We tested a new in vivo hematopoietic stem cell (HSC) transduction/selection approach in rhesus macaques using HSCtropic, integrating, helper-dependent adenovirus vectors (HDAd5/35++) designed for the expression of human g-globin in red blood cells (RBCs) to treat hemoglobinopathies. We show that HDAd5/35++ vectors preferentially transduce HSCs in vivo after intravenous injection into granulocyte colony-stimulating factor (G-CSF)/AMD3100-mobilized animals and that transduced cells return to the bone marrow and spleen. The approach was well tolerated, and the activation of proinflammatory cytokines that are usually associated with intravenous adenovirus vector injection was successfully blunted by pre-treatment with dexamethasone in combination with interleukin (IL)-1 and IL-6 receptor blockers. Using our MGMT P140K -based in vivo selection approach, g-globin + RBCs increased in all animals with levels up to 90%. After selection, the percentage of g-globin + RBCs declined, most likely due to an immune response against human transgene products. Our biodistribution data indicate that g-globin + RBCs in the periphery were mostly derived from mobilized HSCs that homed to the spleen. Integration site analysis revealed a polyclonal pattern and no genotoxicity related to transgene integrations. This is the first proof-of-concept study in nonhuman primates to show that in vivo HSC gene therapy could be feasible in humans without the need for high-dose chemotherapy conditioning and HSC transplantation.
Key Points
An in vivo HSC transduction/selection allows for high-level protein expression from erythroid cells without side effects on erythropoiesis. This approach that did not require ex vivo HSC manipulation and transplantation resulted in phenotypic correction of murine hemophilia A.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.