| Summary: | 碩士 === 國立陽明大學 === 臨床醫學研究所 === 107 === Fabry disease (FD) is an X-linked lysosomal storage disease, which is caused by genetic mutations on human GLA gene that encoded alpha-galactosidase A enzyme. The incidence of FD was around 1 in 50,000 worldwide, but relatively higher in Taiwan at approximately 1 per 1,471 due to a specific mutation in the 4th intron (IVS4+919 G>A). The biological function of GLA is involved in the breakdown of globotriaosylceramide (Gb3) in lysosome. Lack of GLA enzyme activity resulted in accumulation of Gb3 and caused life-threatening complications such as stroke, cardiac, and renal failure.
The enzyme replacement therapy (ERT) with recombinant human GLA (rhGLA) is the standard therapy for FD. Enzyme was uptaken by cells through binding to the cation-independent mannose-6-phosphate receptor (CI-M6PR) and entered lysosome to break down excessive accumulated Gb3. However, ERT has several disadvantages, such as short half-life of protein drug, limited efficacy for patients with renal failure and extremely expensive, which is a burden for not only FD patient but our National Health Insurance. Therefore, development of a new therapeutic strategy for FD is highly demanded.
Recently, clinical studies on gene therapy using adeno-associated virus (AAV) vectors are increasing, which may be a promising therapeutic approach for FD as well. Previous researches took advantage of AAV1, AAV2, AAV8 to express the therapeutic GLA gene in Fabry mice. However, the enzyme activity in kidney was not restored, results in treatment failures and limited the improvement of FD symptoms in mouse model.
In this study, we try to target the most affected tissue in Fabry disease, taking advantage of serotypes endowed with heart and kidney tropism. We used AAV9 or Anc80 to deliver the GLA transgenes to Gla knockout mice. GLA enzyme activity was significantly higher in plasma, liver, heart and kidney of Fabry mice after administration of AAV9-GLA than those with AAV8-GLA and Anc80-GLA. We had also determined that α-Gal A activity can sustain for at least 3 months. Further more, all groups showed low immunogenicity in Fabry mice. Moreover, AAV9 group ameliorated proteinuria symptom comparing to untreat groups.
Previously, our team had successfully generated a GLA-IGF2 fusion recombinant protein which showed more efficient up-taken ability by cells when compared with recombinant GLA. Unfortunately, when we used AAV vector mediated GLA-IGF2 gene therapy to evaluate the therapeutic efficacy in Fabry disease mice model, AAV-GLA-IGF2 was highly trapped in the liver instead of secreting into circulation and show no significant improvement in other organs.
Taken together, AAV9-GLA increased enzyme activity in plasma and tissues, improved therapeutic efficacy and showed low immunogenicity in mice. Our data demonstrated the therapeutic potential of AAV9 vector–mediated GLA gene therapy for Fabry disease. Hopefully, by single administration of AAV gene therapy, we can resolve the inconvenience of repeated injection of ERT and improve patient’s life quality. The use of AAV gene therapy may become a new strategy for treating FD.
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