Association of human leucocyte antigen loci with vaccine-induced immune thrombotic thrombocytopenia: Potential role of the interaction between platelet factor 4-derived peptides and MHC-II.

No risk factors have been identified for vaccine-induced immune thrombotic thrombocytopenia (VITT) so far. The aim of this study was to identify human leucocyte antigen (HLA) alleles potentially associated with VITT susceptibility. Specific HLA class II alleles were detected with significantly higher frequency in VITT patients compared with Italian controls: DPB1*17:01, DQA1*05:01, and DRB1*11:04. In silico analysis revealed increased affinity of DRB1*11:04 for a platelet factor 4 (PF4)-derived peptide, ITSLEVIKA, that contains two amino acids present in the specific binding site of anti-PF4 antibodies from VITT patients. Our findings show for the first time a genetic predisposition to developing anti-PF4 antibodies in response to Ad-vector vaccines.

Gestational diabetes mellitus is associated with in vivo platelet activation and platelet hyperreactivity.

BACKGROUND: Gestational diabetes mellitus is associated with obstetrical and long-term cardiovascular complications. Although platelet hyperresponsiveness in type-2 diabetes mellitus has been well characterized and has been shown to play a crucial role in cardiovascular complications, this aspect has been little studied in gestational diabetes mellitus. OBJECTIVE: We aimed to evaluate platelet reactivity, in vivo platelet activation, and endothelial function in gestational diabetes mellitus in comparison with normal pregnancy. STUDY DESIGN: This was a prospective, case-control study of 23 women with gestational diabetes mellitus and 23 healthy pregnant women who were studied at 26 to 28 and 34 to 36 weeks of gestation and at 8 weeks postpartum. Platelet reactivity and in vivo platelet activation, including light transmission aggregometry, PFA-100, platelet activation antigen expression, platelet adhesion under flow, platelet nitric oxide and reactive oxygen species production, and endothelial dysfunction markers, were assessed. RESULTS: The study of platelet function showed a condition of platelet hyperreactivity in cases with gestational diabetes mellitus when compared with healthy pregnant women at enrollment, which was further enhanced at the end of pregnancy and tended to decrease 2 months after delivery, although it still remained higher in gestational diabetes mellitus. In vivo platelet activation was also evident in gestational diabetes mellitus, especially at the end of pregnancy, in part persisting up to 8 weeks after delivery. Finally, women with gestational diabetes mellitus showed defective platelet nitric oxide production and endothelial dysfunction when compared with healthy pregnancies. CONCLUSION: Our data showed that gestational diabetes mellitus generates a condition of platelet hyperreactivity that in part persists up to 2 months after delivery. Impaired platelet sensitivity to nitric oxide and reduced platelet and endothelial nitric oxide production may contribute to the platelet hyperreactivity condition. Platelet hyperreactivity may play a role in the long-term cardiovascular complications of gestational diabetes mellitus women.

Is tranexamic acid appropriate for all patients undergoing high-risk surgery?

PURPOSE OF REVIEW: Tranexamic acid (TXA), an antifibrinolytic agent, reduces surgical bleeding in a variety of procedures, such as cardiac, orthopedic, abdominal, and urologic surgery, cesarean section, and neurosurgery. However, there are surgical interventions for which its use is not yet widespread, and some caution persists because of concerns regarding thrombotic risk. The purpose of this review is to analyze the most recent evidence in various subgroups of surgical specialties and the association of TXA with thrombotic events and other side effects (e.g. seizures). RECENT FINDINGS: Recent clinical trials and meta-analyses have shown that the efficacy and safety vary according to the clinical context, timing of administration, and dose. Some reports found that TXA reduces major bleeding by 25% without a significant increase in thrombotic events. SUMMARY: Wider use of TXA has the potential to improve surgical safety, avoid unnecessary blood use, and save healthcare funds.

COVID-19 infection-associated platelet and neutrophil activation is blunted by previous anti-SARS-CoV-2 vaccination.

The effectiveness of vaccination against SARS-CoV-2 in preventing COVID-19 or in reducing severe illness in subjects hospitalized for COVID-19 despite vaccination has been unequivocally shown. However, no studies so far have assessed if subjects who get COVID-19 despite vaccination are protected from SARS-CoV-2-induced platelet, neutrophil and endothelial activation, biomarkers associated with thrombosis and worse outcome. In this pilot study, we show that previous vaccination blunts COVID-19-associated platelet activation, assessed by circulating platelet-derived microvesicles and soluble P-selectin, and neutrophil activation, assessed by circulating neutrophil extracellular trap (NET) biomarkers and matrix metalloproteinase-9, and reduces COVID-19-associated thrombotic events, hospitalization in intensive-care units and death.

Simoctocog alfa (Nuwiq®) in previously untreated patients with severe haemophilia A-Final efficacy and safety results from the NuProtect study.

INTRODUCTION: Simoctocog alfa (Nuwiq®) is a 4th generation recombinant FVIII with proven efficacy for the prevention and treatment of bleeding episodes (BEs) in previously treated patients with severe haemophilia A. The NuProtect study assessed the immunogenicity, efficacy and safety of simoctocog alfa in 108 previously untreated patients (PUPs). The incidence of high-titre inhibitors was 16.2% and no patients with non-null F8 mutations developed inhibitors. AIM: To report the efficacy and safety results from the NuProtect study. METHODS: PUPs received simoctocog alfa for prophylaxis, treatment of BEs, or as surgical prophylaxis. The efficacy of prophylaxis (during inhibitor-free periods) was assessed using annualised bleeding rates (ABRs). The efficacy in treating BEs and in surgical prophylaxis was assessed using a 4-point scale. Adverse events were recorded throughout the study. RESULTS: Of 108 PUPs treated with simoctocog alfa, 103 received at least one prophylactic dose and 50 received continuous prophylaxis for at least 24 weeks. In patients on continuous prophylaxis, the median ABR was 0 (mean 0.5) for spontaneous BEs and 2.5 (mean 3.6) for all BEs. In 85 patients who had BEs, efficacy of BE treatment was excellent or good for 92.9% (747/804) of rated BEs; 92.3% of BEs were treated with 1 or 2 infusions. The efficacy of surgical prophylaxis was excellent or good for 94.7% (18/19) of rated procedures. There were no safety concerns and no thromboembolic events. CONCLUSION: Simoctocog alfa was efficacious and well tolerated as prophylaxis, surgical prophylaxis and for the treatment of BEs in PUPs with severe haemophilia A.

A platelet lipidomics signature in patients with COVID-19.

Ischemic cardiovascular and venous thromboembolic events are a frequent cause of death in severe COVID-19 patients. Platelet activation plays a key role in these complications, however platelet lipidomics have not been studied yet. The aim of our pilot investigation was to perform a preliminary study of platelet lipidomics in COVID-19 patients compared to healthy subjects. Lipid extraction and identification of ultrapurified platelets from eight hospitalized COVID-19 patients and eight age- and sex-matched healthy controls showed a lipidomic pattern almost completely separating COVID-19 patients from healthy controls. In particular, a significant decrease of ether phospholipids and increased levels of ganglioside GM3 were observed in platelets from COVID-19 patients. In conclusion, our study shows for the first time that platelets from COVID-19 patients display a different lipidomics signature distinguishing them from healthy controls, and suggests that altered platelet lipid metabolism may play a role in viral spreading and in the thrombotic complications of COVID-19.

What is the context? Besides respiratory system involvement, venous thromboembolism is a severe complication of COVID-19, largely due to the strong derangement of hemostasis, with platelets playing a central role.Great attention has recently been devoted to lipid alterations in COVID-19, both because viruses by reprogramming cellular lipid metabolism remodel lipid membranes to fuel their replication, and because the COVID-19-associated cytokine storm may affect cell/plasma lipidomic signatures.Lipidomics studies in COVID-19 patients have been performed mainly in plasma and serum.To the best of our knowledge, platelet lipidomics have not been examined despite the central role played by platelets in COVID-19 complications.What is the aim of the study?The aim of our pilot study was to preliminarily explore whether platelet lipidomics is altered in COVID-19 patients compared to age- and sex-matched healthy subjects, analyzing lipidomic profile of ultrapurified platelets.What are the results of our study? Our study shows for the first time that platelets from COVID-19 patients display a different lipidomics signature distinguishing them from healthy controls.Ether phospholipids and, intriguingly, two phytoceramides were lower, while ganglioside GM3 was higher in COVID-19 samples compared to healthy controls.What is the impact?Despite the small number of COVID-19 patients enrolled, recognized as a limitation of our study, we show, for the first time, that platelets from COVID-19 patients present a different lipidomics signature and suggest that altered platelet lipid metabolism may play a significant role in viral spreading and in the thrombotic complications of COVID-19.

Matrix metalloproteinase-2 on activated platelets triggers endothelial PAR-1 initiating atherosclerosis.

AIMS: Platelets participate in atherogenesis with mechanisms not yet fully clarified. Vascular wall MMP-2 is involved in the arterial remodelling accompanying atherosclerosis. Platelets contain and release MMP-2 but no informations are available on its role in atherosclerotic lesion formation. METHODS AND RESULTS: We generated double knockout mice lacking the LDL receptor and MMP-2 only in circulating blood cells showing that they develop significantly lesser femoral intima thickening after photochemical-induced arterial damage and atherosclerotic lesions in the aorta, measured by the en face method, after 4 months of atherogenic diet. Moreover, repeated transfusions of autologous-activated platelets in LDLR-/- mice on atherogenic diet significantly enhanced the extension of aortic atherosclerotic lesions while transfusion of activated platelets from MMP-2-/- mice did not. In vitro coincubation studies showed that platelet-derived MMP-2 plays a pivotal role in the development and progression of atherosclerosis through a complex cross-talk between activated platelets, monocyte/macrophages, and endothelial cells. Translational studies in patients with CAD and chronic HIV infection showed that platelet surface expression of MMP-2 highly significantly correlated with the degree of carotid artery stenosis. CONCLUSION: We show a previously unknown mechanism of the pathway through which platelets expressing MMP-2 trigger the initial phases of atherosclerosis and provide a mechanism showing that they activate endothelial PAR-1 triggering endothelial p38MAPK signalling and the expression of adhesion molecules. The development of drugs blocking selectively platelet MMP-2 or its expression may represent a new approach to the prevention of atherosclerosis.

Anti-severe acute respiratory syndrome coronavirus-2 adenoviral-vector vaccines trigger subclinical antiplatelet autoimmunity and increase of soluble platelet activation markers.

To slow down the coronavirus disease 2019 (COVID-19) pandemic an unequalled vaccination campaign was initiated. Despite proven efficacy and safety, a rare but potentially fatal complication of adenoviral-vector vaccines, called vaccine-induced immune thrombotic thrombocytopenia (VITT), has emerged the pathogenesis of which seems to be related to the development of platelet-activating anti-platelet factor 4 (PF4) antibodies. While a few studies have evaluated the incidence of anti-PF4 positivity in anti-severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccine recipients, to date no studies have assessed whether an antiplatelet immunological response develops and if this associates with platelet and blood clotting activation. We carried out a prospective study in healthy subjects who received the first dose of ChAdOx1 or Ad26.COV2.S or BNT162b2 vaccines to evaluate platelet-specific and non-specific immune response and in vivo platelet activation and blood clotting activation. Individuals receiving ChAdOx1 and, less so, Ad26.COV2.S developed with high frequency auto- or alloantiplatelet antibodies, increased circulating platelet-derived microvesicles and soluble P-selectin associated with mild blood clotting activation. Our study shows that an immunological reaction involving platelets is not uncommon in individuals receiving anti-SARS-CoV-2 vaccination, especially after ChAdOx1 and Ad26.COV2.S, and that it associates with in vivo platelet and blood clotting activation.

Impact of COVID-19 and COVID-19 vaccination on high-risk patients with antiphospholipid syndrome: a nationwide survey.

OBJECTIVES: Patients with APS and triple-positive for aPL are at high risk of recurrent events. As COVID-19 and COVID-19 vaccination may induce thrombotic complications, the objective of the study was to assess the course of COVID-19 and adverse events after vaccination in these patients. METHODS: This is a nationwide multicentre survey conducted in nine APS referral centres by means of a questionnaire. Included patients are thrombotic APS with triple-positive aPL confirmed 12 weeks apart. Reference specialist physicians used a four-graded scale of severity for COVID-19 [from 0 (asymptomatic) to 3 (hospitalization in intensive care unit)] and a six-graded scale for adverse reactions to vaccination [from 0 (transient local injection site sign/symptoms) to 5 (potentially life-threatening reactions)]. Outcomes were considered within a 30-day period. RESULTS: Out of 161 patients interviewed, 18 (11%) had COVID-19. All of them fully recovered without any progression to severe disease nor thromboembolic event. A total of 146 patients received the first (92%) and 129 (80%) the second dose of vaccine; side effects were minimal and, in most cases (83% after the first and 68% after the second vaccination) limited to a sore arm. Fifteen patients (9%) were unvaccinated. Most of them raised doubts on the need for vaccination, complained of poor safety and in general were reluctant about COVID-19 vaccination. CONCLUSION: Patients with triple-positive thrombotic APS did not suffer from severe COVID-19 outcomes. Importantly, COVID-19 vaccination was well tolerated. These data may reassure patients and physicians and contribute to reducing hesitancy in unvaccinated patients.

Novel manifestations of immune dysregulation and granule defects in gray platelet syndrome.

Gray platelet syndrome (GPS) is a rare recessive disorder caused by biallelic variants in NBEAL2 and characterized by bleeding symptoms, the absence of platelet α-granules, splenomegaly, and bone marrow (BM) fibrosis. Due to the rarity of GPS, it has been difficult to fully understand the pathogenic processes that lead to these clinical sequelae. To discern the spectrum of pathologic features, we performed a detailed clinical genotypic and phenotypic study of 47 patients with GPS and identified 32 new etiologic variants in NBEAL2. The GPS patient cohort exhibited known phenotypes, including macrothrombocytopenia, BM fibrosis, megakaryocyte emperipolesis of neutrophils, splenomegaly, and elevated serum vitamin B12 levels. Novel clinical phenotypes were also observed, including reduced leukocyte counts and increased presence of autoimmune disease and positive autoantibodies. There were widespread differences in the transcriptome and proteome of GPS platelets, neutrophils, monocytes, and CD4 lymphocytes. Proteins less abundant in these cells were enriched for constituents of granules, supporting a role for Nbeal2 in the function of these organelles across a wide range of blood cells. Proteomic analysis of GPS plasma showed increased levels of proteins associated with inflammation and immune response. One-quarter of plasma proteins increased in GPS are known to be synthesized outside of hematopoietic cells, predominantly in the liver. In summary, our data show that, in addition to the well-described platelet defects in GPS, there are immune defects. The abnormal immune cells may be the drivers of systemic abnormalities such as autoimmune disease.

Platelet dysfunction in platelet-type von Willebrand disease due to the constitutive triggering of the Lyn-PECAM1 inhibitory pathway.

Platelet-type von Willebrand disease (PT-VWD) is an inherited platelet disorder. It is characterized by macrothrombocytopenia and mucocutaneous bleeding, of variable severity, due to gain-of-function variants of GP1BA conferring to glycoprotein Ibα (GPIbα) enhanced affinity for von Willebrand factor (VWF). The bleeding tendency is conventionally attributed to thrombocytopenia and large VWF-multimer depletion. However, while some indications suggest that platelet dysfunction may contribute to the bleeding phenotype, no information on its characteristics and causes are available. The aim of the present study was to characterize platelet dysfunction in PT-VWD and shed light on its mechanism. Platelets from a PT-VWD patient carrying the p.M239V variant, and from PT-VWD mice carrying the p.G233V variant, showed a remarkable platelet function defect, with impaired aggregation, defective granule secretion and reduced adhesion under static and flow conditions. VWFbinding to GPIbα is known to trigger intracellular signaling involving Src-family kinases (SFK). We found that constitutive phosphorylation of the platelet SFK Lyn induces a negative-feedback loop downregulating platelet activation through phosphorylation of PECAM1 on Tyr686 and that this is triggered by the constitutive binding of VWF to GPIbα. These data show, for the first time, that the abnormal triggering of inhibitory signals mediated by Lyn and PECAM1 may lead to platelet dysfunction. In conclusion, our study unravels the mechanism of platelet dysfunction in PT-VWD caused by deranged inhibitory signaling. This is triggered by the constitutive binding of VWF to GPIbα which may significantly contribute to the bleeding phenotype of these patients.

Germline GATA2 variant disrupting endothelial eNOS function and angiogenesis can be restored by c-Jun/AP-1 upregulation.

GATA2 is a transcription factor with key roles in hematopoiesis. Germline GATA2 gene variants have been associated with several inherited and acquired hematologic disorders, including myelodysplastic syndromes. Among the spectrum of GATA2 deficiency- associated manifestations thrombosis has been reported in 25% of patients, but the mechanisms are unknown. GATA2 was shown to be involved in endothelial nitric oxide synthase (eNOS) regulation and vascular development. We assessed eNOS expression and angiogenesis in patients with GATA2 deficiency. Platelets and blood outgrowth endothelial cells (BOEC) from GATA2 variant carriers showed impaired NO production and reduction of eNOS mRNA and protein expression and of eNOS activity. GATA2 binding to the eNOS gene was impaired in BOEC from GATA2-deficient patients, differently from control BOEC. GATA2 deficiency BOEC showed also defective angiogenesis, which was completely restored by treatment with the NO-donor Snitroso- N-acetylpenicillamine (SNAP). Atorvastatin, but not resveratrol, largely restored eNOS expression, NO biosynthesis and neoangiogenesis in GATA2-deficient BOEC by a mechanism involving increased expression of the eNOS transcription factor AP-1/c-JUN, replacing GATA2 when the latter is inactive. Our results unravel a possible thrombogenic mechanism of GATA2 mutations, definitely establish the regulation of eNOS by GATA2 in endothelial cells and show that endothelial angiogenesis is strictly dependent on the eNOS/NO axis. Given the ability of atorvastatin to restore NO production and angiogenesis by GATA2-deficient endothelial cells, the preventive effect of atorvastatin on thrombotic events and possibly on other clinical manifestations of the syndrome related to deranged angiogenesis should be explored in patients with GATA2 deficiency in an ad hoc designed clinical trial.

Proline-rich tyrosine kinase Pyk2 regulates deep vein thrombosis.

Deep vein thrombosis results from the cooperative action of leukocytes, platelets, and endothelial cells. The proline-rich tyrosine kinase Pyk2 regulates platelet activation and supports arterial thrombosis. In this study, we combined pharmacological and genetic approaches to unravel the role of Pyk2 in venous thrombosis. We found that mice lacking Pyk2 almost completely failed to develop deep venous thrombi upon partial ligation of the inferior vena cava. Pyk2-deficient platelets displayed impaired exposure of phosphatidylserine and tissue factor expression by endothelial cells and monocytes was completely prevented by inhibition of Pyk2. In human umbilical vein endothelial cells (HUVEC), inhibition of Pyk2 hampered IL-1b-induced expression of VCAM and P-selectin, and von Willebrand factor release. Pyk2-deficient platelets showed defective adhesion on von Willebrand factor and reduced ability to bind activated HUVEC under flow. Moreover, inhibition of Pyk2 in HUVEC strongly reduced platelet adhesion. Similarly, Pyk2-deficient neutrophils were unable to efficiently roll and adhere to immobilized endothelial cells under venous flow conditions. Moreover, platelets and neutrophils from Pyk2- knockout mice showed defective ability to form heterogeneous aggregates upon stimulation, while platelet monocyte interaction occurred normally. Consequently, platelet neutrophil aggregates, abundant in blood of wild-type mice upon inferior vena cava ligation, were virtually undetectable in Pyk2-knockout mice. Finally, we found that expression of Pyk2 was required for NETosis induced by activated platelets. Altogether our results demonstrate a critical role of Pyk2 in the regulation of the coordinated thromboinflammatory responses of endothelial cells, leukocytes and platelets leading to venous thrombosis. Pyk2 may represent a novel promising target in the treatment of deep vein thrombosis.

Association of Neutrophil Activation, More Than Platelet Activation, With Thrombotic Complications in Coronavirus Disease 2019.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 infection is associated with hypercoagulability, which predisposes to venous thromboembolism (VTE). We analyzed platelet and neutrophil activation in patients with coronavirus disease 2019 (COVID-19) and their association with VTE. METHODS: Hospitalized patients with COVID-19 and age- and sex-matched healthy controls were studied. Platelet and leukocyte activation, neutrophil extracellular traps (NETs), and matrix metalloproteinase 9, a neutrophil-released enzyme, were measured. Four patients were restudied after recovery. The activating effect of plasma from patients with COVID-19 on control platelets and leukocytes and the inhibiting activity of common antithrombotic agents on it were studied. RESULTS: A total of 36 patients with COVID-19 and 31 healthy controls were studied; VTE developed in 8 of 36 patients with COVID-19 (22.2%). Platelets and neutrophils were activated in patients with COVID-19. NET, but not platelet activation, biomarkers correlated with disease severity and were associated with thrombosis. Plasmatic matrix metalloproteinase 9 was significantly increased in patients with COVID-19. Platelet and neutrophil activation markers, but less so NETs, normalized after recovery. In vitro, plasma from patients with COVID-19 triggered platelet and neutrophil activation and NET formation, the latter blocked by therapeutic-dose low-molecular-weight heparin, but not by aspirin or dypiridamole. CONCLUSIONS: Platelet and neutrophil activation are key features of patients with COVID-19. NET biomarkers may help to predict clinical worsening and VTE and may guide low-molecular-weight heparin treatment.

Carotid Intima-Media Thickness Progression as Surrogate Marker for Cardiovascular Risk: Meta-Analysis of 119 Clinical Trials Involving 100 667 Patients.

BACKGROUND: To quantify the association between effects of interventions on carotid intima-media thickness (cIMT) progression and their effects on cardiovascular disease (CVD) risk. METHODS: We systematically collated data from randomized, controlled trials. cIMT was assessed as the mean value at the common-carotid-artery; if unavailable, the maximum value at the common-carotid-artery or other cIMT measures were used. The primary outcome was a combined CVD end point defined as myocardial infarction, stroke, revascularization procedures, or fatal CVD. We estimated intervention effects on cIMT progression and incident CVD for each trial, before relating the 2 using a Bayesian meta-regression approach. RESULTS: We analyzed data of 119 randomized, controlled trials involving 100 667 patients (mean age 62 years, 42% female). Over an average follow-up of 3.7 years, 12 038 patients developed the combined CVD end point. Across all interventions, each 10 µm/y reduction of cIMT progression resulted in a relative risk for CVD of 0.91 (95% Credible Interval, 0.87-0.94), with an additional relative risk for CVD of 0.92 (0.87-0.97) being achieved independent of cIMT progression. Taken together, we estimated that interventions reducing cIMT progression by 10, 20, 30, or 40 µm/y would yield relative risks of 0.84 (0.75-0.93), 0.76 (0.67-0.85), 0.69 (0.59-0.79), or 0.63 (0.52-0.74), respectively. Results were similar when grouping trials by type of intervention, time of conduct, time to ultrasound follow-up, availability of individual-participant data, primary versus secondary prevention trials, type of cIMT measurement, and proportion of female patients. CONCLUSIONS: The extent of intervention effects on cIMT progression predicted the degree of CVD risk reduction. This provides a missing link supporting the usefulness of cIMT progression as a surrogate marker for CVD risk in clinical trials.

ABO Blood Group and Inhibitor Risk in Severe Hemophilia A Patients: A Study from the Italian Association of Hemophilia Centers.

Considering the profound influence exerted by the ABO blood group system on hemostasis, mainly through the von Willebrand factor and factor VIII (FVIII) complex, we have conducted a study evaluating the possible role of blood type on the risk of inhibitor development in hemophilia A. A total of 287 consecutive Caucasian patients with severe hemophilia A (202 without FVIII inhibitors and 85 with FVIII inhibitors) followed at seven Italian Hemophilia Treatment Centers belonging to the Italian Association of Hemophilia Centers (AICE) were included in the study. A higher prevalence of O blood group was detected in patients without inhibitors as compared in inhibitor patients (55 vs. 30.6%; p < 0.001). Among the other variables analyzed (age, F8 mutation, type and intensity of treatment and treatment regimen), F8 mutation class (high-risk vs. low-risk), and treatment regimen (on-demand vs. prophylaxis) were significantly correlated with inhibitor development. However, on a multivariate analysis, only the effects of F8 mutation and ABO blood type were independent of other covariates, being that non-O blood type is associated with a 2.89-fold increased risk of inhibitor development. In conclusion, our study supports the protective effect of O blood type on inhibitor risk in severely affected hemophilia A patients.

Interactions of adenoviruses with platelets and coagulation and the vaccine-induced immune thrombotic thrombocytopenia syndrome.

The COVID-19 pandemic has had a heavy impact on global health and economy and vaccination remains the primary way of controlling the infection. During the ongoing vaccination campaign some unexpected thrombotic events have emerged in subjects who had recently received the AstraZeneca (Vaxzevria) vaccine or the Johnson and Johnson (Janssen) vaccine, two adenovirus vector-based vaccines. Epidemiological studies confirm that the observed/expected ratio of these unusual thromboses is abnormally increased, especially in women in fertile age. The characteristics of this complication, with venous thromboses at unusual sites, most frequently in the cerebral vein sinuses but also in splanchnic vessels, often with multiple associated thromboses, thrombocytopenia, and sometimes disseminated intravascular coagulation, are unique and the time course and tumultuous evolution are suggestive of an acute immunological reaction. Indeed, plateletactivating anti-PF4 antibodies have been detected in a large proportion of the affected patients. Several data suggest that adenoviruses may interact with platelets, the endothelium and the blood coagulation system. Here we review interactions between adenoviral vectors and the hemostatic system that are of possible relevance in vaccine-associated thrombotic thrombocytopenia syndrome. We systematically analyze the clinical data on the reported thrombotic complications of adenovirus-based therapeutics and discuss all the current hypotheses on the mechanisms triggering this novel syndrome. Although, considering current evidence, the benefit of vaccination clearly outweighs the potential risks, it is of paramount importance to fully unravel the mechanisms leading to vaccineassociated thrombotic thrombocytopenia syndrome and to identify prognostic factors through further research.

Walking-induced endothelial dysfunction predicts ischemic cardiovascular events in patients with intermittent claudication.

Endothelial dysfunction, evaluated by flow-mediated dilatation (FMD), predicts adverse cardiovascular events in patients with intermittent claudication (IC). IC is an example of repeated ischemia/reperfusion injury that may contribute to the progression of vascular disease by worsening endothelial function, a trigger for acute cardiovascular events. The predictive value of effort-induced endothelial dysfunction for cardiovascular events in patients with IC has not been studied previously. The objective of this study was to assess whether exercise-induced endothelial dysfunction is predictive of adverse cardiovascular outcome in IC. In 44 patients with IC, we measured brachial artery FMD by B-mode ultrasonography at rest and 10 minutes after a maximal treadmill exercise. Treadmill exercise halved the FMD (from 3.5 ± 0.6% to 1.45 ± 0.46%, p < 0.05). After a follow-up period of 85 (72-98) months, a total of 20 major cardiovascular events occurred. In a multivariate analysis, a post-exercise reduction of brachial FMD > 1.3% was predictive for cardiovascular events. Maximal exercise-induced endothelial dysfunction is predictive of cardiovascular events in patients with IC.

Long-term treatment with thalidomide for severe recurrent hemorrhage from intestinal angiodysplasia in Glanzmann Thrombasthenia.

Gastrointestinal angiodysplasia (GIA) is the most common cause of occult gastrointestinal bleeding (GIB) requiring often hospitalization and transfusions, especially in patients with hemorrhagic disorders. Thalidomide, impairing neo-angiogenesis, has been successfully used in the management of bleeding in patients with GIA and in particular in patients with inherited bleeding disorders. Only one case of short-term treatment with thalidomide in a patient with Glanzmann thrombasthenia (GT) and recurrent GIB due to GIA has been reported so far.We report the case of a woman with GT developing high frequency recurrent GIB due to GIA requiring repeated blood and platelet transfusions, who was treated with thalidomide obtaining a striking and stable reduction of GIB and of the requirement of platelet and blood transfusions for over 5 years. Moreover, we raise the suspicion that the association between GT and GIA may not be fortuitous.

Search for SARS-CoV-2 RNA in platelets from COVID-19 patients.

The frequent finding of thrombocytopenia in patients with severe SARS-CoV-2 infection (COVID-19) and previous evidence that several viruses enter platelets suggest that SARS-CoV-2 might be internalized by platelets of COVID-19. Aim of our study was to assess the presence of SARS-CoV-2 RNA in platelets from hospitalized patients with aconfirmed diagnosis of COVID-19. RNA was extracted from platelets, leukocytes and serum from 24 COVID-19 patients and 3 healthy controls, real-time PCR and ddPCR for viral genes were carried out. SARS-CoV-2 RNA was not detected in any of the samples analyzed nor in healthy controls, by either RT-PCR or ddPCR, while RNA samples from nasopharyngeal swabs of COVID-19 patients were correctly identified. Viral RNA was not detected independently of viral load, of positive nasopharyngeal swabs, or viremia, the last detected in only one patient (4.1%). SARS-CoV-2 entry in platelets is not acommon phenomenon in COVID-19 patients, differently from other viral infections.