Abstract The majority of the patients affected by acquired thrombotic thrombocytopenic purpura (TTP) develop autoantibodies directed towards ADAMTS13 that interfere with its von Willebrand Factor ...(VWF) processing activity. B cell responses have been shown to primarily target the spacer domain of ADAMTS13 thereby prohibiting the binding of ADAMTS13 to the VWF A2 domain. In this review we summarize recent knowledge gained on the immune recognition and processing of ADAMTS13 by antigen-presenting cells (APCs). HLA-DRB1*11 has been identified as a risk factor for acquired TTP. Analysis of MHC class II/peptide complexes of ADAMTS13 pulsed dendritic cells have shown that the CUB2 domain derived peptide FINVAPHAR is preferentially presented on HLA-DRB1*11. Based on these findings we propose a model for the initiation of the autoimmune reactivity against ADAMTS13 in previously healthy individuals. We hypothesize that mimicry between a pathogen-derived peptide and the CUB2 derived FINVAPHAR-peptide might contribute to the onset of acquired TTP.
Introduction Patients (pts) with high grade B-cell lymphoma (HGBL) with MYC and BCL2 and/or BCL6 gene rearrangements (double hit and triple hit (DH/TH)) have poor outcomes to standard R-CHOP. ...Retrospective studies reported improved disease-free survival (DFS) through intensification with dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, and rituximab (DA-EPOCH-R). This regimen was studied in a small prospective trial including 24 DH/TH and 19 single MYC rearranged (SH) lymphomas (Dunleavy, Lancet Haematol 2019). No prospective studies evaluating DA-EPOCH-R exclusively for pts with DH/TH HGBL have been reported. The HOVON-152 trial aimed to improve outcomes in untreated DH/TH HGBL pts by investigating the efficacy of the immune checkpoint inhibitor nivolumab as consolidation treatment in pts achieving complete metabolic response (CMR) after DA-EPOCH-R induction. Here, we present the efficacy and safety profile of the induction phase with DA-EPOCH-R. Methods HOVON-152 is a prospective, multi-center, single arm phase II trial. Inclusion criteria were pts with newly diagnosed HGBL-DH/TH (according to the WHO 2016 classification), age ≥ 18 years, WHO performance status (PS) 0-3 and Ann Arbor stage II-IV. During the screening period for rearrangement status, pts could receive 1 cycle of R-CHOP or DA-EPOCH-R, followed by 5 cycles of DA-EPOCH-R. All pts received intrathecal CNS prophylaxis. All diagnostic lymphoma samples were centrally reviewed. PET-CT scans were performed at diagnosis, after 3 cycles and at end-of-induction (local review, central review will be reported at the conference). Pts in CMR after induction treatment (Deauville 1-3 or a negative lymphoma biopsy in case of Deauville 4) proceeded to nivolumab consolidation (480 mg every 4 weeks for one year). The HOVON-152 aimed to improve 12 months DFS of pts in CMR after induction from an expected 70% to 85% with nivolumab consolidation. Secondary objectives included evaluation of response rates, overall survival (OS) and safety. With a power of 0.90 a sample size of 97 pts was calculated. Here, we report efficacy (CMR rate) and safety of DA-EPOCH-R induction treatment. Logistic univariate analysis is used to analyze baseline characteristics associated with response. Adverse events (AEs) were defined according to the common terminology criteria for adverse events (CTC AE 5.0), counted by the highest grade per system organ class per patient. Results From August 2018 - March 2022, 97 pts have been enrolled (study inclusion completed). One patient was excluded due to CNS localization. The median age was 62 years (range 35-79); 90 (83%) pts had stage III-IV disease and 52 (54%) had (intermediate-)high international prognostic index (IPI) (Table 1). Central pathology review confirmed DH/TH in all pts. 65 pts (67%) had a BCL2 DH, 11 (12%) a BCL6 DH and 16 (17%) a TH. Dose adjustments were performed conform protocol. The maximum dose-level (DL) achieved was DL1 in 41 (43%), DL2 in 22 (23%), DL3 in 25 (25%), DL4 in 7 (7%) and DL5 in 1 (1%) of the pts. Vincristine dose was reduced in 28/81 (35%) pts. After DA-EPOCH-R induction, 63/96 (66%, 95% CI 55-75%) pts achieved CMR. WHO PS 2-3 (odds ratio (OR) 0.15, 95% CI 0.03-0.85, p=0.03), elevated LDH (OR 0.24, 95%CI 0.10-0.59, p=0.002) and bulky disease defined as ≥10 cm mass (OR 0.23, 95%CI 0.09-0.56, p=0.001), were significantly associated with a lower chance of achieving CMR. During treatment, 7 (7%) pts experienced a grade 5 AE (ileus, intestinal perforation, multi-organ failure/sepsis). Thereof, 4 patients died during DA-EPOCH-R and 3 patients died after DA-EPOCH-R. 31 (32%) experienced a grade 4 AE (e.g. sepsis, perforation, hemorrhage, thrombocytopenia and neutropenia), 21 (22%) a grade 3 AE (e.g. anemia, mucositis, infections and electrolyte disturbances) and 16 (17%) pts a grade 2 AE. Conclusion We report the largest prospective series of DH/TH HGBL patients treated with DA-EPOCH-R. DA-EPOCH-R induction was feasible, with toxicity and dose adjustments as previously described. The observed CMR rate of 66% was lower than previously reported in a prospective cohort of mixed DH/TH and SH patients (74%). For patients achieving CMR, the nivolumab consolidation phase is ongoing. Translational side studies investigating predictive factors to identify patients not achieving CMR are ongoing. For these patients, novel strategies to improve first-line treatment are warranted.
Thrombopoietin receptor agonists are frequently used in treating immune thrombocytopenia (ITP) owing to high response rates and good tolerability. ITP is associated with an increased risk of ...thrombosis. Whether treatment with eltrombopag further increases this risk is controversial. The mechanisms behind the thrombotic risk in ITP are unclear.
To assess platelet function and hypercoagulability in patients with ITP and the effect of eltrombopag thereon.
This prospective multicenter study assessed adult primary patients with ITP who were starting eltrombopag treatment. Platelet (re)activity and hypercoagulability were measured in whole blood or plasma before start and after 2 to 3 weeks of eltrombopag treatment and compared with those of controls. Change over time was assessed by mixed-effects models, and the results were corrected for multiple testing.
We included 16 patients and 33 controls. At baseline, patients with ITP exhibited lower expression of glycoprotein VI, more activated platelets, and lower reactivity toward agonists compared with controls. β-Thromboglobulin levels reduced and thrombin generation peak height increased compared with those of controls. In line with this finding, patients with ITP showed high factor VIII (median, 217%; IQR, 174%-272%) and von Willebrand factor levels (median, 167%; IQR, 109%-198%). Eltrombopag treatment increased thrombin generation potential: lag time decreased and peak height and endogeneous thrombin potential increased. The latter changes were not significant after correction for multiple testing.
Patients with ITP in this study were in a hypercoagulable state, with preactivated platelets, increased thrombin generation potential, and increased levels of factor VIII and von Willebrand factor. Eltrombopag treatment further increased plasma thrombin generation potential but no other hemostatic parameters.
•The occurrence of thrombosis, in both patients with immune thrombocytopenia (ITP) and patients treated with eltrombopag, is incompletely understood.•We performed a prospective cohort study with healthy controls to assess platelet function and hypercoagulability in patients with ITP and the effect of eltrombopag thereon.•Patients with ITP exhibited a hypercoagulable state, with preactivated platelets, increased thrombin generation potential, and increased levels of factor VIII and von Willebrand factor.•Eltrombopag treatment did not influence platelet function but did increase the plasma thrombin generation potential.
Platelet activation leads to secretion of granule contents and to the formation of microvesicles by shedding of membranes from the cell surface. Recently, we have described small internal vesicles in ...multivesicular bodies (MVBs) and α-granules, and suggested that these vesicles are secreted during platelet activation, analogous to the secretion of vesicles termed exosomes by other cell types. In the present study we report that two different types of membrane vesicles are released after stimulation of platelets with thrombin receptor agonist peptide SFLLRN (TRAP) or α-thrombin: microvesicles of 100 nm to 1 μm, and exosomes measuring 40 to 100 nm in diameter, similar in size as the internal vesicles in MVBs and α-granules. Microvesicles could be detected by flow cytometry but not the exosomes, probably because of the small size of the latter. Western blot analysis showed that isolated exosomes were selectively enriched in the tetraspan protein CD63. Whole-mount immuno-electron microscopy (IEM) confirmed this observation. Membrane proteins such as the integrin chains αIIb-β3 and β1, GPIbα, and P-selectin were predominantly present on the microvesicles. IEM of platelet aggregates showed CD63+ internal vesicles in fusion profiles of MVBs, and in the extracellular space between platelet extensions. Annexin-V binding was mainly restricted to the microvesicles and to a low extent to exosomes. Binding of factor X and prothrombin was observed to the microvesicles but not to exosomes. These observations and the selective presence of CD63 suggest that released platelet exosomes may have an extracellular function other than the procoagulant activity, attributed to platelet microvesicles.
Summary Asymptomatic malaria infections are highly prevalent in malaria endemic regions and most of these infections remain undiagnosed and untreated. Whereas conventional malaria symptoms are by ...definition absent, little is known on the more subtle health consequences of these infections. The aim of our study was to analyze the hematologic, vascular and inflammatory effects of patent and subpatent asymptomatic malaria parasitemia in children and adults on the Indonesian island Sumba. Both children and adults with parasitemia had increased high-sensitive C-reactive protein levels compared to aparasitemic individuals. In addition, children, but not adults with parasitemia also had lower platelet counts and Hb levels and higher levels of von Willebrand factor and platelet factor-4, markers of endothelial and platelet activation, respectively. These findings suggest that asymptomatic malaria infections have subtle health consequences, especially in children, and should be regarded as potentially harmful.
Summary
Severe dengue is characterised by thrombocytopenia, plasma leakage and bleeding. Platelets are important for preservation of endothelial integrity. We hypothesised that platelet activation ...with secondary platelet dysfunction contribute to plasma leakage. In adult Indonesian patients with acute dengue, we measured platelet activation status and the response to the platelet agonist TRAP using flow cytometerbased assays. Patients were monitored daily for plasma leakage by ultrasonography. Acute dengue was associated with platelet activation with an increased expression of the activated fibrinogen receptor (α
IIb
β
3
), the lysosomal marker CD63 and the alpha-granule marker CD62P (P-selectin). Upon maximal platelet activation by TRAP, platelet function defects were observed with a significantly reduced maximal activated α
IIb
β
3
and CD63 expression and reduced platelet-monocyte and platelet-neutrophil complexes. Patients in the lowest tertile of activated α
IIb
β
3
and CD63 expression had an odds ratio for plasma leakage of 5.2 (95% confidence interval CI 1.3–22.7) and 3.9 (95% CI 1.1–13.7), respectively, compared to the highest tertile. Platelet-derived serotonin has previously been related to plasma leakage and we found increased intra-platelet serotonin concentrations in our patients. In conclusion, platelet activation with platelet function alterations can be found in patients with acute dengue and this may contribute to dengue-associated plasma leakage.
