Upregulation of CD8⁺ regulatory T cells following liver-directed AAV gene therapy

Liver-directed AAV gene therapy represents a unique treatment modality for a host of diseases. This is due, in part, to the induction of tolerance to transgene products. Despite the plethora of recognized regulatory cells in the body, there is currently a lack of literature supporting the induction of non-CD4⁺ regulatory cells following hepatic AAV gene transfer. In this work, we show that CD8⁺ regulatory T cells are up-regulated in PBMCs of mice following capsid only and therapeutic transgene AAV administration. Further, we demonstrate that hepatic AAV gene transfer results in a significant increase in CD8⁺ regulatory T cells following experimental autoimmune encephalomyelitis induction. Notably, this response occurred only in therapeutic vector treated animals, not capsid only controls. Understanding the role these cells play in treatment efficacy will result in the development of improved AAV vectors that take advantage of the full gamut of regulatory cells within the body.