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1.
Semin Hematol ; 59(2): 80-88, 2022 04.
Article in English | MEDLINE | ID: covidwho-1882785

ABSTRACT

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a highly prothrombotic disorder that like heparin-induced thrombocytopenia (HIT) is caused by platelet-activating antibodies that recognize platelet factor 4 (PF4). However, unlike HIT-where heparin at low concentrations (0.1-0.5 U/mL) typically enhances antibody-induced platelet activation, platelet activation by VITT sera is usually inhibited by heparin. Further, conventional platelet activation assays for HIT, such as the serotonin-release assay (SRA) and heparin-induced platelet activation (HIPA) test, often yield negative or atypical results when testing VITT sera. Nevertheless, VITT (like HIT) is a "clinical-pathological" disorder whereby laboratory detectability of platelet-activating anti-PF4 antibodies is crucial for diagnosis. VITT antibodies follow 2 fundamental principles of HIT laboratory testing: (1) high probability of a positive PF4-dependent enzyme-immunoassay (EIA), and (2) high probability of a positive platelet activation assay. However, optimal detection of VITT in platelet activation assays requires the addition of PF4, for example, PF4-enhanced SRA (PF4-SRA) and PF4-enhanced HIPA (PIPA). A novel whole blood assay, called the PF4-induced flow cytometry-based platelet activation (PIFPA) assay, exhibits high sensitivity and specificity for VITT. HIT and VITT sera/plasmas differ in their reactivity in rapid HIT immunoassays (90-97% sensitivity for HIT, <25% sensitivity for VITT), consistent with distinct antigen sites on PF4 recognized by HIT and VITT antibodies.


Subject(s)
Antibodies , Purpura, Thrombocytopenic, Idiopathic , Vaccines , Antibodies/analysis , Heparin/adverse effects , Humans , Platelet Factor 4 , Purpura, Thrombocytopenic, Idiopathic/chemically induced , Vaccines/adverse effects
2.
Rinsho Ketsueki ; 63(5): 454-462, 2022.
Article in Japanese | MEDLINE | ID: covidwho-1879648

ABSTRACT

Antiplatelet factor 4 (PF4) antibodies, also known as anti-PF4/heparin complex antibodies, are measured to diagnose heparin-induced thrombocytopenia (HIT). In HIT, anti-PF4 antibodies induced by heparin exposure cause thrombocytopenia and thrombosis. However, in recent years, autoimmune HIT (aHIT) that develops without heparin exposure has been getting attention. In 2021, anti-PF4 antibodies were reported to cause the fatal vaccine-induced immune thrombotic thrombocytopenia (VITT) that developed after adenoviral vector vaccination for COVID-19. HIT, aHIT, and VITT are considered to be caused by anti-PF4 antibodies, and their pathological conditions are similar. However, they have different levels of severity, and the detection sensitivity of their antibodies varies depending on the assay. Herein, we review three pathologies, namely, HIT, aHIT, and VITT, associated with anti-PF4 antibodies.


Subject(s)
COVID-19 , Purpura, Thrombocytopenic, Idiopathic , Thrombocytopenia , Thrombosis , Vaccines , Antibodies , Heparin/adverse effects , Humans , Platelet Factor 4/immunology , Thrombocytopenia/chemically induced , Thrombocytopenia/diagnosis , Thrombosis/etiology , Vaccines/adverse effects
3.
Blood Adv ; 6(11): 3315-3320, 2022 06 14.
Article in English | MEDLINE | ID: covidwho-1879217

ABSTRACT

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare complication after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) adenoviral vector vaccination. In British Columbia (BC), Canada, a provincial clinical care pathway was developed to guide clinicians in evaluating for VITT among patients who present with thrombocytopenia or thrombosis symptoms within 4 to 28 days after adenoviral vector vaccine exposure. All patients had enzyme-linked immunosorbent assay (ELISA) testing for platelet factor 4 (PF4) antibodies, and all cases with positive PF4-ELISA or d-dimer levels ≥2.0 mg/L fibrinogen equivalent units (FEU) had further testing for platelet-activating PF4 antibodies using a modified serotonin release assay (SRA). Between 1 May and 30 June 2021, 37% of 68 patients investigated for VITT had thrombosis, but only 3 had VITT confirmed by PF4-ELISA and SRA. Platelet counts, d-dimer levels, and ELISA optical density values were significantly different between those with and without VITT. Three patients had thrombocytopenia and thrombosis with d-dimer levels >4.0 mg/L FEU but had negative PF4-ELISA and SRA results. Patients with VITT were treated successfully with IV immunoglobulin, nonheparin anticoagulants, and corticosteroids. Our pathway demonstrated that thrombosis is common among patients investigated for VITT and that PF4-ELISA testing is necessary to confirm VITT in those presenting with thrombosis and thrombocytopenia.


Subject(s)
COVID-19 , Purpura, Thrombocytopenic, Idiopathic , Thrombocytopenia , Thrombosis , Vaccines , Antibodies , COVID-19/diagnosis , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , Critical Pathways , Humans , Platelet Factor 4 , Purpura, Thrombocytopenic, Idiopathic/etiology , SARS-CoV-2 , Thrombocytopenia/chemically induced , Thrombocytopenia/etiology , Vaccination , Vaccines/adverse effects
4.
Intern Med J ; 52(5): 717-723, 2022 05.
Article in English | MEDLINE | ID: covidwho-1816561

ABSTRACT

Vaccine-induced thrombotic thrombocytopenia (VITT) is a rare, but serious, syndrome characterised by thrombocytopenia, thrombosis, a markedly raised D-dimer and the presence of anti-platelet factor-4 (PF4) antibodies following COVID-19 adenovirus vector vaccination. VITT occurs at a rate of approximately 2 per 100 000 first-dose vaccinations and appears exceedingly rare following second doses. Our current understanding of VITT pathogenesis is based on the observations that patients with VITT have antibodies that bind to PF4 and have the ability to form immune complexes that induce potent platelet activation. However, the precise mechanisms that lead to pathogenic VITT antibody development remain a source of active investigation. Thrombosis in VITT can manifest in any vascular bed and affect multiple sites simultaneously. While there is a predilection for splanchnic and cerebral venous sinus thrombosis, VITT also commonly presents with deep vein thrombosis and pulmonary embolism. Pillars of management include anticoagulation with a non-heparin anticoagulant, intravenous immunoglobulin and 'rescue' therapies, such as plasma exchange for severe cases. VITT can be associated with a high mortality rate and significant morbidity, but awareness and optimal therapy have significantly improved outcomes in Australia. A number of questions remain unanswered, including why VITT is so rare, reasons for the predilection for thrombosis in unusual sites, how long pathological antibodies persist, and the optimal duration of anticoagulation. This review will provide an overview of the presentation, diagnostic workup and management strategies for patients with VITT.


Subject(s)
COVID-19 , Thrombocytopenia , Thrombosis , Vaccines , Anticoagulants/adverse effects , COVID-19 Vaccines/adverse effects , Humans , Platelet Factor 4/adverse effects , SARS-CoV-2 , Thrombocytopenia/chemically induced , Thrombosis/chemically induced , Thrombosis/complications , Vaccines/adverse effects
5.
Circ Res ; 130(8): 1187-1203, 2022 Apr 15.
Article in English | MEDLINE | ID: covidwho-1789065

ABSTRACT

The risk of stroke and cerebrovascular disease complicating infection with SARS-CoV-2 has been extensively reported since the onset of the pandemic. The striking efforts of many scientists in cooperation with regulators and governments worldwide have rapidly brought the development of a large landscape of vaccines against SARS-CoV-2. The novel DNA and mRNA vaccines have offered great flexibility in terms of antigen production and led to an unprecedented rapidity in effective and safe vaccine production. However, as mass vaccination has progressed, rare but catastrophic cases of thrombosis have occurred in association with thrombocytopenia and antibodies against PF4 (platelet factor 4). This catastrophic syndrome has been named vaccine-induced immune thrombotic thrombocytopenia. Rarely, ischemic stroke can be the symptom onset of vaccine-induced immune thrombotic thrombocytopenia or can complicate the course of the disease. In this review, we provide an overview of stroke and cerebrovascular disease as a complication of the SARS-CoV-2 infection and outline the main clinical and radiological characteristics of cerebrovascular complications of vaccinations, with a focus on vaccine-induced immune thrombotic thrombocytopenia. Based on the available data from the literature and from our experience, we propose a therapeutic protocol to manage this challenging condition. Finally, we highlight the overlapping pathophysiologic mechanisms of SARS-CoV-2 infection and vaccination leading to thrombosis.


Subject(s)
COVID-19 , Stroke , Thrombocytopenia , Thrombosis , Vaccines , COVID-19/complications , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , Humans , Platelet Factor 4/adverse effects , SARS-CoV-2 , Stroke/epidemiology , Stroke/etiology , Thrombocytopenia/chemically induced , Thrombocytopenia/diagnosis , Thrombosis/etiology , Vaccination/adverse effects , Vaccines/adverse effects
6.
Semin Hematol ; 59(2): 89-96, 2022 04.
Article in English | MEDLINE | ID: covidwho-1788341

ABSTRACT

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a novel prothrombotic disorder characterized by thrombosis, thrombocytopenia, and disseminated intravascular coagulation identified in hundreds of recipients of ChAdOx1 nCoV-19 (Oxford/AstraZeneca), an adenovirus vector coronavirus disease 2019 (COVID-19) vaccine. VITT resembles heparin-induced thrombocytopenia (HIT) in that patients have platelet-activating anti-platelet factor 4 antibodies; however, whereas heparin typically enhances platelet activation by HIT antibodies, VITT antibody-induced platelet activation is often inhibited in vitro by pharmacological concentrations of heparin. Further, the thrombotic complications in VITT feature much higher frequencies of atypical thrombosis, most notably cerebral vein thrombosis and splanchnic vein thrombosis, compared with HIT. In this review, we outline the treatments that have been used to manage this novel condition since its recognition in March 2021, including anticoagulation, high-dose intravenous immune globulin, therapeutic plasma exchange, corticosteroids, rituximab, and eculizumab. We discuss the controversial issue of whether heparin, which often inhibits VITT antibody-induced platelet activation, is harmful in the treatment of VITT. We also describe a case of "long VITT," describing the treatment challenges resulting from platelet-activating anti-PF4 antibodies that persisted for more than 9 months.


Subject(s)
COVID-19 Vaccines , COVID-19 , Purpura, Thrombocytopenic, Idiopathic , Thrombosis , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , Heparin/adverse effects , Humans , Platelet Factor 4 , Purpura, Thrombocytopenic, Idiopathic/chemically induced , Thrombosis/chemically induced
7.
Hum Vaccin Immunother ; 18(5): 2050654, 2022 Nov 30.
Article in English | MEDLINE | ID: covidwho-1784264

ABSTRACT

Cases that experienced COVID-19 postvaccination-related thrombosis have been reported after the first dose of ChAdOx1 nCov-19 (Vaxzevria, AstraZeneca) or Ad26.COV2.S (Johnson & Johnson/Janssen) vaccine. These rare thrombotic events were observed within the expected vaccine-induced seroconversion period and could be attributed to platelet-activating (auto)antibodies against platelet factor 4 (PF4). Newly, vaccine-induced, cross-reactive anti-PF4 antibodies could explain this observation. An in-silico analysis using the Basic Local Alignment Search Tool was used to identify sequence similarity between PF4 and antigens contained in or encoded by ChAdOx1 nCov-19 or Ad26.COV2.S vaccines. Only one sequence within the signaling peptide of the SARS-CoV-2 spike protein exhibited a high percent identity (85.71%) with PF4. This sequence overlaps with a proven immunogenic peptide recognized from convalescent COVID-19 sera and could be responsible for the formation of platelet-activating immunocomplexes in susceptible patients. Manipulation of the immunogenicity of this particular sequence within the encoded SARS-CoV-2 spike protein signaling peptide may eliminate this iatrogenic severe adverse effect.


Subject(s)
COVID-19 , Purpura, Thrombocytopenic, Idiopathic , Thrombocytopenia , Thrombosis , /adverse effects , COVID-19/prevention & control , Humans , Platelet Factor 4 , Purpura, Thrombocytopenic, Idiopathic/chemically induced , SARS-CoV-2 , Spike Glycoprotein, Coronavirus , Thrombosis/chemically induced
8.
Semin Hematol ; 59(2): 108-114, 2022 04.
Article in English | MEDLINE | ID: covidwho-1778659

ABSTRACT

In hundreds of patients worldwide, vaccination against COVID-19 with adenovirus vector vaccines (ChAdOx1 nCoV-19; Ad26.COV2.S) triggered platelet-activating anti-platelet factor 4 (PF4) antibodies inducing vaccine-induced immune thrombotic thrombocytopenia (VITT). In most VITT patients, platelet-activating anti-PF4-antibodies are transient and the disorder is discrete and non-recurring. However, in some patients platelet-activating antibodies persist, associated with recurrent thrombocytopenia and sometimes with relapse of thrombosis despite therapeutic-dose anticoagulation. Anti-PF4 IgG antibodies measured by enzyme-immunoassay (EIA) are usually detectable for longer than platelet-activating antibodies in functional assays, but duration of detectability is highly assay-dependent. As more than 1 vaccination dose against COVID-19 is required to achieve sufficient protection, at least 69 VITT patients have undergone subsequent vaccination with an mRNA vaccine, with no relevant subsequent increase in anti-PF4 antibody titers, thrombocytopenia, or thrombotic complications. Also, re-exposure to adenoviral vector-based vaccines in 5 VITT patients was not associated with adverse reactions. Although data are limited, vaccination against influenza also appears to be safe. SARS-CoV-2 infection reported in 1 patient with preceding VITT did not influence anti-PF4 antibody levels. We discuss how these temporal characteristics of VITT provide insights into pathogenesis.


Subject(s)
COVID-19 , Purpura, Thrombocytopenic, Idiopathic , Thrombosis , /adverse effects , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , Humans , Platelet Factor 4/adverse effects , Purpura, Thrombocytopenic, Idiopathic/chemically induced , SARS-CoV-2 , Thrombosis/chemically induced , Thrombosis/complications
9.
Front Immunol ; 13: 807934, 2022.
Article in English | MEDLINE | ID: covidwho-1775663

ABSTRACT

Coronavirus disease 2019 (COVID-19) is a highly prothrombotic viral infection that primarily manifests as an acute respiratory syndrome. However, critically ill COVID-19 patients will often develop venous thromboembolism with associated increases in morbidity and mortality. The cause for this prothrombotic state is unclear but is likely related to platelet hyperactivation. In this review, we summarize the current evidence surrounding COVID-19 thrombosis and platelet hyperactivation. We highlight the fact that several studies have identified a soluble factor in COVID-19 patient plasma that is capable of altering platelet phenotype in vitro. Furthermore, this soluble factor appears to be an immune complex, which may be composed of COVID-19 Spike protein and related antibodies. We suggest that these Spike-specific immune complexes contribute to COVID-19 platelet activation and thrombosis in a manner similar to heparin-induced thrombocytopenia. Understanding this underlying pathobiology will be critical for advancement of future research and therapeutic options.


Subject(s)
COVID-19 , Thrombosis , Antigen-Antibody Complex/adverse effects , Humans , Platelet Activation , Platelet Factor 4 , SARS-CoV-2 , Thrombosis/etiology
10.
Clin Appl Thromb Hemost ; 28: 10760296221091770, 2022.
Article in English | MEDLINE | ID: covidwho-1775237

ABSTRACT

INTRODUCTION: Previous studies have shown that inflammation may contribute to the interplay of endogenous glycosaminoglycans (GAGs) and anti-PF4 antibodies. In this study, we quantified the levels of anti-PF4 antibody isotypes and endogenous GAGs together with inflammatory biomarkers in pulmonary embolism (PE) patients to determine whether there is a relationship in between. Identification of this relationship may provide insight to the complex pathophysiology of PE and HIT and may also be useful for development of potential prognostic, diagnostic and therapeutic interventions. MATERIALS AND METHODS: Plasma samples from PE patients (n: 210) were analyzed for anti-PF4 antibody isotypes and various thrombo-inflammatory cytokines utilizing commercially available biochip array and ELISA methods. The endogenous GAG levels in PE patients' plasma were quantified using a fluorescence quenching method. The collected data analyzed to demonstrate the relationship between various parameters. RESULTS: The endogenous GAG levels were increased in the PE group (P < .05). The levels of anti-PF4 antibody isotypes were higher in varying levels in comparison to the normal group (P < .05). Inflammatory cytokines have shown varying levels of increase with IL-6, IL-8 and IL-10 showing the most pronounced values. Mortality outcome was related to increased GAGs and some of the cytokines. CONCLUSION: In this study, we demonstrated increased levels of anti-PF4 antibody isotypes, endogenous GAGs, and inflammatory biomarkers in a large patient cohort in PE. The levels of the endogenous GAGs and inflammatory biomarkers were associated with PE severity and mortality. More studies are needed to understand this complex pathophysiology.


Subject(s)
Pulmonary Embolism , Thrombocytopenia , Biomarkers , Glycosaminoglycans , Heparin , Humans , Platelet Factor 4 , Thrombocytopenia/diagnosis
11.
Semin Hematol ; 59(2): 97-107, 2022 04.
Article in English | MEDLINE | ID: covidwho-1768934

ABSTRACT

Vaccine-induced immune thrombotic thrombocytopenia (VITT; synonym, thrombosis with thrombocytopenia syndrome, is associated with high-titer immunoglobulin G antibodies directed against platelet factor 4 (PF4). These antibodies activate platelets via platelet FcγIIa receptors, with platelet activation greatly enhanced by PF4. Here we summarize the current concepts in the pathogenesis of VITT. We first address parallels between heparin-induced thrombocytopenia and VITT, and provide recent findings on binding of PF4 to adenovirus particles and non-assembled adenovirus proteins in the 2 adenovirus vector-based COVID-19 vaccines, ChAdOx1 nCoV-19 and Ad26.COV2.S. Further, we discuss the potential role of vaccine constituents such as glycosaminoglycans, EDTA, polysorbate 80, human cell-line proteins and nucleotides as potential binding partners of PF4. The immune response towards PF4 in VITT is likely triggered by a proinflammatory milieu. Human cell-line proteins, non-assembled virus proteins, and potentially EDTA may contribute to the proinflammatory state. The transient nature of the immune response towards PF4 in VITT makes it likely that-as in heparin-induced thrombocytopenia -marginal zone B cells are key for antibody production. Once high-titer anti-PF4 antibodies have been formed 5 to 20 days after vaccination, they activate platelets and granulocytes. Activated granulocytes undergo NETosis and the released DNA also forms complexes with PF4, which fuels the Fcγ receptor-dependent cell activation process, ultimately leading to massive thrombin generation. Finally, we summarize our initial observations indicating that VITT-like antibodies might also be present in rare patients with recurrent venous and arterial thrombotic complications, independent of vaccination.


Subject(s)
COVID-19 Vaccines , COVID-19 , Purpura, Thrombocytopenic, Idiopathic , Thrombosis , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , Edetic Acid/adverse effects , Humans , Platelet Factor 4 , Purpura, Thrombocytopenic, Idiopathic/chemically induced , Thrombosis/chemically induced
12.
Blood Adv ; 6(11): 3494-3506, 2022 Jun 14.
Article in English | MEDLINE | ID: covidwho-1765427

ABSTRACT

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a severe prothrombotic complication of adenoviral vaccines, including the ChAdOx1 nCoV-19 (Vaxzevria) vaccine. The putative mechanism involves formation of pathological anti-platelet factor 4 (PF4) antibodies that activate platelets via the low-affinity immunoglobulin G receptor FcγRIIa to drive thrombosis and thrombocytopenia. Functional assays are important for VITT diagnosis, as not all detectable anti-PF4 antibodies are pathogenic, and immunoassays have varying sensitivity. Combination of ligand binding of G protein-coupled receptors (protease-activated receptor-1) and immunoreceptor tyrosine-based activation motif-linked receptors (FcγRIIa) synergistically induce procoagulant platelet formation, which supports thrombin generation. Here, we describe a flow cytometry-based procoagulant platelet assay using cell death marker GSAO and P-selectin to diagnose VITT by exposing donor whole blood to patient plasma in the presence of a protease-activated receptor-1 agonist. Consecutive patients triaged for confirmatory functional VITT testing after screening using PF4/heparin ELISA were evaluated. In a development cohort of 47 patients with suspected VITT, plasma from ELISA-positive patients (n = 23), but not healthy donors (n = 32) or individuals exposed to the ChAdOx1 nCov-19 vaccine without VITT (n = 24), significantly increased the procoagulant platelet response. In a validation cohort of 99 VITT patients identified according to clinicopathologic adjudication, procoagulant flow cytometry identified 93% of VITT cases, including ELISA-negative and serotonin release assay-negative patients. The in vitro effect of intravenous immunoglobulin (IVIg) and fondaparinux trended with the clinical response seen in patients. Induction of FcγRIIa-dependent procoagulant response by patient plasma, suppressible by heparin and IVIg, is highly indicative of VITT, resulting in a sensitive and specific assay that has been adopted as part of a national diagnostic algorithm to identify vaccinated patients with platelet-activating antibodies.


Subject(s)
Purpura, Thrombocytopenic, Idiopathic , Thrombocytopenia , Thrombosis , Flow Cytometry , Heparin/therapeutic use , Humans , Immunoglobulins, Intravenous/adverse effects , Platelet Factor 4 , Purpura, Thrombocytopenic, Idiopathic/drug therapy , Receptors, Proteinase-Activated/therapeutic use , Thrombocytopenia/diagnosis , Thrombosis/drug therapy
13.
Blood ; 139(23): 3430-3438, 2022 Jun 09.
Article in English | MEDLINE | ID: covidwho-1759684

ABSTRACT

Life-threatening thrombotic events at unusual sites have been reported after vector-based vaccinations against severe acute respiratory syndrome coronavirus 2. This phenomenon is now termed vaccine-induced immune thrombotic thrombocytopenia (VITT). The pathophysiology of VITT is similar to that of heparin-induced thrombocytopenia (HIT) and is associated with platelet-activating antibodies (Abs) against platelet factor 4 (PF4). Therefore, current guidelines suggest nonheparin anticoagulants to treat VITT patients. In this study, we investigated the interactions of heparin, danaparoid, fondaparinux, and argatroban with VITT-Ab/PF4 complexes using an ex vivo model for thrombus formation as well as in vitro assays to analyze Ab binding and platelet activation. We found that immunoglobulin Gs (IgGs) from VITT patients induce increased adherent platelets/thrombus formation in comparison with IgGs from healthy controls. In this ex vivo flow-based model, the procoagulant activity of VITT IgGs was effectively inhibited with danaparoid and argatroban but also by heparin. Interestingly, heparin and danaparoid not only inhibited IgG binding to PF4 but were also able to effectively dissociate the preformed PF4/IgG complexes. Fondaparinux reduced the in vitro generation of procoagulant platelets and thrombus formation; however, it did not affect platelet aggregation. In contrast, argatroban showed no effect on procoagulant platelets and aggregation but significantly inhibited VITT-mediated thrombus formation. Taken together, our data indicate that negatively charged anticoagulants can disrupt VITT-Ab/PF4 interactions, which might serve as an approach to reduce Ab-mediated complications in VITT. Our results should be confirmed, however, in a clinical setting before a recommendation regarding the selection of anticoagulants in VITT patients could be made.


Subject(s)
Anticoagulants , COVID-19 Vaccines , Thrombocytopenia , Thrombosis , Anticoagulants/therapeutic use , COVID-19 Vaccines/adverse effects , Fondaparinux/therapeutic use , Heparin/therapeutic use , Humans , Immunoglobulin G , Platelet Factor 4 , Thrombocytopenia/chemically induced , Thrombocytopenia/drug therapy , Thrombosis/chemically induced , Thrombosis/drug therapy
14.
J Korean Med Sci ; 37(10): e75, 2022 Mar 14.
Article in English | MEDLINE | ID: covidwho-1742199

ABSTRACT

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare but life-threatening complication. VITT strongly mimics heparin-induced thrombocytopenia (HIT) and shares clinical features. Heparin is commonly used to prevent coagulation during hemodialysis. Therefore, nephrologists might encounter patients needing dialysis with a history of heparin exposure who developed thrombotic thrombocytopenia after vaccination. A 70-year-old male presented with acute kidney injury and altered mental status due to lithium intoxication. He needed consecutive hemodialysis using heparin. Deep vein thrombosis of left lower extremity and accompanying severe thrombocytopenia of 15,000/µL on 24 days after vaccination and at the same time, nine days after heparin use. Anti-platelet factor 4 antibody test was positive. Anticoagulation with apixaban and intravenous immunoglobulin (IVIG) infusion resolved swelling of his left calf and thrombocytopenia. There were no definitive diagnostic tools capable of differentiating between VITT and HIT in this patient. Although VITT and HIT share treatment with IVIG and non-heparin anticoagulation, distinguishing between VITT and HIT will make it possible to establish a follow-up vaccination plan in a person who has had a thrombocytopenic thrombotic event. Further research is needed to develop the tools to make a clear distinction between the clinical syndromes.


Subject(s)
/adverse effects , Heparin/adverse effects , Purpura, Thrombocytopenic, Idiopathic/etiology , Renal Dialysis/adverse effects , Thrombocytopenia/etiology , Aged , Anticoagulants/adverse effects , Autoantibodies/blood , Diagnosis, Differential , Humans , Immunoglobulin G/blood , Lithium/toxicity , Male , Platelet Count , Platelet Factor 4/immunology , Purpura, Thrombocytopenic, Idiopathic/blood , Purpura, Thrombocytopenic, Idiopathic/diagnosis , Renal Dialysis/methods , Thrombocytopenia/blood , Thrombocytopenia/diagnosis
15.
Blood ; 139(16): 2553-2560, 2022 04 21.
Article in English | MEDLINE | ID: covidwho-1736329

ABSTRACT

The COVID-19 pandemic has resulted in the rapid development of a range of vaccines against SARS-CoV-2. Vaccine-induced immune thrombocytopenia and thrombosis (VITT) is a rare but life-threatening complication of primarily adenoviral-based vaccines associated with the presence of antibodies to a PF4/polyanion neoepitope and measured by using enzyme-linked immunosorbent assays. Presented are serial anti-PF4/polyanion antibody, platelet, and D-dimer measurements in a large cohort of patients and their relation to relapse. Overall, 51% of patients using the Stago assay had persistently positive anti-PF4/polyanion levels 100 days' postdiagnosis, whereas 94% of patients monitored by using the Immucor assay remain positive. The median duration of positivity of the PF4 assay is 87 days, with 72% of patients remaining positive after a median follow-up of 105 days. The use of plasma exchange seemed to reduce anti-PF4/polyanion levels and increase platelet counts in the acute setting more rapidly than other therapies. The rate of relapse in this study was 12.6%, with all relapsed cases exhibiting persistently positive PF4 antibodies and falling platelet counts. Only one patient had extension of their thrombosis. Overall, despite the persistence of PF4 antibodies in 72% of patients, the rate of relapse was low and did not seem to result in recrudescence of the aggressive clinical picture seen at index presentation. Monitoring of these patients in the UK cohort is ongoing and will aid in definition of the natural history of this novel condition.


Subject(s)
COVID-19 , Purpura, Thrombocytopenic, Idiopathic , Thrombocytopenia , Thrombosis , Vaccines , Antibodies/adverse effects , COVID-19 Vaccines/adverse effects , Heparin/adverse effects , Humans , Pandemics , Platelet Factor 4 , Recurrence , SARS-CoV-2 , Thrombocytopenia/chemically induced , Thrombocytopenia/complications , Vaccines/adverse effects
16.
Platelets ; 33(4): 640-644, 2022 May 19.
Article in English | MEDLINE | ID: covidwho-1713376

ABSTRACT

Thromboembolic events are frequent and associated with poor outcome in severe COVID-19 disease. Anti-PF4/polyanion antibodies are related to heparin-induced thrombocytopenia (HIT) and thrombus formation, but data on these antibodies in unselected COVID-19 populations are scarce. We assessed the presence of anti-PF4/polyanion antibodies in prospectively collected serum from an unselected cohort of hospitalized COVID-19 patients and evaluated if elevated levels could give prognostic information on ICU admission and respiratory failure (RF), were associated with markers of inflammation, endothelial activation, platelet activation, coagulation and fibrosis and were associated with long-term pulmonary CT changes. Five out of 65 patients had anti-PF4/polyanion reactivity with OD ≥0.200. These patients had more severe disease as reflected by ICU admission without any evidence of HIT. They also had signs of enhanced inflammation and fibrinogenesis as reflected by elevated ferritin and osteopontin, respectively, during the first 10 days of hospitalization. Increased ferritin and osteopontin persisted in these patients at 3 months follow-up, concomitant with pulmonary CT pathology. Our finding shows that the presence of anti-PF4/polyanion antibodies in unselected hospitalized COVID-19 patients was not related to HIT, but was associated with disease severity, inflammation, and pulmonary pathology after 3 months.


Subject(s)
COVID-19 , Thrombocytopenia , Anticoagulants/adverse effects , Ferritins/adverse effects , Heparin/adverse effects , Humans , Inflammation , Osteopontin/adverse effects , Platelet Factor 4 , Severity of Illness Index , Thrombocytopenia/diagnosis
17.
Clin Chim Acta ; 529: 42-45, 2022 Apr 01.
Article in English | MEDLINE | ID: covidwho-1705651

ABSTRACT

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel human pathogen causing coronavirus disease 2019 (COVID-19). Rare cases of COVID-19 vaccine-induced immune thrombotic thrombocytopenia (VITT) after the ChAdOx1 nCoV-19 (AstraZeneca) vaccination have been reported. We performed a test for anti-heparin/ platelet factor 4 (PF4) antibodies and functional assay using flow cytometry. METHOD: A healthy woman presented to the emergency department with chest pain, headache, and abdominal pain after the first vaccination with AstraZeneca. Polymerase chain reaction (PCR) test for SARS-CoV-2 was negative. Chest computed tomography (CT) showed pulmonary artery embolism and brain magnetic resonance imaging (MRI) revealed cerebral sinus-venous thrombosis. Abdominal CT demonstrated the thrombosis with occlusion in her right hepatic vein. Laboratory studies revealed decreased platelet counts, and high D-dimer level. Finally, laboratory results indicated high PF4 antibodies level high and a positive platelet activation test, confirming the diagnosis of VITT. RESULTS: Treatments including intravenous immunoglobulin, methylprednisolone and direct oral anticoagulant were administered. The results of a follow-up platelet count and D-dimer were normal. In addition, the titer of PF4 antibodies (optical density: 0.425; normal ≤ 0.4, enzyme-linked immunosorbent assay) fell. After a 3-month follow-up, her general condition improved gradually. CONCLUSIONS: The use of COVID-19 vaccines to prevent SARS-CoV-2 infections and complications is considered the most practicable policy for controlling the COVID-19 pandemic and is being forcefully pursued in the global area. Appropriate laboratory diagnosis facilitates the accurate and rapid diagnosis. Early recognizing and appropriate strategies for VITT are required and can provide these patients with more favorable patient outcomes. This report also elected to make comparisons of clinical manifestation, laboratory diagnosis, and management in patients with VITT.


Subject(s)
COVID-19 , Thrombocytopenia , Thrombosis , Vaccines , COVID-19 Vaccines/adverse effects , Clinical Laboratory Techniques , Female , Humans , Pandemics , Platelet Activation , Platelet Factor 4 , SARS-CoV-2 , Thrombocytopenia/chemically induced , Thrombocytopenia/diagnosis , Thrombosis/complications
18.
Am J Hematol ; 97(5): 519-526, 2022 05.
Article in English | MEDLINE | ID: covidwho-1705173

ABSTRACT

Rare cases of COVID-19 vaccinated individuals develop anti-platelet factor 4 (PF4) antibodies that cause thrombocytopenia and thrombotic complications, a syndrome referred to as vaccine-induced immune thrombotic thrombocytopenia (VITT). Currently, information on the characteristics and persistence of anti-PF4 antibodies that cause VITT after Ad26.COV2.S vaccination is limited, and available diagnostic assays fail to differentiate Ad26.COV2.S and ChAdOx1 nCoV-19-associated VITT from similar clinical disorders, namely heparin-induced thrombocytopenia (HIT) and spontaneous HIT. Here we demonstrate that while Ad26.COV2.S-associated VITT patients are uniformly strongly positive in PF4-polyanion enzyme-linked immunosorbent assays (ELISAs); they are frequently negative in the serotonin release assay (SRA). The PF4-dependent p-selectin expression assay (PEA) that uses platelets treated with PF4 rather than heparin consistently diagnosed Ad26.COV2.S-associated VITT. Most Ad26.COV2.S-associated VITT antibodies persisted for >5 months in PF4-polyanion ELISAs, while the PEA became negative earlier. Two patients had otherwise unexplained mild persistent thrombocytopenia (140-150 x 103 /µL) 6 months after acute presentation. From an epidemiological perspective, differentiating VITT from spontaneous HIT, another entity that develops in the absence of proximate heparin exposure, and HIT is important, but currently available PF4-polyanion ELISAs and functional assay are non-specific and detect all three conditions. Here, we report that a novel un-complexed PF4 ELISA specifically differentiates VITT, secondary to both Ad26.COV2.S and ChAdOx1 nCoV-19, from both spontaneous HIT, HIT and commonly-encountered HIT-suspected patients who are PF4/polyanion ELISA-positive but negative in functional assays. In summary, Ad26.COV2.S-associated VITT antibodies are persistent, and the un-complexed PF4 ELISA appears to be both sensitive and specific for VITT diagnosis.


Subject(s)
COVID-19 , Thrombocytopenia , Vaccines , COVID-19/diagnosis , COVID-19 Vaccines/adverse effects , Heparin/adverse effects , Humans , Platelet Factor 4 , Thrombocytopenia/chemically induced , Thrombocytopenia/diagnosis
19.
Int J Mol Sci ; 23(3)2022 Feb 05.
Article in English | MEDLINE | ID: covidwho-1674671

ABSTRACT

Inflammation and thrombosis are closely intertwined in numerous disorders, including ischemic events and sepsis, as well as coronavirus disease 2019 (COVID-19). Thrombotic complications are markers of disease severity in both sepsis and COVID-19 and are associated with multiorgan failure and increased mortality. Immunothrombosis is driven by the complement/tissue factor/neutrophil axis, as well as by activated platelets, which can trigger the release of neutrophil extracellular traps (NETs) and release further effectors of immunothrombosis, including platelet factor 4 (PF4/CXCL4) and high-mobility box 1 protein (HMGB1). Many of the central effectors of deregulated immunothrombosis, including activated platelets and platelet-derived extracellular vesicles (pEVs) expressing PF4, soluble PF4, HMGB1, histones, as well as histone-decorated NETs, are positively charged and thus bind to heparin. Here, we provide evidence that adsorbents functionalized with endpoint-attached heparin efficiently deplete activated platelets, pEVs, PF4, HMGB1 and histones/nucleosomes. We propose that this elimination of central effectors of immunothrombosis, rather than direct binding of pathogens, could be of clinical relevance for mitigating thrombotic complications in sepsis or COVID-19 using heparin-functionalized adsorbents.


Subject(s)
Blood Proteins/isolation & purification , Heparin/pharmacology , /drug therapy , Blood Coagulation/physiology , Blood Platelets/metabolism , Blood Proteins/metabolism , COVID-19/metabolism , Extracellular Traps/immunology , Extracellular Traps/metabolism , HMGB Proteins/isolation & purification , HMGB Proteins/metabolism , HMGB1 Protein/isolation & purification , HMGB1 Protein/metabolism , Heparin/metabolism , Histones/isolation & purification , Histones/metabolism , Humans , Neutrophils/metabolism , Platelet Activation/immunology , Platelet Factor 4/isolation & purification , Platelet Factor 4/metabolism , SARS-CoV-2/pathogenicity , Sepsis/blood , Sepsis/metabolism , Thromboplastin/metabolism , Thrombosis/drug therapy
20.
Blood ; 139(12): 1903-1907, 2022 03 24.
Article in English | MEDLINE | ID: covidwho-1673896

ABSTRACT

Vaccine-induced thrombotic thrombocytopenia (VITT) is triggered by vaccination against COVID-19 with adenovirus vector vaccines (ChAdOx1 nCoV-19; Ad26.COV2-S). In this observational study, we followed VITT patients for changes in their reactivity of platelet-activating antiplatelet factor 4 (PF4) immunoglobulin G (IgG) antibodies by an anti-PF4/heparin IgG enzyme immunoassay (EIA) and a functional test for PF4-dependent, platelet-activating antibodies, and new thrombotic complications. Sixty-five VITT patients (41 females; median, 51 years; range, 18-80 years) were followed for a median of 25 weeks (range, 3-36 weeks). In 48/65 patients (73.8%; CI, 62.0% to 83.0%) the functional assay became negative. The median time to negative functional test result was 15.5 weeks (range, 5-28 weeks). In parallel, EIA optical density (OD) values decreased from median 3.12 to 1.52 (P < .0001), but seroreversion to a negative result was seen in only 14 (21.5%) patients. Five (7.5%) patients showed persistent platelet-activating antibodies and high EIA ODs for >11 weeks. None of the 29 VITT patients who received a second vaccination dose with an mRNA COVID-19 vaccine developed new thromboses or relevant increase in anti-PF4/heparin IgG EIA OD, regardless of whether PF4-dependent platelet-activating antibodies were still present. PF4-dependent platelet-activating antibodies are transient in most patients with VITT. VITT patients can safely receive a second COVID-19 mRNA-vaccine shot.


Subject(s)
COVID-19 , Thrombocytopenia , Thrombosis , Vaccines , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , Female , Heparin/adverse effects , Humans , Immunoglobulin G , Platelet Factor 4 , Thrombocytopenia/chemically induced , Vaccines/adverse effects
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