PURIFIED TSH PREPARATION, PROCESS FOR ITS PRODUCTION AND ITS USE FOR THE PRODUCTION OF TSH TRACERS FOR TSH RECEPTOR ASSAYS AND IN TSH RECEPTOR ASSAYS

Abstract: TSH preparation which is obtained by purification of crude bovine TSH (thyrotropin), can be converted by direct radioiodination into a radioiodinated TSH tracer for a TSH receptor assay, has a biological activity of more than 40 IU TSH/mg protein and is obtainable by purification of commercial crude bovine TSH by affinity chromatography over an anti-TSH antibody column and subsequent ion exchange chromatography over a weakly acidic cation exchanger having terminal carboxyl groups and based on a polyamide-coated silica gel, a corresponding process for its production and its use for the production of a TSH tracer, in particular for a TSH receptor autoantibody assay.

Description: Purified TSH preparation, process for its production and its use for the production of TSH tracers for TSH receptor assays and in TSH receptor assays The present invention relates to a TSH preparation which is obtained from crude bovine TSH (thyrotropin) by purification, can be converted by direct radioiodination into a radioiodinated TSH tracer for a TSH receptor assay and has increased biological activity (specific receptor binding activity), a process for the production of this preparation and its use for the production of a tracer or for the production of a TSH receptor assay which contains a tracer which was produced from the TSH preparation according to the invention. TSH is a pituitary hormone which performs a central task in the regulation of the thyroid function. Its release is stimulated by the hormone TRH formed in the hypothalamus and controls the formation and release of the most important thyroid hormone thyroxine (T4). By means of a feedback, the content of thyroxine in the serum controls the release of TSH. The formation of thyroxine by the thyroid cells is stimulated by TSH by virtue of the fact that the TSH released by the pituitary binds to the TSH receptor of the thyroid cell membrane. However, various types of autoantibodies can also be formed against the same TSH receptor in different pathogenic conditions. Depending on the type of the autoantibodies, either the formation and release of thyroxine may be inhibited by shielding of the TSH molecules at the TSH receptors or this thyroid hormone is released in an uncontrolled manner because the TSH receptor autoantibodies, like the TSH, stimulate the synthesis and release of thyroid hormones. The excess thyroid hormone resulting in the latter case manifests itself, inter alia, as a hyperthyroidosis such as Graves' disease. The detection of TSH receptor autoantibodies is thus very important for clinical practice, and a number of radioreceptor assays which permit the determination of such autoantibodies in biological fluid are already known. Such TSH receptor assays function similarly to competitive radioimmunoassays, except that TSH receptors are used as a specific binding agent in the assay instead of antibodies as in the classical radioimmunoassays. In the known TSH receptor autoantibody assays, these receptors originate from animal thyroid tissue, in particular porcine TSH receptor preparations being used. They are available in soluble form and are used in an amount which is less than the stoichiometric amount. When the assay is carried out, TSH receptor autoantibodies from a patient's serum and a labelled TSH which is used as a tracer and is usually a bovine 125 I-labelled TSH compete for a limited number of binding sites of this receptor reagent. The smaller the number of autoantibodies present in the serum sample, the more the labelled TSH tracer molecules are bound by the receptor. The basic principles and details of the determination of the TSH receptor autoantibodies in human serum are described in a large number of publications, of which - in addition to the product information of the various manufacturers (TRAK* of the Applicant; assays of the companies Byk Sangtec, Biocode and Chronus) in connection with their assays - the following may be mentioned in particular: the article by L.C. Harrison and P.J. Leedman in Clin. Biochem. Vol. 23, pages 43 to 48, 1990, Bernard Rees Smith et al. in Endocrine Reviews, Volume 9, No. 1, pages 106 to 121, 1989, and Bernard Rees Smith and Reginald Hall, Methods in Enzymology, Volume 74, pages 405 to 420, 1981. While the TSH receptor required for the TSH receptor assay is usually obtained in a comparatively simple manner by digestion and detergent extraction of thyroid membranes, usually from pigs, and is then ready for use, the TSH used as tracer has to meet very high quality requirements. Thus, the radioiodinated TSH must have certain minimum values for the specific binding to TSH receptors (about 30 to 50% specific binding) with correspondingly low values for unspecific binding (not more than 5% of the total activity of the radioactive marker used) in order to fulfil the clinical expectations for a TSH receptor autoantibody assay. This aim has so far been achieved only with considerable complexity, which is described in detail in the above publications of the author Bernard Rees Smith. In order to obtain a radioiodinated TSH tracer of sufficient quality, the following operations are required: 1. Bovine TSH from bovine pituitaries must be purified by a complicated method. According to the literature, as a rule specific activities of about 30 IU/mg of protein are obtained in the most favourable cases. The best commercially available bovine TSH has a specific activity of 20 IU/mg of protein according to the manufacturer's data (company UCB) . However, other bovine TSH preparations are also commercially available, all of which have a lower specific activity. 2. In order to obtain a radioiodinated TSH tracer, this available bovine TSH must be labelled with 125 I. The iodogenic method, which is complicated but regarded as gentle, is preferably used for this purpose (cf. Bernard Rees Smith in: Methods in Enzymology, Volume 74, pages 408 to 412), incorporation rates of 25 to 70% of 12S iodine in the protein preparation being obtained. A subsequent purification or separation of the free iodine by gel filtration leads to a total yield of 5-10 x 10 s dpm. On the basis of the employed quantity of radioactivity of lmCi (2.22 x 10 9 dpm), this corresponds to a radioactivity yield of 22 to 45% in this known tracer production process. However, when used directly in a radioreceptor test, this tracer leads to specific bindings of only about 11% (B- - UB) (B c = total amount of the bound radioactivity; UB = unspecific binding) . In other words, a major part of the radioactivity is bound to TSH derivatives or fragments which have no receptor binding capability. Such specific binding is far from sufficient for the provision of a TSH receptor autoantibody assay which is satisfactory in practice. 3. According to the so far undisputed opinion of the specialists, it is therefore absolutely essential at this stage to subject the tracer obtained by radioiodination of the bovine TSH to a further affinity purification in order to increase the receptor-binding fraction of the 125 I-TSH. The purification stage carried out at this stage with the already radioiodinated TSH comprises the following processing steps: a) preparation of purified thyroid membranes from the pig (cf. Bernard Rees Smith in Methods in Enzymology) , b) incubation of the tracer obtained as above with the membrane homogenate, a tracer having a sufficient receptor binding capability being bound to the membrane homogenate, c) incubation for 15 minutes at 37°C followed by centrifuging for 15 minutes at 17,000 g in order to obtain a pellet which contains the tracer bound to the membranes, d) after removal of the supernatant solution, this pellet must be rehomogenised in a buffer which contains sodium chloride in a concentration of 2M, so that the binding of the TSH tracer to the receptor used for purification is eliminated, and e) centrifuging for two hours at 100,000 g, the purified radioiodinated TSH tracers being found in the supernatant solution. The final step is the removal of the sodium chloride from the tracer solution via a desalination column. The yield of this extremely inconvenient method is 5%, which leads to a total radioactivity yield in a range from 1.1 to 2.2%. When used in a TSH receptor autoantibody assay, a tracer purified in this manner gives specific binding values of about 45% of the total activity used, which is sufficient for an autoantibody assay. However, the complexity of the method used for the preparation of the radioiodinated TSH tracer results in considerable material losses and also a low radioactivity yield which not only increases the costs but furthermore is disadvantageous for labour and environmental reasons and sets economic limits with regard to the amount of tracer which can be used in an assay and hence to the accuracy of measurement or measuring time. Endocrinology 1985, Vol. 116, No. 4, pages 1379 and 1382, and the publications cited therein describe the processes for the purification of crude bovine TSH. It is reported that a very pure TSH having extremely high biological activity can be obtained by a reversed-phase HPLC (RPLC) chromatography method described in this publication. On repeating the purification process described in the stated publication, however, it was found that, in accordance with the stated publication, very pure protein fractions can be obtained depending on the chromatographic elution, but that, according to the assay method described below, these fractions have lost their receptor binding capability at least with respect to the porcine TSH receptor described in TSH receptor assays and therefore also cannot be used for the preparation of a TSH tracer having high biological activity. When the work leading to the present invention was begun, the problem to be solved was therefore to find an alternative to the complicated preparation of radioiodinated TSH tracers which to date is regarded as essential among specialists, said alternative permitting the preparation of said tracers in a simpler, more reliable manner with smaller material losses and higher radioactivity yields. It was found, surprisingly, that this problem can be directly solved if a new TSH preparation is provided which is distinguished with respect to TSH preparations known to date by the fact that its biological activity, measured as specific receptor binding activity, in the assay method described below is improved, and that, in its direct radioiodination, it gives a radioiodinated, highly active TSH tracer which can be used directly as a tracer. According to a first aspect of the present invention, the latter thus provides a TSH preparation which is obtained by purification of the crude bovine TSH, has a biological activity which is improved by a factor of more than two compared with the best commercially available TSH preparations and, with regard to its composition, for example with regard to accompanying substances of the actual biologically active TSH, has a purity such that direct radioiodination by known methods is possible without harmful losses of activity. According to a further aspect of the present invention, a process is provided which for the first time permits the production of such a TSH preparation. Another aspect of the present invention relates to the use of the TSH preparation according to the invention, having greatly improved biological activity, for the production of TSH tracers by labelling of the TSH preparation according to the invention, a radioiodinated TSH tracer which can be used in TSH receptor autoantibody tests without further purification being obtained in particular in the direct radioiodination of the stated preparation. According to a further aspect of the present invention, this novel high-quality radioiodinated TSH tracer, when used in a TSH receptor autoantibody assay operating according to the principles known per se, permits the provision of such an assay in which a considerable reduction in the assay times is possible owing to the increased tracer radioactivity. These various aspects of the present invention which solve the problems of the prior art are covered by the substance Claims 1 to 3 relating to the novel TSH preparation, the process Claims 4 to 9 relating to the process for its production, the use Claims 9 to 12 relating to the use of the novel TSH preparation for the production of novel labelled TSH tracer obtained therefrom in particular by direct radioiodination, and Claims 13 and 14 relating to the use of the TSH preparation or of the TSH tracer obtained therefrom by direct radioiodination in a TSH receptor assay for the determination of TSH receptor autoantibodies. Further advantageous embodiments and subjects of the invention aspects claimed and described in the present application are evident to one skilled in the art from the description and the embodiments described below. The invention is based on the surprising finding that, contrary to the prior art, it is possible for the crude (natural) TSH preparations obtained in the conventional manner to be subjected to a certain further purification which results in a considerable increase in the biological activity of the TSH preparations which manifests itself as a receptor binding capability, i.e. an increase by a factor of more than two compared with the best commercial preparations and by very much higher factors compared with commercial preparations having a low biological activity, and that there is no formation of accompanying substances which interfere with the subsequent labelling reactions. By purifying the TSH preparations and increasing their activity prior to further processing by coupling with labels in order to obtain tracers, in particular prior to radioiodination, it is possible, by direct labelling, to obtain preparations exhibiting high specific binding to the TSH receptor and having a high radioactivity yield without the necessity of the complicated purification of the labelled TSH preparation by affinity chromatography, which has been described to date in the literature as being necessary. The values obtainable according to the invention for the bound radioactivity, in combination with the good receptor binding capability, make it possible in principle to modify known TSH receptor assays for the determination of TSH autoantibodies in such a way that the measured values required for a statistically relevant result can be obtained in very much shorter times than in all known and commercial processes. s The present invention makes it possible to obtain a radioiodinated bovine TSH which is suitable as a tracer having a radioactivity yield about 40 times higher compared with the prior art, which can be used directly as a tracer in a TSH radioreceptor test after separation of the radioactive iodine not incorporated during the labelling reaction and which has a receptor binding capability which is comparable or even superior to that of the known radioiodinated TSH tracer purified by a complicated procedure. The TSH preparation according to the invention, obtained by purification of crude bovine TSH, is characterised by a biological activity of more than about 40 IU TSH/mg protein, the biological activity being, as a rule, about 55 IU TSH/mg protein. The biological activity of the TSH preparation according to the invention is determined by the process below, and the stated values for the biological activity are directly comparable to corresponding values of the known commercial products, since the standard defined below and valid for establishing the international units (IU) is used as a reference substance. Determination of the specific receptor binder activity (biological activity) of bovine TSH In the present description and the Claims, the biological activity is stated in values as obtained in the determination described below: The biological activity is determined with the aid of the commercially available TRAK-Assay from Henning Berlin. In this test, 125 iodine-labelled bovine TSH binds to a porcine TSH receptor. The TSH preparation whose biological activity is to be determined is used as the sample in the stated assay and competes with the 125 I-labelled bovine TSH, used as a tracer, for the binding sites of the TSH receptor used in the test. Taking into account the protein concentration of the TSH preparation investigated in each case, TSH preparations having a high specific receptor binding activity lead to the bound amount of labelled TSH tracer or the bound radioactivity being too low. Using the international standard or using TSH preparations whose biological activity is known in IU TSH/mg protein, the biological activity of unknown TSH preparations can be determined in this manner. The preparations according to the invention are distinguished by biological activities which have more than 40 IU TSH/mg protein and typically about 55 IU TSH/mg protein. The commercially available TRAK-Assay R used for the determination of biological activity has 125 I-labelled bovine TSH and porcine TSH receptor as components, the preparation of both components being carried out according to the prior art commented on at the outset and described in the stated publication by Bernard Rees Smith and Hall (Meth. Enzym. 74, pages 405 to '420, 1981). The test principle of the known assay may be summarised as follows: Bovine TSH was extracted in a known manner from bovine pituitaries, concentrated by a chromatographic method, labelled with 12S iodine and finally subjected to an affinity purification on porcine TSH receptor to obtain the tracer. For the preparation of the porcine TSH receptor, bovine thyroids are homogenised in a detergent-free buffer. Centrifuging is carried out, the supernatant solution with the water-soluble protein is discarded, the resulting pellet is rehomogenised with detergent-containing buffer (the membrane proteins being solubilised) , after which centrifuging is carried out a second time, and the resulting supernatant solution is the TSH receptor preparation used for the test. The TRAK-Assay R is carried out as in the working instructions provided with this test by the manufacturer Henning Berlin, according to the following steps: 1. Pipette a 50 /ml sample or standard (TSH preparation to be determined or TSH preparation with known biological activity and concentration, respectively) ; pipette 50 υl of receptor; 3. incubate for 15 minutes at room temperature; 4. pipette 100 μl of 125 I-labelled bovine TSH as a tracer (about 12,500 dpm per determination); 5. incubate for 2 hours at room temperature; 6. pipette 2 ml of ice-cold PEG solution (polyethylene glycol 6000, 18%); 7. centrifuge for 20 minutes at 2000 g; 8. decant the resulting supernatant solution; 9. measure the radioactivity in the remaining sediment. For the determination of the receptor binding activity of a TSH preparation to be tested, the latter is measured in different dilutions. The determination of the protein concentration of the preparation to be tested is carried out in a known manner by the BCA method from the company Pierce. The calibration was carried out by standardisation of the above measuring system with the reference material "International Standard of Thyrotrophin, bovine, code 53/1 of the National Institute of Biological Standards and Control, UK" . For various TSH preparations, the following values were determined: TSH preparation Biological activity (Origin) ;iU TSH/mg protein) SIGMA, Order No. : T 3538 2.0 Lot No. : 22H0695 UCB, Order No, I050BTSH 20.0 Batch: 011-1 TSH preparation according to the invention which was obtained by the process described below 55.0 According to the present invention, TSH preparations having a considerably improved biological activity can thus be obtained. It should be pointed out here that the receptor binding capability, which serves as a measure of the biological activity, is an extremely sensitive product property which must not be confused with a chromatographic product unit and which simultaneously represents a very much more sensitive measure than, for example, the antibody binding capability. A TSH preparation according to the invention is obtainable by subjecting any TSH preparation obtained by the conventional process or any commercial crude bovine TSH preparation first to gentle purification by affinity chromatography on an anti-TSH antibody column and then to ion exchange chromatography over a weakly acidic cation exchanger, all operations being carried out below room temperature and unnecessary waiting times during processing being avoided. The process for the production of a TSH preparation according to the invention, which is claimed in general form in Claims 4 to 8, is described in detail below with reference to an embodiment: Production of a TSH preparation obtained from crude bovine TSH and having improved biological activity 1. Production of an anti-TSH affinity column for purification of crude, bovine TSH by affinity chromatography The production was carried out in accordance with the instructions in the "Carbolink R " Manual from the company Pierce, Rockford/Illinois, USA, whose protein coupling gel was used. a) For the preparation of an oxidised anti-TSH antibody, 100 mg of sodium periodate were added to 25 mg of monoclonal anti-TSH antibodies 5405 (Lot No. SP005, obtainable from Oy Medix Biochemica Ab, Kauniainen, Finland) and 25 ml of 0.1 M sodium phosphate buffer (pH 7.0) at room temperature, and mixing was carried out until the solution had become completely clear. Incubation was then carried out for 30 minutes at room temperature. The anti-TSH antibody 5405 is specific for hTSH (or the beta subunit of hTSH) and has an affinity constant of 5 x 10 s 1/mol hTSH. It is prepared in vitro and is sold as an affinity-purified Ig fraction in 0.15 mol/g of NaCl with a content of 0.1% of NaN 3 (protein concentration 1.02 mg/ml) . Its use for the purification of bovine TSH is not among the possible uses stated by the manufacturer. Instead of the stated antibody, it is possible to use other anti-TSH antibodies whose suitability can be relatively simply determined on the basis of their ability to purify crude bovine TSH by the affinity purification described here. (b) The oxidised antibody obtained in stage a) is separated from low molecular weight components by means of desalination columns (NAP-25 from Pharmacia, Uppsala, Sweden) . The desalination buffer used is 0.1 M sodium phosphate (pH 7.5) . (c) After desalination, the antibody (40 ml) is mixed with a Carbolink gel washed beforehand in 0.1 M sodium phosphate (pH 7.0) and is incubated at 4°C for 20 hours with gentle shaking. (d) The column material is then transferred to a glass column (BioRad, 1 x 20 cm) , washed with 100 ml of 0.1 M glycine HCl buffer (pH 2.8) and equilibrated in 0.1 M sodium phosphate buffer (pH 7.0). 2. Purification of crude, bovine TSH by affinity chromatography Various samples of crude, bovine TSH (obtainable from the companies Sigma, Armour, Calbiochem and Fluka) (50 IU in 5 ml of 20 mN sodium phosphate (pH 7.0)) are allowed to seep at 4°C into the anti-TSH affinity column prepared as above and are incubated for 30 minutes. Thereafter, the column is washed with 20 mM sodium phosphate buffer (pH 7.0) (flow rate 1.5 ml/min, total volume 180 ml), after which the elution of bound peptide by means of 50 mM glycine HCl buffer (pH 2.8) is carried out at 1.5 ml/min and 4°C. The column outflow is continuously measured to determine its optical density at 280 ran, and eluting protein is collected (final volume 6 ml) . The solution containing the desired protein is immediately diluted 1:2 with water and is used in the subsequent ion exchange chromatography. Accompanying investigations during the affinity chromatographic purification described has shown that, under the stated conditions (pH 7.0), bovine TSH is completely bound to * the column material. After the column has been washed free of unbound substances, it is desorbed in about 80% yield by elution with the acidic buffer. The results according to the invention were obtained using various crude TSH preparations having very different specific activities (crude TSH from the company Sigma, specific activity 1.8 IU/mg; similar preparations from the companies Calbiochem, Armour and Fluka; and directly freshly prepared bovine pituitary extract) . Any contaminated preparations can therefore be used for the rapid and effective purification of bovine TSH. 3. Ion exchange chromatography over a weakly acidic cation exchange resin The TSH preparation obtained in the purification by affinity chromatography and diluted to twice the volume is applied at 4°C and at a flow rate of 0.8 ml/min directly onto a column equilibrated in 10 mM ammonium acetate (pH 4.5) and containing a weakly acidic cation exchange resin (Euramid WCEX; a weakly acidic cation exchange resin having terminal carboxyl groups and based on a polyamide-coated silica gel) . After application, the peptide is eluted in a linear gradient from 10 mM ammonuim acetate (pH 4.5) to 1 M ammonium acetate (pH 4.5) at 0.8 ml/min in 30 min. The column flow is measured continuously for UV absorption at 280 ran. Bovine TSH elutes after about 19 min and is collected directly in a glass vessel cooled with solid carbon dioxide. After freeze-drying of the TSH, the substance can be reconstituted with 20 mM phosphate (pH 7.0) and is then ready for use and can be labelled with 12£ iodine. In the ion exchange chromatography, intact TSH is separated from the TSH decomposed into its subunits, which can be effected rapidly, effectively and with high yield under the conditions according to the invention. The purified TSH according to the invention is obtained directly in solution or, after freeze- drying, in dry form, and its biological activity (specific receptor binding capability) is about 55 IU TSH/mg protein. 4. Radioiodination of the TSH preparation according to the invention 24 tλg of the TSH preparation according to the invention and obtained above, in 100 μl of 0.1 M sodium phosphate buffer (pH 7.4), are mixed with 2.5 Ci (25 Λ1) of 12S iodine (Amersham) , and the reaction is initiated by adding 3 μg of chloramine T (in 20 μl of H 2 0) . After incubation for 30 s, the reaction mixture is separated directly over a protein Pak-125 column from Waters (Millipore Corporation, USA) (mobile phase: 300 mM sodium phosphate (pH 7.4), 0.1% Lubrol (Sigma), flow rate 0.5 ml/min). The column outflow is measured continuously for radioactivity. Radioiodinated bovine TSH is eluted with an elution time of 17.5 min. The yields of the radioiodination are extremely high. Of the 2.5 Ci of 125 iodine used for the radioiodination, 1.0 to 1.25 mCi are present in the product, which can be used directly as a ready-to-use tracer. About 50% of the radioactivity used are thus contained in the tracer isolated. Instead of radioiodination by the chloramine T method described, radioiodination can also be effected, with essentially the same results, using other known methods, for example the iodogenic method. However, the possibility of carrying out radioiodination without a harmful loss of activity also by the experimentally simple chloramine T method constitutes a considerable practical advantage and reflects the purity of the TSH preparation according to the invention. 5. Use of the radioiodinated TSH tracer in a TSH receptor autoantibody assay The radioiodinated bovine TSH isolated is diluted to the desired final total activity in 10 mM Tris-HCl buffer (pH 7.5), 50 mM sodium chloride and 0.1% bovine serum albumin and is used directly as a tracer in a TSH receptor assay. In contrast to the unanimous opinion to date in the publications cited at the outset, it was found, surprisingly, that the tracer obtained according to the invention has the required receptor binding capability even without subsequent further purification by affinity chromatography, and was qualitatively compar¬ able with, if not superior to, the tracer produced by the complicated conventional method and subsequently purified by affinity chromatography (cf. Table 1) . Table 1: Comparison of different tracers in the TRAK-Assay* of Henning Berlin I Owing to the high yields of the process according to the invention, it is possible to compensate a critical deficiency due to the process technology and associated with the preparation of the tracer used to date and its production process: Owing to the poor yields and high price of the conventional radioiodinated TSH tracer, all known producers of TSH receptor autoantibody assays (apart from the Applicant of the present invention, the companies Byk Sangtec, Biocode and Chronus) are forced to operate with low total radioactivities (10,000 to 15,000 dpm), which, for the users, leads to unfavourably long counting times in the determination of autoantibodies against the TSH receptor (all producers specify counting times of the order of 5 minutes per sample) . Owing to the high biological activity (receptor binding capability) and purity of the TSH preparation obtained in the first step of the present invention, this preparation can be directly radioiodinated without there being a disadvantageous decrease in the specific receptor- binding capacity and without it being necessary to carry out a further purification by affinity chromatography in order to obtain a product having sufficient biological activity. In the process according to the invention, a radioiodinated TSH tracer can be prepared without problems even in large amounts, permitting the use of substantially higher quantities of radioactivity in a TSH receptor autoantibody assay and thus resulting in shorter counting times for the user. Table 2 summarises the differences between the present invention in its various aspects and the prior art. Table 2 Comparison of the conventional process for the production of a radioiodine- labelled TSH tracer with the process according to the invention Since it was not known from the prior art that the crude bovine TSH preparations known to date can be purified in a relatively simple manner with recovery of TSH preparations which have a considerably improved biological activity (receptor binding capability) compared with all commercial TSH preparations, and since it was furthermore not known from the prior art that it is possible, by direct radioiodination of any TSH preparation, to obtain a radioiodinated TSH which has the high specific binding properties required for use in a TSH radioreceptor assay, in conjunction with a high radioactivity yield, the present invention constitutes a considerable surprising technical advance.

Claims: Claims 1. TSH preparation which is obtained by purification of crude bovine TSH (thyrotropin) , can be converted by direct radioiodination into a radioiodinated TSH tracer for a TSH receptor assay, has a biological activity of more than 40 IU TSH/mg protein and is obtainable by purification of commercial crude bovine TSH by affinity chromatography over an anti-TSH antibody column and subsequent ion exchange chromatography over a weakly acidic cation exchanger having terminal carboxyl groups and based on a polyamide-coated silica gel. 2. TSH preparation according to Claim 1, having a biological activity of about 55 IU TSH/mg protein. 3. TSH preparation according to either of Claims 1 or 2, obtainable by a process according to the following Claims 4 to 7. 4. Process for the production of a TSH preparation having a biological activity of more than 40 IU TSH/mg protein, according to any of Claims 1 to 3 , comprising the steps: (1) Treatment of crude bovine TSH over an anti-TSH antibody affinity gel and recovery of an eluate of purified TSH preparation, and subsequent (2) treatment of the TSH eluate purified by affinity chromatography and obtained from stage (1) by ion exchange chromatography over a weakly acidic cation exchange resin, (3) recovery of the fraction of the eluate of stage (2) which absorbs at 280 ran and (4) freeze-drying of the eluate fraction obtained from stage ( 2 ) . 5. Process according to Claim 4, characterised in that the purification of the crude bovine TSH by affinity chromatography is carried out with the aid of an anti-TSH antibody affinity column which is obtainable by (a) oxidation of a monoclonal anti-TSH antibody with sodium periodate, (b) separation of the oxidised antibody from low molecular weight components by means of desalination columns, (c) incubation of the desalinated oxidised antibody with a protein coupling gel and (d) transfer of the gel with the bound anti-TSH antibodies to a conventional column, conventional buffer and washing solutions being used in all stages . 6. Process according to either of Claims 4 or 5, in which the ion exchange chromatography in stage (2) is carried out using a weakly acidic cation exchange resin having terminal carboxyl groups and based on a polyamide-coated silica gel. 7. Process according to any of Claims 4 to 6, in which an anti-TSH antibody having binding properties which are identical or similar to those of the monoclonal antibody 5405 (Medix, Kauniainen, Finland) is used as an antibody for the production of the anti- TSH antibody affinity column for purification stage (1) . 8. Process according to any of Claims 4 to 7, characterised in that the eluate obtained from stage (1) is diluted and is used directly in stage (2), and the eluate obtained from stage (2) is immediately cooled to the temperature of solid carbon dioxide. 9. Use of the TSH preparation according to any of Claims 1 to 3 or of the product from a process according to Claims 4 to 8 for the production of a tracer in a TSH receptor assay by labelling with any labelling molecule known per se. 10. Use of the TSH preparation according to Claim 9 for the production of a radioiodinated TSH tracer for a TSH receptor assay by direct radioiodination, known per se, of the stated TSH preparation without subsequent further purification by affinity chromatography of the tracer preparation obtained in the radioiodination. 11. Use of a TSH preparation according to Claim 10 for the production of a radioiodinated TSH tracer having over 30% specific binding. 12. Use of a TSH preparation according to Claim 10 or 11, in which the total radioactivity yield of the radioiodination is 45 to 50%. 13. Use of a TSH preparation according to any of Claims 1 to 4 or of a product of a process according to Claims 5 to 8, in the form of a radiolabelled TSH preparation obtained by subsequent direct radioiodination of this TSH preparation, as a tracer in a TSH receptor assay for the determination of TSH receptor autoantibodies. 14. Use according to Claim 13, in which the tracer is used in the TSH radioreceptor assay in amounts such that the counting times required for the determination of TSH receptor autoantibodies in a biological fluid and applicable to values of B 0 > 12,500 dpm are in the region of 1 min.

Inventors: BERGMANN ANDREAS, STRUCK JOACHIM, BERGMANN, ANDREAS, STRUCK, JOACHIM
Applicants: BERGMANN ANDREAS, HENNING BERLIN GMBH, STRUCK JOACHIM, BERGMANN, ANDREAS, STRUCK, JOACHIM
Application year: 1993
Main classification: A61K37
IPC codes: A61K35, A61K51, C07K14, G01N33