Abstract 2546: Analysis of immune cell subsets in a multidrug therapeutic regimen for patients with metastatic castration-resistant prostate cancer

Purpose: To investigate the effects of docetaxel-based combination therapy with bevacizumab and dexamethasone premedication on the immune response in patients with metastatic castration-resistant prostate cancer (mCRPC).

Experimental Design: We studied immune responses in 13 patients enrolled in a phase II trial at the National Cancer Institute (NCI). The study was designed as a 13 patient expansion of a previously reported phase II study to evaluate the immunologic response after 2 cycles of treatment with a docetaxel-based chemotherapy regimen including docetaxel (75 mg/m2 every 3 weeks) and bevacizumab (15 mg/kg every 3 weeks). Dexamethasone pre-medication (4 mg) was given 12 h and 1 h prior to chemotherapy, and again after 12 h. Patients were evaluated before treatment and on day 40, 3 weeks after the second cycle. We compared PBMC and serum samples collected at baseline and after 40 days of treatment. We investigated CD4+ and CD8+ T-cells and regulatory T-cells (CD4+ CD25hi CD127- FoxP3+) by flow cytometry. T-cell proliferation, as well as NK-cell functional activity, was evaluated. Serum samples were analyzed for levels of cytokines, chemokines, sCD27, sCD40L and vascular endothelial growth factor (VEGF).

Results: The baseline characteristics were: median age 64 years, Gleason score 9, PSA 100 ng/ml, and Halabi Predicted Survival 10.6 months. Patients had a median PSA decline of 66% after 2 cycles. The median TTP was 14.1 months, and OS 18.7 months. At 3 weeks after the second cycle we found no significant changes in absolute lymphocyte count, CD4+ and CD8+ T-cell proliferation and NK-cell function. The number of CD4+ T-cells decreased. CTLA4+ regulatory T-cells did not change. There was no change in the serum levels of IL-6, IL-8, IL-10 and TNFα. As expected, the serum levels of VEGF decreased substantially after therapy. The serum levels of sCD40L did not change after treatment. Interestingly, an increase in the serum level of sCD27 correlated with longer OS (P= 0.037, R= 0.58).

Conclusions: Treatment of mCRPC patients with docetaxel-based combination therapy with bevacizumab and dexamethasone premedication for 40 days did not alter the immune response in a way that would decrease the likelihood of successful immunotherapy, either before or after this treatment.

Citation Format: Caroline Jochems, Benjamin Boyerinas, Ravi A. Madan, Diane J. Poole, Yang-Min Ning, William D. Figg, David J. Liewehr, Seth M. Steinberg, James L. Gulley, Kwong-Yok Tsang, Jeffrey Schlom. Analysis of immune cell subsets in a multidrug therapeutic regimen for patients with metastatic castration-resistant prostate cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2546. doi:10.1158/1538-7445.AM2014-2546

Effect of talactoferrin alfa on the immune system in adults with non-small cell lung cancer

BACKGROUND

Talactoferrin alfa (talactoferrin), an agent with immune-stimulating properties, has demonstrated safety and preliminary efficacy in clinical trials.

METHODS

Ten patients (five males and five females) with stage IV non-small cell lung cancer (NSCLC) in a single-arm pilot study received orally administered talactoferrin (1.5 g, b.i.d.) for up to 24 weeks. Radiographic and immunologic studies were performed at baseline and at weeks 6 and 12. Circulating immune cells (natural killer cells [NKCs], CD4+, CD8+, and regulatory T cells) and systemic cytokine levels were measured to assess immune response.

RESULTS

Patients enrolled in the study had received a median of four prior chemotherapy regimens, and all patients were symptomatic. Talactoferrin was well tolerated, with no grade 3 or 4 toxicities. Median time to progression (TTP) and overall survival were 6 weeks and 14.5 weeks, respectively. The four patients with ≥9 weeks TTP had evidence of immunologic activity (three with increased NKC activity).

CONCLUSIONS

The median of four previous chemotherapy regimens, with elevated levels of interleukin (IL) 6 and tumor necrosis factor-alfa in most patients, suggests these patients were poor candidates for immunotherapy.

Abstract 1260: Generation of human T cells directed against an agonist epitope of a transcription factor involved in epithelial to mesenchymal transition (EMT)

Purpose: The T-box family transcription factor Brachyury is overexpressed in a variety of human carcinomas, including lung, breast, colon, ovarian and prostate. Brachyury has been shown to promote epithelial to mesenchymal transition (EMT) in tumor cells, a critical step in the path to metastasis. An HLA-A2 epitope of Brachyury has been shown to expand human T cells that are capable of lysing Brachyury-expressing tumor cells in an HLA-dependent manner. This study sought to define an agonist of this epitope in order to increase T cell activation and tumor lysis.

Experimental Design: A novel agonist epitope of Brachyury was generated by residue substitution of the native epitope. Characterization of this epitope as an agonist included; comparison of HLA binding affinity and stability, interferon γ production by epitope-specific T cell lines, as well as Brachyury-and HLA-specific lysis of tumor cells. The presence of Brachyury-specific T cells that would recognize the agonist peptide, within the circulating PBMC of cancer patients, was determined by ELISPOT.

Results: The agonist epitope was shown to bind HLA-A2 with higher affinity and stability than the native. T cell lines generated from both the native and agonist epitopes produced higher levels of interferon γ in response to stimulation with the agonist epitope. The agonist-specific T cell line was able to lyse a variety of Brachyury-expressing tumor cells more efficiently than the T cell line generated with the native epitope, and specificity of lysis was confirmed by cold-target inhibition and HLA-A2 blocking. Tetramer staining revealed Brachyury agonist-specific T cells in the PBMC of a prostate cancer patient after in vitro stimulation with the agonist peptide. PBMC from colon and ovarian cancer patients reacted to the agonist peptide in an interferon γ ELISPOT assay.

Conclusions: An agonist epitope for Brachyury has been identified, which increased T cell activation and function as compared to the native epitope. T cells that react to the agonist peptide were detected in patients with carcinomas known to express high levels of Brachyury. This study supports the use of Brachyury as a cancer vaccine strategy, including the Brachyury agonist epitope.

Citation Format: Jo A. Tucker, Diane J. Poole, Claudia Palena, Caroline Jochems, Jeffrey Schlom, Kwong Y. Tsang. Generation of human T cells directed against an agonist epitope of a transcription factor involved in epithelial to mesenchymal transition (EMT). [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1260. doi:10.1158/1538-7445.AM2013-1260

Abstract 5379: Combination treatment with Bevacizumab, Lenalidomide, Docetaxel and Prednisone (ART-P) does not impact the immune response in patients with metastatic castration-resistant prostate cancer

Purpose: Investigation of the effect of combination therapy for 5 cycles with bevacizumab, lenalidomide, docetaxel and prednisone (ART-P) on the immune response in patients with metastatic castration-resistant prostate cancer (mCRPC). The aim was to ascertain if treatment containing prednisone and docetaxel would impact immune responses, which could compromise the efficacy of subsequent immunotherapy. Experimental Design: We report here a study of immune responses in 12 patients enrolled in a phase II trial of ART-P at the National Cancer Institute (NCI). We compared peripheral blood mononuclear cells (PBMC) and serum samples collected at baseline and post 5 3-week cycles of ART-P treatment. PBMCs were analyzed using flow cytometry to characterize phenotypes of T-cells, regulatory T-cells, myeloid derived suppressor cells (MDSC) and natural killer (NK) cells, and T-cell proliferation as well as NK-cell functional activity were evaluated. Serum samples were analyzed for levels of cytokines, chemokines and vascular endothelial growth factor (VEGF) with ELISA assays. Results: The baseline characteristics for the 12 patients were: median age 65.7 years, Gleason score 8, and PSA 74 ng/ml. Greater than 50% decreases in PSA were seen in 9/12 patients, with a median decrease of 74%. Of the 12 patients 7 had a partial response, and 5 had stable disease by RECIST criteria. After 5 cycles of ART-P treatment we found no significant differences from baseline in T-cell proliferation and NK-cell function, or the frequencies of T-cells, regulatory T-cells, MDSC and NK-cells. There was also no change in the serum levels of cytokines and chemokines except for IL-6, which decreased. As expected, the serum levels of VEGF substantially decreased with therapy. Conclusions: Treatment of mCRPC patients with ART-P for 5 cycles did not alter the immune response in a way that would decrease the likelihood of successful immunotherapy, pre or post treatment with ART-P.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5379. doi:1538-7445.AM2012-5379

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.

Ipilimumab and a poxviral vaccine targeting prostate-specific antigen in metastatic castration-resistant prostate cancer: a phase 1 dose-escalation trial

BACKGROUND

Therapeutic cancer vaccines have shown activity in metastatic castration-resistant prostate cancer (mCRPC), and methods are being assessed to enhance their efficacy. Ipilimumab is an antagonistic monoclonal antibody that binds cytotoxic T-lymphocyte-associated protein 4, an immunomodulatory molecule expressed by activated T cells, and to CD80 on antigen-presenting cells. We aimed to assess the safety and tolerability of ipilimumab in combination with a poxviral-based vaccine targeting prostate-specific antigen (PSA) and containing transgenes for T-cell co-stimulatory molecule expression, including CD80.

METHODS

We did a phase 1 dose-escalation trial, with a subsequent expansion phase, to assess the safety and tolerability of escalating doses of ipilimumab in combination with a fixed dose of the PSA-Tricom vaccine. Patients with mCRPC received 2×10(8) plaque-forming units of recombinant vaccinia PSA-Tricom subcutaneously on day 1 of cycle 1, with subsequent monthly boosts of 1×10(9) plaque-forming units, starting on day 15. Intravenous ipilimumab was given monthly starting at day 15, in doses of 1, 3, 5, and 10 mg/kg. Our primary goal was to assess the safety of the combination. This study is registered with ClinicalTrials.gov, number NCT00113984.

FINDINGS

We completed enrolment with 30 patients (24 of whom had not been previously treated with chemotherapy) and we did not identify any dose-limiting toxic effects. Grade 1 and 2 vaccination-site reactions were the most common toxic effects: three of 30 patients had grade 1 reactions and 26 had grade 2 reactions. 21 patients had grade 2 or greater immune-related adverse events. Grade 3 or 4 immune-related adverse events included diarrhoea or colitis in four patients and grade 3 rash (two patients), grade 3 raised aminotransferases (two patients), grade 3 endocrine immune-related adverse events (two patients), and grade 4 neutropenia (one patient). Only one of the six patients previously treated with chemotherapy had a PSA decline from baseline. Of the 24 patients who were chemotherapy-naive, 14 (58%) had PSA declines from baseline, of which six were greater than 50%.

INTERPRETATION

The use of a vaccine targeting PSA that also enhances co-stimulation of the immune system did not seem to exacerbate the immune-related adverse events associated with ipilimumab. Randomised trials are needed to further assess clinical outcomes of the combination of ipilimumab and vaccine in mCRPC.

FUNDING

US National Institutes of Health.

Abstract 5524: Generation of cellular immune responses to MUC1-C to target the portion of MUC1 that is most biologically relevant to the transformation process

MUC1 is overexpressed in diverse human carcinomas and hematological cancers, and therefore serves as a potential target for immunotherapy. The MUC1 molecule has two distinctive subunits, formed by autocleavage with a SEA domain. The N-terminal (MUC1-N) is the large extracellular domain, and the C-terminal (MUC1-C) has three subunits: a small extracellular domain that is covalently bound to MUC1-N, a single transmembrane domain and a cytoplasmic tail. It has been reported by Kufe et al that the MUC1-C subunit transduces signals that confer growth and survival responses. The MUC1-C cytoplasmic tail located downstream of the SEA domain is sufficient for the induction of anchorage independent growth and tumorigenicity. MUC1-C overexpression is also highly associated with poor prognosis in patients with lung cancer and breast cancer. We and others have previously reported on HLA-A2 binding agonist epitopes to MUC1-N. The objective of this investigation is to identify and characterize HLA-A3 binding cytotoxic T-lymphocyte (CTL) epitopes and agonist epitopes of the MUC1-C subunit. The intention is to add these peptides to vaccines against MUC1 positive carcinomas, as well as using them for monitoring patients’ immune responses in clinical MUC1 vaccine trials. The generation of cellular immune responses to MUC1-C would thus target the portion of MUC1 that is most biologically relevant to the transformation process.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5524. doi:10.1158/1538-7445.AM2011-5524

Immunologic and prognostic factors associated with overall survival employing a poxviral-based PSA vaccine in metastatic castrate-resistant prostate cancer

A concurrent multicenter, randomized Phase II trial employing a recombinant poxviral vaccine provided evidence of enhanced median overall survival (OS) (p = 0.0061) in patients with metastatic castrate-resistant prostate cancer (mCRPC). The study reported here employed the identical vaccine in mCRPC to investigate the influence of GM-CSF with vaccine, and the influence of immunologic and prognostic factors on median OS. Thirty-two patients were vaccinated once with recombinant vaccinia containing the transgenes for prostate-specific antigen (PSA) and three costimulatory molecules. Patients received boosters with recombinant fowlpox containing the same four transgenes. Twelve of 32 patients showed declines in serum PSA post-vaccination and 2/12 showed decreases in index lesions. Median OS was 26.6 months (predicted median OS by the Halabi nomogram was 17.4 months). Patients with greater PSA-specific T-cell responses showed a trend (p = 0.055) toward enhanced survival. There was no difference in T-cell responses or survival in cohorts of patients receiving GM-CSF versus no GM-CSF. Patients with a Halabi predicted survival of <18 months (median predicted 12.3 months) had an actual median OS of 14.6 months, while those with a Halabi predicted survival of > or =18 months (median predicted survival 20.9 months) will meet or exceed 37.3 months, with 12/15 patients living longer than predicted (p = 0.035). Treg suppressive function was shown to decrease following vaccine in patients surviving longer than predicted, and increase in patients surviving less than predicted. This hypothesis-generating study provides evidence that patients with more indolent mCRPC (Halabi predicted survival > or =18 months) may best benefit from vaccine therapy.

Pilot study of vaccination with recombinant CEA-MUC-1-TRICOM poxviral-based vaccines in patients with metastatic carcinoma

PURPOSE

Poxviral vectors have a proven safety record and can be used to incorporate multiple transgenes. Prior clinical trials with poxviral vaccines have shown that immunologic tolerance to self-antigens can be broken. Carcinoembryonic antigen (CEA) and MUC-1 are overexpressed in a substantial proportion of common solid carcinomas. The primary end point of this study was vaccine safety, with immunologic and clinical responses as secondary end points.

EXPERIMENTAL DESIGN

We report here a pilot study of 25 patients treated with a poxviral vaccine regimen consisting of the genes for CEA and MUC-1, along with a triad of costimulatory molecules (TRICOM; composed of B7.1, intercellular adhesion molecule 1, and lymphocyte function-associated antigen 3) engineered into vaccinia (PANVAC-V) as a prime vaccination and into fowlpox (PANVAC-F) as a booster vaccination.

RESULTS

The vaccine was well tolerated. Apart from injection-site reaction, no grade > or =2 toxicity was seen in more than 2% of the cycles. Immune responses to MUC-1 and/or CEA were seen following vaccination in 9 of 16 patients tested. A patient with clear cell ovarian cancer and symptomatic ascites had a durable (18-month) clinical response radiographically and biochemically, and one breast cancer patient had a confirmed decrease of >20% in the size of large liver metastasis.

CONCLUSIONS

This vaccine strategy seems to be safe, is associated with both CD8 and CD4 immune responses, and has shown evidence of clinical activity. Further trials with this agent, either alone or in combination with immunopotentiating and other therapeutic agents, are warranted.

Clinical safety of a viral vector based prostate cancer vaccine strategy

PURPOSE

The primary objective of this phase I study was to evaluate the clinical safety of a vaccine using recombinant vaccinia virus (prime) and recombinant fowlpox virus (boost) in combination with granulocyte-macrophage colony-stimulating factor in patients with prostate cancer. The vaccines contained transgenes for prostate specific antigen, a triad of co-stimulatory molecules and a tumor antigen whose amino acid sequence had been modified to enhance its immunogenicity. Secondary end points were immunological and clinical responses, changes in prostate specific antigen velocity, and the kinetics of vaccinia virus clearance from the vaccination site, serum, peripheral blood mononuclear cells, urine and saliva.

MATERIALS AND METHODS

The 15 patients enrolled in this study had metastatic prostate cancer. Patients were given recombinant fowlpox-prostate specific antigen/triad of co-stimulatory molecules alone or recombinant vaccinia-prostate specific antigen/triad of co-stimulatory molecules followed by recombinant fowlpox-prostate specific antigen/triad of co-stimulatory molecules on a prime and boost schedule with or without recombinant-granulocyte-macrophage colony-stimulating factor protein or recombinant fowlpox-granulocyte-macrophage colony-stimulating factor vector. Prostate specific antigen specific immune responses were measured using an enzyme-linked immunosorbent spot assay for interferon-gamma production. Polymerase chain reaction for vaccinia DNA and a plaque assay for live virus were also used.

RESULTS

Some grade 2 toxicity was seen in patients who received a higher dose of recombinant fowlpox-granulocyte-macrophage colony-stimulating factor but no toxicity exceeded grade 2. Viable vaccinia was detected after vaccination at the site swab of 1 of 4 patients analyzed. Prostate specific antigen specific immune responses were seen in 4 of 6 patients who were HLA-A2+ and decreases in serum prostate specific antigen velocity were observed in 9 of 15.

CONCLUSIONS

Based on the safety and preliminary immunogenicity results of this trial we recommend initiating a randomized, phase II study of prostate specific antigen/triad of co-stimulatory molecules vaccines in patients with less advanced prostate cancer.

Modified vaccinia virus ankara recombinants are as potent as vaccinia recombinants in diversified prime and boost vaccine regimens to elicit therapeutic antitumor responses

Cancer vaccine regimens use various strategies to enhance immune responses to specific tumor-associated antigens (TAAs), including the increasing use of recombinant poxviruses [vaccinia (rV) and fowlpox (rF)] for delivery of the TAA to the immune system. However, the use of replication competent vectors with the potential of adverse reactions have made attenuation a priority for next-generation vaccine strategies. Modified vaccinia Ankara (MVA) is a replication defective form of vaccinia virus. Here, we investigated the use of MVA encoding a tumor antigen gene, carcinoembryonic antigen (CEA), in addition to multiple costimulatory molecules (B7-1, intercellular adhesion molecule-1, and lymphocyte function-associated antigen-3 designated TRICOM). Vaccination of mice with MVA-CEA/TRICOM induced potent CD4+ and CD8+ T-cell responses specific for CEA. MVA-CEA/TRICOM could be administered twice in vaccinia naïve mice and only a single time in vaccinia-immune mice before being inhibited by antivector-immune responses. The use of MVA-CEA/TRICOM in a diversified prime and boost vaccine regimen with rF-CEA/TRICOM, however, induced significantly greater levels of both CD4+ and CD8+ T-cell responses specific for CEA than that seen with rV-CEA/TRICOM prime and rF-CEA/TRICOM boost. In a self-antigen tumor model, the diversified MVA-CEA/TRICOM/rF-CEA/ TRICOM vaccination regimen resulted in a significant therapeutic antitumor response as measured by increased survival, when compared with the diversified prime and boost regimen, rV-CEA/TRICOM/rF-CEA/TRICOM. The studies reported here demonstrate that MVA, when used as a prime in a diversified vaccination, is clearly comparable with the regimen using the recombinant vaccinia in both the induction of cellular immune responses specific for the "self"-TAA transgene and in antitumor activity.

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.

Vaccine therapy of established tumors in the absence of autoimmunity

PURPOSE

Many current clinical trials involve vaccination of patients with vaccines directed against tumor-associated antigens, which are, in actuality, "self-antigens" overexpressed in tumors as compared with normal tissues. As tumor vaccines become more potent through the addition of costimulatory molecules and cytokines and the use of diversified prime and boost regimes, the level of concern rises regarding the balance between antitumor immunity and pathological autoimmunity. Studies were conducted using mice bearing a transgenic self-antigen [human carcinoembryonic antigen (CEA)], which is expressed in some normal adult tissues, and tumor expressing the same self-antigen. These mice were vaccinated with recombinant poxviral vectors [recombinant vaccinia, recombinant fowlpox (rF)] encoding the CEA transgene as well as a triad of costimulatory molecules [B7-1, ICAM-1, and LFA-3 (TRICOM)]. Here we investigate the mechanism of tumor therapy and evaluate the safety of such a regimen in a self-antigen system. To our knowledge, the study reported here is the first description of a vaccine to a defined antigen where the regimen is potent enough to induce tumor therapy in the absence of autoimmunity.

EXPERIMENTAL DESIGN

CEA transgenic mice were transplanted with CEA-expressing tumors. Fourteen days later, mice were vaccinated with recombinant vaccinia-CEA/TRICOM admixed with recombinant murine granulocyte macrophage colony-stimulating factor and then given low-dose interleukin 2. Mice were boosted on days 21, 28, and 35 with rF-CEA/TRICOM admixed with rF-granulocyte macrophage colony-stimulating factor and then given low-dose interleukin 2. Mice were monitored for survival and compared with groups of mice vaccinated in a similar manner with poxviral vectors containing CEA/B7-1 or CEA transgenes. To determine the mechanism of antitumor therapy, mice were depleted of T-cell subpopulations before vaccination with the CEA/TRICOM regimen. Mice successfully cured of tumor and age-matched control mice were monitored for 1 year. At 1 year, several clinical assays were carried out involving analysis of 9 serological parameters, 11 urinalysis parameters, and 14 immunological parameters. In addition, histopathology was performed on 42 tissues/mouse.

RESULTS

The CEA/TRICOM vaccination regimen induced a therapeutic antitumor response as measured by increased survival, which was due largely to induced T-cell responses (both CD4(+) and CD8(+)) as determined by selective T-cell subset depletion. The CEA/TRICOM vaccination regimen induced a significant increase in proliferation of CD4(+) T cells to CEA protein and a significant increase in secretion of IFN-gamma from CD8(+) T cells in response to a defined CEA epitope. Despite CEA expression in normal adult gastrointestinal tissues, no toxicity was observed in the CEA/TRICOM-vaccinated group when an array of clinical serum and urine chemistry assays was conducted 1 year after vaccination. Moreover, a comprehensive histopathological evaluation of all tissues from these groups also showed no evidence of toxicity.

CONCLUSIONS

Activation of T cells directed against a tumor-associated self-antigen, sufficient to mediate therapeutic antitumor immunity, was observed in vivo without the development of autoimmunity as analyzed by a comprehensive evaluation of biochemical, immunological, and histopathological criteria. These studies demonstrate that the use of vectors containing as many as three costimulatory molecules does not induce autoimmunity or other pathology. These studies thus demonstrate that a balance can indeed be achieved between the induction of an immune response to a self-antigen, which is capable of antitumor therapy, and the absence of autoimmunity.

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.

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.

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.

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.

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.

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.