MyD88-dependent silencing of transgene expression during the innate and adaptive immune response to helper-dependent adenovirus

• Published in: Human gene therapy Vol. 21; no. 3; p. 325
• Main Authors: Suzuki, Masataka, Cerullo, Vincenzo, Bertin, Terry K, Cela, Racel, Clarke, Christian, Guenther, Margaretha, Brunetti-Pierri, Nicola, Lee, Brendan
• Format: Journal Article
• Language: English
• Published: United States 01.03.2010
• Subjects: Adaptive Immunity; Adenoviridae - genetics; Animals; Antigen-Presenting Cells - metabolism; Blotting, Western; Bone Marrow - immunology; Cells, Cultured; Chromatin Immunoprecipitation; Cytokines - metabolism; Enzyme-Linked Immunosorbent Assay; Fibroblasts - metabolism; Flow Cytometry; Gene Silencing - physiology; Genetic Vectors - therapeutic use; Helper Viruses - genetics; Immunity, Innate; Interferon-gamma - metabolism; Liver - immunology; Macrophages - immunology; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Myeloid Differentiation Factor 88 - genetics; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; RNA, Messenger - metabolism; Spleen - immunology; Th1 Cells - immunology; Toll-Like Receptor 2 - physiology; Transgenes - physiology
• ISSN: 1557-7422
• DOI: 10.1089/hum.2009.155

Activation of the host innate immune response after systemic administration of adenoviral vectors constitutes a principal impediment to successful clinical gene replacement therapies. Although helper-dependent adenoviruses (HDAds) lack all viral functional genes, systemic administration of a high dose of HDAd still elicits a potent innate immune response in host animals. Toll-like receptors (TLRs) are innate receptors that sense microbial products and trigger the maturation of antigen-presenting cells and cytokine production via MyD88-dependent signaling (except TLR3). Here we show that mice lacking MyD88 exhibit a dramatic reduction in proinflammatory cytokines after intravenous injection of a high dose of HDAd, and show significantly reduced induction of the adaptive immune response when compared with wild-type and TLR2-deficient mice. Importantly, MyD88(-/-) mice also show significantly higher and longer sustained transgene expression than do wild-type mice. Chromatin immunoprecipitation studies using wild-type and MyD88-deficient primary mouse embryonic fibroblasts showed significant MyD88-dependent transcriptional silencing of the HDAd-encoded transgenes. Our results demonstrate that MyD88 signaling, activated by systemic delivery of HDAd, initiates an innate immune response that suppresses transgene expression at the transcriptional level before initiation of the adaptive immune response.