Contrary to expectations, lentiviral vector (LV) initiated an immune response via “pseudotransduction” - the direct delivery of antigen packaged in the virus - rather than by the intended expression of antigen-encoding DNA. LVs induced dendritic cell activation via two pathways: viral-mediated membrane fusion induced a P13K-dependent pathway, while pseudotransduced human genomic DNA activated a STING- and cGAS-dependent pathway.
Dendritic cell (DC) activation and antigen presentation are critical for efficient priming of T cell responses. Here, we study how lentiviral vectors (LVs) deliver antigen and activate DCs to generate T cell immunization in vivo. We report that antigenic proteins delivered in vector particles via pseudotransduction were sufficient to stimulate an antigen-specific immune response. The delivery of the viral genome encoding the antigen increased the magnitude of this response in vivo but was irrelevant in vitro. Activation of DCs by LVs was independent of MyD88, TRIF, and MAVS, ruling out an involvement of Toll-like receptor or RIG-I-like receptor signaling. Cellular DNA packaged in LV preparations induced DC activation by the host STING (stimulator of interferon genes) and cGAS (cyclic guanosine monophosphate-adenosine monophosphate synthase) pathway. Envelope-mediated viral fusion also activated DCs in a phosphoinositide 3-kinase-dependent but STING-independent process. Pseudotransduction, transduction, viral fusion, and delivery of cellular DNA collaborate to make the DC-targeted LV preparation an effective immunogen.
Author Info: (1) Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA. Division of Infectious Diseases, Department of Medicine at Universi
Author Info: (1) Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA. Division of Infectious Diseases, Department of Medicine at University of California, Los Angeles, Los Angeles, CA 90095, USA. (2) Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089, USA. (3) Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA. Division of Dermatology, Department of Medicine, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095, USA. (4) Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA. (5) Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089, USA. (6) Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA. (7) Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA. (8) Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA 90089, USA. (9) Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA. Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA. (10) Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA. baltimo@caltech.edu.
