Development of anti-idiotypic antibodies against tumour antigens and autoantigens in ovarian cancer patients treated intraperitoneally with mouse monoclonal antibodies

Application of Genetically-Engineered Anti-CEA Antibodies for Potential Immunotherapy of Colorectal Cancer

Hitherto anti-CEA monoclonal antibodies (MAbs), normally of mouse origin, have been used primarily for clinical diagnosis of colorectal cancer, either as a tumor marker in serum to monitor tumor recurrence, or latterly as a means to localize in vivo CEA-bearing tumors and metastases in patients. In vivo diagnosis using mouse anti-CEA MAbs has so far had limited clinical utility because the antibodies elicit a strong anti-mouse immunoglobulin immune response on repeated administration in man. This problem has been addressed by the development of various strategies for “humanization” of mouse anti-CEA MAbs by genetic manipulation of immunoglobulin genes. Such humanized, engineered antibodies markedly attenuate the antigenic response directed against the MAb, such that safe, repeated administration to patients has become feasible. Such humanized anti-CEA antibodies can thus be radioactively-labelled and applied for in vivo monitoring and detection of recurrent malignant disease, or used for therapeutic strategies which similarly take advantage of the ability of the antibodies to target cytotoxic agents selectively to tumor cells. The application of these novel procedures for manipulating MAb structure presents entirely new opportunities for diagnosis and treatment of human colorectal cancer.

Predictors of long-term outcome from intraperitoneal radioimmunotherapy for ovarian cancer

Data was analyzed from 92 patients >  5 years after intraperitoneal (IP) radionuclide therapy (RIT) with (90)Y- or (177)Lu-CC49 to determine prognostic factors. Patients had CC49 antibody-reactive ovarian cancer confined to the abdominal cavity after primary debulking and chemotherapy. The first 27 patients received IP (177)Lu-CC49 alone; the remainder received Interferon (IFN), to increase the expression of the tumor-associated glycoprotein-72 (TAG-72) antigen, +/- IP paclitaxel (25-100 mg/m(2)) 2 days before RIT. Factors assessed by univariate (and some multivariate) analysis included age, race, body size, interval between initial diagnosis and RIT, interval between 2nd look surgery and RIT, (90)Y versus (177)Lu, MBq dose, paclitaxel dose, grade of tumor, extent of initial surgery, size of disease deposits prior to RIT, intensity of TAG reactivity, the addition of unlabeled antibody, and the development of human anti-mouse antibody and/or serum sickness after murine antibody. A statistically significant improvement in progression-free survival (p ≤ 0.05) was noted for less bulky disease and younger age. Administration of paclitaxel plus IFN, an immune response, and use of (90)Y showed a favorable nonsignificant trend. Dose escalation of radionuclide did not change risk of progression; thus, this therapy may have therapeutic efficacy at modest dose levels.

Natural and Induced Humoral Responses to MUC1

MUC1 is a membrane-tethered mucin expressed on the ductal cell surface of glandular epithelial cells. Loss of polarization, overexpression and aberrant glycosylation of MUC1 in mucosal inflammation and in adenocarcinomas induces humoral immune responses to the mucin. MUC1 IgG responses have been associated with a benefit in survival in patients with breast, lung, pancreatic, ovarian and gastric carcinomas. Antibodies bound to the mucin may curb tumor progression by restoring cell-cell interactions altered by tumor-associated MUC1, thus preventing metastatic dissemination, as well as counteracting the immune suppression exerted by the molecule. Furthermore, anti-MUC1 antibodies are capable of effecting tumor cell killing by antibody-dependent cell-mediated cytotoxicity. Although cytotoxic T cells are indispensable to achieve anti-tumor responses in advanced disease, abs to tumor-associated antigens are ideally suited to address minimal residual disease and may be sufficient to exert adequate immune surveillance in an adjuvant setting, destroying tumor cells as they arise or maintaining occult disease in an equilibrium state. Initial evaluation of MUC1 peptide/glycopeptide mono and polyvalent vaccines has shown them to be immunogenic and safe; anti-tumor responses are scarce. Progress in carbohydrate synthesis has yielded a number of sophisticated substrates that include MUC1 glycopeptide epitopes that are at present in preclinical testing. Adjuvant vaccination with MUC1 glycopeptide polyvalent vaccines that induce strong humoral responses may prevent recurrence of disease in patients with early stage carcinomas. Furthermore, prophylactic immunotherapy targeting MUC1 may be a strategy to strengthen immune surveillance and prevent disease in subjects at hereditary high risk of breast, ovarian and colon cancer.

Induction of IgG antibodies to MUC1 and survival in patients with epithelial ovarian cancer

We investigated whether epithelial ovarian cancer patients participating in a randomized phase III trial comparing single intraperitoneal (IP) administration of yttrium-90-labeled murine HMFG1 ((90)Y-muHMFG1) plus standard treatment (AT) vs. standard treatment (ST) alone developed IgG ab to MUC1 that had an impact on disease outcome. Serial serum samples from 208 patients in the AT and 199 patients in the ST arm were tested for IgG ab to MUC1 (anti-MUC1 IgG). Anti-MUC1 IgG at weeks 4, 8 and 12 ranked higher in the AT than in the ST arm (p < 0.001). The median (range) area under the curve (AUC) of anti-MUC1 IgG for weeks 1 to 12 was 5.53 (1.51-39.51) and 3.92 (1.17-68.74) for the AT and ST arm, respectively (p < 0.001). An anti-MUC1 IgG AUC > 13 was associated with a benefit in overall survival (OS) and disease-free survival (DFS) in the AT arm in univariate (p = 0.043 and 0.036, respectively), but not in multivariate analysis (Cox proportional hazards regression model). Kaplan-Meier analysis showed a benefit in OS and DFS in patients with an anti-MUC1 IgG AUC > 13 in the AT arm (p = 0.043 and 0.036, respectively), but not in the ST arm. A single IP injection with muHMFG1 did not lead to a survival benefit in the randomized trial, but it induced ab to MUC1 that were associated with an improved disease outcome in patients with highest levels of anti-MUC1 IgG. Immunotherapy against MUC1 could be effective in the treatment of epithelial ovarian cancer.

The immunology of colorectal cancer

Despite the fact that the vast majority of differentiated colorectal cancers express tumour-associated antigens (TAA's) such as Carcinoembryonic antigen (CEA) and Ep-CAM, the immune response particularly in advanced disease is often attenuated. This may result from clonal immunocyte energy to oncofetal antigens normally expressed during cell development, immune complex disease where the TAA is repeatedly shed into the circulation and tumour-induced impairments in T cell receptor recognition and stimulation. Commonly used monoclonal anti-TAA antibody therapy is also hampered by human anti-xenogeneic antibody production and by the physical distribution of the antibody into the center of tumour deposits where blood flow is limited and where tumour neovasculature is hyperpermeable. Moreover, animal models of colorectal cancer should be assessed carefully since CEA is not normally expressed, requiring the transduction of CEA cDNA into tumour xenografts or the creation of transgenic species where the mechanisms of tumour rejection are still governed by non-human antigenic histoincompatibility. All of this has resulted in the generation of novel immune constructs designed to enhance the inherent immunogenicity of colorectal cancer, using antigenic viral genomes or cytokine transduction methodology as well as the ex vivo stimulation of dendritic antigen-presenting cells or autologous tumour-infiltrating lymphocytes. Even these powerful strategies may be foiled by intratumoural mechanisms which result in excessive apoptosis of infused cells even when they have been shown in vitro to be immunocompetent and tumour-specific. This review discusses these immune approaches in colorectal cancer and their inherent limitations.

Monoclonal antibodies in solid tumours: approaches to therapy with emphasis on gynaecological cancer

Monoclonal antibodies have progressed from the laboratory to the clinic. Although recognised in diagnosis there are still problems as far as their therapeutic use is concerned. This review looks at the history, principles of active specific immunotherapy, clinical experience with monoclonal antibodies in therapy of solid tumours, in particular the development of new bispecific monoclonal antibodies, and trials in ovarian, breast and colorectal cancer. Immunoconjugates, linked with radionuclides and cytotoxic drugs, indicate future developments. Conditions for successful therapy, especially with adjuvants in patients with small tumour residues, are also described.

Prospects of radioimmunotherapy in epithelial ovarian cancer: results with iodine-131-labeled murine and humanized MN-14 anti-carcinoembryonic antigen monoclonal antibodies

OBJECTIVES

Epithelial ovarian cancer (EOC) is known to produce carcinoembryonic antigen (CEA), and the plasma CEA level is frequently elevated in patients with advanced stage and bulk of tumor. This study reports the results of a phase I therapy trial with intravenously administered 131I-MN-14 anti-CEA monoclonal antibody (MAb) in patients with EOC.

METHODS

Fourteen patients with advanced refractory EOC were given escalating intravenous doses (two received 30 mCi/m2, six 40 mCi/m2, and six 50 mCi/m2) of 131I-MN-14 IgG. All patients received a diagnostic study with 8 mCi (0.6 mg) of 131I-MN-14 IgG 1 week prior to their therapy infusion. Tumor targeting was assessed by external scintigraphy, toxicity according to the Radiation Therapy Oncology Group criteria, and therapy responses by CT and serum CA-125.

RESULTS

The MAb scan was positive in all 14 treated patients. Myelosuppression was the only observed treatment-related toxicity. Dose-limiting toxicity, defined as grade 4 leukopenia or thrombocytopenia of any duration, or grade 3 leukopenia or thrombocytopenia of > 2 weeks, was not seen at the 30 or 40 mCi/m2 dose levels. However, 2 of 6 patients treated at 50 mCi/m2 had a grade 4 thrombocytopenia or a grade 3 thrombocytopenia lasting 18 days. Of the 14 patients, 1 with diffuse peritoneal implants of < or = 2 cm had a complete clinical remission by CT and CA-125 for 8 months, following an initial partial remission for 10 months, both at the 40 mCi/m2 dose level. Another patient had a mixed response for 1 month.

CONCLUSION

MN-14 anti-CEA MAb is a suitable agent for tumor targeting and may have a therapeutic potential in patients with chemotherapy-refractive EOC, especially those with minimal disease.

Are human anti-idiotypic anti-OC125 antibodies formed after immunization with the anti-CA125 antibody B43.13?

The two monoclonal antibodies (MAb) OC125 and B43.13 both recognize antigenic determinants on the cancer antigen 125 (CA125) molecule. The aim of the present study was to clarify how far antibodies formed by patients treated with B43.13 may cross-react with idiotopes of OC125. Serum samples from 15 ovarian cancer patients treated with B43.13 were tested for the presence of anti-idiotypic anti-OC125 antibodies; 4 of these patients previously had received OC125 F(ab')2 fragments. Six patients treated only with B43.13 and all patients pretreated with OC125 fragments developed a considerable increase of human anti-mouse anti-bodies after B43.13 infusion, indicating an immune response to antibody infusion. However, none of the patients treated only with B43.13 developed detectable levels of anti-idiotypic anti-OC125 antibodies, whereas in 2 patients pretreated with OC125 fragments, the pre-existing concentration of anti-idiotypic anti-OC125 antibodies further increased after B43.13 infusion. The binding of these newly formed antibodies to OC125 was not inhibited by the B43.13, but about 70% of the binding was inhibited by the CA125 antigen. The present data suggest that the idiotopes expressed on the antibodies B43.13 and OC125, respectively, are completely different. Thus, anti-idiotypic anti-B43.13 antibodies may not cross-react with OC125. A greater number of cases is needed to clarify how far the increase of anti-idiotypic anti-OC125 antibodies observed in 2 patients pretreated with OC125 fragments really is due to B43.13 infusion.

Anti-TAG-72 antibody B72.3--immunological and clinical effects in ovarian carcinoma

Based on the network theory, anti-tumor antibodies (Ab1) can trigger the immune system of the host into a response against tumor cells. Through an immunological cascade, anti-idiotypic antibodies bearing the internal image of epitopes of the nominal antigen (Ab2 beta) are produced that themselves can induce cellular and humoral cytotoxic effects against the antigen-expressing tumor cell. Formation of such antibodies has been shown to be associated with prolonged survival of melanoma, colorectal, and ovarian carcinoma patients. We studied anti-idiotypic antibody (Ab2) responses and clinical outcome of 31 ovarian cancer patients receiving the monoclonal antibody (MAb) B72.3, which targets the ovarian carcinoma associated antigen TAG-72. All patients were treated by surgery and polychemotherapy, which was followed by repeated (mean of 4) injections of 1 mg of the MAb B72.3. A remarkable anti-idiotypic anti-B72.3 response arose in 19 patients, with 9 of them showing a major response with Ab2 serum concentrations greater than 1,000 U/ml ("high-responders"). The median disease-free survival time, as well as the median survival time of these high-responders, was increased as compared to the low- or no responders. Evaluating our data, we conclude that monoclonal antibody treatment with the MAb B72.3 may induce humoral immunological responses in about two-thirds of our study group, although a positive clinical effect may only be expected in patients with excessive anti-idiotypic antibody formation.

Humoral immune response to polymorphic epithelial mucin (MUC-1) in patients with benign and malignant breast tumours

To investigate the clinical significance of an immune response to the MUC-1 encoded polymorphic epithelial mucin (PEM) breast cancer, circulating immune complexes containing PEM (PEM.CIC) were measured in sera from 96 healthy women, in pretreatment serum samples from 40 patients with benign breast tumours and from 140 patients with breast cancer and in serum samples from 61 breast cancer patients with recurrent or progressive disease. PEM.CIC were measured using a sandwich enzyme-linked immunoassay, and PEM serum levels were measured with CA 15.3 IRMA (Centocor Inc., Malvern, Pennsylvania, U.S.A.). Cut-off levels used for PEM.CIC and CA 15.3 were 120 Optical Density Units (O.D.) x 10(3) and 30 U/ml, respectively. In benign tumours, positivity for PEM.CIC was 37.5% (15/40). 36 of the 140 patients (25.7%) in the breast cancer pretreatment group had elevated PEM.CIC values. In patients with advanced metastatic disease, positivity for PEM.CIC was 18% (11/61). PEM.CIC was elevated in 32% (24/74) of node-negative patients, but only in 20% (12/59) of node-positive patients and absolute values were higher in node-negative patients (Mann-Whitney U test, two-tailed P = 0.0168). There was an inverse correlation between positivity for PEM.CIC and extent of disease: while 3 of the 6 patients with a carcinoma in situ were positive, only 1 of the 15 patients with more than five nodes involved had elevated levels of PEM.CIC. All 7 patients with distant metastases at first diagnosis were PEM.CIC negative. 28 out of 133 patients had a recurrence during the observation period (median 55 months, range 27-84 months). 23 of these 28 patients (82%) were PEM.CIC negative at the moment of first diagnosis. None of the patients with pretreatment elevation of both PEM.CIC and CA 15.3 (n = 13) relapsed. Our preliminary clinical results suggest that a humoral immune response to PEM protects against disease progression, and further support the idea of using synthetic peptides or glycopeptides containing the immunogenic core of the mucin as cancer vaccines.

A simple and sensitive assay for determination of human anti-idiotypic anti-B72.3 antibodies, which is not affected by the presence of tumour-associated glycoprotein 72

An immunoradiometric assay is described for the determination of human anti-idiotypic anti-B72.3 IgG. The latter is formed in ovarian cancer patients after treatment with the murine monoclonal antibody B72.3, which is directed against the tumour-associated glycoprotein 72 (TAG-72). A gel coupled with Fc-specific anti-human IgG antibodies is used as a solid phase for the extraction of serum IgG. The anti-B72.3 IgG is then specifically detected by incubation with radiolabelled B72.3 detector antibodies. Calibration standards were prepared from serum obtained from a patient repeatedly treated with B72.3 antibodies. The concentration of anti-idiotypic anti-B72.3 antibodies was expressed as TAG-72-like arb.units/1. The assay performed with two 60-minute incubation steps is characterized by a high sensitivity (detection limit: 3 x 10(3) arb.units/1) and precision (coefficients of variation: intra-assay = 6.4% and 5.8% at 80 x 10(3) arb. units/1 and 217 x 10(3) arb.units/1, inter-assay = 8.7% and 7.1% at 91 x 10(3) arb.units/1 and 212 x 10(3) arb.units/1) and a good linearity of dilution (recovery after dilution between 99% and 107%). The assay is more specific than previously described methods; no interference was observed by TAG-72 up to 3.3 x 10(7) arb.units/1. Also, non-specific human anti-mouse antibodies did not cross-react up to 34.8 mg/l. The test may be modified for detection of anti-idiotypic antibodies, which are formed after treatment with other monoclonal antibodies.

Monoclonal antibodies used in the detection and treatment of epithelial ovarian cancer

Conventional therapy for epithelial ovarian cancer, including aggressive cytoreductive surgery followed by combination chemotherapy regimens, has failed to reduce the number of deaths caused by this disease, which remains the most lethal of gynecologic malignancies. Monoclonal antibodies, which offer the promise of high selectivity for detection and therapy, may be targeted to tumor-associated antigens, growth factors, receptors, or oncogenes. They may be used alone as immunotherapeutic agents or conjugated to chemotherapeutic drugs, toxins, or radionuclides. Radioimmunoconjugates may also be used for preoperative or intraoperative tumor localization. The authors focused on the clinical utility, technical limitations, and potential of monoclonal antibodies in the detection and treatment of epithelial ovarian cancer with emphasis on radioimmunodetection and radioimmunotherapy.

Antiidiotypic antibodies in ovarian cancer patients treated with the monoclonal antibody B72.3

Immunotherapy with monoclonal antibodies has become a hopeful approach to the adjuvant therapy of cancer patients. Recently, formation of antiidiotypic antibodies (Ab2) has been demonstrated in ovarian cancer patients after immunization with F(ab')2 fragments of the monoclonal antibody OC 125 (MAb OC 125). Preliminary results suggested that patients with high Ab2 serum concentrations had better survival rates compared to those where low or no Ab2 serum levels were detected. Beginning in 1992, 23 patients with advanced ovarian adenocarcinomas have been treated with repeated intravenous applications of the MAb B72.3, which is directed against the ovarian carcinoma associated antigen TAG-72. Five of them had been pretreated with several F(ab')2 MAb OC 125 infusions. Blood sample analysis revealed a remarkable antiidiotypic antibody (Ab2) response in 14 patients, with five patients developing high serum levels > 1000 U/ml. Ab2 serum concentrations increased with increasing number of Mab B72.3 applications. In terms of serum levels, corresponding antiidiotypic antibody responses in patients who received both the F(ab')2 MAb OC 125 and the MAb B72.3 differed considerably. We conclude that the use of MAb B72.3 may be an additional beneficial approach to the immunological therapy of ovarian cancer. Subsequent MAb B72.3 application after failure of the F(ab')2 MAb OC 125 may induce appreciable Ab2 serum concentrations and vice versa.

Inhibition of bispecific monoclonal antibody (bsAb)-targeted cytolysis by human anti-mouse antibodies in ovarian carcinoma patients treated with bsAb-targeted activated T-lymphocytes

T lymphocytes of 8 patients with ovarian cancer were targeted to the tumor cells using F(ab')2 fragments of a bispecific monoclonal antibody (bsAb), specific for CD3 (a component of the T lymphocyte receptor for antigen) and for the folate receptor MOv18 (overexpressed by ovarian carcinoma cells) as part of a phase I/II study. Phase I (days 0 to 3) consisted of increasing intraperitoneal (i.p.) numbers (10(6)-10(9)) of bsAb-targeted T lymphocytes plus low-dose interleukin-2 (IL-2). Phase II (days 6 to 13, and 27 to 33) consisted of daily i.p. infusions of 10(9) targeted T lymphocytes, 2 mg soluble bsAb, and low-dose IL-2. Using enzyme-linked immunosorbent assays (ELISA), human anti-mouse antibodies (HAMA) were detected in all patients: in the serum from day 13 onwards and in the peritoneal fluid from day 20 onwards. A significant proportion of the HAMA appeared to be directed against the idiotypes of the bsAb specific for CD3 and MOv18, as suggested by (1) the clearly higher ELISA titers against OC/TR bsAb as compared to those against a monoclonal antibody (MAb) with unrelated specificity, and (2) failure to abrogate the capacity of peritoneal fluid containing HAMA to block the binding of OC/TR bsAb to MOv18+ or CD3+ cells by absorption of human anti-mouse IgG-framework antibodies in peritoneal fluid to immobilized mouse IgG. The OC/TR-targeted cytolysis of the MOv18+ ovarian carcinoma cell line Igrov-I by autologous T lymphocytes was inhibited by peritoneal fluid samples containing relatively high HAMA titers. Such inhibitory activity was never detected at the start of phase II, but coincided with the last series of i.p. infusions of targeted T lymphocytes in 2 patients.

Antigen “Suicide”: A Preliminary Study on the Induction of Specific Anti-Immunoglobulin Immunological Suppression in Vivo, Using Radiolabeled Immunoglobulin as “Lethal” Antigen

The effectiveness of immunodiagnosis and immunotherapy is limited when xenogeneic antibodies are used, due to the host's anti-immunoglobulin response. We have attempted to specifically suppress the immune response to the immunogen (immunoglobulin) administered. The concept of antigen “suicide” was used, where the antigen (immunoglobulin) was suitably radiolabelled and administered to animals. The question asked was whether immunocompetent cells that specifically interact with the radiolabeled immunogen, would be lethally irradiated and thus become inactivated rather than stimulated. When mice where primed with111Indium-labelled polyclonal human IgG (specific activity 15 mCi/mg), they responded 13% less than control animals (p = 0.0485). This suppression was IgG-specific, since all animals responded similarly to a control antigen (human albumin). However, a second boost of the same111Indium-labelled preparation (specific activity 7 mCi/mg) did not show any statistically significant immunosuppression. In addition, rabbits primed with125Iodine-labelled mouse monoclonal antibody (specific activity 180mCi/mg) and boosted with the same unlabelled monoclonal antibody, showed a similar anti-mouse antibody response with the ones that received only unlabelled preparation twice. We conclude that the concept of antigen “suicide” may be effective for the induction of specific unresponsiveness; when immunoglobulins are radiolabeled with111Indium at high specific activities, the desired state of specific immune suppression may be induced.

Activation of cellular immunity after intracavitary monoclonal antibody therapy of ovarian cancer

BACKGROUND

Murine monoclonal antibodies (MoAbs) are now used for targeted tumor therapy. A major obstacle in their successful application is the development of a humoral antiglobulin response, which limits the use of repeated cycles of therapy. The cellular aspects of that response are not well understood.

METHODS

Fifteen patients who had one (12 patients) or two (3 patients) courses of MoAb treatment, 13 age-matched patients with the same histologic types of tumors who had not received MoAbs, and 4 healthy control subjects were studied. Peripheral blood mononuclear cells (PBMCs) were obtained and tested for the ability of T-cells to proliferate in vitro in the presence of the MoAb administered for therapy (HMFG1), a control antibody (11.4.1), and, in some cases, their F(ab')2 fragments. In addition, PBMCs from these patients were phenotyped after in vitro MoAb stimulation with antibodies against CD2, CD3, CD4, CD8, CD16, CD20, CD25 (interleukin-2 receptor [IL-2R]), CD45RA, and UCHL1, and the production of interleukin-2 (IL-2) was evaluated by the CTLL-2 bioassay.

RESULTS

A dose-dependent in vitro T-cell proliferation was observed in 13 of the 15 patients after MoAb therapy. This was not observed in the pretherapy group of patients or healthy control subjects. The mean stimulation index (SI) in the posttherapy group was significantly higher than that of the pretherapy patients and that of healthy control subjects (P = 0.007). When the in vitro T-cell proliferative responses of these patients were measured in the presence of HMFG1 MoAb (IgG1) and 11.4.1 MoAb, there was no significant difference in the mean SI for HMFG1 versus 11.4.1 for the whole group of treated patients (P = 0.67). A significant increase in the mean SI was observed in the presence of HMFG1 over 11.4.1 and their F(ab')2 fragments (P = 0.02) in patients treated twice. A significant increase in the percentage of cells expressing IL-2R was observed after in vitro MoAb stimulation. CD4+ lymphocytes, particularly the CD4+/UCHL1+ memory, the CD4+/IL-2R+ subpopulation, and the CD4/CD8 ratio, increased in all the cases studied after MoAb stimulation, where B-cell and natural killer-cell numbers remained relatively constant (< 2-3%). A sixfold increase was found in the production of IL-2 in PBMC supernatants after MoAb stimulation.

CONCLUSIONS

Mouse MoAbs administered to patients with cancer can lead to the generation of T-cells, which can recognize these MoAbs as antigens and therefore refocus the host's cellular immune response against the targeted tumor. The main proliferating population appears to be CD4+ T-lymphocytes, which after stimulation can release IL-2. Multiple treatments may lead to the generation of T-cells with specificity for the idiotypic component of the administered MoAb.

Induction of an immune network cascade in cancer patients treated with monoclonal antibodies (ab1). II. Is induction of anti-idiotype reactive T cells (T3) of importance for tumor response to mAb therapy?

The antitumor effector functions of unconjugated monoclonal antibodies (mAb) in cancer therapy are not fully understood. Direct cytotoxic mechanisms such as antibody-dependent cellular cytotoxicity, complement-dependent cytolysis and apoptosis have been suggested. Induction of anti-idiotypic (ab2) and anti-anti-idiotypic (ab3) antibodies as well as the corresponding T cells (T2 and T3) has also been proposed to be of therapeutic significance. In this study induction of an immune network cascade in ten patients with colorectal carcinoma, treated with mAb 17-1A (ab1) was assessed. After treatment, all ten patients had anti-idiotypic antibodies and anti-anti-idiotypic antibodies with ab1-like binding specificity while only five of ten patients had T cells corresponding to ab3 (T3) as assessed by a proliferation assay (DNA synthesis), and an assay of interferon gamma production (ELISPOT) (Enzyme-linked immuno SPOT) in vitro or by a delayed-type hypersensitivity reaction in vivo. Purified T cells from four of the five patients with a positive T3 test responded with DNA synthesis after stimulation using human anti-mAb 17-1A anti-idiotypic monoclonal antibodies. These four patients had a clinical response showing a tumor reduction after therapy, while all six patients lacking a proliferative response failed to show tumor regression. Induction of a cell-mediated immune network cascade might accordingly be an important antitumor effector function of mAb and should be considered in the future design of mAb-based therapy protocols in cancer patients.

Induction of an immune network cascade in cancer patients treated with monoclonal antibodies (ab1). I. May induction of ab1-reactive T cells and anti-anti-idiotypic antibodies (ab3) lead to tumor regression after mAb therapy?

The antitumor effector functions of unconjugated monoclonal antibodies in cancer therapy are complex. Direct cytotoxic mechanisms such as antibody-dependent cellular cytotoxicity, complement-dependent cytolysis and apoptosis have been suggested. Induction of anti-idiotypic (ab2) and anti-anti-idiotypic (ab3) antibodies as well as T cell (T2 and T3 respectively) responses have also been proposed to be of clinical importance. In this study induction of an immune network cascade in patients with colorectal carcinoma, treated with mAb 17-1A (ab1) was assessed. All patients developed anti-idiotypic antibodies (ab2) of the IgG class after treatment with ab1 and four of nine patients showed induction of mouse Ig reactive T cells [a proliferative response to F(ab')2 fragments of ab1]. Patients with such a T cell response developed anti-anti-idiotypic antibodies (ab3), while those lacking the T cell reactivity failed to mount an ab3 response. Three of four patients with a T cell response achieved a tumor response to mAb therapy. Thus, all responding patients belonged to the group of individuals developing ab3. Induction of mAb(ab1)-reactive T cells as well as an immune network cascade might be important antitumor effector functions of mAb and should be considered in the future design of mAb-based therapy protocols in cancer patients.

Adjuvant therapy of ovarian cancer with radioactive monoclonal antibody

Fifty-two patients with epithelial ovarian cancer were treated with yttrium-90-labelled monoclonal antibody HMFG1 administered intraperitoneally following conventional surgery and chemotherapy as part of an extended phase I-II trial. The treatment was well tolerated and the only significant toxicity observed was reversible myelosuppression as previously described. Following conventional surgery and chemotherapy, 21 out of the 52 patients had no evidence of residual disease and were regarded as receiving treatment in an adjuvant setting. To date, two of these patients have died of their disease (follow-up 3-62 months, median follow-up 35 months). This extended phase I-II study suggests that patients with advanced ovarian cancer who achieve a complete remission following conventional therapy may benefit from further treatment with intraperitoneal radioactive monoclonal antibody.

Review: advances in monoclonal antibody tumour targeting

Since the breakthrough in producing monoclonal antibodies was achieved, this new tool has opened up numerous avenues in basic science and clinical investigation. In the area of oncology, monoclonal antibodies were initially seen as offering new hopes of a cure and many investigations in the last decade therefore focused on applying these reagents in tumour diagnosis and therapy. The results to date have been less encouraging and have served as a basis for understanding current limitations in the application of monoclonal antibodies and designing future strategies to overcome these problems. Advances in molecular biology now offer the possibility of better understanding tumour antigens and of constructing recombinant antibody fragments and fusion proteins with novel effector functions. Furthermore, advances in chelate and isotope chemistry have enabled the use of more potent and stable radiolabelled immunoconjugates. Better understanding of tumour biology and the mechanisms of tumour escape from current therapeutic approaches in opening up the intriguing possibility of combining monoclonal antibody-based therapy with chemotherapy, radiotherapy, and biological response modifiers.

The clinical significance of HAMA in patients treated with mouse monoclonal antibodies

Twenty-four patients were analyzed for the development of HAMA (human antimouse antibodies) after being treated with repeated doses (200-500 mg) of the mouse monoclonal antibody (MAb) 17-1A. All patients developed anti-17-1A IgG antibodies, and most of them also developed IgM antibodies. In only two patients could immune complexes be demonstrated. Allergic reactions were rare (1.9%). In an extended study, a further 19 patient were analyzed for an idiotypic response. Forty-one out of 43 patients developed antiidiotypic antibodies (ab2), and 20 of these also anti-anti-idiotypic antibodies (ab3). Ab3+ patients responded significantly better (p = 0.01) and survived longer (p < 0.001) compared to ab3- patients. In this study, we showed that MAb 17-1A could be repeatedly given on a safe basis. The development of high titers of HAMA did not cause significant clinical problems when further repeated infusions of MAb 17-1A were given. The development of an idiotypic response also indicate that the induction of HAMA might be beneficial and not harmful to the patient.

Tumour localisation with a radioactively labelled reshaped human monoclonal antibody

A genetically reshaped human IgG1 monoclonal antibody (Hu2PLAP) with anti-tumour specificity, was radiolabelled with Indium-111 by chelation with a new macrocyclic compound (DOTA) which allows the production of stable radioimmunoconjugates for in vivo application. This was used to image seven patients with malignant disease, of whom two had been previously exposed to mouse monoclonal antibodies and had developed human anti-mouse antibodies (HAMA). Successful tumour localisation was seen in the four patients with active disease and antigen positive tumours. No patient showed any antibody responses against Hu2PLAP, but three out of six patients tested showed an immune response against the macrocycle DOTA. Reshaped human monoclonal antibodies with anti-tumour specificity may facilitate repeated administrations of radioactive antibodies, thus allowing new possibilities, both in the diagnosis and treatment of cancer.

Patients receiving murine monoclonal antibody therapy for malignancy develop T cells that proliferate in vitro in response to these antibodies as antigens

Peripheral blood mononuclear cells (PBMCs) were obtained from patients receiving radioactive murine monoclonal antibody (MAb) therapy for malignant epithelial tumours, as well as normal controls, and were tested for the ability of T cells to proliferate in vitro in the presence of the MAb administered for therapy (HMFG1), and another isotypically matched antibody of irrelevant specificity (11.4.1). We studied 13 patients who had one (ten patients) or two (three patients) courses of MAB treatment, 11 age matched patients with the same histologic types of tumours, that had not received MAbs, and four normal controls. There was a consistent dose dependent in vitro T cell proliferation in 11 of the 13 patients after MAb therapy. This was not observed in the pre-therapy group of patients or normal controls, where the T cell proliferative responses remained baseline. The mean stimulation index (S.I.) in the post-therapy group was significantly higher than that of the pre-therapy patients and that of normal controls. When the in vitro T cell proliferative responses of these patients were measured in the presence of HMGF1 MAb (IgG1) and an isotypically identical, but idiotypically unrelated 11.4.1 MAb (IgG1), there was no statistically significant difference in the mean S.I. For HMFG1 vs 11.4.1 for the whole group of treated patients. When patients were separated into those who received one and those who received two MAb treatments, a significant increase in the mean S.I. was observed in the presence of HMFG1, in the group of patients receiving two treatment courses, suggesting the generation of T cells with specificity for the idiotypic component of the administered murine immunoglobulin. In order to further characterise these in vitro cellular responses we incubated PBMCs with and without an optimal concentration of the MAb (100-300 micrograms ml-1), as defined by the proliferation assay, and compared the differences in cell subpopulations. A significant increase in the percentage of cells expressing interleukin-2 receptors (IL-2R) was observed after MAb stimulation. The percentage of CD4+ lymphocytes and the CD4/CD8 ratio increased in all the cases studied, after MAb stimulation, where the percentages of B cells and NK cells remained relatively constant at less than 2-3% of the total population. We therefore conclude that murine MAbs administered to patients with cancer can lead to the generation of T cells which can recognise these MAbs as antigens when presented appropriately in vitro. The main proliferating population appears to be T helper CD4+ lymphocytes which following stimulation can release interleukin-2 leading to the expression of high levels of IL-2R.

Induction of anti-idiotypic (ab2) and anti-anti-idiotypic (ab3) antibodies in patients treated with the mouse monoclonal antibody 17-1A (ab1). Relation to the clinical outcome--an important antitumoral effector function?

Forty-three patients with metastatic colorectal carcinoma (CRC) were treated with the unconjugated mouse monoclonal antibody (MAb) 17-1A (ab1) only. The presence of antiidiotypic antibodies (ab2) and anti-antiidiotypic antibodies (ab3) were analyzed using an ELISA technique and a mixed hemadsorption assay respectively. Ninety-five percent (41/43) of the patients developed ab2 both of the IgM and the IgG classes. Forty-seven percent (20/43) of the patients had detectable ab3 after therapy, two of them also before administration of MAb 17-1A. Binding in vitro of ab3 (ab1) to CRC cells could be specifically inhibited by ab1. Ab3 bound to human monoclonal antiidiotypic antibodies and to a goat antiidiotypic antibody (ab2). Both these ab2 were directed against MAb 17-1A (ab1). There was a strong correlation between the presence of ab3 and the clinical outcome. Ab3+ patients survived significantly longer than those who did not develop ab3 antibodies, 80 weeks vs 38 weeks (p less than 0.001). A statistically significant correlation was found between the presence of ab3 and the anti-tumor response (CR + PR + MR + SD) (p = 0.01). Thus, induction of an antiidiotypic cascade seems to be an important antitumor effector function of MAb in the treatment of cancer patients.

Xenogeneic monoclonal antibodies in the management of cancer: control of their in vivo immunogenicity and induction of specific unresponsiveness using an antibody-drug immunoconjugate

A bispecific mouse monoclonal antibody (mAb) that recognises carcinoembryonic antigen (CEA) with one binding site and vinblastine (VLB) with the other was used, and its in vivo immunosuppressive effect specific for anti-mouse immunoglobulin (Ig) was studied. The antibody was incubated with VLB at a molar ratio (MR) of 1:1, and administered i.v. to rabbits. Control animals received either the MAb alone, or the MAb with VLB covalently linked (MR 1:1), or the parental anti-CEA with equimolar amount of VLB. Seven days later, the rabbit anti-mouse Ig primary response was measured, and found to be almost 55% reduced in the animals that received the VLB 'loaded' MAb. In vivo kinetics and stability experiments revealed that the T1/2 of the MAb was 68 +/- 5 h, whereas free VLB disappeared within minutes. It was concluded that as soon as the drug dissociates from the antibody's binding site, it is rapidly removed. This problem was overcome by subcutaneously implanting osmotic mini-pumps containing VLB. The pumps released the drug at a constant rate for a period greater than 1 week, saturating the antibody's binding site. Under these conditions rabbits developed 80% less anti-mouse Ig antibodies when the bispecific antibody was administered (compared with the parental anti-CEA). The immunosuppression observed was specific for the mouse Ig, under conditions compatible with the full clinical therapeutic potential of the MAb. In conclusion, these experiments show, that it is possible to develop hybrid antibodies that can act as a 'lethal bait' to any specific lymphocyte in vivo, thus preventing undesirable responses against the xenogeneic MAb.

Patients treated with a monoclonal antibody (ab1) to the colorectal carcinoma antigen 17-1A develop a cellular response (DTH) to the "internal image of the antigen" (ab2)

The anti-tumor effector functions of unconjugated MAb in cancer therapy are not fully understood. Direct cytotoxic mechanisms have been demonstrated as well as induction of anti-idiotypic (ab2) and anti-anti-idiotypic (ab3) antibodies. If such a humoral response is induced, then an idiotypic cellular response would also be anticipated. Human monoclonal ab2s which mimic a tumor-associated antigen (TAA) (CO17-1A) of colorectal carcinoma (CRC) cells ("the internal image of the antigen") were produced. These ab2s were injected intradermally to patients with metastatic CRC who had been treated with the anti-colon carcinoma MAb 17-1A (ab1). Five out of 12 patients had a specific DTH (delayed-type hypersensitivity) reaction of the tuberculin type, which was proven by immunohistochemical analysis of skin biopsies. Serum ab3 was demonstrated in 4/4 tested DTH+ patients and also in 4 DTH patients. Control patients did not show any skin reactivity. Generation of an idiotypic response induced by the infused antibody (ab1) might be regarded as an active anti-tumor "vaccination". Induction of an idiotypic cellular and humoral cascade might be an important anti-tumor effector function of MAb and should be considered in future strategies for such therapy in cancer patients.

Human response against NP-4, a mouse antibody to carcinoembryonic antigen: human anti-idiotype antibodies mimic an epitope on the tumor antigen

Anti-idiotype antibodies (Ab2) were purified from a cancer patient treated with NP-4, a murine monoclonal antibody to carcinoembryonic antigen (CEA). These Ab2 were specific for NP-4 and inhibited the binding between NP-4 and CEA. BALB/c mice immunized with these human Ab2 produced anti-Ab2 antibodies that were also reactive with the CEA epitope recognized by NP-4. These results indicate that human Ab2 to NP-4 can antigenically mimic the CEA epitope recognized by NP-4.

Autologous antibodies eluted from membrane fragments in human ovarian epithelial neoplastic effusions. III. Cytotoxic potential in vitro and characterization of antigen(s)

Cyst and ascites fluids from patients with ovarian epithelial neoplasms contain immunoglobulins with antitumor activity. Autologous antibodies bound to the cellular membrane fragments obtained from human ovarian neoplastic effusions react with cell-surface antigens on different human ovarian cell lines, surgical specimens of human ovarian adenocarcinoma, and human ovarian tumors grown in athymic Balb/c mice. The antibodies do not react with tissue preparations from normal human ovaries, other nonovarian normal or neoplastic tissues, and nonovarian human cell lines. These studies indicate that these antibodies are capable of complement-mediated lysis of human ovarian tumor cell lines in vitro. Preliminary characterization of the autologous ovarian tumor-associated antigen(s) indicates that it may be composed of three large-molecular-weight proteins of 182,000, 164,000, and 122,000 d.

Characteristic immunophenotyping artefact seen in patients with anti-mouse immunoglobulin antibodies

Patients treated with murine monoclonal antibodies develop anti-mouse immunoglobulin antibodies which can interfere with flow cytometry of lymphocytes, giving rise to high levels of nonspecific staining. This artefact can be avoided by using separated, washed lymphocytes for immunophenotyping.

Idiotypic cascades in cancer patients treated with monoclonal antibody CO17-1A

We have previously shown that gastrointestinal cancer patients treated with monoclonal antibody CO17-1A (Ab1) developed anti-idiotypic antibodies (Ab2) to the Ab1. We now demonstrate that patients produce anti-anti-idiotypic antibodies (Ab3) to their autologous Ab2. Ab3 were demonstrated in culture supernatants of peripheral blood mononuclear cells from five Ab1-treated patients after stimulation of the cells with heterologous Ab2 that functionally mimicked the tumor antigen (Ag) defined by Ab1 and immunologically cross reacted with the patients' Ab2. Ab3 shared idiotopes with Ab1 and were Ab1-like in their binding specificities to tumor cells, Ag, and Ab2. Such antibodies were also elicited by stimulating cells with Ag. However, they were not produced by stimulating posttreatment mononuclear cells with control proteins or by stimulating pretreatment cells with either Ag or Ab2. Our results demonstrate idiotypic cascades in cancer patients treated with monoclonal antibody. Ag-specific Ab3 responses may underlie delayed clinical responses often observed in cancer patients treated with monoclonal antibodies of various specificities.