A large number of blinding disorders caused by monogenic mutations lead to neuroretinal degeneration with no treatment currently available. Gene therapy carries the potential to counteract this degeneration and Adeno-associated virus (AAV) has become a widely used vector system for gene transfer in the eye. However, independent AAV gene therapy trials reported cases with ocular inflammation and loss of efficacy after initial functional improvements. One explanation for the decline of efficacy might be a host immune response directed against AAV and/or transduced cells. Our own data demonstrate that clinical grade AAV can indeed activate the pathogen-associated pattern recognition (PPR) system in the primate retina and consequently induce an immune response.

So far little is known about the interaction between recombinant AAV and PPRs in retinal cells. PPRs and downstream effector cytokines help to stage a concerted immune response. Therfore, this project aims to increase the safety and efficacy of AAV-mediated gene transfer by identifying the key pathways leading to the ocular immune response against AAV and finding ways to modulate those to limit inflammation and ensure long-term therapeutic transgene expression. 

Specifically, we use a unique collection of samples from current non-human primate and clinical trials to characterize the adaptive (humoral/cellular) immune response following ocular gene therapy with clinical grade AAV by ELISA, PBMC sub-population analysis (FACS), histology, immunohistochemistry and expression analysis. This will provide an overview of incidence and severity of ocular inflammation and immune response (aim1). Molecular and cell-biological techniques will be used to identify the relevant key PPR systems and associated pathways both in above samples and in appropriate in vitro models (aim2). Once key pathways are identified, strategies to prevent/block an immune response following AAV exposure are tested in a pilot study in vitro with the aim to enhance the safety and long term efficacy of AAV gene therapy (aim3).