The degree of correction of β-thalassemic red cell morphologic abnormalities correlates with the level of HbF resulting from lentiviral vector–encoded human γ-globin.

Wright-Giemsa–stained PB smears from (A) normal mouse, (B) mouse that received transplant of mock-transduced β-thalassemic BM cells, (C-F) mice that received transplants of γ-globin vector–transduced β-thalassemic BM cells and having HbF levels of 13%, 14%, 35%, and 16%.