[Refractory thrombotic thrombocytopenic purpura complicated with multiple cerebral infarction].

Neuropsychiatric symptoms comprise one of the five classic symptoms of autoimmune thrombotic thrombocytopenic purpura (aTTP). Although aTTP is typically transient, it is sometimes complicated by cerebral infarction with residual disability. This report presents the case of an 87-year-old man previously admitted to a different hospital with fever and transient consciousness loss. After receiving platelet transfusion with diagnosis of Evans syndrome, he was transferred to our hospital with worsening consciousness disturbance. He was subsequently diagnosed with aTTP with a PLASMIC score of 6 points, ADAMTS13 activity of less than 0.5%, and its inhibitor of 7.4 BU/ml. Platelet count and consciousness were rapidly improved with plasmapheresis and steroids, but motor aphasia emerged. MRI showed multiple cerebral infarctions, including a large infarction in the left frontal lobe. Thus, unfractionated heparin was administered. When his platelet count dropped once again on the 20th day, rituximab was added. The treatment eventually proved to be successful, and his aTTP remained in remission one year after the onset. Treatment for cerebral infarctions was switched to DOAC, and rehabilitation was continued. However, his ADL has not yet recovered. Advances in aTTP treatment have cured many similar cases. Thus, rituximab is now considered a treatment option for refractory cases. However, ischemic organ damage in acute phase and sequelae are observed. Therefore, early diagnosis and novel therapy are required.

Characteristics Behaviors of Coagulation and Fibrinolysis Markers in Acquired Thrombotic Thrombocytopenic Purpura.

INTRODUCTIONS: Patients with acquired thrombotic thrombocytopenic purpura (TTP) show no severe abnormalities in coagulation or fibrinolysis. However, the exact extent of the abnormalities is unclear. MATERIALS AND METHODS: This study analyzed 138 patients with acquired TTP and 46 patients with septic disseminated intravascular coagulation (DIC) who were included in a Japanese registry. Complete blood cell counts and 8 coagulation or fibrinolysis parameters were compared between the 2 groups. RESULTS: Platelet counts in the acquired TTP group were significantly lower than those in the septic DIC group (P < .001). The international normalized ratio of prothrombin time and the activated partial thromboplastin time in the septic DIC group were significantly higher and longer, respectively, than those in the acquired TTP group (P < .01). The antithrombin (AT) values were significantly lower in the septic DIC group than in the acquired TTP group (P < .001), the latter of which were almost normal. Although both groups revealed elevations of fibrinogen degradation product (FDP) and D-dimer, these levels were significantly higher in the septic DIC group than in the acquired TTP group (P < .001). Of 138 patients with acquired TTP, 25 (18.1%) were diagnosed with septic DIC by the diagnostic criteria of the Japanese Ministry Health, Labour and Welfare, and 78 (56.5%) by those of the Japanese Association of Acute Medicine. Receiver operating characteristic curve analysis showed that acquired TTP could be diagnosed based on severe thrombocytopenia (<20 × 109/L), normal AT level (>87%), and mildly elevated FDP (<23 µg/mL). CONCLUSIONS: Our results indicate that 3 routine laboratory tests could differentiate between acquired TTP and septic DIC.

Hemolysis and von Willebrand factor degradation in mechanical shuttle shear flow tester.

Chronic blood trauma caused by the shear stresses generated by mechanical circulatory support (MCS) systems is one of the major concerns to be considered during the development of ventricular assist devices. Large multimers with high-molecular-weight von Willebrand factor (VWF) are extended by the fluid forces in a shear flow and are cleaved by ADAMTS13. Since the mechanical revolving motions in artificial MCSs induce cleavage in large VWF multimers, nonsurgical bleeding associated with the MCS is likely to occur after mechanical hemodynamic support. In this study, the shear stress (~ 600 Pa) and exposure time related to hemolysis and VWF degradation were investigated using a newly designed mechanical shuttle shear flow tester. The device consisted of a pair of cylinders facing the test section of a small-sized pipe; both the cylinders were connected to composite mechanical heads with a sliding-sleeve structure for axial separation during the withdrawing motion. The influence of exposure time, in terms of the number of stress cycles, on hemolysis and VWF degradation was confirmed using fresh goat blood, and the differences in the rates of dissipation of the multimers were established. The plasma-free hemoglobin levels showed a logarithmic increase corresponding to the number of cycles, and the dissipation of large VWF multimers occurred within a few seconds under high shear stress flow conditions.

[Acquired von Willebrand syndrome].

Von Willebrand disease (VWD) is among the most common inherited bleeding disorders. Interestingly, acquired von Willebrand syndrome (AVWS) is diagnosed much less frequently, but can be identified in association with a substantial number of medical conditions and diseases, including lymphoproliferative (48%), cardiovascular (21%), myeloproliferative (15%), other neoplastic (5%), and autoimmune disorders (2%). Most recently, AVWS has been diagnosed in patients with aortic valve stenosis (AS, 79%) and continuous-flow left ventricular assist devices (LVAD, up to 100%).1) Immune mechanisms mediated reduction of VWF activityAutoantibodies to VWF have been identified in association with monoclonal gammopathies, lymphoid, neoplasms, and autoimmune diseases. Some autoantibodies have higher affinity to high molecular weight-VWF multimers (HMW-VWFMs); clearance of HMW-VWFMs leads to bleeding.2) Non-immune mechanisms induced reduction of VWF activityOne of the mechanisms is VWF adsorption onto malignant cells and paraproteins (i.e., as in multiple myeloma) and thereby removed from the blood circulation. VWF-linked proteolysis can be induced by shear stress. According to high levels of shear stress in AS and LVAD, HM-VWFMs are more susceptible to cleavage by ADAMTS13. We will find a large number of AVWS cases related to cardiovascular diseases.

[Successful management of acquired factor V deficiency developing shortly after induction of hemodialysis].

Autoimmune factor V deficiency (AiF5D) is caused by autoantibodies to coagulation factor V (FV); its clinical manifestations range from asymptomatic to fatal hemorrhage. Herein, we report the case of a 68-year-old man who was diagnosed with end-stage renal disease at the time of a femoral fracture and developed AiF5D after initiating hemodialysis. A wound infection that occurred after joint replacement was treated with antibiotics; however, it was poorly controlled. One month after the procedure, his coagulation time prolonged. The infection was improved by debridement and antibiotics; however, the coagulation time was not decreased and poor hemostasis at the shunt was still persistent. Because ELISA detected anti-FV-binding IgG with FV activity of <2.8% and FV inhibitor levels were 11.8 BU/ml, AiF5D was diagnosed. Oral prednisolone (PSL) was started. Dialysis was initially performed without anticoagulants, but blood clots were not found in the circuit. Anticoagulants were resumed when the coagulation time decreased. After achieving complete remission, PSL dose was tapered and finally discontinued. Few reports have described the management of AiF5D via dialysis. We consider that our report would be useful for the management of patients with similar manifestations.

Secretion of GLP-1 but not GIP is potently stimulated by luminal d-Allulose (d-Psicose) in rats.

Glucagon-like peptide 1 (GLP-1), an incretin gastrointestinal hormone, is secreted when stimulated by nutrients including metabolizable sugars such as glucose and fructose. d-Allulose (allulose), also known as d-psicose, is a C-3 isomer of d-fructose and a rare sugar with anti-diabetic or anti-obese effects in animal models. In the present study, we examined whether an oral administration of allulose could stimulate GLP-1 secretion in rats, and investigated the underlying mechanisms. Oral, but not intraperitoneal, administration of allulose (0.5-2.0 g/kg body weight) elevated plasma GLP-1 levels for more than 2 h in a dose-dependent manner. The effects of allulose on GLP-1 secretion were higher than that of dextrin, fructose, or glucose. In addition, oral allulose increased total and active GLP-1, but not glucose-dependent insulinotropic polypeptide (GIP), levels in the portal vein. In anesthetized rats equipped with a portal catheter, luminal (duodenum and ileum) administration of allulose increased portal GLP-1 levels, indicating the luminal effect of allulose. Allulose-induced GLP-1 secretion was abolished in the presence of xanthohumol (a glucose/fructose transport inhibitor), but not in the presence of inhibitors of the sodium-dependent glucose cotransporter 1 or the sweet taste receptor. These results demonstrate a potent and lasting effect of orally administered allulose on GLP-1 secretion in rats, without affecting GIP secretion. The potent and selective GLP-1-releasing effect of allulose holds promise for the prevention and treatment of glucose intolerance through promoting endogenous GLP-1 secretion.

Acquired thrombotic thrombocytopenic purpura with a smoldering clinical course.

Acquired thrombotic thrombocytopenic purpura (aTTP) is caused by a deficiency of ADAMTS13 activity due to neutralizing auto-autoantibodies (inhibitors) against ADAMTS13. Patients with aTTP show a rapid and fatal clinical course, unless an effective therapeutic intervention such as plasma exchange therapy (PEX) is performed. There is, however, a small population of patients who show a smoldering clinical course, for which no effective treatment strategy has yet been established. We herein report a 77-year-old man, who had repeated episodes of cerebral infarction and persistent thrombocytopenia over several months, but was not correctly diagnosed as having aTTP at a local hospital. However, sudden progression to an unconsciousness state together with thrombocytopenia prompted his physician to make a clinical diagnosis of aTTP, and the patient was then referred to our hospital, where the diagnosis of aTTP was confirmed by analyzing ADAMTS13. An improvement of his clinical signs was achieved with PEX and steroid therapy, but the latter had to be discontinued due to the development of grade 3 liver dysfunction. Despite discontinuation of steroid therapy, his clinical condition remained stable, but with a persistently low level of ADAMTS13 activity associated with the presence of low-titer inhibitors. Our experience may raise awareness of the diagnosis and treatment of aTTP with a smoldering clinical course.

Refractory thrombotic thrombocytopenic purpura achieving complete remission with rituximab treatment.

Some patients with thrombotic thrombocytopenic purpura (TTP) are refractory to standard treatment regimens comprised of plasma exchange (PEX) and steroids. This report describes a 40-year-old woman with refractory TTP who achieved complete remission (CR) in response to rituximab. She was referred to our institution from a rural hospital with purpura of the extremities, severe thrombocytopenia, anemia, and rapidly progressive disturbance of consciousness. TTP was diagnosed based on the clinical symptoms of TTP, low ADAMTS13 activity (<0.5%), and high ADAMTS13 inhibitor (4.4 BU/ml) titers. High-dose prednisolone was immediately administered and PEX was started. This approach was initially effective, but the thrombocytopenia and disturbance of consciousness worsened on the sixth day of treatment. We considered this patient to have refractory TTP and administered weekly rituximab. CR was achieved on day 20, and the disease status of this patient has remained stable over the long term. Our experience with this patient and five others who were similarly treated at our hospital over the past eight years indicates that rituximab is effective for refractory TTP.

Influenza-associated thrombotic microangiopathy with unbalanced von Willebrand factor and a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 levels in a heterozygous protein S-deficient boy.

Influenza infections often cause pneumonia, but there is limited information on thrombotic microangiopathy (TMA) in these circumstances. We report the case of an 11-year-old boy who developed TMA during the acute phase of H1N1 influenza. Plasma von Willebrand factor (VWF) was elevated, whereas a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) activity was mildly reduced in the absence of ADAMTS13-neutralizing autoantibody, resulting in low ratio of ADAMTS13 to VWF. The patient was treated intensively, including plasma exchange, and he recovered from the TMA. He developed pulmonary embolism (PE), however, after removal of the central venous catheter. The findings suggested that influenza-associated cytokines enhanced the release of unusually large VWF multimers from vascular endothelial cells and promoted the formation of platelet thrombi and TMA. Subsequent analysis further indicated the presence of familial protein S deficiency, and it seemed likely that the PE was more related to this heterozygous protein S defect.

[Acquired thrombotic thrombocytopenic purpura after vascular prosthesis implantation for impending rupture of an abdominal aortic aneurysm].

Acquired thrombotic thrombocytopenic purpura (TTP) is caused by autoantibodies against ADAMTS13. TTP patients run a rapidly fatal course unless immediate plasma exchange (PEX) is initiated upon diagnosis. Herein, we report a 72-year-old man with TTP, which developed after he underwent artificial blood vessel replacement surgery for an abdominal aneurysm with impending rupture. In the perioperative period, the patient received several platelet transfusions for severe thrombocytopenia (minimum platelet count: 0.6×10(4)/µl). Thereafter, he was admitted to our department for rapidly progressing coma with multiple cerebral infarctions, and was transferred to the ICU. Based on the tentative diagnosis of TTP, we immediately began PEX and steroid pulse therapy. The diagnosis was confirmed thereafter by markedly reduced ADAMTS13 activity (<0.5%) and his being positive for the ADAMTS13 inhibitor. We performed PEX for five consecutive days and administered high-dose prednisolone (PSL). On the second hospital day (HD), his platelet count rose along with improvement of his consciousness level. The ADAMTS13 inhibitor was not detected on the 10th HD. TTP did not relapse and his general condition improved despite tapering of PSL. In this case, by closely monitoring ADAMTS13-related parameters and minimizing the number of plasma exchanges, the patient was able to achieve a remission without the use of boosting inhibitors.

Mitral regurgitation is associated with similar loss of von Willebrand factor large multimers but lower frequency of anemia compared with aortic stenosis.

Background: Various cardiovascular diseases cause acquired von Willebrand syndrome (AVWS), which is characterized by a decrease in high-molecular-weight (large) von Willebrand factor (VWF) multimers. Mitral regurgitation (MR) has been reported as a cause of AVWS. However, much remains unclear about AVWS associated with MR. Objectives: To evaluate VWF multimers in MR patients and examine their impact on clinical characteristics. Methods: Moderate or severe MR patients (n = 84) were enrolled. VWF parameters such as the VWF large multimer index (VWF-LMI), a quantitative value that represents the amount of VWF large multimers, and clinical data were prospectively analyzed. Results: At baseline, the mean hemoglobin level was 12.9 ± 1.9 g/dL and 58 patients (69.0%) showed loss of VWF large multimers defined as VWF-LMI < 80%. VWF-LMI in patients with degenerative MR was lower than in those with functional MR. VWF-LMI appeared to be restored the day after mitral valve intervention, and the improvement was maintained 1 month after the intervention. Seven patients (8.3%) had a history of bleeding, 6 (7.1%) of whom had gastrointestinal bleeding. Gastrointestinal endoscopy was performed in 23 patients (27.4%) to investigate overt gastrointestinal bleeding, anemia, etc. Angiodysplasia was detected in 2 of the 23 patients (8.7%). Conclusion: Moderate or severe MR is frequently associated with loss of VWF large multimers, and degenerative MR may cause more severe loss compared with functional MR. Mitral valve intervention corrects the loss of VWF large multimers. Gastrointestinal bleeding may be relatively less frequent and hemoglobin level remains stable in MR patients.

von Willebrand factor Ristocetin co-factor activity to von Willebrand factor antigen level ratio for diagnosis of acquired von Willebrand syndrome caused by aortic stenosis.

Background: Severe aortic stenosis (AS) causes acquired von Willebrand syndrome by the excessive shear stress-dependent cleavage of high molecular weight multimers of von Willebrand factor (VWF). While the current standard diagnostic method is so-called VWF multimer analysis that is western blotting under nonreducing conditions, it remains unclear whether a ratio of VWF Ristocetin co-factor activity (VWF:RCo) to VWF antigen levels (VWF:Ag) of <0.7, which can be measured with an automated coagulation analyzer in clinical laboratories and is used for the diagnosis of hereditary von Willebrand disease. Objectives: To evaluated whether the VWF:RCo/VWF:Ag is useful for the diagnosis of AS-induced acquired von Willebrand syndrome. Methods: VWF:RCo and VWF:Ag were evaluated with the VWF large multimer index as a reference, which represents the percentage of a patient's VWF high molecular weight multimer ratio to that of standard plasma in the VWF multimer analysis. Results: We analyzed 382 patients with AS having transaortic valve maximal pressure gradients of >30 mmHg, 27 patients with peripheral artery disease, and 46 control patients free of cardiovascular disease with osteoarthritis, diabetes, and so on. We assumed a large multimer index of <80% as loss of VWF large multimers since 59.0% of patients with severe AS had the indices of <80%, while no control patients or patients with peripheral artery disease, except for 2 patients, exhibited the indices of <80%. The VWF:RCo/VWF:Ag ratios, measured using an automated blood coagulation analyzer, were correlated with the indices (rs = 0.470, P < .001). When the ratio of <0.7 was used as a cut-off point, the sensitivity and specificity to VWF large multimer indices of <80% were 0.437 and 0.826, respectively. Conclusion: VWF:RCo/VWF:Ag ratios of <0.7 may indicate loss of VWF large multimers with high specificity, but low sensitivity. VWF:RCo/VWF:Ag ratios in patients with AS having a ratio of <0.7 may be useful for monitoring the loss of VWF large multimers during their clinical courses.

ADAMTS13 unbound to larger von Willebrand factor multimers in cryosupernatant: implications for selection of plasma preparations for thrombotic thrombocytopenic purpura treatment.

BACKGROUND: Thrombotic thrombocytopenic purpura (TTP) is characterized by deficient ADAMTS13 activity. Treatment involves plasma exchange (PE). Both fresh-frozen plasma (FFP) and cryosupernatant (CSP) are used, but it remains to be determined which is more effective. STUDY DESIGN AND METHODS: To analyze the interaction between von Willebrand factor (VWF) and ADAMTS13, we used large-pore isoelectric focusing (IEF) analysis followed by detection with anti-ADAMTS13 monoclonal antibody. FFP, CSP, cryoprecipitate (CP), and purified ADAMTS13 were analyzed for their effects on high shear stress-induced platelet aggregation (H-SIPA). RESULTS: IEF analysis of normal plasma revealed three groups of ADAMTS13 bands with pI of 4.9 to 5.6, 5.8 to 6.7, and 7.0 or 7.5. Two band groups (pI 4.9-5.6 and 5.8-6.7) were found in plasma of a patient with Type 3 von Willebrand disease, in which VWF is absent, whereas no bands were found in plasma of a patient with congenital ADAMTS13 deficiency. Mixing these plasmas generated the bands at pI 7.0 or 7.5, representing the VWF-ADAMTS13 complex; these bands were absent in CSP. FFP and purified ADAMTS13 down regulated H-SIPA in a dose-dependent manner. However, CP did not inhibit H-SIPA in the initial phase, and the degree of inhibition at the endpoint was almost indistinguishable from those of the other two plasma products. CONCLUSION: Both plasma products (FFP and CSP) are effective for PE in TTP patients. However, CSP may be more favorable, because it has lower levels of VWF and almost normal ADAMTS13 activity, but lower levels of ADAMTS13 in complex with larger VWF multimers.

[Improvement in peripheral blood T cell subset imbalance in a house with an elimination system for various allergens].

We analyzed the change of peripheral blood T cell subsets after moving into a house with a Healthy Air system (HAS) elimination system for various allergens, e.g. pollens, house dusts, etc. The 20 subjects were divided into an allergic group (13 subjects) and control group (7 subjects). We measured complete blood counts (CBC), white blood cell differentiation (DIFF), CD4/CD8 ratio, Th1/Th2 ratio, and percentage of CD4+CD25+T-cells and regulatory T-cells in peripheral blood, and these data were compared before and 3 and 6 months after moving into the HAS house. There was no significant difference in CBC, DIFF, CD4/CD8 ratio, and Th1/Th2 ratio before and after the move. The mean levels and 95% confidence interval of CD4+CD25+T-cells in the allergic group were as follows: before, 16.66% (12.99-20.34%); at 3 months, 13.86% (10.49-17.22%); and at 6 months, 12.66% (9.28-16.05%), respectively. Those in the control group were as follows: before, 13.60% (5.27-21.93%); at 3 months, 12.51%(5.41-19.61%); and at 6 months, 11.77% (3.93-19.61%), respectively. CD4+CD25+T-cells were significantly decreased at 6 months after the move compared to before the move in the allergic group (p < 0.01). However, there was no significant difference between before and after the move in the control group. The mean levels of regulatory T-cells were not different between before and after the move in both groups. The mean level of CD4+CD25+T-cells in subjects that had improved allergic condition was significantly decreased at 6 months after the move compared to before the move (p < 0.05). These results suggest that decreases in allergens in the home environment may affect lymphocyte subsets.

Increased cleavage of von Willebrand factor by ADAMTS13 may contribute strongly to acquired von Willebrand syndrome development in patients with essential thrombocythemia.

BACKGROUND: Patients with essential thrombocythemia (ET) often experience bleeding associated with acquired von Willebrand syndrome (AVWS) when the platelet count is markedly increased. OBJECTIVE: We investigated whether von Willebrand factor (VWF) degradation is enhanced in patients with ET. METHODS: Seventy patients with ET underwent VWF multimer (VWFM) analysis and measurement of VWF-related parameters. We calculated the VWFM index, defined as the ratio of intensities of a patient's molecular weight-categorized VWFMs, and those of a healthy subject's, using densitometric analysis. VWF degradation product (DP) was measured via ELISA using a monoclonal antibody that specifically recognizes Y1605 at the C-terminal boundary, which is exposed following ADAMTS13-mediated cleavage of the Y1605-M1606 bond of the VWF A2 domain. RESULTS: Patients with higher platelet counts had a significantly reduced high molecular weight (HMW)-VWFM index and an increased VWF-DP:VWF antigen (Ag) ratio compared to those with lower platelet counts. On multivariate analysis, the VWF-DP/VWF:Ag ratio was an independent predictor of the HMW-VWFM index. Patients who underwent cytoreductive therapy had a significantly higher HMW-VWFM index and lower VWF-DP/VWF:Ag ratio than those who did not. Among individual patients, there was also a significant increase in the HMW-VWFM index and a decrease in the VWF-DP/VWF:Ag ratio after cytoreductive therapy compared to pre-therapy values. CONCLUSION: In patients with ET, an increased platelet count is associated with enhanced cleavage of VWF at the Y1605-M1606 bond, primarily by ADAMTS13, leading to AVWS. Cytoreductive therapy reduces the platelet count, prevents excessive VWF cleavage, and improves VWFM distributions.

Management of a COVID-19 Patient during ECMO: Paying Attention to Acquired von Willebrand Syndrome.

Patients with severe COVID-19 often experience complications including coagulopathy and fatal thrombosis. COVID-19 pneumonia sometimes leads to acute respiratory distress syndrome, requiring extracorporeal membrane oxygenation (ECMO), during which thrombosis and bleeding are major causes of death. Anticoagulation such as heparin is essential for COVID-19 patients on ECMO; however, bleeding might be caused by not only heparin, but also acquired von Willebrand syndrome (AVWS). To date, no study has examined ECMO-related bleeding and AVWS in COVID-19 patients.We report a COVID-19 patient who experienced bleeding from AVWS in addition to disseminated intravascular coagulation (DIC) during ECMO. The level of high-molecular weight VWF multimers decreased during ECMO therapy, and these findings promptly improved after discontinuation of ECMO. Plasma levels of VWF antigen were extremely high, probably due to endothelial cell damage caused by COVID-19. On the other hand, plasma levels of ADAMTS13 activity were moderately reduced, to 20-30% of normal. The patient was successfully treated with cryoprecipitate in bleeding during ECMO without a reduction in heparin, which might have induced thromboembolism. Bleeding found in this patient might be caused by AVWS and DIC.Severe COVID-19 patients are in a thrombotic state and need to receive anticoagulant therapy. However, once they receive ECMO therapy, bleeding symptoms could be observed. In such cases, physicians should think of AVWS in addition to the side effect of heparin and DIC.

Analysis focusing on plasma von Willebrand factor in pachychoroid neovasculopathy and age-related macular degeneration.

Pachychoroid neovasculopathy (PNV) is a new concept of macular disorder. Some cases diagnosed as age-related macular degeneration (AMD) have been re-diagnosed as PNV. However, the biological features of PNV are still uncertain. The purpose of this study was to compare PNV and AMD by analyses focusing on von Willebrand factor (VWF) and complement factor H (CFH). Ninety-seven patients who were previously diagnosed with treatment naïve AMD were enrolled in this study. They were re-classified as either PNV or AMD based on the clinical criteria and 33 patients were classified as PNV and 64 patients as AMD. We examined the clinical data, analyzed VWF multimer and two genetic polymorphisms (I62V and Y402H) in the CFH. PNV group was significantly younger than AMD group (P = 0.001). In both I62V and Y402H, there were no significant differences between PNV and AMD while the recessive homozygous (AA) was found only in PNV group in I62V. The presence of unusually large VWF multimers (UL-VWFMs) and subretinal hemorrhages were significantly higher in PNV than in AMD (P = 0.045, P = 0.020, respectively). Thus, the residual UL-VWFMs may result in platelet thrombosis and hemorrhages in the choriocapillaris of PNV. In conclusion, our results suggest the biological differences between PNV and AMD.

Optimization of anti-ADAMTS13 antibodies for the treatment of ADAMTS13-related bleeding disorder in patients receiving circulatory assist device support.

ADAMTS13 (a disintegrin-like and metalloproteinase with thrombospondin type-1 motif 13)-related bleeding disorder has been frequently observed as a life-threatening clinical complication in patients carrying a circulatory assist device. Currently, treatment modalities for the bleeding disorder are very limited and not always successful. To address the unmet medical need, we constructed humanized antibodies of mouse anti-ADAMTS13 antibody A10 (mA10) by using complementarity-determining region (CDR) grafting techniques with human antibody frameworks, 8A7 and 16E8. The characteristics of the two humanized A10 antibodies, namely A10/8A7 and A10/16E8, were assessed in vitro and in silico. Among the two humanized A10 antibodies, the binding affinity of A10/16E8 to ADAMTS13 was comparable to that of mA10 and human-mouse chimeric A10. In addition, A10/16E8 largely inhibited the ADAMTS13 activity in vitro. The results indicated that A10/16E8 retained the binding affinity and inhibitory activity of mA10. To compare the antibody structures, we performed antibody structure modeling and structural similarity analysis in silico. As a result, A10/16E8 showed higher structural similarity to mA10, compared with A10/8A7, suggesting that A10/16E8 retains a native structure of mA10 as well as its antigen binding affinity and activity. A10/16E8 has great potential as a therapeutic agent for ADAMTS13-related bleeding disorder.