PF4 Immunoassays in Vaccine-Induced Thrombotic Thrombocytopenia.
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ABSTRACT:
SUBMITTER: Vayne C
PROVIDER: S-EPMC8174029 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description: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.
| S-EPMC8949646 | biostudies-literature
Project description:In response to the COVID-19 pandemic, vaccines for SARS-CoV-2 were developed, tested, and introduced at a remarkable speed. Although the vaccine introduction had a major impact on the evolution of COVID-19, some potential rare side-effects of the vaccines were observed. Within a short period, three scientific groups from Norway, Germany, and the UK reported cerebral venous sinus thrombosis with thrombocytopenia and anti-platelet factor 4 (anti-PF4) antibodies in individuals following AstraZeneca-Oxford vaccination and named this new syndrome vaccine-induced immune thrombotic thrombocytopenia (VITT). This syndrome was subsequently reported in individuals who received Johnson & Johnson vaccination. In this Viewpoint, we discuss the epidemiology, pathophysiology, and optimal diagnostic and therapeutic management of VITT. Presentation of an individual with possible VITT should raise prompt testing for anti-PF4 antibodies and initiation of treatment targeting autoimmune processes with intravenous immunoglobulin and prothrombotic processes with non-heparin anticoagulation.
| S-EPMC8585488 | biostudies-literature
Project description: Not available
| S-EPMC8063912 | biostudies-literature
Project description:The novel coronavirus pandemic has taken a toll on the global healthcare systems and economy. Safety precautions, along with vaccination, are the most effective preventive measures. The global vaccination program against COVID-19 has dramatically reduced the number of deaths and cases. However, the incidence of thrombotic events and thrombocytopenia post-COVID-19 vaccination known as vaccine-induced thrombotic thrombocytopenia has raised safety concerns. This has led to an element of vaccine hesitancy. The exact mechanism for vaccine-induced thrombotic thrombocytopenia is unknown. Although the incidence of thrombosis associated with COVID-19 vaccination is low, it still requires attention, especially in older people, smokers, and people with preexisting comorbidities. This study aims to review the pathophysiology, diagnosis, and management of vaccine-induced thrombotic thrombocytopenia, to provide a concise and comprehensive update.
| S-EPMC8556865 | biostudies-literature
Project description: Not available
| S-EPMC8279091 | biostudies-literature
Project description:The use of high-dose intravenous immune globulin (IVIG) plus anticoagulation is recommended for the treatment of vaccine-induced immune thrombotic thrombocytopenia (VITT), a rare side effect of adenoviral vector vaccines against coronavirus disease 2019 (Covid-19). We describe the response to IVIG therapy in three of the first patients in whom VITT was identified in Canada after the receipt of the ChAdOx1 nCoV-19 vaccine. The patients were between the ages of 63 and 72 years; one was female. At the time of this report, Canada had restricted the use of the ChAdOx1 nCoV-19 vaccine to persons who were 55 years of age or older on the basis of reports that VITT had occurred primarily in younger persons. Two of the patients in our study presented with limb-artery thrombosis; the third had cerebral venous and arterial thrombosis. Variable patterns of serum-induced platelet activation were observed in response to heparin and platelet factor 4 (PF4), indicating the heterogeneity of the manifestations of VITT in serum. After the initiation of IVIG, reduced antibody-induced platelet activation in serum was seen in all three patients. (Funded by the Canadian Institutes of Health Research.).
| S-EPMC8362588 | biostudies-literature
Project description:In the spring of 2021, reports of rare and unusual venous thrombosis in association with the ChAdOx1 and Ad26.COV2.S adenovirus-based coronavirus vaccines led to a brief suspension of their use by several countries. Thromboses in the cerebral and splanchnic veins among patients vaccinated in the preceding 4 weeks were described in 17 patients out of 7.98 million recipients of the Ad26.COV2.S vaccine (with 3 fatalities related to cerebral vein thrombosis) and 169 cases of cerebral vein thrombosis among 35 million ChAdOx1 recipients. Events were associated with thrombocytopenia and anti-PF4 (antibodies directed against platelet factor 4), leading to the designation vaccine-induced immune thrombotic thrombocytopenia. Unlike the related heparin-induced thrombotic thrombocytopenia, with an estimated incidence of <1:1000 patients treated with heparin, and a mortality rate of 25%, vaccine-induced immune thrombotic thrombocytopenia has been reported in 1:150 000 ChAdOx1 recipients and 1:470 000 Ad26.COV.2 recipients, with a reported mortality rate of 20% to 30%. Early recognition of this complication should prompt testing for anti-PF4 antibodies and acute treatment targeting the autoimmune and prothrombotic processes. Intravenous immunoglobulin (1 g/kg for 2 days), consideration of plasma exchange, and nonheparin anticoagulation (argatroban, fondaparinux) are recommended. In cases of cerebral vein thrombosis, one should monitor for and treat the known complications of venous congestion as they would in patients without vaccine-induced immune thrombotic thrombocytopenia. Now that the Ad26.COV2.S has been reapproved for use in several countries, it remains a critical component of our pharmacological armamentarium in stopping the spread of the human coronavirus and should be strongly recommended to patients. At this time, the patient and community-level benefits of these two adenoviral vaccines vastly outweigh the rare but serious risks of vaccination. Due to the relatively low risk of severe coronavirus disease 2019 (COVID-19) in young women (<50 years), it is reasonable to recommend an alternative vaccine if one is available. Ongoing postmarketing observational studies are important for tracking new vaccine-induced immune thrombotic thrombocytopenia cases and other rare side effects of these emergent interventions.
| S-EPMC8378439 | biostudies-literature
Project description:Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare yet serious adverse effect of the adenoviral vector vaccines ChAdOx1 nCoV-19 (AstraZeneca) and Ad26.COV2.S (Janssen) against COVID-19. The mechanisms involved in clot formation and thrombocytopenia in VITT are yet to be fully determined. Here we show neutrophils undergoing NETosis and confirm expression markers of NETs in VITT patients. VITT antibodies directly stimulate neutrophils to release NETs and induce thrombus formation containing abundant platelets, neutrophils, fibrin, extracellular DNA and citrullinated histone H3 in a flow microfluidics system and in vivo. Inhibition of NETosis prevents VITT-induced thrombosis in mice but not thrombocytopenia. In contrast, in vivo blockage of FcγRIIa abrogates both thrombosis and thrombocytopenia suggesting these are distinct processes. Our findings indicate that anti-PF4 antibodies activate blood cells via FcγRIIa and are responsible for thrombosis and thrombocytopenia in VITT. Future development of NETosis and FcγRIIa inhibitors are needed to treat VITT and similar immune thrombotic thrombocytopenia conditions more effectively, leading to better patient outcomes.
| S-EPMC9441824 | biostudies-literature
Project description:BackgroundThis is a review article on heparin-induced thrombocytopenia, an adverse effect of heparin therapy, and vaccine-induced immune thrombotic thrombocytopenia, occurring in some patients administered certain coronavirus vaccines.Main body/textImmune-mediated thrombocytopenia occurs when specific antibodies bind to platelet factor 4 /heparin complexes. Platelet factor 4 is a naturally occurring chemokine, and under certain conditions, may complex with negatively charged molecules and polyanions, including heparin. The antibody-platelet factor 4/heparin complex may lead to platelet activation, accompanied by other cascading reactions, resulting in cerebral sinus thrombosis, deep vein thrombosis, lower limb arterial thrombosis, myocardial infarction, pulmonary embolism, skin necrosis, and thrombotic stroke. If untreated, heparin-induced thrombocytopenia can be life threatening. In parallel, rare incidents of spontaneous vaccine-induced immune thrombotic thrombocytopenia can also occur in some patients administered certain coronavirus vaccines. The role of platelet factor 4 in vaccine-induced thrombosis with thrombocytopenia syndrome further reinforces the importance the platelet factor 4/polyanion immune complexes and the complications that this might pose to susceptible individuals. These findings demonstrate, how auxiliary factors can complicate heparin therapy and drug development. An increasing interest in biomanufacturing heparins from non-animal sources has driven a growing interest in understanding the biology of immune-mediated heparin-induced thrombocytopenia, and therefore, the development of safe and effective biosynthetic heparins.Short conclusionIn conclusion, these findings further reinforce the importance of the binding of platelet factor 4 with known and unknown polyanions, and the complications that these might pose to susceptible patients. In parallel, these findings also demonstrate how auxiliary factors can complicate the heparin drug development.
| S-EPMC8443112 | biostudies-literature
Project description:Adenoviral-vector based vaccines for coronavirus disease 2019 (COVID-19) have been linked with a thrombotic syndrome, vaccine-induced thrombotic thrombocytopenia (VITT). A key clinical question is whether VITT can be reliably ruled out by the absence of thrombocytopenia. We report on three patients who presented to our institute with this syndrome. Noteworthy in our presentations are two patients who presented for medical assessment of thrombotic symptoms with a normal platelet count, one preceding and one following a period of thrombocytopenia. Prompt diagnosis of VITT is critical to prevent rapid patient decline. We provide herein a new diagnostic algorithm that we believe will help optimally capture case presentations of VITT. These cases broaden and refine our understanding of the disease process and highlight to practitioners that VITT cannot be adequately ruled out by thrombocytopenia alone.
| S-EPMC8440941 | biostudies-literature