Hematopoietic stem cell (HSC) transplantation has become a standard of care for the treatment of otherwise incurable blood cancers and genetic diseases. The cure of HIV by transplanting CCR5-mutant (CCR5-delta32) HSCs demonstrated the feasibility and power of stem cell-based therapies for eliminating latent virus and controlling AIDS. However, it will be critical to define the spectrum of anti-viral protection, the engraftment threshold of CCR5-mutant HSCs required for protection, and the potential for depletion of the virus reservoir through allo-effect following allogeneic HSC transplantation, to facilitate translation to human patients. We propose to develop an MHC-defined CCR5-mutant nonhuman primate (NHP) bone marrow transplantation model at the Wisconsin National Primate Research Center (WNPRC) to address the critical questions of HSC-based therapies for HIV. This model will employ Mauritian Cynomolgus monkeys (MCMs) with well-defined MHC to control genetic factors in the setting of allogeneic bone marrow transplant.
In aim 1, we will use CRISPR/Cas9 methods in MCM induced pluripotent stem cell (iPSC) lines to optimize efficient targeting of the MCM CCR5-locus with minimal off-target effects.
In aim 2, we will confirm the feasibility and accuracy of CCR5 genomic editing in IVF-derived MCM embryos and generate CCR5-mutant MCMs.
In aim 3, we will evaluate the engraftment of WT and CCR5-mutant HSCs in SHIV-infected, MHC and blood group identical MCM recipients using a myeloablative BMT regimen and assess the effect of these transplants on persistence of SHIV infection. The proposed studies will establish a CCR5-mutant MHC- defined NHP model and will demonstrate utility for evaluation of HSC-based therapies for AIDS. Development of these resources will benefit AIDS researchers at multiple NIH institutions, including ORIP, NHLBI, NIAID, NIDKK, NICHD, and NINDS. Although CCR5-mutant mutation protects from HIV infection, the lack of CCR5 is also associated with increased susceptibility to West Nile virus infection, and other infections including Toxoplasma gondii, Mycobacterium tuberculosis, Chlamydia trachomatis, Listeria, and Plasmodium. Thus, for example, access to CCR5-mutant NHPs will open unique opportunities to establish NHP models for West Nile infection for evaluation of vaccine efficacy and advance the use of NHPs for studies of other infections which may require CCR5-mutant hosts to reproduce a disease course observed in susceptible humans. In addition, advances in gene editing technologies in NHP models will facilitate their clinical translation for treatment of genetic disorders in humans.
Successful cure of HIV infection via transplantation has raised the hope that a similar approach could be applicable for other HIV patients; however, there are a number of questions that remain regarding hematopoietic stem cell-based therapies for HIV. These questions cannot be answered in controlled studies in human patients. Our novel proposal to develop methods to address these questions with genetically-modified nonhuman primates will provide a platform which can allow us and other investigators to define the potential value and application of cells with targeted gene modification for HIV, and other infectious disease, such as West Nile Virus.