title: Immune responses against tetracycline-dependent transactivators affect long-term expression of mouse erythropoietin delivered by a helper-dependent adenoviral vector.
abstract: BACKGROUND
  Helper-dependent adenoviral (HD-Ad) vectors give rise to sustained gene expression after delivery in a variety of organisms. In particular, we previously documented persistent expression of erythropoietin (EPO) in mice after a single intramuscular (i.m.) injection of a HD-Ad vector harboring the mouse EPO cDNA.
  
  
  METHODS
  We use the same vector harboring the tetracycline (tet)-dependent transactivator (rtTA2S-M2) and silencer (tTS) and mouse EPO cDNA to analyze the capacity of the dual tet-dependent transactivator system to control long-term EPO gene expression and to study the effect of an eventual immune response against these artificial proteins after i.m. delivery in immuno-competent mice.
  
  
  RESULTS
  In the present study we demonstrate that i.m. injection of this vector in immuno-competent mice generates a cellular immune response to the rtTA2S-M2 transcription factor. This response curtails the duration of mouse EPO expression in mice, presumably by destroying the cells that co-express transcription factors and the therapeutic gene. Nonetheless, regulation of mouse EPO secretion was maintained during the entire experimental period, both when the vector dosage was reduced and when the tet-dependent transcription factors were put under the control of a muscle-specific promoter.
  
  
  CONCLUSIONS
  Delivery of the tet transactivators using as vehicle a HD-Ad vector induced an immune response directed against the transactivators themselves, causing short-term therapeutic transgene expression. Regulated, long-term therapeutic transgene expression was, however, obtained by reducing the vector dose or expressing the transactivators under the control of a muscle-specific promoter.
authors.affiliation: I.R.B.M. P. Angeletti, Via Pontina km 30 600, 00040 Pomezia, Italy.
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Lena
authors.forename: Patrizia
authors.initials: P
authors.lastname: Giannetti
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Sporeno
authors.forename: Gennaro
authors.initials: G
authors.lastname: Ciliberto
authors.forename: Rocco
authors.initials: R
authors.lastname: Savino
mesh_terms: D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D018274:Electroporation; D004921:Erythropoietin / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000276:immunology; D005822:Genetic Vectors / Q000235:genetics; D006378:Helper Viruses / Q000502:physiology*; D007111:Immunity, Cellular / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018482:Muscle, Skeletal / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D013752:Tetracycline / Q000494:pharmacology*; D013997:Time Factors; D015534:Trans-Activators / Q000235:genetics / Q000276:immunology* / Q000378:metabolism*; D019076:Transgenes / Q000235:genetics
chemical_list: D015534:Trans-Activators; D004921:Erythropoietin; D013752:Tetracycline