Biomedical subjects

R Madiyalakan

Publications and source records attributed to R Madiyalakan.

At least 19 recordsLinked to original sources

PubMed2001

Induction of CA125-specific B and T cell responses in patients injected with MAb-B43.13--evidence for antibody-mediated antigen-processing and presentation of CA125 in vivo.

The murine monoclonal anti-CA125 antibody MAb-B43.13 has previously been administered as an immunoscintigraphic agent in order to monitor recurrence of ovarian cancer in patients, and a long-term follow-up demonstrated a survival benefit for these patients. The clinical benefit was initially attributed to the activation of the idiotypic network. The objective of this study was to investigate the role of CA125-MAb-B43.13 immune complex formation on the induction of CA125-specific immune responses. Analysis of patient serum samples from pharmacokinetic studies demonstrated that the antibody forms immune complexes with CA125 in circulation within 30 minutes of injection. Induction of humoral and cellular anti-CA125 responses correlated with the amount of circulating CA125 antigen present at time of antibody injection. Subsequent to the injection of MAb-B43.13, the patients generated anti-CA125 antibodies that were directed against various epitopes on the antigen and were not restricted to the specific epitope recognized by MAb-B43.13. The generation of CA125-specific B and T cell responses after MAb-B43.13 injection correlated with improved survival. The influence of circulating CA125 for the induction of CA125-specific immune responses and the multi-epitopic nature of the human anti-CA125 antibodies suggest that the majority of these antibodies were not induced via the idiotypic network but by the autologous antigen itself. Since antibody and T cell responses to CA125 were not present before injection of MAb-B43.13, it is hypothesized that complex formation of MAb-B43.13 with circulating antigen triggers the induction of CA125-specific immune responses.

Adenocarcinoma↗

PubMed2001

Characterization of an anti-MUC1 monoclonal antibody with potential as a cancer vaccine.

The monoclonal antibody (MAb) AR20.5 is a murine MAb, generated against the tandem repeat protein backbone of the tumor-associated antigen MUC1. MAb AR20.5 reacts strongly with either the soluble form or the cell surface epitope of MUC1 on many human cancer cell lines. It also reacts with a 23-amino acid MUC1 peptide, E23, which includes the core tandem repeat sequence. Epitope mapping confirmed that MAb AR20.5 recognizes a minimum of six residues with the sequence DTRPAP. Inhibition of glycosylation of MUC1 resulted in decreased binding of MAb AR20.5 to cell surface MUC1, suggesting that MAb AR20.5 binding is carbohydrate dependent. The antibody was studied in a human PBL-SCID/beige mouse model to evaluate its effect on progression of NIH:OVARCAR-3 tumors. Tumor reduction was observed in mice injected with MAb AR20.5, but not in mice treated with control murine antibody or PBS (p < 0.001 and p < 0.05, respectively). An anti-tumor effect could also be demonstrated in a CB6F1 mouse model with the MUC1 transfectoma 413BCR.

Animals↗

PubMed2000

Therapeutic antibodies for prostate cancer.

Twenty five years ago, monoclonal antibodies were envisioned as magic bullets capable of targeting radioisotopes, toxins or cytotoxic drugs to the tumor site. It was soon realized that the potential of therapeutic antibodies far exceeded their use as carrier molecules and that native antibodies could also act as effector molecules capable of triggering a wide variety of antitumor responses. Today, we recognize that the utility and versatility of antibody-based products are unlimited; at the same time we have also learned that many obstacles need to be addressed to make antibody therapy an effective treatment modality. Past experiences from clinical trials and new developments in the field of antibody technology have paved the way towards the creation of new strategies capable of circumventing or minimizing these difficulties. Antibody therapy is currently being tested in multiple trials for a variety of cancers, including prostate cancer. This review discusses the different antibody-based strategies currently under investigation for prostate cancer.

Journal Article↗

PubMed1999

Immunotherapy of human ovarian carcinoma with OvaRex MAb-B43.13 in a human-PBL-SCID/BG mouse model.

The monoclonal antibody (MAb) B43.13, binding to the ovarian cancer-associated antigen CA125, has been injected into more than 200 patients with ovarian cancer to detect recurrence of the disease. The follow-up of the patients revealed surprisingly long survival spans for several patients despite high CA125 levels. To investigate the therapeutic effectiveness of OvaRex MAb-B43.13 (AltaRex, Edmonton, Canada) under well-controlled conditions, the antibody was tested in a human-PBL-SCID/BG mouse model with CA125 positive human ovarian cancer cells. Mice were reconstituted with human peripheral blood lymphocytes (PBL, normal donors) by intraperitoneal (IP) injection of 2 to 3 x 10(7) PBL/mouse. OvaRex MAb-B43.13 was administered at 100 microg/mouse in phosphate buffered saline (PBS), in three different experimental set-ups. An isotype-matched control antibody (MOPC21 or MAb-170) and PBS injection served as controls. The ovarian cancer cell line NIH:OVCAR-NU-3 was injected IP at 1 x 10(6) cells/mouse or subcutaneously (SC) at 4 x 10(6) cells/mouse. Human-PBL-SCID/BG mice were either immunized before injection of tumor cells, along with tumor cells or after small tumors were established (2 weeks after transplantation). Antibody injections were repeated twice in 2-week intervals. Functional and cellular characterization of serum and PBL from these mice demonstrated the successful engraftment of a human immune system in those mice. All three experiments showed that OvaRex MAb-B43.13 treatment could (a) delay or prevent development of tumors; (b) reduce the size of small established tumors (SC tumor injection) or suppress ascites formation; (c) delay tumor growth when injected prior to tumor implantation; and (d) prolong the survival of the mice (i.p. tumor injection).

Animals↗

PubMed1998

Expression of a fusion protein of scFv-biotin mimetic peptide for immunoassay.

We constructed two fusion proteins of scFv linked to biotin mimetic sequence (BMS) via different linkers, and expressed them in the Pichia pastoris expression/secretion system. We found that both bi-functional scFv proteins exhibited their intrinsic binding activities to antigen CA125 determined in competitive radioimmunoassay experiments, but the fusion protein with a spacer between the scFv and BMS (scFv-spacer-BMS) showed higher binding activity of streptavidin than the one with c-Myc peptide as a linker.

Antibodies, Bispecific↗

PubMed1998

Anti-idiotype induction therapy: anti-CA125 antibodies (Ab3) mediated tumor killing in patients treated with Ovarex mAb B43.13 (Ab1).

Intravenous injection of the murine monoclonal anti-CA125 antibody B43.13 (Ovarex: Ab1) into ovarian cancer patients led to the induction of an idiotypic network. Of the 75 patients who received one to ten injections of a 2-mg dose of the antibody, 48 developed anti-(mAb B43.13) antibodies (Ab2); 18 of these patients also had elevated levels of anti-[anti-(mAb B43.13)] antibodies (Ab3; = anti-CA125 antibodies) compared to pre-injection values. Characterization of these antibodies revealed that the binding to CA125 could be inhibited by mAb B43.13 in most samples. Human anti-CA125 antibodies or Ab3 purified from patient serum samples specifically recognized human ovarian tumor cells and tissues expressing CA125. In addition, these anti-CA125 antibodies were able to conduct Fc-mediated tumor cell killing (antibody-dependent cell-mediated cytotoxicity). This raises the possibility of using an Ab1 for anti-idiotype induction immunotherapy of cancer.

Animals↗

PubMed1998

Induction of anti-idiotypic humoral and cellular immune responses by a murine monoclonal antibody recognizing the ovarian carcinoma antigen CA125 encapsulated in biodegradable microspheres.

The use of biodegradable poly(DL-lactic-co-glycolic acid) microspheres as a cancer vaccine delivery system for induction of anti-idiotypic responses was investigated using a murine monoclonal antibody B43.13 that recognizes the human ovarian cancer antigen CA125. Immunization of mice with mAb B43.13 encapsulated in poly(DL-lactic-co-glycolic acid) microspheres resulted in enhanced humoral and cellular immune responses compared with mAb B43.13 alone or mAb B43.13 mixed with microspheres. The antibody responses could be further enhanced by the co-encapsulation of mAb B43.13 with monophosphoryl lipid A, a non-toxic adjuvant, in microspheres. Anti-idiotypic humoral responses were shown to result in Ab2 antibodies mimicking the nominal antigen CA125 and Ab3 antibodies recognizing CA125. Further, microsphere delivery of mAb B43.13 also resulted in induction of T cell responses involving T2 cells reactive with mAb B43.13 epitopes and T3 cells recognizing CA125. These results indicate that microsphere delivery of Abl can induce both humoral and cellular anti-idiotypic responses relevant to cancer antigens. This raises the possibility of the use of such formulations for anti-idiotypic induction immunotherapy for cancer.

Animals↗

PubMed1998

Use of encapsulated single chain antibodies for induction of anti-idiotypic humoral and cellular immune responses.

The use of biodegradable poly(lactic-co-glycolic acid) (PLGA) microspheres as a cancer vaccine delivery system for induction of anti-idiotypic responses has been investigated using a single chain antibody scFv-pDL10, which recognizes the human ovarian cancer antigen CA125. Immunization of mice with scFv-pDL10 encapsulated in PLGA microspheres resulted in enhanced humoral and cellular immune responses when compared to scFv-pDL10 alone. Induced anti-idiotypic antibodies (Ab2) which mimic the original antigen CA125 compete with CA125 for the epitope. A cellular response (T2 induction) was also observed. These results raise the possibility of anti-idiotypic antibody induction by a single chain antibody, encapsulated in biodegradeble microspheres, as a potential vaccine for ovarian carcinoma.

Animals↗

PubMed1998

Summary report on the ISOBM TD-6 workshop: analysis of 20 monoclonal antibodies against Sialyl Lewisa and related antigens. Montreux, Switzerland, September 19-24, 1997.

The ISOBM TD-6 Workshop is the first international workshop on monoclonal antibodies against the Sialyl Lewisa (SLea) antigen. Eight research groups participated in a blind study to characterize the epitope binding, relative affinity and performance in immunoradiometric assays, of a panel of 20 monoclonal antibodies. The antibodies were tested against a diverse panel of neoglycoconjugates, purified antigens and human serum pools from gastrointestinal malignancies. Epitope specificities were determined for the majority of antibodies in the panel. Cross-reactivity with related saccharide structures was noted in several antibodies. Overall, the results of the TD-6 Workshop show further development of SLea immunoassays may yield yet more specific assays for the detection and management of gastrointestinal and other malignancies.

Antibodies, Monoclonal↗

PubMed1997

OVAREX MAb-B43.13:IFN-gamma could improve the ovarian tumor cell sensitivity to CA125-specific allogenic cytotoxic T cells.

Various immunological parameters were studied in 100 ovarian cancer patients injected with the OVAREX therapeutic vaccine (the functional component of which is anti-CA125 MAb-B43.13) to explain the serendipitous observation of prolonged survival after such treatment. In addition to CA125-specific humoral and cellular responses, interferon-gamma (IFN-gamma) was also found to be induced in those patients receiving the vaccine. In vitro studies indicated that the expression of MHC I, MHC II, and ICAM I in ovarian tumor cells were upregulated in response to IFN-gamma. Such tumor cells were also found to be more sensitive to CA125-specific cytotoxic T cells compared to cells that were not incubated with IFN-gamma.

Animals↗

PubMed1997

An engineered bivalent single-chain antibody fragment that increases antigen binding activity.

Bivalent single chain Fv (scFv) was constructed by fusing a polypeptide extension containing one or two cysteines to the COOH-terminus of an scFv antibody fragment. The scFv protein was expressed and secreted in a recombinant Pichia pastoris system as a dimer with a C-terminal disulfide bridge, as determined by Western blot analysis under non-reducing conditions. We found that the scFv construct with one cysteine in the C-extension (scFv-1Cys) exhibited a much higher dimer/monomer ratio than the two cysteine counterpart (scFv-2Cys). Binding activity measurements performed by means of a competitive radioimmunoassay showed that scFv-1Cys exhibited specific antigen binding activity, which was almost the same as that of the parental MAb, and approximately four- and fortyfold higher than those of the control scFv monomer and scFv-2Cys.

Amino Acid Sequence↗

PubMed1997

Pharmacokinetics and radiation dosimetry of 99Tcm-labelled monoclonal antibody B43.13 in ovarian cancer patients.

OVAREX MAb B43.13 is a new radiopharmaceutical based on a monoclonal antibody (MAb-B43.13) known to recognize CA 125, a tumour antigen associated with epithelial ovarian cancer. This MAb is capable of facile radiolabelling with 99Tcm and has been shown previously to localize in the tumours of ovarian cancer patients. The present study was initiated to measure the pharmacokinetics of this MAb in the serum of 10 patients with primary or metastatic ovarian cancer. A two-compartment model was found to be best at representing the biodistribution of the 99Tcm-labelled MAb, yielding a 2.6 h distribution phase half-life and a 31.3 h elimination phase half-life. The serum and renal clearances for 99Tcm-MAb-B43.13 were 121 and 53 ml h-1 respectively. These parameters were compared with a similar model developed from the serum values of the MAb itself (determined using an ELISA detection method). Based on the serum pharmacokinetics of 99Tcm-MAb-B43.13 and whole-body planar gamma camera images, an estimate of the radiation dose from 99Tcm was calculated using standard MIRD schema. The organs demonstrating significant 99Tcm uptake included the liver, kidneys, heart and spleen. The whole-body dose was similar to other 99Tcm-labelled MAbs.

Adult↗

PubMed1996

An antibody-lectin sandwich assay for the determination of CA125 antigen in ovarian cancer patients.

A two-step forward sandwich assay was developed for the determination of the ovarian tumour associated glycoconjugate antigen CA125 with anti-CA125 Monoclonal antibody B27.1 on the solid phase and 125I-labelled wheat germ lectin as tracer in the solution phase. This Mab-lectin heterosandwich assay was optimized and the clinical utility was evaluated in sera from healthy volunteers and ovarian cancer patients. A correlation was established between Mab-lectin assay and the dual monoclonal antibody sandwich assay, TRUQUANTOV2 RIA, that uses the same MAb B27.1 on the solid phase and a second 125I-labelled B43.13 MAb in the solution phase. A potentially improved clinical utility is suggested for the Mab-lectin assay. The unique format seems to identify novel isoforms of CA125 with different carbohydrate side chains that would otherwise be undetectable in the MAb-MAb sandwich assay wherein the paratopes are likely directed to protein determinants.

Antibodies↗

PubMed1995

Antiidiotype induction therapy: evidence for the induction of immune response through the idiotype network in patients with ovarian cancer after administration of anti-CA125 murine monoclonal antibody B43.13.

The immune status of ovarian cancer patients receiving anti-CA125 murine monoclonal antibody B43.13 was evaluated by measuring antiidiotypic antibodies (Ab2), antiantiidiotypic antibodies (Ab3), antiisotypic human antimouse antibodies (HAMA), interferon-gamma, and CA125 levels in the serum. A specific assay was developed for the determination of Ab2 antibodies using chimeric MAb B43.13. Of the 50 patients studied, 26 had elevated levels of Ab2. Eleven of these 26 patients also had high titer of antiantiidiotypic (Ab3) antibodies. Eight of the 22 patients analyzed had increased interferon-gamma levels. A tentative correlation was found between survival of these patients' antiidiotype induction.

Antibodies, Anti-Idiotypic↗

PubMed1990

Use of benzyl 2-acetamido-2-deoxy-3-O-(2-O-methyl-beta-D-galactosyl)-beta- D-glucopyranoside [2'-O-methyllacto-N-biose I beta Bn] as a specific acceptor for GDP-fucose: N-acetylglucosaminide alpha(1----4)-L-fucosyltransferase.

A synthetic substrate, benzyl 2-acetamido-2-deoxy-3-O-(2-O-methyl-beta-D- galactopyranosyl)-beta-D-glucopyranoside, was demonstrated to be a specific acceptor for the Lewis blood group-specified alpha(1----4)-L-fucosyltransferase from human saliva and stomach mucosa. The fucosyl linkage of the product resulting from the use of this substrate isolated by paper chromatography was characterized by hydrolysis with specific alpha(1----3)/(1----4)-L- fucosidase. The product can be separated by adsorption onto the reverse-phase cartridge and recovered by one-step elution with methanol. The enzymatic properties of alpha(1----4)-L-fucosyltransferase from saliva and stomach mucosa have also been examined using this substrate.

Chemical Phenomena↗

PubMed1988

Cancer-associated elevation of alpha(1----3)-L-fucosyltransferase activity in human serum.

GDP-fucose:N-acetylglucosaminide alpha(1----3)-L-fucosyltransferase activity was measured in sera of patients with various cancers using a synthetic substrate, N-acetyl-2'-O-methyllactosamine, as an acceptor. One hundred twenty-four of the 169 patients showed significantly high levels of the enzyme activity when compared to healthy controls, irrespective of the location of their tumor. However, enzyme levels were in the normal range in patients with non-neoplastic diseases, such as infectious disease, liver disease, and other inflammatory problems as well as in leukemic patients. The chromatofocusing profile of the enzyme using PBE-94 gel over a pH gradient from pH 6.0 to 4.0 demonstrated that the level of enzyme eluted at pH 5.4 was markedly elevated in the sera of stomach and ovarian cancer patients. A correlation was established between alpha(1----3)-L-fucosyltransferase activity and the presence of malignancy which may be used to evaluate the utility of the enzyme as a tumor marker.

Biomarkers, Tumor↗

PubMed1987

Role of glycosidases in human ovarian carcinoma cell mediated degradation of subendothelial extracellular matrix.

Penetration of the extracellular matrix (ECM) by tumor cells, an event which occurs at various stages of the metastatic process, involves tumor cell glycosidase mediated hydrolysis of proteoglycans (PG). Recently, we observed that human ovarian carcinoma cell lines (HOCC) derived from primary tumors, peritoneal effusions, and distant metastases possess a varying ability to degrade radiolabeled PG of the ECM, while normal cells (human mesothelial cells or ovarian fibroblasts) fail to do so. To determine whether a quantitative relationship exists between glycosidase activity and degradation of ECM, both intracellular and extracellular glycosidase activities were measured for HOCC and normal cell lines. No relationship was found between intracellular glycosidase activities and the ability of cells to degrade ECM. However, a correlation was observed between extracellular or secretory glycosidase activities and HOCC mediated ECM degradation. In particular, a 5-8-fold increase, as compared to normal cells, was observed for HOCC extracellular beta-N-acetylglucosaminidase (EC 3.2.2.30) activity. The accumulation or secretion of this enzyme from HOCC into culture medium was found to be time dependent and not related to intracellular levels. Purified hexosaminidase derived from invasive HOCC was able to hydrolyze [3H]-glucosamine radiolabeled ECM (up to 30% radiolabel) and resulted in the cumulative release of free [3H]-N-acetylglucosamine. This enzyme mediated hydrolysis could be completely prevented with 2-acetamido-2-deoxy-1,5-D-gluconolactone, a competitive inhibitor (Ki 10(-6) M). Finally, HOCC mediated degradation of radiolabeled ECM was discerned to be dependent upon active hexosaminidase action, since tumor cell mediated degradation of ECM could be inhibited by up to 60% in the presence of this synthetic competitive inhibitor. In summary, these studies indicate a strong association between HOCC solubilization of glycoconjugates present in the ECM and extracellular levels of hexosaminidase.

Acetylglucosamine↗

PubMed1987

Phosphorylation of the alpha 1,2-linked mannosylsaccharide by N-acetylglucosamine-1-phosphotransferase from fibroblasts occurs at the terminal mannose.

UDP-GlcNAc: Lysosomal enzyme precursor N-acetylglucosamine-1-phosphotransferase activity from normal fibroblasts was measured using methyl 2-O-(alpha-D-mannopyranosyl) 6-deoxy-6-fluoro-alpha-D-mannopyranoside and methyl 2-O-(6-deoxy-6-fluoro-alpha-D-mannopyranosyl) alpha-D-mannopyranoside as acceptors. The results indicate that the phosphorylation in man alpha 1----2 man sequence occurs at the C-6 position of the terminal mannose residue.

Fibroblasts↗