Human erythropoietin-specific sites of monoclonal antibody-mediated neutralization.

Recombinant human erythropoietin (rhuEpo)-specific mouse monoclonal antibodies (MoAbs) have been produced and characterized. All antibodies were specifically reactive with rhuEpo in enzyme-linked immunosorbent assay (ELISA). Epitope exclusion studies showed three distinct epitope regions, A, B, and C, recognized by neutralizing MoAbs. An additional epitope region D was recognized by non-neutralizing MoAbs. Antibodies defining an epitope region competed with each other for binding sites, but did not compete with antibodies defining a different epitope region. Group B antibodies were able to compete for the receptor binding site on rhuEpo with a soluble human Epo-receptor-lg fusion protein. No single peptide sequences were found to specifically interact either with group B MoAbs or with the rhuEpo-receptor. Therefore, it is suggested that epitope region B and the receptor binding site share binding determinants that are primarily composed of conformational epitopes. Because group A and group C antibodies did not compete with the receptor for binding to the receptor binding site of the rhuEpo molecule, it is suggested that neutralization via epitope regions A and C is mediated through binding inhibition caused by conformational changes, transmuting the binding site(s) for the receptor. Conversely, binding to the receptor seems to induce conformational changes in the hormone molecule, eliminating epitopes for group A and C antibodies.

Evidence for the location of the receptor-binding site of human erythropoietin at the carboxyl-terminal domain.

Five different peptides (P1: 84-95; P2: 152-166; P3: 52-63; P4: 7-23; P5: 110-123) homologous to relatively hydrophilic regions of human erythropoietin (huEpo) have been synthesized to identify biologically active domains of the hormone. All peptides were able to induce high titers of peptide-specific antibodies in rabbits. Antisera from rabbits induced by recombinant huEpo (rhuEpo) contained a relatively high amount of antibodies preferentially directed against three peptides (P2, P4, and P5), of which P4 comprised the amino-terminal region, P2 the carboxyl-terminus, and P5 an interior region previously described as the receptor-binding site. The same three peptides were able to induce rhuEpo-specific antibodies, whereas P1 and P3 lacked this activity. Only peptide-P2-induced antisera inhibited the biologic activity of rhuEpo in a cell proliferation assay, indicating that the carboxyl-terminal region of the molecule is essentially involved in the biologic function of rhuEpo.

Development of an ELISA for the detection and determination of contaminating proteins in recombinant DNA derived human erythropoietin.

An enzyme linked immunosorbent assay (ELISA) has been developed for the quantitative determination of the most probable contaminating proteins (MCP) of recombinant human Erythropoietin produced in the mouse fibroblast cell line C-127. The developed ELISA is a double polyclonal sandwich type immunoassay, which allows a quantitation of the MCPs in the range of parts per million. The polyclonal antibody, used for both coat and conjugate in this ELISA, was demonstrated to be reactive with the reference MCPs (a collection of the most probable protein contaminants) by immunoblot analysis and immunoabsorption of radiolabeled MCPs. Affinity purification of this antibody preparation using the immobilized MCPs resulted in an assay with higher signal-to-noise ratio. The assay was demonstrated to be very specific for the MCPs obtained from the rhu EPO purification process. Since the purification of each recombinant DNA derived protein expressed in mammalian cells requires its own unique process, no generic assay for contaminating proteins can be developed. There are only a few common criteria for the development of such multi-antigen ELISA, which will be discussed in this paper.

Granulocyte-macrophage colony-stimulating factor binding sites and oxidative metabolism in human granulocytes.

We investigated the interaction between GM-CSF and its receptor on human granulocytes and on several human tumor cell lines. Specific high-affinity binding for GM-CSF was characterized by Scatchard plot analysis. The specific radioactivity of the 125I-labeled derivative of rH. GM-CSF was determined by self-displacement analysis and calculated to be 30 microCi/micrograms. The maximum concentration of binding sites (B max) in granulocytes was 40 fmol/mg protein (2,200 molecules GM-CSF bound/cell) and the dissociation constant (KD) was 0.42 nM. No binding sites for GM-CSF were found in two lung cancer cell lines, SCLC-16HV and NCI-N417 or in the urinary bladder carcinoma cell line 5637, whereas the promyelocytic leukemia cell line HL60 was positive for GM-CSF binding. Time course experiments showed maximum binding of GM-CSF in granulocytes after an incubation period of 60 min and a decrease in binding after an incubation period of 2 h. In parallel, we found a maximum biological signal when granulocytes were preincubated for 90 min with GM-CSF, and a decrease after an incubation time of 120 min. Preincubation of the cells with rH. GM-CSF induced an enhancement of the production of activated oxygen species by the cells in response to PMA.

Quantitative considerations supporting the irrelevance of circulating serum CEA for the immunoscintigraphic visualization of CEA expressing carcinomas.

Starting from the phenomenon that the amount of circulating CEA in patients' sera did not significantly influence immunoscintigraphic visualization of CEA expressing tumors, we built up an in vitro model to explain this phenomenon. Blocking experiments in this model system showed that the CEA specific MAbs BW 431/26 and BW 431/31 could not be inhibited in their binding to cell associated CEA, if they were preincubated with a 20 molar excess of serum CEA. In contrast, the CEA-NCA cross reactive MAbs could be inhibited in their binding to tumor associated CEA under identical conditions. These data combined with western blotting analysis of patients' sera and affinity constant determinations argue that conformational changes in serum CEA cause a decreased affinity of the CEA specific MAbs to serum CEA allowing a preferential binding to tumor associated CEA.

A monoclonal antibody with binding and inhibiting activity towards human pancreatic carcinoma cells. I. Immunohistological and immunochemical characterization of a murine monoclonal antibody selecting for well differentiated adenocarcinomas of the pancreas.

The murine monoclonal antibody (MAb) BW 494 was characterized in relation to its tissue specificity, the epitope recognized, in vitro and in vivo radiolocalization and its potential to mediate antibody dependent cellular cytotoxicity (ADCC) and complement mediated cytolysis (CMC). The MAb defined carbohydrate epitope located on a greater than 200 k daltons glycoprotein was mainly expressed on the majority of well differentiated adenocarcinomas of the pancreas. Furthermore, the epitope is accessible to MAb BW 494 in vivo, allowing an enrichment of radioactive antibody at the tumor site in nude mice. Additionally, MAb BW 494 is able to use human peripheral blood lymphocytes as effector cells for ADCC reactions against appropriate tumor target cells in vitro. In contrast, the antibody does not mediate human or rabbit CMC.

Characterization of an individual specific small cell lung carcinoma associated antigen.

The specificity of the murine monoclonal antibody (moab) BW 278/97 of IgG1 isotype is determined on the cellular and tissue level. Additionally, the antigen carrying the epitope recognized by moab BW 278/97 is defined as a 72 KD protein, uniquely expressed on a single small cell lung carcinoma.

Immunohistochemical localization and molecular characteristics of three monoclonal antibody-defined epitopes detectable on carcinoembryonic antigen (CEA).

Three murine monoclonal antibodies (MAbs) reactive to different epitopes on CEA were selected according to their ability to bind to various human tissue sections. The most selective MAb, BW 431/31, bound to the majority of colon carcinomas but only faintly to normal colon mucosa. In addition to the tissues stained by MAb BW 431/31, MAb BW 250/183 reacted with granulocytes, colon mucosa and faintly with pancreatic ducts. The third MAb, BW 374/14, reacted with granulocytes, colon mucosa, strongly with pancreatic ducts and with alveolar and bronchial epithelium. The antigenic determinants recognized by the 3 MAbs in human tissue sections were resistant to formaldehyde fixation and paraffin embedding as well as to periodic acid oxidation and neuraminidase treatment. The last two treatments suggest that the epitopes are protein in nature. Using MAb affinity chromatography, 3 antigen preparations were isolated from a human colon carcinoma xenograft with an approximate molecular weight of 180 kd. These preparations were shown to bear the epitopes from each of the MAbs and from a polyclonal antiserum specific for purified CEA. Furthermore, the ability of MAb BW 431/31 to localize its antigenic determinant in vivo on a human colon carcinoma xenograft is evaluated and its possible application in the patient is suggested.

[Do pregnancy proteins have prospective significance? (SP-1, HPL and PP-5)]. / Haben Schwangerschaftsproteine eine prospektive Aussagekraft? (SP-1, HPL und PP-5).

Concentrations of pregnancy proteins were determined in blood of 219 pregnant women in 20th week of gestation. Pregnancy-specific beta 1-glycoprotein SP-1, human placental lactogen (hPL) and placental protein 5 (PP-5) were tested. In contrast with results of other authors there were no differences between the normal group of patients and those with complications during gestation, such as prematurity and foetal retardation. Thus measurement of blood concentration of proteins mentioned above in 20th week is not of prognostic relevance for gestation.

Molecular characteristics of two lung carcinoma cell-line associated membrane antigens.

The molecular characteristics of the antigens detected by the moab BW 181/26 and BW 166/6 are described. The 55 KD molecule defined by BW 181/26 is strongly attached to the plasma membrane and is not secreted, whereas the 140 KD (96 KD) and 120 KD (61 KD) molecules recognized by BW 166/6 are loosely associated to the cell membrane and secreted into the tissue culture medium. The last two antigens might be used as markers for the early detection of certain lung carcinomas, whereas the 55 KD membrane associated antigen could be a target for immunotoxins used in immunotherapy of cancer.

Studies on the mechanisms of action of the immunomodulator Bestatin in various screening test systems.

The effects of Bestatin, a low molecular weight metabolite of Streptomyces olivoreticuli on the human and mouse/rat immune system, have been studied in detail. To describe the activity of the immunomodulating dipeptide, it has been tested in vitro, ex vivo and in vivo in various experimental models. Bestatin simultaneously applied with selected antigens to mice was able to enhance the DTH response against a challenge injection of the respective antigen given into the footpad. Serum antibody levels against those antigens were uneffected. However, an increase of PFC could be found in those mice given high doses of Bestatin. On natural killer cell activity against Yac-1 tumor cells the dipeptide had no effect in low responder (DBA2/J) mice. In high responder mice (CBA/JCr), however, a significant increase of NK cell activity of spleen cells could be found, when the drug was given on day 0 or on days 0 to 3 and the test was performed on day 4. Bestatin had no effect on the generation of allogeneic cytotoxic T-lymphocytes in vivo or in vitro and even a suppressive effect on the induction of syngeneic antitumor CTL. Contrary to this suppressive effect, Bestatin increases in the popliteal lymph node assay the weights in a dose-dependent way. When mouse macrophages or human monocytes were either incubated in vitro with Bestatin or mice were treated with the dipeptide parenterally or orally and the macrophages from those mice were investigated, Bestatin induced in vitro and in vivo a dose-dependent increase in pinocytic uptake of radioactive colloidal gold. Also the oxidative metabolism was dose-dependently augmented as measured by chemiluminescence. Bestatin modulates the macrophage mediated cytotoxicity. In vitro or in vivo activated mononuclear phagocytes exhibited a dose-dependent increase in cytotoxic activity for several tumor target cells. A minimum ratio of 50:1 effector to target cells was necessary for this cytotoxic effect. A similar degree of activation was observed in macrophages from athymic nu/nu-mice or from endotoxin resistant C3H/HeJ-mice. Other parameters of macrophage activation were determined by measuring secretion of lysosomal enzymes and liberation of prostaglandins. Bestatin interacts with macrophages in vivo and in vitro by increasing their secretory activity of acid hydrolases (beta-glucuronidase, beta-galactosidase, and N-acetyl-beta-D-glucosaminidase). This release was dose- and time-dependent and not associated with any sign of cell death. Another class of mediators produced by macrophages after stimulation with Bestatin were the prostaglandins E2 and F2a.(ABSTRACT TRUNCATED AT 400 WORDS)

The immunocytochemical location of two membrane-associated placental tissue proteins in human and cynomolgus monkey placentae.

Using the PAP technique, the location of two new membrane-associated placental tissue proteins, MP1 and PP4 was studied in the placenta, its membranes, decidua and umbilical cord of human and cynomolgus monkeys. The results were the same throughout pregnancy. MP1 was located in the syncytiotrophoblast and trophoblastic cells of the reflected chorion. Other placental tissue components (cytotrophoblast, amnion, decidua, and umbilical cord) were negative. At present, MP1 appears to be specific for trophoblast. PP4 was located in the syncytiotrophoblast. Furthermore clear positive staining for PP4 was found in the villous cytotrophoblast, reflected and basal chorion, amnion, umbilical cord and decidua. In addition, PP4 was positive in some granulocyte-like blood cells in the intervillous space. Immunocytochemically, the most positive staining for both proteins was observed in the membrane of villous syncytiotrophoblastic cells. The findings in the placenta of cynomolgus monkeys were similar to those in women. The monkey could, thus, serve as a model for the investigation of these new membrane-associated placental tissue proteins.

S-sulfonation: a reversible chemical modification of human immunoglobulins permitting intravenous application. I. Physicochemical and binding properties of S-sulfonated and reconstituted IgG.

S-sulfonation represents a reversible chemical modification of disulfide bonds by which under the special conditions chosen only about 2.2 cystine units per IgG molecule are cleaved. Physicochemical and functional evidence for reconstitution is presented. Molecules reconstituted in vitro or in vivo regain, within a few hours, a reactivity (antigen binding, immunoprecipitation, Clq-mediated cross-linking of immune complexes) comparable to equimolar control preparations.

Concentration of placental protein 10 (PP10) in maternal serum and amniotic fluid throughout normal gestation and in pregnancy complicated by fetal growth retardation.

PP10, a new placental glycoprotein, was studied by a specific and sensitive double-antibody radioimmunoassay in maternal serum and other body fluids throughout pregnancy. The mean value of serum PP10 in healthy nonpregnant individuals was approximately 10 microU/l. During normal pregnancy it rose to 3,500 microU/l. The rate of rise was obtained from 78 normal pregnancies with 279 single assay values from weeks 6-40. The shape of the curve resembled that for other placental proteins (HPL, SP1). PP10 levels in amniotic fluid were measured in 145 samples from weeks 13-55 of normal pregnancies and at term. The mean concentration was 500 microU/l until week 18 and then rose slowly. Cord blood contained only trace amounts. PP10 was not found in maternal urine. The concentration in maternal serum and amniotic fluid was higher in twin pregnancies than in singleton pregnancies. In 46 cases with low birth weights the PP10 levels in maternal serum were significantly lower than normal. Simultaneous measurements of PP10 and E3, HPL and SP1 were made in 17 individual follow-up's. PP10 was comparable with E3 and appeared to be better than HPL and SP1 in predicting intrauterine fetal growth retardation.

Serum levels of placental protein 10 (PP10) in women with breast cancer and genital carcinoma and in healthy male and female subjects.

PP10, a recently characterized glycoprotein from human placenta, was studied using a specific double-antibody radioimmunoassay in the serum of about 100 volunteers and 200 cancer patients. Elevated levels (greater than 20 nU/ml) were found in 87% of patients with primary breast cancer, in 100% of those with primary genital tumours and in 78% of patients with recurrent disease. PP10 was also measured in tumour extracts and in some patients with benign tumours. The serum concentration decreased within a few weeks after removal of the tumour. There were no significant correlations of the PP10 level with age, tumour size, histological grading or lymph node involvement. Sequential determinations of PP10 during cytostatic therapy sometimes showed rising levels accompany the development of metastases. PP10 can be regarded as a tumour associated protein and a tumour marker in gynaecological practice.

Radioimmunoassay of SP1 (pregnancy-specific beta1-glycoprotein) in maternal blood and in amniotic fluid normal and pathologic pregnancies.

Sp1, the pregnancy-specific beta 1-glycoprotein, was studied in normal and pathologic pregnancies. We developed a highly specific and sensitive double-antibody-radioimmunoassay by radioiodination of purified placental SP1. This RIA allowed the estimation of SP1 concentrations as low as 2 ng/ml. In a collective of 227 women with normal pregnancies we established the normal distribution curve in maternal plasma from the fifth week of gestation to term. The median value rose steadily from 3 microgram/ml in the 8th week to 140 microgram/ml in the 36th week when a plateau was formed. In more than 400 patients with pregnancies complicated by a variety of pathologic disorders the SP1 levels were controlled by either single assays or serial estimations throughout pregnancy and were compared with the normal distribution range. SP1 was also determined in about 200 samples of amniotic fluid gained by amniocentesis and during parturition of normal pregnant women from the 13th gestational week until term. The normal range was established up to the 20th w.o.p. The concentrations rose from below 0.2 microgram/ml in early pregnancy to 3 microgram/ml and generally amounted to approximately 1% of the respective serum value. Pathologic cases with diverse chromosomal anomalies, Rh-incompatibility, anencephaly, hydramnios and other abnormal conditions were examined. From these only twin-pregnancies with slightly elevated levels and cases with fetal trisomies with reduced SP1 concentrations showed aberrations from the normal distribution. The estimation of serum concentrations in mothers with diabetes or Rh-incompatibility were not significantly different from the normal collective. In diabetes a characteristic course of the follow-up curves was observed. Abortion in early pregnancy was frequently but not always indicated by reduced SP1 values. Threatened abortion with subsequent continuation of pregnancy exhibited SP1 values scattered within the normal range. Since the radioimmunological determination of SP1 is possible in the early stage of gestation (from week 8) it may serve as a useful tool for prediction at times when the determination of placental lactogen is not yet possible. In pregnancies with "small-for-date babies" the correlation between SP1 in maternal plasma and fetal growth retardation was reflected in a pronounced tendency to low SP1 levels. Serial determinations of SP1 in the serum of women with EPH-gestosis were compared with the corresponding HPL determinations and showed the equality of SP1 concerning the assessment of the placental function.

[Factor VIII concentrate, highly purified and heated in solution (author's transl)]. / Faktor VIII-Konzentrat, hochgereinigt und in Lösung erhitzt

A process is described to produce a highly purified factor VIII concentrate heated in solution. Pooled cryoprecipitate from citrated plasma is adsorbed on aluminum hydroxide gel. The fibrinogen is removed by heat denaturation in the presence of glycine; factor VIII is precipitated with sodium chloride from the supernatant. The precipitate is dissolved in a saccharose/glycine solution and heated at 60 degrees C for 10 h. The factor VIII is then separated by further precipitation with sodium chloride, the precipitate dissolved, dialysed and sterilized by filtration. The factor VIII concentrate contains approximately 6 units F VIII:C per mg protein. the ratio of F VIII R:Ag/F VIII:C is 3. The product is free from coagulable protein and gamma-globulins. The efficacy of the heating step in the reduction of the hepatitis B-infectious titre was proved in chimpanzees. For this purpose, hepatitis B virus was added to the pooled cryoprecipitate.