Inflammation and Immune Response of Intra-Articular Serotype 2 Adeno-Associated Virus or Adenovirus Vectors in a Large Animal Model

Abstract

Intra-articular gene therapy has potential for the treatment of osteoarthritis and rheumatoid arthritis. To quantify in vitro relative gene transduction, equine chondrocytes and synovial cells were treated with adenovirus vectors (Ad), serotype 2 adeno-associated virus vectors (rAAV2), or self-complementary (sc) AAV2 vectors carrying green fluorescent protein (GFP). Using 6 horses, bilateral metacarpophalangeal joints were injected with Ad, rAAV2, or scAAV2 vectors carrying GFP genes to assess the in vivo joint inflammation and neutralizing antibody (NAb) titer in serum and joint fluid. In vitro, the greater transduction efficiency and sustained gene expression were achieved by scAAV2 compared to rAAV2 in equine chondrocytes and synovial cells. In vivo, AAV2 demonstrated less joint inflammation than Ad, but similar NAb titer. The scAAV2 vectors can induce superior gene transduction than rAAV2 in articular cells, and both rAAV2 and scAAV2 vectors were showed to be safer for intra-articular use than Ad vectors.

scAAVIL-1ra dosing trial in a large animal model and validation of long-term expression with repeat administration for osteoarthritis therapy

“…As confirmed in other intra-articular gene therapy studies, synovial cells within the synovial tissue and chondrocytes within the cartilage are the principle targeted cells for initial injection; however, synovial turnover results in most transduced cells within the synovium to be absent (due to turnover) between 4 and 6 weeks following injection leaving the chondrocytes as the stable, long-term protein producing cells. 24,34 Although initial gene therapy studies in laboratory animals suggested that cartilage is not successfully transduced, this and other work in the horse has shown long-term expression of AAV in this enduring population of quiescent and minimally dividing cell population 19,24,31 and therefore highlight the potential for human cartilage to also result in sustained levels of protein production given its similarities to the horse. 27,37 GFP expression persisting in chondrocytes rules out the possibility of immune response to GFP as a primary reason of loss of transgene expression in synoviocytes.…”

“…27,37 While the use of the horse for dosing studies is expensive, the translational value of performing this study should provide valuable data to the human arena to suggest appropriate dosing for similarly sized joints using scAAVIL-1ra. We based our escalating vector dosage on previous work by us 24 and others 21,31 who established therapeutic levels of various AAV transgenes in joints similar in size to the human knee. The horse has been used extensively as a translational model to humans for OA 37,38 and cartilage repair 39,40 and we believe this dosing study is suggestive of levels that can be expected in a similarly sized human knee.…”

“…As AAV gene delivery to joints continues to show promise in animals 24,31,52 and people, 21,55 questions have surfaced as to whether immunity to AAV vectors would result in an inability to re-dose patients with AAV vectors that had an inadequate rise of protein to therapeutic levels. The inability to utilize AAV gene therapy following previous exposure to AAV has been well-established.…”

scAAV-mediated gene transfer of interleukin-1-receptor antagonist to synovium and articular cartilage in large mammalian joints

“…A recent study by Ishihara et al, however, showed the capacity of intraarticular injection of AAV to stimulate a potent humoral immune response. 28 The capacity with which AAV specific antibodies in synovial fluid may neutralize a bolus of 10 12 -10 13 vector particles, or the ability to bypass this humoral immunity via methods, such as by fluid aspiration or joint lavage remains unknown. The equine joint however offers a useful system in which to explore these types of practical studies, which may be of significant clinical relevance.…”

Optimization of scAAVIL-1ra In Vitro and In Vivo to Deliver High Levels of Therapeutic Protein for Treatment of Osteoarthritis

“…Suitability of scAAV vectors intra-articularly was further confirmed in equine joints when transduction efficiency of AdGFP, rAAV, and scAAV were compared over a period of 8 weeks. 26 Goodrich et al compared scAAV serotypes in synoviocytes and chondrocytes in vitro and revealed the importance of serotype affinity in that significant differences existed in transduction efficiencies in both synoviocytes and chondrocytes which are the main cell types in joints. 27 Serotype 6 was better in chondrocytes and serotype 3 in synoviocytes whereas serotype 2 was best in both chondrocytes and synoviocytes.…”