Construction and Expression of Mouse-human Chimeric Antibody SZ-51 Specific for Activated Platelet P-selectin

A murine monoclonal (mAb) SZ-51 specific for human P-selectin may be used for in vivo thrombus imaging and for the targeting of fibrinolytic agents to thrombi. In order to reduce the immunogenicity of the murine mAb SZ-51 in humans, we cloned and sequenced the cDNAs encoding the variable region of mAb SZ-51 in order to develop mouse/human chimeric reagents. The E. coli expression vector. pHENl-SZ51 Fab/Hu was constructed by fusing the variable regions of mAb SZ-51 with human IgG γICHI and Cκ genes. The constructs were introduced into E. coli HB2151 for expression of soluble chimeric Fab fragment. We also constructed two fusion products by joining the variable regions of mouse antibody to the appropriate constant regions of human Igγl and κ. These chimeras were cloned into two eukaryotic selectable expression vectors separately, which were then cotransfected into a non-Ig secreting murine myeloma line SP2/0 with lipofectin reagent. Six cell lines remained positive for Ig secretion. The highest producing cell line, which showed stable integration and expression at 5 mg/1 of culture, was selected for the large scale production of chimeric antibody. Immunoblotting analysis demonstrated that both of the chimeric antibodies (SZ51Fab/Hu, SZ51/Hu) in the culture supernatants, like the native mAb SZ-51, bind P-selectin. In addition, the whole chimeric antibody can compete for binding to activated platelets with murine SZ-51. Therefore, the SZ-51 chimeric antibody may be a potential agent for diagnosis and treatment of thrombotic diseases in the future.

Defibrotide Stimulates Expression of Thrombomodulin in Human Endothelial Cells

Cultured human umbilical vein endothelial cells were incubated with defibrotide at concentrations of 0, 5, 50 and 500 jxg/ml for 4 and 24 h respectively. Thrombomodulin activity and molecules on the surface of the cells were determined by chromogenic assay and radioimmunoassay, thrombomodulin antigen in endothelial cells and in conditioned medium of the cells was measured by immunoradioassay. Thrombomodulin mRNA within the cells was analysed by slot blot. After 24 h of incubation, the activity and molecules of thrombomodulin on the surface of endothelial cells, as well as the antigen and mRNA of thrombomodulin in the cells were significantly increased in a dose dependent manner. However, the level of thrombomodulin antigen in conditioned medium was about equal to that of the control. Our data indicate that defibrotide stimulates expression of thrombomodulin in human endothelial cells. These beneficial effects may play a role in antithrombotic activity of defibrotide.

Application of GPIIIa Gene Taq I Polymorphism to Determination of Carrier Status in Glanzmann’s Thrombasthenia Families of Chinese Origin

Glanzmann’s thrombasthenia is a bleeding disorder caused by qualitative and/or quantitative defects of platelet membrane glycoprotein (GP) IIb/IIIa complex. The disease is inherited in an autosomal recessive manner. In this paper, cDNA probes were used to study restriction fragment length polymorphisms (RFLPs) in GPIIIa gene. A Taq I polymorphism was identified and this RFLP was composed of variant bands of 6.5 Kb/4.0 and 2.5 Kb with a frequency of 0.46/0.54 in Chinese population. The Taq I polymorphism was further localized by polymerase chain reaction (PCR) method to exon VIII of the GPIIIa gene. In two Glanzmann’s thrombasthenia families, the Taq I RFLP studied by both Southern blotting and PCR methods identified the defective GPIIIa gene inherited by patients, and determined the genotype of asymptomatic subjects. Analysis of this Taq I polymorphism by PCR method should be potentially useful in future for the carrier detection and prenatal diagnosis in Glanzmann’s thrombasthenia families.

Plasma soluble podoplanin is a novel marker for the diagnosis of tumor occurrence and metastasis

Podoplanin (PDPN) is expressed on many tumors and is involved in tumor metastasis. The objective of the present study was to develop an ELISA for determining soluble PDPN (sPDPN) levels as a potential novel tumor marker in plasma of patients with cancers for detection of tumor occurrence and metastasis. Mouse monoclonal antibodies (mAb) against human PDPN were developed and characterized. Two anti-PDPN mAb, SZ-163 and SZ-168, were used in a sandwich ELISA to detect plasma sPDPN in patients with cancers and in normal individuals. The levels of sPDPN were detected in patients with adenocarcinoma (87 cases, 31.09 ± 5.48 ng/ml), squamous cell carcinoma (86 cases, 6.91 ± 0.59 ng/ml), lung cancer (45 cases, 26.10 ± 7.62 ng/ml), gastric cancer (38 cases, 23.71 ± 6.90 ng/ml) and rectal cancer (27 cases, 32.98 ± 9.88 ng/ml), which were significantly higher than those in normal individuals (99 cases, 1.31 ± 0.13 ng/ml) (P < .0001). Moreover, the sPDPN levels in patients with metastatic cancers were higher (192 cases, 30.35 ± 3.63 ng/ml) than those in non-metastatic cancer patients (92 cases, 6.28 ± 0.77 ng/ml) (P < .0001). The post-treatment sPDPN levels of cancer patients (n = 156) (4.47 ± 0.35 ng/ml) were significantly lower compared with those seen pre-treatment (n = 128) (43.74 ± 4.97 ng/ml) (P < .0001). These results showed that an ELISA method was successfully established for quantitation of plasma sPDPN and plasma sPDPN levels correlate significantly with tumor occurrence and metastasis.

Studies on Reference Intervals for Platelet Counts in Three Cities in China and one in Japan

Hematological parameters including platelet counts, etc. were determined in 1,140 healthy subjects living in four cities: Suzhou (Jiangsu Province), Chengdu (Sichuan Province) and Harbin (Heilongjang Province) in China, and Kobe in Japan. Then, the reference intervals for platelet counts were calculated and compared. The reference interval for platelet count of subjects aged between 18 and 60 years was 60-259 × 109/L in Suzhou and 52–202 × 109/L in Chengdu, and subjects with platelet counts of 100 × 109/L or less accounted for about 30% of the subjects examined in these cities. The reference intervals in Harbin and Kobe were within the range of 150–350 × 109/L, and no subject having a platelets count of 100 × 109/L or less was detected. Mean platelet volume (MPV) determined concurrently was negatively correlated with platelet count, and the reference intervals for MPV in Chengdu and Suzhou were higher than those in Harbin and Kobe.

P-selectin-targeting of the fibrin selective thrombolytic Desmodus rotundus salivary plasminogen activator α1

During thrombosis, P-selectin is expressed on the surface of activated endothelial cells and platelets. We hypothesized that targeting a plasminogen activator (PA) to P-selectin would enhance local thrombolysis and reduce bleeding risk. Previously, a urokinase (uPA)/anti-P-selectin antibody (HuSZ51) fusion protein was shown to increase fibrinolysis in a hamster pulmonary embolism model. To explore the therapeutic potential of this targeting strategy, we fused the fibrin-selective Desmodus rotundus salivary PA α1 (dsPAα1) to HuSZ51 and compared the fibrinolytic activity of P-selectin-targeted dsPAα1 (HuSZ51-dsPAα1) to unmodified dsPAα1 in vitro and in vivo. HuSZ51-dsPAα1 and dsPAα1 were expressed in CHO cells and purified to homogeneity by affinity chromatography. HuSZ51dsPAα1 bound to thrombin-activated human and dog platelets with comparable affinities to that of parental antibody SZ51. The fusion protein retained the catalytic activities of dsPAα1 in chromogenic and clot lysis assays, indicating that dsPAα1 is fully functional when fused to HuSZ51. Compared to dsPAα1, HuSZ51-dsPAα1 had similar thrombolytic efficacy in a rat pulmonary embolism model and anti-thrombotic potency in a dog model of femoral artery thrombosis. However, HuSZ51dsPAα1 was less effective in lysis of preexisting arterial thrombi in the dog model. The reduced arterial thrombolysis was not due to the pharmacokinetic properties of HuSZ51-dsPAα1 because antigen level and amidolytic activity were higher in plasma from HuSZ51-dsPAα1-treated groups than corresponding dsPAα1-treated groups. These data indicate that the thrombolytic efficacy of HuSZ51-dsPAα1 varied dependent on the physical composition of thrombi. The lack of stimulation by fibrin in arterial thrombi may contribute to the attenuated thrombolytic efficacy of HuSZ51-dsPAα1 in the dog model.

Effects of biological variations on platelet count in healthy subjects in China

The effects of biological variations on platelet counts were investigated in 694 healthy subjects aged 18 to 60 years living in three cities including Chengdu (Sichuan Province), Suzhou (Jiangsu Province) and Harbin (Heilongjang Province) in China. Platelet counts in healthy subjects were significantly lower in Chengdu (52∼202 X 109/L) and Suzhou (60∼259 X 109/L) than in Harbin (154∼348 X 109/L)(p <0.0001), but the mean platelet volume (MPV) determined concurrently was negatively correlated with platelet count, the MPV values were significantly higher in Chengdu (11.8∼15.6 fl) and Suzhou (10.9∼15.8 fl) than in Harbin (9.5∼12.9 fl) (p < 0.0001). Platelet counts were significantly higher in summer (73∼289 X 109/L) than in winter (52∼202 X 109/L) (p <0.0001), but the MPV values were lower in summer (11.2∼14.7 fl) than in winter (11.8∼15.6 fl) (p <0.05) in Chengdu. Platelet associated immunoglobulin (PA-IgG) in Chengdu was revealed to be significantly higher in the low platelet count group (<150 X 109/L, 13.5 ± 7.1 ng/107 PLT) than in the normal platelet count group (≥150 X 109/L, 8.3 ± 2.7 ng/107 PLT)(p <0.0001). Similar results were observed in Suzhou for the reticulated platelet ratio, which was significantly higher in the low platelet count group (19.5 ± 7.1%) than in the normal platelet count group (11.6 ± 2.7%)(p <0.01). The bleeding time in Chengdu showed a significantly longer time in the low platelet count group (8.6 ± 2.3 min) than in the normal platelet count group (6.0 ± 1.2 min)(p <0.01). With regard to the effects of lipids on platelet counts, the HDL values were significantly higher in the normal platelet count group (1.60 ± 0.76 mmol/L) than the low platelet count group (1.23 ± 0.31 mmol/L) (p <0.01); but no significant differences in cholesterol and triglycerides values between the normal and low platelet count groups (p >0.05) were recorded. These findings suggest that the platelet counts could be greatly influenced in healthy subjects by biological variations such as geographical, seasonal, and lipid variations.

Plasma microRNAs characterising patients with immune thrombo cytopenic purpura

Altered microRNA (miRNA) expression has been reported in patients with immune thrombocytopenic purpura (ITP). However, the detailed expression profiling of cell-free circulating miRNAs in ITP patients has not been fully investigated. In this study, we aimed to examine plasma miRNAs in ITP patients and evaluate their diagnostic values. Plasma samples from 74 ITP patients and 58 healthy controls were obtained and allocated into discovery, validation, and therapy-response sets. Initial screen with a miRNA microarray assay identified 23 miRNAs with different levels between ITP patients and healthy controls (>1.5-fold changes; p<0.01). Subsequent quantitative real-time PCR confirmed eight up-regulated miRNAs (miR-320c, miR-642b-3p, miR-1275, miR-3141, miR-4270, miR-4499, miR-4739 and miR-6126) and three down-regulated miRNAs (miR-144–3p, miR-1281 and miR-3162–3p) in ITP patients. The levels of these circulating miRNAs varied, depending on ITP subtypes, i.e. newly-diagnosed, persistent and chronic ITP, and between treatment responders and non-responders. In receiver operator characteristic analysis, 10 miRNAs had positive diagnostic values (p<0.05) when tested individually. The diagnostic value improved when the miRNAs were analysed as a panel or together with the analysis of anti-platelet autoantibodies. Plasma miR-3162–3p levels were also found to positively correlate with platelet counts in ITP patients (r=0.338, p=0.01). Our results indicate that plasma miRNA profiles are altered in ITP patients and that the differentially expressed miRNAs may be used as biomarkers to improve the diagnosis of ITP.

Plasma levels of complement activation fragments C3b and sC5b-9 significantly increased in patients with thrombotic microangiopathy after allogeneic stem cell transplantation

Transplantation-associated thrombotic microangiopathy (TA-TMA) is an uncommon but severe complication in patients undergoing allogeneic stem cell transplantation (allo-SCT). However, the mechanism is unclear. From 2011 to 2014, 20 patients with TA-TMA, 20 patients without, and 54 patients with various other complications, including veno occlusive disease (VOD), graft-versus-host disease (GVHD), and infection, were recruited in the study. Plasma vWF antigen (vWFAg), vWF activity (vWFAc), and ADAMTS13 activity were determined in these patients by ELISAs and FRETS-vWF73 assay, respectively. Plasma C3b, sC5b-9, and CH50 were also determined by ELISAs. Plasma levels of C3b were significantly increased in patients with either TA-TMA (p < 0.0001) or GVHD (p < 0.01). Plasma sC5b-9 and CH50 levels in patients with TA-TMA were also significantly increased (p < 0.001). Plasma ADAMTS13 activity was lower in patients with VOD, but normal with other complications. Both plasma vWFAg and vWFAc levels were not elevated in patients with TA-TMA or VOD compared with those of other groups. Complement activation likely via an alternative pathway (increased C3b, sC5b-9, and CH50) may play a role in the pathogenesis of TA-TMA. ADAMTS13 activity is reduced in VOD, but the ADAMTS13/vWF axis appears to be unaffected in patients with TA-TMA.

Protein kinase A determines platelet life span and survival by regulating apoptosis

Apoptosis delimits platelet life span in the circulation and leads to storage lesion, which severely limits the shelf life of stored platelets. Moreover, accumulating evidence indicates that platelet apoptosis provoked by various pathological stimuli results in thrombocytopenia in many common diseases. However, little is known about how platelet apoptosis is initiated or regulated. Here, we show that PKA activity is markedly reduced in platelets aged in vitro, stored platelets, and platelets from patients with immune thrombocytopenia (ITP), diabetes, and bacterial infections. Inhibition or genetic ablation of PKA provoked intrinsic programmed platelet apoptosis in vitro and rapid platelet clearance in vivo. PKA inhibition resulted in dephosphorylation of the proapoptotic protein BAD at Ser155, resulting in sequestration of prosurvival protein BCL-XL in mitochondria and subsequent apoptosis. Notably, PKA activation protected platelets from apoptosis induced by storage or pathological stimuli and elevated peripheral platelet levels in normal mice and in a murine model of ITP. Therefore, these findings identify PKA as a homeostatic regulator of platelet apoptosis that determines platelet life span and survival. Furthermore, these results suggest that regulation of PKA activity represents a promising strategy for extending platelet shelf life and has profound implications for the treatment of platelet number-related diseases and disorders.

Flow cytometric immunobead assay for quantitative detection of platelet autoantibodies in immune thrombocytopenia patients

BACKGROUND

Platelet autoantibody detection is critical for immune thrombocytopenia (ITP) diagnosis and prognosis. Therefore, we aimed to establish a quantitative flow cytometric immunobead assay (FCIA) for ITP platelet autoantibodies evaluation.

METHODS

Capture microbeads coupled with anti-GPIX, -GPIb, -GPIIb, -GPIIIa and P-selectin antibodies were used to bind the platelet-bound autoantibodies complex generated from plasma samples of 250 ITP patients, 163 non-ITP patients and 243 healthy controls, a fluorescein isothiocyanate (FITC)-conjugated secondary antibody was the detector reagent and mean fluorescence intensity (MFI) signals were recorded by flow cytometry. Intra- and inter-assay variations of the quantitative FCIA assay were assessed. Comparisons of the specificity, sensitivity and accuracy between quantitative and qualitative FCIA or monoclonal antibody immobilization of platelet antigen (MAIPA) assay were performed. Finally, treatment process was monitored by our quantitative FCIA in 8 newly diagnosed ITPs.

RESULTS

The coefficient of variations (CV) of the quantitative FCIA assay were respectively 9.4, 3.8, 5.4, 5.1 and 5.8% for anti-GPIX, -GPIb, -GPIIIa, -GPIIb and -P-selectin autoantibodies. Elevated levels of autoantibodies against platelet glycoproteins GPIX, GPIb, GPIIIa, GPIIb and P-selectin were detected by our quantitative FCIA in ITP patients compared to non-ITP patients or healthy controls. The sensitivity, specificity and accuracy of our quantitative assay were respectively 73.13, 81.98 and 78.65% when combining all 5 autoantibodies, while the sensitivity, specificity and accuracy of MAIPA assay were respectively 41.46, 90.41 and 72.81%.

CONCLUSIONS

A quantitative FCIA assay was established. Reduced levels of platelet autoantibodies could be confirmed by our quantitative FCIA in ITP patients after corticosteroid treatment. Our quantitative assay is not only good for ITP diagnosis but also for ITP treatment monitoring.

Efficacy of recombinant factor VIIa for severe bleeding complicated by platelet transfusion refractoriness in patients with hematologic malignancies

INTRODUCTION

Severe bleeding with platelet transfusion refractoriness (PTR) is a common complication associated with reduced survival in patients with hematologic malignancies. The present study aimed to evaluate the efficacy of recombinant factor VIIa (rFVIIa) for severe bleeding complicated by PTR.

MATERIALS AND METHODS

Sixty-four patients suffering from severe bleeding with PTR hospitalized in our center between September 2012 and December 2016 were enrolled in this study. Thirty-two patients received rFVIIa (rFVIIa group) and other conventional hemostatic treatments, while the other 32 patients received conventional hemostatic treatments other than rFVIIa (control group).

RESULTS

The baseline parameters of patients before treatment were similar in both groups. The total response rates to hemostatic treatment at 24h and 48h were significantly higher in the rFVIIa group compared with the control group (p=0.014, p=0.020, respectively). Significantly more patients in the rFVIIa group achieved complete responses (CR) at 24h (p=0.031), 48h (p=0.039), and 72h (p=0.021) compared with the control group. The bleeding score (p=0.029), time to control bleeding (p=0.034), and activated partial thromboplastin time (p=0.021) after hemostatic treatment were significantly lower in the rFVIIa group compared with the control group. Patients who achieved a CR to rFVIIa had a significant survival advantage compared with those with a partial response/no response (p=0.020). No complications with venous or arterial thromboembolism were observed during treatment.

CONCLUSIONS

rFVIIa may provide effective and safe hemostasis in patients suffering from severe bleeding and PTR.

Preclinical efficacy and biological effects of the oral proteasome inhibitor ixazomib in diffuse large B-cell lymphoma

Despite advances in deciphering the molecular pathogenesis of diffuse large B-cell lymphoma (DLBCL), patients with relapsed/refractory disease, particularly those with adverse genetic features (e.g., mutated p53 or double hit lymphoma (DHL)) have very poor prognoses, and effective therapies are lacking. In this study we examined the preclinical efficacy and associated biological effects of the first oral proteasome inhibitor, ixazomib, in DLBCL in vitro and in vivo models. We demonstrated that ixazomib exhibited anti-tumor activities in 28 representative DLBCL cell lines, 10 primary DLBCL samples, and a DHL xenotransplant mouse model, at clinically achievable drug concentrations. Ixazomib sensitivity in DLBCL cells is correlated with immunoproteasomal activity; stimulating lymphoma cells with interferon gamma induced immunoproteasome activity and sensitized these cells to ixazomib. In addition, we showed that ixazomib induces apoptosis and the DNA damage response pathway, through activation of the checkpoint kinase 2 (CHK2). Hence, pharmacological inhibition of CHK2 enhances the anti-tumor activity of ixazomib in DLBCL cells. Our results indicate that ixazomib is an effective proteasome inhibitor active in DLBCL, including DHL, and its combination with a CHK2 inhibitor offers a potentially more robust therapeutic regimen for treatment-resistant DLBCL.

Development of a novel flow cytometric immunobead array to quantify VWF: Ag and VWF: GPIbR and its application in acute myocardial infarction

OBJECTIVES

Both von Willebrand disease (VWD) and acute myocardial infarction (AMI) involve quantitative and qualitative changes in von Willebrand factor (VWF). Our objective was to develop a rapid and precise flow cytometric immunobead array (FCIA) to quantify VWF antigen (VWF:Ag) and ristocetin-triggered platelet glycoprotein Ib binding (VWF:GPIbR) and apply it in a clinical setting.

METHODS

Microbeads, coated with monoclonal antibodies for SZ29 or SZ151 IgG, were incubated with diluted plasma. VWF-binding microbeads were detected with FITC-conjugated sheep-anti-human VWF IgG by flow cytometry. Plasma VWF:Ag and VWF:GPIbR levels in normal controls (CTL; n=105), patients with VWD (n=21), and patients with AMI (n=146) were tested by FCIA and ELISA in parallel. ADAMTS13 activity and VWF multimer analyses were also implemented.

RESULTS

Our novel FCIA showed a strong correlation with the ELISA results (VWF:Ag, r=.855; VWF:GPIbR, r=.813). The intra-assay coefficient variations (CVs) of VWF:Ag-FCIA and VWF:GPIbR-FCIA were 9.2% and 7.7%, respectively, and the interassay CVs were 12.6% and 13.5%, respectively. Plasma VWF:Ag and VWF:GPIbR levels were significantly higher in patients with AMI than in CTL (P<.0001), whereas the ratios of ADAMTS13/VWF:Ag and ADAMTS13/VWF:GPIbR were significantly lower (P<.0001). Levels of plasma ultra-large VWF (UL-VWF) were dramatically increased in patients with AMI.

CONCLUSIONS

The novel VWF:Ag and VWF:GPIbR-FCIA assays were found to be simpler, more specific, and more accurate than the classical ELISA method. In addition, elevated VWF:GPIbR and UL-VWF may contribute to the pathogenesis of AMI.

The chimeric monoclonal antibody MHCSZ-123 against human von Willebrand factor A3 domain inhibits high-shear arterial thrombosis in a Rhesus monkey model

Background

SZ-123, a murine monoclonal antibody that targets the human von Willebrand factor (VWF) A3 domain and blocks the binding of collagen, is a powerful antithrombotic. In a Rhesus monkey model of thrombosis, SZ-123 had no side effects, such as bleeding or thrombocytopenia.

Methods

The mouse/human chimeric version of SZ-123, MHCSZ-123, was developed and maintained inhibitory capacities in vitro and ex vivo after injection into monkeys. CHO-S cells were selected for stable expression of MHCSZ-123. Cell clones with high levels of MHCSZ-123 expression were screened with G418 then adapted to serum-free suspension culture. The antithrombotic effect of MHCSZ-123 on acute platelet-mediated thrombosis was studied in monkeys where thrombus formation was induced by injury and stenosis of the femoral artery, which allowed for cyclic flow reductions (CFRs). CFRs were measured in the femoral artery of anesthetized Rhesus monkeys before and after intravenous administration of MHCSZ-123. Ex vivo VWF binding to collagen, platelet aggregation, platelet counts, and template bleeding time were used as measurements of antithrombotic activity. In addition, plasma VWF and VWF occupancy were measured by ELISA.

Results

Injection of 0.1, 0.3, and 0.6 mg/kg MHCSZ-123 significantly reduced CFRs by 29.4%, 57.9%, and 73.1%, respectively. When 0.3 and 0.6 mg/kg MHCSZ-123 were administered, 46.6%–65.8% inhibition of ristocetin-induced platelet aggregation was observed between 15 and 30 min after injection. We observed minimal effects on bleeding time, minimal blood loss, and no spontaneous bleeding or thrombocytopenia.

Conclusions

The VWF-A3 inhibitor MHCSZ-123 significantly reduced thrombosis in Rhesus monkeys and appeared to be safe and well tolerated.

[A Study on the establishment of immune thrombocytopenia model induced by anti-platelet GPⅠbα antibodies]

Objective: To establish primary immune thrombocytopenia (ITP) animal model induced by anti-platelet membrane glycoprotein GPⅠbα antibodies AN51 and R300. Methods: Twenty guinea pigs (6-8 week) were divided into 4 groups. Five guinea pigs in each group were intravenously injected with different doses of AN51 (0.05, 0.1, 0.2 μg/g) and 0.2 μg/g IgG as control. The whole blood was collected from inner angular venous plexus. Platelets number was determined by an automated cell counter and Swiss-Jim method. Then, the similar protocol was used to establish ITP nude mice model by intraperitoneal injection of different concentrations of anti-platelet GPⅠbα antibody R300, respectively. Results: ①Five minutes after intravenous injection of AN51 at 0.05, 0.1 and 0.2 μg/g, the platelet counts of guinea pigs reduced about 0-5%, 50%-60% and 70%-80% compared to the control group, respectively. The difference was statistically significant (P<0.01) . ②Six hours after intraperitoneal injection of R300 at 0.05, 0.1, 0.2 μg/g, the platelet counts of nude mice decreased about 20%-30%, 60%-70% and 80%-90% compared to the control group, respectively. The difference was statistically significant (P<0.01) . The nude mice, injected 0.2 μg/g R300 once a day for 2 weeks, showed typical ITP clinical manifestations including large number of petechiaes or ecchymoses on limbs, head and abdomen. Conclusion: AN51 at 0.2 μg/g and R300 at 0.2 μg/g could establish stable ITP model in guinea pigs and nude mice respectively.

A novel monoclonal antibody against the von Willebrand Factor A2 domain reduces its cleavage by ADAMTS13

We developed a novel murine monoclonal antibody (mAb) against the C-terminal α-helix of the human von Willebrand factor A2, designated SZ-179. We showed that SZ-179 inhibited the interactions between VWF and ADAMTS13 and prevented the degradation of high molecular weight VWF multimers. Importantly, SZ-179 reduced the proteolysis of VWF-R1597W mutant by rADAMTS13 dose-dependently under native conditions. Our findings reveal a potential therapeutic target for bleeding disorders.

[Acquired von Willebrand syndrome in three patients and literature review]

OBJECTIVE

To deepen the understanding of acquired von Willebrand syndrome (AVWS).

METHODS

The clinical data of 3 patients were analyzed and related literature were reviewed.

RESULTS

① Case 1, a 70- year- old male, diagnosed as Waldenstrom macroglobulinemia and AVWS, was presented with spontaneous epitaxis and bruising. The VWF∶Ag level was 16%. Treatment was initiated with VWF concentrates. Two cycles of chemotherapy with Bortezomib, thalidomide and Dexamethasone were followed. Partial remission was achieved. Half- year' follow- up showed no sign of spontaneous hemorrhage. ② Case 2, a 48- year- old female, diagnosed as monoclonal gammopathy of undetermined significance and AVWS, was presented with repeated epitaxis. The VWF∶Ag level was 7%. Because the bleeding was slight and self-relieved, no specific treatment was addressed. She was followed up for one and a half year. ③ Case 3, a 50- year- old man, diagnosed as monoclonal gammopathy of undetermined significance and AVWS, was referred to our hospital for presentation with significant hematomas. VWF∶ Ag was reduced to 12%. VWF- containing cryoprecipitate, plasma, intravenous immunoglobulin and rituximab were used to control his bleeding symptom. During the follow-up, spontaneous hemorrhage still occurred occasionally.

CONCLUSIONS

Acquired von Willebrand syndrome presented with heterogeneous symptoms. The level of VWF∶Ag and VWF∶Rco for patients with bleeding disorder should be performed. Abnormal bleeding symptoms in elderly patients without personal or family history of bleeding should prompt consideration of the underlying disorders. Treatment included controlling acute bleeding, curing the underlying diseases and preventing bleeding in high- risk situations. The prognosis of acquired von Willebrand syndrome is mainly related to the underlying diseases.

Integrin-αIIbβ3-mediated outside-in signalling activates a negative feedback pathway to suppress platelet activation

Integrin-αIIbβ3-mediated outside-in signalling is widely accepted as an amplifier of platelet activation; accumulating evidence suggests that outside-in signalling can, under certain conditions, also function as an inhibitor of platelet activation. The role of integrin-αIIbβ3-mediated outside-in signalling in platelet activation is disputable. We employed flow cytometry, aggregometry, immunoprecipitation, and immunoblotting to investigate the role of integrin-αIIbβ3-mediated outside-in signalling in platelet activation. Integrin αIIbβ3 inhibition enhances agonist-induced platelet ATP secretion. Human platelets lacking expression of αIIbβ3 exhibited more platelet ATP secretion than their wild-type counterparts. Moreover, integrin-αIIbβ3-mediated outside-in signals activate SHIP-1, which in turn mediates p-Akt dephosphorylation, leading to inactivation of PI3K/Akt signalling. Furthermore, 3AC (SHIP-1 inhibitor) inhibits platelet disaggregation, and promotes platelet ATP secretion. Upon ADP stimulation, Talin is recruited to αIIbβ3, and it is dissociated from αIIbβ3 when platelets disaggregate. In addition, treatment with RUC2, an inhibitor of αIIbβ3, which blocks αIIbβ3-mediated outside-in signalling, can markedly prevent the dissociation of talin from integrin. SHIP1 Inhibitor 3AC inhibits the dissociation of talin from integrin-β3. These results suggest that integrin-αIIbβ3-mediated outside-in signalling can serve as a brake to restrict unnecessary platelet activation by activated SHIP-1, which mediated the disassociation of talin from β3, leading to integrin inactivation and blocking of PI3K/Akt signalling to restrict platelet ATP secretion.

Deep molecular response by IFN-α and dasatinib combination in a patient with T315I-mutated chronic myeloid leukemia

The T315I mutation is especially challenging as it confers resistance to all first- and second-generation tyrosine kinase inhibitors. We present here a chronic myeloid leukemia patient harboring the T315I and E255V BCR-ABL1 mutation successfully achieved deep molecular response with a combined treatment of dasatinib and IFN-α. To our knowledge, this is the second case of a T315I-bearing chronic myeloid leukemia patient displaying satisfactory response to the combination therapy of dasatinib and IFN-α.