Peptide immunogen mimicry of a protein-specific structural epitope on human choriogonadotropin

It is a challenge to construct synthetic immunogens that elicit antibodies (Abs) both directed to conformational epitopes and specific for a complex protein like human choriogonadotropin (hCG). A monoclonal antibody specific for hCG bound to regions around Lys45 of the alpha subunit (hCG alpha) and Asp112 of the beta subunit (hCG beta). A peptide comprising residues 46 to 55 of hCG alpha and residues 106 to 116 of hCG beta elicited Abs in rabbits that were directed to a discontinuous epitope and were specific for hCG. These Abs inhibited the binding of hCG to its receptor. Thus, a synthetic immunogen can mimic a conformational-specific epitope and can be useful for vaccine development.

Structural probing of human lutropin using antibodies raised against synthetic peptides constructed by classical and multiple antigen peptide system approaches

Antibodies were elicited against a synthetic peptide which encompassed two different regions of the human lutropin beta-subunit (hLH-beta). These antibodies were raised against either the peptide which was assembled using a conventional approach and conjugated to the tetanus toxoid, or with the peptide assembled using the multiple antigen peptide system approach. Automated simultaneous synthesis of the two forms of the immunizing peptide was successfully achieved. Animal injected with the peptide conjugated to tetanus toxoid produced high titers of antibodies to the synthetic peptide, but did not bind to the native hLH-beta subunit. In contrast, antisera induced by the peptide in its MAP form displayed reactivity with both the peptide and the native hLH-beta subunit; these latter antisera appeared to preferentially recognize the beta 47-55 portion of the molecule and were able to bind to the beta-subunit of human choriogonadotropin. Present results demonstrate that the beta 47-55 region is accessible to antibody binding and appears to be located at the surface of both hLH-beta and hLH. Moreover, this study confirms that the MAP approach provides a chemically unambiguous method for obtaining antibodies of predetermined specificity, capable of recognizing cognate sequences of various native proteins.

Occurrence of fragmentation of free and combined forms of the beta-subunit of human chorionic gonadotropin

In an attempt to further study various fragments of free and combined forms of hCG beta present in biological fluids, we performed one- and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis, followed by Western immunoblotting using antipeptide antibodies directed to the hCG beta-(111-116) portion (monoclonal antibody FB12) antiserum to the hCG beta(8-16) portion or antiserum which was specific for fragments ending at residue 47. Results observed in a crude preparation of urinary hCG demonstrated that in addition to the carboxyl-terminal part of the reduced hCG beta nicked subunit (beta NS) [hCG beta-(48-145)], three other fragments of mol wt 18,000 (F1), 16,500 (F2), and 12,000 (F3) were detectable after cleavage of disulfide bonds. Both the immunoreactivity pattern and peptide sequencing revealed that the F1 fragment was constituted of the hCG beta-(1-47) sequence, whereas the F2 fragment comprised the 6-47 portion. We then studied the beta NS in urine from either pregnant women or four patients with choriocarcinomas. Results showed that both hCG and the free beta-subunit contained beta NS. Furthermore, free hCG beta present in those urine samples appeared to be extensively, if not totally, nicked. Results observed in urine were confirmed using separation of hCG from its beta-subunit by a two-step chromatography procedure, identification of hCG and hCG beta immunoreactive peaks by specific monoclonal immunoradiometric assay, and analysis of resulting preparations by one-dimensional electrophoresis under reducing conditions, followed by Western immunoblotting with FB12. This latter protocol was also used to investigate the presence of beta NS in sera of four patients with choriocarcinoma tumors. In those sera, hCG appeared to be nicked. This study demonstrates that the beta-subunit of hCG is modified by multiple fragmentations.

Peptide mapping of intersubunit and receptor interactions of human choriogonadotropin

Seven peptides covering the entire sequence of human choriogonadotropin (hCG) alpha-subunit, eight peptides covering the hCG beta-subunit sequence and two peptides, one of human beta-lutropin and one of beta-thyrotropin were synthesized. We checked their ability to prevent reassociation between hCG alpha- and beta-subunits and between hCG and its receptor. Only the alpha 1-22, alpha 59-92 and beta 1-16 peptides inhibited the reassociation between the alpha- and beta-subunits of hCG with an ED50 of respectively 2 mM, 2 mM and 4 mM. Using porcine Leydig cells in primary culture, we showed that alpha 33-59, alpha 41-59 and beta 1-16 peptides decreased both the specific binding to the cell surface and the internalization of [125I]hCG and [125I]porcine LH with ED50 of 0.3, 0.1 and 0.5 mM, respectively. From these results, the following minimal area may be assigned, (i) to the alpha-beta interaction: alpha 5-16, alpha 52-72 (or alpha 59-70) and beta 8-16, and (ii) to the hormone-receptor association: alpha 41-45 and beta 8-16.

[Value of biological markers in the diagnosis and monitoring of cystadenocarcinoma]

Among the various antigens described as biological markers of ovarian cancer, only one, CA 125, is of value in clinical practice. CA 125 is not specific to epithelial ovarian cancer, but it is associated with this tumour. CA 125 assays are useless in the early detection of tumours in asymptomatic patients, but they are helpful to monitor the clinical course of treated cystadenocarcinoma of the ovary since a rise in CA 125 level may be observed several months before clinical or radiological evidence of ovarian malignancy is obtained. Finally, CA 125 determination is important before second-look laparotomy.

Lutropin receptor and thyrotropin receptor share a common epitope

In the present work, using an immunological approach, we have investigated the existence of common epitopes between two receptors of the glycoprotein hormone family, lutropin (LH) and thyrotropin (TSH) receptors. We have immunized high responder mice with purified porcine LH receptors obtained by successive affinity chromatographies on agarose-human chorionic gonadotropin (hCG) gels. From one fusion of splenocytes with the murine myeloma NSC1, secreting hybridomas were tested for their anti-LH receptor specificities. During sequential selection for this activity including direct recognition of the purified LH receptors in dot-blot assays and displacement experiments of 125I-pLH and 125I-hCG binding to different sources of receptors, we performed a parallel investigation of their anti-porcine TSH receptor activities. Purified immunoglobulins from two of them showed a TSH-like activity on the iodide metabolism of porcine thyroid cell, this activity being related to the phosphoinositide breakdown pathway; moreover, these antibodies obtained after immunization with porcine LH receptors were able to immunopurify human TSH receptors. The double selection process led us to characterize three groups of immunoglobulins: exclusive specificities for lutropin receptors or thyrotropin receptors and cross-reactive specificities. Our results demonstrate the possibility of sequence homologies at the protein and the gene levels between the receptors for the glycoprotein hormone family supporting the hypothesis of a common origin in evolution.

In vivo toxicity of cisplatin and carboplatin on the Leydig cell function and effect of the human choriogonadotropin

In order to characterize the respective toxicity of cisplatin (CDDP) and carboplatin (CBDCA) on the male reproductive system, we have investigated their in vivo effects on the steroidogenesis function of rat leydig cells. Animals were treated at the respective LD50 of platin compounds, and we analyzed plasmatic testosterone level, microsomal cytochrome P-450 and platinum concentrations in the testis. CDDP induces a dramatic change in both the testosterone level and the microsomal cytochrome P-450 concentration. In contrast, CBDCA was found to be less toxic than CDDP, probably due to its different accumulation at the testis level. We also investigated the potential action of human chorionic gonadotropin which allows a full restoration of the steroidogenesis function.

Monoclonal antibodies directed to human and equine chorionic gonadotropins as probes for the topographic analysis of epitopes on the human alpha-subunit

To improve our knowledge of the structural features of the alpha-subunit of hCG we have studied the antigenic site recognized by monoclonal antibody (MAb) ECG01 raised against equine CG (eCG) which binds to hormones and alpha-subunits from human and equine species. We have also delineated regions of hCG alpha comprising the epitope recognized by HT13 which was raised against hCG and binds to hCG and hCG alpha. To define the residues involved in the antigenic sites recognized by ECG01 and HT13, we have studied the reactivities of these two MAbs with native or chemically modified LH and CG with subunits from equine, human, or ovine (o) species or with synthetic peptides analogous to various portions of hCG alpha. We have also compared these reactivities with those displayed by MAbs AHT20 and FA 36, whose epitopes have been previously described; anti-hCG alpha MAb AHT20 is specific for the free alpha-subunits of various species and recognizes residues localized to the 36-41 region of hCG alpha, whereas antipeptide MAb FA36 binds to the 87-92 carboxyl-terminal part of hCG alpha. Our results show that the epitopes of HT13 and ECG01 are 1) probably discontinuous, as these MAbs did not bind to the reduced and S-carboxymethylated hCG alpha; and 2) constituted by residues borne on the 1-35 and 52-86 sequences, as they do recognize the hCG alpha core missing the 36-51 portion, yet do not recognize hCG alpha-(87-92) region recognized by FA36. The comparative studies performed with specific two-site immunoradiometric assays to determine the interspecies cross-reactivities of the MAbs allow us hypothetical assignment of residues on the primary structure of hCG alpha. The antigenic site recognized by ECG01 might include two to six amino acids, four of these residues being located at inverted places compared to those of oLH alpha (Asp6/Gly22 and Arg67/Lys75). These residues present important charged functional groups highly conserved among evolutionarily related variants, and it is likely that they are located on the surface of both the intact hormone and its alpha-subunit. Three peptidic portions of hCG alpha, 16-17, 64-66, and 73-76, respectively, might be involved in the epitope recognized by HT13, although we could not rule out the possibility that other residues were also involved in the antigenic site. These observations allow us to identify several residues as potentially constituting the epitopes recognized by two MAbs on both hCG and hCG alpha.

Characterization of a cleavage product in the human choriogonadotropin beta-subunit

The various molecular forms of human chorionic gonadotropin present in a crude preparation of urine from pregnant women were analyzed by two-dimensional gel electrophoresis and immunoblotting with monoclonal antibodies directed to synthetic peptides corresponding to the carboxyl-terminal part of either the alpha or beta-subunit. Under reducing conditions, immunoblotting with antibodies directed to the beta-subunit revealed the presence of a low-molecular-weight material of 22 kDa. This molecular form had large heterogeneity, as analyzed by isoelectrofocusing; it was immunoreactive with antibodies directed to the 111-145 region. Using microsequencing techniques, we found that the fragment had a NH2 terminal portion corresponding to the sequence of the beta-subunit appearing from residue 48. Thus, the 22-kDa fragment comprises the 48-145 portion of the beta-subunit and is probably a cleavage product of the native protein with intrachain nicking.

Antigenic determinants on human choriogonadotropin alpha-subunit. I. Characterization of topographic sites recognized by monoclonal antibodies

Immunochemical studies were designed to localize antigenic regions recognized by two monoclonal antibodies directed against the alpha-subunit of human choriogonadotropin (hCG-alpha) and to provide information on the three-dimensional structure of hCG and its alpha-subunit. Monoclonal antibody HT13 bound to a region accessible on both hCG and the free alpha-subunit, whereas monoclonal antibody AHT20 recognized a site localized only on the free alpha-subunit. By studying the cross-reactivity of these antibodies to homologous proteins, we found that antibody HT13 did not bind to equine or ovine lutropin, whereas AHT20 was capable of binding to both subunits. This observation suggests that AHT20 recognized a structurally related antigenic determinant on alpha-subunits of different species. To delineate the portions of hCG-alpha contributing to the antigenic determinants of AHT20 and HT13, we performed competitive inhibition assays using reduced and carboxymethylated hCG-alpha, deglycosylated hCG-alpha, hCG-alpha minus the 5 COOH-terminal residues (hCG-alpha core 1), or disulfide-bridged peptides comprising residues 1-35 and 52-91 of hCG-alpha (hCG-alpha core 2). Reduced and carboxymethylated hCG-alpha did not inhibit the binding of 125I-labeled hCG-alpha to both antibodies, whereas deglycosylated hCG-alpha was as active as hCG-alpha, suggesting that antigenic determinants of both antibodies are mainly discontinuous and do not reside on the oligosacharide part of the alpha-subunit. hCG-alpha core 1 had the same capacity as intact hCG-alpha to inhibit the binding of 125I-hCG-alpha to both antibodies, indicating that the 5 COOH-terminal residues of hCG-alpha do not participate in the antigenic determinants. hCG-alpha core 1 was as potent as hCG-alpha in inhibition experiments performed with HT13, whereas, in striking contrast, hCG-alpha core 2 did not compete with 125I-hCG-alpha for binding to AHT20, suggesting that the peptides released after proteolysis of the alpha-subunit by trypsin participate in the epitope of AHT20 and are not included in the antigenic determinant of HT13. In an attempt to elucidate the amino acid residues constituting the antigenic sites of HT13 and AHT20, hapten inhibition experiments were carried out using as competitive inhibitors five different synthetic peptides spanning the primary structure of hCG-alpha. None of these peptides inhibited the binding of 125I-hCG-alpha to HT13. In contrast, two peptides analogous to regions 23-43 and 33-59 of hCG-alpha exhibited significant potency in competing with 125I-hCG-alpha for binding to AHT20.(ABSTRACT TRUNCATED AT 400 WORDS)

Antigenic determinants on human choriogonadotropin alpha-subunit. II. Immunochemical mapping by a monoclonal antipeptide antibody

In order to study antigenic site(s) present in the carboxyl-terminal part of the alpha-subunit of human choriogonadotropin (hCG-alpha), we attempted to produce site-specific antibodies directed against a 34-residue synthetic peptide analogous to region 59-92 of hCG-alpha. From a fusion experiment performed with a mouse injected with hCG-alpha-(59-92)-peptide conjugated to tetanus toxoid as immunogen, we selected a monoclonal antipeptide antibody (designated FA36) which has high binding activity for 125I-hCG-alpha but not for 125I-hCG in a radioimmunoassay. This antibody is of the IgG1 subclass and displays an affinity constant for 125I-hCG-alpha of 3.1 x 10(8) M-1. Hapten inhibition experiments performed by either radioimmunoassay or enzyme-linked immunosorbent assay with synthetic peptides spanning different portions of the region (59-92) demonstrated that the binding site of FA36 resides on (minimally) the six COOH-terminal amino acids of hCG-alpha, namely Cys-Tyr-Tyr-His-Lys-Ser, and that FA36 binds preferentially to peptides containing a carboxyl group on the COOH-terminal residue. Monoclonal immunoradiometric assays were established to determine the location of antigenic regions recognized by FA36, by antibody AHT20 (which binds only to hCG-alpha), and by antibody HT13 (which binds to both hCG and hCG-alpha). FA36 has the capacity to bind to hCG-alpha bound to either AHT20 or HT13, demonstrating that both AHT20 and HT13 antibodies are directed against antigenic regions distinct from the epitope of FA36. Monoclonal immunoradiometric assays were also carried out to study the binding of FA36 to hCG, the ovine and equine lutropin alpha-subunit, or hCG-alpha minus the 5 COOH-terminal residues (hCG-alpha core). Whereas significant binding of 125I-FA36 was observed with the ovine lutropin alpha-subunit, no binding was found with the equine lutropin alpha-subunit. As expected, FA36 did not bind to hCG-alpha core. Binding was also not detected with hCG, confirming that FA36 is specific for free hCG-alpha and that the COOH-terminal part of hCG-alpha is either weakly or (more likely) not at all accessible in the alpha/beta-dimer for antibody binding. Finally, immunoblots performed on hCG-alpha-(59-62)-peptide and various denatured alpha-subunits indicated that, with the exception of the equine lutropin alpha-subunit, FA36 detected various denatured alpha-subunits and particularly the alpha-subunit of carp gonadotropin-thyrotropin. This latter observation suggests a high degree of homology between the COOH-terminal regions of the alpha-subunits of fish gonadotropin and analogous mammalian hormones.(ABSTRACT TRUNCATED AT 400 WORDS)

Solubilization and purification of the lutropin (LH) receptor from porcine testes

The LH receptor was solubilized from porcine testis homogenates by different detergents. Non-ionic detergents appeared to be the best ones regarding solubilization yield and recovery of active receptor after elution from hCG affinity gels. However, the final yield was not greater than 1-2% of the starting receptor activity. We also investigated the effect of added phospholipids (75% phosphatidylcholine + 25% phosphatidylethanolamine) on the yield of the overall purification process. It was shown that the best p value [i.e. the ratio of (detergent concentration - critical micellar concentration) to phospholipids] upon solubilization was congruent to 1.1 for a non-ionic detergent such as Nonidet P-40, while a higher p value was better upon elution. The stability of the solubilized receptor versus pH and SDS has been studied. The receptor exhibited two pKa's of denaturation congruent to 3.8 and 11.1, while the [125I]hCG-receptor complex dissociated with a pKa congruent to 3.8 and 10.3 SDS concentrations as low as 0.05% denatured rapidly and apparently, irreversibly, the solubilized LH receptor. The stability of different affinity gels was checked and it was found that the best yield for receptor elution (congruent to 10%) was obtained with an immunoaffinity anti-hCG support. The obtention of two monoclonal antibodies is mentioned, as well as their competition with the binding of [125I]pLH to testis homogenates.

Electronic video endoscopy: preliminary results of imaging modification

This study represents a preliminary trial of the quantification of colorimetric modification of the esophageal mucosa, permitting the opening up of a video-electronic and computer classification of lesions of esophagitis.

Immunochemical mapping of a specific domain on human choriogonadotropin using anti-protein and anti-peptide monoclonal antibodies

In an attempt to localize topographic domains specific to native human chorionic gonadotropin (hCG), we studied the discontinuous antigenic regions recognized by a monoclonal anti-hCG antibody designated as C8 which binds only to hCG and does not cross-react with either the free hCG-alpha and hCG-beta subunits or other glycoprotein hormones. Using two-site monoclonal immunoradiometric assays (M-IRMAs), we found that C8 antibody and an anti-peptide antibody (FB12) directed to residues 110-116 of hCG-beta did not bind simultaneously to hCG. This observation suggested that C8 binds to residues of hCG-beta included either in the antibody-binding region of FB12 or in close proximity to amino acids 110-116. To further delineate the regions of hCG-beta recognized by C8, we carried out hapten inhibition experiments with synthetic peptides corresponding to various regions of hCG-beta. The peptide corresponding to residues 109-122 and subpeptides (111-122 or 112-122) inhibited the binding of 125I-hCG to C8, whereas weak inhibition was observed with subpeptide 113-122. By studying the binding of C8 to the 1-112 disulfide-bonded part of hCG-beta (hCG-beta core) recombined with hCG-alpha, we were able to confirm that C8 binds to a region including or near to Asp112. M-IRMAs showed that C8 does not bind to the recombinant molecule lacking residues 113-145 of hCG. Taken together, these results indicate that a limited number of residues located on hCG-beta near to Asp112, and most likely the sequence Asp111-Asp112-Pro113, are included in the discontinuous antigenic region recognized by C8. We then attempted to localize residues of hCG-alpha that constitute another part of the determinant which bound to C8. Six synthetic peptides corresponding to various regions of hCG-alpha did not inhibit binding of 125I-hCG to C8. In contrast, M-IRMAs demonstrated that C8 is capable of binding recombinant products composed of the hCG-beta subunit and the alpha subunits from human, equine, and porcine species. These results indicate that C8 recognizes a region of the alpha subunit highly conserved in these three species. Finally, we determined that the discontinuous regions recognized by C8 are partially accessible on the CG/LH-receptor complex.

Topographic antigenic determinants recognized by monoclonal antibodies on human choriogonadotropin beta-subunit

We describe a first attempt to study the antibody-combining sites recognized by monoclonal antibodies raised against the beta-subunit of human choriogonadotropin (hCG). Two groups of antibodies were first defined by their ability to recognize only the free beta-subunit or the free and combined subunit. Antibodies FBT-11 and FBT-11-L bind only to hCG beta-subunit but not to hCG, whereas antibodies FBT-10 and D1E8 bind to both the beta-subunit and the hormone. In both cases, the antigenic determinants were localized to the core of the protein (residues 1-112), indicating the weak immunogenicity of the specific carboxyl-terminal extension of hCG-beta. Nine synthetic peptides spanning different regions of hCG-beta and lutropin-beta were assessed for their capacity to inhibit antibody binding. A synthetic peptide inclusive of the NH2-terminal region (residues 1-7) of the hCG beta-subunit was found to inhibit binding to the radiolabeled subunit of a monoclonal antibody specific for free hCG-beta (FBT-11). Further delineation of the antigenic site recognized by this antibody provided evidence for the involvement of fragment 82-92. Moreover, monoclonal antibody FBT-11 inhibited the recombination of hCG-beta to hCG-alpha, indicating that its antigenic determinant might be located nearby or in the hCG-beta portion interacting with the alpha-subunit. Binding of monoclonal antibody FBT-10, corresponding to the second antigenic determinant, was weakly inhibited by fragment 82-105 and did not impair the recombination of the hCG beta-subunit to the hCG alpha-subunit. Its combining site appeared to be located in a region of the intact native choriogonadotropin present at the surface of the hormone-receptor complex.

The immune response to a synthetic peptide analogous to the 109-145 beta hCG carboxyl-terminus is directed against two major and two minor regions

The immune response to a 37-amino acid synthetic peptide analogous to the carboxyl-terminal part (109-145) of the human chorionic gonadotropin beta subunit (beta hCG) was studied with monoclonal antibodies selected from 31 cell fusion experiments. Analysis of the immunogenic determinants borne on the synthetic peptide (CTP) showed a prevailing response to two immunodominant regions. The first was located on the 110-116 amino acid sequence of the CTP which is also the most hydrophilic region: 50% of anti-CTP antibodies selected for their high binding to 125I beta hCG were directed to this sequence. A second immunodominant portion was recognized by four antibodies, and comprised amino acids 134 to 139, representing a highly O-glycosylated region on the native protein. Moreover, a unique antibody designated FB13 bound to a region located on the last seven amino acids (139-145) of beta hCG. Finally, a hypothetical conformational determinant was recognized by antibody FB02 within the 121-145 region. Thus, the immune response to CTP was directed against two major and two minor regions. These antigenic determinants were demonstrated to be accessible for antibody binding on both the hCG molecule and its beta subunit. Localization of these epitopes suggests a relationship between the hydrophilicity and the immunological potency of different CTP regions.

Photoregulation process of sorghum leaf phosphoenolpyruvate carboxylase: study with monoclonal antibodies

Monoclonal antibodies were produced against the G isozyme subunit of PEP carboxylase (PEPC) from Sorghum leaves by the hybridoma technique. More than 400 antibodies-producing hybridomas to PEPC were produced from the fusion of spleen cells from immunized mice with NS1 myeloma cells. By using an ELISA, three hybridomas (91-G, 83-G, 49-EG) were selected. Monoclonal antibodies were subsequently characterized in a Western experiment; Mabs 83-G and 91-G were found to be highly specific to the G isozyme whereas Mab 49-EG recognized both forms (E and G isozymes) of the enzyme. Addition of Mabs to the enzyme preparation did not modify its catalytic activity nor its activation by glycine. Use of these probes provided direct and definite evidence of the specific enhancing effect of light on the G form and on its corresponding mRNA.

Elevation of CA 125 in patients with benign and malignant ascites

The presence of CA 125, an ovarian cancer-associated antigen, was assessed in serum and ascites from patients with ovarian cancer (n = 47), hepatocellular carcinoma (n = 21), and liver cirrhosis (n = 40). Abnormal levels of serum CA 125 were observed in 49% of ovarian cancer patients, and in 89% of these same patients with ascites. In all cases of cirrhosis or hepatocellular carcinoma with ascites, CA 125 levels were above 35 U/ml. The specificity and sensitivity of CA 125 measurement for detecting ascites in chronic liver diseases were 73% and 100%, respectively. Furthermore, the CA 125 level was always higher in ascites than in serum. The authors conclude that CA 125 is a nonspecific marker of ascites. This result must be considered in the interpretation of CA 125 elevation in patients with ovarian cancer. Moreover, CA 125 may be of value in the diagnosis and monitoring of peritoneal diseases.

Elevation of CA 125 in patients with benign and malignant ascites

The presence of CA 125, an ovarian cancer-associated antigen, was assessed in serum and ascites from patients with ovarian cancer (n = 47), hepatocellular carcinoma (n = 21), and liver cirrhosis (n = 40). Abnormal levels of serum CA 125 were observed in 49% of ovarian cancer patients, and in 89% of these same patients with ascites. In all cases of cirrhosis or hepatocellular carcinoma with ascites, CA 125 levels were above 35 U/ml. The specificity and sensitivity of CA 125 measurement for detecting ascites in chronic liver diseases were 73% and 100%, respectively. Furthermore, the CA 125 level was always higher in ascites than in serum. The authors conclude that CA 125 is a nonspecific marker of ascites. This result must be considered in the interpretation of CA 125 elevation in patients with ovarian cancer. Moreover, CA 125 may be of value in the diagnosis and monitoring of peritoneal diseases.

Sensitive and specific assay for human chorionic gonadotropin (hCG) based on anti-peptide and anti-hCG monoclonal antibodies: construction and clinical implications

We developed a highly sensitive and specific assay for hCG using monoclonal antibodies (Mabs) directed against a 37-amino acid synthetic polypeptide analogous to the carboxyl-terminus (CTP) of beta hCG. Five antibodies that varied by either their affinity for beta hCG or their specificity for epitopes on CTP were investigated. To measure hormone levels, we used as the radiolabeled indicator an alpha-subunit-reactive Mab. The monoclonal-immunoradiometric assay had a lower limit of sensitivity of 0.05 ng/ml. Serum levels of hCG or hCG-like material with CTP structure were measured in 229 healthy blood donors; 1.1% of healthy men and 4.6% of nonpregnant women younger than 50 yr had serum values varying between 0.05 and 0.23 ng/ml. Moreover, 6 to 7 healthy women older than 50 yr had detectable levels in the 0.05-0.20 ng/ml range. To study the disappearance rates in normal women, we followed serum hCG serum levels of 6 women who had previously received a single im injection of the hormone. These individuals failed to develop a pregnancy after in vitro fertilization; hCG declined from 0.5 to 0.05 ng/ml within 2 weeks. These results were in contrast to the findings in 12 patients with hCG-producing tumors. In 9 patients without any evidence of recurrent disease, hCG levels became undetectable within 5 months. However, 3 others had levels consistently above 0.05 but below 0.5 ng/ml. In 2 of these three patients, subsequent increasing hCG levels were associated with tumor recurrence. We conclude that this hCG assay based on both anti-peptide and anti-hCG Mabs may be useful in tumor monitoring.

[Effect of chronic chloroquine poisoning on the cardiac binding sites of calcium inhibitors in the rat]

Among the antimalarial drugs, chloroquine (CLQ) and 4-aminoquinoline derivatives display important interferences with biological membranes. The present study reports the effects of CLQ on dihydropyridine binding sites, measured in the heart of rats intoxicated with the drug. Acute intoxication does not entail any modification of the sites. On the other hand, binding sites were dramatically decreased by a chronic intoxication realized twice a week. In such a case, this decrease may be directly related to CLQ concentration in the heart. The regulation mechanisms involved are discussed.

CA 125 (ovarian tumour-associated antigen) in ascitic liver diseases

The presence of Ca 125, an ovarian cancer-associated antigen, was assessed in serum from patients with liver diseases with (n = 26) and without (n = 26) ascites. Abnormal levels of serum CA 125 were observed in all patients with ascites and in 4 patients without ascites (15%). We conclude that CA 125 is a non-specific marker of ascites whatever the origin: ovarian carcinoma, cirrhosis or peritoneal inflammatory process.

Ellipticine derivatives interact with muscarinic receptors

Ellipticine derivatives or analogues, tetracyclic alkaloids used in human cancer treatment, have been evaluated with regard to their interaction with several neurotransmitter receptors, in order to explain or to predict the side effects which occur in man. These drugs were recently found to be reversible non-competitive inhibitors of cholinesterases. In this study, we have shown that ellipticines are also potent muscarinic antagonists, only 100-fold less active than atropine in inhibiting 50% of the specific binding of (3H) quinuclidinyl benzilate on rat brain preparation of muscarinic receptors. That the interaction with muscarinic receptors is quite unique has been demonstrated by the lack of interaction with three other neurotransmitter receptors. Tertiary amines show relatively less blockade of muscarinic receptors, while substituted ammonium ions are better inhibitors of the QNB binding. The possible mechanisms of in vivo action of these alkaloids is discussed.

Drug-induced antibodies during 2-N-methyl-9-hydroxyellipticinium acetate (NSC-264137) treatment: schedule dependency and relationship to hemolysis

Drug-dependent antibodies were investigated in patients treated with elliptinium acetate, a cytostatic drug with activity in advanced breast cancer. Retrospective analysis of 83 patients, receiving weekly intravenous elliptinium, showed a high incidence of anti-elliptinium antibodies (20%). Hemolysis occurred among antibody-positive patients, apparently related to the antibody titer. The predictability of anti-elliptinium antibodies for hemolysis and the schedule dependency of antibody development was examined prospectively. Among 42 patients treated weekly for at least three courses, 40% developed antibodies. Of 30 patients receiving elliptinium daily for three days every three weeks, none developed either antibodies or hemolysis. Only antibody positive patients, with titers greater than or equal to 32 were at risk for hemolysis. The possible mechanisms are discussed.

Identification of epitopes associated with hCG and the beta hCG carboxyl terminus by monoclonal antibodies produced against a synthetic peptide

We have produced a library of monoclonal antibodies directed against a 37-amino acid synthetic polypeptide analogous to the carboxyl terminus of hCG. Five antibodies, designated FB01, FB02, FB03, FB04, and FB00, were developed and analyzed with respect to affinity and specificity for epitopes on human chorionic gonadotropin (hCG) and beta hCG by enzyme-linked immunoabsorbent and radioimmunoassays (RIA). All monoclonal antibodies demonstrated low affinity constants (approximately 10(-7) liters/mol) compared with those obtained by immunization with native beta hCG. One antibody, namely FB00, bound only to the synthetic peptide, whereas all other monoclonal antibodies recognized either free native beta hCG or both beta hCG and HCG. Antibodies produced against the synthetic peptide did not cross-react with other glycoprotein hormones such as LH, TSH, and FSH. Characterization of the monoclonal antibody-binding sites revealed the presence of at least four separate and distinct epitopes on the last 35 amino acids of beta hCG. Indeed, one epitope recognized by FB01 is located between residues 109 and 118, whereas another antigenic region recognized by FB04 appears to be present on the 109-121 portion of the molecule near or at position 118. One additional antigenic site was localized between residues 118 and 136. Finally, FB00 recognized an epitope located on the last 10 amino acids (136-145) of beta hCG. With the use of such antibodies, two- and three-site monoclonal RIA were developed and employed to detect free beta hCG and hCG in sera of patients with choriocarcinoma. These assays may be useful in the detection of beta hCG- and hCG-producing tumors and subsequent monitoring of patients in response to surgery and/or chemotherapy.

Identification of epitopes associated with hCG and the beta hCG carboxyl terminus by monoclonal antibodies produced against a synthetic peptide

We have produced a library of monoclonal antibodies directed against a 37-amino acid synthetic polypeptide analogous to the carboxyl terminus of hCG. Five antibodies, designated FB01, FB02, FB03, FB04, and FB00, were developed and analyzed with respect to affinity and specificity for epitopes on human chorionic gonadotropin (hCG) and beta hCG by enzyme-linked immunoabsorbent and radioimmunoassays (RIA). All monoclonal antibodies demonstrated low affinity constants (approximately 10(-7) liters/mol) compared with those obtained by immunization with native beta hCG. One antibody, namely FB00, bound only to the synthetic peptide, whereas all other monoclonal antibodies recognized either free native beta hCG or both beta hCG and HCG. Antibodies produced against the synthetic peptide did not cross-react with other glycoprotein hormones such as LH, TSH, and FSH. Characterization of the monoclonal antibody-binding sites revealed the presence of at least four separate and distinct epitopes on the last 35 amino acids of beta hCG. Indeed, one epitope recognized by FB01 is located between residues 109 and 118, whereas another antigenic region recognized by FB04 appears to be present on the 109-121 portion of the molecule near or at position 118. One additional antigenic site was localized between residues 118 and 136. Finally, FB00 recognized an epitope located on the last 10 amino acids (136-145) of beta hCG. With the use of such antibodies, two- and three-site monoclonal RIA were developed and employed to detect free beta hCG and hCG in sera of patients with choriocarcinoma. These assays may be useful in the detection of beta hCG- and hCG-producing tumors and subsequent monitoring of patients in response to surgery and/or chemotherapy.

Two-dimensional electrophoretic analysis of cytosols from human breast tumors: optimal migration conditions

In an examination of cytosols from human breast tumors, we performed two-dimensional electrophoretic analysis. Several migration conditions were tried in a search for a homogeneous repartition of cytosolic proteins. The most workable gels were obtained with a 4.40 to 8.05 pH gradient in the first dimension and a homogeneous 125 g/L acrylamide/sodium dodecyl sulfate gel, 1 mm in thickness, in the second dimension. The practicability of this method is discussed.

Two-dimensional electrophoretic analysis of cytosols from human breast tumors: optimal migration conditions

In an examination of cytosols from human breast tumors, we performed two-dimensional electrophoretic analysis. Several migration conditions were tried in a search for a homogeneous repartition of cytosolic proteins. The most workable gels were obtained with a 4.40 to 8.05 pH gradient in the first dimension and a homogeneous 125 g/L acrylamide/sodium dodecyl sulfate gel, 1 mm in thickness, in the second dimension. The practicability of this method is discussed.

Benzodiazepine receptors on human blood platelets

Binding studies conducted on membrane preparation from human platelets using (3H) Ro5-4864 and (3H) diazepam showed specific and saturable binding. Scatchard analysis revealed a single class of binding sites with KD = 10.8 +/- 0.9 nM and Bmax = 775 +/- 105 fmol/mg protein for (3H) Ro5-4864 and KD = 10.5 +/- 1.1 nM and Bmax = 133 +/- 19 fmol/mg for (3H) diazepam. We were unable to detect any GABA binding site on crude membrane preparation, nor did GABA enhance the binding of (3H) Ro5-4864 or (3H) diazepam. This suggests that benzodiazepine receptors are uncoupled to GABA system on human platelets. Ro15-1788, a specific antagonist for "central type" benzodiazepine (BDZ) binding sites was inactive in displacing (3H) Ro5-4864 from membrane receptors, while PK 11195 (a specific ligand for the "peripheral type" receptor) was the most potent of the drugs tested in inhibiting (3H) Ro5-4864 binding. These results indicate that human blood platelets bear "peripheral-type" BDZ receptor. Moreover, we could not detect any (3H) propyl beta carboline specific binding on platelet membranes. Results on benzodiazepine receptors on human circulating lymphocytes are also reported and similarity in pharmacological properties with platelet benzodiazepine receptors is suggested.

A monoclonal antibody against a synthetic peptide is specific for the free native human chorionic gonadotropin beta-subunit

A totally synthetic molecule (109-145 peptide) analogous to the beta-subunit carboxyl terminus was used as an antigen in the development of antibodies by the hybridoma technique. A monoclonal antibody (702 D7) specifically recognized the free native beta-human CG (beta hCG). 702 D7 was of the immunoglobulin G1 subclass and was directed against an antigenic site localized in a 10-amino acid sequence (109-118) or less. The recognition of an epitope located in the 109-118 region could explain the specific recognition of beta hCG observed with 702 D7, in contrast to monoclonal antibodies directed against a 118-145 region with a recognition of both beta hCG and whole hCG, as observed with a second monoclonal antibody (1032) to synthetic peptide. Immunohistochemical results and preliminary data obtained from the immunoradiometric assay show that 702 D7 provides a clinical tool for the detection of free beta-subunit secretion even at low concentrations, and could allow the study of this subunit or its metabolites produced by normal and tumoral cells.

In vivo modulation of muscarine receptors in rat brain by acute lead intoxication

In our experiments on acutely lead exposed rats we observed a marked increase (a 2-fold or 3-fold increase with 30 mg/kg or 60 mg/kg lead acetate, respectively) in [3H]quinuclidinyl benzilate [( 3H]QNB) specific binding to muscarine receptors from striatum and cortex, without any change in receptor affinity. Muscarine receptor level was maximal 2 h after intoxication, but the effect of lead on [3H]QNB binding was completely reversible in 24 h, without any lead redistribution to other brain areas being observed during this time period. Modulation of muscarine receptors in rat brain during in vivo acute intoxication might be involved in some of the observed neurotoxic effects of lead, resulting of an action on cholinergic neurotransmission. The various possible mechanisms of the lead effect on [3H]QNB binding are discussed.

Characterization of a peripheral-type benzodiazepine binding site on human circulating lymphocytes

Binding studies conducted with [3H]Ro 5-4864, a specific ligand for peripheral-type benzodiazepine receptors, on circulating lymphocytes from 5 normal volunteers provided evidence for a single, saturable (Bmax 12.2 +/- 3.6 fmol/10(6) cells), and high affinity (KD 7.1 +/- 2.0 nM) specific binding site. We were unable to detect any GABA receptor, suggesting that human lymphocytes bear a peripheral-type benzodiazepine binding site not coupled with the GABA system. Results on lymphocytes from chronic lymphocytic leukemics are also reported.

Interaction between hepatitis b virus and alcohol consumption in liver cirrhosis. An epidemiologic study

The relationship between alcohol consumption and the presence of seric hepatitis B virus markers has been studied in 125 male patients with liver cirrhosis and 126 control subjects. Mean daily alcohol consumption was found to be higher in patients than in controls. Hepatitis B virus seric markers were also more frequently observed in patients than in controls (53.6% vs. 36.5%, 2p less than 0.05). This was due to the greater frequency of hepatitis B core antibody alone or with hepatitis B surface antigen in the patients (2p less than 0.05). The possible interaction between alcohol and B virus was studied by log-linear hierarchic models for contingency tables. Data were displayed in a three-way classification frequency table (diagnosis, daily alcohol consumption, and hepatitis B virus seric markers). A model assuming that alcohol and seric markers of unresolved infection by hepatitis B virus are independently linked to cirrhosis gives the better goodness of fit between observed and estimated frequencies. The result however, suggests, that hepatitis B virus infection does not increase the influence of alcohol consumption on the production of cirrhosis.

Diet, alcohol, tobacco and risk of cancer of the pancreas: a case-control study

In view of the increased incidence of pancreatic cancer and the possible aetiological role of certain dietary factors, a retrospective epidemiological study was undertaken to investigate the roles of tobacco, alcohol, fat, protein and carbohydrate intakes. Sixty-nine patients with pancreatic adenocarcinoma, and 199 normal subjects were interviewed. Data were obtained on life time drinking, smoking and dietary habits. Conditional logistic regression models were used to analyse the relative risk variations. It was shown that the relative risk of cancer of the pancreas increases with fat and alcohol intakes, does not vary with protein intake, and decreases with carbohydrate intake and duration of alcohol consumption. Alcohol may be not directly involved in the aetiology of cancer of the pancreas: its effect could be due to the contents of some alcoholic beverages.

Production and in vitro utilization of monoclonal antibodies to human thyroglobulin

Human thyroglobulin (Tg) was used as an antigen in the development of antibodies by the hybridoma technique. From four antibodies that bound more than 40% labeled Tg, two were characterized (182/E4 and 211/A5). They were both of the immunoglobulin G 2ab subclass, and provided an affinity constants (Ka) of 1.2 X 10(10) and 7.7 X 10(9) mol-1, respectively. The specificity of these antibodies was demonstrated by the absence of cross-reaction by monoiodothyronine, diiodothyronine, T3, T4, and sialic acid. A RIA was developed with 182/E4 or 211/A5, and the least detectable dose, based on the standard curve, was 10 ng/ml. The immunoreactivities of 182/E4 and 211/A5 to four Tg preparations different in iodine content appeared to be identical. Histochemical staining was used on normal and neoplastic tissues with both antibodies. Positive reactions were obtained in both cells and colloid, with heterogeneous staining from one follicle to another. Papillary carcinoma showed numerous positive cells, in contrast with Hürtle cell tumors which displayed very few positive cells. Anaplasic giant and spindle cells were negative. Monoclonal antibodies to human Tg are useful for in vitro detection of Tg.

Catechol-O-methyltransferase activity and aminergic binding sites distribution in human peripheral blood lymphocyte subpopulations

We have studied the binding of [3H]dihydroalprenolol, a beta-adrenergic ligand, and [3H]spiroperidol, a dopaminergic ligand, to human peripheral blood lymphocyte subpopulations. The catechol-O-methyltransferase activity on these different cells was also determined. On intact living cells, an unequal distribution of both beta-adrenergic and dopaminergic binding sites was found between B- and T-lymphocyte subpopulations. In each binding, T cells exhibited a lower number of binding sites than B cells. On particulate preparation, catechol-O-methyltransferase activity showed a similar distribution, but binding data with such material were quite different. Although it was not possible to detect dopaminergic binding sites on particulate preparation, T and B lymphocytes contained equivalent numbers of beta-adrenergic binding sites. Different explanations for these results are proposed.

Muscarinic cholinergic receptors on circulating human lymphocytes: evidence for a particulate binding site

Lymphocytes from thirteen normal volunteers were investigated for their muscarinic cholinergic receptors content. A particular binding site was characterized with 3H-quinuclidinyl benzilate; saturation binding occurred at 80 X 10(-9)M and scatchard analysis provided a dissociation constant of 40 X 10(-9)M. These results showed that there were about 4000 muscarinic receptors on human lymphocyte. Although, it is possible to demonstrate the presence of binding site on a particulate preparation, the significance of such low-affinity receptor is yet unclear.

Catechol-O-methyl transferase activity in human mononuclear cells

Catechol-O-methyl transferase (COMT) activity was investigated in human peripheral mononuclear cells and in human lymphoblastoid cells lines. In any case, we have detected enzymatic activity in the membrane fraction of the cells. Km was found to be 4-9 10(-6) M and the enzyme was inhibited by tropolone and the lack of magnesium. The eventual association of COMT with adrenergic receptor-adenylate cyclase system in mononuclear cells is discussed.