The use of hybrid hybridomas to target human cytotoxic T lymphocytes

Proteomics of immune cells from liver tumors reveals immunotherapy targets

Elucidating the mechanisms by which immune cells become dysfunctional in tumors is critical to developing next-generation immunotherapies. We profiled proteomes of cancer tissue as well as monocyte/macrophages, CD4⁺ and CD8⁺ T cells, and NK cells isolated from tumors, liver, and blood of 48 patients with hepatocellular carcinoma. We found that tumor macrophages induce the sphingosine-1-phospate-degrading enzyme SGPL1, which dampened their inflammatory phenotype and anti-tumor function in vivo. We further discovered that the signaling scaffold protein AFAP1L2, typically only found in activated NK cells, is also upregulated in chronically stimulated CD8⁺ T cells in tumors. Ablation of AFAP1L2 in CD8⁺ T cells increased their viability upon repeated stimulation and enhanced their anti-tumor activity synergistically with PD-L1 blockade in mouse models. Our data reveal new targets for immunotherapy and provide a resource on immune cell proteomes in liver cancer.

Combining T-cell-specific activation and in vivo gene delivery through CD3-targeted lentiviral vectors

Genetic modification of T lymphocytes is a key issue in research and therapy. Conventional lentiviral vectors (LVs) are neither selective for T cells nor do they modify resting or minimally stimulated cells, which is crucial for applications, such as efficient in vivo modification of T lymphocytes. Here, we introduce novel CD3-targeted LVs (CD3-LVs) capable of genetically modifying human T lymphocytes without prior activation. For CD3 attachment, agonistic CD3-specific single-chain variable fragments were chosen. Activation, proliferation, and expansion mediated by CD3-LVs were less rapid compared with conventional antibody-mediated activation owing to lack of T-cell receptor costimulation. CD3-LVs delivered genes not only selectively into T cells but also under nonactivating conditions, clearly outperforming the benchmark vector vesicular stomatitis-LV glycoproteins under these conditions. Remarkably, CD3-LVs were properly active in gene delivery even when added to whole human blood in absence of any further stimuli. Upon administration of CD3-LV into NSG mice transplanted with human peripheral blood mononuclear cells, efficient and exclusive transduction of CD3+ T cells in all analyzed organs was achieved. Finally, the most promising CD3-LV successfully delivered a CD19-specific chimeric antigen receptor (CAR) into T lymphocytes in vivo in humanized NSG mice. Generation of CAR T cells was accompanied by elimination of human CD19+ cells from blood. Taken together, the data strongly support implementation of T-cell-activating properties within T-cell-targeted vector particles. These particles may be ideally suited for T-cell-specific in vivo gene delivery.

A Bispecific Antibody to Link a TRAIL-Based Antitumor Approach to Immunotherapy

T-cell-based immunotherapy strategies have profoundly improved the clinical management of several solid tumors and hematological malignancies. A recently developed and promising immunotherapy approach is to redirect polyclonal MHC-unrestricted T lymphocytes toward cancer cells by bispecific antibodies (bsAbs) that engage the CD3 complex and a tumor-associated antigen (TAA). The TNF-related apoptosis-inducing ligand receptor 2 (TRAIL-R2) is an attractive immunotherapy target, frequently expressed by neoplastic cells, that we decided to exploit as a TAA. We found that a TRAIL-R2xCD3 bsAb efficiently activates T cells and specifically redirect their cytotoxicity against cancer cells of different origins in vitro, thereby demonstrating its potential as a pan-carcinoma reagent. Moreover, to mimic in vivo conditions, we assessed its ability to retarget T-cell activity in an ex vivo model of ovarian cancer patients' ascitic fluids containing both effector and target cells—albeit with a suboptimal effector-to-target ratio—with remarkable results.

Design, selection and optimization of an anti-TRAIL-R2/anti-CD3 bispecific antibody able to educate T cells to recognize and destroy cancer cells

Recombinant human tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or TRAIL-receptor agonistic monoclonal antibodies promote apoptosis in most cancer cells, and the differential expression of TRAIL-R2 between tumor and normal tissues allows its exploitation as a tumor-associated antigen. The use of these antibodies as anticancer agents has been extensively studied, but the results of clinical trials were disappointing. The observed lack of anticancer activity could be attributed to intrinsic or acquired resistance of tumor cells to this type of treatment. A possible strategy to circumvent drug resistance would be to strike tumor cells with a second modality based on a different mechanism of action. We therefore set out to generate and optimize a bispecific antibody targeting TRAIL-R2 and CD3. After the construction of different bispecific antibodies in tandem-scFv or single-chain diabody formats to reduce possible immunogenicity, we selected a humanized bispecific antibody with very low aggregates and long-term high stability and functionality. This antibody triggered TRAIL-R2 in an agonistic manner and its anticancer activity proved dramatically potentiated by the redirection of cytotoxic T cells against both sensitive and resistant melanoma cells. The results of our study show that combining the TRAIL-based antitumor strategy with an immunotherapeutic approach in a single molecule could be an effective addition to the anticancer armamentarium.

Hybrid Antibodies in Cancer Diagnosis and Therapy

Monoclonal Antibodies (Mabs) represent a promising tool for cancer diagnosis and theraphy.

Administration of MAbs alone or conjugated to cytotoxic agents has been attempted but has significant limitations. Another potentially effective approach is the use of bispecific or bifunctional antibodies where the capacity to recognize the tumor cell and the toxic agent or lymphocyte activation molecule are united in one MAb. The hybrid molecule can be produced by chemical linkage between the two parentalantibodies, or alternatively by a biological approach that consists in the fusion of the two selected hybridomas. In the resulting quadroma cell the hybridoma immunoglobulin chains recombine randomly to form the bifunctional MAb.

In different in vitro and in vivo models, bifunctional MAbs against tumor and CDS at nanomolar concentration has been shown to promote tumor cell killing by cytotoxic T cells.

Specific localization of chemotherapeutic drugs in xenografted tumors has been demonstrated in mice pretreated with hybrid MAbs.

The advantages of the hybrid MAb approach are that it should reduce the MAb biodistribution problem and that it involves no chemical manipulation between the functional agent and the MAb molecules.

PPARγ in dendritic cells and T cells drives pathogenic type-2 effector responses in lung inflammation

Type-2 immune responses are well-established drivers of chronic inflammatory diseases, such as asthma, and represent a large burden on public health systems. The transcription factor PPARγ is known to promote M2-macrophage and alveolar macrophage development. Here, we report that PPARγ plays a key role in both T cells and dendritic cells (DCs) for development of type-2 immune responses. It is predominantly expressed in mouse Th2 cells in vitro and in vivo as well as human Th2 cells from allergic patients. Using conditional knockouts, we show that PPARγ signaling in T cells, although largely dispensable for IL-4 induction, is critical for IL-33-driven Th2 effector function in type-2 allergic airway responses. Furthermore, we demonstrate that IL-4 and IL-33 promote up-regulation of PPARγ in lung-resident CD11b+ DCs, which enhances migration to draining lymph nodes and Th2 priming capacity. Thus, we uncover a surprising proinflammatory role for PPARγ and establish it as a novel, important mediator of DC-T cell interactions in type-2 immunity.

Elimination of large tumors in mice by mRNA-encoded bispecific antibodies

The potential of bispecific T cell-engaging antibodies is hindered by manufacturing challenges and short serum half-life. We circumvented these limitations by treating mice with in vitro-transcribed pharmacologically optimized, nucleoside-modified mRNA encoding the antibody. We achieved sustained endogenous synthesis of the antibody, which eliminated advanced tumors as effectively as the corresponding purified bispecific antibody. Because manufacturing of pharmaceutical mRNA is fast, this approach could accelerate the clinical development of novel bispecific antibodies.

Emerging trends and new developments in monoclonal antibodies: A scientometric analysis (1980-2016)

This article aims to explore the intellectual landscape of the study of monoclonal antibody (mAb), mainly to identify thematic trends, landmark articles and emerging trends involving mAb. This work is based on 4 sets of bibliographic records retrieved from the Web of Science. The final data set, consisting of 7,385 bibliographic records, was combined from the 4 individual data sets. This study explores the document co-citation clusters of 7,385 bibliographic records to identify the origin of mAb and the hot research specialty of this domain by applying CiteSpace software. We examined the mAb evolution from 4 perspectives: (1) Clusters of cited references regarding mAb; (2) Cited authors as contributors to mAb research; (3) Institutions participating in mAb research; and (4) Cited journals regarding mAb. The technical development, drug development and clinical applications of mAbs were analyzed. Through data analysis, we have identified the new directions for the exploration of mAbs, interactions between mAb technologies and diseases, and evolving global collaboration among institutions.

L-Arginine Modulates T Cell Metabolism and Enhances Survival and Anti-tumor Activity

Metabolic activity is intimately linked to T cell fate and function. Using high-resolution mass spectrometry, we generated dynamic metabolome and proteome profiles of human primary naive T cells following activation. We discovered critical changes in the arginine metabolism that led to a drop in intracellular L-arginine concentration. Elevating L-arginine levels induced global metabolic changes including a shift from glycolysis to oxidative phosphorylation in activated T cells and promoted the generation of central memory-like cells endowed with higher survival capacity and, in a mouse model, anti-tumor activity. Proteome-wide probing of structural alterations, validated by the analysis of knockout T cell clones, identified three transcriptional regulators (BAZ1B, PSIP1, and TSN) that sensed L-arginine levels and promoted T cell survival. Thus, intracellular L-arginine concentrations directly impact the metabolic fitness and survival capacity of T cells that are crucial for anti-tumor responses.

L-Arginine Modulates T Cell Metabolism and Enhances Survival and Anti-tumor Activity

Metabolic activity is intimately linked to T cell fate and function. Using high-resolution mass spectrometry, we generated dynamic metabolome and proteome profiles of human primary naive T cells following activation. We discovered critical changes in the arginine metabolism that led to a drop in intracellular L-arginine concentration. Elevating L-arginine levels induced global metabolic changes including a shift from glycolysis to oxidative phosphorylation in activated T cells and promoted the generation of central memory-like cells endowed with higher survival capacity and, in a mouse model, anti-tumor activity. Proteome-wide probing of structural alterations, validated by the analysis of knockout T cell clones, identified three transcriptional regulators (BAZ1B, PSIP1, and TSN) that sensed L-arginine levels and promoted T cell survival. Thus, intracellular L-arginine concentrations directly impact the metabolic fitness and survival capacity of T cells that are crucial for anti-tumor responses.

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Dataset on dynamic metabolome/proteome profiles of activated human naive T cells

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Intracellular L-arginine levels regulate several metabolic pathways in T cells

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T cells with increased L-arginine display enhanced survival and anti-tumor activity

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LiP-MS identified proteins that are structurally modified by high L-arginine levels

Bispecific antibodies and CARs: generalized immunotherapeutics harnessing T cell redirection

To realize the full potential of cancer immunotherapy, the latest generation immunotherapeutics are designed to harness the potent tumor-killing capacity of T cells. Thus, to mobilize T cells, new optimized bispecific antibody (BsAb) designs, enabling efficient polyclonal redirection of cytotoxic activity through binding to CD3 and a Tumor Associated Antigen (TAA) and refined genetically modified T cells have recently expanded the arsenal of available options for cancer treatment. This review presents the current understanding of the parameters crucial to the design of optimal T cell redirecting BsAb and chimeric antigen receptor (CAR)-modified T cells. However, there are additional questions that require thorough elucidation. Both modalities will benefit from design changes that may increase the therapeutic window. One such approach could employ the discrimination afforded by multiple TAA to significantly increase selectivity.

CD19xCD3 DART protein mediates human B-cell depletion in vivo in humanized BLT mice

Novel therapeutic strategies are needed for the treatment of hematologic malignancies; and bispecific antibody-derived molecules, such as dual-affinity re-targeting (DART) proteins, are being developed to redirect T cells to kill target cells expressing tumor or viral antigens. Here we present our findings of specific and systemic human B-cell depletion by a CD19xCD3 DART protein in humanized BLT mice. Administration of the CD19xCD3 DART protein resulted in a dramatic sustained depletion of human CD19⁺ B cells from the peripheral blood, as well as a dramatic systemic reduction of human CD19⁺ B-cell levels in all tissues (bone marrow, spleen, liver, lung) analyzed. When human CD8⁺ T cells were depleted from the mice, no significant B-cell depletion was observed in response to CD19xCD3 DART protein treatment, confirming that human CD8⁺ T cells are the primary effector cells in this in vivo model. These studies validate the use of BLT humanized mice for the in vivo evaluation and preclinical development of bispecific molecules that redirect human T cells to selectively deplete target cells.

Characterization of the first-in-class T-cell-engaging bispecific single-chain antibody for targeted immunotherapy of solid tumors expressing the oncofetal protein claudin 6

The fetal tight junction molecule claudin 6 (CLDN6) is virtually absent from any normal tissue, whereas it is aberrantly and frequently expressed in various cancers of high medical need. We engineered 6PHU3, a T-cell-engaging bispecific single chain molecule (bi-(scFv)₂) with anti-CD3/anti-CLDN6 specificities, and characterized its pharmacodynamic properties. Our data show that upon engagement by 6PHU3, T cells strongly upregulate cytotoxicity and activation markers, proliferate and acquire an effector phenotype. 6PHU3 exerts potent killing of cancer cells in vitro with EC₅₀ values in the pg/mL range. Subcutaneous xenograft tumors in NSG mice engrafted with human PBMCs are eradicated by 6PHU3 treatment and survival of mice is significantly prolonged. Tumors of 6PHU3-treated mice are strongly infiltrated with activated CD4⁺, CD8⁺ T cells and T_EM type cells but not T_regs and display a general activation of a mostly inflammatory phenotype. These effects are only observed upon bispecific but not monospecific engagement of 6PHU3. Together with the exceptionally cancer cell selective expression of the oncofetal tumor marker CLDN6, this provides a safeguard with regard to toxicity. In summary, our data shows that the concept of T-cell redirection combined with that of highly selective targeting of CLDN6-positive solid tumors is effective. Thus, exploring 6PHU3 for clinical therapy is warranted.

Purified anti-CD3 × anti-HER2 bispecific antibody potentiates cytokine-induced killer cells of poor spontaneous cytotoxicity against breast cancer cells

Background

Chemical crosslinking is the most straightforward method to produce bispecific antibodies (BsAb) for arming ex vivo activated cytotoxic T lymphocytes. However, heterogeneous polymers are produced by chemical crosslinking. Currently, it is not known under what circumstances or to what extent further purification is needed.

Results

In this study, we purified Traut’s Reagent-Sulfo-SMCC crosslinked anti-CD3 × anti-HER2 by size-exclusion column chromatography and compared the capacity of the crude and the purified forms of the BsAb in enhancing cytokine-induced killer (CIK) cell-mediated cytotoxicity in vitro. We found that the purified BsAb assisted CIK cells more efficiently than the crude form only when the spontaneous cytotoxicity of the CIK cells was relatively low; otherwise, the two forms performed almost identically.

Conclusions

For the CIK cells of low spontaneous cytotoxicity, purified BsAb is a more powerful substitute for crude BsAb in enhancing their killing efficacy. However, that purification of BsAb is not necessary for robust CIK cells. This phenomenon also corroborates that CIK-mediated cytotoxicity is highly dependent on cell contact.

Electronic supplementary material

The online version of this article (doi:10.1186/2045-3701-4-70) contains supplementary material, which is available to authorized users.

Effects of intracellular calcium and actin cytoskeleton on TCR mobility measured by fluorescence recovery

BACKGROUND

The activation of T lymphocytes by specific antigen is accompanied by the formation of a specialized signaling region termed the immunological synapse, characterized by the clustering and segregation of surface molecules and, in particular, by T cell receptor (TCR) clustering.

METHODOLOGY/PRINCIPAL FINDINGS

To better understand TCR motion during cellular activation, we used confocal microscopy and photo-bleaching recovery techniques to investigate the lateral mobility of TCR on the surface of human T lymphocytes under various pharmacological treatments. Using drugs that cause an increase in intracellular calcium, we observed a decrease in TCR mobility that was dependent on a functional actin cytoskeleton. In parallel experiments measurement of filamentous actin by FACS analysis showed that raising intracellular calcium also causes increased polymerization of the actin cytoskeleton. These in vitro results were analyzed using a mathematical model that revealed effective binding parameters between TCR and the actin cytoskeleton.

CONCLUSION/SIGNIFICANCE

We propose, based on our results, that increase in intracellular calcium levels leads to actin polymerization and increases TCR/cytoskeleton interactions that reduce the overall mobility of the TCR. In a physiological setting, this may contribute to TCR re-positioning at the immunological synapse.

Spatial differences in active caspase-8 defines its role in T-cell activation versus cell death

Caspase-8, a cysteine-protease, initiates apoptosis when activated by death receptors. Caspase-8 is also essential for initiating T lymphocyte proliferation following T-cell antigen receptor (TCR) signaling. Given these disparate functions of caspase-8, we sought to determine whether this represented only a difference in the magnitude of caspase-8 activation, or different intracellular locations of active caspase-8. We demonstrate by high-resolution multicolor confocal laser scanning microscopy an aggregation of active caspase-8 within membrane lipid rafts in T cells stimulated with anti-CD3. This suggests that following TCR stimulation active caspase-8 physically interacts with lipid raft proteins, possibly to form a signaling platform. In contrast, Fas stimulation of T cells resulted in a much more profound activation of caspase-8 that was exclusively cytosolic. These confocal microscopic findings were confirmed using discontinuous sucrose gradient ultracentrifugation to isolate lipid raft versus cytosolic components. This sequestration model of caspase-8 activation was further supported by the observation that a classic caspase-8 substrate, BID, was not cleaved in CD3-stimulated T cells, but was cleaved after Fas engagement. Our data support a model that the location of active caspase-8 may profoundly influence its functional capacity as a regulator of either cell cycling or cell death.

Induction of adaptive Anti-HER2/neu immune responses in a Phase 1B/2 trial of 2B1 bispecific murine monoclonal antibody in metastatic breast cancer (E3194): a trial coordinated by the Eastern Cooperative Oncology Group

2B1 is a bispecific murine monoclonal antibody that binds to the extracellular domains of HER2/neu and FcgammaRIII. 2B1 efficiently promotes the lysis of tumor cells overexpressing HER2/neu by natural killer cells and mononuclear phagocytes that express the FcgammaRIII A isoform. Here, we report the results of E3194, a phase 1B/2 trial conducted by the Eastern Cooperative Oncology Group that employed 2B1 therapy in 20 women with metastatic breast cancer. The median age was 51 years. All but 1 patient had received prior chemotherapy. After the first dose, 3 of the initial 8 patients experienced dose-limiting toxicities that required dose-reduction. The nature of these dose-limiting toxicities resulted in a reduced dose from 2.5 mg/m/d to 1 mg/m/d in the remaining 12 patients. Objective antitumor responses were not seen. However, 2B1 therapy induced adaptive immune responses to both intracellular and extracellular domains of HER2/neu. Even though 2B1 antibody therapy did not show activity in metastatic breast cancer at the current administered doses, the ability of this antibody to induce detectable immune responses against an important tumor antigen has implications for understanding the mechanisms by which antibodies that mediate antibody-directed cellular cytotoxicity may exert their clinical antitumor effects.

Construction and Purification of a Covalently Linked Divalent Tandem Single-Chain Fv Antibody Against Placental Alkaline Phosphatase

Multivalency is a recognized means to increase the functional affinity of single-chain antibody fragments (scFvs) for optimizing tumor uptake at radioimmunotargeting. A unique divalent tandem single-chain Fv antibody [sc(Fv)2], based on the variable regions of the monoclonal antibody (MAb) H7, has now been generated. The antibody differs from other dimeric single-chain constructs in that a linker sequence (L) is introduced between the repeats of VL and VH domains (VL-L-VH-L-VL-L-VH). This construct was expressed as a His-tagged TrxA fusion protein in the Escherichia coli strain Origami B. Following cleavage with AcTev protease, the antibody was obtained in soluble and active form in E. coli and could be purified by Ni-NTA and cation-exchange chromatography. Purity and immunochemical properties were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), enzyme-linked immunosorbent assay (ELISA), Western blot, and Biacore analyses. The [sc(Fv)2] displayed proper stability and could be purified to homogeneity. This antibody also maintained immunoreactivity at 42 degrees C with only slight decrease at 52 degrees C. The high affinity displayed by the original antibody H7, 6.7 x 10(9) M(-1), was only slightly decreased to 1.2 x 10(9) M(-1) as determined by Biacore. The generation of such a divalent single-chain Fv with a molecular weight around 60 kd would be of value for clinical applications such as radioimmunolocalization and radioimmunotherapy.

Highly efficient redirected anti-tumor activity of human lymphocytes transduced with a completely human chimeric immune receptor

BACKGROUND

Novel antibody-based immunotherapeutic strategies exploit chimeric immune receptors (CIR), expressed on the surface of transduced human peripheral blood mononuclear cells (PBMC), to redirect potent non-MHC-dependent cytotoxicity to tumor cells expressing a tumor-associated antigen. However, clinical application of the strategy has been hampered by the potential side effects associated with immunogenicity and by low transduction efficiency.

METHODS

A fully human CIR was constructed that triggers immune activation through the zeta chain of CD3 and contains a human single-chain antibody fragment specific for an extracellular epitope of HER2. PBMC were transduced with the CIR using gibbon-ape leukemia virus envelope pseudotyped retroviruses. In vitro cytotoxicity and inhibition assays were carried out using normal and tumor cell lines expressing different levels of HER2.

RESULTS

Bulk populations of CIR-transduced PBMC could express high levels of the construct and subcloning ensured stable expression. CIR-mediated killing and growth inhibition of targets expressing high HER2 levels were very efficient at low effector-to-target ratios. Under the same experimental conditions, CIR-mediated activity against normal cells expressing low HER2 levels was marginal. The CIR-mediated recognition of target cells induced the release of soluble factors able to inhibit growth of both HER-positive and HER2-negative bystander tumor cells.

CONCLUSIONS

Human CIR-transduced PBMC exert a potent and dose-dependent anti-tumor activity. Target antigen level appeared to be a critical determinant of specificity and delivery of signals leading to redirected effector functions. Soluble factors, released by redirected effectors at the site of antigen-driven activation, mediate potent bystander killing.

Immunological Synapses Are Versatile Structures Enabling Selective T Cell Polarization

Helper T cells discriminate among different antigen-presenting cells to provide their help in a selective fashion. The molecular mechanisms leading to this exquisite selectivity are still elusive. Here, we demonstrate that immunological synapses are dynamic and adaptable structures allowing T cells to communicate with multiple cells. We show that T cells can form simultaneous immunological synapses with cells presenting different levels of antigenic ligands but eventually polarize toward the strongest stimulus. Remarkably, living T cells form discrete foci of signal transduction of different intensities during the interaction with different antigen-presenting cells and rapidly relocate TCR and Golgi apparatus toward the cell providing the strongest stimulus. Our results illustrate that, although T cell activation requires sustained signaling, T cells are capable of rapid synapse remodeling and swift polarization responses. The combination of sustained signaling with preferential and rapid polarization provides a mechanism for the high sensitivity and selectivity of T cell responses.

Bispecific Minibodies Targeting HER2/neu and CD16 Exhibit Improved Tumor Lysis When Placed in a Divalent Tumor Antigen Binding Format

Unconjugated monoclonal antibodies have emerged as important therapeutic agents for selected malignancies. One mechanism by which antibodies can exert cytotoxic effects is antibody-dependent cellular cytotoxicity (ADCC). In an effort to increase the efficiency of ADCC at tumor sites, we have focused on the construction of bispecific antibodies specific for the tumor antigen HER2/neu and the Fc gamma RIII-activating receptor (CD16) found on NK cells, mononuclear phagocytes, and neutrophils. Here, we describe the production of bispecific minibodies in two distinct binding formats. The parent minibody was constructed such that the IgG1 C(H)3 constant domain serves as the oligomerization domain and is attached to an anti-CD16 and an anti-HER2/ neu single-chain Fv via 19- and 29-amino acid linkers, respectively. This molecule can be expressed in mammalian cells from a dicistronic vector and has been purified using sequential affinity purification techniques. Analysis by surface plasmon resonance shows that the bispecific minibody can bind to HER2/neu and CD16, both individually and simultaneously. Furthermore, cytotoxicity studies show that the minibody can induce significant tumor cell lysis at a concentration as low as 20 nm. A trimeric, bispecific minibody (TriBi) that binds dimerically to HER2/neu and monomerically to CD16 induces equivalent cytotoxicity at lower antibody concentrations than either the parent minibody or the corresponding single-chain dimer. Both minibody constructs are stable in mouse and human serum for up to 72 h at 37 degrees C. These minibodies have the potential to target solid tumors and promote tumor lysis by natural killer cells and mononuclear phagocytes.

A novel recombinant bispecific single-chain antibody, bscWue-1 × CD3, induces T-cell-mediated cytotoxicity towards human multiple myeloma cells

The development of antibody-based strategies for the treatment of multiple myeloma (MM) has been hampered so far by the fact that suitable plasma cell-specific surface antigens have been missing. However, recently a novel monoclonal antibody, designated Wue-1, has been generated that specifically recognizes normal and malignant human plasma cells. Therefore, Wue-1 is an interesting and promising candidate to develop novel immunotherapeutic strategies for the treatment of MM. One variant for an antibody-based strategy is the bispecific antibody approach. Recombinant bispecific single-chain (bsc) antibodies are especially interesting candidates because they show exceptional biological properties. We have generated a novel MM-directed recombinant bsc antibody, bscWue-1 x CD3, and analyzed the biological properties of this antibody using the MM cell line NCI-H929 and primary cells from the bone marrow of patients with MM. We were able to show that bscWue-1 x CD3 induces efficient and selective T-cell-mediated cell death of NCI-H929 cells and primary myeloma cells in nine out of 11 cases. The bscWue-1 x CD3 Ab is efficacious even at low E:T ratios, and with or without additional T-cell pre- or costimulation. Target cell lyses were specific for Wue-1 antigen-positive cells and could be blocked by the Wue-1 monoclonal antibody.

Induction of human T lymphocyte cytotoxicity and inhibition of tumor growth by tumor-specific diabody-based molecules secreted from gene-modified bystander cells

Infiltrating T cells are found in many malignancies, but they appear to be mostly anergic and do not attack the tumor, presumably because of the absence of activation and/or costimulatory signals. We describe a strategy for cellular antitumor immunotherapy by the in situ production of soluble bifunctional Ab-based molecules that activate and retarget T cells to the tumor. We genetically modified cells to simultaneously secrete two bifunctional molecules, a bispecific diabody directed against the carcinoembryonic Ag (CEA) and the CD3 epsilon chain of the TCR (alphaCEA x alphaCD3), and a fusion protein comprising the extracellular portion of B7-1 fused to a bivalent anti-CEA diabody (B7-alphaCEA). Together, alphaCEA x alphaCD3 and B7-alphaCEA proved potent at inducing the activation, proliferation, and survival of primary human T cells. When producer cells were cocultured with primary T cells and CEA(+) cancer cells, alphaCEA x alphaCD3 and B7-alphaCEA acted in combination to activate and retarget T cell cytotoxicity and completely abrogate tumor growth in the coculture. Furthermore, the introduction of just a few such producer cells at the tumor site efficiently inhibited the growth of established human colon carcinoma xenografts. Despite a cumbersome generation process, the use of autologous gene-modified producer cells opens the way for a new diabody-based gene therapy strategy of cancer.

Efficient elimination of chronic lymphocytic leukaemia B cells by autologous T cells with a bispecific anti-CD19/anti-CD3 single-chain antibody construct

Recently, we have shown that a novel recombinant bispecific single-chain antibody construct (bscCD19 x CD3), induces highly efficacious lymphoma-directed cytotoxicity mediated by unstimulated peripheral T lymphocytes. Functional analysis of bscCD19 x CD3 has so far been exclusively performed with human B lymphoma cell lines and T cells from healthy donors. Here we analysed the properties of bscCD19 x CD3 using primary B cells and autologous T cells from healthy volunteers or patients with B-cell chronic lymphocytic leukaemia (B-CLL). We show that bscCD19 x CD3 induces T-cell-mediated depletion of nonmalignant B cells in all four cases and depletion of primary lymphoma cells in 22 out of 25 cases. This effect could be observed at low effector-to-target (E:T) ratios and in the majority of cases without additional activation of autologous T cells by IL-2. Even in samples derived from patients heavily pretreated with different chemotherapy regimens, strong cytotoxic effects of bscCD19 x CD3 could be observed. The addition of bscCD19 x CD3 to patients' cells resulted in an upregulation of activation-specific cell surface antigens on autologous T cells and elevated levels of CD95 on lymphoma B cells. Although anti-CD95 antibody CH-11 failed to induce apoptosis in lymphoma cells, we provide evidence that B-CLL cell depletion by bscCD3 x CD3 is mediated at least in part by apoptosis via the caspase pathway.

Down-modulation of responses to type I IFN upon T cell activation

The immunomodulatory role of type I IFNs (IFN-alpha/beta) in shaping T cell responses has been demonstrated, but the direct effects of IFN on T cells are still poorly characterized. Particularly, because IFN exert an antiproliferative activity, it remains elusive how the clonal expansion of effector T cells can paradoxically occur in the event of an infection when large amounts of IFN are produced. To address this issue, we have studied the effects of type I IFN in an in vitro differentiation model of human primary CD4(+) T cells. We found that IFN-alpha treatment of resting naive T cells delayed their entry into the cell cycle after TCR triggering. Conversely, the ongoing expansion of effector T cells was not inhibited by the presence of IFN. Moreover, activated T cells showed a significantly reduced induction of IFN-sensitive genes, as compared with naive precursors, and this decline occurred independently of subset-specific polarization. The residual type I IFN response measured in activated T cells was found sufficient to inhibit replication of the vesicular stomatitis virus. Our data suggest that the activation of T lymphocytes includes regulatory processes that restrain the transcriptional response to IFN and allow the proliferation of effector cells in the presence of this cytokine.

Genetic engineering of T cell specificity for immunotherapy of cancer

The ultimate goal of immunotherapy of cancer is to make use of the immune system of patients to eliminate malignant cells. Research has mainly focused on the generation of effective antigen specific T-cell responses because of the general belief that T-cell immunity is essential in controlling tumor growth and protection against viral infections. However, the isolation of antigen specific T cells for therapeutic application is a laborious task and it is often impossible to derive autologous tumor specific T cells to be used for adoptive immunotherapy. Therefore, strategies were developed to genetically transfer tumor specific immune receptors into patients T cells. To this end, chimeric receptors were constructed that comprise antibody fragments specific for tumor associated antigens, linked to genes encoding signaling domains of the T-cell receptor (TCR) or Fc receptor. T cells expressing such chimeric antibody receptors recapitulate the immune specific responses mediated by the introduced receptor. Recently, we introduced chimeric TCR genes into primary human T lymphocytes and demonstrated that these T cell transductants acquired the exquisite major histocompatibility complex (MHC) restricted tumor specificity dictated by the introduced TCR. Importantly, the introduction of chimeric TCR bypasses problems associated with the introduction of nonmodified TCR genes, such as pairing of introduced TCR chains with endogenous TCR chains and unstable TCRalpha expression. A novel strategy which is completely independent of available tumor specific T-cell clones for cloning of the TCR genes was recently used to transfer MHC restricted tumor specificity to T cells. Human "TCR-like" Fab fragments obtained by in vitro selection of Fab phages on soluble peptide/MHC complexes were functionally expressed on human T lymphocytes, resulting in MHC restricted, tumor specific lysis and cytokine production. In addition, affinity maturation of the antibody fragment on Fab phages allows improvement of the tumor cell killing capacity of chimeric Fab receptor engrafted T cells. Developments in retroviral transfer technology now enables the generation of large numbers of antigen specific T cells that can be used for adoptive transfer to cancer patients. In this article we summarize the developments in adoptive T cell immunogenetic therapy and discuss the limitations and perspectives to improve this technology toward clinical application.

Protocol for gene transduction and expansion of human T lymphocytes for clinical immunogene therapy of cancer

In preparation of a clinical phase I/II study in renal cell carcinoma (RCC) patients, we developed a clinically applicable protocol that meets good clinical practice (GCP) criteria regarding the gene transduction and expansion of primary human T lymphocytes. We previously designed a transgene that encodes a single chain (sc) FvG250 antibody chimeric receptor (ch-Rec), specific for a RCC tumor-associated antigen (TAA), and that genetically programs human T lymphocytes with RCC immune specificity. Here we describe the conditions for activation, gene transduction, and proliferation for primary human T lymphocytes to yield: (a) optimal functional expression of the transgene; (b) ch-Rec-mediated cytokine production, and (c) cytolysis of G250-TAA(POS) RCC by the T-lymphocyte transductants. Moreover, these parameters were tested at clinical scale, i.e., yielding up to 5-10 x 10(9) T-cell transductants, defined as the treatment dose according to our clinical protocol. The following parameters were, for the first time, tested in an interactive way: (1) media compositions for production of virus by the stable PG13 packaging cell; (2) T-lymphocyte activation conditions and reagents (anti-CD3 mAb; anti-CD3+anti-CD28 mAbs; and PHA); (3) kinetics of T-lymphocyte activation prior to gene transduction; (4) (i) T-lymphocyte density, and (ii) volume of virus-containing supernatant per surface unit during gene transduction; and (5) medium composition for T-lymphocyte maintenance (i) in-between gene transduction cycles, and (ii) during in vitro T-lymphocyte expansion. Critical to gene transduction of human T lymphocytes at clinical scale appeared to be the use of the fibronectin fragment CH-296 (Retronectin) as well as Lifecell) X-fold cell culture bags. In order to comply with GCP requirements, we used: (a) bovine serum-free human T-lymphocyte transduction system, i.e., media supplemented with autologous patients' plasma, and (b) a closed cell culture system for all lymphocyte processing. This clinical protocol routinely yields 30-65% scFvG250 ch-Rec(POS) T lymphocytes in both healthy donors and RCC patients.

Construction of a bispecific single chain antibody for recruitment of cytotoxic T cells to the tumour stroma associated antigen fibroblast activation protein

Bispecific antibodies directed against tumour associated antigens and the T cell receptor component CD3 for recruitment and tumour targeted activation of T cells represent a novel class of highly specific immunotherapeutics for cancer. We here describe the construction, eukaryotic expression and in vitro functional activity of a new T cell activating bispecific reagent, termed TTS for T cell targeting to the tumour stroma, comprised of a CD3 specific single chain antibody derivative (scFv) fused C-terminally to a 'fibroblast activation protein' (FAP) specific scFv that targets cytotoxic effector cells to FAP. FAP is highly expressed in the vascularised tumoural stroma of most lung, breast and colon carcinomas. It thus represents a selectively tumour associated, yet common marker of many solid tumours and is a potentially ideal candidate marker for efficient targeting of immune effector cells.

New approaches to antibody therapy

Antibody-based therapy of human cancers has led to several remarkable outcomes, particularly in the therapy of breast cancer and lymphoma. Many solid tumors have proven less responsive, due in part to difficulties in the tumor-selective delivery of antibodies and potential cytolytic effectors. However, antibodies that directly perturb signaling mechanisms in cells derived from epithelial malignancies have shown benefit; examples include antibodies directed against the extracellular domains of HER2/neu and epidermal growth factor receptor. A long-term goal of immunotherapy has been to induce anti-tumor inflammatory responses that can directly cause tumor regression or induce adaptive responses against tumor-related antigens. This review focuses on the use of antibodies to provide a means for initiating anti-tumor immune responses, and on the use of antibodies as delivery vehicles of radionuclides.

Fyn-binding protein (Fyb)/SLP-76-associated protein (SLAP), Ena/vasodilator-stimulated phosphoprotein (VASP) proteins and the Arp2/3 complex link T cell receptor (TCR) signaling to the actin cytoskeleton

T cell receptor (TCR)-driven activation of helper T cells induces a rapid polarization of their cytoskeleton towards bound antigen presenting cells (APCs). We have identified the Fyn- and SLP-76-associated protein Fyb/SLAP as a new ligand for Ena/ vasodilator-stimulated phosphoprotein (VASP) homology 1 (EVH1) domains. Upon TCR engagement, Fyb/SLAP localizes at the interface between T cells and anti-CD3-coated beads, where Evl, a member of the Ena/VASP family, Wiskott-Aldrich syndrome protein (WASP) and the Arp2/3 complex are also found. In addition, Fyb/SLAP is restricted to lamellipodia of spreading platelets. In activated T cells, Fyb/SLAP associates with Ena/VASP family proteins and is present within biochemical complexes containing WASP, Nck, and SLP-76. Inhibition of binding between Fyb/SLAP and Ena/VASP proteins or WASP and the Arp2/3 complex impairs TCR-dependent actin rearrangement, suggesting that these interactions play a key role in linking T cell signaling to remodeling of the actin cytoskeleton.

A recombinant bispecific single-chain antibody, CD19 × CD3, induces rapid and high lymphoma-directed cytotoxicity by unstimulated T lymphocytes

Although bispecific antibodies directed against malignant lymphoma have been shown to be effective in vitro and in vivo, extended clinical trials so far have been hampered by the fact that conventional approaches to produce these antibodies suffer from low yields, ill-defined byproducts, or laborious purification procedures. To overcome this problem, we have generated a small, recombinant, lymphoma-directed, bispecific single-chain (bsc) antibody according to a novel technique recently described. The antibody consists of 2 different single-chain Fv fragments joined by a glycine-serine linker. One specificity is directed against the CD3 antigen of human T cells, and the other antigen-binding site engages the pan–B-cell marker CD19, uniformly expressed on the vast majority of B-cell malignancies. The construct was expressed in Chinese hamster ovary cells and purified by its C-terminal histioline tag. Specific binding to CD19 and CD3 was demonstrated by fluorescence-activated cell sorter analysis. By redirecting unstimulated primary human T cells derived from the peripheral blood against CD19-positive lymphoma cells, the bscCD19 × CD3 antibody showed significant cytotoxic activity at very low concentrations of 10 to 100 pg/mL and at effector to target cell ratios as low as 2:1. Moreover, strong lymphoma-directed cytotoxicity at low antibody concentrations was rapidly induced during 4 hours even in experiments without any T-cell prestimulation. Thus, this particular antibody proves to be much more efficacious than the bispecific antibodies described until now. Therefore, the described bscCD19 × CD3 molecule should be a suitable candidate to prove the therapeutic benefit of bispecific antibodies in the treatment of non-Hodgkin lymphoma.

1 Alpha,25-dihydroxyvitamin D3 inhibits differentiation, maturation, activation, and survival of dendritic cells leading to impaired alloreactive T cell activation

1 Alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3), the active form of vitamin D3, is a potent immunomodulatory agent. Here we show that dendritic cells (DCs) are major targets of 1,25(OH)2D3-induced immunosuppressive activity. 1,25(OH)2D3 prevents the differentiation in immature DCs of human monocytes cultured with GM-CSF and IL-4. Addition of 1,25(OH)2D3 during LPS-induced maturation maintains the immature DC phenotype characterized by high mannose receptor and low CD83 expression and markedly inhibits up-regulation of the costimulatory molecules CD40, CD80, and CD86 and of class II MHC molecules. This is associated with a reduced capacity of DCs to activate alloreactive T cells, as determined by decreased proliferation and IFN-gamma secretion in mixed leukocyte cultures. 1, 25(OH)2D3 also affects maturing DCs, leading to inhibition of IL-12p75 and enhanced IL-10 secretion upon activation by CD40 ligation. In addition, 1,25(OH)2D3 promotes the spontaneous apoptosis of mature DCs. The modulation of phenotype and function of DCs matured in the presence of 1,25(OH)2D3 induces cocultured alloreactive CD4+ cells to secrete less IFN-gamma upon restimulation, up-regulate CD152, and down-regulate CD154 molecules. The inhibition of DC differentiation and maturation as well as modulation of their activation and survival leading to T cell hyporesponsiveness may explain the immunosuppressive activity of 1, 25(OH)2D3.

Switch in chemokine receptor expression upon TCR stimulation reveals novel homing potential for recently activated T cells

When naive T lymphocytes are activated and differentiate into memory/effector cells, they down-regulate receptors for constitutive chemokines such as CXCR4 and CCR7 and acquire receptors for inflammatory chemokines such as CCR3, CCR5 and CXCR3, depending on the Th1/Th2 polarization. This switch in chemokine receptor usage leads to the acquisition of the capacity to migrate into inflamed tissues. Using RNase protection assays, staining with specific antibodies, and response to recombinant chemokines, we now show that following TCR stimulation, memory/effector T cells undergo a further and transient switch in receptor expression. CCR1, CCR2, CCR3, CCR5, CCR6 and CXCR3 are down-regulated within 6 h, while CCR7, CCR4, CCR8 and CXCR5 are up-regulated for 2 to 3 days. Up-regulation of CCR7 following TCR stimulation was observed also among resting peripheral blood T cells and required neither co-stimulation nor exogenous IL-2. On the other hand IL-2 down-regulated CXCR5, up-regulated CCR8 and facilitated the recovery of CCR3 and CCR5. Upon TCR stimulation, Th1 and Th2 cells produced comparable sets of chemokines, including RANTES, macrophage inflammatory protein-1beta, I-309, IL-8 and macrophage-derived chemokine, which may modulate surface chemokine receptors and contribute to cell recruitment at sites of antigenic recognition. Altogether these results show that following TCR stimulation effector/memory T cells transiently acquire responsiveness to constitutive chemokines. As a result, T cells that are activated in tissues may either recirculate to draining lymph nodes or migrate to nearby sites of organized ectopic lymphoid tissues.

Interleukin-12 induces expression of interferon regulatory factor-1 via signal transducer and activator of transcription-4 in human T helper type 1 cells

IRF-1-deficient mice show a striking defect in the development of T helper 1 (Th1) cells. In the present report, we investigate the expression of IRF-1 during differentiation of human T helper cells. No significant differences of IRF-1 mRNA expression were found in established Th1 and Th2 cells; however, interleukin 12 (IL-12) induced a strong up-regulation of IRF-1 transcripts in Th1 but not in Th2 cells. We demonstrate that IL-12-induced up-regulation of IRF-1 is mediated by signal transducer and activator of transcription-4, which binds to the interferon (IFN)-gamma-activated sequence present in the promoter of the IRF-1 gene. Strong IL-12-dependent activation of a reporter gene construct containing the IRF-1 IFN-gamma-activated sequence element provides further evidence for the key role of signal transducer and activator of transcription-4 in the IL-12-induced up-regulation of IRF-1 transcripts in T cells. IRF-1 expression was strongly induced after stimulation of naive CD4(+) T cells via the T cell receptor, irrespective of the cytokines present at priming, indicating that this transcription factor does not play a major role in initiating a Th1-specific transcriptional cascade in differentiating helper T cells. However, our finding that IRF-1 is a target gene of IL-12 suggests that some of the IL-12-induced effector functions of Th1 cells may be mediated by IRF-1.

Level of anti-mouse-antibody response induced by bi-specific monoclonal antibody OC/TR in ovarian-carcinoma patients is associated with longer survival

More than 60% of cancer patients injected with intact murine monoclonal antibody (MAb) develop a humoral response against the antigen even after a single dose. Analysis of a series of 35 ovarian-cancer patients entered in phase-I and -II clinical studies of T-cells retargeted with the bi-specific F(ab')2 OC/TR revealed: (i) a detectable human anti-mouse antibody (HAMA) response in 31/35 (88%) patients, with high HAMA levels (> or = 150 ng/ml) in 18/31 (58%) cases by the end of the treatment; (ii) no correlation between HAMA levels and the form of delivery of the mAb (OC/TR bound to T cells or bound plus soluble), time schedule or cumulative dose; (iii) an association between high HAMA levels and favorable clinical parameters and response to immunotherapy; and (iv) a significantly longer median survival probability in patients with high HAMA levels than in patients with lower HAMA levels, even when the sub-group of non-responder patients was considered. Evaluation of the anti-idiotypic response in HAMA-positive sera indicated that 11/17 sera showed high-titer (>6000) binding of OC/TR, as evaluated by a specific radioimmunoassay, and 15/18 and 16/16 sera specifically inhibited the binding of the MOv18 and anti-CD3 parental MAbs to ovarian-carcinoma cells and T lymphocytes respectively. Of 7 patients evaluated for duration of the HAMA response, 5 showed stable or even increased HAMA levels. The long-lasting HAMA response maintained an anti-idiotypic component, directed mainly against the alphaCD3 idiotype of bi-MAb OC/TR in 2 out of 3 cases tested.

Therapeutic strategies targeting proteins that regulate folate and reduced folate transport

Folate is an essential vitamin which acts as a precursor for cofactors that regulate a variety of biochemical reactions. Cellular uptake of endogenous folates as well as antifolate agents such as methotrexate may be regulated by two independent transport proteins, the folate receptor and the reduced folate carrier. This paper reviews the molecular and functional characteristics of these transport systems and potential therapeutic approaches exploiting these targets in the treatment of cancer. Understanding of the molecular basis and functional characteristics of the transport of endogenous folates and folate analogs via the folate receptor and the reduced folate carrier has led to the development of novel antifolate agents through rational drug design and targeted therapeutic approaches for tumors that express or lack the presence of these transport proteins. With this knowledge, new and selective treatment will become available to more effectively treat patients with a variety of malignancies.

The Role of Stat4 in Species-Specific Regulation of Th Cell Development by Type I IFNs

Type I IFNs (IFN-α/β), in addition to IL-12, have been shown to play an important role in the differentiation of human, but not mouse, Th cells. We show here that IFN-α/β act directly on human T cells to drive Th1 development, bypassing the need for IL-12-induced signaling, whereas IFN-α cannot substitute IL-12 for mouse Th1 development. The molecular basis for this species specificity is that IFN-α/β activate Stat4 in differentiating human, but not mouse, Th cells. Unlike IL-12, which acts only on Th1 cells, IFN-α/β can activate Stat4 not only in human Th1, but also in Th2 cells. However, restimulation of human Th2 lines and clones in the presence of IFN-α does not induce the production of IFN-γ. These results suggest that activation of Stat4, which is necessary for the differentiation of naive T cells into polarized Th1 cells, is not sufficient to induce phenotype reversal of human Th2 cells.

Development of a bispecific monoclonal antibody as a universal immunoprobe for detecting biotinylated macromolecules

Bispecific monoclonal antibody (BsMab) combining two different antigen binding sites, anti-biotin and anti-HRPO paratopes, could be used as a universal immunoprobe for detecting all biotinylated macromolecules. First, a mouse hybridoma cell line secreting monospecific anti-biotin Mab was generated and characterized. Second, a quadroma cell line which could continuously secrete bsMab (anti-biotin x anti-HRPO) was developed by a nonselective microelectrofusion method. The supernatant containing bsMab was collected from tissue culture medium and purified with two affinity columns. This bsMab has comparable avidity to commercial streptavidin-HRPO when tested against biotinylated macromolecules. Compared to streptavidin, this bsMab can bind the enzyme and thus eliminate the need for chemical conjugation. This bsMab can be used as a promising immunoprobe for detecting many macromolecules bearing biotin markers, such as protein, phage, liposome and DNA in different bioassay systems.

Activated murine B lymphocytes and dendritic cells produce a novel CC chemokine which acts selectively on activated T cells

Genes were isolated using the suppression subtractive hybridization method by stimulation of pro/pre B cells with anti-CD40 and interleukin (IL)-4 to mature S mu-Sepsilon-switched cells. One of the strongly upregulated genes encodes a novel murine CC chemokine we have named ABCD-1. The ABCD-1 gene has three exons separated by 1. 2- and 2.7-kb introns. It gives rise to a 2.2-kb transcript containing an open reading frame of 276 nucleotides. Two polyadenylation sites are used, giving rise to cDNAs with either 1550 or 1850 bp of 3' untranslated regions. The open reading frame encodes a 24 amino acid-long leader peptide and a 68 amino acid-long mature protein with a predicted molecular mass of 7.8 kD. ABCD-1 mRNA is found in highest quantities in activated splenic B lymphocytes and dendritic cells. Little chemokine mRNA is present in lung, in unstimulated splenic cells, in thymocytes, and in lymph node cells. No ABCD-1 mRNA is detected in bone marrow, liver, kidney, or brain, in peritoneal exudate cells as well as in the majority of all unstimulated B lineage cells tested. It is also undetectable in Concanavalin A-activated/IL-2-restimulated splenic T cells, and in bone marrow-derived IL-2-induced natural killer cells and IL-3-activated macrophages. Recombinant ABCD-1 revealed a concentration-dependent and specific migration of activated splenic T lymphoblasts in chemotaxis assays. FACS(R) analyses of migrated cells showed no preferential difference in migration of CD4(+) versus CD8(+) T cell blasts. Murine as well as human T cells responded to ABCD-1. Freshly isolated cells from bone marrow, thymus, spleen, and lymph node, IL-2-activated NK cells, and LPS-stimulated splenic cells, all did not show any chemotactic response. Thus, ABCD-1 is the first chemokine produced in large amounts by activated B cells and acting selectively on activated T lymphocytes. Therefore, ABCD-1 is expected to play an important role in the collaboration of dendritic cells and B lymphocytes with T cells in immune responses.

Chimeric scFv/gamma receptor-mediated T-cell lysis of tumor cells is coregulated by adhesion and accessory molecules

Adhesion and accessory molecules play a critical role in T-cell activation and effector function in general and in tumor cell recognition and lysis in particular. We investigated the contribution of CD2, CD3, CD11a/CD18, CD54 and CD58 molecules in T lymphocyte-tumor cell interactions mediated by chimeric immunoglobulin receptors. The chimeric receptor is composed of a single chain antibody binding site and a gamma-chain signal transducing molecule (scFv/gamma). T lymphocytes expressing such scFv/gamma receptors recognize the G250 Ag on renal cell carcinoma (RCC) in an major histocompatibility complex (MHC)-unrestricted manner and exert RCC selective cytolysis. A coregulatory role for CD2, CD3 and CD11a/CD18 molecules in scFv/gamma-mediated cytolysis was demonstrated using monoclonal antibody (MAb)-induced inhibition of scFv/gamma-mediated cytolysis. The inhibition of lysis was not due to inhibition of cytotoxic T lymphocyte (CTL)-target cell conjugation but rather to a post-conjugate signaling event. Binding of CD54 and CD58 MAbs to the RCC did not inhibit cytolysis of RCC cells that expressed high levels of both CD54 and the G250 antigen (Ag) (A75), whereas cytolysis of RCC expressing intermediate levels of CD54 and G250 Ag (SK-RC-17 cl.4) was partly inhibited by the CD54 MAb. Binding of low concentrations of G250 MAb to RCC (A75) rendered these cells sensitive to CD54 MAb inhibition, demonstrating a direct functional relation between G250 Ag expression level and adhesion molecules. Taken together, our findings indicate a coregulatory role for CD2, CD3 and CD11a/CD18 molecules in the scFv/gamma-mediated cytolysis of tumor cells and show that the requirement of CD11a/CD18-CD54 interactions is dependent on the level of free Ag. This make these gene-transduced T lymphocytes attractive tools for adoptive immunogene therapy of cancer.

Bispecific antibodies for treatment of cancer in experimental animal models and man

Immunotherapy is a powerful anti-cancer treatment modality. However, despite numerous encouraging results obtained in pre-clinical studies, a definite breakthrough towards an established clinical treatment modality has as yet not occurred. Antibodies against tumor antigens have been shown to localise at the site of the tumor, but inadequate triggering of immune effector mechanisms have thwarted clinical efficacy thus far. Cellular immunotherapy has been hampered by limitations such as lack of specificity, down-regulation of major histocompatibility complex (MHC)-expression or Fas ligand up-regulation on tumor cells. This review focuses on the use of bispecific antibodies (BsAbs) for immunotherapy of cancer. Using BsAbs, it is possible to take advantage of the highly specific binding characteristics of antibodies and combine these with the powerful effector functions of cytotoxic immune effector cells. BsAbs share two different, monoclonal antibody-derived, antigen-recognizing moieties within one molecule. By dual binding, BsAbs reactive with a trigger molecule on an immune effector cell on the one hand and a surface antigen on a tumor target cell on the other are thus able to functionally focus the lytic activity of the immune effector cell towards the target cell. Over the last few years, the concept of BsAb-mediated tumor cell killing has been studied extensively both in preclinical models and in a number of phase I clinical trials. Promising pre-clinical results have been reported using tumor models in which diverse immune effector cell populations have been used. Despite this pre-clinical in vivo efficacy, the first clinical trials indicate that we are still not in a position to successfully treat human malignancies. This review discusses the production of BsAbs, the choice of trigger molecules in combination with potential effector cells and the preclinical models that have led to the current use of BsAbs in experimental clinical trials. It has become clear that appropriate immune cell activation and establishing a favourable effector-to-target cell ratio will have direct impact on the efficacy of the therapeutic approaches using BsAbs. New directions are discussed, i.e. finding appropriate dosage schemes by which immune effector cells become redirected without inducing hyporesponsiveness, defining possibilities for combining different immune effector cell populations and creating an in situ tumor environment that allows maximal tumoricidal activity

Comparison of three different methods for radiolabelling human activated T lymphocytes

One approach in the treatment of ovarian cancer patients involves the infusion of autologous T lymphocytes coupled with a bispecific monoclonal antibody MOv18/anti-CD3 (biMAb OC/TR), which recognizes a 38-kDa glycoprotein expressed on ovarian carcinomas and the CD3 T cell receptor. However, little is known about the in vivo biodistribution of injected activated lymphocytes, information that could be obtained by scintigraphic imaging of radiolabelled T cells in order to visualize the migratory pattern. We compared the efficiency, stability and toxicity of technetium-99m hexamethylpropylene amine oxime (HMPAO), indium-111 oxine and fluorine-18 2-fluoro-2-deoxy-d-glucose (FDG) in radiolabelling activated lymphocytes targeted with biMAb OC/TR. The mean labelling efficiencies of 111In-oxine and 18F-FDG using 2.5x10(8) lymphocytes (68% and 64%, respectively) were more than twice that of 99mTc-HMPAO (31%). Retention of the radionuclide in the cell was highest in the case of 111In-oxine labelling (less than 25% of the initial cell-bound activity released after 240 min, as compared with 44% of the 99mTc label in the same period and 45% of 18F radionuclide released after 150 min). None of the three radiolabelling reagents induced any significant alteration in cell viability or immunophenotype. However, both 111In-oxine and 18F-FDG induced a loss of cytotoxic activity of lymphocytes against the ovarian carcinoma cell line IGROV1, and all three radiolabelling reagents caused a significant reduction in the proliferative ability of labelled lymphocytes compared to controls, with cell death occurring after 8-9 days. Radiolabelling with the more stable 111In-oxine reagent using a higher number of lymphocytes (1.4x10(9)) but the same total activity (around 55.5 MBq) resulted in improved labelled T cell viability and proliferative ability, although the mean labelling efficiency decreased (35.8%). Together the data suggest that 111In-oxine at low activity per cell is the most appropriate reagent for radiolabelling activated retargeted T lymphocytes useful for in vivo biodistribution studies.

Selective expression of an interleukin-12 receptor component by human T helper 1 cells

Interleukin-12 (IL-12), a heterodimeric cytokine produced by activated monocytes and dendritic cells, plays a crucial role in regulating interferon (IFN)-gamma production and in the generation of IFN-gamma-producing T helper 1 (Th1) cells. Here we show that the IL-12 receptor (IL-12R) beta 2 subunit, a recently cloned binding and signal transducing component of the IL-12R, is expressed on human Th1 but not Th2 clones and is induced during differentiation of human naive cells along the Th1 but not the Th2 pathway. IL-12 and type I but not type II interferons induce expression of the IL-12R beta 2 chain during in vitro T cell differentiation after antigen receptor triggering. The selective expression and regulation of the IL-12R beta 2 subunit may help to understand the basis of Th1/Th2 differentiation and may provide therapeutic options for altering the Th1/Th2 balance in several immuno-pathological conditions such as autoimmune diseases and allergies.

Identification of a committed T cell precursor population in adult human peripheral blood

Here, we report data concerning the discovery in adult human peripheral blood of a precursor cell population able to differentiate into CD4+CD3+ alpha beta + mature T cells. These cells, which represent 0.1-0.5% of total peripheral blood mononuclear cells (PBMC), express substantial levels of CD4, but lack CD3 surface expression. At a molecular level, they express the pre-T cell receptor alpha (pT alpha) gene, CD3-gamma, CD-delta and CD-epsilon, and RAG-1 recombination enzyme and have initiated rearrangements in the T cell receptor (TCR)-beta locus (D-J). Moreover, low levels of CD3 epsilon protein, but not of TCR-beta chain, can be detected in their cytoplasm. Our results suggest that CD4+CD3- cells identified in peripheral blood are different from CD3-CD4+CD8- thymocytes and may contain precursors of an extrathymic T cell differentiation pathway.