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Klaus G. Schmetterer,1
Alina Neunkirchner,1
Christian Sillaber,5
Brian Seed,6 and
Winfried F. Pickl1*
Institute of Immunology, Center for Physiology, Pathophysiology, and Immunology, Medical University of Vienna, A-1090 Vienna, Austria,1 Insitut Curie, Centre National de la Recherche Scientifique, UMR 144, Paris 75248, France,2 Institut Curie, Centre National de la Recherche Scientifique, Paris 75248, France,3 Institut National de la Santé et de la Recherche Médicale, INSERM U653, Institut Curie, Paris 75248, France,4 Division of Hematology and Hemostaseology, Department of Internal Medicine I, Medical University of Vienna, A-1180 Vienna, Austria,5 Center for Computational and Integrative Biology, Harvard Medical School, Boston, Massachusetts 021146
Received 30 March 2007/ Accepted 22 May 2007
Viral particles preferentially incorporate extra- and intracellular constituents of host cell lipid rafts, a phenomenon central to pseudotyping. Based on this mechanism, we have developed a system for the predictable decoration of enveloped viruses with functionally active cytokines that circumvents the need to modify viral proteins themselves. Human interleukin-2 (hIL-2), hIL-4, human granulocyte-macrophage colony-stimulating factor (hGM-CSF), and murine IL-2 (mIL-2) were used as model cytokines and fused at their C terminus to the glycosylphosphatidylinositol (GPI) acceptor sequence of human Fc
receptor III (CD16b). We show here that genetically modified cytokines are all well expressed on 293 producer cells. However, only molecules equipped with GPI anchors but not those linked to transmembrane/intracellular regions of type I membrane proteins are efficiently targeted to lipid rafts and consequently to virus-like particles (VLP) induced by Moloney murine leukemia virus Gag-Pol. hIL-4::GPI and hGM-CSF::GPI coexpressed on VLP were found to differentiate monocytes towards dendritic cells. Apart from myeloid-committed cell types, VLP-bound cytokines also act efficiently on lymphocytes. hIL-2::GPI strongly costimulated T-cell receptor (TCR)/CD3 dependent T-cell activation in vitro and mIL-2::GPI-coactivated antigen-specific T cells in vivo. On a molar basis, the functional activity of VLP-bound hIL-2::GPI was found to be comparable to that of soluble hIL-2. VLP decorated with hIL-2::GPI and coexpressing a TCR/CD3 ligand have an IL-2-specific activity of 5 x 104 units/mg protein. Virus particles decorated with lipid-modified cytokines might help to improve viral strains for vaccination purposes, the propagation of factor-dependent cell types, as well as gene transfer by viral systems in the future.
Published ahead of print on 30 May 2007.
Present address: Department of Systems Biology of Signal Transduction, Deutsches Krebsforschungszentrum Heidelberg, 69120 Heidelberg, Germany.
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