387. Transfer of Hyaluronic Acid Synthase-2 Gene into Canine Joints Using Adeno-Associated Viral Vectors

Abstract

Osteoarthritis (OA) is one of the more common causes of lameness in dogs and is estimated to affect approximately 20% of dogs >1 year old. OA is a progressive and degenerative disease that results in pain, inflammation and reduced joint mobility. Novel, safe and efficacious therapies that improve joint lubrication and reduce the extent of inflammation and pain are potential solutions for the management of canine OA. Here, we evaluated the efficiency of gene transfer to canine joint by intra-articular injections of recombinant adeno-associated virus (rAAV) vectors encoding therapeutic genes. Specifically, we generated rAAV vectors (either AAV2 and AAV5 serotypes vectors) encoding canine codon-optimized hyaluronic acid (HA) synthase-2 (HAS2) to provide local and continuous synthesis of HA in the joint. Twenty-two adult healthy dogs that were seronegative for anti-AAV2 and -AAV5 antibodies were injected intra-articularly with rAAV2/HAS2 (1, 5 and 10×1011 vg/joint), rAAV5/HAS2 (5×1011 vg/joint) or PBS (control). No adverse clinical signs were observed following the 28-day study period. Histopathological analysis showed minimal synovial inflammation in the joints of dogs treated with rAAV5/HAS2 and no significant changes in the rAAV2/HAS2 treated dogs. Vector genomes (VG) were detected in the synovium of all the rAAV-treated joints and in the majority of cartilage samples tested. The rAAV5/HAS2 vector resulted in findings of higher and more consistent detection of VG and transcripts compared to rAAV2/HAS2 in both the synovial and cartilage samples. Preliminary analysis also showed a trend towards increased HA levels in the synovial fluid of the treated joints. In summary, our study demonstrated that rAAV2 and rAAV5-mediated gene transfer to canine joint tissues is feasible and that both vectors present an acceptable safety profile following a single intra-articular injection.