SUSTAINED SECRETION OF HUMAN ALPHA-1-ANTITRYPSIN FROM MURINE MUSCLE TRANSDUCED WITH ADENOASSOCIATED VIRUS VECTORS

Recombinant adeno-associated virus (AAV) vectors have been used to tra nsduce murine skeletal muscle as a platform for secretion of therapeut ic proteins. The utility of this approach for treating alpha-1-antitry psin (AAT) deficiency was tested in murine myocytes in vitro and in vi vo. AAV vectors expressing the human AAT gene from either the cytomega lovirus (CMV) promoter (AAV-C-AT) or the human elongation factor 1-alp ha promoter (AAV-E-AT) were examined. in vitro in C2C12 murine myoblas ts, the expression levels in transient transfections mere similar betw een the two vectors. One month after transduction, however, the human elongation factor 1 promoter mediated 10-fold higher stable human AAT expression than the CMV promoter. In vivo transduction was performed b y injecting doses of up to 1.4 x 10(13) particles into skeletal muscle s of several mouse strains (C57BL/6, BALB/c, and SCID). In vivo, the C MV vector mediated higher levels of expression, with sustained serum l evels over 800 mu g/ml in SCID and over 400 mu g/ml in C57BL/6 mice. T hese serum concentrations are 100,000-fold higher than those previousl y observed with AAV vectors in muscle and are at levels which would be therapeutic if achieved in humans. High level expression was delayed for several weeks but was sustained for over 15 wk Immune responses we re dependent upon the mouse strain and the vector dosage. These data s uggest that recombinant AAV vector transduction of skeletal muscle cou ld provide a means for replacing AAT or other essential serum proteins but that immune responses may be elicited under certain conditions.