Long-term cure of the photosensitivity of murine erythropoietic protoporphyria by preselective gene therapy

Abstract

Definitive cure of an animal model of a human disease by gene transfer into hematopoietic stem cells has not yet been accomplished in the absence of spontaneous in vivo selection for transduced cells. Erythropoietic protoporphyria is a genetic disease in which ferrochelatase is defective. Protoporphyrin accumulates in erythrocytes, leaks into the plasma and results in severe skin photosensitivity. Using a mouse model of erythropoietic protoporphyria, we demonstrate here that ex vivo preselection of hematopoietic stem cells transduced with a polycistronic retrovirus expressing both human ferrochelatase and green fluorescent protein results in complete and long-term correction of skin photosensitivity in all transplanted mice.

Liver transplantation for erythropoietic protoporphyria liver disease

“…Bone marrow transplantation has the advantage of correcting the deficiency of ferrochelatase activity in the bone marrow. Experimental studies using bone marrow replacement in a mouse model of EPP, 34,35 as well as studies in a human with the disorder, 36 indicate that this will be the case. Patients receiving bone marrow transplantation for nonmalignant diseases generally have a 3-year survival rate of 70-90% if the donor is a matched sibling and 36-65% if the donor is unrelated.…”

Persisting multilineage transgene expression in the clonal progeny of a hematopoietic stem cell

“…Despite selection prior to BMT, all but one study published to date resulted in an incomplete and variable transgene chimerism. 9,10,[12][13][14][15] The single study with virtually complete expression in multiple lineages 11 did not show data regarding reconstitution of secondary recipients, hematopoietic clonality or transgene copy number. Thus, it remained unclear whether single retrovirally transduced HSCs are capable of multilineage transgene expression in vivo.…”

“…Mature erythroid cells or platelets have not been evaluated. Other studies have sorted cells prior to primary BMT, either by flow cytometry [9][10][11][12][13][14] or immunoaffinity selection, 15 showing that both procedures increase the likelihood for obtaining active transgene expression in vivo. Despite selection prior to BMT, all but one study published to date resulted in an incomplete and variable transgene chimerism.…”

Succès de la thérapie génique d’un modèle murin de porphyrie érythropoïétique congénitale

“…Les résultats d'une thé-rapie génique efficace dans un nouveau modèle murin de cette porphyrie sont exposés dans cet article. < modèle murin de protoporphyrie érythropoïétique ou PPE, maladie différente de la PEC [10][11][12]. Le vecteur lentiviral thérapeutique utilisé, dénommé Esp-UROS, est un vecteur dit « SIN » (self inactivation) ou autoinactivé, possédant un promoteur spécifiquement activé dans la lignée érythroïde (HS40/Ankyrine), la séquence ADNc UROS humaine, ainsi que l'élément de régulation post-transcriptionnel WPRE.…”

“…Cet avantage sélectif des précurseurs des globules rouges corrigés constitue un argument important pour espérer un bénéfice théra-peutique chez l'homme, même si la totalité des cellules souches déficientes n'a pas été corrigée. Ces résultats sont différents de ceux qui sont obtenus dans la protoporphyrie érythropoïétique : il n'y a pas d'anémie hémolytique dans cette maladie, et l'avantage sélectif des progéniteurs érythroïdes corrigés n'y existe pas [10][11][12].…”