Reduction in Brain Heparan Sulfate with Systemic Administration of an IgG Trojan Horse-Sulfamidase Fusion Protein in the Mucopolysaccharidosis Type IIIA Mouse
Reduction in Brain Heparan Sulfate with Systemic Administration of an IgG Trojan Horse-Sulfamidase Fusion Protein in the Mucopolysaccharidosis Type IIIA Mouse
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DOI：
10.1021/acs.molpharmaceut.7b00958
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发表时间：
2018-02-01
影响因子：
4.9
通讯作者：
Pardridge, William M.
中科院分区：
文献类型：
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作者：
Boado, Ruben J.;Lu, Jeff Zhiqiang;Pardridge, William M.
粘多糖沉积症IIIA型（MPSIIIA），也称为Sanfilippo A综合征，是一种遗传性神经退行性疾病，由溶酶体酶N-磺基葡糖胺磺基水解酶（SGSH）（也称为磺酰胺酶）突变引起。SGSH酶（唯一的哺乳动物乙酰肝素N-硫酸酯酶）中的突变引起包含硫酸乙酰肝素（HS）糖胺聚糖（GAGS）的脑细胞中溶酶体包涵体的积累。用静脉内重组GSH治疗MPSIIIA是不可能的，因为这种大分子不能穿过血脑屏障（BBB）。在本研究中，通过将这种酶重新设计为IgG-SGSH融合蛋白，使SGSH能够穿透BBB，其中IgG结构域是针对小鼠转铁蛋白受体（TfR）的嵌合单克隆抗体（mAb），命名为cTfRMAb。融合蛋白的IgG结构域充当分子特洛伊木马以经由内源性BBB TfR上的转运将酶递送到脑中。cTfRMAb-SGSH融合蛋白与小鼠TfR结合。具有高亲和力，ED 50 = 0.74 +/- 0.07 nM，并保留了高GSH酶活性，10043 +/- 1003单位/mg蛋白，这与重组人GSH相当。从2周龄开始，每周三次腹膜内注射媒介物、单独的5 mg/kg的cTfRMAb或5 mg/kg的cTfRMAb-GSH融合蛋白，对不含GSH酶的雄性和雌性MPSIIIA小鼠治疗6周，并在最后一次注射后1周实施安乐死。通过液相色谱-质谱法测定，MPSIIIA小鼠的脑和肝HS分别升高了30倍和36倍。用cTfRMAb-SGSH融合蛋白治疗小鼠，使脑和肝脏HS分别减少70%和85%。在雄性小鼠中，脑HS的减少与运动活动的旋转棒测试的潜伏期增加28%相关。小鼠未表现出注射相关反应，仅观察到低滴度的研究结束抗药抗体应答。总之，在MPSIIIA的鼠模型中，脑病理性GAG的实质性减少是通过长期全身施用IgG-GSH融合蛋白产生的，所述融合蛋白被工程化以经由受体介导的转运穿透BBB。
Mucopolysaccharidosis Type IIIA (MPSIIIA), also known as Sanfilippo A syndrome, is an inherited neurodegenerative disease caused by mutations in the lysosomal enzyme, N-sulfoglucosamine sulfohydrolase (SGSH), also known as sulfamidase. Mutations in the SGSH enzyme, the only mammalian heparan N-sulfatase, cause accumulation of lysosomal inclusion bodies in brain cells comprising heparan sulfate (HS) glycosamino-glycans (GAGS). Treatment of MPSIIIA with intravenous recombinant SGSH is not possible because this large molecule does not cross the blood-brain barrier (BBB). BBB penetration by SGSH was enabled in the present study by re-engineering this enzyme as an IgG-SGSH fusion protein, where the IgG domain is a chimeric monoclonal antibody (mAb) against the mouse transferrin receptor (TfR), designated the cTfRMAb. The IgG domain of the fusion protein acts as a molecular Trojan horse to deliver the enzyme into brain via transport on the endogenous BBB TfR. The cTfRMAb-SGSH fusion protein bound to the mouse TfR. with high affinity, ED50 = 0.74 +/- 0.07 nM, and retained high SGSH enzyme activity, 10 043 +/- 1003 units/mg protein, which is comparable to recombinant human SGSH. Male and female MPSIIIA mice, null for the SGSH enzyme, were treated for 6 weeks with thrice-weekly intraperitoneal injections of vehicle, 5 mg/kg of the cTfRMAb alone, or 5 mg/kg of the cTfRMAb-SGSH fusion protein, starting at the age of 2 weeks, and were euthanized 1 week after the last injection. Brain and liver HS, as determined by liquid chromatography-mass spectrometry, were elevated 30-fold and 36-fold, respectively, in the MPSIIIA mouse. Treatment of the mice with the cTfRMAb-SGSH fusion protein caused a 70% and 85% reduction in brain and liver HS, respectively. The reduction in brain HS was associated with a 28% increase in latency on the rotarod test of motor activity in male mice. The mice exhibited no injection related reactions, and only a low titer end of study antidrug antibody response was observed. In conclusion, substantial reductions in brain pathologic GAGs in a murine model of MPSIIIA are produced by chronic systemic administration of an IgG-SGSH fusion protein engineered to penetrate the BBB via receptor-mediated transport.