A Novel Bispecific Tetravalent Antibody Fusion Protein to Target Costimulatory Activity for T-cell Activation to Tumor Cells Overexpressing ErbB2/HER2

Adoptive antitumor immunotherapy in vitro and in vivo using genetically activated erbB2-specific T cells

The use of human T lymphocytes genetically modified to express chimeric antigen receptors on their surfaces has emerged as a promising treatment strategy for malignant tumors. We have transfected primary human peripheral T lymphocytes with a recombinant vector carrying DNA fragments encoding anti-erbB2 scFv/Fc/CD28/CD3ζ chimeric antigen receptor using electroporation. Transfected T cells have been demonstrated to express anti-erB2 scFv/Fc on their surface and CD28/CD3ζ intracellularly. These modified T cells were able to specifically bind to erbB2 tumor-associated antigen on target tumor cells. After specific binding, modified T cells were activated to produce high levels of cytokines (not only interferon-γ but also interluekin-2) and mediate lysis of erbB2-positive human tumor cells in an antigen-specific manner. Furthermore, such genetically modified human T cells significantly delayed the growth of subcutaneous erbB2-positive human xenograft tumors after systemic administration. These preclinical studies suggest that human T cells can be modified genetically and redirected to tumors in cancer patients.

Immunomodulatory effects of polysaccharide from marine fungus Phoma herbarum YS4108 on T cells and dendritic cells

YCP, as a kind of natural polysaccharides from the mycelium of marine filamentous fungus Phoma herbarum YS4108, has great antitumor potential via enhancement of host immune response, but little is known about the molecular mechanisms. In the present study, we mainly focused on the effects and mechanisms of YCP on the specific immunity mediated by dendritic cells (DCs) and T cells. T cell /DC activation-related factors including interferon- (IFN-) γ, interleukin-12 (IL-12), and IL-4 were examined with ELISA. Receptor knock-out mice and fluorescence-activated cell sorting are used to analyze the YCP-binding receptor of T cells and DCs. RT-PCR is utilized to measure MAGE-A3 for analyzing the tumor-specific killing effect. In our study, we demonstrated YCP can provide the second signal for T cell activation, proliferation, and IFN-γ production through binding to toll-like receptor- (TLR-) 2 and TLR-4. YCP could effectively promote IL-12 secretion and expression of markers (CD80, CD86, and MHC II) via TLR-4 on DCs. Antigen-specific immunity against mouse melanoma cells was strengthened through the activation of T cells and the enhancement of capacity of DCs by YCP. The data supported that YCP can exhibit specific immunomodulatory capacity mediated by T cells and DCs.

Gene therapy of malignant solid tumors by targeting erbB2 receptors and by activating T cells

One of the strategies to improve the outcome of anti-erbB2-mediated immunotherapy is to combine anti-erbB2 antibodies with T-cell-based adoptive immunotherapy, which can be achieved by expressing anti-erbB2 mAb on the surface of T cells. A single-chain variable fragment (scFv) from an anti-erbB2 mAb has been expressed on T cell surface to bind to erbB2-positive cells, and CD3ζ has been expressed as a fusion partner at C terminus of this scFv to transduce signals. T cells grafted with this chimeric scFv/CD3ζ were able to specifically attack target tumor cells with no MHC/Ag restriction. To test the effects of CD28 signal on cellular activation and antitumor effectiveness of chimeric scFv/CD3ζ-modified T cells, we constructed a recombinant anti-erbB2 scFv/Fc/CD28/CD3ζ gene in a retroviral vector. T cells expressing anti-erbB2 scFv/Fc/CD28/CD3ζ specifically lyzed erbB2-positive target tumor cells and secreted not only interferon-γ (IFN-γ) but also IL-2 after binding to their target cells. Our data indicate that CD3 and CD28 signaling can be delivered in one molecule, which is sufficient for complete T cell activation without exogenous B7/CD28 co-stimulation.

Maltose-binding protein enhances secretion of recombinant human granzyme B accompanied by in vivo processing of a precursor MBP fusion protein

BACKGROUND

The apoptosis-inducing serine protease granzyme B (GrB) is an important factor contributing to lysis of target cells by cytotoxic lymphocytes. Expression of enzymatically active GrB in recombinant form is a prerequisite for functional analysis and application of GrB for therapeutic purposes.

METHODS AND FINDINGS

We investigated the influence of bacterial maltose-binding protein (MBP) fused to GrB via a synthetic furin recognition motif on the expression of the MBP fusion protein also containing an N-terminal α-factor signal peptide in the yeast Pichia pastoris. MBP markedly enhanced the amount of GrB secreted into culture supernatant, which was not the case when GrB was fused to GST. MBP-GrB fusion protein was cleaved during secretion by an endogenous furin-like proteolytic activity in vivo, liberating enzymatically active GrB without the need of subsequent in vitro processing. Similar results were obtained upon expression of a recombinant fragment of the ErbB2/HER2 receptor protein or GST as MBP fusions.

CONCLUSIONS

Our results demonstrate that combination of MBP as a solubility enhancer with specific in vivo cleavage augments secretion of processed and functionally active proteins from yeast. This strategy may be generally applicable to improve folding and increase yields of recombinant proteins.

Anti-CD3 scFv-B7.1 fusion protein expressed on the surface of HeLa cells provokes potent T-lymphocyte activation and cytotoxicityThis paper is one of a selection of papers in this Special Issue, entitled International Symposium on Recent Advances in Molecular, Clinical, and Social Medicine, and has undergone the Journal's usual peer-review process

The targeting of tumor cells by cytotoxic T lymphocytes is a promising strategy for biotherapy, but T cells require 2 signals via the T-cell receptor – CD3 complex and CD28 molecules for activation. To bridge the gap between cytotoxic T lymphocytes and tumor cells, our objective in this study was to describe the construction and the cell surface-anchored expression of a fusion protein, anti-CD3 scFv-B7.1, derived from inserting a fusion gene encoding anti-CD3 scFv and the extra-cellular domain of B7.1 fused by the splicing by overlap extension method into a mammalian expression vector, pDisplay. Transfection of the recombinant vector by electroporation into HeLa cells resulted in the production of protein migrating at approximately 57 kDa under reducing conditions. The expressed fusion protein could bind to T lymphocytes and induce strong T-cell activation. Meanwhile, a potent cytotoxicity was induced in the mixed culture of T-cell-modified tumor cells in a 96 h methyl-thiazolyl-diphenyl tetrazolium bromide assay. Our results indicate that this bifunctional protein, through activating T lymphocytes to lyse homologous human carcinomas, may be of potential value for T-cell-based immunotherapeutical treatment protocols in vivo.

Cancer Imaging and Therapy with Bispecific Antibody Pretargeting

This article reviews recent preclinical and clinical advances in the use of pretargeting methods for the radioimmunodetection and radioimmunotherapy of cancer. Whereas directly-labeled antibodies, fragments, and subfragments (minibodies and other constructs) have shown promise in both imaging and therapy applications over the past 25 years, their clinical adoption has not fulfilled the original expectations due to either poor image resolution and contrast in scanning or insufficient radiation doses delivered selectively to tumors for therapy. Pretargeting involves the separation of the localization of tumor with an anticancer antibody from the subsequent delivery of the imaging or therapeutic radionuclide. This has shown improvements in both imaging and therapy by overcoming the limitations of conventional, or 1-step, radioimmunodetection or radioimmunotherapy. We focus herein on the use of bispecific antibodies followed by radiolabeled peptide haptens as a new modality of selective delivery of radionuclides for the imaging and therapy of cancer. Our particular emphasis in pretargeting is the use of bispecific trimeric (3 Fab's) recombinant constructs made by a modular method of antibody and protein engineering of fusion molecules called Dock and Lock (DNL).

Breast carcinoma specific antibody selection combining phage display and immunomagnetic cell sorting

To discover new specific antibodies directed against disseminated carcinoma cells in breast cancer patients, a strategy combining single-chain variable fragment (scFv) phage display and immunomagnetic cell sorting was developed. A selection model, in which ErbB2-expressing breast carcinoma SKBR3 cells are spiked into a 50-fold excess of lymphocytes, was setup. Selection conditions, optimized using the previously characterized ErbB2-specific F5 phage scFv, led to an outstanding phage enrichment yield of 25,000 after only one round. This protocol applied to human nai ve and synthetic phage display antibody libraries led to the selection, in only two rounds, of individual scFv clones (43 out of 46 tested) specific for non-epithelial carcinoma antigens expressed on SKBR3 cells. This strategy is fully applicable to metastatic cells in effusions from breast carcinoma patients and shall lead to the discovery of immunotools crucial for novel diagnostic and therapeutic approaches.

Engineered antibody fragments and the rise of single domains

With 18 monoclonal antibody (mAb) products currently on the market and more than 100 in clinical trials, it is clear that engineered antibodies have come of age as biopharmaceuticals. In fact, by 2008, engineered antibodies are predicted to account for >30% of all revenues in the biotechnology market. Smaller recombinant antibody fragments (for example, classic monovalent antibody fragments (Fab, scFv)) and engineered variants (diabodies, triabodies, minibodies and single-domain antibodies) are now emerging as credible alternatives. These fragments retain the targeting specificity of whole mAbs but can be produced more economically and possess other unique and superior properties for a range of diagnostic and therapeutic applications. Antibody fragments have been forged into multivalent and multi-specific reagents, linked to therapeutic payloads (such as radionuclides, toxins, enzymes, liposomes and viruses) and engineered for enhanced therapeutic efficacy. Recently, single antibody domains have been engineered and selected as targeting reagents against hitherto immunosilent cavities in enzymes, receptors and infectious agents. Single-domain antibodies are anticipated to significantly expand the repertoire of antibody-based reagents against the vast range of novel biomarkers being discovered through proteomics. As this review aims to show, there is tremendous potential for all antibody fragments either as robust diagnostic reagents (for example in biosensors), or as nonimmunogenic in vivo biopharmaceuticals with superior biodistribution and blood clearance properties.