title: Toward reducing immunogenicity of enzyme replacement therapy: altering the specificity of human β-glucuronidase to compensate for α-iduronidase deficiency.
abstract: Enzyme replacement therapy (ERT) is an effective treatment for many patients with lysosomal storage disorders caused by deficiency in enzymes involved in cell metabolism. However, immune responses that develop against the administered enzyme in some patients can hinder therapeutic efficacy and cause serious side effects. Here we investigated the feasibility of a general approach to decrease ERT immunogenicity by altering the specificity of a normal endogenous enzyme to compensate for a defective enzyme. We sought to identify human β-glucuronidase variants that display α-iduronidase activity, which is defective in mucopolysaccharidosis (MPS) type I patients. A human β-glucuronidase library was screened by the Enzyme Cleavable Surface-Tethered All-purpose Screen sYstem to isolate variants that exhibited 100-290-fold greater activity against the α-iduronidase substrate 4-methylumbelliferyl α-l-iduronide and 7900-24 500-fold enzymatic specificity shift when compared with wild-type β-glucuronidase. In vitro treatment of MPS I cells with the β-glucuronidase variants significantly restored lysosome appearance similar to treatment with α-iduronidase. Our study suggests that β-glucuronidase variants can be isolated to display α-iduronidase activity and produce significant phenotype improvement of MPS I cells. This strategy may represent a possible approach to produce enzymes that display therapeutic benefits with potentially less immunogenicity.
authors: Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 11490, Taiwan Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan.
authors: Huai-Yao
authors: HY
authors: Chuang
authors: Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan.
authors: Ching-Shu
authors: CS
authors: Suen
authors: Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan.
authors: Ming-Jing
authors: MJ
authors: Hwang
authors: Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 11490, Taiwan Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan sroff@ibms.sinica.edu.tw.
authors: Steve R
authors: SR
authors: Roffler
mesh_terms: D000595:Amino Acid Sequence; D056947:Enzyme Replacement Therapy / Q000009:adverse effects / Q000379:methods; D005966:Glucuronidase / Q000737:chemistry / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D007068:Iduronidase / Q000172:deficiency* / Q000378:metabolism*; D008958:Models, Molecular; D009083:Mucopolysaccharidoses; D015202:Protein Engineering
chemical_list: D005966:Glucuronidase; D007068:Iduronidase
keywords: enzyme replacement therapy; mucopolysaccharidosis (MPS); protein evolution; α-iduronidase; β-glucuronidase