Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K39/00—Medicinal preparations containing antigens or antibodies
  • A61K39/395—Antibodies; Immunoglobulins; Immune serum, e.g. antilymphocytic serum
  • A61K39/44—Antibodies bound to carriers
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07K—PEPTIDES
  • C07K14/00—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
  • C07K14/435—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans
  • C07K14/52—Cytokines; Lymphokines; Interferons
  • C07K14/555—Interferons [IFN]
  • C07K14/56—IFN-alpha
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07K—PEPTIDES
  • C07K16/00—Immunoglobulins [IG], e.g. monoclonal or polyclonal antibodies
  • C07K16/18—Immunoglobulins [IG], e.g. monoclonal or polyclonal antibodies against material from animals or humans
  • C07K16/24—Immunoglobulins [IG], e.g. monoclonal or polyclonal antibodies against material from animals or humans against cytokines, lymphokines or interferons
  • C07K16/249—Interferons
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
  • C12P21/00—Preparation of peptides or proteins
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K38/00—Medicinal preparations containing peptides

Definitions

• the present invention relates to the purification of human interferon , to a purified form of human interferon and antibodies thereto, and to purification and preparative methods relevant thereto .
• protein includes “glycoprotein” .
• This invention is based on the discovery of purification methodswhich permit the preparation , for the first time, of all the components of human Le form interferon protein substantially free of inactive and otherwise undesirable impurities ,
• the Le form of interferon is defined in a paper by E . A . Havell, B . Berman , C . A , Ogburn , K. Berg, K . Paucker, and J. Vilcek, Proc . Nat . Acad. Sci. USA, 72, 2185 - 2187 (1975) .
• pure human leukocyte interferon proteins have been prepared from crude human leukocyte interferon through a number of special purification steps , and the pure human leukocyte interferon has been characterized by stained protein bands in SDS PAGE (sodium dodecylsulfate polyacrylamide gradient electrophoresis) .
• the pure human leukocyte interferon has a specific activity of about 10 9 IFU per mg of protein; the specific activity found may vary to some extent depending upon the protein determination method employed, and the specific activity on a protein weight basis is judged to be 2 x 10 8 - 2 x 10 9 IFU per mg of protein.
• the fact that the pure interferon shows two major distinct bands is in accordance with prior art findings using crude or partially purified interferon preparations which indicated that human leukocyte interferon comprises at least two major species . At a higher total interferon load, e.g.
• the above-mentioned SDS PAGE system has been found to be capable of showing a more differentiated protein pattern comprising six interferon protein bands , i. e. the two strongly stained bands at 18,410 ⁇ 200 Daltons and 20, 180 ⁇ 200 Daltons , respectively, a medium-stained band at 20,420 ⁇ 200 Daltons (corresponding to the above-mentioned minor stained band) and just visible protein bands at 19,500 ⁇ 200 Daltons , 21, 130 ⁇ 200 Daltons, and 23,440 ⁇ 200 Daltons , respectively.
• interferon protein bands i. e. the two strongly stained bands at 18,410 ⁇ 200 Daltons and 20, 180 ⁇ 200 Daltons , respectively, a medium-stained band at 20,420 ⁇ 200 Daltons (corresponding to the above-mentioned minor stained band) and just visible protein bands at 19,500 ⁇ 200 Daltons , 21, 130 ⁇ 200 Daltons, and 23,440 ⁇ 200 Daltons , respectively.
• each of the individual components in the above-mentioned bands of the SDS PAGE acrylamide gradient gel has been found to show biological interferon activities : antiviral activity, ability to neutralize only an ti- human leukocyte interferon (but not anti-human fibroblast interferon) , and anticellular activity, plus a variety of so-called non-viral activities, as exemplified by potentiation of Natural Killer cells , potentiation of MLC-CML, increase of HLA antigens , etc .
• the complete purification of interferon proteins makes it possible, for the first time, to produce anti- interferon which is strictly specific to the active species simply by immunizing animals with the pure interferon preparation or one or more of its components .
• Such strictly monospecific anti-interferon is extremely useful for antibody affinity chromatography for purification of crude or partially purified interferon to obtain, in a simple and economic way, large amounts of pure interferon or highly purified interferon for clinical purposes , standardization, chemical studies , sequence studies , and as immunogen for repeated preparation of monospecific anti-interferon. It is within the scope of the present invention not only to purify human leukocyte interferon by means of the monospecific antibody raised against the pure human leukocyte interferon, but also to purify other interferon types which cross-react immunologically with the monospecific anti-interferon, e.g.
• Nemalva interferon human lymphoblastoid interferons ; the Le form interferon constitutes about 85% of the biological activity of human lymphoblastoid or Namalva interferon, vide E .A. Havell, Y. K . Yip, and J. Vilcek, "Characterization of human lymphoblastoid (Namalva) interferon", J. gen. Virol. , 38, 51 - 59, (1977)) , and interferon containing the Le form obtained by cultivation of a microorganism carrying DNA coding for the production of interferon proteins (or proteins having the significant biological interferon activity determinants) .
• the monospecific anti-interferon is also useful for establishing in a manner known per se a genetic engineering system for production of interferon protein:
• the first stage is the isolation of messenger RNA from interferon-producing cells in which the interferon synthesis has been triggered by means of an interferon inducer and has reached a degree of completion of the synthesis of interferon proteins at which the immunological determinants (or parts thereof) of the interferon have been expressed, while at the same time, the interferon is still attached to the ribosomes and the messenger
• RNA A high clone producing Namalva cell suspension grown in the usual way or buffy coats (or lymphocytes isolated by Ficoll technique) is preferred as the interferon-producing cells .
• the messenger RNA is isolated from such cells by lysing the cells in a manner known per se and passing the lysate through an antibody affinity column where the antibody bound covalently is the monospecific anti-interferon.
• the antibody column selectively retains not only the interferon, but also the attached messenger RNA.
• salt elution the messenger RNA is isolate from the eluate from the column and is , also, by known methods, treated with reverse transcriptase to obtain the corresponding DNA .
• immunoprecipitation methods may be used:
• DNA coding for interferon or important parts thereof is incorporated in a suitable cloning vector, preferably a miniplasmid, and transformed into a microorganism, the culturing of which produces interferon and/or interferon derivatives released in the culturing medium, from which the interferon is obtained.
• the purification of such interferon obtained by cultivation of the microorganism can suitably be performed in the same manner as described above by passing the crude preparation through an antibody affinity column made by means of monospecific anti-interferon .
• Radiolabelled monospecific anti-interferon may be a valuable tool in the assessment of which clones of the microorganism have received the DNA and are capable of producing interferon or parts or derivatives thereof.
• the pure human leukocyte interferon proteins appear as the above-mentioned three individual protein bands in the SDS PAGE acrylamide gradient gel, together with five-six biological peaks . Whether five or six biological bands are found depends on the exact places at which the gel slice is cut.
• Fig. 1 shows a stained SDS PAGE gradient gel slab prepared at this load as described in the section "Materials and Methods" below. Each of the protein bands has been shown to possess distinct interferon activity .
• Fig. 2 which is a drawing of an SDS slab from another experiment at the same interferon load, Fig.
• the invention relates to human interferon or species thereof having a specific activity of about 2 x 10 8 - 2 x 10 9 IFU per mg protein .
• the methodology concerning the protein determination varies considerably, the actual figure of the specific activity is of less importance compared to the clear demonstration, by SDS PAGE, of the individual species .
• the pure interferon proteins of the invention are, therefore, more suitably expressed as human Le form interferon proteins which under the SDS PAGE and staining conditions defined herein at a total interferon load of 0.9 x 10 6 IFU show two major sharp stained protein bands having antiviral interferon activity at 18,400 and 20, 100 Daltons , respectively, and a minor stained protein band having antiviral interferon activity between 20,300 and 20,400
• the individual components in the abovementioned bands of the SDS PAGE gel show biological interferon activity, ability to neutralize anti-human leukocyte interferon, and anticellular activity, etc.
• the invention also relates to each of the individual components represented by each of the above-mentioned individual SDS - PAGE bands, as well as to any protein having the significant biological interferon activity determinant(s) possessed by the individual components , and to any protein having the significant immunological determinant(s) possessed by the individual components .
• the human interferon proteins of the invention may be derived from human leukocyte interferon prepared using human cells or from cultured human lymphoblastoid (Namalva) cells , or from proteins prepared by cultivation of a microorganism containing DNA coding for the interferon or an important part thereof, such as described above, but also human Le form interferons of other origin, but conforming with the above characteristics , are within the scope of the present invention.
• One aspect of the invention comprises a formulation comprising the pure human Le form interferon protein or proteins adapted for administration to human beings or animals for prophylactic , therapeutic, or immunization effect.
• a formulation may, e. g. , be adapted for parenteral, intranasal, or topical administration .
• a most useful formulation of the pure interferon proteins of the present invention is an aqueous solution.
• Pure interferon proteins in aqueous solution should be stabilized, and the choice of stabilizer will depend upon the use of the solution.
• the stabilizer should be a physiologically acceptable stabilizer, and a suitable stabilizer is a protein or combination of proteins which is non-toxic and non-immunogenic in human beings, such as human serum proteins and fractions thereof, and human albumin .
• a typical preferred stabilizer is 1% human albumin .
• the normal concentration of pure interferon proteins in compositions for parenteral administration to human beings will be in the range corresponding to 1 - 20 million IFU per ml, and a normal daily dose will be 3 to 10 million , e. g. 5 to 10, million IFU totally, preferably administered once or twice a day by intramuscular injection .
• a normal daily dose will be 3 to 10 million , e. g. 5 to 10, million IFU totally, preferably administered once or twice a day by intramuscular injection .
• normal pharmaceutical precautions which are customarily taken in connection with the preparation of parenteral com positions , will also be observed, such as precautions to ensure sterility and freedom from pyrogenicity .
• the- stabilized formulation of the invention is an aqueous solution of pure human Le form interferon protein(s) to be used for immunization of animals for the preparation of monospecific anti-interferon
• stabilization with SDS sodium dodecylsulfate
• SDS sodium dodecylsulfate
• the pure interferon-SDS combination or complex may be formed simply by adding SDS to the aqueous pure interferon proteins , preferably in a concentration of about 0.1% by weight, calculated on the solution, at pH 7.2.
• the SDS complex of the human Le form interferon protein or proteins constitutes , in itself, a valuable aspect of the present invention because of the stability thereof, and a most interesting form of such complex, well suited for storage and transport (suitably at low temperature, e. g. , at a temperature of at the most 4°C or preferably -20°C, is when isolated in solid form such as described below. )
• the use of other stabilizers of the detergent type for this purpose is within the scope of the present invention .
• a further preferred form of the pure human Le form interferon proteins is a form in which they are bound to Cibacron Blue F3GA or another ligand capable of binding the interferon proteins according to the mechanism exhibited by Cibacron Blue F3GA, such as will be explained in greater detail below.
• the pH of the pure interferon protein solution for immunization of animals to prepare the monospecific anti-interferon is preferably about 7.2, and a suitable buffer is PBS (phosphate buffered saline) .
• the stabilized pure interferon protein preparation for immunization of animals may additionally comprise an adjuvant to further increase the antigenicity, and one suitable adjuvant is Freund's adjuvant. It is also within the scope of the invention to increase and/or stabilize the antigenicity of the pure Le form interferon proteins or each member thereof by coupling to an immunogenic carrier (so as to present the pure interferon protein or proteins as a sort of "hapten") in accordance with wellknown principles .
• an immunogenic carrier may be mentioned PPD (Purified Protein Derivative) and BCG (Bacille Calmette Guerin) . However, the use of such immunogenic carriers is not presently preferred.
• mice, rabbit, goat and sheep are preferred animals , but it is also within the scope of the invention to use other animals, and as described below, pig IgG immunoglobulins show distinct advantages for certain purposes .
• the immunization of animals against the pure interferon is performed in accordance with known methods for preparation of anti-interferon , such as described, for example in Acta Path. Microbiol. Scand. Section B , 83, 443 - 460 (1975) , but the fact that the interferon proteins of the invention are pure gives rise to minor variations with respect to the concentration of the immunogen and the immunization time and intervals . Examples of immunization schedules appear from the "Experimental Section" .
• the bleeding of the animal and the isolation of antiserum are performed in accordance with wellknown methods .
• the antibodies prepared as described above are, apart from the trivial fact that they show a natural background characteristic of the animal immunized, substantially specific to the interferon proteins characterized by the above-mentioned SDS PAGE bands .
• An extremely small amount of impurities not seen as stained bands in the SDS PAGE together with the interferon protein cannot be ruled out.
• Such proteins which may represent small amounts corresponding to about 1 - 5% of the total protein content in the pure interferon protein preparation might trigger antibodies against the corresponding impurities .
• One way of checking such a possibility is to construct an anti-interferon column of the relevant antiserum, obtained by immunizing a rabbit with the pure interferon (that is interferon of the above-described characterization which in SDS
• the column is constructed without any absorption at all. Crude human leukocyte interferon is loaded to the column, and a normal antibody affinity chromatography is performed, vide below. The eluate is analyzed in an SDS PAGE
• the “foreign" proteins might also appear by simple spontaneous cross reaction which by chance takes place.
• This aspect is a method for checking whether a particular antibody preparation (e.g. , an antiserum) , is monospecific to its particular antigen, comprising constructing an antibody affinity chromatography column by means of the antibody preparation to be checked, loading a solution containing the antigen plus impurities to the column, and analyzing the eluate from the column to ascertain the presence of any protein different from the antigen.
• a particular antibody preparation e.g. , an antiserum
• the latter analysis is performed by SDS PAGE gradient in the same manner as discussed in connection with the present use of the method in determining the monospecificity of anti-interferon, and the occurrence of bands corresponding to at the most 4 impurity proteins in the eluate will generally be considered a satisfactory indication of monospecificity for most practical uses of the antibody preparation.
• the stained interferon protein bands in the SDS PAGE have preserved their antigenicity completely or to a considerable extent, it is also possible to use the stained interferon proteins directly cut out from an SDS PAGE as antigen preparations for immunizing immunizable animals such as rabbits .
• the stained band cut out from the SDS PAGE is used for the immunization (after preparation described below) , a possible cross-over reaction (or contamination from extremely small amounts of impurities) as discussed above is less likely (compared to the total eluate representing 5 interferon species) .
• antibodies versus the individual species of interferon (primarily the two major species at about 18,400 and 20, 100 Daltons) with optimum specificity may be produced according to the following protocol:
• IFU human leukocyte interferon (as CIF) is purified completely (by means of the "tandem" affinity chromatography described below) and subjected to SDS PAGE .
• the gel is only stained for 10 - 15 minutes at room temperature and is partially destained for 10 minutes followed by a wash in distilled water three times, done in 1 - 2 minutes with 0°C distilled water.
• the exact location of the protein bands is noted (for example by means of a Polaroid photo) , and the two major interferon protein species are specifically removed by cutting out with a sharp knife.
• Each slice is minced by means of a teflon rod in 1 ml
• the term "monospecific anti-interferon” is used both in relation to anti-interferon produced by means of the pure interferon proteins as described above without the step of cutting out from SDS PAGE, and in relation to the antibodies raised against the stained interferon band or bands cut out from the SDS PAGE .
• hybridoma technique is a well-known method for preparing anti bodies and comprises the establishment of monoclonal antibody-producing lymphocytes/myeloma hybrids - (compare, for example, "Current topics in Microbiology and Immunology, Vol. 81, Lymphocyte Hybridomas, Eds . F . Melchors, M. Potter, and N.L. Warner, Springer Verlag, 1978) .
• lymphocytes/myeloma hybrids - comprise, for example, "Current topics in Microbiology and Immunology, Vol. 81, Lymphocyte Hybridomas, Eds . F . Melchors, M. Potter, and N.L. Warner, Springer Verlag, 1978.
• the present invention it was not known or obvious that it would be possible to obtain an anti-interferon-producing hybridoma cell clone.
• mice are immunized with human Le form interferon and spleen cells from the immunized mice are fused with myeloma cells , whereafter the fused hybridoma are cloned, antibody-producing clones are selected and cultured, and antibodies are obtained from the culturing medium.
• Antibodies prepared by hybridoma technique in a mouse system are strictly monospecific and are therefore especially advantageous in radioimmunoassays or other similar tests .
• one particular way of obtaining the antibody is to culture the selected clones in vivo in the animal species from which the spleen cells were derived, and harvesting antibody from the ascites fluid of the animal, and such embodiment is within the scope of the present invention.
• the selection of positive hybridoma clones may be performed by the usual interferon neutralization test.
• the usual interferon neutralization test as a prerequisite, requires that the antigenic determinant of the interferon is located very close to the center(s) of the biological activity (within a distance of about 1 IgG molecule length) , it is likely that antigenic determinants located further away from the center(s) of the biological activity/ activities will not be detected by this test, and it is , hence, likely that "positive" hybridoma clones (producing antibodies against antigenic determinants on the interferon protein which are located at a distance from the biological center which is greater than the length of 1 IgG molecule) will escape detection in the test.
• a more advantageous technique for testing for positive hybridoma clones is to use radio-labelled pure human Le interferon proteins of the invention in a radioimmunoassay.
• the radio-labelled pure human Le interferon proteins can be made by radio-labelling human Le interferon, e . g. , a gel filtrate made by the gel filtration technique described below, by means of a standard radio-labelling technique such as using lactoperoxidase and iodine 135, and then purifying the interferon proteins in the manner described herein , subjecting the purified interferon proteins to SDS PAGE and eluting the radio-labelled pure interferon proteins from the SDS PAGE gel.
• Another method for selecting the positive hybridoma clones in a manner which will detect also such clones that are not detected in the usual interferon neutralization test comprises subjecting an amount, e . g. , 500 ⁇ l, of the supernatant from each clone cultivation to immobilization on a matrix, e . g. , immobilization on CNBractivated Sepharose according to the method described in the section "Materials and Methods" , applying human Le form interferon, e.g. crude human leukocyte interferon, to the resulting treated matrix, e. g.
• elution buffer pH 2.4
• centrifugating by mixing with elution buffer (pH 2.4) and centrifugating, and selecting the clones corresponding to the matrix gel portions from which the eluting buffer portions , in particular the last eluting buffer portions, contain interferon, as the yielding of interferon in the elution is an indication of a positive clone.
• the two above-mentioned advantageous methods for detecting positive hybridoma clones may be applied not only to anti-interferon-producing hybridoma clones , but with evident modifications , also to the detection of positive hybridoma clones producing antibody directed against other proteins .
• antibodies raised against one of the purified interferon proteins of the invention are capable of neutralizing the other purified proteins of the invention.
• the monospecific antibodies of the invention whether raised against a single purified interferon protein of the invention or raised against a combination of purified interferon proteins of the invention, are equally effective for purification of human Le form interferon-containing solutions .
• the monospecific anti-interferon of the invention can be used for determination of the corresponding interferon or interferon component in biological fluids such as by radioimmunoassay or related techniques .
• an interesting and important utility of the monospecific antibodies is for antibody affinity chromatography purification of interferon-containing solutions .
• the antibodies are immobilized on a matrix in a manner known per se, suitably covalently bound to a suitable antibody affinity chromatography matrix such as a cross-linked agarose such as Sepharose 4B from Pharmacia.
• the antibody affinity chromatography purification of interferon-containing solutions may be performed according to any of the wellknown methods , either batchwise or, preferably, using the matrix-immobilized antibody arranged in a column.
• the preparation of antibody affinity columns using the monospecific anti-interferon, and the operation of such columns are performed in a manner known per se.
• the interferon-containing solution applied on such columns may be a crude, unconcentrated interferon preparation, or it may be a concentrated or partially purified interferon preparation.
• the interferon preparation applied on the column may be any interferon preparation containing human Le form interferon, that is , human leukocyte interferons, human lymphoblastoid interferons (Namalva interferons) , or interferon (or important parts thereof) produced by cultivation of a microorganism containing DNA coding for interferon, such as described above .
• the columns may be used for large scale industrial purification of interferon from a crude interferon preparation to result in pure (or highly purified) interferon proteins in the column eluate.
• the pure (or highly purified) interferon proteins prepared in this way are stabilized with suitable stabilizers according to the intended use thereof, such as described above .
• interferon of the interferon preparations applied on the monospecific anti-interferon columns is present in usually very low concentrations , on a weight basis , and as as great amounts as possible of the valuable interferon are to be isolated, it is of importance to minimize any deterioration of the interferon proteins which might be caused due to the presence of proteolytic activity in any biological substance with which the interferon is contacted, and one aspect of the present invention comprises removing any proteolytic activity from any biological material with which the interferon to be purified is in contact.
• One important utility of this aspect is the removal of proteolytic activity from the anti-interferon antibodies (inmunoglobulins) of the invention .
• this removal is suitably performed by treating the antibodies, prior to their binding to the matrix, with matrix-immobilized enzyme inhibitor or enzyme destructor which is not harmful to immuno globulins (or the important fragments thereof) .
• the antibodies may be passed through a column of matrix-immobilized poly-L-lysin and/or matrix-immobilized Soyabean Trypsin inhibitor, and/or matrix-immobilized kallikrein inactivator.
• An example of a suitable treatment of the antibodies is passage through a column of poly-L-lysin covalently bound to cross-linked agarose such as Sepharose 4B , followed by passages through a column of Soyabean Trypsin inhibitor covalently bound to the same matrix. It has been found that this removal of proteolytic activity increases the recovery of interferon activity in antibody affinity chromatography purification of interferon-containing solutions .
• the monospecific anti-interferon when covalently' bound to a matrix such as cross-linked agarose, is preferably bound to such an extent that the total amount of antibody covalently bound to the matrix corresponds to at the most 85% of the immunoglobulins used at the covalent binding stage, such as described by the present inventor in Scand. J. Immunolog. , 6, 77 - 86 (1977) . This results in the highest recovery of interferon from the column.
• the eluate from the monospecific anti-interferon affinity chromatography column is to be used for administration in human beings , it is important that it does not contain any component which might be immunogenic in man.
• One risk which might be associated with antibody affinity chromatography is that immunoglobulins or immunoglobulin fragments liberate from the column and become eluted together with the desired protein or proteins .
• such immunoglobulins or fragments thereof which are immunogenic in man are removed by passage of the eluate through an antibody affinity column in which the antibodies are directed against the anti-interferon immunoglobulins and are of a kind which is non-immunogenic on parenteral administratio to human beings .
• an antibody affinity column in which the antibodies are directed against the anti-interferon immunoglobulins and are of a kind which is non-immunogenic on parenteral administratio to human beings .
• Immunoglobulins which are non-immunogenic on parenteral administration to human beings are primate immunoglobulins , but the access to primate immunoglobulins directed against the immunoglobulins of the animal used for the preparation of the monospecific anti-interferon may be limited or completely precluded, for legal or ethical reasons . Therefore, it is important to note that pig IgG immunoglobulins have been found to be non-immunogenic in man, such as is described in U. S . Patent No . 4, 132, 769. Antibodies produced in a human hybridoma system, when available, would constitute an interesting alternative.
• the removal of any anti-interferon immunoglobulin or immunoglobulin fraction from the eluate of the anti-interferon affinity chromatography is preferably performed by passing the eluate (after adjustment of pH to neutrality) through a column of matrix-immobilized pig IgG directed against the antiinterferon immunoglobulins .
• Pig IgG immunoglobulins directed against the anti-interferon immunoglobulins may be prepared in a manner known per se by immunizing a pig with immunoglobulins from the anti-interferon immunoglobulinproducing animal species, and isolating the IgG immunoglobulin fraction from the antiserum harvested from the pig, in accordance with the methods disclosed in the above-mentioned U. S . Patent No . 4, 132, 769.
• this contribution according to the present invention can be expressed as a method of removing proteins which are immunogenic in man. from a protein solution which is to be administered to human beings , comprising subjecting the protein solution to an antibody affinity chromatography treatment where the antibodies are immunoglobulins directed against the immunogenic proteins , the said immunoglobulins being of a kind which is non-immunogenic on parenteral administration to human beings .
• the non-immunogenic immunoglobulins preferred are primate immunoglobulins or pig IgG immunoglobulins .
• the purification stages performed according to the present invention to prepare the pure human leukocyte interferon proteins (human Le form interferon proteins) from crude human leukocyte interferon comprise concentration by precipitation of proteins with
• KSCN gel filtration, ligand affinity chromatography, and antibody affinity chromatography.
• stages are known per se in the interferon art, the particular combination thereof and the particular conditions applied in certain of the operations constitute novel features, some of which are in themselves aspects of the present invention.
• the particular way in which the stages are performed, and the particular combination of operations have resulted in optimal purification and concentration of the interferon, with minimum loss of interferon proteins during the sequence.
• the KSCN precipitation is preferably performed by lowering the pH of the crude interferon containing a KSCN concentration of 0.5 M. to pH 4.5 instead of the conventional lowering to pH 3.5. This results in a considerably lower amount of protein in the precipitate, thus facilitating the later purification steps .
• the gel filtration is performed with a buffer solution containing 25% by volume of ethylene glycol and being 1 molar with respect to NaCl, incl. PBS (pH 7.2) . This results in a much better resolution than when using PBS or low pH (2,4) alone, or when using urea,
• the ligand affinity chromatography is performed in a novel and extremely advantageous way and constitutes one important aspect of the present invention :
• the said ligand affinity chromatography is performed under specified conditions on an interferon having a specific activity of at least 50, 000 - 100.000 IFU per mg protein, using immobilized Cibacron Blue F3GA as the ligand-.
• Cibacron Blue F3GA as the ligand for affinity chromatography of interferon was known in the art, but according to the invention , it has been found that the selectivity of this ligand increases drastically when particular combinations of conditions are used: the interferon applied should have a much higher specific activity i.e .
• a specific activity of at least 50,000 - 100,000 IFU per mg protein than in the conventional uses of this ligand type (where crude human leukocyte interferon of a specific activity of about 3 - 5 x 10 3 IFU per mg of protein is applied) , and the solution in which the interferon is applied on the column should be in the pH range of 6.5 - 8 and should have an ionic strength which does not essentially exceed the ionic strength of a 10 - 100, in particular 20, mM phosphate buffer, pH 7.2.
• the specificity of the ligand changes, and a higher degree of selective binding of the interferon proteins to the ligand occurs .
• Cibacron F3GA is believed to interact with interferon proteins in a way which indicates the existence of a "dinucleotide fold" and in this interaction, it seems to have the same binding site as polyribonucleotides . It is believed that the particular advantageous properties shown by Cibacron F3GA under particular critical conditions as discussed above will also be exhibited by the other members of the class to which this ligand pertains, and the present aspect of the invention, therefore, is constituted by a method of purifying human interferon, comprising applying an aqueous solution containing human Le form interferon protein in a form having a specific activity of at least 50, 000 - 100,000 IFU per mg of protein, the said solution being buffered to a pH of 6.5 - 8 and having an ionic strength substantially not exceeding the ionic strength of a 10 - 100, in particular 20, mM phosphate buffer, pH 7.2 solution, optionally together with a water miscible organic solvent such as ethanol in amounts of 5 - 80%,
• Cibacron F3GA examples of materials which are matrix-immobilized Cibacron F3GA are "Blue Dextran 2000" (matrix: dextran with molecular weight 2 millions) , and Blue Sepharose CL-6B . Further details concerning these and other materials and their use in the conventional interferon purification appear from Bollin et al. , Preparative Biochemistry, 8(4) , 259 - 274 (1978) .
• the immobilized Cibacron F3GA composition Blue Dextran 2000 coupled to Sepharose 4B (by means of CNBr-activated Sepharose 4B) .
• the elution of the interferon from this type of immobilized ligand has been found, according to the invention, to be extremely selective when using 0.6 M NaCl buffered to pH 7.2, and pH 7.2 is also the preferred pH of the interferon-containing solution applied.
• Fig. 4 shows the elution pattern of a Blue Dextran-Sepharose 4B column loaded with partially purified human leukocyte interferon, 1 ml, specific activity 500,000 IFU per mg protein, subsequent to throughout dialysis versus 20 mM phosphate buffer (PB) , pH 7.4.
• the size of the fractions was 5 ml, and the flow rate was 35 - 40 ml/h .
• the column was washed with 20 mM PB for 2 hours, before it was eluted stepwise with 0.2, 0.4, 0.6, 0.8, and 1.0 M NaCl in PB 7.4, respectively.
• the total eluate (I + II + III) contained 754,000 IFU (in 30 ml) , the originally applied amount being determined to 750,000 IFU. Hence, the recovery was 100%.
• the specific activity of the eluate was 2.1 x 10 7 IFU per mg of protein.
• the purification factor was 42.
• NaCl solution of a concentration of 0.5 - 0.7, in particular 0.5 - 0.65 molar and buffered to a pH of 6.5 - 8, or other aquous solution buffered to a pH of 6.5 - 8 and having an ionic strength corresponding to such NaCl solution .
• the use of other eluants is also within the scope of the present invention.
• salts and/or ethylene glycol in stepwise and/or gradient-wise increasing concentration up to 50%, aminoacids , artificial aminoacids , ampholines , and proteins and protein mixtures .
• the interferon solution may be applied together with a water miscible organic solvent, such as alcohol, in particular ethanol.
• the interferon which is purified by the affinity chromatography according to this aspect of the invention is typically an interferon containing human Le form interferon proteins , such as human interferons (apart from human fibroblast interferons) , that is, e. g. , human leukocyte interferons , human lymphoblastoid interferons and human Le form interferon proteins or important parts thereof when produced by cultivation of a microorganism clone containing DNA coding for the production of such interferon protein.
• human lymphoblastoid interferon contains a minor proportion of interferon of fibroblast character (F form - corresponding to 15% of the biological activity) does not detract from the fact that human lymphoblastoid interferon is, with respect to its major interferon activity, a human Le form interferon in that it contains human Le form interferon proteins (corresponding to 85% of the biological activitiy) having determinants identical with determinants . of human leukocyte interferon proteins , such as has been shown according to the present invention. )
• the specific activity of the interferon preparation applied on the affinity column is 100,000 - 1 ,000, 000, such as 200,000 - 1, 000,000, e . g. about 500, 000, e .g. 500,000 - 1, 000,000
• the eluate from the affinity chromatography column operated in accordance with this aspect of the invention may be an interesting product also for therapeutic use. It will often have a specific activity of at least 30 x 10 6 IFU per mg protein, based on the Lowry procedure using pure human albumin serum as standard, such as 30 x 10 6 - 10 8 , e . g. , 30 x 10 6 - 70 x 10 6 IFU per mg protein .
• this preparation is subject to normal pharmaceutical precautions , such as precautions to ensure sterility and freedom from pyrogenicity.
• the dosage of this preparation will correspond to the dosage stated above for the pure interferon, on a total activity basis .
• the eluate from the affinity chromatography column was, in the original experiments leading to the pure interferon, subjected to final purification by passage through an absorbed antibody affinity column in which the antibodies are immunoglobulins raised against partially purified human leukocyte interferon and then subjected to removal of antibodies against contaminating proteins by several passages through columns of matrix-immobilized crude human leukocyte interferon.
• the covalent binding of crude interferon to a matrix as e.g.
• Sepharose 4B destroys the immunological determinants of the interferon itself, (>98%) , but apparently not the determinants of the major part of the impurities, and this means that when immunoglobulins raised against partially purified leukocyte interferon are passed (normally several times) through the column, the anti-impurities thereof will be retained on the column, while the anti-interferon will pass the column.
• Such absorbed anti-interferon was used in the antibody affinity chromatography stage following the affinity chromatography.
• washes from “interferon antibody affinity chromatographies” , in particular interferon antibody affinity chromatographies performed using the monospecific antibody of the invention, could also be used for this purpose, or such washes could be used together with the crude human leukocyte interferon.
• all the impurities from several interferon antibody affinity chromatograpies could be pooled together, and these impurities could be used instea of or combined with the crude human leukocyte interferon.
• a preferred way of operating the affinity columns is to connect the two columns so that the eluate from the Blue Dextran column at the same time loads the antibody affinity column . This prevents any loss which might otherwise occur if the eluate fractions from the Blue Dextran column were handled separately.
• This method constitutes a further aspect of the present invention and comprises precipitating SDS or a salt thereof from a solution of the protein which contains SDS , preferably in a concentration of 0.1 - 4 per cent by weight, in a particular about 0.1 per cent by weight, to obtain a precipitate comprising a complex or complexes of SDS or a salt thereof with the protein, separating the precipitate from the solution, preferably by centrifugation at ' 0 - 4°C, and redissolving the precipitate in a smaller liquid volume.
• the precipitation of the SDS may suitably be obtained by either a) lowering the temperature to 0°C for about 15 minutes or b) adding a salt, e . g . , a K + salt, which forms a precipitate with SDS or with SDS-protein complexes .
• a salt e . g . , a K + salt
• This method is a valuable method for concentrating aqueous solutions of pure or purified interferons, and, as indicated above, has been found to be an excellent way of concentrating human Le form interferon proteins .
• the total purification sequence performed in accordance with the present invention was found to be extremely activity-preserving: From a starting amount of proteins of 7 x 10 5 gamma, the pure interferon isolated was less than or equal to 1 gamma, (as determined by comparison of protein bands on SDS PAGE) . Yet, the overall decrease in total interferon activity from the starting batch of crude interferon to the pure interferon was only from 4 x 10 6 IFU to 1.85 x 10 6 IFU (about 50%) . This emphasizes the unique character of the purification sequence and the above-mentioned critical stages thereof . MATERIALS AND METHODS .
• Interferon assays were performed according to the well-known standard method (Berg K. , Sequential Antibody Affinity Chromatography of Human Leukocyte Interferon, Scand. J. Immunol. 6, 77 - 86 (1977)) using VERO cells (monkey kidney cells) and Vesicular Stomatitis Virus (VSV) as a challenge virus . All interferon units (IFU) are expressed in international reference units (69/19 B units) (69/19 B reference was obtained from MRC, Mill Hill, U.K. )
• Interferon Partially purified interferon (PIF) with a specific activity of 5 x 10 5 IFU/mg protein was obtained from crude concentrated human leukocyte interferon (CIF) by ethanolic precipitation as described by Cantell, K. , Hirvonen, S . , Mogensen, K. E. and Pyhala, L. , loc . cit.
• Interferon neutralization for determining anti-interferon was performed in a micro-assay system in the following manner: 20,000 VERO cells per well were seeded in 100 ⁇ l medium and kept at 5% COn in a humidified cabinet. On day 2 the medium was removed from the cells , and each well received 100 ⁇ l of a dilution (in medium) of the antiserum, containing an interferon concentration of 6 - 8 IFU/ml (the serum and interferon had been preincubated at 37°C for 1 h) . On day 3 the medium was removed, and all the wells received 100 ⁇ l VSV (diluted to 10 -3 .5 in medium) . On day 4 the CPE (cytopathogenic effect) was determined, and 50% destruction was taken as the end point for the determination of the antiinterferon titer. The titers are expressed as interferon neutralization units (IFU-NU) per ml.
• IFU-NU interferon neutralization units
• Non-monospecific anti-interferon against PIF was produced, according to Mogensen, K. E . , Pyhala, Liisa and Cantell, K. , Acta path, microbiol. scand. Sect. B , 83, 443 - 450, (1975) , partly in sheep, partly in rabbits .
• the titer of the sheep anti-interferon was 100 - 250,000 IFU-NU/ml.
• a rabbit was injected weekly, s . c . with PIF (2 x 10 5 IFU) for more than two years .
• the titer of the rabbit antiinterferon was 15,000 - 30,000 IFU-NU/ml. All immunoglobulins were isolated by 50% ammonium sulphate precipitation, followed by a dialysis versus phosphate buffer saline (PBS) , pH 7.2.
• PBS phosphate buffer saline
• CNBr was from Fluka (stored at -20°C) .
• SDS Sodium dodecylsulphate
• BDH British Drug House
• Soyabean Trypsin Inhibitor (STI) and L-Lysine were obtained from Sigma .
• Sepharose 4B , CNBr-activated Sepharose 4B , CH-activated Sepharose 4B , and Epoxy-activated Sepharose 6B were all purchased from Pharmacia (Denmark) .
• Protein determinations were made by a modification of the Lowry procedure (Berg K. , Sequential Antibody Affinity Chromatography of Human Leukocyte Interferon, Scand. J. Immunol. , 6, 77 - 86 (1977)) which permitted detection of 1 - 2 ⁇ g/ml as the lowest level of proteins detectable (using an LKB Calculation Absorptioner
• Affinity chromatographies were performed at 4°C .
• the gel suspensions were degassed before packed into the columns . Packing was performed by washing with 3 - 5 bed volumes of loading buffer, using a peristaltic pump . Samples (100 ⁇ l) for interferon titrations were taken from either pools or individual fractions and titrated on the same day or frozen in plastic tubes (-20°C) and titrated later. The dilutions were made in medium (incl. 10% calf serum) .
• Antibody affinity chromatography was essentially done as described by Berg (Sequential Antibody Affinity Chromatography of Human Leukocyte Interferon, Scand. J. Immunol. , 6, 77 - 86 (1977)) .
• As loading buffer was used 0.1 M NaOA/0.3 M NaCl at pH 7.2 (flow rate 40 ml/h) .
• Stepwise elution was performed with 0.1 M HOAc/0.3 M NaCl including a minute amount of citric acid (enough to keep the pH firmly at 2.4) .
• the column was stored at 4°C in PBS 1 M NaCl including Penicillin, Streptomycin, Gentamycin and Chloramphenicol (1% of each) .
• the plastic tubes used for collecting the interferon eluate were pre-wetted with 100 ⁇ l of 1% SDS .
• the gels were dried on paper of a good quality (for example, Whatman Chromatographic paper (17 mm)) under heat and vacuum using a gel dryer (Bio Rad, gel slab dryer, model 224) .
• Solutions of five different molecular markers from 0.1 ⁇ g to 10 ⁇ g of each marker per 20 ⁇ l, - Lactalbumin (14,400 Daltons) ; Soyabean Trypsin Inhibitor (20,100 Daltons) ; Carbonic
• the part of the gel intended for interferon determination was cut from the remainder gel and kept at 4°C (in a humidified box) on a glass plate.
• the main part of the gel was stained for 15 minutes ; after destaining for additionally 3 - 5 minutes , weak bands were clearly seen on a blue background, whereby the precise location of the protein bands corresponding to 14,000 and 30,000 Daltons could be established.
• the unstained part of the gel was cut, so it only contained proteins between 14,000 and 30,000 Daltons and was further subdivided in 1 mm pieces by sharp knives .
• the interferon from these slices was eluted with 0.5 ml 0.1 M SDS subsequent to a complete mincing by means of a teflon rod. After 5 h at room temperature (rocking) the interferon activity of the supernatant was determined. The individual fractions were frozen at
• Namalva interferon (NaCIF) was 10 - 12 x 10 3 IFU/mg protein The recovery was about 98%.
• HuLeCIF and NaCIF are shown in Figs . 5 and 6, respectively, and "HULEIF” indicates the human leukocyte interferon, whereas “NALYIF” indicates the Namalva (lymphoblastoid) interferon. It is clearly seen that the interferon activity is effectively separated from the major part of the proteins .
• the gel-filtered human leukocyte interferon solution obtained as described above, was exhaustively dialyzed against 200 volumes of 20 mM PB , pH 7.2 at 4°C. The dialysis was performed twice, the total dialysis time being about 24 hours .
• the dialyzed solution (25 ml, containing 1.8 x 10 6 IFU) was loaded on a column of Blue Dextran-Sepharose 4B . The diameter of the column was 1 cm, and the length of the column was
• the column was pre-washed with 200 - 300 ml of 20 mM PB (phosphate buffer) at pH 7.4.
• the dialyzed interferon preparation was loaded to the equilibrated column, and the column was washed with 75 ml of PB . 4500 IFU was found in the wash.
• the column was eluted with 0.6 M NaCl, 20 mM PB , pH 7.2 whereby more than
• tHe above-mentioned gel-filtered Namalva interferon solution was exhaustively dialyzed and thereafter subjected to Blue Dextran chromatography.
• the input in the Blue Dextran chromatography was 1,600,000 IFU.
• the wash consisted of 70,000 IFU in 50 ml.
• the eluate was obtained by means of 0.6 M NaCl in PB (pH 7.2) .
• the Blue Dextran chromatography of Namalva interferon is illustrated in Fig. 7.
• the fibroblast part of the Namalva interferon was not eluted from the column under the above conditions , but is expected to be eluted using, e.g. , 25% ethylene glycol in 1 M NaCl, pH 7.2.
• the above-mentioned Blue Dextran column was a column of Blue
• the 0.6 NaCl eluates from the Blue Dextran chromatography show a sp ecific activity of 70 x6 10 6 IFU/mg of protein, both for the human leukocyte interferon and for the Namalva interferon .
• these are candidates for parenteral administration in human beings for therapeutic purposes and, in this regard, are much more pure preparations than the commonly used PIF preparations .
• the eluates are stabilized with physiologically acceptable stabilizers such as described further above, for example 1% of human albumin.
• the eluates from the Blue Dextran column are directly transferred to an antibody affinity chromatography column.
• the antibody affinity chromatography column is combined with the Blue Dextran column in a "tandem system" as described below:
• the Blue Dextran column is combined with the equilibrated antibody column prior to the elution, by connecting the outlet of the Blue Dextran column with the inlet of the antibody column. In this manner, the eluate from the Blue
• Dextran column is immediately “caught” by the antibody column.
• This combination makes use of the fact that the elution conditions (0.6 M NaCl, 20 mM PB , pH 7.2) can be used as loading conditions of the antibody column.
• the elution/loading using 20 ml of the eluate/"loading buffer” (this "loading buffer” , of course, at the same time contains the interferon eluted from the Blue Dextran column)
• the two columns are disconnected, and the antibody column is washed further before eluted as described above.
• the human leukocyte interferon eluate from the antibody column contains pure interferon proteins showing a specific activity of more than 10 9 IFU/mg of protein (as assessed by the determination method discussed above) .
• the tubes in which the eluate from the antibody column is collected (fraction size 2 ml) have been pre-wetted with 100 ⁇ l of 1% SDS each. After pooling of the interferon- containing eluate, additional SDS is added up to a total concentration of 0.1% by weight.
• the pooled interferon-containing eluates stabilized with 0.1% SDS are transferred to a 20 ml stainless steel tube pre-cooled to 0°C in an ice bath. After 15 minutes , a precipitate is formed. The precipitate is isolated by centrifugation at 20,000 rpm at 4°C for 20 minutes . The supernatant is discarded (no interferon activity) , and the precipitate is redissolved in 4 ml of 8 M urea and transferred to a Millipore concentration cell, size 8 ml, filter 10,000 molecular weight cut, and concentrated to about 100 ⁇ l at room temperature. Thereafter, additional 4 ml 4 M urea (p.
• the above-mentioned antibody affinity chromatography column had been prepared in accordance with "Binding Procedures" using nonmonospecific anti-PIF which had been absorbed as follows : a total amount of 10 6 IFU-NU of anti-interferon immunoglobulins (corresponding to 4 ml sheep anti-interferon serum) was absorbed three times on a 150 ml column of human serum bound to Sepharose 4B followed by 4 absorptions on a CIF-epoxy Sepharose column and 2 absorptions on a CIF CH-activated Sepharose 4B as described in the below section "Absorption of Anti interferon" and in Scand. J. Immunol. 8, 429 - 436 (1978) . Finally, the immunoglobulins had been absorbed on a poly-L-lysine-Sepharose column (once) and on a Soyabean Trypsin Inhibitor-Sepharose column (twice) .
• the eluate from the Blue Dextran chromatography of Namalva interferon was divided in two portions . One portion was used for SDS PAGE electrophoresis as described below. 250, 000 IFU were loaded to the absorbed antibody column as shown in Fig. 8. No interferon was found in the wash . The interferon was eluted as usual by lowering pH to 2.4, and 235,000 IFU (collected in the presence of 0.1% SDS) were recovered. This eluate was concentrated as described above and further examined in SDS PAGE .
• Fig. 1 shows a stained slab of the electrophoresis of the pure human leukocyte interferon proteins.
• Fig. 2 shows , schematically, the stained slab from another experiment, together with the corresponding interferon activity eluted from an unstained parallel gel strip .
• the striking reproducibility between the two experiments appears from the two Figures , the difference between 20, 100 and 20, 180 being within the experimental accuracy .
• the biological peaks coincide exactly with the proteins .
• Fig. 9 shows the stained slab from the SDS PAGE (load 0.9x10 IFU) , of the pure Namalva interferon proteins (A) , and of the eluate from the Blue Dextran column (B) .
• the bands of the pure Namalva interferon are essentially identical with the bands of pure human leukocyte interferon applied in the same amount.
• the first injection (40,000 IFU) was performed subcutaneously in the back of each mouse .
• the immunization was continued every week with subcutaneous injection of 70,000 IFU.
• the last injection was given intravenously the 9th week (mouse 1) and 10th week (mouses 2 and 3) , respectively.
• mice were killed by breaking their necks two to four days after the last injection, and their spleens were removed under sterile conditions .
• the homogenized cell suspension was transferred to centrifuge tubes and centrifugated for 5 minutes at 170 g at 4°C .
• the cells were resuspended in PBS, and after a second centrifugation, they were resuspended in serum-free DMEM (about 0.5 ml per spleen) .
• the total amount of cells was 10 8 (mouse 1) , 0.8 x 10 8 (mouse 2) , and
• 10 7 X63Ag8 (HPRT-) myeloma cells in the following manner: 10 8 mouse spleen cells and 10 7 8-azaguanin-resistent myeloma cells
• the cells were transferred to 5 ml cultures in 25 ml NUNC bottles which, like the Costar trays , contained a "feeder layer" of macrophages . On shift of medium, the supernatants were obtained, and from these dense cultures , cells were frozen in liquid nitrogen.
• the supernatants of the individual cultures from mouse 1 were subjected to detection of positive clones using the interferon neutralization test. In this manner, one positive clone was found, although with a very low titer (about 2 - 3 IFU-NU per ml) .
• the two interferon species exhibit the same antigenic determinants .
• Biological Effects of the Pure Interferon Proteins .
• the antiviral activity of each of the six stained protein bands shown in Fig. 3 was determined.
• the gel was loaded in two slots, both of which were stained.
• the stained bands in one of the slots is shown at A in Fig. 3.
• the other slot slot was then briefly destained (in 50% methanol, 45% H 2 O 2 , 5% acetic acid) , the exact location of the interferon proteins in the wet gel was recorded, and the gel was rinsed in water and was thereafter sliced as shown at B in Fig. 3.
• the number of gel slices is indicated at C in Fig. 3. In this manner, each interferon protein band was exactly cut out of the gel, without being mixed with the adjacent one.
• the anticellular activity of the pure interferon proteins was investigated by incubating Daudi cells with 1 : 1000 dilutions (in medium) of pure interferon proteins obtained from the eluted SDS
• MHC major histocompatibility antigen
• ⁇ 2 -associated MHC major histocompatibility antigen
• PNAS 75 partially purified human leukocyte interferon , such as described by I. Heron, M. Hokland & K. Berg (1978) , "Enhanced expression of ⁇ 2 microglobulin and HLA on human lymphoid cells by interferon" , Proc . Natl. Acad. Sci. 75: 6215 - 6222 (referred to below as PNAS 75) .
• PNAS 75 Proc . Natl. Acad. Sci. 75: 6215 - 6222
• Fig 10 shows the antiviral profile (as assessed on an SDS PAGE in the same manner as described in connection with Fig. 2) .
• Each of the species from the gel was assessed for NK enhancing activity, using the method described in PNAS 75. Fractions that have antiviral activity as shown in the lower curve gave increased NK, such as illustrated in the upper curve, whereas "base line" fractions did not.
• One arrow indicates only saline added as a negative control, and two arrows indicate partially purified human leukocyte interferon (PIF) used as a positive control. Around 100 IFU antiviral units of each interferon preparation was added per ml.

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