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Biomedical subjects

D Bellet

Publications and source records attributed to D Bellet.

At least 91 records · Page 5Linked to original sources
PubMed1989

Phase I clinical trial of monoclonal anti-human chorionic gonadotropin antibody in women with an ectopic pregnancy.

A phase-I clinical trial of a mouse monoclonal anti-human chorionic gonadotropin (hCG) antibody designated as HT13 was conducted in three patients treated for ectopic pregnancy. Doses of 5 and 25 mg of purified antibody were injected into patients. Monoclonal antibody serum levels dropped to 0 within 1 to 5 days. Human antibodies directed against mouse immunoglobulins were not detected at up to 41 days after injection. In one patient, the tubal pregnancy resolved, as confirmed by hCG levels of less than 10 mUl/mL and by tubal patency at hysterosalpingography. The time of resolution was 30 days. In two patients, salpingectomy was performed because of persistence of elevated hCG levels, whereas HT13 had a striking effect on progesterone (P) and estradiol (E2) serum levels. The injection of anti-hCG antibody did not appear to interfere with the subsequent fertility of patients, and two out of three patients later developed a successful pregnancy. While the precise role of antibody injection in the interruption of ectopic pregnancy remains speculative, the injection of monoclonal anti-hCG antibody appears to induce a dramatic decrease in the production of both P and E2.

Antibodies, Monoclonal↗
PubMed1989

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.

Amino Acid Sequence↗
PubMed1989

The development of a two-site enzyme immunometric assay (EIA) for calcitonin and its application in the measurement of the hormone in normal subjects, MTC-patients and post-menopausal women.

We have developed a sensitive, two-site enzyme immunometric assay (EIA) using high affinity monoclonal antibodies for the measurement of immunoreactive human calcitonin (i-hCT) and compared the performance of the assay with that of the conventional radioimmunoassay (RIA). The sensitivity of an overnight EIA (2 pmol/l) was comparable with the long incubation (7 days) RIA. Both, the EIA and the RIA have been applied for the measurement of i-hCT in three groups: normal volunteers (n = 53), post-menopausal women (n = 25) and patients with MTC (n = 20). The results showed that in all three groups, the level of i-hCT was somewhat lower than that measured by RIA due to its greater specificity. The EIA can provide an attractive alternative to the conventional RIA for both routine diagnostic work and physiological studies.

Antibodies, Monoclonal↗
PubMed1989

[The value of tumor markers in digestive oncology].

Over the last few years, many tumor markers have been proposed to clinicians but only a limited number of them meet the necessary criteria to be useful for either screening, diagnosis, prognosis or follow-up of gastrointestinal (GI) tumors. Both CEA and Ca 19-9 have proven to be clinically useful for the detection of recurrent tumors. AFP remains the most useful marker for the follow-up of hepatocellular carcinoma (HCC). Its interest for the early detection of primary tumor is debated. Recent data suggest that assays based on monoclonal antibodies to AFP could be used for detection HCC in high risk populations. Decarboxy-prothrombin assay may be a complement to the AFP test in this localization. In addition to GI hormones, serotonin and urinary 5HIAA, Neuron Specific Enolase appears to be a valuable marker for the follow-up of neuroendocrine tumors of the GI tract. Only a few of the new tumor-associated antigens detected by monoclonal antibodies, appear to be promising clinical ly e.g. Ca50 TAG-72, PAO. Monoclonal antibodies to tumor-associated markers have also been used with other techniques: Immunohistochemistry: this technique is useful to the pathologist for the diagnosis of undifferentiated tumors by demonstrating the presence of specific antigens on tissue samples. Immunoscintigraphy: it can be useful for the detection of either metastases of recurrences of colorectal cancer by using anti-ACE antibodies labeled with Iodine 131 iodine 123 or indium 111. However immunoscintigraphy is less sensitive than both ultrasonography and CT scan for localizing hepatic metastases. At the present time the best indication of this method remains the diagnosis of pelvic recurrences.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1988

Monoclonal antipeptide antibodies as tools to dissect closely related gene products. A model using peptides encoded by the calcitonin gene.

We have explored the possibility of using mAb as tools for distinguishing between closely related gene products. We utilized calcitonin (CT) gene products as a model, because this 32-amino-acid-amidated hormone is biosynthesized by post-translational processing of a larger precursor. By using CT as a hapten, we had previously identified a mAb (CT07) with restricted specificity to mature CT, and had shown that another mAb (CT08) directed to a different epitope bound to both CT and the CT precursor. In this study, we used synthetic peptides analogous to various regions of biosynthetic intermediates of CT as haptens, and generated a library of mAb which define distinct epitopes. First, we identified two separate epitopes located in either the 1-11 or the 12-21 region of the C-terminal flanking peptide of CT (katacalcin, KC), and which were recognized by mAb KC01 and KC04, respectively. Second, we identified a conformational epitope in the C-terminal region of the putative glycine-extended form of CT (CT-Gly). This epitope was recognized by mAb CT19 and was shared by mature CT but not by CT precursors. Third, we identified an epitope restricted to CT-Gly and recognized by mAb CT20. For dissecting between related products of the CT gene, we designed different monoclonal immunoradiometric assays (m-IRMA) based on CT08 as the radiolabeled indicator antibody. A first m-IRMA based on CT07 as the capture antibody specifically recognized mature CT and did not cross-react with CT precursors. Conversely, another m-IRMA with KC01 as the capture antibody was specific for CT precursors and did not cross-react with either mature CT or CT-Gly. A third assay based on CT20 as the capture mAb was specific for CT-Gly and was not affected by the presence of either CT precursors or mature CT. We also used these antibodies to demonstrate that neoplastic C cells incompletely released processed CT precursors in serum, in addition to mature CT. This study demonstrates that mAb can be used as tools to selectively recognize closely related gene products. These findings might be applied to the study of other molecules biosynthesized by enzymatic modifications of a larger precursor.

Amino Acid Sequence↗
PubMed1988

Prognostic factors in gestational trophoblastic tumors. A multivariate analysis.

One hundred sixty-two gestational trophoblastic tumors (GTT) were treated at the Institute Gustave-Roussy, Villejuif, France, from 1975 to 1985. Sustained complete remission (CR) was obtained in 146 patients (90%). All 97 patients with no histologic diagnosis of choriocarcinoma were cured, including 19 patients considered at high risk initially. Among 65 histologic chariocarcinoma patients, 16 died (CR, 75.5%) including seven initially nonmetastatic patients. Using a univariate analysis, all factors tested in the whole group of patients were more or less significant except for age and parity. However, when the same variables were tested in patients considered at high risk initially, only three factors were statistically significant. Those three factors were the only ones associated with a statistically significant higher relative death risk (RR) on multivariate analysis and are as follows: an antecedent nonmolar pregnancy (RR = 4.3; P less than 0.01); initial presentation with more than one metastatic organ (RR = 7.4; P less than 0.01); and primary resistance to single agent (RR = 18.8; P less than 0.0001) or multi-agent chemotherapy (RR = 26.1; P less than 0.0001). It seems that those three factors, together with a histologic diagnosis of choriocarcinoma, are the prognostic factors that discriminate patients with unfavorable outcomes among the high-risk group.

Choriocarcinoma↗
PubMed1988

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.

Amino Acid Sequence↗
PubMed1988

Construction and clinical validation of a sensitive and specific assay for serum mature calcitonin using monoclonal anti-peptide antibodies.

Using calcitonin (CT) as an hapten, we have generated a library of monoclonal antibodies. Six monoclonal antibodies were developed and analyzed with respect to affinity and specificity for epitopes on CT by enzyme linked immunosorbent assay and radioimmunoassay. These antibodies were used in the construction and the optimization of a two-site monoclonal immunoradiometric assay (m-IRMA) for CT. We used a combination of two monoclonal antibodies to develop an assay which is rapid (overnight incubation), sensitive (10 pg/ml) and strictly specific for the mature form of calcitonin, ie the 32 amino acid-long polypeptide bearing a prolineamide as the C-terminal residue. This assay was utilized to demonstrate that mature calcitonin circulates as heterogeneous molecular species resulting from polymerization of calcitonin by disulphide linkage and/or by aggregation on irrelevant proteins. The clinical relevance of this assay was studied on a series of patients with medullary carcinoma of the thyroid (MCT) and the characteristics of the assay was compared with those of a conventional polyclonal radioimmunoassay. The m-IRMA for CT proved to be useful for both the diagnosis and the follow-up of MCT.

Adult↗
PubMed1988

Is anti-alphafetoprotein immunoscintigraphy a promising approach for the diagnosis of hepatoma? Implications of a quantitative study in 41 patients.

The actual interest of immunoscintigraphy for the detection of liver tumours was investigated by both visual examination and quantitative analysis in 41 patients with hepatoma (HCC, 21 cases, 13 AFP-secreting), other primary or secondary liver cancer (9 cases), testicular cancer (2 cases) and cancer free cirrhosis (9 cases). All patients were injected with 123I-anti-alphafetoprotein (AFP) monoclonal antibodies (MAbs) and scans were performed after 28 +/- 2 h. In the hepatoma-bearing patients, 11 positive anti AFP scans were found; 9 of them had an enhanced serum; besides, 3 non HCC tumours were also detected. With respect to hepatoma diagnosis, sensitivity was 52.5% and specificity 66.5%. For all hepatomas, it was striking that the positivity rate was 2/10 and 9/11, respectively, when HCC was and was not associated with cirrhosis. Among 6 patients with a positive anti AFP scan who were also injected with control anti hCG 123I-MAb, 5 positive anti hCG scans were surprisingly found, with specificity indices ranging between 1.00 and 1.75. The quantitative study also highlighted the importance for hepatoma detection of specific and non specific factors such as serum AFP, tumoural vascularization, non tumoural liver uptake and intrahepatic distribution of HCC. Anti AFP immunoscintigraphy appears as a poorly sensitive and moderately specific method for hepatoma diagnosis. In contrast, non tumoural liver uptake level could be more useful for discriminating HCC from liver metastases and perhaps to detect the early extension of HCC.

Adult↗
PubMed1988

Differential production of human chorionic gonadotropin and free subunits in gestational trophoblastic disease.

Serum levels of human chorionic gonadotropin (hCG) and its free subunits (alpha hCG and beta hCG) were determined by means of highly sensitive and specific monoclonal and antipeptide-based monoclonal immunoradiometric assays. During normal pregnancy, the beta hCG to hCG ratio appears constant at approximately 0.5% after 5 weeks of gestation. In contrast, gestational choriocarcinoma was characterized by absolute serum beta hCG levels varying from three to 280 times greater than the maximum values observed during pregnancy and by exceedingly high beta hCG to hCG ratios. In complete hydatidiform mole, this ratio was intermediate between normal pregnancy and choriocarcinoma. The ratios of free beta hCG to hCG will distinguish normal from complete molar pregnancy (p less than 10(-8)), hydatidiform mole from choriocarcinoma (p less than 10(-4)), and choriocarcinoma from normal pregnancy (p less than 10(-8)) with high probability. Finally, it was found by means of the high sensitivity hCG immunoradiometric assays (less than 0.02 ng/ml) that this assay predicted very early tumor recurrence in patients with gestational choriocarcinoma.

Adult↗
PubMed1988

A sensitive and specific two-site enzyme-immunoassay for human calcitonin using monoclonal antibodies.

A highly sensitive, specific and rapid two-site enzyme-immunometric assay (EIA) for the measurement of immunoreactive (ir) human calcitonin (hCT) in human plasma was developed using high-affinity monoclonal antibodies. The assay was validated in terms of sensitivity, specificity and reproducibility and its performance compared with that of a radioimmunoassay (RIA) employing a polyclonal antiserum. The sensitivity of the overnight EIA (2 pmol/l) was comparable with the long-incubation (7 days) RIA. The overnight RIA had a sensitivity of 10 pmol/l. The inter- and intra-assay variations of the EIA were less than 12%. Some related and non-related peptides were compared with synthetic hCT for cross-reactivity in the assay and were found to be negative. The mean recovery of added synthetic hCT from plasma of normal volunteers was 96%. Both RIA and EIA have been applied to the measurement of ir-hCT in normal volunteers and in patients with medullary carcinoma of the thyroid. In both groups, the level of ir-hCT measured by EIA was found to be lower than that measured by RIA, presumably due to the ability of the more specific EIA to detect only the 'mature' form of the hormone. EIA offers an attractive alternative to the more cumbersome and lengthy RIA in current usage, with the added advantage of employing a non-isotopic label.

Alkaline Phosphatase↗
PubMed1988

[Chorionic gonadotrophic hormone and transitional cell carcinoma of the bladder. Immunohistochemical characterization of HCG and its alpha and beta subunits].

Investigation of cellular localization of hCG and alpha- and beta- subunits in 17 transitional cell carcinomas of urinary bladder was performed using immunohistochemical techniques. Serial sections were tested with monoclonal antibodies to hCG, free beta hCG and free alpha hCG. Transitional cell carcinomas producing hCG and/or beta hCG are easily found (6/17 cases). None of these tumors correspond morphologically to a choriocarcinoma. However, it must be mentioned that neoplastic areas exhibit some features reminiscent of a choriocarcinomatous structure. Notably, positive cells can be disposed at the periphery of neoplastic nests, mimicking the arrangement of syncytiotrophoblast. Positive neoplastic cells express hCG and/or beta hCG; alpha hCG immuno-reactivity is quite rare. The relative distribution of hCG/beta hCG is excessively variable from case to case. In contrast, normal transitional epithelium contains endocrine cells which only express the alpha-subunit of hCG.

Carcinoma, Transitional Cell↗
PubMed1988

Spontaneous resolution of ectopic pregnancy.

Fourteen patients with ampullary tubal pregnancy confirmed by laparoscopy were initially managed conservatively. Serum human chorionic gonadotropin (hCG) levels were measured daily and strict clinical monitoring performed. In nine patients (64%), the tubal pregnancy spontaneously resolved. In four cases (29%), surgery was ultimately necessary. One patient with a coexistent intra- and extrauterine pregnancy was also successfully managed conservatively. There was a high probability of spontaneous resolution of the pregnancy when the serum hCG level at diagnosis was less than 1000 mIU/mL. Hysterosalpingography was performed after the spontaneous resolution of the tubal pregnancies. Tubal patency was demonstrated in all six patients, and three are currently pregnant. We conclude that conservative therapy allows spontaneous resolution of certain types of ectopic pregnancy.

Abortion, Spontaneous↗
PubMed1987

Monoclonal antibodies distinguish synthetic peptides that differ in one chemical group.

By using human calcitonin (hCT), human calcitonin-gene-related peptide (hCGRP), and a synthetic peptide with a sequence analogous to the 34 C-terminal amino acids of human preprocalcitonin (designated as PQN-34) as haptens in the generation of monoclonal antibodies, we assessed the role of amido and amino groups in paratope-epitope binding. By using peptide inhibition experiments and solid-phase immunoassays, monoclonal anti-hCT antibody CT07 and monoclonal anti-hCGRP antibody CGR01 were found to bind to an antigenic determinant located in the C-terminal segment of the hormones. These epitopes comprise the seven C-terminal amino acids of the hormones, and the presence of the hormone-ending carboxamide group was found to be essential for antibody binding. The corresponding heptapeptides, either bearing a carboxyl group or else linked to a glycine residue at their C-terminal part, failed to react with the antibodies. Moreover, these monoclonal antibodies did not bind to synthetic peptides analogous to the C-terminal region of the hormone precursor molecules that comprised the epitope site flanked by a peptide sequence. In an attempt to assess whether amido groups when present on the side-chain of amino acids may also modulate antibody binding, a monoclonal antibody referred to as QPO1 was produced and was found to recognize an antigenic determinant localized in the N-terminal region of the PQN-34 peptide bearing a glutamine residue as the N-terminal amino acid. The epitope was found to correspond to a topographic assembled site, and binding of QPO1 was found to be substantially dependent on the presence of the free amino and the side-chain amido groups borne by the N-terminal glutamine residue of this peptide PQN-34. In contrast to these findings, an antigenic determinant located in the internal sequence of calcitonin and recognized by monoclonal anti-hCT antibody CT08 was found to be expressed on the mature form of the hormone, as well as on synthetic peptides with sequence mimicking that of preprocalcitonin. These data should guide the choice of synthetic peptide haptens for the production of anti-protein antibodies.

Amino Acid Sequence↗