Liver cells transduced with AAV.MOG increase the frequency of MOG-specific T regulatory cells capable of reducing EAE by adoptive transfer

Abstract Multiple Sclerosis is a demyelinating autoimmune disease brought on by self-reactive, myelin-specific T effector cells. Immunosuppressants are the most utilized tool to combat disease progression; however, they bring unwanted side effects. We have previously published on a novel gene immunotherapy that uses an adeno-associated virus (AAV) containing the full sequence of the myelin oligodendrocyte glycoprotein (MOG) that restores tolerance through liver-directed gene therapy, resulting in the generation of antigen-specific T regulatory cells (Tregs) that can ameliorate Experimental Autoimmune Encephalomyelitis (EAE). While the data is promising, the mechanism of this therapy remains enigmatic. To begin defining the mechanism initially, we cultured MOG-specific CD4 +T cells from 2D2 mice with liver cells from B6 mice that received either AAV.MOG or a saline control. We found a significant increase in the frequency of CD4 +CD25 +FoxP3 +Tregs when 2D2 T cells were cultured with liver cells from AAV.MOG-vectored mice in a 1:2 ratio compared to the control. Next, we injected 2D2 mice with AAV.MOG and isolated CD4 +CD25 +T cells 2 weeks later. To evaluate their suppressive ability they, or control cells, were adoptively transferred to recipient naïve B6 mice. After 24 hours, active EAE was induced. By day 15, disease severity in mice that received AAV.MOG donor 2D2 T cells was significantly reduced compared to the controls (CD4 +CD25 +T cells from wildtype B6 mice given either AAV.MOG or AAV.AQP4) Overall, these results demonstrated that livers transduced with AAV.MOG can induce 2D2 Tregs in vitro and that CD4 +CD25 +T cells from vectored 2D2 mice reduce EAE severity. Supported by a grant from the NIH (R01AI128074) and the Children's Miracle Network