High efficient mammalian expression and secretion of a functional humanized single-chain Fv/human interleukin-2 molecules

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.

Antitumor efficacy of the scFv-based fusion protein and its enediyne-energized analogue directed against epidermal growth factor receptor

Epidermal growth factor receptor (EGFR), overexpressed in many epithelial tumors, plays important roles in the formation and the development of tumors, and thus it is regarded as a promising target for cancer therapy. Single-chain variable fragment (scFv), an engineered antibody fragment, is generally used for constructing antibody-targeted drugs, owing to its low immunogenicity and high penetration capability into solid tumors. A fusion protein ER(Fv-LDP), consisting of an anti-EGFR scFv and the apoprotein (LDP) of lidamycin (LDM), was prepared and then assembled with the active chomophore [active enediyne (AE)] of LDM to generate enediyne-energized analogue ER(Fv-LDP-AE). The fusion protein ER(Fv-LDP) bound specifically to EGFR-overexpressing cancer cells and internalized into the cytoplasm through receptor-mediated endocytosis. ER(Fv-LDP) possessed cytotoxicity against carcinoma cell lines, which was hundreds of times more potent than the separate moiety of ER(Fv) and LDP. The enediyne-energized fusion protein ER(Fv-LDP-AE) also showed stronger cytotoxicity to target-relevant cancer cells than LDM in vitro. In human epidermoid carcinoma A431 xenografts, ER(Fv-LDP) presented higher antitumor efficacy than that of ER(Fv), LDP, and their mixture, with tumor growth inhibition rates of 63.6, 46.7, 48.5, and 49.9%, respectively. The enediyne-energized fusion protein ER(Fv-LDP-AE) at a dose of 0.4 mg/kg inhibited tumor growth by 89.2%, while no significant body weight loss was seen in treated animals. The results show that an anti-EGFR scFv-based fusion protein and its enediyne-energized analogue can be prepared by DNA recombination and molecular reconstitution. Both ER(Fv-LDP) and ER(Fv-LDP-AE) are effective against EGFR-overexpressing cancer xenograft in athymic mice. An integrated technical platform for scFv-based enediyne-energized fusion proteins has been established.

A dual-purpose protein ligand for effective therapy and sensitive diagnosis of anthrax

This article reports the design of a bivalent protein ligand with dual use in therapy and diagnosis of anthrax caused by Bacillus anthracis. The ligand specifically binds to PA and thereby blocks the intracellular delivery of LF and EF toxins that, respectively, cause cell lysis and edema. The ligand is a chimeric scaffold with two PA-binding domains (called VWA) linked to an IgG-Fc frame. Molecular modeling and binding measurements reveal that the VWA-Fc dimer binds to PA with high affinity (K(D)=0.2 nM). An in vitro bio-luminescence assay shows that VWA-Fc (at nanomolar concentration) protects mouse macrophages from lysis by PA/LF. In vivo studies demonstrate that VWA-Fc at low doses (approximately 50 microg/animal) are able to rescue animals from lethal doses of PA/LF and B. anthracis spores. Finally, VWA-Fc is utilized as the capture molecule in the sensitive (down to 30 picomolar) detection of PA using surface plasmon resonance.