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Therapy of human non-small-cell lung carcinoma using antibody targeting of a modified superantigen
G Forsberg1, L Ohlsson, T Brodin
1Active Biotech Research AB, Box 724, 220 07 Lund, Sweden.
Abstract:
Superantigens activate T-cells by linking the T-cell receptor to MHC class II on antigen-presenting cells, and novel reactivity can be introduced by fusing the superantigen to a targeting molecule. Thus, an antibody-targeted superantigen, which activates T cells to destroy tumour cells, might be used as cancer therapy. A suitable target is the 5T4 oncofetal antigen, which is expressed on many carcinomas. We constructed a fusion protein from a Fab of a monoclonal antibody recognizing the 5T4 antigen, and an engineered superantigen. The recombinant product 5T4FabV13-SEA(D227A)bound the 5T4 antigen expressed on the human non-small-cell lung cancer cell line Calu-1 with a Kd of 1.2 nM while the substitution of Asp227 to Ala in the superantigen moiety reduced binding activity to MHC class II. 5T4FabV13-SEA(D227A)tumour reactivity was demonstrated in 7/7 NSCLC samples by immunohistochemistry, while normal tissue reactivity was low to moderate. 5T4FabV13-SEA(D227A)induced significant T-cell-dependent in vitro killing of sensitive 5T4 bearing Calu-1 cells, with maximum lysis at 10(-10)M, while the capacity to lyse MHC class II expressing cells was approximately 1000 times less effective. Immunotherapy of 5T4FabV13-SEA(D227A)against human NSCLC was investigated in SCID mice reconstituted with human peripheral blood mononuclear cells. Mice carrying intreperitoneally growing Calu-1 cells showed significant reduction in tumour mass and number after intravenous therapy with 5T4FabV13-SEA(D227A). Thus, 5T4FabV13-SEA(D227A)has highly attractive properties for therapy of human NSCLC.
Insights
This study developed a novel antibody-targeted superantigen, 5T4FabV13-SEA(D227A), to treat non-small cell lung cancer (NSCLC). The fusion protein effectively targets 5T4 antigen on cancer cells, activating T cells for tumor destruction with minimal off-target effects.
Area of Science:
- Oncology
- Immunology
- Biotechnology
Background:
- Superantigens activate T-cells by bridging T-cell receptors and MHC class II molecules.
- Antibody-targeted superantigens offer a novel approach for cancer immunotherapy by directing T-cell activation to tumor cells.
- The 5T4 oncofetal antigen is a promising target due to its expression on various carcinomas, including non-small cell lung cancer (NSCLC).
Purpose of the Study:
- To engineer and evaluate a fusion protein, 5T4FabV13-SEA(D227A), for targeted cancer immunotherapy.
- To assess the binding affinity, tumor reactivity, and T-cell-mediated cytotoxicity of the engineered fusion protein.
- To investigate the in vivo efficacy of 5T4FabV13-SEA(D227A) in a human NSCLC mouse model.
Main Methods:
- Construction of a fusion protein combining a 5T4-specific antibody fragment (Fab) with an engineered superantigen (SEA(D227A)).
- Characterization of binding affinity to 5T4 antigen and reduced binding to MHC class II.
- Immunohistochemical analysis of tumor and normal tissue reactivity.
- In vitro assessment of T-cell-dependent tumor cell killing.
- In vivo efficacy study in SCID mice bearing human NSCLC xenografts.
Main Results:
- The fusion protein 5T4FabV13-SEA(D227A) demonstrated high affinity binding (Kd of 1.2 nM) to the 5T4 antigen on Calu-1 NSCLC cells.
- The engineered superantigen moiety showed reduced binding to MHC class II, minimizing off-target T-cell activation.
- Significant T-cell-mediated lysis of 5T4-positive NSCLC cells was observed in vitro.
- Immunohistochemistry confirmed 5T4FabV13-SEA(D227A) reactivity in 7/7 NSCLC samples with low to moderate normal tissue reactivity.
- Intravenous therapy with 5T4FabV13-SEA(D227A) resulted in a significant reduction in tumor mass and number in a human NSCLC SCID mouse model.
Conclusions:
- 5T4FabV13-SEA(D227A) is a potent antibody-targeted superantigen with specific activity against 5T4-expressing NSCLC.
- The fusion protein effectively mediates T-cell-dependent tumor cell killing and demonstrates in vivo anti-tumor efficacy.
- 5T4FabV13-SEA(D227A) shows significant promise as a novel immunotherapy for human NSCLC.