Effect of synovial fluid on adeno-associated virus mediated gene transfer to chondrocytes

Background

Direct intra-articular gene tranfer with adeno-associated virus (AAV) vectors is a promising strategy to allow efficient therapeutic transgene expression within the joint. However, over 90% of humans demonstrate antibodies against AAV which could alter AAV transduction efficiency in vivo.

Objective

Our objective was to determine the influence of synovial fluid (SF) and serum from arthritic patients on AAV-mediated gene transfer to chondrocytes in vitro.

Methods

SF and sera derived from 21 patients suffering from various (inflammatory or mechanical) origins were collected. Neutralizing activity against AAV/IL-4 was determined by assessing the ability of SF or serum to inhibit transduction of AAV/IL-4 into the C20A4 human chondrocyte cell line. Total IgGs were purified from SF by salt-dependent chromatography.

Results

In SF and sera, inhibition of AAV-mediated gene transfer to chondrocytes was observed in all arthritic patients. Purified IgG from SF exhibited inhibition patterns similar to those seen with unfraction-ated SF. A correlation was observed between levels of inhibition by the SF and the serum (P < 0.0001, r = 0.813). Lastly, we have shown that the inhibition of AAV/IL-4 infection on C20A4 cells by SF and sera could be reversed by increasing the number of AAV/IL-4 particles, with a dose-dependent effect.

Conclusion

SF and sera from all patients show a neutralizing activity against AAV infection on chondrocytes. Neutralizing factors were IgG antibodies present in the SF. This inhibition can be reversed by increasing AAV doses. In the future, these data might be useful to adapt intra-articular AAV gene therapy to each individual patient.