Switching of serotype can improve local AAV-mediated gene therapy in RA

Objective

Adeno-associated virus (AAV) is a very promising vector for gene therapy in RA. Although an increasing number of AAV serotypes have been identified, all studies so far have been performed with serotype 2. The aim of this study was to compare the transduction efficiency of five different AAV serotypes (AAV1–AAV5) encoding reporter genes, the murine secreted alkaline phosphatase (mSEAP) or the E. coli β-galactosidase (beta-Gal), in two different animal models of arthritis.

Methods

AAV1–AAV5 containing the gene for beta-Gal were injected into the right ankle joints of rats with adjuvant arthritis (AA) on day 12 after adjuvant immunization. Joints were collected 2 weeks after injection. The number of viral genomic copies in the joint was determined by qPCR. For detection of LacZ transcription in joints and organs, RT-PCR was used. Beta-Gal expression was analyzed by direct in situ staining of frozen sections, quantified by digital image analysis. In mice with collagen-induced arthritis (CIA), AAV1, 2 and 5 constructs encoding the mSEAP gene were injected into the left knee joint 32 days following arthritis induction. Transgene expression was analyzed by chemiluminescence in sera and culture medium conditioned by the joint tissues at different time points.

Results

The greatest number of viral genomic copies was detected using AAV5. This was confirmed by in situ beta-Gal staining. RT-PCR proved the presence of LacZ mRNA in injected joints, but not in any of the organs tested. In the CIA mice model AAV5 also had the best transduction efficiency. Transgene expression was detectable in sera and patellae 1 week after joint injection, increased over time, and remained at plateau levels for at least 1 month.

Conclusion

In vivo gene transfer with AAV5 is far more efficient than with other serotypes. Local AAV-mediated gene therapy in RA could be improved by using AAV5.