Serological mapping of the TAG-72 tumor-associated antigen using 19 distinct monoclonal antibodies.

Monoclonal antibody (MAb) B72.3 has been shown to be of potential utility in the management of human carcinoma via its use in (a) the targeting of carcinoma lesions in colorectal and ovarian cancer patients, (b) immunohistochemical analyses of biopsies and effusions, and (c) serum assays to help define the presence of carcinoma. The B72.3-reactive antigen, designated tumor-associated glycoprotein 72 (TAG-72), has been characterized as a high molecular weight glycoprotein with the properties of a mucin. We report here the utilization of MAb B72.3 and 18 second generation MAbs (generated using purified TAG-72 obtained from a colon carcinoma xenograft as immunogen) to construct a serological map of the TAG-72 molecule. The generation and initial characterization of 10 of the second generation MAbs have been described previously; in addition, eight previously unreported MAbs were used. All 19 MAbs produced immune precipitate lines against purified TAG-72 in double immunodiffusion, indicating that each epitope recognized by a single MAb is present at least twice on the TAG-72 molecule. Immunodepletion analyses utilizing 11 of the anti-TAG-72 MAbs indicated that each recognizes the same molecule or population of molecules. Nineteen competition radioimmunoassays were developed and 19 purified competitor immunoglobulins were used in each assay. The patterns of cross-competition indicated the presence of a complex array of tumor-associated epitopes on the TAG-72 molecule. Some of the MAbs recognized epitopes that were structurally or spatially related to one another, but none appeared to recognize identical epitopes. The spectrum of inhibitory reactivities of these MAbs for TAG-72 binding varied from extremely restricted to more broad inhibition. The serological mapping studies reported here provide information as to the range and nature of the epitopes expressed on the TAG-72 molecule, help form the basis for selecting alternative anti-TAG-72 MAbs for use in potential clinical applications, and further define the nature of this oncofetal antigen.

Baculovirus recombinants expressing the human carcinoembryonic antigen gene.

Carcinoembryonic antigen (CEA), one of the most extensively studied human tumor-associated antigens, represents a potential target for passive as well as active immunotherapy. We describe here the first baculovirus recombinants expressing the human CEA gene. Eight baculovirus clones were isolated which expressed products of varying molecular weights; one clone, termed BVCEA-140, was shown to contain multiple CEA epitopes by reactivity to a panel of anti-CEA monoclonal antibodies. When purified protein isolated from this clone was deglycosylated, immunoreactive species ranging from M(r) 50,000 to M(r) 110,000 were found. Results of Southern blot analysis carried out on BVCEA-140 DNA were consistent with the hypothesis that these products result from the stable expression of variants which have recombined within the repeated domains of CEA. Other baculovirus recombinants expressing products comprising different portions of the CEA gene were also derived. One, termed BVCEA-35, was shown to be a recombination between the first 87 bases of domains I and III of the CEA gene. A variant, termed BVCEA-16, contained only the NH2-terminal domain of the CEA gene. Moreover, a recombinant expressing the closely related molecule nonspecific cross-reactive antigen was also derived. As shown here, commercially available preparations of CEA, which are derived from tumor biopsies or cell line supernatants, may contain nonspecific cross-reacting antigens and other contaminants. Thus, the recombinant CEA molecules described should have numerous uses including validation of the use of monoclonal antibodies as standards in CEA serum assays, the characterization of immune responses to CEA, the use as immunogen, and the study of structure function relationships.

Generation and characterization of B72.3 second generation monoclonal antibodies reactive with the tumor-associated glycoprotein 72 antigen.

Monoclonal antibody (MAb) B72.3 was generated using a membrane-enriched fraction of a human mammary carcinoma biopsy. It has demonstrated reactivity to the majority of human adenocarcinomas including colorectal, gastric, pancreatic, ovarian, endometrial, mammary, and non-small cell lung cancer and no or weak reactivity to normal adult tissues, with the exception of secretory endometrium. The B72.3-reactive antigen, termed tumor-associated glycoprotein (TAG)-72, has been purified and used as an immunogen to generate B72.3 second generation MAbs. Since the source of purified TAG-72 was a human colon cancer (CC) xenograft, these MAbs have been given a CC designation. Twenty-eight CC MAbs, all immunoglobulin Gs, have been generated and shown to be reactive with TAG-72 and via both radioimmunoassay and immunohistochemical analyses show differential reactivity to carcinoma versus normal adult tissue biopsies. Nine CC MAbs (CC11, 15, 29, 30, 40, 46, 49, 83, and 92) were selected for further characterization. As a result of analyses using direct-binding radioimmunoassay to a range of human carcinomas, Western blotting, live cell surface binding assays, five liquid competition radioimmunoassays, and Ka measurements, all nine CC MAbs could be distinguished from each other and from B72.3. The Ka of B72.3 was determined to be 2.54 X 10(9) M-1; all the CC MAbs demonstrated higher KaS with MAbs CC92, 49, and 83 having KaS of 14.26, 16.18, and 27.72 X 10(9) M-1, respectively. These studies thus demonstrate that one or more of the anti-TAG-72 CC MAbs may be more efficient than B72.3, or useful in combination with B72.3, toward the further study of human carcinoma cell population and the diagnostic and therapeutic procedures presently utilizing MAb B72.3.

A CDR-grafted (humanized) domain-deleted antitumor antibody.

While several murine monoclonal antibodies (MAbs) directed against carcinoma associated antigens have shown excellent tumor targeting properties in clinical trials, the use of radiolabeled MAbs for both diagnostic and therapeutic applications has been hindered by two factors: (a) the induction of host anti-immunoglobulin (Ig) responses and (b) slow plasma clearance of unbound radiolabeled MAb, resulting in bone marrow toxicity for therapeutic application, and long intervals between MAb administration and tumor detection for diagnostic applications. This report describes the development of the first recombinant Ig with properties designed to reduce or eliminate both of the above problems: a complementarity determining region (CDR)-grafted humanized (Hu) MAb with a CH2 domain deletion (delta CH2). The MAb chosen for engineering was CC49, which is directed against a pancarcinoma antigen designated TAG-72 that is expressed on the majority of colorectal, gastric, breast, ovarian, prostate, pancreatic and lung carcinomas. When characterized for antigen binding in solid phase competition radioimmunoassays, the HuCC49 delta CH2 MAb completely inhibited the binding of murine (mu) CC49 and HuCC49 for TAG-72. The relative affinity constants (Ka) of MAbs HuCC49 delta CH2, HuCC49 and muCC49 were 5.1 x 10(-9), 2.1 x 10(-9) and 2.3 x 10(-9), respectively. The plasma clearance of 131I-HuCC49 delta CH2 was significantly faster than that of intact 125I-HuCC49 after either i.v. or i.p. administration in athymic mice (p(2)0.05). Biodistribution studies in athymic mice bearing human colon carcinoma xenografts after i.v. or i.p. administration of 131I-HuCC49 delta CH2 and 125I-HuCC49 demonstrated the efficient tumor localization and substantially lower percent of the injected dose (%ID/g) of the HuCC49 delta CH2 in normal tissues. This is reflected in the significantly higher radiolocalization indices (%ID/g in tumor divided by %ID/g in normal tissue) observed with the HuCC49 delta CH2 for most normal tissues tested (p(2)0.05). The differential between the rate of plasma clearance of HuCC49 delta CH2 and HuCC49 was even more pronounced in SCID mice, which have been shown to be an appropriate model to study the metabolism of human IgG. These studies thus describe the development of a recombinant Ig molecule which, for the first time, combines 1) the properties of more rapid blood clearance than an intact humanized Ig molecule--without loss of antigen binding affinity--and 2) reduced potential for eliciting a human anti-murine antibody (HAMA) response in patients. These studies also demonstrate the potential utility of HuCC49 delta CH2 for i.p. as well as i.v. radioimmunodiagnosis and radioimmunotherapy in patients with TAG-72 positive tumors.

A screening method for beta-lactams in tissues hydrolyzed with penicillinase I and lactamase II.

Antibiotic residues above tolerance levels are not allowed in foods derived from farm animals. Microbial inhibition assays are used to screen antibiotics in U.S. regulatory laboratories. We developed a screening approach to classify beta-lactams through selective hydrolysis of the beta-lactam ring with Penase or lactamase II, thereby inactivating the beta-lactam activity. Optimum conditions for hydrolysis of beta-lactams with Penase and lactamase II were determined. beta-Lactams were detected by a microbial inhibition assay and with enzyme-linked immunosorbent assays before and after hydrolysis. beta-Lactams (10-100 ppb) were spiked in kidney extracts and hydrolyzed. Results indicate a pattern that tentatively classified the beta-lactams into 3 subgroups. Desfuroyl-ceftiofur-cysteine, a major metabolite of ceftiofur, was clearly detected. Penicillin G, ampicillin, amoxicillin, and cloxacillin were distinguishable from cephapirin, ceftiofur metabolite, and high levels of hetacillin. Liver and kidney tissue samples were analyzed with the combined enzyme hydrolysis and screening assays, which tentatively identified the residues. This approach can speed up screening analysis of beta-lactam residues prior to identification and quantitation by chromatographic analysis, thus enhancing positive identification of residues to provide a safer food supply.

Long-term follow-up of prostate cancer patients treated with vaccine and definitive radiation therapy.

BACKGROUND: Vaccine therapy in combination with radiation therapy may improve distant and/or local control in prostate cancer. We present long-term follow-up data on the secondary and exploratory endpoints of safety and biochemical failure, respectively, from patients with clinically localized prostate cancer treated definitively with a poxviral vector-based therapeutic vaccine combined with external beam radiation therapy (EBRT). METHODS: Thirty-six prostate cancer patients received definitive EBRT plus vaccine. A total of 18 patients were treated with adjuvant standard-dose interleukin-2 (S-IL-2) (4 MIU m(-2)) and 18 were treated with very low-dose IL-2 (M-IL-2) (0.6 MIU m(-2)). Seven patients were treated with EBRT alone. Twenty-six patients treated with EBRT plus vaccine returned for follow-up, and we reviewed the most recent labs and clinical notes of the remaining patients. RESULTS: Median follow-up for the S-IL-2, M-IL-2 and EBRT-alone groups was 98, 76 and 79 months, respectively. Actuarial 5-year PSA failure-free probability was 78%, 82% and 86% (P=0.58 overall), respectively. There were no significant differences between the actuarial overall survival and the prostate cancer-specific survival between the two vaccine arms. Of the 26 patients who returned for follow-up, Radiation Therapy Oncology Group grade ≥2 genitourinary (GU) and gastrointestinal (GI) toxicity was seen in 19% and 8%, respectively, with no difference between the arms (P=1.00 and P=0.48 for grade ≥2 GU and GI toxicity, respectively). In all, 12 patients were evaluated for PSA-specific immune responses, and 1 demonstrated a response 66 months post-enrollment. CONCLUSIONS: We demonstrate that vaccine combined with EBRT does not appear to have significant differences with regard to PSA control or late-term toxicity compared with standard treatment. We also found limited evidence of long-term immune response following vaccine therapy.

Evaluation of human carcinoembryonic-antigen (CEA)-transduced and non-transduced murine tumors as potential targets for anti-CEA therapies.

The MC-38 C57BL/6 mouse colon adenocarcinoma cell line has been transduced with a retroviral construct containing cDNA encoding the human carcinoembryonic antigen (CEA) gene [Robbins PF, Kantor JA, Salgaller M, Horan Hand P, Fernsten PD, Schlom J (1991) Cancer Res 51: 3657]. Two clones, MC-38-ceal and MC-38-cea2, expressed high levels of CEA on their cell surface. A third CEA-expressing cell line, MCA-102-cea3, was similarly derived by transduction of the MCA-102 C57BL/6 mouse fibrosarcoma cell line and is described here. In this study, the three CEA-transduced murine tumor cell lines (MC-38-ceal, MC-38-cea2, MCA-102-cea3) were evaluated for their tumorigenic potential, as well as their ability to serve as in vivo model systems for active and passive immunotherapy studies. Parameters that were investigated include tumor growth rate, the antibody response of the host to CEA, and the CEA content of the tumors. The MC-38-cea2 model appeared to be the most appropriate for immunotherapy studies. Biodistribution studies, using an 125I-labeled anti-CEA mAb, demonstrated efficient tumor targeting of MC-38-cea2 tumors in C57BL/6 and athymic mice.

Continuous measurement of metals in flue gas using ICP-OES.

A system capable of continuously measuring a range of metallic elements in the effluent gas from incinerators and other similar industrial processes, and providing on-line results has been developed. With a state-of-the-art mobile laboratory measurements were taken from a UK municipal solid waste incinerator. The detection system used was an ICP-OES, with a modified torch to allow the introduction of flue gas directly into the plasma. Metals that were investigated were Ni, Hg, V, Al, Na, Ca, Cu, Sn, Pb, Sb, As, Cd and Tl, with limits of detection in the range 0.0004 mg m(-3) to 0.1 mg m(-3) being calculated. Emission measurements produced data that showed that the MSWI plants emission were significantly lower than the emission limits specified in EC 2000/76/EC.