TSP2-8和CUB1+2片段对血管性血友病因子裂解酶分泌方向的影响

本研究旨在探讨羧基端TSP2-8和CUB1+2片段是否决定血管性血友病因子裂解酶(ADAMTS13)合成后细胞内运输的方向,以了解金属蛋白酶ADAMTS13羧基端结构与功能的关系。利用脂质体转染技术将重组质粒pcDNA3.1-ADAMTS13及pcDNA3.1-delTSP2-8CUB1+2ADAMTS13分别转染犬肾上皮极性细胞MDCK,筛选出阳性细胞克隆后传代铺到中间有特殊分子筛膜的双池培养皿内培养,待细胞生长到无空隙后收集上、下池培养液;通过Western blot检测上、下池培养液中ADAMTS13蛋白表达水平,以对比分析ADAMTS13蛋白在极性细胞内的分泌方向。结果表明,稳定表达野生型ADAMTS13的MDCK细胞组,在分子筛膜的上池培养液中检测到ADAMTS13蛋白,而表达缺失TSP2-8CUB1+2区域ADAMTS13的细胞组,在分子膜的上、下池培养液中均检测到ADAMTS13重组蛋白。结论:金属蛋白酶ADAMTS13的分泌是有极性的,且羧基端TSP2-8和CUB1+2结构域与ADAMTS13合成后细胞内的运输方向密切相关。     

无流体剪切力条件下ADAMTS13裂解内皮细胞上特大血管性血友病因子的研究

目的：研究血管性血友病因子裂解酶（ADAMTS13）在无流体剪切力下裂解内皮细胞上特大血管性血友病因子（ULVWF）的分子机制,为探明血栓性血小板减少性紫癜（TTP）和其他血栓性疾病的发病机理提供理论依据。方法：通过免疫荧光显微镜观察ADAMTS13在无流体剪切力下裂解内皮细胞表面上ULVWF的情况,采用ELISA测定不同条件下培养基中VWF抗原量的变化。ELISA和Western blot分别测定有无流体剪切力或凝血因子VIII(FVIII)条件培养基中的VWF和蛋白水解片段的数量。多聚体分析评估ADAMTS13裂解内皮细胞上ULVWF的情况。将组胺刺激的人脐静脉内皮细胞（HUVEC）与ADAMTS13和各种N-和C-末端截断的突变体一起孵育,通过免疫荧光显微镜观察与细胞保持结合的ULVWF,ELISA测定内皮细胞释放出的ULVWF,确定降解内皮细胞上ULVWF所需的ADAMTS13结构域。结果：在无流体剪切力下,重组ADAMTS13和血浆ADAMTS13迅速降解了内皮细胞表面上新形成的ULVWF。ULVWF的蛋白水解过程依赖于培养时间、ADAMTS13浓度和剪切力。ADAMTS13...     

抗ADAMTS13单克隆抗体杂交瘤细胞株的建立

目的:建立分泌抗ADAMTS13单克隆抗体的杂交瘤细胞株,制备针对ADAMTS13不同结构域的单克隆抗体。方法:利用真核表达的重组血浆金属蛋白酶ADAMTS13截短型蛋白(ADAMTS13-T7)纯品免疫BALB/c小鼠。用ELISA方法测定免疫小鼠与ADAMTS13-T7蛋白的抗血清效价。取小鼠脾脏,制成单细胞悬液与SP2/0骨髓瘤细胞以10∶1的比例混合,进行细胞的融合,并将杂交瘤细胞稀释培养。2周后选生长良好的克隆孔检测,阳性克隆孔扩大培养并再次检测。结果:获得真核表达截短型血管性血友病因子裂解蛋白酶ADAMTS13-T7蛋白纯品。利用真核表达的截短型ADAMTS13-T7蛋白免疫BALB/c雌性小鼠,ELISA检测免疫后抗血清效价约为1∶20 000。利用杂交瘤技术通过融合,获得多株分泌抗重组ADAM TS13抗体的杂交瘤单克隆细胞株。将其中的30株转入液氮中冻存,以备进一步分选及功能研究。结论:融合获得多株分泌抗重组ADAMTS13抗体的杂交瘤单克隆细胞株,为进一步筛选出具有一定功能活性的单克隆抗体及研究ADAMTS13结构和功能提供更多的有力工具。     

血管性血友病因子裂解酶CUB区的稳定表达及其鉴定

目的 该研究旨在得到血管性血友病因子裂解酶ADAMTS13中重组的CUB区蛋白,进一步研究其生物功能.方法 利用脂质体将编码CUB区序列的重组质粒pSecTag-CUB转染Hela细胞.用潮霉素（hygromycin-B）筛选得到阳性克隆细胞株,并扩大培养,收集上清.利用Ni-NTA琼脂糖柱,梯度咪唑淋洗法纯化蛋白,SDS-PAGE和Western blotting鉴定纯化产品纯度和免疫学活性.结果 成功获得一株能恒定分泌重组CUB区蛋白的细胞株CUB-7,每1 L培养上清可纯化剑6.0mg重组蛋白.Western blotting结果显示,6×His抗体能与重组蛋白在41kD处显单一条带.结论 重组蛋白具有较好的免疫原活性和纯度,为进一步研究CUB区在ADAMTS13中的作用机理和运用奠定了良好的基础.     

血管性血友病因子裂解酶CysR结构域生物学功能的研究

目的:研究血管性血友病因子裂解酶(ADAMTS13)富含半胱氨酸(CysR)结构域在血管性血友病因子(vWF)裂解中的生物学功能,为探明血栓性血小板减少性紫癜(TTP)的发病机制提供实验证据.方法:利用点突变技术对ADAMTS13 CysR结构域中的EDGTLS氨基酸残基进行基因突变,制备质粒,表达并提纯蛋白.1％Se...     

血管性血友病因子vWF73和vWF114片段的表达及其在ADAMTS13活性测定中的应用

目的 构建血管性血友病因子(vWF)A2区片段vWF73和vWF114的表达质粒,在大肠杆菌中表达两种谷胱甘肽S转移酶(GST)融合蛋白,并探讨两种蛋白作为底物在测定ADAMTS13活性中的应用价值.方法 应用PCR的方法扩增vWF A2区内vWF73和vWF114的相应DNA片段,分别克隆至GST融合表达载体pGEX-6P-1进行诱导表达,Ni-NTA琼脂糖柱纯化可溶性蛋白部分.以Western blot法榆测正常人血浆、血栓性血小板减少性紫癜(TTP)患者血浆和重组ADAMTS13(rADAMTS13)水解两种重组vWF A2区片段的情况,并以此为底物用抗GST和抗His两种抗体建立酶联免疫吸附试验(ELISA)法测定血浆ADAMqS13活性的新方法.结果 成功表达和纯化了ADAMTS13的两种可溶性小分子底物GST-vWF73-H和GST-vWF114-H,均能被rADAMTS13或正常人血浆有效地水解,而遗传性和特发性TTP患者血浆则无此作用.同时,以此为底物建立了测定ADAMTS13活性的ELISA方法.结论 采用原核表达系统成功得到了vWF A2区片段vWF73和vWF114两种GST融合蛋白,可作为底物用于ADAMTS13活性的测定.

Abstract：

Objective To construct the expression vectors of vWF73 and vWF114 fragments of von Willebrand factor (vWF) A2 domain, and to express glutathione S-transferase (GST) fusion proteins in E.coli, and to explore their values in measuring ADAMTS13 activity as substrates. Methods The DNA fragments encoding vWF73 and vWF114 were generated using PCR and separately cloned into pGEX-6P-1 , a Schistosoma japonicum GST fusion expression vector. The expression of GST-vWF73-H and GST-vWF114-H was induced in liquid culture, followed by purification with Ni-NTA agarose column. The cleavage of two GST fusion proteins by recombinant ADAMTS13 ( rADAMTS13) or plasma from normal individuals and thrombotic thrombocytopenic purpura (TTP) patients were identified by Western blot. Based on an enzyme-linked immunosorbent assay ( ELISA) with anti-GST and anti-His monoclonal antibodies, GST-vWF73-H and GSTvWF114-H were used to measure plasma ADAMTS13 activity as substrates. Results Two small molecular substrates of ADAMTS13, GST-vWF73-H and GST-vWF114-H, are expressed and purified,which could be specifically cleaved by rADAMTS13 or plasma from healthy individuals, but not by plasma from congenital or idiopathic TTP patients. An ELISA assay was established to detect plasma ADAMTS13 activity using GSTvWF73-H and GST-vWF114-H as substrates. Conclusions Two GST fusion proteins in vWF A2 domain,vWF73 and vWF114, were expressed effectively using a prokaryotic expression system and could be used to detect ADAMTS13 activity as substrates.     

A1500E突变对血管性血友病因子的ADAMTS13依赖性水解的影响

目的 研究血管性血友病因子(VWF) A1500E突变体对金属蛋白酶ADAMTS13敏感性的改变,为VWF-A1500E突变导致2A型血管性血友病(VWD)的发病机制提供直接依据.方法 将野生型VWF质粒和A1500E突变体VWF质粒分别瞬时转染HeLa细胞,收集并浓缩培养上清,分别用重组人ADAMTS13( rADAMTS13)进行水解,然后通过十二烷基硫酸钠-琼脂糖凝胶电泳进行VWF多聚体分析,观察与野生型VWF相比,A1500E突变体VWF对ADAMTS13的敏感性有无改变.结果 体外表达研究结果显示WT-VWF和A1500E突变体VWF的表达上清中VWF:Ag的平均含量分别为1.10 U/ml和0.78 U/ml,突变体细胞裂解液中的VWF:Ag表达量为野生型的90.6％,两者差异均无统计学意义(P＞0.05).VWF多聚体电泳显示突变体VWF与WT-VWF的多聚体分布亦无明显差别.在无尿素和盐酸胍等变性剂的静态条件下,rADAMTS13即可对A1500E突变体VWF进行有效地水解,VWF多聚体分析显示大中分子量VWF多聚体明显减少和小分子量VWF多聚体明显增多;相反,野生型VWF在非变性条件下则无被rADAMTS13水解的证据.结论 A1500E突变导致突变体VWF对ADAMTS13的敏感性异常性增高,符合第二组2A型VWD的突变特点.     

血管性血友病因子裂解酶(ADAMTS13)单克隆抗体的鉴定以及生物学功能的研究

目的:构建并鉴定血管血友病因子裂解酶(ADAMTS13)单克隆抗体,并研究其生物学功能。方法:利用真核表达的重组血浆金属蛋白酶ADAMTS13截断型蛋白(ADAMTS13-T7)纯品免疫BALB/c小鼠,经标准单克隆抗体技术制备单克隆抗体。用ELISA方法鉴定单克隆抗体的特异性;应用免疫印迹技术确定单克隆抗体与全长ADAMTS13的识别能力;观察单克隆抗体对ADAMTS13水解v WF的影响。结果:最终获得6株抗ADAMTS13的单克隆抗体,克隆号分别为1G11、2F11、6G3、9E1、10A8、10B4。经ELISA鉴定,纯化后的单克隆抗体1G11和2F11的效价最高,与截断型ADAMTS13-T7蛋白结合能力比较,明显高于全长ADAMTS13蛋白。Western blotting结果显示,6个单克隆抗体都能与全长ADAMTS13结合,其中1G11和2F11条带最亮。功能实验表明,在变性条件下1G11和2F11能够明显抑制ADAMTS13水解v WF,并随着单克隆抗体浓度的增加而抑制作用增强。结论:成功获得针对ADAMTS13的单克隆抗体,其中两株为抑制性功能抗体。     

影响获得性血栓性血小板减少性紫癜首次缓解期内复发的相关指标研究

目的 探讨血管性血友病因子裂解蛋白酶(ADAMTS) 13活性和抗ADAMTS13抗体表达水平,与获得性血栓性血小板减少性紫癜(TTP)于首次缓解期内复发的关系.方法 选择2008年3月至2014年6月于陕西延安大学附属医院和陕西省渭南市富平县医院诊治的37例获得性TTP患者为研究对象,按照其在首次缓解随访期内是否复发,分为研究组(n=15)和对照组(n=22).分别采用残余胶原结合试验、ELISA、免疫印迹等方法,检测两组患者的ADAMTS13活性,ADAMTS13抗原水平,抗ADAMTS13抗体,ADAMTS13抑制物,血管性血友病因子(vWF)抗原和超大分子量vWF(ULVWF)多聚体等指标,并且进行统计学分析;采用多因素非条件logistic回归分析法,评估获得性TTP患者于首次缓解期内复发的独立影响因素.本研究遵循的程序符合病例收集医院人体试验委员会所制定的伦理学标准,得到该伦理会批准,分组征得受试对象本人的知情同意,并与之签订临床研究知情同意书.结果 ①研究组患者的中位ADAMTS13活性为11％(7％～124％),低于对照组的53％(7％～151％),差异有统计学意义(u=4.018,P＜0.05).研究组与对照组患者的ADAMTS13活性显著降低率分别为53.3％(8/15)和22.7％(5/22),二者比较,差异有统计学意义(P=0.049).②37例获得性TTP患者的血浆ADAMTS13活性和ADAMTS13抗原水平呈正相关关系(rs=0.810,P=0.001).研究组患者的中位ADAMTS13抗原水平为33％(3％～99％),低于对照组的59％(3％～128％),差异有统计学意义(u=4.121,P＜0.05).研究组与对照组ADAMTS13抗原水平显著降低率分别为13.3％(2/15)和9.1％(2/22),二者比较,差异有统计学意义(P=0.008).③研究组患者的抗ADAMTS13抗体检出率为66.7％(10/15),高于对照组的36.4％(8/22),差异有统计学意义(P=0.007).④研究组患者中抗ADAMTS13抑制物检出率为46.7％ (7/15),高于对照组患者的18.2％ (4/22),差异有统计学意义(P=0.011).⑤研究组与对照组患者ULVWF多聚体检出率分别为20.0％(3/15)和13.6％(3/22),二者比较,差异有统计学意义(P=0.042).⑥多因素非条件logistic回归分析结果显示,获得性TTP患者于首次缓解期内复发的独立危险因素包括ADAMTS13活性显著降低(OR=2.95,95％ CI:1.13～6.96,P＜0.05),检出抗ADAMTS13抗体(OR=3.31,95％CI:1.08～8.19,P＜0.05),检出抗ADAMTS13抑制物(OR=3.24,95 ％CI:1.24～9.03,P＜0.05).结论 获得性TTP患者在首次缓解期内,ADAMTS13活性水平显著降低,存在抗ADAMTS13抗体及抗ADAMTS13抑制物,会显著增加疾病复发风险,可以考虑将其作为预测获得性TTP患者于首次缓解期内复发的重要指标.     

p53结合蛋白对细胞周期阻滞与细胞凋亡调控的研究进展

p53基因是人体内重要的肿瘤抑制基因,位于人类染色体17p13．1,含有11个外显子,编码的野生型p53蛋白由393个氨基酸残基组成,包含N．末端的转录激活结构域、生长抑制结构域、序列特异的DNA结合结构域（DNAbindingdomain,DBD）、核定位信号（nuclearlocalizationsignal,NLS）、四聚体化结构域和c．末端非专一DNA调节结构域。p53在监视细胞基因组损伤及维持基因组的稳定性中发挥重要作用。当紫外线、电离辐射、氧化应激及癌基因表达等刺激因素引起细胞内DNA损伤时,p53蛋白迅速聚集活化,并作为序列特异性转录因子对一系列靶基因进行调控。     

The distal carboxyterminal domains of murine ADAMTS13 influence proteolysis of platelet‐decorated VWF strings in vivo

Summary. Background: The multidomain metalloprotease ADAMTS13 regulates the size of von Willebrand factor (VWF) multimers upon their release from endothelial cells. How the different domains in ADAMTS13 control VWF proteolysis in vivo remains largely unidentified. Methods: Seven C‐terminally truncated murine ADAMTS13 (mADAMTS13) mutants were constructed and characterized in vitro. Their ability to cleave VWF strings in vivo was studied in the ADAMTS13^?/? mouse. Results: Murine MDTCS (devoid of T2‐8 and CUB domains) retained full enzyme activity in vitro towards FRETS‐VWF73 and the C‐terminal T6‐8 (del(T6‐CUB)) and CUB domains (delCUB) are dispensable under these assay conditions. In addition, mADAMTS13 fragments without the spacer domain (MDT and M) had reduced catalytic efficiencies. Our results hence indicate that similar domains in murine and human ADAMTS13 are required for activity in vitro, supporting the use of mouse models to study ADAMTS13 function in vivo. Interestingly, using intravital microscopy we show that removal of the CUB domains abolishes proteolysis of platelet‐decorated VWF strings in vivo. In addition, whereas MDTCS is fully active in vivo, partial (del(T6‐CUB)) or complete (delCUB) addition of the T2‐8 domains gradually attenuates its activity. Conclusions: Our data demonstrate that the ADAMTS13 CUB and T2‐8 domains influence proteolysis of platelet‐decorated VWF strings in vivo.     

Multiple B-cell clones producing antibodies directed to the spacer and disintegrin/thrombospondin type-1 repeat 1 (TSP1) of ADAMTS13 in a patient with acquired thrombotic thrombocytopenic purpura

BACKGROUND: The cysteine-rich/spacer domains of ADAMTS13 contain a major binding site for antibodies in patients with acquired thrombotic thrombocytopenic purpura (TTP). OBJECTIVE: To study the heterogeneity of the antibody response towards these domains an immunoglobulin V-gene phage-display library was constructed to isolate monoclonal anti-ADAMTS13 antibodies from the immunoglobulin repertoire of a patient with acquired TTP. METHODS: Combined variable heavy chain (VH) and variable light chain (VL) segments, expressed as single-chain Fv fragments (scFv), were selected for binding to an ADAMTS13 fragment consisting of the disintegrin/thrombospondin type-1 repeat 1 (TSP1)/cysteine-rich/spacer domains. RESULTS: Seven different scFv antibody clones were identified that were assigned to four groups based on their homology to VH germline gene segments. Epitope-mapping revealed that scFv I-9 (VH1-69), I-26 (VH1-02), and I-41 (VH3-09) bind to an overlapping binding site in the ADAMTS13 spacer domain, whereas scFv I-16 (VH3-07) binds to the disintegrin/TSP1 domains. The affinity of scFv for the disintegrin/TSP1/cysteine-rich/spacer domain was determined by surface plasmon resonance analysis and the dissociation constants ranged from 3 to 254 nM. The scFv partially inhibited ADAMTS13 activity. However, full-length IgG prepared from the variable domains of scFv I-9 inhibited ADAMTS13 activity more profoundly. Plasma of six patients with acquired TTP competed for binding of scFv I-9 to ADAMTS13. CONCLUSION: Our data indicate that multiple B-cell clones producing antibodies directed against the spacer domain are present in the patient analyzed in this study. Our findings also suggest that antibodies with a similar epitope specificity as scFv I-9 are present in plasma of other patients with acquired TTP.     

Humoral immune response to ADAMTS13 in acquired thrombotic thrombocytopenic purpura

Summary. The apparently spontaneous development of autoantibodies to ADAMTS13 in previously healthy individuals is a major cause of thrombotic thrombocytopenic purpura (TTP). Epitope mapping studies have shown that in most patients antibodies directed towards the spacer domain of ADAMTS13 are present. A single antigenic surface comprising Arg⁶⁶⁰, Tyr⁶⁶¹ and Tyr⁶⁶⁵ that contributes to the productive binding of ADAMTS13 to unfolded von Willebrand factor is targeted by anti‐spacer domain antibodies. Antibodies directed to the carboxyl‐terminal CUB1–2 and TSP2–8 domains have also been observed in the plasma of patients with acquired TTP. As yet it has not been established whether this class of antibodies modulates ADAMTS13 activity. Inspection of the primary sequence of human monoclonal anti‐ADAMTS13 antibodies suggests that the variable heavy chain germline gene segment VH1–69 is frequently incorporated. We suggest a model in which ‘shape complementarity’ between the spacer domain and residues encoded by the VH1–69 gene segment explain the preferential use of this variable heavy chain gene segment. Finally, a model is presented for the development of anti‐ADAMTS13 antibodies in previously healthy individuals that incorporates the recent identification of HLA DRB1*11 as a risk factor for acquired TTP.     

Novel monoclonal antibody-based enzyme immunoassay for determining plasma levels of ADAMTS13 activity

BACKGROUND: ADAMTS13 specifically cleaves unusually large von Willebrand factor (VWF) multimers, which induce platelet thrombi formation under high shear stress. ADAMTS13 activity is deficient in patients with thrombotic thrombocytopenic purpura (TTP). The determination of plasma levels of ADAMTS13 activity is a prerequisite for a differential diagnosis of thrombotic microangiopathies. Here, a unique and highly sensitive enzyme immunoassay (EIA) of ADAMTS13 activity is described. STUDY DESIGN AND METHODS: ADAMTS13 hydrolyzes the peptide bond between Y1605 and M1606 of VWF. In this assay, a recombinant fusion protein (GST-VWF73-His) is used as a substrate. A panel of mouse monoclonal antibodies (MoAbs) that specifically recognizes Y1605, which is the C-terminal edge residue of the VWF-A2 domain and is generated by the enzymatic cleavage, has been produced. These antibodies were prepared with a synthetic decapeptide, termed N-10 (1596-DREQAPNLVY-1605), as the immunogen. Twenty-six clones specific to N10 were obtained, and one anti-N10 MoAb was used in this study. RESULTS: With horseradish peroxidase-conjugated anti-N10 MoAb, a standard enzyme assay was established. This assay was highly sensitive, and the detection limit was 0.5 percent of the normal. Further, an inhibitor of ADAMTS13 was measured to a level of 0.1 Bethesda units per mL. ADAMTS13 activity was measured in 20 patients with Upshaw-Schulman syndrome, a congenital TTP, and 61 acquired TTP patients. The activity measured by this assay and by the classic VWF multimer assay showed high correlation. CONCLUSION: A convenient and highly sensitive EIA for ADAMTS13 activity has been established. This assay can be introduced for routine laboratory work in transfusion medicine.     

Ten candidate ADAMTS13 mutations in six French families with congenital thrombotic thrombocytopenic purpura (Upshaw–Schulman syndrome)

Summary.  ADAMTS13, the specific von Willebrand factor (VWF)-cleaving metalloprotease, prevents the spontaneous formation of platelet thrombi in the microcirculation by degrading the highly adhesive ultralarge VWF multimers into smaller forms. ADAMTS13 severe enzymatic deficiency and mutations have been described in the congenital thrombotic thrombocytopenic purpura (TTP or Upshaw–Schulman syndrome), a rare and severe disease related to multivisceral microvascular thrombosis. We investigated six French families with congenital TTP for ADAMTS13 enzymatic activity and gene mutations. Six probands with congenital TTP and their family were tested for ADAMTS13 activity in plasma using a two-site immunoradiometric assay and for ADAMTS13 gene mutations using polymerase chain reaction and sequencing. ADAMTS13 activity was severely deficient (< 5%) in the six probands and one mildly symptomatic sibling but normal (> 50%) in all the parents and the asymptomatic siblings. Ten novel candidate ADAMTS13 mutations were identified in all families, showing either a compound heterozygous or a homozygous status in all probands plus the previous sibling and a heterozygous status in the parents. The mutations were spread all over the gene, involving the metalloprotease domain (I79M, S203P, R268P), the disintegrin domain (29 bp deletion in intron/exon 8), the cystein-rich domain (acceptor splice exon 12, R507Q), the spacer domain (A596V), the 3rd TSP1 repeat (C758R), the 5th TSP1 repeat (C908S) and the 8th TSP1 repeat (R1096stop). This study emphasizes the role of ADAMTS13 mutations in the pathogenesis of congenital TTP and suggests that several structural domains of this metalloprotease are involved in both its biogenesis and its substrate recognition process.     

N-acetylcysteine reduces the size and activity of von Willebrand factor in human plasma and mice

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening disease characterized by systemic microvascular thrombosis caused by adhesion of platelets to ultra-large vWF (ULVWF) multimers. These multimers accumulate because of a deficiency of the processing enzyme ADAMTS13. vWF protein forms long multimers from homodimers that first form through C-terminal disulfide bonds and then join through their N termini by further disulfide bonding. N-acetylcysteine (NAC) is an FDA-approved drug that has long been used to treat chronic obstructive lung disease and acetaminophen toxicity and is known to function in the former disorder by reducing mucin multimers. Here, we examined whether NAC could reduce vWF multimers, which polymerize in a manner similar to mucins. In vitro, NAC reduced soluble plasma-type vWF multimers in a concentration-dependent manner and rapidly degraded ULVWF multimer strings extruded from activated ECs. The effect was preceded by reduction of the intrachain disulfide bond encompassing the platelet-binding A1 domain. NAC also inhibited vWF-dependent platelet aggregation and collagen binding. Injection of NAC into ADAMTS13-deficient mice led to the rapid resolution of thrombi produced by ionophore treatment of the mesenteric venules and reduced plasma vWF multimers. These results suggest that NAC may be a rapid and effective treatment for patients with TTP.     

Targeting von Willebrand factor and platelet glycoprotein Ib receptor

Atherothrombotic events, such as acute coronary syndrome or stroke, are the result of platelet activation. Von Willebrand factor (vWF), a multimeric glycoprotein, plays a key role in aggregation of platelets, especially under high-shear conditions. Acting as bridging element or ligand between damaged endothelial sites and the glycoprotein Ib (GPIb) receptor on platelets, vWF is responsible for platelet adhesion and aggregation. This vWF activation and further platelet aggregation mainly occurs under high shear stress present in small arterioles or during deficiency of the vWF-cleaving protease ADAMTS13. There are several substances targeting vWF itself or its binding receptor GPIb on platelets. Two antibodies are directed against vWF: AJW200, an IgG4 humanized monoclonal antibody, and 82D6A3, a monoclonal antibody of the collagen-binding A-3 domain of vWF. ALX-0081 and ALX-0681 are bivalent humanized nanobodies targeting the GPIb binding site of vWF. Aptamers are oligonucleotides with drug-like properties that share some of the attributes of monoclonal antibodies. ARC1779 is a second-generation, nuclease-resistant aptamer, binding to the activated vWF A1 domain and ARC15105 is a chemically advanced follower with an assumed higher affinity to vWF. Antibodies targeting GPIbα are h6B4-Fab, a murine monoclonal antibody; GPG-290, a recombinant, chimeric protein containing the amino-terminal 290 amino acids of GPIbα linked to human IgG1 Fc; and the monoclonal antibody SZ2. There are a number of promising preclinical results and development of some agents (AJW 200, ARC1779 and ALX-0081) has already reached Phase II trials.     

Targeting von Willebrand factor and platelet glycoprotein Ib receptor

Atherothrombotic events, such as acute coronary syndrome or stroke, are the result of platelet activation. Von Willebrand factor (vWF), a multimeric glycoprotein, plays a key role in aggregation of platelets, especially under high-shear conditions. Acting as bridging element or ligand between damaged endothelial sites and the glycoprotein Ib (GPIb) receptor on platelets, vWF is responsible for platelet adhesion and aggregation. This vWF activation and further platelet aggregation mainly occurs under high shear stress present in small arterioles or during deficiency of the vWF-cleaving protease ADAMTS13. There are several substances targeting vWF itself or its binding receptor GPIb on platelets. Two antibodies are directed against vWF: AJW200, an IgG4 humanized monoclonal antibody, and 82D6A3, a monoclonal antibody of the collagen-binding A-3 domain of vWF. ALX-0081 and ALX-0681 are bivalent humanized nanobodies targeting the GPIb binding site of vWF. Aptamers are oligonucleotides with drug-like properties that share some of the attributes of monoclonal antibodies. ARC1779 is a second-generation, nuclease-resistant aptamer, binding to the activated vWF A1 domain and ARC15105 is a chemically advanced follower with an assumed higher affinity to vWF. Antibodies targeting GPIbα are h6B4-Fab, a murine monoclonal antibody; GPG-290, a recombinant, chimeric protein containing the amino-terminal 290 amino acids of GPIbα linked to human IgG1 Fc; and the monoclonal antibody SZ2. There are a number of promising preclinical results and development of some agents (AJW 200, ARC1779 and ALX-0081) has already reached Phase II trials.