily produced according to standard procedures, see, for example, "Styrene-based polymer supports developed by suspension polymerization" (R apparatus: Chimica e L' Industria 70(9), 70-75 (1988)). Alternatively, commercially available products, such as SOURCE ™ (GE Healthcare), are used. In another alternative method, the solid support of the present invention comprises a support of inorganic nature (e.g., silica, zirconia, etc.).

In yet another embodiment, the solid support is in another form, such as a surface, a chip, a capillary, or a filter (e.g., a membrane or depth filter matrix).

As to the shape of the substrate of the present invention, in one embodiment, the substrate is in the form of a porous monolith. In an alternative embodiment, the matrix is in the form of beads or particles which may be porous or non-porous. The matrix in bead form or in particle form can be used as a packed bed or in suspended form. Suspended forms include those known as expanded beds and pure suspensions, in which the particles or beads are free to move. In the case of monoliths, packed beds and expanded beds, the separation procedure generally follows conventional chromatography with a concentration gradient. In the case of pure suspension, a batch mode will be used.

In a sixth aspect, the present invention discloses a method for isolating immunoglobulins wherein a separation matrix as disclosed above is used.

In certain embodiments, the method comprises the steps of:

a) contacting a liquid sample comprising immunoglobulins with a separation matrix as disclosed above,

b) the separation matrix is washed with a washing liquid,

c) eluting the immunoglobulin from the separation matrix with an eluent, and

d) the separation matrix is washed with a wash solution.

The method may further comprise a step prior to step a) of providing the affinity separation matrix of any one of the embodiments described above and providing a solution comprising the immunoglobulin and at least one further substance as a liquid sample; and a step after step c) of recovering the eluate and optionally subjecting the eluate to a further separation step, for example by anion or cation exchange chromatography, multimodal chromatography and/or hydrophobic interaction chromatography. Suitable compositions of liquid samples, wash solutions and eluents, and general conditions under which the separation is carried out, are well known in the field of affinity chromatography, in particular protein A chromatography. The liquid sample comprising the Fc-containing protein and at least one other substance may comprise a Host Cell Protein (HCP), such as a CHO cell or e. The content of CHO cells and E.coli proteins may conveniently be determined by immunoassays for these proteins, e.g.CHOHCP from Cygnus Technologies or E.coli HCP ELISA kits. The host cell proteins or CHO cell/e.coli proteins may be desorbed during step b).

Elution may be performed using any suitable solution for elution from the protein a medium. This may be, for example, a solution or buffer at a pH of 5 or less, for example at a pH of 2.5-5 or 3-5. In some cases it may also be a solution or buffer at a pH of 11 or higher, for example at a pH of 11 to 14 or at a pH of 11 to 13. In some embodiments, the elution buffer or elution buffer gradient comprises at least one mono-, di-or tri-functional carboxylic acid or salt of said carboxylic acid. In certain embodiments, the elution buffer or elution buffer gradient comprises at least one anionic species selected from the group consisting of: acetate, citrate, aminoacetate, succinate, phosphate and formate.

In some embodiments, the cleaning solution is alkaline, e.g., has a pH of 13-14. The solution provides effective cleaning of the substrate, particularly the upper end of the interior.

In certain embodiments, the cleaning solution comprises 0.1 to 2.0M NaOH or KOH, such as 0.5 to 2.0 or 0.5 to 1.0M NaOH or KOH.

In some embodiments, steps a) -d) are repeated at least 10 times, such as at least 50 times or 50-200 times.