Ex Vivo Gene Therapy Treats Bone Complications of Mucopolysaccharidosis Type II Mouse Models through Bone Remodeling Reactivation.

Mucopolysaccharidosis type II is a disease caused by organ accumulation of glycosaminoglycans due to iduronate 2-sulfatase deficiency. This study investigated the pathophysiology of the bone complications associated with mucopolysaccharidosis II and the effect of lentivirus-mediated gene therapy of hematopoietic stem cells on bone lesions of mucopolysaccharidosis type II mouse models in comparison with enzyme replacement therapy. Bone volume, density, strength, and trabecular number were significantly higher in the untreated mucopolysaccharidosis type II mice than in wild-type mice. Accumulation of glycosaminoglycans caused reduced bone metabolism. Specifically, persistent high serum iduronate 2-sulfatase levels and release of glycosaminoglycans from osteoblasts and osteoclasts in mucopolysaccharidosis type II mice that had undergone gene therapy reactivated bone lineage remodeling, subsequently reducing bone mineral density, strength, and trabecular number to a similar degree as that observed in wild-type mice. Bone formation, resorption parameters, and mineral density in the diaphysis edge did not appear to have been affected by the irradiation administered as a pre-treatment for gene therapy. Hence, the therapeutic effect of gene therapy on the bone complications of mucopolysaccharidosis type II mice possibly outweighed that of enzyme replacement therapy in many aspects.

The production of human glucocerebrosidase in glyco-engineered Nicotiana benthamiana plants.

For the production of therapeutic proteins in plants, the presence of ß1,2-xylose and core α1,3-fucose on plants' N-glycan structures has been debated for their antigenic activity. In this study, RNA interference (RNAi) technology was used to down-regulate the endogenous N-acetylglucosaminyltransferase I (GNTI) expression in Nicotiana benthamiana. One glyco-engineered line (NbGNTI-RNAi) showed a strong reduction of plant-specific N-glycans, with the result that as much as 90.9% of the total N-glycans were of high-mannose type. Therefore, this NbGNTI-RNAi would be a promising system for the production of therapeutic glycoproteins in plants. The NbGNTI-RNAi plant was cross-pollinated with transgenic N. benthamiana expressing human glucocerebrosidase (GC). The recombinant GC, which has been used for enzyme replacement therapy in patients with Gaucher's disease, requires terminal mannose for its therapeutic efficacy. The N-glycan structures that were presented on all of the four occupied N-glycosylation sites of recombinant GC in NbGNTI-RNAi plants (GC(gnt1) ) showed that the majority (ranging from 73.3% up to 85.5%) of the N-glycans had mannose-type structures lacking potential immunogenic ß1,2-xylose and α1,3-fucose epitopes. Moreover, GC(gnt1) could be taken up into the macrophage cells via mannose receptors, and distributed and taken up into the liver and spleen, the target organs in the treatment of Gaucher's disease. Notably, the NbGNTI-RNAi line, producing GC, was stable and the NbGNTI-RNAi plants were viable and did not show any obvious phenotype. Therefore, it would provide a robust tool for the production of GC with customized N-glycan structures.

Frequency of de novo mutations in Japanese patients with Fabry disease.

We examined alpha-galactosidase A (GLA) gene mutations in 74 Japanese families with Fabry disease (FD) to determine the frequency of de novo mutations. In 5 of 74 families (6.8%), the probands had no positive family histories and were diagnosed as de novo because their parents had no mutations in GLA gene. The parents of Fabry patients do not necessarily have mutations in GLA gene which is an important consideration in genetic counseling for FD.

Administration of anti-CD3 antibodies modulates the immune response to an infusion of α-glucosidase in mice.

Animal and human studies of enzyme replacement therapy (ERT) for Pompe disease (PD) have indicated that antibodies (Abs) generated against infused recombinant human α-glucosidase (rhGAA) can have a negative impact on the therapeutic outcome and cause hypersensitivity reactions. We showed that parenteral administration of anti-CD3 Abs into mice can reduce the titer of anti-human GAA Abs in wild-type mice administered the enzyme. Mice that had been treated with anti-CD3 Abs and then subjected to a secondary challenge with rhGAA showed a lower increase in Ab titers than control mice. Moreover, the administration of anti-CD3 Abs also reduced the levels of pre-existing Abs. Treatment with anti-CD3 Abs also prevented a lethal hypersensitivity reaction and reduced the Ab titers in a mouse model of PD. Mice treated with anti-CD3 Abs showed reduced numbers of CD4(+) and CD8(+) cells, and an increased ratio of CD4(+)CD25(+)/CD4(+) and CD4(+)CD25(+)FoxP3(+)/CD4(+) cells. When the CD4(+)CD25(+) cells were depleted using anti-CD25 Abs, the observed reduction in Abs against the enzyme by anti-CD3 Abs was abrogated. This suggests that CD4(+)CD25(+) cells are important for the immune suppressive activity of anti-CD3 Abs. In summary, anti- CD3 Abs are useful for inducing immune tolerance to ERT for PD.

Reduced alpha-Gal A enzyme activity in Fabry fibroblast cells and Fabry mice tissues induced by serum from antibody positive patients with Fabry disease.

Fabry disease is a progressive, life-threatening lysosomal storage disorder which is characterized by deficient activity of the lysosomal enzyme alpha-galactosidase A. Studies have demonstrated that both enzyme preparations currently available for treatment of Fabry disease (i.e., agalsidase beta and agalsidase alpha) elicit immune responses in the majority of patients which negatively influences the reduction of urinary globotriaosylceramide concentration. In the current study, agalsidase beta antibodies were found to be associated with inhibition of alpha-Gal A enzyme activity in cultured Fabry fibroblast and tissues from Fabry mice. However, the negative effect of antibody formation could be overcome by increasing the dose of enzyme administered to mice. In conclusion, antibody titers and the dose of enzyme influenced alpha-Gal A enzyme activities in vivo. Further studies are required to investigate to what extend antibody formation impacts on therapeutic responses in antibody positive Fabry patients receiving enzyme replacement therapy and if negative effects can be overcome by adjusting the dose of enzyme.