Ex Vivo Gene Delivery to Synovium Using Foamy Viral Vectors

Background: Gene transfer technologies have the potential to fundamentally improve current therapies for arthritic conditions, although this is essentially dependent on safe and efficient vector systems. The foamy virus (FV)-based vectors have many safety features that favour their use in the treatment of arthritis. In the present study, we investigated the use of safe prototype foamy viral vectors (FVV) for indirect gene delivery to articular tissues.

Methods: We generated recombinant FVV encoding enhanced green fluorescent protein (EGFP) or human interleukin 1 receptor antagonist protein (IL1RA) cDNA under the control of the spleen focus forming virus U3 promoter and explored their transgene expression profile following ex vivo gene delivery to knee joints of Wistar and athymic nude rats.

Results: FVV efficiently transduced primary rat synovial fibroblasts using the EGFP and the IL1RA transgene in vitro. FVV-mediated IL1RA expression was functional in blocking IL1 effects in vitro. After the transplantation of FVV transduced synovial fibroblasts, the intra-articular transgene expression in Wistar rats was initially high and declined after approximately 3 weeks for both transgenes. By contrast, FVV-mediated expression of EGFP and IL1RA persisted for at least 12 weeks at high levels in immunocompromised nude rats. FVV-meditated gene delivery was well tolerated by all animals without extra-articular transgene expression, arguing for the safety of this approach.

Conclusions: Our results indicate that FVV are capable of efficient ex vivo gene transfer to synovium and merit further investigation as a means to provide long-term intra-articular transgene expression for arthritis treatment.