High Prevalence of Anti-PF4 Antibodies Following ChAdOx1 nCov-19 (AZD1222) Vaccination Even in the Absence of Thrombotic Events.

It is unclear whether the ChAdOx1 nCov-19 vaccine can induce the development of anti-PF4 antibodies in vaccinated individuals who have not developed thrombosis. The aim of this prospective study was to evaluate the presence of antibodies against heparin/PF4 in adults who received a first dose of the ChAdOx1 nCov-19 vaccine, and correlate them with clinical data and antibody responses to the vaccine. We detected non-platelet activating anti-PF4 antibodies in 67% (29/43) of the vaccinated individuals on day 22 following the first dose of the ChAdOx1 nCov-19 vaccine, though these were detected in low titers. Furthermore, there was no correlation between the presence of anti-PF4 IgG antibodies and the baseline clinical characteristics of the patients. Our findings suggest that the ChAdOx1 nCov-19 vaccine can elicit anti-PF4 antibody production even in recipients without a clinical manifestation of thrombosis. The presence of anti-PF4 antibodies was not sufficient to provoke clinically evident thrombosis. Our results offer an important insight into the ongoing investigations regarding the underlying multifactorial pathophysiology of thrombotic events induced by the ChAdOx1 nCov-19 vaccine.

Carotid Stent Restenosis and Thrombosis in Rabbits: The Effect of Antiplatelet Agents.

BACKGROUND: The purpose of the study was the comparative assessment of ticagrelor and clopidogrel effects on carotid post-balloon injury (PBI) and on post carotid artery stenting (CAS) rate of in-stent restenosis (ISR) and in-stent thrombosis in atherosclerotic rabbits. METHODS: Forty-eight New Zealand white rabbits on high-fat diet were randomized into 4 groups: A1: PBI and clopidogrel (30 mg/kg/d), A2: PBI and ticagrelor (21 mg/kg twice daily), B1: PBI, CAS, and clopidogrel (30 mg/kg/d), B2: PBI, CAS, and ticagrelor (21 mg/kg twice daily). All rabbits received orally aspirin (10 mg/kg/d) and interventions were performed in their right carotid arteries (RCAs). Optical coherence tomography (OCT) and carotid angiography were performed at end point, while platelet aggregation and lipid profile were measured. After euthanasia both carotids were obtained for histological examination. RESULTS: In B1 group, 3 rabbits presented thrombotic total occlusion of the stents, while none such episode was observed in B2 group. The neointimal areas in RCAs, calculated by OCT, did not differ between A1 and A2 groups, and between B1 and B2 groups (P > .05). From the histological findings, the intima/(media + intima) percentage (%) in RCAs of balloon-injured rabbits did not present any difference between groups (P = .812). Similarly, the immunohistochemically determined accumulation of endothelial cells and macrophages on vascular walls was equivalent between groups (P > .05). CONCLUSION: Following carotid balloon injury and stenting, clopidogrel and ticagrelor did not show any differential effects on the extent of neointimal formation and ISR in atherosclerotic rabbits receiving aspirin. Three thrombotic stent occlusions were noted in the clopidogrel treatment group, but this finding was not statistically significant.

A Successful Mother and Neonate Outcome for a Woman with Essential Thrombocytosis and FV Leiden Heterozygosity.

Essential thrombocytosis (ET) and FV Leiden heterozygosity represent an acquired and hereditable hypercoagulable state, respectively. An uncommon case of coexistence of ET and FV Leiden heterozygosity in a 36-year-old pregnant woman and her successful pregnancy outcome is described. She was considered to be at high risk of thrombosis during her pregnancy and she was treated with both prophylactic dose of LMWH and aspirin daily throughout her pregnancy and for a 6-week period postpartum. The efficacy of the anticoagulation treatment was monitored in various time points not only by measuring anti-Xa levels and D-Dimers but also with new coagulation methods such as rotation thromboelastometry and multiplate. Global assessment of coagulation using additional newer laboratory tests might prove useful in monitoring coagulation pregnancies at high risk for thrombosis.

Do different substitution patterns or plant origin in hydroxyethyl starches affect blood coagulation in vitro?

The effect of hydroxyethyl starches (HES) on blood coagulation is affected by their molecular weight, their molar substitution and the C2/C6 ratio. The solutions of 6% HES 130/0.4 and 6% HES 130/0.42 have similar molecular weight and molar substitution but different C2/C6 ratio and plant origin. In the present study, the comparative effect of 6% HES 130/0.4 versus 6% HES 130/0.42 on blood coagulation was investigated in vitro. Thirty milliliter of blood was obtained from 10 healthy volunteers and was diluted by 10, 30 and 50% using either 6% HES 130/0.4 or HES 130/0.42, respectively. Blood coagulation was assessed using thrombelastography measurements (clotting time, clot formation time, maximal clot firmness and alpha-angle). The assessment of platelet function was performed with whole blood aggregometry after adding thrombin-receptor-activating protein. No differences were noted between respective dilutions of the two HES. Both colloids produced significant reductions below the reference values range in clotting time at 10, 30 and 50% dilutions. The 50% dilution of both colloids resulted in significant reduction of maximal clot firmness, alpha-angle and platelet aggregation. The present study showed that the corn-derived 6% HES 130/0.4 and the potato-derived 6% HES 130/0.42 have the same effect on blood coagulation in vitro.

Reduced carriership of 4G allele of plasminogen activator inhibitor-1 4G/5G polymorphism in very young survivors of myocardial infarction.

There are limited and controversial data regarding the impact of 4G/5G polymorphism of the plasminogen activator inhibitor-1 (PAI-1) gene in the pathogenesis of premature myocardial infarction (MI). We explored whether 4G/5G polymorphism of the PAI-1 gene is associated with the development of MI

Evaluation of a reverse-hybridization StripAssay for the detection of genetic polymorphisms leading to acenocoumarol sensitivity.

Acenocoumarol is mainly catabolized by CYP2C9 isoform of cytochrome P450 (CYP) liver complex and exerts its anticoagulant effect through the inhibition of Vitamin K Epoxide Reductase (VKOR). The most important genetic polymorphisms which lead to an impaired enzymatic activity and therefore predispose to acenocoumarol sensitivity, are considered to be CYP2C9*2 (Arg144Cys), CYP2C9*3 (Ile359Leu) and VKORC1-1639G>A, respectively. In this study we compared the results of the PGXThrombo StripAssay kit (ViennaLab Diagnostics,Vienna, Austria) with direct DNA sequencing and in house Restriction Fragment Length Polymorphisms (RFLP) for the detection of the aforementioned Single Nucleotide Polymorphisms (SNPs). The reverse hybridization StripAssay was found to be equally effective with RFLP and direct DNA sequencing for the detection of CYP2C9*2 and CYP2C9*3 polymorphisms, respectively. The comparison of the RFLP reference method with the reverse hybridization StripAssay for the detection of VKORC1-1639 G>A polymorphism showed that the reverse hybridization StripAsssay might misclassify some A/A homozygotes as heterozygotes. Optimization of the hybridization procedures may eliminate the extra low signal band observed in some samples at the reverse hybridization StripAssay and improve its diagnostic value.

Portal, splenic and mesenteric vein thrombosis in a patient double heterozygous for factor V Leiden and prothrombin G20210A mutation.

We herein report a 56-year-old man who presented with abdominal pain, diarrhea and a 22-kg-weight loss over 4 months. He was on acenocoumarol treatment because of portal, splenic and mesenteric vein thrombosis (PSMVT) 3 months before, with admission international normalized ratio (INR):1.6. Doppler ultrasonography and helical computerized tomographic scan of the abdomen showed complete thrombosis of the extrahepatic portal vein extending into the superior mesenteric vein and splenic vein. The manifestation of thrombosis was in the absence of provocative stimuli or local cause. The patient had a negative history of venous thromboembolism. Thrombophilia workup revealed double heterozygosity for factor V Leiden and prothrombin G20210A mutation. He was immediately started with intravenous unfractionated heparin, followed by oral anticoagulation with target INR 2-3. Five days after a Doppler examination showed significant improvement in the flow within the portal vein, and a computerized tomographic scan of the abdomen 1 month later showed extensive recanalization of the portal venous system. The patient is now 36 months out from the second PSMVT episode and is doing well although maintaining oral lifelong anticoagulation. The case is of particular interest in that PSMVT was the first manifestation of this combined disorder. We conclude that all patients presenting with unexplained PSMVT should be investigated for the presence of a hypercoagulable state. Anticoagulation should be considered in all patients with this diagnosis and should be a lifelong therapy in those with an underlying thrombophilia.

Prevalence of prothrombotic polymorphisms in Greece.

The aim of this study was to assess the prevalence of several polymorphisms in genes that are involved in several pathways such as hemostasis, fibrinolysis, platelet membrane receptor activity, endothelial integrity and function, lipid metabolism, and regulation of blood pressure in healthy subjects of Greek origin. Most of these polymorphisms are mainly associated with conditions such as venous thromboembolism and atherothrombosis, and their prevalence has not been studied yet in Greece. We tested 140 healthy individuals for factor V (FV)1691G/A, FV4070G/A, FII 20210G/A, factor XIII (FXIII) exon 2G/T, fibrinogen beta-455G/A, plasminogen activator inhibitor-1 (PAI-1)-675 4G/5G, human platelet antigens 1 (HPA1) a/b, apolipoprotein B (ApoB) 10708 G/A, apolipoprotein E (ApoE) E2, E3, and E4, angiotensin-converting enzyme (ACE) D/I, 5,10 methylenetetrahydrofolate reductase (MTHFR) 677C/T, and MTHFR 1298A/C polymorphisms using a PCR and reverse hybridization technique that detects all of them simultaneously. The allele frequencies observed are in accordance with those reported in other Caucasian populations and almost identical to those of East Mediterranean populations. This first report from Greece may serve as a baseline for planning further investigations of these polymorphisms in association with several clinical entities and for launching guidelines for patient testing of various disease settings in this population.

VKORC1 and CYP2C9 allelic variants influence acenocoumarol dose requirements in Greek patients.

AIM: To identify the frequencies of the polymorphisms CYP2C9*2, CYP2C9*3 and VKORC1-1639 G>A in the Greek population and investigate whether these polymorphisms and patient demographics (age, sex and comedication) could explain the interindividual variability of acenocoumarol dose requirements for efficient anticoagulation. MATERIALS & METHODS: CYP2C9*2 (Arg144Cys), CYP2C9*3 (Ile359Leu) and VKORC1-1639G>A allelic variants were analyzed in 98 patients treated with acenocoumarol. RESULTS: Allelic frequencies of CYP2C9*2, CYP2C9*3 and VKORC1A were found to be 0.155, 0.075 and 0.485, respectively. Carriership of at least one CYP2C9*3 allele led to the most pronounced reduction in the required mean dose (p<0.0001). In contrast, the CYP2C9*2 allele played a minor role (p=0.3). VKORC1 A/A patients needed approximately a third of the dose required by wild-type patients to achieve the target INR (p<0.0001). Age was the only demographical factor significantly affecting acenocoumarol dose (p<0.0001). In a multivariable regression model, CYP2C9, VKORC1 genotypes and age explained 55% of acenocoumarol dosing variability. CONCLUSION: VKORC1-1639G>A, CYP2C9*2 and CYP2C9*3 polymorphisms were found to predispose to acenocoumarol sensitivity in Greeks. Other hereditary and nongenetic parameters must be incorporated in an individualized dosing algorithm to achieve a safer anticoagulant effect.