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Evaluation of engraftment and immunological tolerance after reduced intensity conditioning in a rhesus hematopoietic stem cell gene therapy model.

ABSTRACT: Reduced intensity conditioning (RIC) is desirable for hematopoietic stem cell (HSC) targeted gene therapy; however, RIC may be insufficient for efficient engraftment and inducing immunological tolerance to transgenes. We previously established long-term gene marking in our rhesus macaque autologous HSC transplantation model following 10?Gy total body irradiation (TBI). In this study, we evaluated RIC transplantation with 4?Gy TBI in two rhesus macaques that received equal parts of CD34(+) cells transduced with green fluorescent protein (GFP)-expressing lentiviral vector and empty vector not expressing transgenes. In both animals, equivalently low gene marking between GFP and empty vectors was observed 6 months post-transplantation, even with efficient transduction of CD34(+) cells in vitro. Autologous lymphocyte infusion with GFP marking resulted in an increase of gene marking in lymphocytes in a control animal with GFP tolerance, but not in the two RIC-transplanted animals. In vitro assays revealed strong cellular and humoral immune responses to GFP protein in the two RIC-transplanted animals, but this was not observed in controls. In summary, 4?Gy TBI is insufficient to permit engraftment of genetically modified HSCs and induce immunological tolerance to transgenes. Our findings should help in the design of conditioning regimens in gene therapy trials.

SUBMITTER: Uchida N

PROVIDER: S-EPMC4699286 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature

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Evaluation of engraftment and immunological tolerance after reduced intensity conditioning in a rhesus hematopoietic stem cell gene therapy model.

Uchida N N Weitzel R P RP Evans M E ME Green R R Bonifacino A C AC Krouse A E AE Metzger M E ME Hsieh M M MM Donahue R E RE Tisdale J F JF

Gene therapy 20131121 2

Reduced intensity conditioning (RIC) is desirable for hematopoietic stem cell (HSC) targeted gene therapy; however, RIC may be insufficient for efficient engraftment and inducing immunological tolerance to transgenes. We previously established long-term gene marking in our rhesus macaque autologous HSC transplantation model following 10 Gy total body irradiation (TBI). In this study, we evaluated RIC transplantation with 4 Gy TBI in two rhesus macaques that received equal parts of CD34(+) cells ...[more]

PMID: 24257347

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Project description:The high incidence of human herpesvirus-6 (HHV-6) reactivation, potentially interfering with engraftment after umbilical cord blood (UCB) hematopoietic cell transplantation (HCT), remains a major challenge. To potentially address this problem, we evaluated the effect of prophylactic foscarnet administered twice daily beginning on day +7 and continuing through engraftment in 25 patients. To determine the impact of foscarnet on HHV-6, engraftment, and other transplantation outcomes, we compared results in 61 identically treated patients with hematologic malignancies. Treatment and control groups underwent reduced-intensity conditioning UCB HCT with a conditioning regimen of fludarabine, cyclophosphamide, and total body irradiation 200 cGy with or without antithymocyte globulin (ATG), using sirolimus plus mycophenolate mofetil immune suppression. The treatment and control groups were similar in terms of age, disease risk, use of ATG, Hematopoietic Cell Transplantation Comorbidity Index, and graft CD34 cell dose; however, foscarnet-treated patients were less likely to receive a double UCB graft and to be treated more recently (2016 to 2018). The cumulative incidence of HHV-6 reactivation by day +100 was 63% for all patients (95% confidence interval [CI], 51% to 75%) and was not significantly different between the 2 groups. HHV-6 reactivation occurred at a median of 34 days in the foscarnet group and 25.5 days in the control group. The incidence of neutrophil engraftment at day 42 was higher in the foscarnet group compared with the control group (96%; [95% CI, 83% to 100%] versus 75% [95% CI, 64% to 85%]; P< .01). The cumulative incidence of platelet engraftment by 6 months was 92% (95% CI, 69% to 100%) for the foscarnet group versus 75% (95% CI, 60% to 90%) for the control group (P= .08), and multivariate analysis identified the use of foscarnet as an independent predictor of better platelet engraftment. No patients died as a result of graft failure in recipients of foscarnet, whereas 5 patients died from graft failure in the control group. Six-month overall survival (OS) and nonrelapse mortality (NRM) were better in the foscarnet group (96% versus 72% [P= .02] and 4% versus 18% [P= .07], respectively). Even though foscarnet prophylaxis did not prevent HHV-6 viremia, we observed a delay in time to HHV-6 reactivation, a trend toward differences in engraftment, NRM, and OS compared with historical controls.

Dataset Information

Evaluation of engraftment and immunological tolerance after reduced intensity conditioning in a rhesus hematopoietic stem cell gene therapy model.

Publications

Evaluation of engraftment and immunological tolerance after reduced intensity conditioning in a rhesus hematopoietic stem cell gene therapy model.

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