98. Adeno-Associated Virus Serotype 8 as a Vector for HEPATIC Delivery of alpha-1 Anti-Trypsin (AAT)

Abstract

Recently, we have demonstrated that local (intraarticular) or systemic (intramuscular) administration of an AAV-ratTNFR:Fc vector, encoding the rat tumor necrosis factor-a receptor: immunoglobulin (IgG1) Fc fusion gene, to rats with experimental arthritis led to suppression of disease as reflected in decreased inflammatory cell infiltration, pannus formation, cartilage and bone destruction, and mRNA expression of joint proinflammatory cytokines. Last year we began to evaluate the serum expression levels, in rats, of TNFR:Fc fusion protein following either endotracheal, intramuscular or intravenous administration of AAV-ratTNFR:Fc vectors pseudotyped with capsids from AAV serotypes 1, 2 or 5. Intramuscular delivery proved to be the most efficient route of administration and resulted in very high and sustained serum levels of TNFR:Fc protein for over a year. AAV2/1 was 100- to 1000-fold more efficient than AAV2/5 and AAV2/2, while AAV2/5 was up to 5-fold more efficient than AAV2/2. All animals developed anti-capsid neutralizing antibodies. For AAV2/1, these neutralizing antibodies reduced but not eliminated transduction following repeat intramuscular administration. Following a single intravenous administration, AAV2/1 demonstrated an over a 100-fold enhanced expression compared with AAV2/5 and AAV2/2, and AAV2/5 was up to 10-fold more efficient than AAV2/2. All animals developed anti-capsid neutralizing antibodies. Biodistribution of AAV2/1 vector DNA to perfused organs as well as TNFR:Fc mRNA expression is currently being assessed and data will be presented. Following a single pulmonary delivery of AAV2/5, maximum expression was achieved at 6-weeks post-administration, then gradually declined but remained detectable over a period of more than 250 days. Anti-AAV type 5 capsid neutralizing antibodies were elicited but did not prevent transduction and renewed expression of circulating TNFR:Fc protein for additional 6 months following a second AAV2/5 administration. The serum levels of TNFR:Fc protein were below the limit of detection (< 2 ng/mL) over 9-weeks post-AAV2/2 administration to the lung, although anti-AAV2 neutralizing antibodies were clearly evident. These had no apparent impact on transduction following repeat administration with an AAV2/5 vector. After more than 400 days, AAV2/5-transduced lungs demonstrated 100-fold more TNFR:Fc mRNA than animals administered with AAV2/2. AAV2/1 administration to the lung resulted in secretion of low but detectable TNFR:Fc protein that was almost 10-fold less efficient than AAV2/5. AAV2/1-treated animals developed anti-AAV type 1 capsid neutralizing antibodies. Re-administration of AAV2/5 to AAV2/1-treated animals resulted in renewed high levels of circulating TNFR:Fc protein which declined over a period of 6 months. These results demonstrate the utility of AAV vectors of alternate serotypes for long-term systemic delivery of secreted soluble TNFR:Fc protein and highlight their potential to treat systemic TNF-alpha-mediated autoimmune diseases such as reumatoid arthritis and psoriasis.