Malcolm S. Mitchell

Immunosuppressive Effects of Cytosine Arabinoside and Methotrexate in Man

Abstract Thirty-six patients with nonlymphoid solid tumors who were undergoing therapy with cytosine arabinoside (ara-C) or methotrexate (MTX) were immunized withEscherichia coliVi antigen and teta...

Activation of suppressor T cells by tumour cells and specific antibody

IMMUNOSUPPRESSION by passively administered antibody has long been known (see ref. 1 for review) and as antibody can cause enhancement of tumour growth2,3, particular attention has been paid to the role of antibody-mediated immunosuppression in tumour immunology. Hellstrom et al. have emphasised that blocking factors, most likely antigen-antibody complexes4, suppress cell-mediated immunity and thus play a major part in the progression of tumour growth5. Such blocking factors may be an important factor in the induction and/or maintenance of some forms of immunological tolerance6–8. But the mechanism remains obscure.

Increased effectiveness of interferon alfa-2b following active specific immunotherapy for melanoma.

PURPOSE To determine whether interferon alfa-2b (IFN-alfa; intron-A, Schering Corp, Kenilworth, NJ) can induce a remission in patients previously treated with active specific immunotherapy (therapeutic melanoma vaccine) without response. PATIENTS AND METHODS Eighteen patients with disseminated melanoma who had failed to respond to at least five injections of Melacine therapeutic melanoma vaccine (Ribi ImmunoChem Research, Inc, Hamilton, MT) were then treated IFN-alfa after a 4-week interval. IFN-alfa 5 or 6 x 10(6) U/m2 was self-administered three times a week subcutaneously by melanoma patients for at least 2 months. Computed tomographic (CT) scans of the chest, abdomen, and pelvis and magnetic resonance imaging of the brain were performed within 4 weeks before treatment as a baseline, and then at 2-month intervals during treatment to evaluate response. All 18 patients were HLA-typed before treatment. The frequency of cytolytic T-cell precursors (pCTL) in the blood had been measured weekly in 13 of the patients during treatment with Melacine. RESULTS Eight of 18 patients (44.4%) had a major objective clinical response induced by IFN-alfa, including site-specific complete remissions in five. Responses lasted a median of 11 months. The median survival duration of the responders has not been reached, and exceeds 32 months. The group as a whole had a median survival duration of 10.1 months, and nonresponders lived 7.3 months. Cytolytic T-cell precursors had been increased by immunization in all five responding patients tested, but also in five of eight nonresponders. There was no association of response to IFN-alfa with specific HLA phenotypes, in contrast to our previous results with melanoma theraccine alone. CONCLUSION These data suggest an additive effect of active specific immunotherapy and IFN-alfa on the objective response rate, perhaps through upregulation of HLA molecules and tumor-associated antigens on the tumor cell by IFN-alfa, after immunization of the patient by Melacine. This treatment may have improved survival over that expected in metastatic melanoma.

Synthetic insertion signal sequences enhance MHC class I presentation of a peptide from the melanoma antigen MART-1

Cytotoxic T lymphocytes (CTL) recognize minimal peptides of eight to ten residues which are the products of intracellularly processed proteins and are presented at the cell surface by MHC class I molecules. An important step in this process is the translocation of processed proteins from the cytosol across the endoplasmic reticulum membrane mediated by transporter associated with antigen processing (TAP) proteins, or as an alternative, by endoplasmic reticulum insertion signal sequences. We report here that the addition of synthetic signal sequences at the N terminus, but not at the C terminus, of an epitope from the human melanoma antigen MART‐1 greatly enhances its presentation in both TAP‐deficient and TAP‐expressing cells. A newly designed peptide construct, composed of the epitope replacing the hydrophobic part of a natural signal sequence, was also very effective. Interestingly, an artificial signal sequence containing the same epitope was the most efficient construct for enhancing its presentation. These peptide constructs facilitated epitope presentation when loaded into the cytosol of TAP‐deficient T2 cells, TAP‐expressing melanoma cells and human dendritic cells. These findings may be of practical significance for the development of synthetic anti‐cancer vaccines and in vitro immunization of CTL for adoptive immunotherapy.

Active specific immunotherapy of metastatic melanoma with an antiidiotype vaccine: a phase I/II trial of I-Mel-2 plus SAF-m.

PURPOSE To determine the toxicity and immunologic activity of an antiidiotype melanoma vaccine that consists of monoclonal antibody I-Mel-2 (MELIMMUNE-2, IDEC Pharmaceuticals, La Jolla, CA) and an immunologic adjuvant SAF-m. PATIENTS AND METHODS Twenty-six patients with metastatic melanoma, 17 of whom had previously received chemotherapy, were given 2 mg of I-Mel-2 and either 100 micrograms (n = 6) or 250 micrograms (n = 20) of SAF-m. Antiidiotype vaccine was given intramuscularly (IM) biweekly for 4 weeks, and then bimonthly until disease progression. Human antimurine antibodies (HAMA), anti-I-Mel-2 antibodies, and specific antibody (Ab)3 against the melanoma epitope mimicked by the vaccine were titrated before treatment, biweekly from weeks 4 to 12, and every 4 to 8 weeks thereafter. Computed tomographic (CT) scans of the chest, abdomen, and pelvis and magnetic resonance imaging (MRI) of the brain were obtained before and bimonthly during treatment to evaluate responses. RESULTS Elevated titers of human antimouse antibodies and anti-I-Mel-2 antibodies were associated with clinical antitumor effect (P = .02 and P = .05, respectively). Ab3 was absent in most patients, but was found in the best clinical responder. Fever, myalgias/arthralgias, fatigue, nausea, and headaches were the most common toxicities. Grade III myalgias/arthralgias and headaches required dose reduction of SAF-m in eight patients at the 250-microgram dose. No treatment-related death occurred. Six patients had an antitumor effect: one complete response in liver and lung, two minor responses, and three stable disease. The patient with a complete response has survived nearly 5 years. CONCLUSION I-Mel-2 antiidiotype vaccine was safe, tolerated best at the 100-microgram dose of SAF-m, and had immunologic and clinical activity.

Detection of melanoma-reactive CD4+ HLA-class I-restricted cytotoxic T cell clones with long-term assay and pretreatment of targets with interferon-γ

Twenty-five CD4+ cytotoxic T lymphocyte (CTL) clones were obtained from the peripheral blood or tumor tissues of melanoma patients undergoing active specific immunotherapy. Melanoma-reactive T cells were cloned by limiting dilution using either autologous or allogeneic melanoma cells to stimulate their proliferation. Sixteen of the clones reacted against autologous melanoma cells but not against the autologous lymphoblastoid cell line, which we defined as “melanoma-specific”. Optimal demonstration of the lytic activity of CD4+ CTL required a 16-h incubation period and an effector∶target cell ratio of 40∶1. In addition, a 24-h pre-incubation of the target melanoma cells with 100 U interferon (IFN)γ consistently augmented lysis by these CD4+ CTL, increasing it from a mean level of 20% to one of 52%. Lysis by 8 of the 11 melanoma-reactive CD4+ T cell clones was exclusively HLA-class-I-restricted, as judged by blocking with monoclonal antibodies (mAb). Five of these HLA class-I-restricted clones were reactive only with the autologous melanoma cells, while the other 3 clones were also reactive with allogeneic melanoma cells. In all cases, the T cells and melanoma targets shared at least one HLA class I allele, usually HLA-A2, HLA-C3 or HLA-B62. Interestingly, lysis by 2 of the 11 clones was inhibited by both anti-HLA-class-I or -HLA-class-II mAb, while lysis by 1 other clone was inhibited by neither. HLA class I molecules and several accessory molecules were maximally expressed by the melanoma target cells, both in terms of distribution and copy number before IFNγ treatment. Thus, IFNγ may have acted by increasing the expression of melanoma-associated epitopes as presented by HLA class I (or HLA class II) molecules. A proportion of human CD4+CTL appeared to recognize melanoma-associated epitopes presented by the HLA class I molecule, although their lytic potency may be less than that of their CD8+ counterparts.

Phase I Trial of Large Multivalent Immunogen Derived from Melanoma Lysates in Patients with Disseminated Melanoma

Purpose: The purpose of this research was to determine the toxicity and immunological activity of large multivalent immunogen (LMI), a preparation of tumor cell membranes affixed to amorphous silica microbeads, in patients with melanoma. Experimental Design: Nineteen patients with metastatic (stage IV) melanoma were entered into the study, of whom 15 received the full 3 months of treatment with LMI. LMI was administered without adjuvant, one-half intradermally (i.d.) and the other half s.c. Because we expected little toxicity, we first treated 2 patients at each dose level, 10-, 30-, or 100-million tumor cell equivalents on weeks 0, 4, and 8, and subsequently randomized the remaining 13 patients to receive treatment with one of those dosage schedules, for a total of 19 patients. Two patients who were registered were found to be ineligible because of brain metastases, and 2 others did not complete the course of treatment for reasons other than toxicity. Thus, 15 patients were fully evaluable. Patients with evidence of a clinical response (at least stable disease at the 12-week checkpoint) had the option of continuing treatment at 4-week intervals. Frequencies of cytolytic T cell precursors against HLA-A2 matched melanoma cells, and delayed-type hypersensitivity to a melanoma cell membrane preparation from a component melanoma cell line were performed to measure immunological efficacy, and serum chemistries and complete blood counts were performed every 2 weeks throughout the study to measure possible toxicity. Computed tomography scans were performed pretreatment and at week 12 to measure possible beneficial effects on known lesions. Results: Eight of the 15 evaluable patients had an increase in cytolytic T-cell precursors during the course of therapy, usually by day 42. No patient had demonstrable delayed-type hypersensitivity to a melanoma membrane preparation before or after treatment. No toxicity of any kind was observed. A degree of clinical effectiveness of LMI was suggested by the elicitation of stable disease in 5 patients at 12 weeks. One patient had >50% regression of a lung nodule but progression of disease to the brain, whereas a second patient had a bona fide partial remission of a 3-cm diameter solitary lung nodule. Conclusions: LMI was nontoxic, improved immunological reactivity to melanoma cells, and showed evidence of clinical effectiveness (shrinkage of tumor) in 1 patient. Additional studies with LMI with added adjuvant materials, in melanoma and other cancers, appear warranted.

Cancer Vaccines: Novel Approaches and New Promise

Cancer vaccines are a promising tool in the hands of the clinical oncologist. We have summarized the most recent findings and achievements in this exciting field. Tumor-associated antigens, as a basis for the new cancer vaccines, are reviewed. We emphasize novel approaches for the design of safe and more effective vaccines for cancer. We also discuss the possible clinical applications and the future prospects for vaccine development.

Cytophilic Antibodies in Man

Abstract Antibodies cytophilic for macrophages, mediating attachment of immunologically naive macrophages to leukemic cells, were found in the serum of 25 patients with acute myelocytic or lymphocy...

Lymphocytes cytotoxic to uveal and skin melanoma cells from peripheral blood of ocular melanoma patients

SummaryTo study antitumor immunity in patients with choroidal melanoma, T cells were generated from the peripheral blood of choroidal melanoma patients by mixed lymphocyte/tumor cell culture (MLTC). Because autologous tumors are generally unavailable, an allogeneic choroidal melanoma cell line, OCM-1, was used as the specific stimulus. Lymphocyte cultures from 27 patients were characterized by cell-surface phenotypes, patterns of reactivity towards cells of the melanocytic origin and T-cell-receptor gene usage. Antimelanoma reactivity was found in cell-sorter-purified CD4+ and CD8+ T cell subsets. To analyze this reactivity, sorter-purified CD4+ and CD8+ cells from a MLTC were cloned by limiting dilution in the presence of exogenous interleukin-2 and interleukin-4 as well as irradiated OCM-1. Under these conditions, CD4+ T cells did not proliferate, perhaps because of the absence of antigen-presenting cells. However, CD8+ grew vigorously and 29 cytolytic CD8+ T cell clones were isolated. On the basis of their pattern of lysis of OCM-1, a skin melanoma cell line M-7 and its autologous lymphoblastoid cell line LCL-7, the clones were categorized into three groups. Group 1, representing 52% of the clones, lysed all three target cells, and are alloreactive. However, since OCM-1 and M-7 did not share class I antigens, these clones recognized cross-reactive epitope(s) of the histocompatibility locus antigen (HLA) molecule. Group 2, constituting 28% of the clones, lysed both the ocular and skin melanoma cell lines but not LCL-7, and were apparently melanoma-specific. Unlike classical HLA-restricted cytolytic T lymphocytes, these T cells might mediate the lysis of melanoma cells via other ligands or a more degenerate type of HLA restriction. For the latter, the HLA-A2 and -A28 alleles would have to act interchangeably as the restriction element for shared melanoma-associated antigen(s). Group 3, representing only 10% of the T cell clones, was cytotoxic only to OCM-1, but not to M-7 or LCL-7. These clones may recognize antigens unique to ocular melanoma cells. Our data suggest that choroidal melanoma patients can recognize melanoma-associated antigens common to both ocular and cutaneous melanoma cells, and presumbly their autologous tumor. Thus, choroidal melanoma, like its skin counterpart, may be responsive to immunotherapeutic regimens such as active specific or adoptive cellular immunotherapy.