Immunotherapy with anti-CD3 monoclonal antibodies and recombinant interleukin 2: stimulation of molecular programs of cytotoxic killer cells and induction of tumor regression

Mechanisms of Superior Anti-Tumor Cytotoxic Response of Interleukin 15-Induced Lymphokine-Activated Killer Cells

Interleukin (IL) 15 is one of the main cytokines controlling cytotoxic lymphocyte survival and growth. Despite its receptor and functional similarity to IL-2, IL-15 affects a wider target cell population and utilizes different mechanisms in cell activation. The role of IL-15 in lymphokine-activated killer (LAK) cell generation in vitro and potential mechanisms of cytotoxicity compared with equivalent low concentration of IL-2 with or without mitogens (phytohemoglutinin (PHA) and anti-CD3 antibody) have been investigated in this study. IL-15 treatment resulted in moderate cell proliferation over 7 days, whereas IL-2 treatment was associated with decreased cell numbers. Unlike IL-2 in combination with mitogens, IL-15 caused increases in both cytotoxic T lymphocytes (CTL) and CD56 LAK cells, particularly cytokine-induced killer and cytolytic natural killer T-cell (CNK-T) subpopulations, which are known to be highly effective in cytotoxicity. IL-15 also increased overall perforin and tumor necrosis factor-alpha expression and more prominently in CTLs. Consequently, IL-15 resulted in superior cytotoxicity against two different NK-sensitive (human K-562 and murine YAC-1) and LAK-sensitive (human Daudi and Raji) cell lines compared with other cytokine combinations. There was also no contribution of mitogens to IL-2-induced cytotoxicity. In conclusion, IL-15 at the concentration of 10 ng/mL used in this study causes moderate proliferation and superior cytotoxicity of LAK cells in vitro that was associated with induction of a specific LAK cell subpopulation profile and related cellular killing mechanisms. These results are encouraging for potential use of IL-15 as part of immunotherapy.

Immunotherapy of cancer by active vaccination: does allogeneic bone marrow transplantation after non-myeloablative conditioning provide a new option?

The critical role of antigen-specific T cells in cancer immunotherapy has been amply demonstrated in many model systems. Though success of clinical trials still remains far behind expectation, the continuous improvement in our understanding of the biology of the immune response will provide the basis of optimized cancer vaccines and allow for new modalities of cancer treatment. This review focuses on the current status of active therapeutic vaccination and future prospects. The latter will mainly be concerned with allogeneic bone marrow cell transplantation after non-myeloablative conditioning, because it is my belief that this approach could provide a major breakthrough in cancer immunotherapy. Concerning active vaccination protocols the following aspects will be addressed: i) the targets of immunotherapeutic approaches; ii) the response elements needed for raising a therapeutically successful immune reaction; iii) ways to achieve an optimal confrontation of the immune system with the tumor and iv) supportive regimen of immunomodulation. Hazards which one is most frequently confronted with in trials to attack tumors with the inherent weapon of immune defense will only be briefly mentioned. Many question remain to be answered in the field of allogeneic bone marrow transplantation after non-myeloablative conditioning to optimize the therapeutic setting for this likely very powerful tool of cancer therapy. Current considerations to improve engraftment and to reduce graft versus host disease while strengthening graft versus tumor reactivity will be briefly reviewed. Finally, I will discuss whether tumor-reactive T cells can be "naturally" maintained during the process of T cell maturation in the allogeneic host. Provided this hypothesis can be substantiated, a T cell vaccine will meet a pool of virgin T cells in the allogeneically reconstituted host, which are tolerant towards the host, but not anergised towards tumor antigens presented by MHC molecules of the host.

Specific immunotherapy of cancer in elderly patients

The concept of immunotherapy of cancer is more than a century old, but only recently have molecularly defined therapeutic approaches been developed. In this review, we focus on the most promising approach, active therapeutic vaccination. The identification of tumour antigens can now be accelerated by methods allowing the amplification of gene products selectively or preferentially transcribed in the tumour. However, determining the potential immunogenicity of such gene products remains a demanding task, since major histocompatibility complex (MHC) restriction of T cells implies that for any newly defined antigen, immunogenicity will have to be defined for any individual MHC haplotype. Tumour-derived peptides eluted from MHC molecules of tumour tissue are also a promising source of antigen. Tumour antigens are mostly of weak immunogenicity, because the vast majority are tumour-associated differentiation antigens already 'seen' by the patient's immune system. Effective therapeutic vaccination will thus require adjuvant support, possibly by new approaches to immunomodulation such as bispecific antibodies or antibody-cytokine fusion proteins. Tumour-specific antigens, which could be a more potent target for immunotherapy, mostly arise by point mutations and have the disadvantage of being not only tumour-specific, but also individual-specific. Therapeutic vaccination will probably focus on defined antigens offered as protein, peptide or nucleic acid. Irrespective of the form in which the antigen is applied, emphasis will be given to the activation of dendritic cells as professional antigen presenters. Dendritic cells may be loaded in vitro with antigen, or, alternatively, initiation of an immune response may be approached in vivo by vaccination with RNA or DNA, given as such or packed into attenuated bacteria. The importance of activation of T helper cells has only recently been taken into account in cancer vaccination. Activation of cytotoxic T cells is facilitated by the provision of T helper cell-derived cytokines. T helper cell-dependent recruitment of elements of non-adaptive defence, such as leucocytes, natural killer cells and monocytes, is of particular importance when the tumour has lost MHC class I expression. Barriers to successful therapeutic vaccination include: (i) the escape mechanisms developed by tumour cells in response to immune attack; (ii) tolerance or anergy of the evoked immune response; (iii) the theoretical possibility of provoking an autoimmune reaction by vaccination against tumour-associated antigens; and (iv) the advanced age of many patients, implying reduced responsiveness of the senescent immune system.

Expansion of cytolytic CD8(+) natural killer T cells with limited capacity for graft-versus-host disease induction due to interferon gamma production

T cells with natural killer cell phenotype and function (NKT cells) have been described in both human and murine tissues. In this study, culture conditions were developed that resulted in the expansion of CD8(+) NKT cells from bone marrow, thymus, and spleen by the timed addition of interferon-gamma (IFN-gamma), interleukin 2 (IL-2), and anti-CD3 monoclonal antibody. After 14 to 21 days in culture, dramatic expansion of CD3(+), CD8(+), alphabetaT-cell receptor(+) T cells resulted with approximately 20% to 50% of the cells also expressing the NK markers NK1.1 and DX5. The CD8(+) NKT cells demonstrated lytic activity against several tumor target cells with more than 90% lysis by day 14 to day 21 of culture. Cytotoxicity was observed against both syngeneic and allogeneic tumor cell targets with the greatest lytic activity by the cells expressing either NK1.1 or DX5. The expanded CD8(+) NKT cells produce T(H)1-type cytokines with high levels of IFN-gamma and tumor necrosis factor alpha. Expansion of the CD8(+) NKT cells was independent of CD1d. Ly49 molecules were expressed on only a minority of cells. A single injection of expanded CD8(+) NKT cells was capable of protecting syngeneic animals from an otherwise lethal dose of Bcl1 leukemia cells. Expanded CD8(+) NKT cells produced far less graft-versus-host disease (GVHD) than splenocytes across major histocompatibility barriers, even when 10 times the number of CD8(+) NKT cells as compared to splenocytes were injected. This reduction in GVHD was related to IFN-gamma production since cells expanded from IFN-gamma knock-out animals caused acute lethal GVHD, whereas cells expanded from animals defective in fas ligand, fas, IL-2, and perforin did not. These data indicate that CD8(+) NKT cells expanded in this fashion could be useful for preserving graft-versus-leukemia activity without causing GVHD.

Human melanoma therapy in the SCID mouse: in vivo targeting and reactivation of melanoma-specific cytotoxic T cells by bi-specific antibody fragments

The adoptive transfer of tumor-specific cytotoxic T cells (CTL) offers a promising perspective in cancer immunotherapy. However, the ex vivo-generated T lymphocytes are mostly IL-2-dependent. Here we explored the possibility of circumventing the requirement for IL-2, known for severe side effects in the patient, and of simultaneously targeting the CTL towards the tumor by the use of 2 bi-specific antibody fragments. As a model system, we used SCID mice bearing an s.c.-implanted human melanoma line (BLM-gp100) and in vitro-generated CTL specific for the gp100-derived immunogenic peptide YLEPGPVTA, which were injected i.v. with delay. To maintain the cytotoxic potential of the transferred CTL, 2 bi-specific antibody (biAb) fragments were generated which bound with one arm either CD3 or CD28, a combination known to support the activation of CTL. For targeting the CTL, both biAbs contained the F(ab') part of HD-Me13, an antibody recognizing p97, a non-immunogenic melanoma-associated surface molecule. In vitro and in vivo, the addition of the 2 biAbs increased the cytotoxic potential of the gp100-specific CTL and supported their clonal expansion in the absence of IL-2. Correspondingly, significantly higher numbers of CTL were recovered from melanoma-bearing SCID-mice that received the 2 biAb than from mice treated with the CTL only. In animals treated with CTL plus both biAbs, the primary tumor did not grow, and none of the mice developed metastases. Thus, this set of bi-specific antibody fragments was proved to target effector cells in the tumor-bearing host and to efficiently support in vivo clonal expansion and cytolytic activity of in vitro-generated CTL.

Adoptive transfer: the role of perforin in mouse cytotoxic T lymphocyte rejection of human tumor xenografts in vivo

The popliteal lymph node cells of immunocompetent mice generated a strong in vitro cytotoxic response to footpad injection of several human tumor cell lines and the resulting mouse effector cells predominantly used a perforin-mediated cytotoxic mechanism. A relatively minor FasL-dependent cytotoxic response to CEM-CCRF and Jurkat leukemias, but not colon carcinoma COLO 205 cells, was also detected in immunized perforin-deficient mice. In vitro depletion of CD3+ CD8+ T cells, but not CD4+ T or NK1.1+ cells, completely inhibited lysis of human tumor cells, suggesting that CD3+ CD8+ T cells were effectors of perforin-mediated xenospecific cytotoxicity. Xenospecific cytotoxic T cells from wild-type mice were extremely efficient at rejecting tumor when adoptively transferred into scid mice bearing established COLO 205, CEM-CCRF, or Jurkat tumor xenografts. By contrast, cytotoxic T lymphocytes of perforin-deficient mice had no effect on the growth of established tumor xenografts. These data indicate that perforin, and hence direct cytotoxicity, plays a key role in the ability of adoptively transferred CD8+ cytotoxic T lymphocytes to eradicate established xenografts.

Immunostimulatory therapy with anti-CD3 monoclonal antibodies and recombinant interleukin-2: heightened in vivo expression of mRNA encoding cytotoxic attack molecules and immunoregulatory cytokines and regression of murine renal cell carcinoma

The response rate to IL-2 immunotherapy, currently used in the treatment of metastatic renal cell cancer, is limited. Based on our earlier demonstration that a combined regimen of monoclonal antibodies directed at the T cell surface protein CD3 (anti-CD3 mAbs) and IL-2 is synergistic in constraining tumor progression in a murine fibrosarcoma hepatic metastasis model, we have explored the efficacy of an anti-CD3 mAbs plus IL-2 regimen in a murine renal cell cancer model. Our studies demonstrate that a regimen of anti-CD3 mAbs plus IL-2 is superior to treatment with anti-CD3 mAbs alone or IL-2 alone in reducing the number of pulmonary metastases and in prolonging survival. Moreover, the efficacious regimen is associated with heightened intrapulmonary expression of mRNA encoding cytotoxic attack molecules (perforin, granzyme B) and immunoregulatory cytokines (IL-4, IL-10 and IFN- gamma).

Role of naive and memory T cells in tumor cell lysis mediated by bi-specific antibodies

Bispecific monoclonal antibodies (Bi-mAb) with specificity for a tumor associated antigen and the CD3 or CD28 antigen on T lymphocytes, respectively, induce activation of resting T lymphocytes and target-specific tumor cell lysis. Former studies had confirmed that T cells expressing the CD45RO "memory" antigen at high levels were the most potent effectors of Bi-mAb-mediated cytotoxicity when compared to their "naive" counterparts expressing the CD45RA antigen. Further analysis of the T cell subpopulations revealed that within the memory T cell pool, CD8+ T cells were the effector cell, population with strongest cytolytic activity. The cytolytic activity was correlated with the expression level of perforin and granzymes B mRNA. Ca2+ complexing agents, which abrogate perforin activity, reduced necrosis, while inhibition of granzyme activity in effector or target-cells had a similar effect on apoptosis. These results confirm the crucial role perforin and granzymes play in target-cell lysis and explain why CD8+CD45RO+ T cells activated by combined CD3 and CD28 antigen triggering represent the T cell pool with highest cytolytic potential.

Induction of anti-tumour lymphocytes in cancer patients after brief exposure to supernatants from cultures of anti-CD3-stimulated allogeneic lymphocytes

The present study investigated the ability of supernatants collected from cultures of healthy donor-derived peripheral blood mononuclear cells (HD-PBMCs) stimulated with anti-CD3 monoclonal antibody (MAb) (allogeneic CD3 supernatants; ACD3S) to induce, upon brief exposure, tumour-reactive cytotoxic lymphocytes in cancer patients' PBMCs. ACD3S enhanced natural killer (NK) and lymphokine-activated killer (LAK) cell-mediated cytotoxicity. ACD3S contained increased levels of interleukins (IL) 1, 2, 6, 7 and 12, as well as of granulocyte-macrophage colony-stimulating factor (GM-CSF), gamma-interferon (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha). MAbs against these cytokines significantly reduced the ACD3S-induced cytotoxicity. ACD3S-induced cytotoxicity was not inhibited by anti-CD4, CD8 and MHC class I MAbs, but was markedly reduced in the presence of MAb against CD18. In contrast to HD-PBMC, ACD3S derived from cancer patients' lymphocytes exhibited lower levels of the above-mentioned cytokines and exerted reduced biological activity. In conclusion, ACD3S are able to activate, upon short-term incubation, tumour-reactive lymphocytes from cancer patients' PBMCs that lyse a variety of tumour targets, including autologous tumours. ACD3S contain high levels of certain cytokines that positively influence the induction of autologous tumour-reactive lymphocytes. Such supernatants can be collected easily from healthy donors and stored until use in clinical trials for adoptive cellular therapy of cancer. They may also be indicated in the construction of cytokine cocktails that have the ability to induce anti-tumour cytotoxicity.

Reduction of nitric oxide with L-/NG-monomethyl arginine in interleukin-2 and anti-CD3 monoclonal antibody combination therapy

We evaluated nitric oxide induction in antitumor therapy consisting of anti-CD3 monoclonal antibody (anti-CD3) and interleukin-2 (IL-2), then determined the effect of nitric oxide reduction with L-N(G)-monomethyl arginine (LNMA) on the therapeutic methods. Female C57BL/6 mice, MCA102 (a non immunogenic, NK-resistant murine fibrosarcoma cell line), and 145-2C11 (hamster anti-murine-CD3 mAb) were utilized in an experimental hepatic metastasis model developed by injecting a tumor cell suspension into the spleen of mice. A marked increase in serum NO2 (-) + NO1 was observed at 19 hours after anti-CD3 (10 μ, IV) and additional IL-2 administrations (40 × 10(1) U, twice, If) induced a further increase. The NO2, + NO3- elevation in spot urine in the combination therapy was not suppressed with LNMA at a dose of 100 μg/h but was significantly lowered at 300 μg/h. The efficacy of the anti-CD3 + IL-2 therapy was not diminished by LNMA administration either at 100 μg/h or at 300 μg/h.

CD8 T cell activation after intravenous administration of CD3 x CD19 bispecific antibody in patients with non-Hodgkin lymphoma

A bispecific antibody directed to T and B cells (CD3 x CD19 bsAb) was daily infused intravenously in escalating doses from 10 micrograms up to 5 mg in three patients with chemotherapy-resistant non-Hodgkin lymphoma; in this way we aimed to activate T cells to kill the malignant B cells. Only limited toxicity was observed, consisting of moderate fever preceded by chills or shivers and mild thrombocytopenia. No human anti-(mouse Ig) antibodies were found. Pharmacokinetics showed a t1/2 of 10.5 h with peak levels of 200-300 ng/ml after infusion of 2.5 mg bsAb. bsAb in serum was functionally active in vitro. After bsAb infusion a rise in serum tumour necrosis factor alpha was observed, accompanied by an increase in soluble CD8 and to some extent in soluble interleukin-2 receptor (IL-2R), but not in interferon gamma. IL-4 or soluble CD4. No evidence was found for monocyte activation (no increases in IL-6, IL-8 or IL-1 beta in serum). No gross changes in histology or number of IL-2R+, CD4+ or CD8+ cells were found in the lymph nodes after therapy, but one patient showed activated CD8+ T cells within the tumour nodules. In conclusion, after intravenously administered CD3 x CD19 bsAb only moderate toxicity was found, probably due to CD8+ T cell activation and cytokine release, without CD4+ T cell activation.