title: Early STAT1 activation after systemic delivery of HSV amplicon vectors suppresses transcription of the vector-encoded transgene.
abstract: The herpes simplex virus (HSV) amplicon vector is a powerful gene delivery vehicle that can accommodate up to 150 kilobase of exogenous DNA. However, amplicon-mediated transgene expression is often transient outside the nervous system. In order to define the role of host immune responses in silencing amplicon-encoded transgenes, we evaluated the kinetics of cytokine-/chemokine-expression after tail-vein injection of a luciferase-encoding amplicon into mice. Type I interferons (IFNs) were induced earliest, within an hour after injection, and several other cytokines/chemokines were subsequently upregulated in the livers of wild-type (WT) mice. When the same experiment was performed in signal transducers and activators of transcription 1 (STAT1)-knockout (KO) mice, the levels of type I IFN expression were significantly lower and chemokine induction was almost non-existent. Importantly, STAT1-KO mice exhibited significantly higher and more sustained luciferase activity than did the WT mice, which is attributable to increased transcriptional activity rather than increased copy numbers of luciferase-encoding vector DNA. Further studies using primary cultured fibroblasts derived from WT and STAT1-KO mice revealed the significance of STAT1 signaling in transcriptional silencing of the amplicon-encoded transgene in vitro. Our results indicate that type I IFNs induced by systemic delivery of HSV amplicon vectors initiate a cascade of immune responses and suppress transgene expression at the transcriptional level by activation of STAT1.
authors.affiliation: Dardinger Laboratory for Neuro-oncology and Neurosciences, Department of Neurological Surgery and Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Masataka
authors.initials: M
authors.lastname: Suzuki
authors.forename: E Antonio
authors.initials: EA
authors.lastname: Chiocca
authors.forename: Yoshinaga
authors.initials: Y
authors.lastname: Saeki
mesh_terms: D000818:Animals; D039481:CD11b Antigen / Q000378:metabolism; D002522:Chlorocebus aethiops; D002843:Chromatin / Q000235:genetics; D016207:Cytokines / Q000096:biosynthesis; D004279:DNA, Viral / Q000235:genetics; D005347:Fibroblasts; D015870:Gene Expression; D005822:Genetic Vectors / Q000235:genetics*; D008099:Liver / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D050794:STAT1 Transcription Factor / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D018139:Simplexvirus / Q000235:genetics*; D013997:Time Factors; D014158:Transcription, Genetic / Q000235:genetics*; D019076:Transgenes / Q000235:genetics*; D014709:Vero Cells
chemical_list: D039481:CD11b Antigen; D002843:Chromatin; D016207:Cytokines; D004279:DNA, Viral; D050794:STAT1 Transcription Factor