The degree of phenotypic correction of murine beta -thalassemia intermedia following lentiviral-mediated transfer of a human gamma-globin gene is influenced by chromosomal position effects and vector copy number.
Increased fetal hemoglobin (HbF) levels diminish the clinical severity of beta-thalassemia and sickle cell anemia. A treatment strategy using autologous stem cell-targeted gene transfer of a gamma-globin gene may therefore have therapeutic potential. We evaluated oncoretroviral- and lentiviral-based gamma-globin vectors for expression in transduced erythroid cell lines. Compared with gamma-globin, oncoretroviral vectors containing either a beta-spectrin or beta-globin promoter and the alpha-globin HS40 element, a gamma-globin lentiviral vector utilizing the beta-globin promoter and elements from the beta-globin locus control region demonstrated a higher probability of expression. This lentiviral vector design was evaluated in lethally irradiated mice that received transplants of transduced bone marrow cells. Long-term, stable erythroid expression of human gamma-globin was observed with levels of vector-encoded gamma-globin mRNA ranging from 9% to 19% of total murine alpha-globin mRNA. The therapeutic efficacy of the vector was subsequently evaluated in a murine model of beta-thalassemia intermedia. The majority of mice that underwent transplantation expressed significant levels of chimeric m(alpha)(2)h(gamma)(2) molecules (termed HbF), the amount of which correlated with the degree of phenotypic improvement. A group of animals with a mean HbF level of 21% displayed a 2.5 g/dL (25 g/L) improvement in Hb concentration and normalization of erythrocyte morphology relative to control animals. gamma-Globin expression and phenotypic improvement was variably lower in other animals due to differences in vector copy number and chromosomal position effects. These data establish the potential of using a gamma-globin lentiviral vector for gene therapy of beta-thalassemia.
Persons
Derek A
DA
Division of Experimental Hematology, Department of Hematology and Oncology, St Jude Children's Research Hospital, Memphis, TN 38105, USA. derek.persons@stjude.org
Hargrove
Phillip W
PW
Allay
Esther R
ER
Hanawa
Hideki
H
Nienhuis
Arthur W
AW
D000818:Animals; D001854:Bone Marrow Cells / Q000378:metabolism; D016026:Bone Marrow Transplantation; D004912:Erythrocytes / Q000378:metabolism; D005319:Fetal Hemoglobin / Q000032:analysis; D015870:Gene Expression; D015316:Genetic Therapy; D005822:Genetic Vectors; D005914:Globins / Q000172:deficiency / Q000235:genetics*; D006801:Humans; D016086:Lentivirus / Q000235:genetics*; D004915:Leukemia, Erythroblastic, Acute; D051379:Mice; D018345:Mice, Knockout; D010641:Phenotype; D012333:RNA, Messenger / Q000032:analysis; D012190:Retroviridae / Q000235:genetics; D013154:Spleen / Q000166:cytology; D014162:Transfection; D014407:Tumor Cells, Cultured; D017086:beta-Thalassemia / Q000235:genetics / Q000628:therapy*
D012333:RNA, Messenger; D005914:Globins; D005319:Fetal Hemoglobin