Experimental treatment of SIV-infected macaques via autograft of CCR5-disrupted hematopoietic stem and progenitor cells

Abstract Hematopoietic stem cell-based gene therapy targeting CCR5 represents a promising way to cure HIV-1 infection. Yet the preclinical animal model with transplantation of autologous CCR5-ablated HSCs remains to be optimized. In this study, four Chinese rhesus macaques of SIV chronic infection were given long-term ART, during which peripheral CD34+HSPCs were purified and infected with CCR5-specific CRISPR/Cas9 lentivirus (three monkeys) or GFP lentivirus (one monkey). After non-myeloablative conditioning, the CCR5-modified or GFP-labeled HSPCs were autotransplanted to four recipients and ART was withdrawn following engraftment. All the recipients survived the process of transplantation. The purified CD34+HSPCs harbored undetectable level of integrated SIV DNA. The efficiency of CCR5 disruption in HSPCs ranges from 6.5% to 15.6%. Starting ART three months after SIV infection could license the hematopoietic reconstruction and maintain the physiological homeostasis. Despite the low-level editing of CCR5 in vivo (0.3-1%), the CCR5-disrupted cells in peripheral CD4+TEM subsets were enriched 2 to 3 fold after cessation of ART. Moreover, two of the three treated monkeys displayed a delayed viral rebound and a moderately recovered immune function six months after ART withdrawal. This study highlights the importance of improving the CCR5-editing efficacy and augmenting the virus-specific immunity for effective treatment of HIV-1 infection.