1. ¹Molecular Immunology Unit, Hospital Universitario Puerta de Hierro, Madrid, Spain
2. ²Tissue Bioengineering Multidisciplinary Unit, Fundación Hospital de Alcorcón, Madrid, Spain
3. ³Department of Immunology and Oncology, Centro Nacional de Biotecnología, Madrid, Spain
4. ⁴Medical Research Council Laboratory of Molecular Biology, Cambridge, UK

Correspondence: Dr L Álvarez-Vallina, Servicio de Inmunología, Hospital Universitario Clínica Puerta de Hierro, San Martín de Porres 4, 28035 Madrid, Spain. E-mail: lalvarezv.hpth@salud.madrid.org

Received 3 June 2006; Revised 25 September 2006; Accepted 18 November 2006; Published online 12 January 2007.

Abstract

Infiltrating T lymphocytes are found in many malignancies, but they appear to be mostly anergic and do not attack the tumor, presumably because of defective T-cell activation events. Recently, we described a strategy for the tumor-specific polyclonal activation of tumor-resident T lymphocytes based on the in situ production of recombinant bispecific antibodies (bsAbs) by transfected nonhematological cell lines. Here, we have constructed a novel HIV-1-based lentiviral vector for efficient gene transduction into various human hematopoietic cell types. Several myelomonocytic and lymphocytic cell lines secreted the anti-carcinoembryonic antigen (CEA) anti-CD3 diabody in a functionally active form with CD3⁺ T-cell lines being the most efficient secretors. Furthermore, primary human peripheral blood lymphocytes (PBLs) were also efficiently transduced and secreted high levels of functional diabody. Importantly gene-modified PBLs significantly reduced in vivo tumor growth rates in xenograft studies. These results demonstrate, for the first time, the utility of lentiviral vectors for sustained expression of recombinant bsAbs in human T lymphocytes. Such T lymphocytes, transduced ex vivo to secrete the activating diabody in autocrine fashion, may provide a promising route for a gene therapy strategy for solid human tumors.