Patent Publication Number: US-2018036445-A1

Title: Sanitization Method for Affinity Chromatography Matrices

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to the field of affinity chromatography, and more specifically to a method of sanitizing affinity chromatography matrices. 
     BACKGROUND OF THE INVENTION 
     Immunoglobulins and immunoglobulin fragments represent the most prevalent biopharmaceutical products in either manufacture or development worldwide. The high commercial demand for and hence value of this particular therapeutic market has led to the emphasis being placed on pharmaceutical companies to maximize the productivity of their respective manufacturing processes whilst controlling the associated costs and maintaining product quality. 
     Affinity chromatography, typically on matrices comprising staphylococcal protein A or variants thereof, is normally used as one of the key steps in the purification of intact immunoglobulin molecules. The highly selective binding of protein A to the Fc chain of immunoglobulins provides for a generic step with very high clearance of impurities and contaminants. Similarly, matrices comprising  Peptostreptococcus  Protein L or variants thereof are useful for purifying e.g. Fabs or other fragments of antibodies like scFv, BiTEs, domain antibodies etc., which contain a kappa light chain. 
     Any bioprocess chromatography application requires comprehensive attention to definite removal of impurities and contaminants. Such impurities/contaminants can for example be non-eluted molecules adsorbed to the stationary phase or matrix in a chromatographic procedure, such as non-desired biomolecules or microorganisms, including for example proteins, carbohydrates, lipids, bacteria and viruses. The removal of such impurities/contaminants from the matrix is usually performed after a first elution of the desired product in order to regenerate the matrix before subsequent use. Such removal usually involves a procedure known as cleaning-in-place (CIP) and typically involves alkaline solutions. 
     Additionally, there is a need for regular sanitization of the matrix to inactivate any microorganisms or spores present in the column. This is typically carried out as a sanitization-in-place (SIP) procedure, either involving sodium hydroxide or acidic solutions, e.g. phosphoric/acetic acid mixtures containing bacteriostats such as benzyl alcohol. With matrices having proteinaceous ligands, it is however difficult to find conditions that effectively kill microorganisms and spores without damaging the ligands. 
     There is thus still a need in this field for efficient SIP methods that do not damage the ligands. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention is to provide a sanitization and/or cleaning method for affinity chromatography media with proteinaceous ligands, which method does not substantially impair the function of the ligands. This is achieved with a method as defined in claim  1 . 
     One advantage is that a high degree of bacteria and spore inactivation can be achieved. A further advantage is that product-related impurities such as tightly bound non-eluted antibodies or process-related impurities such as host cell proteins can be removed. 
     A second aspect of the invention is to provide a use of an oxidant solution for sanitization and/or cleaning of affinity chromatography media. This is achieved with a use as defined in the claims. 
     Further suitable embodiments of the invention are described in the dependent claims. 
     Definitions 
     The terms “antibody” and “immunoglobulin” are used interchangeably herein, and are understood to include also fragments of antibodies, fusion proteins comprising antibodies or antibody fragments and conjugates comprising antibodies or antibody fragments. 
     The terms a “kappa light chain-binding polypeptide” and “kappa light chain-binding protein” herein mean a polypeptide or protein respectively, capable of binding to the kappa light chain of an antibody and includes e.g. Protein L, and any variant, fragment or fusion protein thereof that has maintained said binding property. 
     The term “kappa light chain-containing protein” is used as a synonym of “immunoglobulin kappa light chain-containing protein” and herein means a protein comprising a kappa light chain derived from an antibody and includes any intact antibodies, antibody fragments, fusion proteins, conjugates or recombinant proteins containing a kappa light chain. 
     The term “oxidation-tolerant” herein means a material which retains at least 80%, such as at least 90%, of its functionality after 24 h incubation at 22+/−2° C. with an aqueous 0.1 M peracetic acid solution. The functionality can e.g. be the binding capacity for a target species such as an immunoglobulin, IgG, a monoclonal antibody or an antibody fragment. 
     The term “affinity chromatography matrix” herein means a separation matrix having ligands capable of binding a target species with an equilibrium dissociation constant K D  less than about 10 −5  M, such as between 10 −14  and 10 −6  M. K D  is here defined as K D =[L]*[T]/[LT], where [L] is the concentration of free ligand, [T] is the concentration of free target species and [LT] is the concentration of ligand-target species complex. Most such ligands are proteins and can e.g. include bacterial immunoglobulin-binding proteins and their variants, antibodies, streptavidin, lectins etc. The target species can e.g. be a protein such as an immunoglobulin. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
         FIG. 1  shows chromatograms (UV detection) of recombinant Protein L before (a) and after (b) 1 h incubation in 0.1 M peracetic acid. x-axis time, y-axis UV absorbance (280 nm). 
         FIG. 2  shows chromatograms (UV detection) of single-chain camelid antibody against kappa chains (KappaSelect ligand) before (a) and after (b) 1 h incubation in 0.1 M peracetic acid. x-axis time, y-axis UV absorbance (280 nm). 
         FIG. 3  shows chromatograms (MS detection) of recombinant Protein L before (a) and after (b) 1 h incubation in 0.1 M peracetic acid. x-axis time, y-axis MS response. 
         FIG. 4  shows chromatograms (MS detection) of single-chain camelid antibody against kappa chains (KappaSelect ligand) before (a) and after (b) 1 h incubation in 0.1 M peracetic acid. x-axis time, y-axis MS response. 
         FIG. 5  shows pressure-flow curves for a rigid agarose base matrix, a) untreated matrix and b) a sample of the same matrix after incubation with 30 mM peracetic acid solution. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     In one aspect the present invention discloses a method for cleaning or sanitization of an affinity chromatography matrix. This method comprises the steps of: 
     a) providing an affinity chromatography matrix having oxidation-tolerant proteinaceous ligands coupled to a support. The proteinaceous ligands can suitably comprise or consist essentially of one or more immunoglobulin-binding domains derived from a bacterial protein. Bacterial immunoglobulin-binding proteins are well known in the art, (see e.g. E V Sidorin, T F Soloveva: Biochemistry Moscow 76(3), 295-308, 2011) and can in particular be exemplified by the immunoglobulin-binding proteins of Gram-positive bacteria, such as  Staphylococcus  Protein A (SpA, SEQ ID NO:17),  Peptostreptococcus  Protein L (SEQ ID NO:18) and  Streptococcus  Protein G (SEQ ID NO:19). These proteins have a common single-chain structure characterized by the presence in the molecule of three different regions: the N-terminal region containing a signaling peptide responsible for the translocation of the protein across the cytoplasmic membrane and then detached; the functional region comprising several domains that determine the functional activity of the protein; and the C-terminal region denoted as a sorting signal responsible for anchoring of the protein in the cell wall. The functional regions are constructed on a single principle: they contain polypeptide repeats of one or several types. Highly homologous repeats of the same type can be organized as tandems. The number of repeats can vary and determine the protein heterogeneity in molecular weight and functional activity. Recombinant variants of these proteins to be used as affinity ligands often lack the C-terminal region, as it is not needed for this purpose. They can also have different N-terminal regions and selected point mutations in the domains to e.g. improve the alkali stability of the proteins. 
     b) contacting the matrix with a sanitization solution comprising at least one oxidant as defined by formula I, 
       R—O—O—H  (I)
 
     wherein R is hydrogen or an acyl group R′—C(O)—, with R′ being a hydrogen or a methyl, ethyl or propyl group. Such oxidants include hydrogen peroxide H 2 O 2 , performic acid HCO 3 H, peracetic acid CH 3 CO 3 H, perpropionic acid CH 3 CH 2 CO 3 H and perbutyric acid CH 3 CH 2 CH 2 CO 3 H. The pH of the sanitization solution can e.g. be 2-12, such as 2-4 or 2-3, which is beneficial for the sanitization effect and the concentration of the at least one oxidant can e.g. be 0.01-1.0 mol/l, such as 0.02-0.2 mol/l, 0.05-0.5 mol/l or 0.03-0.1 mol/l. The solution may contain a single oxidant or a mixture of oxidants according to formula I, e.g. a mixture of hydrogen peroxide with performic or peracetic acid. In the case of mixtures, the total concentration of oxidants defined by formula I can suitably be 0.01-1 mol/l, such as 0.02-0.2 mol/l, 0.05-0.5 mol/l or 0.03-0.1 mol/l. The solution may further comprise a carboxylic acid such as formic acid, acetic acid, propionic acid or butyric acid. If the solution comprises a peracid, the carboxylic acid can suitably be the corresponding carboxylic acid, i.e. a carboxylic acid R′—C(O)—OH having the same acyl group R′—C(O)— as the peracid R′C(O)OOH. The contacting may involve, or consist essentially of, incubating the matrix with the sanitization solution for e.g. 1 min-24 h, such as 5 min-24 h or 10 min-24 h. The incubation can suitably take place in a column packed with the matrix, or alternatively in a separate vessel with matrix from an unpacked column, and the incubation temperature can e.g. be room temperature or 15-30° C. The column can be a re-usable stainless steel column but it can also be a single use column, e.g. a column prepared from thermoplastic and elastomeric components. In the latter case, the thermoplastic and elastomeric materials can suitably be selected such that they are not significantly degraded by the oxidant solutions. Temperatures outside of the 15-30° C. range can also be possible, particularly if some experimental work is carried out to find suitable concentrations and incubation times. As a first approximation it can be assumed that the usual Arrhenius temperature dependence can be applied, such that for a temperature increase of 10° C., the incubation time may be decreased 2-3 times. The relationship between suitable concentrations and incubation times at constant temperature can be assumed to be approximately linear. 
     In certain embodiments, the immunoglobulin-binding domain(s) can be derived from a bacterial protein selected from the group consisting of  Staphylococcus  Protein A,  Peptostreptococcus  Protein L and  Streptococcus  Protein G, such as from the group consisting of  Staphylococcus  Protein A and  Peptostreptococcus  Protein L. The immunoglobulin-binding domain(s) can e.g. have at least 80%, such as at least 90 or 95%, homology with Domain E, D, A, B or C of  Staphylococcus  Protein A, with Protein Z (a variant of Domain B of Protein A) or with Domain 1, 2, 3, 4 or 5 of  Peptostreptococcus  Protein L. In this context, the immunoglobulin-containing domain(s) can be defined by, or have at least 80%, such as at least 90 or 95% sequence homology with, an amino acid sequence selected from the group consisting of SEQ ID NO: 1-11. 
     
       
         
           
               
            
               
                 Domain E of Protein A 
               
               
                 SEQ ID NO: 1 
               
               
                 AQQ NAFYQVLNMP NLNADQRNGF IQSLKDDPSQ SANVLGEAQK 
               
               
                 LNDSQAPK 
               
               
                   
               
               
                 Domain D of Protein A 
               
               
                 SEQ ID NO: 2 
               
               
                 ADA QQNKFNKDQQ SAFYEILNMP NLNEEQRNGF IQSLKDDPSQ 
               
               
                 STNVLGEAKK LNESQAPK 
               
               
                   
               
               
                 Domain A of Protein A 
               
               
                 SEQ ID NO: 3 
               
               
                 A DNNFNKEQQ NAFYEILNMP NLNEEQRNGF IQSLKDDPSQ 
               
               
                 SANLLAEAKK LNESQAPK 
               
               
                   
               
               
                 Domain B of Protein A 
               
               
                 SEQ ID NO: 4 
               
               
                 ADNKFNKEQQ NAFYEILHLP NLNEEQRNGF IQSLKDDPSQ 
               
               
                 SANLLAEAKK LNDAQAPK 
               
               
                   
               
               
                 Domain C of Protein A 
               
               
                 SEQ ID NO: 5 
               
               
                 ADNKFNKEQQ NAFYEILHLP NLTEEQRNGF IQSLKDDPSV 
               
               
                 SKEILAEAKK LNDAQAPK 
               
               
                   
               
               
                 Protein Z 
               
               
                 SEQ ID NO: 6 
               
               
                 VDNKFNKEQQ NAFYEILHLP NLNEEQRNAF IQSLKDDPSQ 
               
               
                 SANLLAEAKK LNDAQAPK 
               
               
                   
               
               
                 Domain 1 of Protein L 
               
               
                 SEQ ID NO: 7 
               
               
                 SEEEVTIKAN LIFANGSTQT AEFKGTFEKA TSEAYAYADT 
               
               
                 LKKDNGEYTV DVADKGYTLN IKFAGKEKTPEE 
               
               
                   
               
               
                 Domain 2 of Protein L 
               
               
                 SEQ ID NO: 8 
               
               
                 PKEEVTIKAN LIYADGKTQT AEFKGTFEEA TAEAYRYADA 
               
               
                 LKKDNGEYTV DVADKGYTLN IKFAGKEKTPEE 
               
               
                   
               
               
                 Domain 3 of Protein L 
               
               
                 SEQ ID NO: 9 
               
               
                 PKEEVTIKAN LIYADGKTQT AEFKGTFEEA TAEAYRYADL 
               
               
                 LAKENGKYTV DVADKGYTLN IKFAGKEKTPEE 
               
               
                   
               
               
                 Domain 4 of Protein L 
               
               
                 SEQ ID NO: 10 
               
               
                 PKEEVTIKAN LIYADGKTQT AEFKGTFAEA TAEAYRYADL 
               
               
                 LAKENGKYTA DLEDGGYTIN IRFAGKKVDEKPEE 
               
               
                   
               
               
                 Domain 5 of Protein L 
               
               
                 SEQ ID NO: 11 
               
               
                 EKEQVTIKEN IYFEDGTVQT ATFKGTFAEA TAEAYRYADL 
               
               
                 LSKEHGKYTA DLEDGGYTIN IRFAG 
               
            
           
         
       
     
     In some embodiments, the immunoglobulin-binding domain(s) can be derived from known variants of the native domains of SEQ ID NO: 1-11, such as the domains described in one or more of WO03080655A1, WO2008039141A1, EP1992692A1, EP2157099A1, EP2202310A2, EP2412809A1, EP2557157A1, EP2157099 and WO2013109302A2, all of which are hereby incorporated by reference in their entireties. The immunoglobulin-binding domain(s) can e.g. be defined by, or have at least 90%, such as at least 95 or 98% sequence homology with, an amino acid sequence selected from the group consisting of SEQ ID NO: 12-16. 
     
       
         
           
               
            
               
                 Protein Z variant (WO03080655A1) 
               
               
                 SEQ ID NO: 12 
               
               
                 VDNKFNKEQQ NAFYEILHLP NL T EEQRNAF IQSLKDDPSQ 
               
               
                 SANLLAEAKK LNDAQAPK 
               
               
                   
               
               
                 Protein Z variant (WO03080655A1) 
               
               
                 SEQ ID NO: 13 
               
               
                 VD A KF D KEQQ NAFYEILHLP NL T EEQRNAF IQSLKDDPSQ 
               
               
                 SANLLAEAKK LNDAQAPK 
               
               
                   
               
               
                 Domain C variant (WO2008039141A1) 
               
               
                 SEQ ID NO: 14 
               
               
                 ADNKFNKEQQ NAFYEILHLP NLTEEQRN A F IQSLKDDPSV 
               
               
                 SKEILAEAKK LNDAQAPK 
               
               
                   
               
               
                 Domain C variant (EP2557157A1) 
               
               
                 SEQ ID NO: 15 
               
               
                 ADNKFNKEQQ NAFYEILHLP NLTEEQRN A F IQ E LKDDPSV 
               
               
                 SKEILAEAKK LNDAQAPK 
               
               
                   
               
               
                 Domain C variant (WO3013109302A2) 
               
               
                 SEQ ID NO: 16 
               
               
                 FNKEQQ NAFYEILHLP NLTEEQRNGF IQSLKDDPSV SKEILAEAKK 
               
               
                 LNDAQAPK 
               
               
                   
               
               
                 Protein A 
               
               
                 SEQ ID NO: 17 
               
               
                 AQQ NAFYQVLNMP NLNADQRNGF IQSLKDDPSQ SANVLGEAQK 
               
               
                   
               
               
                 LNDSQAPK ADA QQNKFNKDQQ SAFYEILNMP NLNEEQRNGF 
               
               
                   
               
               
                 IQSLKDDPSQ STNVLGEAKK LNESQAPK A DNNFNKEQQ 
               
               
                   
               
               
                 NAFYEILNMP NLNEEQRNGF IQSLKDDPSQ SANLLAEAKK 
               
               
                   
               
               
                 LNESQAPK ADNKFNKEQQ NAFYEILHLP NLNEEQRNGF 
               
               
                   
               
               
                 IQSLKDDPSQ SANLLAEAKK LNDAQAPK ADNKFNKEQQ 
               
               
                   
               
               
                 NAFYEILHLP NLTEEQRNGF IQSLKDDPSV SKEILAEAKK 
               
               
                   
               
               
                 LNDAQAPK 
               
               
                   
               
               
                 Protein L (US5965390) 
               
               
                 SEQ ID NO: 18 
               
               
                 AVENKEETPETPETDSEEEVTIKANLIFANGSTQTAEFKGTFEKATSEA 
               
               
                   
               
               
                 YAYADTLKKDNGEYTVDVADKGYTLNIKFAGKEKTPEEPKEEVTIKANL 
               
               
                   
               
               
                 IYADGKTQTAEFKGTFEEATAEAYRYADALKKDNGEYTVDVADKGYTLN 
               
               
                   
               
               
                 IKFAGKEKTPEEPKEEVTIKANLIYADGKTQTAEFKGTFEEATAEAYRY 
               
               
                   
               
               
                 ADLLAKENGKYTVDVADKGYTLNIKFAGKEKTPEEPKEEVTIKANLIYA 
               
               
                   
               
               
                 DGKTQTAEFKGTFAEATAEAYRYADLLAKENGKYTADLEDGGYTINIRF 
               
               
                   
               
               
                 AGKKVDEKPEE 
               
               
                   
               
               
                 Protein G 
               
               
                 SEQ ID NO: 19 
               
               
                 AQHDEAVDAN SRGSVDASEL TPAVTTYKLV INGKTLKGET 
               
               
                   
               
               
                 TTEAVDAATA EKVFKQYAND NGVDGEWTYD DATKTFTVTE 
               
               
                   
               
               
                 KPEVIDASEL TPAVTTYKLV INGKTLKGET TTKAVDAETA 
               
               
                   
               
               
                 EKAFKQYAND NGVDGVWTYD DATKTFTVTE MVTEVPLEST A 
               
            
           
         
       
     
     In certain embodiments of the method, the ligands comprise or consist essentially of homo- or heteromultimers of immunoglobulin-binding domains derived from a bacterial protein. This is to say that the ligands comprise a plurality of domains as discussed above. The domains in a ligand may all be the same (a homomultimer) or one or more of them can differ from the other(s) (a heteromultimer). In addition to the domains, the ligands may comprise linker structures between the domains, a leader or signal sequence at the N-terminus and a tail sequence at the C-terminus. 
     In some embodiments, the ligands comprise  Staphylococcus  Protein A or an alkali-stabilized immunoglobulin-binding variant of  Staphylococcus  Protein A. As stated above, Protein A comprises the five domains E, D, A, B, C in that order. Examples of commercially available matrices comprising  Staphylococcus  Protein A ligands include MabSelect™ and MabSelect Xtra (GE Healthcare), ProSep™-A and ProSep Ultra Plus (Merck-Millipore), AbSolute™ (Novasep), CaptivA™ PriMab™ (Repligen) and Protein A Diamond (Bestchrom). Alkali-stabilized variants of Protein A are typically homo- or heteromultimers of modified Domain C or Protein Z units, as discussed e.g. in WO03080655A1, WO2008039141A1, EP1992692A1, EP2157099A1, EP2202310A2, EP2412809A1, EP2557157A1, EP2157099 and WO2013109302A2. Examples of commercially available matrices comprising alkali-stabilized immunoglobulin-binding variants of  Staphylococcus  Protein A include MabSelect SuRe and MabSelect SuRe LX (GE Healthcare), Eshmuno™ A (Merck-Millipore), Toyopearl™ AF-rProtein A (Tosoh Bioscience), Amsphere™ Protein A (JSR Life Sciences Inc.) and KanCapA™ (Kaneka Corp.). 
     In certain embodiments of the method, the ligands comprise  Peptostreptococcus  Protein L or an alkali-stabilized immunoglobulin-binding variant of  Peptostreptococcus  Protein L. A commercially available matrix with Protein L ligands is Capto™ L (GE Healthcare). Alkali-stabilized variants of Protein L are discussed in co-pending applications PCT EP2015/079387 and PCT EP2015/079389, both of which are hereby incorporated by reference in their entireties. The ligands can also comprise an amino acid sequence defined by, or having at least 90%, such as at least 95 or 98% sequence homology with, an amino acid sequence selected from the group consisting of SEQ ID NO: 17-19. 
     In contrast to the bacterial protein-derived ligands discussed above, antibody-derived ligands have been found to be unstable towards the sanitization solutions used in the method of the invention. This is particularly the case for ligands derived from single-chain camelid antibodies, as described e.g. in WO0144301A1. Examples of matrices with such ligands include KappaSelect™, LambdaFabSelect™, VIIISelect™ and VIISelect™ (all GE Healthcare). 
     In some embodiments the method comprises, before step b), a step a′) of contacting the matrix with a solution comprising an immunoglobulin to adsorb the immunoglobulin and subsequently contacting the matrix with an elution solution to desorb the immunoglobulin. Step a′) can e.g. be repeated at least 10 times, such as at least 25 times before step b) is applied, but step b) may also be applied after each instance of step a′). Step a′) may further include a cleaning-in-place step, e.g. using 10-500 or 10-100 mmol/1 alkali, such as NaOH as a cleaning solution. 
     In certain embodiments, the content of viable bacteria, vegetative bacteria and/or spores is reduced by at least 3 log 10 , such as at least 5 log 10  or at least 6 log 10  in step b). 
     In some embodiments, the immunoglobulin- or IgG-binding capacity of the matrix after step b) is at least 95%, such as at least 97% of the immunoglobulin- or IgG-binding capacity of the matrix before step b). 
     The support (also called a base matrix) of the matrix can be of any suitable well-known kind, in particular an oxidation-tolerant support, such as a support whose pressure-flow performance is not changed by more than 20% after 24 h incubation at 22+/−2° C. with an aqueous 0.03 M or 0.1 M peracetic acid solution. A conventional affinity separation matrix is often of organic nature and based on polymers that expose a hydrophilic surface to the aqueous media used, i.e. expose hydroxy (—OH), carboxy (—COOH), carboxamido (—CONH 2 , possibly in N-substituted forms), amino (—NH 2 , possibly in substituted form), oligo- or polyethylenoxy groups on their external and, if present, also on internal surfaces. The solid support can suitably be porous. The porosity can be expressed as a Kav or Kd value (the fraction of the pore volume available to a probe molecule of a particular size) measured by inverse size exclusion chromatography, e.g. according to the methods described in Gel Filtration Principles and Methods, Pharmacia LKB Biotechnology 1991, pp 6-13. By definition, both Kd and Kav values always lie within the range 0-1. The Kay value can advantageously be 0.6-0.95, e.g. 0.7-0.90 or 0.6-0.8, as measured with dextran of Mw 110 kDa as a probe molecule. An advantage of this is that the support has a large fraction of pores able to accommodate both the proteinaceous ligands and immunoglobulins binding to the ligands and to provide mass transport of the immunoglobulins to and from the binding sites. 
     The proteinaceous ligands may be covalently coupled to the support, such as where they are attached to the support via conventional coupling techniques utilising e.g. thiol, amino and/or carboxy groups present in the ligand. Bisepoxides, epichlorohydrin, CNBr, N-hydroxysuccinimide (NHS) etc are well-known coupling reagents. Between the support and the ligands, a molecule known as a spacer can be introduced, which improves the availability of the ligand and facilitates the chemical coupling of the ligand to the support. 
     In some embodiments the matrix comprises 5-20, such as 5-15 mg/ml, 5-11 mg/ml or 8-11 mg/ml of the ligand coupled to the support. The amount of coupled ligand can be controlled by the concentration of ligand used in the coupling process, by the coupling conditions used and/or by the pore structure of the support used. As a general rule the absolute binding capacity of the matrix increases with the amount of coupled ligand, at least up to a point where the pores become significantly constricted by the coupled ligand. The relative binding capacity per mg coupled ligand will decrease at high coupling levels, resulting in a cost-benefit optimum within the ranges specified above. 
     In some embodiments the proteinaceous ligands are coupled to the support via multipoint attachment. This can suitably be done by using such coupling conditions that a plurality of reactive groups in the ligand react with reactive groups in the support. Typically, multipoint attachment can involve the reaction of several intrinsic reactive groups of amino acid residues in the sequence, such as amines in lysines, with the reactive groups on the support, such as epoxides, cyanate esters (e.g. from CNBr activation), succinimidyl esters (e.g. from NHS activation) etc. It is however also possible to deliberately introduce reactive groups at different positions in the ligands to affect the coupling characteristics. In order to provide multipoint coupling via lysines, the coupling reaction is suitably carried out at a pH where a significant fraction of the lysine primary amines are in the non-protonated nucleophilic state, e.g. at pH higher than 8.0, such as above 10. 
     In certain embodiments the ligands are coupled to the support via thioether bonds. Methods for performing such coupling are well-known in this field and easily performed by the skilled person in this field using standard techniques and equipment. Thioether bonds are flexible and stable and generally suited for use in affinity chromatography. In particular when the thioether bond is via a terminal or near-terminal cysteine residue on the ligand, the mobility of the coupled ligand is enhanced which provides improved binding capacity and binding kinetics. In some embodiments the ligand is coupled via a C-terminal cysteine provided on the protein as described above. This allows for efficient coupling of the cysteine thiol to electrophilic groups, e.g. epoxide groups, halohydrin groups etc. on a support, resulting in a thioether bridge coupling. 
     In certain embodiments the support comprises a polyhydroxy polymer, such as a polysaccharide. Examples of polysaccharides include e.g. dextran, starch, cellulose, pullulan, agar, agarose etc. Polysaccharides are inherently hydrophilic with low degrees of nonspecific interactions, they provide a high content of reactive (activatable) hydroxyl groups and they are generally stable towards alkaline cleaning solutions used in bioprocessing. 
     In some embodiments the support comprises agar or agarose. The supports used in the present invention can easily be prepared according to standard methods, such as inverse suspension gelation (S Hjertén: Biochim Biophys Acta 79(2), 393-398 (1964). Alternatively, the base matrices are commercially available products, such as crosslinked agarose beads sold under the name of SEPHAROSE™ FF (GE Healthcare). In an embodiment, which is especially advantageous for the sanitization method, the support is a rigid crosslinked agarose. Such agarose supports are highly crosslinked, e.g. according to the methods described in U.S. Pat. No. 6,602,990, U.S. Pat. No. 7,396,467 or U.S. Pat. No. 8,309,709, which are hereby incorporated by reference in their entirety. A rigid crosslinked agarose support in the form of spherical beads and packed to 20 cm bed height in a 2.6 cm inner diameter column gives a water flow velocity v (cm/h) at 3 bar back pressure which is at least 0.14×d 2 , where d is the volume-weighted median diameter (d50,v) of the beads in micrometers. The rigid crosslinked agarose is remarkably stable towards the oxidants used in the methods of the invention. 
     In certain embodiments the support, such as a polysaccharide or agarose support, is crosslinked, such as with hydroxyalkyl ether crosslinks. Crosslinker reagents producing such crosslinks can be e.g. epihalohydrins like epichlorohydrin, diepoxides like butanediol diglycidyl ether, allylating reagents like allyl halides or allyl glycidyl ether. Crosslinking is beneficial for the rigidity of the support and improves the chemical stability. Hydroxyalkyl ether crosslinks are alkali stable and do not cause significant nonspecific adsorption. 
     Alternatively, the solid support is based on synthetic polymers, such as polyvinyl alcohol, polyhydroxyalkyl acrylates, polyhydroxyalkyl methacrylates, polyacrylamides, polymethacrylamides etc. In case of hydrophobic polymers, such as matrices based on divinyl and monovinyl-substituted benzenes, the surface of the matrix is often hydrophilised to expose hydrophilic groups as defined above to a surrounding aqueous liquid. Such polymers are easily produced according to standard methods, see e.g. “Styrene based polymer supports developed by suspension polymerization” (R Arshady: Chimica e L&#39;Industria 70(9), 70-75 (1988)). Alternatively, a commercially available product, such as SOURCE™ (GE Healthcare) is used. In another alternative, the solid support according to the invention comprises a support of inorganic nature, e.g. silica, glass, zirconium oxide etc. 
     In yet another embodiment, the solid support is in another form such as a surface, a chip, capillaries, or a filter (e.g. a membrane or a depth filter matrix). 
     As regards the shape of the matrix according to the invention, in one embodiment the matrix is in the form of a porous membrane. In an alternative embodiment, the matrix is in beaded or particle form that can suitably be porous. Matrices in beaded or particle form can be used as a packed bed or in a suspended form. Suspended forms include those known as expanded beds and pure suspensions, in which the particles or beads are free to move. 
     In a second aspect the current invention discloses the use of a solution comprising an oxidant defined by formula I, 
       R—O—O—H  (I)
 
     wherein R is hydrogen or an acyl group R′—C(O)—, with R′ being a hydrogen or a methyl, ethyl or propyl group, for sanitization of an affinity chromatography matrix having proteinaceous ligands coupled to a support. The proteinaceous ligands comprise or consist essentially of one or more immunoglobulin-binding domains derived from a bacterial protein as discussed above. The use may comprise the methods of any of the embodiments discussed above. 
     Further, the invention discloses a method for sanitization of a chromatography matrix, comprising the steps of: 
     a) providing a chromatography matrix having oxidation-tolerant ligands coupled to a rigid crosslinked agarose support, 
     b) contacting the matrix with a sanitization solution comprising an oxidant defined by formula I, 
       R—O—O—H  (I)
 
     wherein R is hydrogen or an acyl group R′—C(O)—, with R′ being a hydrogen or a methyl, ethyl or propyl group. The ligands can be the oxidation-tolerant proteinaceous ligands as discussed above, but they can also be e.g. cation exchange ligands (e.g. ligands comprising sulfopropyl, sulfoethyl or carboxymethyl groups), anion exchange ligands, (e.g. comprising trimethylammonium or diethylaminoethyl groups), hydrophobic ligands (e.g. comprising butyl, hexyl, octyl or phenyl groups) or multimodal groups (e.g. comprising cation or anion exchange groups in combination with hydrophobic groups). The ligands may be homogeneously distributed over the matrix or they may be exclusively or primarily located in one region of the matrix, e.g. the cores or shells of bead-shaped matrices. 
     As discussed above, the concentration of said oxidant in said sanitization solution can be e.g. 0.01-1 mol/l and the pH can be e.g. 2-12, such as 2-4 or 2-3. The matrix can in step b) be incubated with the sanitization solution for 1 min-24 h, such as 5 min-24 h or 15 min-3 h, and the matrix can e.g. be in the form of spherical beads having a median diameter (d50,v) of 10-200 micrometers, such as 30-100 micrometers. 
     EXAMPLES (ALL PERFORMED AT ROOM TEMPERATURE=22+/−2° C.) 
     Example 1 (Capto L Sanitization Study) 
     The purpose of this investigation was to evaluate the bactericidal and sporicidal effect on bacterial spores and bacteria of eight disinfectants as well as PBS as reference added to Capto L 50% slurry. The effect was tested with contact times of 0 and 15 minutes as well as 1, 4, and 24 hours. 
     The test was performed in slurries of Capto L 50% and disinfectants. Microorganisms were added at a concentration of approximately 10 7  cfu/mL to the suspension and the reducing effect was evaluated after given time intervals by neutralizing the disinfectant. The efficacy of the neutralizer and its ability to recover the inoculated microorganisms was demonstrated by validating the method in parallel with the challenge test. The results were evaluated with regard to log 10 reductions of the microorganisms  Bacillus subtilis  (spores) and  Pseudomonas aeruginosa  (vegetative bacteria). 
     10 7  cfu/mL of the microorganism was added to 10 mL of Capto L 50% slurry with disinfectant. Samples were mixed and duplicate samples of 0.1 mL were added to 50 mL of neutralizing agent (0.075 M phosphate buffer with 0.3% lecithin, 3.0% Tween 80, 0.5% sodium thiosulfate and 0.1% L-histidine). The total solution was analyzed by filtrating fractions corresponding to 10-times serial dilutions. Filters were rinsed three times with 100 mL of 0.9% NaCl. As positive control each microorganism was added to 50 mL of neutralizing agent, the same amount added as for the disinfectant challenge tests. The total solution was analyzed by filtrating fractions corresponding to 10-times serial dilutions. Filters were rinsed three times with 100 mL of 0.9% NaCl. Filters were incubated on TSA (Trypticase Soy Agar) at 30-35° C. for 2-5 days. Preliminary reading was performed after 1-3 days. The reduction of microorganisms was calculated as the log 10  of the surviving microorganisms as compared to that of the positive control. The results show that among the tested disinfectants only 0.1 M peracetic acid and 0.6% formic acid with 3% hydrogen peroxide are capable of efficiently killing  B. subtilis  spores. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Results (log 10  reductions) of viable count of  Bacillus subtilis  when 
               
               
                 added to Capto L 50% slurry containing various disinfectants after 
               
               
                 contact times of 0 and 15 minutes as well as 1, 4 and 24 hours. 
               
               
                 Results are mean values of duplicate samples from the slurries. 
               
            
           
           
               
               
            
               
                   
                 Log10 reduction of  Bacillus subtilis  spores 
               
            
           
           
               
               
               
               
               
               
            
               
                 Disinfectant 
                 0 min 
                 15 min 
                 1 hour 
                 4 hours 
                 24 hours 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 PBS: 20 mM Phosphate, 
                 0.0 
                 0.0 
                 0.0 
                 0.0 
                 0.0 
               
               
                 150 mM NaCI, pH 7.4 
               
               
                 (ref) 
               
               
                 0.5M Acetic acid, 20% 
                 0.0 
                 0.0 
                 0.0 
                 0.0 
                 0.0 
               
               
                 Ethanol 
               
               
                 100 mM NaOH, 60% 
                 0.0 
                 0.3 
                 0.5 
                 1.1 
                 &gt;5.3 
               
               
                 Ethanol 
               
               
                 8M Urea, 0.5M Acetic 
                 0.8 
                 0.7 
                 1.0 
                 0.8 
                 1.0 
               
               
                 acid, 1M NaCI, pH 2.5 
               
               
                 8M Urea. 0.5M Acetic 
                 0.9 
                 1.0 
                 1.0 
                 0.9 
                 1.0 
               
               
                 acid. pH 2.5 
               
               
                 6M Guanidine-HCI, 
                 0.8 
                 0.8 
                 0.8 
                 1.0 
                 1.2 
               
               
                 0.5M Acetic acid 
               
               
                 0.1M Peracetic acid 
                 5.6 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
               
               
                 0.6% Formic acid, 3% 
                 0.4 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
               
               
                 Hydrogen peroxide 
               
               
                 2% Chlorhexidine 
                 1.3 
                 1.2 
                 0.7 
                 1.6 
                 0.2 
               
               
                 digluconale 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Results (log 10  reductions) of viable count of  Pseudomonas aeruginosa   
               
               
                 when added to Capto L 50% slurry containing various disinfectants after 
               
               
                 contact times of 0 and 15 minutes as well as 1, 4 and 24 hours. 
               
               
                 Results are mean values of duplicate samples from the slurries. 
               
            
           
           
               
               
            
               
                   
                 Log10 reduction of 
               
               
                   
                 
                   Pseudomonas aeruginosa 
                 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                 15 
                   
                 4 
                 24 
               
               
                 Disinfectant 
                 0 min 
                 min 
                 1 hour 
                 hours 
                 hours 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 PBS: 20 mM Phosphate, 150 mM 
                 0.3 
                 0.3 
                 0.3 
                 0.3 
                 0.4 
               
               
                 NaCI, pH 7.4 (ref) 
               
               
                 0.5M Acetic acid, 20% 
                 6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
               
               
                 Ethanol 
               
               
                 100 mM NaOH, 60% Ethanol 
                 6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
               
               
                 8M Urea, 0.5M Acetic acid, 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
               
               
                 1M NaCI, pH 2.5 
               
               
                 8M Urea. 0.5M Acetic acid. 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
               
               
                 pH 2.5 
               
               
                 6M Guanidine-HCI, 0.5M 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
               
               
                 Acetic acid 
               
               
                 0.1M Peracetic acid 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
               
               
                 0.6% Formic acid. 3% 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
               
               
                 Hydrogen peroxide 
               
               
                 2% Chlorhexidine 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
                 &gt;6.9 
               
               
                 digluconale 
               
               
                   
               
            
           
         
       
     
     Example 2 (Ligand Incubation, Biacore Test) 
     The aim with this activity was to study the binding kinetics of different chromatography media ligands as a measure of the retained binding capability before and after sanitization with 0.1 M Peracetic acid (PAA). The kinetics was measured by Surface Plasmon Resonance on a Biacore™instrument. The ligands tested were monomers (Z1) and tetramers (Z4) of SEQ ID NO: 13, recombinant Protein A (rPrA), recombinant Protein L (rPrL) and single-chain camelid antibodies against IgG kappa chains (KappaSelect ligand). Z1, Z4 and rPrA were tested with a monoclonal antibody immobilized on a Biacore chip, while rPrL and the KappaSelect ligand were tested with an immobilized Fab antibody fragment.
     1. 1 ml 10 mg/ml Z1, Z4 and rPrA were reduced, alkylated and buffer exchanged to 10 mM NaCl and analyzed on a mass spectrometer (MS) to verify the reduction and alkylation.   2. 1 ml rPrL and KappaSelect ligand were diluted to 10 mg/ml.   3. Reference sample (0 h) was withdrawn, 100 μl and buffer exchanged to 50 mM Ammonium Bicarbonate.   4. 10% 1 M PAA was added and the incubations started.   5. Samples were withdrawn after 1, 2, 4, 8, 16 and 24 h, 100 μl and buffer exchanged to 50 mM Ammonium Bicarbonate to stop the oxidation reaction.   6. The concentrations were measured in all samples by measuring the UV absorbance at 276 nm.   7. The samples were then analyzed on LC-MS and Biacore.   

     The Z1 ligand incubated for 0 to 16 h in 0.1 M PAA has similar affinity before and after SIP. The ligand after 24 h incubation does not change in off-rate but changes in on-rate, which also gives a shift in affinity. 
     The Z4 ligand incubated for 0 to 24 h in 0.1 M PAA has similar affinity before and after SIP. The rPrA ligand incubated for 0 to 24 h in 0.1 M PAA gives some loss in affinity with increasing SIP treatment. The ligand changes in both on-rate and off-rate, and gives a shift in affinity 
     The rPrL ligand incubated for 0 to 24 h in 0.1 M PAA has similar affinity before and after SIP. The LC chromatograms before and after SIP ( FIGS. 1 a  and  b   ) show no signs of degradation. The KappaSelect ligand was so heavily degraded already after 1 h in 0.1 M PAA that it was not possible to perform any kinetics studies on it. The LC chromatograms before and after SIP ( FIGS. 2 a  and  b   ) also show an essentially complete degradation. 
     Example 3 (Matrix Incubation) 
     The aim with these experiments was to test the Sanitization in place (SIP) compatibility of different affinity chromatography media. This was done by calculating the 10% breakthrough dynamic binding capacity (DBC) after SIP with 0.1 M Peracetic acid on six different chromatography media packed in PreDictor RoboColumn 600 μl by using a TECAN robot. The initial DBC was measured on six corresponding reference columns which had not been subjected to SIP. The media were: Capto L (recombinant Protein L), KappaSelect (single-chain camelid antibodies against IgG kappa chains), MabSelect (recombinant Protein A), MabSelect SuRe (multimer of Protein Z variant with substituted asparagines), MabSelect SuRe LX (multimer of Protein Z variant with substituted asparagines) and MabSelect Xtra (recombinant Protein A). The support in all these media is rigid crosslinked agarose. 
     Methods
         1. Wash/removal of storage solution: 10 column volumes (CV) (6×1000 μl) 20 mM phosphate, 150 mM NaCl pH 7.4   2. Addition of 20 CV (12×1000 μl) SIP solution (0.1 M peracetic acid)   3. Sealing of bottom and top of the mini-columns with column plugs, Parafilm and aluminium foil.   4. Incubation in SIP solution for 24 hours at room temperature   5. After 24h SIP incubation, wash: 10 CV (6×1000 μl) 20 mM phosphate, 150 mM NaCl pH 7.4   6. Sample loading: 12*600 μl Fab/Mab at different concentrations, residence time 6 min   7. Collection of unbound sample in UV-readable plates and measurement of UV absorbance at 280 (and 300 nm)   For DBC of columns not subjected to SIP, points 1, 6 and 7 were done.       

     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Dynamic binding capacities before and after SIP 
               
               
                 (24 h incubation in 0.1M peracetic acid) 
               
            
           
           
               
               
               
               
            
               
                   
                 DBC control, no SIP 
                 DBC after SIP 
                 ΔDBC 
               
               
                 Matrix 
                 (g/L) 
                 (g/L) 
                 (g/L) 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Capto L 
                 30 
                 29 
                 −1 
               
               
                 KappaSelect 
                 20 
                 0 
                 −20 
               
               
                 MabSelect 
                 52 
                 51 
                 −1 
               
               
                 MabSelect SuRe 
                 50 
                 51 
                 1 
               
               
                 MabSelect SuRe LX 
                 63 
                 63 
                 0 
               
               
                 MabSelect Xtra 
                 59 
                 60 
                 1 
               
               
                   
               
            
           
         
       
     
     Example 4 (Matrix Incubation Capto L) 
     A PreDictor™ (GE Healthcare) 96-well filter plate with 6 microliters Capto L in each well was subjected to the following procedure: 
     Removal of PreDictor storage solution (20% Ethanol)
         Wash: 3×200 μl 20 mM phosphate, 150 mM NaCl pH 7.4   Wash 3×200 μl MilliQ   Addition of 600 μl SIP solutions and 20 mM phosphate, 150 mM NaCl pH 7.4 (control) (48 solutions and duplicates in plate)   Sealing of bottom and top of the plates with Parafilm   Incubation in SIP solutions for 4 or 24 hours with shaking at 450 rpm       

     Liquids were removed by centrifugation (500×g, 1 min). 
     The static binding capacity (SBC) of a Fab was determined by:
         1. Removal of SIP solutions   2. Wash: 1×600 μl MilliQ, 1×600 μl PBS   3. Equilibration: 3×200 μl 20 mM phosphate, 150 mM NaCl pH 7.4   4. Sample loading: 200 μl Fab at a concentration of 2.5 mg/mL, incubation 10 min and 90 min at 1100 rpm   5. Collection of unbound sample in UV-readable plates and measurement of UV absorbance at 280 (and 254 nm)       

     Liquids were removed by centrifugation (500×g, 1 min). 
     The UV absorbance of the PBS buffer at 280 nm (path check on) was subtracted from the UV absorbance of the flow through fraction (A280-blank280) 
     The concentration in the flow through fraction was calculated using a standard curve (A280-blank280)/1.2796 
     
       
         
           
             
                 
             
              
             
               Calculation 
                
               
                   
               
                
               of 
                
               
                   
               
                
               the 
                
               
                   
               
                
               SBC 
                
               
                 : 
               
             
              
             
                 
             
           
         
       
       
         
           
             
                 
             
              
             
               SBC 
               = 
               
                 
                   
                     Vsample 
                     Vmedium 
                   
                    
                   
                     ( 
                     
                       Csample 
                       - 
                       Cunbound 
                     
                     ) 
                   
                 
                 - 
                 
                   
                     
                       Vr 
                       * 
                     
                     Vmedium 
                   
                    
                   Cunbound 
                 
               
             
           
         
       
       
         
           
             
                 
             
              
             
               Vsample 
               = 
               
                 200 
                  
                 
                     
                 
                  
                 µl 
               
             
           
         
       
       
         
           
             
                 
             
              
             
               Vmedium 
               = 
               
                 6 
                  
                 
                     
                 
                  
                 µl 
               
             
           
         
       
       
         
           
             
                 
             
              
             
               Vr 
               = 
               
                 
                   6 
                   + 
                   
                     0.6 
                     * 
                     Vmedium 
                   
                 
                 = 
                 9.6 
               
             
           
         
       
       
         
           
             Vr 
              
             
               : 
             
              
             
                 
             
              
             The 
              
             
                 
             
              
             retained 
              
             
                 
             
              
             volume 
              
             
                 
             
              
             
               i 
               . 
               e 
               . 
               
                   
               
                
               filter 
             
              
             
                 
             
              
             volume 
              
             
                 
             
              
             
               ( 
               
                 6 
                  
                 
                     
                 
                  
                 µl 
               
               ) 
             
              
             
                 
             
              
             and 
              
             
                 
             
              
             liquid 
              
             
                 
             
              
             volume 
              
             
                 
             
              
             in 
              
             
                 
             
              
             resin 
              
             
                 
             
              
             
               ( 
               
                 0.6 
                 * 
                 6 
               
               ) 
             
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Remaining static capacities of Capto L for a Fab after 4 or 24 h 
               
               
                 incubation in SIP solutions, compared to the control, 20 mM phosphate, 
               
               
                 150 mM NaCl pH 7.4 (PBS). SBC values were determined both for 
               
               
                 10 and 90 minutes incubation with the Fab sample. 
               
            
           
           
               
               
               
            
               
                   
                 Relative remaining SBC (%) 
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 4 h 
                   
                 24 h 
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 SIP solution 
                 10′ 
                 90′ 
                 10′ 
                 90′ 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 100 mM Peracetic acid 
                 109 
                 101 
                 107 
                 105 
               
               
                   
                 500 mM Peracetic acid 
                 106 
                 103 
                 97 
                 102 
               
               
                   
                 5% H2O2 
                 104 
                 102 
                 102 
                 105 
               
               
                   
                 0.6% formic acid, 3% 
                 108 
                 105 
                 104 
                 106 
               
               
                   
                 H2O2 
               
               
                   
                   
               
            
           
         
       
     
     Example 5 (Matrix Incubation with MS Analysis) 
     200 mg wet matrix was washed with water and incubated 24 h with 0.1 M peracetic acid. The matrix was removed by filtration and the incubation solution was analyzed on a Waters AQUITY H-Class+Waters Xevo Q-TOFMS LC-MS system with a RPLC C 18  RPC column. The presence of protein fragments in the incubation solution was taken as an indication of ligand degradation by the peracetic acid. 
     Seven matrices were tested (all from GE Healthcare), with different proteinaceous affinity ligands: 
     Kappa Select (single-chain camelid antibodies against IgG kappa chains) 
     LambdaFab Select (single-chain camelid antibodies against IgG lambda chains) 
     Factor VII Select (single-chain camelid antibodies against Factor VII) 
     Factor VIII Select (single-chain camelid antibodies against Factor VIII) 
     Capto L (recombinant Protein L) 
     MabSelect Xtra recombinant (Protein A) 
     MabSelect SuRe (multimer of Protein Z variant with substituted asparagines) 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Results from LC-MS analyses of 0.1M peracetic acid incubation solutions. 
               
            
           
           
               
               
            
               
                 Matrix 
                 Result 
               
               
                   
               
               
                 Kappa Select 
                 Degradation of ligand 
               
               
                 Lambda Fab Select 
                 Degradation of ligand 
               
               
                 Factor VII Select 
                 Degradation of ligand 
               
               
                 Factor VIII Select 
                 Degradation of ligand 
               
               
                 Capto L 
                 No degradation, no ligand leakage 
               
               
                 MabSelect Xtra 
                 No degradation, small leakage of intact ligand 
               
               
                 MabSelect SuRe 
                 No degradation, small leakage of intact ligand 
               
               
                   
               
            
           
         
       
     
     Example 6 (Base Matrix Stability) 
     In order to see if the oxidant treatment had any negative properties of the agarose base matrix, a pressure-flow test of a rigid agarose base matrix was carried out on a non-treated matrix sample and a sample which had been incubated with oxidant. 
     Base Matrix 
     The base matrix used was rigid cross-linked agarose beads of 88 micrometers (volume-weighted, d50V) median diameter, prepared according to the methods of U.S. Pat. No. 6,602,990 and with a pore size corresponding to an inverse gel filtration chromatography K D  value of 0.70 for dextran of Mw 110 kDa, according to the methods described in Gel Filtration Principles and Methods, Pharmacia LKB Biotechnology 1991, pp 6-13. 
     Incubation 
     The base matrix was incubated in 30 mM aqueous peracetic acid for 24 h at room temperature and then washed with distilled water. 
     Column Packing 
     300 ml sedimented gel was slurried with distilled water to give a slurry volume of 620 ml and packed in a FineLINE™ 35/600 column (GE Healthcare, Sweden) with inner diameter 35 mm. The packing pressure was 0.10+/−0.02 bar and the bed height was 300+/−10 mm. 
     Pressure-Flow Test 
     Distilled water was pumped through the column at stepwise increasing back pressures up to 7.5 bar. After each pressure increase step, the pump rate was kept constant for 5 min and the volumetric flow rate and back pressure were measured. Linear flow velocities (calculated as the volumetric flow rate divided by the inner cross section area of the column) were plotted against the back pressure and a maximum flow velocity was calculated from the curve, while the maximum pressure was taken as the back pressure at the maximum flow velocity. 
     Results 
       FIG. 5  shows the flow velocity vs back pressure curves for a) non-incubated matrix and b) matrix after incubation. The maximum flow velocity was 1.30×10 3  cm/h before incubation and 1.18×10 3  cm/h after incubation, while the corresponding max pressures were 5.31 and 5.44 bar before and after incubation. The differences are within the experimental error limits of the method, indicating that the peracetic acid incubation did not affect the pressure-flow properties of the matrix. This was further corroborated by measuring the median diameter of the beads in a Coulter Counter, showing that the d50V median diameter was 88.3 micrometers before and 88.5 micrometers after incubation (no statistically significant difference). Also the pore size of the beads was unaffected as shown by the K D  values for dextran of Mw 110 kDa of 0.696 before and 0.692 after incubation. 
     Example 7 (Cleaning, MabSelect SuRe) 
     Aliquots of MabSelect SuRe matrix were fouled with a monoclonal antibody (mAb) feed and then incubated with different cleaning solutions. After cleaning, the matrix was boiled in SDS-DTT buffer to release any proteins and the supernatant was run on an electrophoresis gel in an Amersham WB system (GE Healthcare, Sweden) to determine the amounts of residual foulant proteins. 
     Fouling 
     A 96-well filter plate with 20 microliters MabSelect SuRe in each well (PreDictor MabSelect Sure, GE Healthcare, Sweden) was equilibrated with 3*200 microliters PBS buffer per well and then loaded with 200 microliters mAb feed (CHO cell supernatant with 4 g/l mAb) per well and incubated for 30 min. After washing with 200 microliters PBS, the wells were eluted with 2*200 microliters 50 mM acetate buffer pH 3.5 The equilibration-loading-washing elution cycle was repeated for a total of five cycles and the wells were then equilibrated and distilled water added. The liquid was removed by vacuum filtration or centrifugation after each step (sample load, wash, elution, cleaning) 
     Cleaning 
     The wells were washed with 3*200 microliters distilled water and then incubated with 300 microliters CIP solution 1 for 15 min. After removal of the CIP 1 solution, they were washed with 2*300 microliters PBS and 2*300 microliters water. They were then incubated with 300 microliters CIP solution 2 for 15 min and washed as above. The CIP 1 and CIP 2 solutions are listed in Table 6. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 CIP solutions and amounts of residual foulant proteins on MabSelect SuRe 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 Residual 
               
               
                   
                   
                   
                 foulant 
               
               
                   
                 CIP solution 1 
                 CIP solution 2 
                 (scan intensity) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 PBS (control) 
                 PBS (control) 
                 32400 
               
               
                   
                 PBS 
                 100 mM NaOH 
                 3810 
               
               
                   
                 30 mM peracetic acid 
                 PBS 
                 4580 
               
               
                   
                 30 mM peracetic acid 
                 100 mM NaOH 
                 595 
               
               
                   
                 100 mM peracetic acid 
                 PBS 
                 2030 
               
               
                   
                 100 mM peracetic acid 
                 100 mM NaOH 
                 347 
               
               
                   
                 100 mM DTT in Tris 
                 100 mM NaOH 
                 1150 
               
               
                   
                   
               
            
           
         
       
     
     Analysis 
     The matrix in the wells was prelabeled with Cy5 fluorescent dye using the Amersham WB Cy5 labeling kit, by adding 50 microliters labeling buffer+5 microliters Cy5 and incubating 30 minutes. 50 microliters SDS-DTT buffer was then added and boiled for 5 min with the matrix. The supernatants were loaded on an Amersham WB Gel Card and run together with prelabeled mAb and MabSelect SuRe ligand references plus a set of molecular weight standards. The Gel Card was scanned and the scan signals integrated to give numbers corresponding to the amount of residual foulant retrieved from the matrix. 
     The results show that 30 mM peracetic acid is almost as effective as 100 mM NaOH, while 100 mM peracetic acid is more effective. Particularly good results were obtained with a serial combination of oxidant and alkali. 
     Example 8 (Cleaning, Capto L) 
     This was performed as Example 7, except that a 20 microliter PreDictor Capto L plate, with Protein L-functional Capto L matrix in the wells was used and that the foulant was a domain antibody (dAb) feed, consisting of supernatant from a heat-treated  E. Coli  culture, with periplasmic expression of the dAb. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 CIP solutions and amounts of residual foulant proteins on Capto L 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 Residual 
               
               
                   
                   
                   
                 foulant 
               
               
                   
                 CIP solution 1 
                 CIP solution 2 
                 (scan intensity) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 PBS (control) 
                 PBS (control) 
                 42700 
               
               
                   
                 PBS 
                 15 mM NaOH 
                 6920 
               
               
                   
                 30 mM peracetic acid 
                 PBS 
                 13600 
               
               
                   
                 30 mM peracetic acid 
                 15 mM NaOH 
                 1660 
               
               
                   
                 100 mM peracetic acid 
                 PBS 
                 4150 
               
               
                   
                 100 mM peracetic acid 
                 15 mM NaOH 
                 1960 
               
               
                   
                 100 mM DTT in Tris 
                 15 mM NaOH 
                 7250 
               
               
                   
                   
               
            
           
         
       
     
     Also here, the peracetic acid has a considerable cleaning effect and the effect is further enhanced by serial combination with 15 mM alkali. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. All patents and patent applications mentioned in the text are hereby incorporated by reference in their entireties, as if they were individually incorporated.