In vivo transduction of primitive mobilized hematopoietic stem cells after intravenous injection of integrating adenovirus vectors

Current protocols for hematopoietic stem/progenitor cell (HSPC) gene therapy, involving the transplantation of ex vivo genetically modified HSPCs are complex and not without risk for the patient. We developed a new approach for in vivo HSPC transduction that does not require myeloablation and transplantation. It involves subcutaneous injections of granulocyte-colony-stimulating factor/AMD3100 to mobilize HSPCs from the bone marrow (BM) into the peripheral blood stream and the IV injection of an integrating, helper-dependent adenovirus (HD-Ad5/35++) vector system. These vectors target CD46, a receptor that is uniformly expressed on HSPCs. We demonstrated in human CD46 transgenic mice and immunodeficient mice with engrafted human CD34+ cells that HSPCs transduced in the periphery home back to the BM where they stably express the transgene. In hCD46 transgenic mice, we showed that our in vivo HSPC transduction approach allows for the stable transduction of primitive HSPCs. Twenty weeks after in vivo transduction, green fluorescent protein (GFP) marking in BM HSPCs (Lin-Sca1+Kit- cells) in most of the mice was in the range of 5% to 10%. The percentage of GFP-expressing primitive HSPCs capable of forming multilineage progenitor colonies (colony-forming units [CFUs]) increased from 4% of all CFUs at week 4 to 16% at week 12, indicating transduction and expansion of long-term surviving HSPCs. Our approach was well tolerated, did not result in significant transduction of nonhematopoietic tissues, and was not associated with genotoxicty. The ability to stably genetically modify HSPCs without the need of myeloablative conditioning is relevant for a broader clinical application of gene therapy

Re-educating immunity in respiratory allergies: the potential for hematopoietic stem cell-mediated gene therapy

Respiratory allergies represent a significant disease burden worldwide affecting up to 300 million people globally. Medication and avoidance of known triggers do not address the underlying pathology. Traditional immunotherapies for allergy aim to reinstate immune homeostasis but require years of treatment and have poor long-term efficacy. Novel approaches, such as gene-engineered hematopoietic stem cell transplantation, induce profound antigen-specific tolerance in autoimmunity. Recent evidence shows this approach may also have therapeutic utility for allergy. Here, we review the mechanisms of antigen-specific tolerance and the potential of stem cell-mediated gene therapy to induce tolerance in allergic respiratory diseases