Alpha-galactosidase A-Tat fusion enhances storage reduction in hearts and kidneys of Fabry mice

Abstract

The protein transduction domain from human immunodeficiency virus (HIV) Tat allows proteins to penetrate the cell membrane. Enhanced cellular uptake of therapeutic proteins could benefit a number of disorders. This is especially true for lysosomal storage disorders (LSDs) where enzyme replacement therapy (ERT) and gene therapy have been developed. We developed a novel recombinant lentiviral vector (LV) that engineers expression of alpha-galactosidase A (alpha-gal A)-Tat fusion protein for correction of Fabry disease, the second-most prevalent LSD with manifestations in the brain, kidney and heart. In vitro experiments confirmed mannose-6-phosphate independent uptake of the fusion factor. Next, concentrated therapeutic LV was injected into neonatal Fabry mice. Analysis of tissues at 26 wks demonstrated similar alpha-gal A enzyme activities but enhanced globotriaosylceramide (Gb3) reduction in hearts and kidneys compared with the alpha-gal A LV control. This strategy might advance not only gene therapy for Fabry disease and other LSDs, but also ERT, especially for cardiac Fabry disease.

Figure 1

Schematic of alignment of Tat PTD domain at the carboxy-terminus of α-galactosidase A.

Figure 2

Plasma α-gal A activity in high-dose LV-injected Fabry mice from Experiment 1. *P < 0.001 compared with PBS-injected group. ^#P < 0.05 compared with LV/α-gal A-Tat-injected group.

Figure 3

Plasma α-gal A activity in low-dose LV-injected Fabry mice from Experiment 2.

Figure 4

α-Gal A and Tat mRNA expression and α-gal A enzyme activity. (A) Similar levels of α-gal A and Tat mRNA expression in transduced 3T3 cells were confirmed by RT-PCR. (B) α-Gal A activity secreted from transduced HeLa cells. (C) Uptake of secreted α-gal A and α-gal A/Tat in Fabry mouse fibroblasts with or without M6P. NT, non-transduced; RT, reverse transcriptase; sup, supernatant; M6P, mannose-6-phosphate. α-Gal A activity assays were measured in triplicates. Values are mean ± SD.