181. Optimization of In Vivo Delivery of Baculovirus Gene Therapy Vectors for the Treatment of Alpha-1 Antitrypsin Deficiency

Abstract

Alpha-1 antitrypsin deficiency (AATD) is a single-gene disorder commonly associated with adult onset lung diseases, including emphysema, chronic obstructive pulmonary disease and airway inflammation. Alpha-1 antitrypsin (AAT) is produced primarily in hepatocytes and is subsequently secreted into the bloodstream and travels to the lung where it inhibits neutrophil elastase. Unregulated neutrophil elastase activity in individuals with AATD causes degradation of various components of the extracellular matrix producing damage to alveolar and airway epithelial cells. Furthermore, mutated AAT folds incorrectly causing intracellular aggregation within hepatocytes, which can result in liver damage in addition to pulmonary symptoms. The development of gene therapy strategies has been a popular approach for the treatment of AATD due to monogenic nature of this genetic disease. Recently, baculovirus based vectors have garnered attention for possible application in gene therapy due to multiple factors. Baculoviruses can tolerate large gene insertions (>38kb), are capable of transducing mammalian cells but not replicating or integrating into host chromosomes and finally, humans lack pre-existing immunity to these insect viruses. Although there are many characteristics that make baculovirus vectors attractive for use in gene therapy, there is little in vivo data on bio-distribution and tissue tropism in mammalian models. As AATD is a disease affecting both the liver and the lung, we examined several delivery routes of a baculovirus vector expressing the human placental alkaline phosphatase reporter gene in C57BL/6 mice. To target the lung we investigated intranasal and intratracheal administration and for liver delivery intravenous, intrahepatic and intraportal vein injections were utilized. Lung delivery of wild type baculovirus yielded little transduction, however intrahepatic injection resulted in moderate liver transduction as well as unexpected spread to other tissues. Different formulations of the baculovirus vector were examined for pulmonary delivery including a variety of viscoeleastic gels. Additionally, pharmacological agents such as clodronate liposomes to deplete macrophages and cobra venom factor to ablate complement activity were examined in an effort to bolster transduction.