title: Total body irradiation must be delivered at high dose for efficient engraftment and tolerance in a rhesus stem cell gene therapy model.
abstract: Reduced intensity conditioning (RIC) is desirable for hematopoietic stem cell (HSC) gene therapy applications. However, low gene marking was previously observed in gene therapy trials, suggesting that RIC might be insufficient for (i) opening niches for efficient engraftment and/or (ii) inducing immunological tolerance for transgene-encoded proteins. Therefore, we evaluated both engraftment and tolerance for gene-modified cells using our rhesus HSC gene therapy model following RIC. We investigated a dose de-escalation of total body irradiation (TBI) from our standard dose of 10Gy (10, 8, 6, and 4Gy), in which rhesus CD34(+) cells were transduced with a VSVG-pseudotyped chimeric HIV-1 vector encoding enhanced green fluorescent protein (GFP) (or enhanced yellow fluorescent protein (YFP)). At ~6 months after transplantation, higher-dose TBI resulted in higher gene marking with logarithmic regression in peripheral blood cells. We then evaluated immunological tolerance for gene-modified cells, and found that lower-dose TBI allowed vigorous anti-GFP antibody production with logarithmic regression, while no significant anti-VSVG antibody formation was observed among all TBI groups. These data suggest that higher-dose TBI improves both engraftment and immunological tolerance for gene-modified cells. Additional immunosuppression might be required in RIC to induce tolerance for transgene products. Our findings should be valuable for developing conditioning regimens for HSC gene therapy applications.
authors.affiliation: Molecular and Clinical Hematology Branch, National Heart Lung and Blood Institutes (NHLBI)/National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH) , Bethesda, Maryland, USA.
authors.forename: Naoya
authors.initials: N
authors.lastname: Uchida
authors.affiliation: Molecular and Clinical Hematology Branch, National Heart Lung and Blood Institutes (NHLBI)/National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH) , Bethesda, Maryland, USA.
authors.forename: R Patrick
authors.initials: RP
authors.lastname: Weitzel
authors.affiliation: Molecular and Clinical Hematology Branch, National Heart Lung and Blood Institutes (NHLBI)/National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH) , Bethesda, Maryland, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Shvygin
authors.affiliation: Molecular and Clinical Hematology Branch, National Heart Lung and Blood Institutes (NHLBI)/National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH) , Bethesda, Maryland, USA.
authors.forename: Luke P
authors.initials: LP
authors.lastname: Skala
authors.affiliation: Molecular and Clinical Hematology Branch, National Heart Lung and Blood Institutes (NHLBI)/National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH) , Bethesda, Maryland, USA.
authors.forename: Lydia
authors.initials: L
authors.lastname: Raines
authors.affiliation: Hematology Branch, NHLBI, NIH , Bethesda, Maryland, USA.
authors.forename: Aylin C
authors.initials: AC
authors.lastname: Bonifacino
authors.affiliation: Hematology Branch, NHLBI, NIH , Bethesda, Maryland, USA.
authors.forename: Allen E
authors.initials: AE
authors.lastname: Krouse
authors.affiliation: Hematology Branch, NHLBI, NIH , Bethesda, Maryland, USA.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Metzger
authors.affiliation: Hematology Branch, NHLBI, NIH , Bethesda, Maryland, USA.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Donahue
authors.affiliation: Molecular and Clinical Hematology Branch, National Heart Lung and Blood Institutes (NHLBI)/National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH) , Bethesda, Maryland, USA.
authors.forename: John F
authors.initials: JF
authors.lastname: Tisdale