The interaction between anti-PF4 antibodies and anticoagulants in vaccine-induced thrombotic thrombocytopenia

Singh, Anurag; Toma, Filip; Uzun, Günalp; Wagner, Teresa R.; Pelzl, Lisann; Zlamal, Jan; Freytag, Verena; Weich, Karoline; Nowak-Harnau, Stefanie; Rothbauer, Ulrich; Althaus, Karina; Bakchoul, Tamam

doi:10.1182/blood.2021013839

Cited by 28 publications

(27 citation statements)

References 30 publications

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“…However, we observed the dilution effect also in sera obtained before IVIG treatment was started. Third, danaparoid in high concentrations can inhibit platelet activation in HIT 20 and VITT antibodies 21 . However, danaparoid treatment was excluded in the majority of patients assessed.…”

Section: Resultsmentioning

confidence: 99%

“…Third, danaparoid in high concentrations can inhibit platelet activation in HIT 20 and VITT antibodies. 21 However, danaparoid treatment was excluded in the majority of patients assessed. We suggest that the most likely explanation is based on the fundamental findings of Huynh et al, 22 who showed that VITT antibodies have very high avidity to PF4.…”

Section: Effect Of Antibody Dilution On the Pipamentioning

confidence: 99%

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Quantitative interpretation of PF4/heparin‐EIA optical densities in predicting platelet‐activating VITT antibodies

Schönborn

Thiele

Esefeld

et al. 2022

Journal of Thrombosis and Haemostasis

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Background Vaccine‐induced immune thrombotic thrombocytopenia (VITT) is a prothrombotic, heparin‐induced thrombocytopenia (HIT)‐mimicking, adverse reaction caused by platelet‐activating anti‐platelet factor 4 (PF4) antibodies that occurs rarely after adenovirus vector‐based COVID‐19 vaccination. Strength of PF4‐dependent enzyme immunoassay (EIA) reactivity—judged by optical density (OD) measurements—strongly predicts platelet‐activating properties of HIT antibodies in a functional test. Whether a similar relationship holds for VITT antibodies is unknown. Objectives To evaluate probability for positive platelet activation testing for VITT antibodies based upon EIA OD reactivity; and to investigate simple approaches to minimize false‐negative platelet activation testing for VITT. Methods All samples referred for VITT testing were systematically evaluated by semiquantitative in‐house PF4/heparin‐EIA (OD readings) and PF4‐induced platelet activation (PIPA) testing within a cohort study. EIA‐positive sera testing PIPA‐negative were retested following 1/4 to 1/10 dilution. Logistic regression was performed to predict the probability of a positive PIPA per magnitude of EIA reactivity. Results Greater EIA ODs in sera from patients with suspected VITT correlated strongly with greater likelihood of PIPA reactivity. Of 61 sera (with OD values >1.0) testing negative in the PIPA, a high proportion (27/61, 44.3%) became PIPA positive when tested at 1/4 to 1/10 dilution. Conclusions VITT serology resembles HIT in that greater EIA OD reactivity predicts higher probability of positive testing for platelet‐activating antibodies. Unlike the situation with HIT antibodies, however, diluting putative VITT serum increases probability of a positive platelet activation assay, suggesting that optimal complex formation depends on the stoichiometric ratio of PF4 and anti‐PF4 VITT antibodies.

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Section: Resultsmentioning

confidence: 99%

Section: Effect Of Antibody Dilution On the Pipamentioning

confidence: 99%

Quantitative interpretation of PF4/heparin‐EIA optical densities in predicting platelet‐activating VITT antibodies

Schönborn

Thiele

Esefeld

et al. 2022

Journal of Thrombosis and Haemostasis

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“…Dysregulated functions of platelets were involved in the vaccine-induced immune thrombotic thrombocytopenia (VITT) 44 . In platelets, rAdVV and RNA vaccination, FOS, JUN , and DUSP1 were commonly upregulated.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, differential gene expression analysis suggested that each vaccine type (rAdVV or mRNA) in individual cell cluster could have different immune response outcome, thus overall immune response should be different depending upon COVID-19 vaccination. Dysregulated functions of platelets were involved in the vaccine-induced immune thrombotic thrombocytopenia (VITT) 44 . In platelets, rAdVV and RNA vaccination, FOS, JUN, and DUSP1 were commonly upregulated.…”

Section: Altered Gene Expression and Signalling Pathways After Radvv ...mentioning

confidence: 99%

Comparative multi-OMICS single cell atlas of five COVID-19 (rAdVV and mRNA) vaccines describe unique and distinct mechanisms of action

Singh

Schulze-Selting

Gabernet

et al. 2022

Preprint

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COVID-19 vaccines based on a range of expression platforms have shown considerable protective efficacy, generating antibody and T cell immune responses. However, molecular pathways underpinning the COVID-19 vaccine priming of immunity against the SARS-CoV-2 virus have not yet been explored extensively. This analysis is critical to the optimization of future vaccination strategies, schedules, and combinations. Thus, we investigated a cohort of individuals pre- and post-vaccination to understand the humoral and cellular immune response against different COVID-19 vaccines, including recombinant adenoviral vector (rAdVV) and mRNA-based vaccines. Single-cell RNA sequencing allowed characterization of monocytes, T, NK and B cell activation at the transcriptomics/proteomic level, in response to different COVID-19 vaccines. Our data revealed that different COVID-19 vaccines elicit a unique and distinct mechanism of action. Specifically, we revealed that rAdVV vaccines negatively regulate CD4+ T cell activation, leukocytes chemotaxis, IL-18 signalling and antigen presentation by monocytes whilst mRNA vaccines positively regulate NKT cell activation, platelets activation and chemokine signalling pathways. An antigen-specific T cell response was already observed following the 1st vaccine dose and was not further augmented after the subsequent 2nd dose of the same vaccine and it was dependent on the type of vaccination used. Our integrated three layered-analyses highlights that COVID-19 vaccines evoke a strong but divergent immune response at the RNA, protein, and cellular levels. Our approach is able to pinpoint efficacy and mechanisms controlling immunity to vaccination and open the door for better vaccination which could induce innate and adaptive immunity equally in the long term.

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“…Finally, reconstituted WB samples were recalcified and run at a shear rate of 250s -1 (10 dyne) for 10 min as previously described. 25,32…”

Section: Methodsmentioning

confidence: 99%

Platelet phosphatidylserine is the critical mediator of thrombosis in heparin-induced thrombocytopenia

Zlamal

Singh

Weich

et al. 2022

Preprint

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Heparin-induced thrombocytopenia (HIT) is a severe immune-mediated prothrombotic disorder caused by antibodies reactive to complexes of platelet factor 4 and heparin. Platelets (PLTs) and their interaction with different immune cells contribute to prothrombotic conditions in HIT. However, the exact mechanisms and the role of different PLT subpopulations to this prothrombotic environment remain poorly understood. In this study, we observed that HIT patient antibodies (Abs) induce relevant changes in PLT phenotype, with the key features being increased P-Selectin expression and procoagulant phosphatidylserine (PS) externalization. Formation of procoagulant PLTs was dependent on engagement of PLT Fc-gamma-RIIA by HIT Abs and resulted in significant increase of thrombin generation on the PLT surface. Using an ex vivo thrombosis model and multi-parameter assessment of thrombus formation, we observed that HIT Ab-induced procoagulant PLTs propagated formation of large PLT aggregates, leukocyte recruitment and most importantly, fibrin network generation. These prothrombotic conditions were prevented via the upregulation of PLTs intracellular cAMP with Iloprost, a clinically approved prostacyclin analogue. Additionally, the functional relevance of high P-Selectin and PS levels on procoagulant PLTs was dissected. While inhibition of P-Selectin did not affect thrombus formation, the specific blockade of PS with Lactadherin prevented HIT Ab-mediated thrombin generation and most importantly procoagulant PLT-mediated thrombus formation ex vivo. Taken together, our findings indicate that procoagulant PLTs are critical mediators of prothrombotic conditions in HIT. Upregulation of cAMP with Iloprost or PS targeting specifc therapeutics could be a promising approach to prevent thromboembolic events in HIT patients.

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The interaction between anti-PF4 antibodies and anticoagulants in vaccine-induced thrombotic thrombocytopenia

Cited by 28 publications

References 30 publications

Quantitative interpretation of PF4/heparin‐EIA optical densities in predicting platelet‐activating VITT antibodies

Quantitative interpretation of PF4/heparin‐EIA optical densities in predicting platelet‐activating VITT antibodies

Comparative multi-OMICS single cell atlas of five COVID-19 (rAdVV and mRNA) vaccines describe unique and distinct mechanisms of action

Platelet phosphatidylserine is the critical mediator of thrombosis in heparin-induced thrombocytopenia

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