Clearing of globotriaosylceramide from endothelial vessels of ocular conjunctiva in patients with Fabry disease treated with agalsidase alfa

Abstract

Abstract Introduction: Fabry disease is an X‐linked inborn metabolic error caused by a deficiency of lysosomal α‐galactosidase A. Globotriaosylceramide (Gb3) accumulates in lysosomes of various cells. At the moment, enzyme replacement therapy (ERT) is the only available specific treatment for patients with Fabry disease. Enzyme infusions reduce the Gb3 content of plasma, urine sediment and tissue. In a previous study, we reported the development of a method to specifically detect Gb3 deposits by immunofluorescence in conjunctival biopsies. Aim: The aim of this work is to evaluate the clearance of Gb3 in cells from the conjunctiva in patients with Fabry disease treated with agalsidase alfa. Methods: Conjunctival biopsies were obtained from three hemizygous and two heterozygous patients, before and after 6 months of treatment with agalsidase alfa. The specimens were processed for direct immunofluorescence using an anti‐Gb3 monoclonal antibody and light microscopy using a mouse polyclonal antiserum specific for α‐galactosidase A. Results: Positive immunofluorescence was not observed in cells from the blood vessels of patients with Fabry disease after 6 months of treatment, as compared with the specimens before the treatment, which were positive. We detected Gb3 in stromal/macrophage cells that were distal from the blood vessels where the enzyme was circulating. Specific staining for α‐galactosidase A revealed the presence of this protein in the tissue of patients after ERT, but not before. Conclusion: Agalsidase alfa eliminated Gb3 deposits from the cells of blood vessel walls in patients with Fabry disease after 6 months of treatment. The deposits in stromal cells were not removed, probably because the enzyme must diffuse into the tissue to reach these cells and/or because of the short length of therapy. This method may be useful to evaluate the effectiveness of ERT.