ENZYME AND GENE THERAPY OF MPS I IN ANIMAL MODELS

粘多糖病I （MPS I, Hurler， Hurler/Scheie和Scheie综合征）的分子基础是编码α - l -伊杜糖醛酸酶的基因突变，导致酶活性缺失，未降解的糖胺聚糖积累和全身性疾病。由于α - l -伊杜糖醛酸酶是一种溶酶体酶，可以被受体介导的内吞作用分泌和吸收，MPS I一直被认为是替代疗法的主要候选者。由造血来源的供体细胞（可能是巨噬细胞）提供的α - l -伊杜糖醛酸酶被认为是骨髓移植后疾病进展变化的原因。重组α - l -伊杜糖醛酸酶也能改变病程。该酶先前在犬多磺酸粘多糖1型模型中观察到的治疗效果已经足够有希望在多磺酸粘多糖1型患者中进行临床试验。但是，即使重组α -l -伊杜糖醛酸酶可能很快就会成为一种药物，仍然需要开发有效和持久的基因治疗方法。为了获得合适的动物模型，我们通过靶向破坏α - l -伊杜糖醛酸酶基因产生了突变小鼠。目的1是在生化、病理、行为和临床水平上确定MPS I小鼠模型的表型。目的2是确定给药人重组α - l -伊杜糖醛酸酶对疾病表型的影响，以便为基于基因的程序提供比较基础。目的3是比较过表达人α - l -伊杜糖醛酸酶的基因修饰骨髓移植与表达正常水平的骨髓移植，以改变疾病表型的有效性。目的4是确定四环素诱导的α - l -伊杜糖醛酸酶在巨噬细胞中表达的有效性，作为酶递送到受影响器官，特别是大脑的手段，并将其与上述程序进行比较，以改变疾病表型的能力。拟议的研究代表了我们为MPS I患者开发治疗方案的长期计划的步骤。

The molecular basis of Mucopolysaccharidosis I (MPS I, Hurler, Hurler/Scheie and Scheie syndromes) is mutations in the gene encoding alpha-L-iduronidase, resulting in absence of enzyme activity, accumulation of undegraded glycosaminoglycans, and systemic disease. Because alpha-L-iduronidase, a lysosomal enzyme, can be secreted as well as taken up by receptor-mediated endocytosis, MPS I has long been considered a prime candidate for replacement therapy. Alpha-L-Iduronidase provided by donor cells of hematopoietic origin (probably macrophages) is thought to be responsible for changes in disease progression that are seen after bone marrow transplantation. The course of the disease can also be altered by administration of recombinant alpha-L-iduronidase. The therapeutic effect of the enzyme previously observed in the canine MPS I model had been promising enough to generate a clinical trial in MPS I patients. But even though recombinant alpha-L-iduronidase may soon become available as a pharmaceutical, there is still a need for developing effective and long-lasting gene therapy. To have a suitable animal model, we have produced mutant mice by targeted disruption of the alpha-L-iduronidase gene. Aim 1 is to define the phenotype of the MPS I mouse model at the biochemical, pathological, behavioral and clinical levels. Aim 2 is to determine the effect of administration of human recombinant alpha-L-iduronidase on the disease phenotype, in order to provide a basis of comparison for gene-based procedures. Aim 3 is to compare transplantation of gene-modified bone marrow over-expressing human alpha-L-iduronidase with transplantation of bone marrow expressing normal levels of the enzyme, for effectiveness in altering the disease phenotype. Aim 4 is to determine the effectiveness of tetracycline-inducible alpha-L-iduronidase expression in macrophages as a means of enzyme delivery to affected organs, in particular to the brain, as well as to compare it with the above procedures for ability to alter the disease phenotype. The proposed studies represent steps in our long-term program to develop treatment for patients affected with MPS I.