Systemic and local immune response to intraocular AAV vector administration in non-human primates

The positive clinical outcomes in adeno-associated virus (AAV)-mediated retinal gene therapy have often been attributed to the low immunogenicity of AAVs along with the immune-privilege of the eye. However, several recent preclinical studies and clinical trials have shown potential for inflammatory responses to AAV mediated gene therapy. Our current understanding of the factors contributing to intraocular inflammation such as the existence of serum antibodies against AAVs prior to injection and their contribution to increases in antibody levels post-injection is incomplete. The parameters that regulate the generation of new antibodies in response to the AAV capsid or transgene post-injection after intraocular administration are also insufficiently described. In this study we carried out a retrospective analysis of the pre-existing serum antibodies in correlation with changes in antibody levels after intraocular injections of AAV in non-human primates (NHPs). We analyzed NHP serums for the presence of both Binding Antibodies (BABs), as well as a subset of these called Neutralizing Antibodies (NABs) that impede AAV transduction upon binding. We observed significantly higher pre-existing serum BABs against AAV8 compared to other serotypes. We observed a dose-dependent increase in both BABs and NABs in the serums collected post-injection, irrespective of the serotype or the mode of injection. Lastly, we were able to demonstrate a co-relation between the serum BAB levels with clinical grading of inflammation and levels of transgene expression. ### Competing Interest Statement DD is an inventor on a patent of adeno-associated virus virions with variant capsid and methods of use thereof with royalties paid to Adverum Biotechnologies (WO2012145601 A2), patent applications on noninvasive methods to target cone photoreceptors (EP17306429.6 and EP17306430.4) licensed to Gamut Tx (now SparingVision). DD is a founder of Gamut Tx (now SparingVision). The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.