Development of new strategies for the modulation of the immune response against gene therapy vectors

Resumen

Currently, several clinical trials addressing gene therapy for the treatment of inherited diseases are underway, with AAV being one of the most widely used gene therapy vector due to its safety and great therapeutic potential. However, one of the main limitations for its clinical use is the presence of neutralizing antibodies (NAbs) naturally acquired against AAV or after the administration of a recombinant AAV (rAAV). NAbs prevent binding of the vector to the target cell and thus transduction, greatly diminishing or abrogating the expression of the therapeutic gene. For this reason, the presence of NAbs against AAV is an exclusion criterion in AAV clinical trials. Our working hypothesis is that the AAV gene therapy field would benefit enormously from the development of strategies that eliminate or prevent the formation of anti AAV neutralising antibodies. In this thesis two main objectives were addressed: 1) the use of an immunoglobulin G degrading enzyme (Ides) to eliminate pre-existing NAbs against rAAV to obtain an efficient transduction, and 2) the use of rapamycin containing nanoparticles (SVP-Rapa) together with a therapeutic vector for the treatment of PFIC3 in order to prevent antibody formation and allow vector re-administration. The selected Ides, the immunoglobulin G degrading enzyme from S. pyogenes (IdeS), was found to be highly efficient at cleaving human IgG, less efficient against NHP IgG and inefficient against mouse IgG. In vivo, we observed differences in how IdeS affected liver transduction in the presence of NAbs depending on the AAV serotype. For AAVAnc80 and AAV3B, the best transduction levels were achieved when the vector was administered after IgG digestion products were cleared from circulation. Selection of the best IdeS dose and the timing for vector administration after IdeS injection is essential for optimal transduction. Moreover, production of NAbs was prevented when PFIC3 animals were co-administered with SVP-Rapa and VTX-803, which allowed the re-administration of the vector and thus the reversal of the disease.