254 AAV In Vivo Gene Transfer Suppresses Adaptive Immune Responses Against α 1 Antitrypsin evaluate possible inflammatory and cytotoxic side effects caused by overexpression of transactivators We hav[.]
evaluate possible inflammatory and cytotoxic side effects caused by overexpression of transactivators We have previously developed a novel HC-Ad vector, HC-Ad-mTetON-~-Gal, encoding the tetracycline dependent transactivator (rtTA2 S-M2) and silencer (tTSk;d) under the control of a constitutive mCMV promoter We observed robust, inducible ~gal transgene expression in vitro and in vivo following administration of Doxycyline (Dox) Here, we characterized the effect of immune responses against the transactivator (constitutive expression) and the transgene (inducible expression) on HC-Ad-mTetON-~-Gal mediated expression after its delivery into the brain of C57BL/6 mice We immunized C57BLl6 mice with either pCI-TetON or pCI-~Gal plasm ids by intra-muscular injection HC-Ad-mTetON-~-Gal vector was injected three weeks later into the striatum (Ix 107 blue forming units) We administered Dox (in chow) for or weeks beginning twenty-four hours prior to intracranial HC-Ad injection We demonstrate that intra-muscular expression of the rtTA2S-M2 and Bgal using pCI-TetON and pCI~Gal plasmids induced a cellular immune response directed against the rtTA2 S-M2 transactivator and ~gal protein We observed higher numbers of IFN-ysecreting specific T cells by ELISPOT in the ~gal and TetON immunized animals (p