Selective uptake and sustained expression of AAV vectors following subcutaneous delivery

Background Recombinant adeno-associated viral (rAAV) vectors are capable of long-term expression of secreted and intracellular proteins following deli very to muscle, liver, and the central nervous system. In this study, we ha ve evaluated subcutaneous injection of rAAV encoding a variety of transgene s as an alternative route of administration for the systemic delivery of th erapeutic proteins. Methods rAAV vectors encoding the human factor TX, human interferon-alpha 2 a, murine erythropoietin (epo), and Escherichia coli lacZ genes were used f or subcutaneous delivery into mature immunocompetent mice. Expression of fa ctor TX and interferon in mouse serum was measured by ELISA. Expression of Epo was monitored by an increase in hemotocrit and by RIA. The tissue tropi sm of AAV transduction was determined by histochemistry following administr ation of the lacZ vector. Results Long-term protein expression (at least one year) is demonstrated in the serum of immunocompetent mice following subcutaneous delivery of AAV v ectors encoding the human factor IX and interferon genes. The murine epo ge ne delivered via this route resulted in levels of Epo that correlate with i ncreased hematocrits of up to 90% for a duration of nine months, rAAV encod ing the lacZ gene revealed that the panniculus carnosus, a skeletal muscle layer of the skin, was transduced upon subcutaneous administration. Conclusions This study shows that long-term expression of secreted proteins can be achieved using rAAV vectors injected subcutaneously as a single adm inistration. The observation that the panniculus carnosus is the primary ti ssue transduced by rAAV illustrates the high tropism of rAAV for skeletal m uscle. Copyright (C) 1999 John Wiley & Sons Ltd.