NoSMod · Novel Strategies for the Modulation of Immunity to AAV vectors

Novel Strategies for the Modulation of Immunity to AAV vectors

Immune responses directed against adeno-associated virus (AAV) vectors represent an important obstacle to the safety and efficacy of in vivo gene transfer. The overarching goal of the Career Integration Grant “NosMod” was to gain a better understanding on the interactions between the host immune system and AAV vectors to develop targeted intervention to modulate capsid immunogenicity. The resources provided by the grant were instrumental to achieve the research objectives, establish techniques and a line of research focused on immunology of gene therapy, and secure significant funding such as an ERC consolidator grant and other European Community grants. Several articles were accepted for publication and the support from NosMod was acknowledged. Additional articles are in submission. The applicant also secured a permanent position with the INSERM, the French national institute for biomedical research, further consolidating his presence in Europe. NosMod focused on three main aims centered around immunity to AAV. The first aim was based on in vitro studies in human peripheral blood mononuclear cells (PBMCs) collected in the context of AAV gene therapy trial or normal donors. Work from this aim allowed to 1) define the complexity of immune responses to AAV in healthy donors and identify reactivity to the AAV capsid in known T cell compartments (e.g. effector memory CD8+ T cells) and in others not previously described; 2) identify some of the markers of early activation of the immune system and translate the finding into a possible immunomodulatory strategy; 3) tracked the fate of T cells in the bloodstream and in AAV-injected tissue, showing that some of T cell cloned induced by the exposure to AAV vectors do not necessarily circulate in PBMCs. Additional ongoing work involves immunomonitoring in subjects undergoing AAV gene transfer. This work provides access to key samples for additional studies focused on the adaptive immune responses to AAV vectors. The second aim of NosMod focused on the identification of safe and effective immunomodulatory regimens to tackle the issue of anti-AAV antibodies. Like in the first aim of the NosMod grant, here we focused on human donors and we screened samples from subjects receiving immunosuppressive drugs. We did identify some regiments with some effect of pre-existing neutralizing antibodies to AAV. Additionally, while preforming this work we establish novel, highly sensitive assay to measure anti-capsid antibodies and we also carefully dissected the different role of neutralizing and non-neutralizing antibodies on AAV transduction in vitro and in vivo. Work from this second aim was instrumental to the third aim of the NosMod grant in which we tested several immunomodulatory regimens in vivo in small and large animal models of gene transfer. We tested regimens identified in the first and second aim of NosMod and also extensively tested a new technology based on the formulation of rapamycin in nanoparticles. This technology was safe and highly effective in blocking anti-AAV antibodies in mice and non-human primates, allowing for vector readministration. Importantly, this work is currently being translated to humans in the context of gene therapy trials. As a fallback strategy to overcome the issue of neutralizing antibodies to AAV, we published data on the use of exosome enveloped AAV vectors, which seem to be more resistant to antibody-mediated neutralization than conventional AAV. We also collaborated on the development of novel AAV capsid engineered to be less prone to antibody mediated neutralization. Thus, the scientific program described in NosMod was successfully conducted and results obtained had an important impact on the field of gene therapy with AAV vectors. Several publications originated from this work in journals like Blood Advances, Molecular Therapy, Molecular Therapy Methods and Clinical Development, etc. The work was also presented at several national and international conferences. Several teaching activities were also part of the work conducted and associated with NosMod. Thanks to the help of NosMod the laboratory was established and funding was obtained, mostly awarded by the European Community (FP7 and H2020 actions).

Data: CORDIS, © European Union