483. Epigenetic Silencing of Hepatitis B cccDNA In Vitro and In Vivo Using AAV-Delivered Engineered Repressor Transcription Activator-Like Effector

Abstract

Gene editinG and Gene ReGulation iistimulation paralleled that of endogenous CD40L in unedited T-cells. Additionally, activated T-cells expressing edited CD40L were able to bind CD40-Ig similar to unedited cells. When T-cells from X-HIGM patients were edited in this fashion, CD40L expression and CD40-Ig binding was restored, and repaired activated X-HIGM T-cells induced the expression of early activation markers and class switching of naïve B-cells in vitro. Finally, we found no differences in TCR repertoire or engraftment and stability in NSG mice between T cells that underwent gene editing vs. unedited cells. These results demonstrate the feasibility of site-directed gene repair to restore normally regulated CD40L protein expression and functional T-cell help.

Gene Therapy for Chronic HBV—Can We Eliminate cccDNA?

“…The engineered sequence caused methylation of targeted CpG sites, downregulation of viral mRNAs and proteins, and a decrease in viral replication in cell culture and in HBV transgenic mice. Repressors based on the Krüppel associated box (KRAB) domain have also been investigated as ZF [ 80 ] and TALE [ 81 ] fusions. Although these KRAB-repressors inhibit viral replication, verification of heterochromatin formation, which is important to achieve permanent gene silencing, remains to be confirmed.…”