Role of the atypical antigen presenting Müller cell during retinal gene therapy

• Applicant: Dr. Adrian Schmalen
• Subject Area: Ophthalmology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 525798505

Inherited retinal dystrophies comprise a heterogeneous set of retinal diseases that are associated with dysfunction and loss of photoreceptors. Thereby, loss of photoreceptor often is accompanied by chronic inflammation, secretion of various cytokines, and enhanced antigen presentation. Gene therapy approaches based on adeno-associated virus vectors hold promise to treat these eye diseases long-term. However, immune response against the viral particles and their transgene, administered to a retina showing already sings of persistent inflammation, is a major concern for safety and efficacy of expensive gene therapies. Rising evidence indicate that Müller cells fulfill all criteria of antigen presenting cells. Thus, they might form a second resident immune cell in the retina besides microglial cells, and must be considered for the success of gene therapy. Therefore, we will provide an in-depth characterization of the antigenic capacity of Müller cells in general and following AAV administration. Our immunopeptidomics analysis will highlight the immunologic phenotype of transduced Müller cells and their potential to stimulate CD4 or CD8 positive T cells. Additionally, we will identify immunodominant AAV-derived epitopes presented by Müller cells, that hold promise to adapt novel AAV capsids in order to reduce immunogenicity. Furthermore, Müller cells communicate with their cellular environment by releasing a plethora of cytokines. Amongst them are pro-inflammatory cytokines like IFNy, TNFa and CXCL10 induced upon stimulation with different other cytokines. Since Müller cells also express various Toll-like receptors, transduction of Müller cells might also induce release of pro-inflammatory signaling and result in retinal inflammation. Therefore, we will characterize release of these cytokines following transduction of Müller cells using an AAV-vector. Finally, we will establish a human retinal organoid model system that allows quantifying the AAV vector derived antigen presentation in a fast and reliable manor. This will allow us to test various conditions in order to reduce the immunogenicity of AAV vector preparations, while enhancing the transduction efficiency.

• DFG Programme: Research Grants