RESUMO
BACKGROUND: Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a complication of adenoviral-based vaccine against SARS-CoV-2 due to prothrombotic immunoglobulin (Ig) G antibodies to platelet factor 4 (PF4) and may be difficult to distinguish from heparin-induced thrombocytopenia (HIT) in patients treated with heparin. OBJECTIVES: We assessed the usefulness of competitive anti-PF4 enzyme immunoassays (EIAs) in this context. METHODS: The ability of F(ab')2 fragments of 1E12, 1C12, and 2E1, 3 monoclonal anti-PF4 antibodies, to inhibit the binding of human VITT or HIT antibodies to PF4 was evaluated using EIAs. Alanine-scanning mutagenesis was performed to define the amino acids involved in the interactions between the monoclonal antibodies and PF4. RESULTS: A strong inhibition of VITT IgG binding to PF4 was measured with 1E12 (median inhibition, 93%; n = 8), whereas it had no effect on the binding of HIT antibodies (median, 6%; n = 8). In contrast, 1C12 and 2E1 inhibited VITT (median, 74% and 76%, respectively) and HIT antibodies (median, 68% and 53%, respectively) binding to PF4. When a competitive anti-PF4 EIA was performed with 1E12 for 19 additional VITT samples, it strongly inhibited IgG binding to PF4, except for 1 patient, who had actually developed HIT according to the clinical history. Epitope mapping showed that 1E12 interacts with 5 key amino acids on PF4, of which 4 are also required for the binding of human VITT antibodies, thus explaining the competitive inhibition. CONCLUSION: A simple competitive anti-PF4 EIA with 1E12 could help confirm VITT diagnosis and distinguish it from HIT in patients when both diagnoses are possible.
Assuntos
Anticorpos Monoclonais , Vacinas contra COVID-19 , Heparina , Fator Plaquetário 4 , Humanos , Fator Plaquetário 4/imunologia , Heparina/efeitos adversos , Heparina/imunologia , Anticorpos Monoclonais/imunologia , Anticorpos Monoclonais/efeitos adversos , Vacinas contra COVID-19/efeitos adversos , Vacinas contra COVID-19/imunologia , Imunoglobulina G/sangue , Imunoglobulina G/imunologia , Valor Preditivo dos Testes , Anticoagulantes/efeitos adversos , Anticoagulantes/imunologia , COVID-19/imunologia , COVID-19/prevenção & controle , COVID-19/diagnóstico , Fragmentos Fab das Imunoglobulinas/imunologia , Fragmentos Fab das Imunoglobulinas/efeitos adversos , Ligação Proteica , Púrpura Trombocitopênica Idiopática/imunologia , Púrpura Trombocitopênica Idiopática/diagnóstico , Púrpura Trombocitopênica Idiopática/induzido quimicamente , SARS-CoV-2/imunologia , Ligação Competitiva , Púrpura Trombocitopênica Trombótica/imunologia , Púrpura Trombocitopênica Trombótica/diagnóstico , Púrpura Trombocitopênica Trombótica/sangue , Púrpura Trombocitopênica Trombótica/induzido quimicamenteAssuntos
Autoanticorpos , Fator Plaquetário 4 , Púrpura Trombocitopênica Idiopática , Humanos , Adenoviridae , Anticorpos Antivirais/sangue , Autoanticorpos/sangue , Autoanticorpos/imunologia , Fator Plaquetário 4/imunologia , Púrpura Trombocitopênica Idiopática/etiologia , Púrpura Trombocitopênica Idiopática/imunologia , ChAdOx1 nCoV-19/efeitos adversos , ChAdOx1 nCoV-19/imunologia , Ad26COVS1/efeitos adversos , Ad26COVS1/imunologia , Infecções por Adenovirus Humanos/complicações , Infecções por Adenovirus Humanos/imunologia , Infecções por Adenovirus Humanos/virologiaAssuntos
Hemorragias Intracranianas , Fator Plaquetário 4 , Trombose dos Seios Intracranianos , Trombocitopenia , Humanos , Trombose dos Seios Intracranianos/diagnóstico por imagem , Trombose dos Seios Intracranianos/complicações , Trombocitopenia/complicações , Trombocitopenia/diagnóstico , Hemorragias Intracranianas/diagnóstico por imagem , Hemorragias Intracranianas/etiologia , Hemorragias Intracranianas/diagnóstico , Fator Plaquetário 4/imunologia , Feminino , Autoanticorpos/sangue , Masculino , AdultoRESUMO
BACKGROUNDFeatures of consumptive coagulopathy and thromboinflammation are prominent in cerebral malaria (CM). We hypothesized that thrombogenic autoantibodies contribute to a procoagulant state in CM.METHODSPlasma from children with uncomplicated malaria (UM) (n = 124) and CM (n = 136) was analyzed by ELISA for a panel of 8 autoantibodies including anti-platelet factor 4/polyanion (anti-PF4/P), anti-phospholipid, anti-phosphatidylserine, anti-myeloperoxidase, anti-proteinase 3, anti-dsDNA, anti-ß-2-glycoprotein I, and anti-cardiolipin. Plasma samples from individuals with nonmalarial coma (NMC) (n = 49) and healthy controls (HCs) (n = 56) were assayed for comparison. Associations with clinical and immune biomarkers were determined using univariate and logistic regression analyses.RESULTSMedian anti-PF4/P and anti-PS IgG levels were elevated in individuals with malaria infection relative to levels in HCs (P < 0.001) and patients with NMC (PF4/P: P < 0.001). Anti-PF4/P IgG levels were elevated in children with CM (median = 0.27, IQR: 0.19-0.41) compared with those with UM (median = 0.19, IQR: 0.14-0.22, P < 0.0001). Anti-PS IgG levels did not differ between patients with UM and those with CM (P = 0.39). When patients with CM were stratified by malaria retinopathy (Ret) status, the levels of anti-PF4/P IgG correlated negatively with the peripheral platelet count in patients with Ret+ CM (Spearman's rho [Rs] = 0.201, P = 0.04) and associated positively with mortality (OR = 15.2, 95% CI: 1.02-275, P = 0.048). Plasma from patients with CM induced greater platelet activation in an ex vivo assay relative to plasma from patients with UM (P = 0.02), and the observed platelet activation was associated with anti-PF4/P IgG levels (Rs= 0.293, P = 0.035).CONCLUSIONSThrombosis mediated by elevated anti-PF4/P autoantibodies may be one mechanism contributing to the clinical complications of CM.
Assuntos
Autoanticorpos , Malária Cerebral , Fator Plaquetário 4 , Humanos , Malária Cerebral/imunologia , Malária Cerebral/sangue , Autoanticorpos/sangue , Autoanticorpos/imunologia , Feminino , Masculino , Fator Plaquetário 4/imunologia , Fator Plaquetário 4/sangue , Criança , Pré-Escolar , Lactente , Polieletrólitos , Trombose/imunologia , Trombose/sangueRESUMO
BACKGROUND AND OBJECTIVES: Vaccine-induced thrombotic thrombocytopenia (VITT) is a rare adverse effect characterized by thrombocytopenia and thrombosis occurring after COVID-19 vaccination. VITT pathophysiology is not fully unravelled but shows similarities to heparin-induced thrombocytopenia (HIT). HIT is characterized by the presence of antibodies against platelet factor 4 (PF4)/heparin complex, which can activate platelets in an FcγRIIa-dependent manner, whereas IgG-antibodies directed against PF4 play an important role in VITT. MATERIALS AND METHODS: We characterized all clinically suspected VITT cases in the Netherlands from a diagnostic perspective and hypothesized that patients who developed both thrombocytopenia and thrombosis display underlying mechanisms similar to those in HIT. We conducted an anti-PF4 ELISA and a functional PF4-induced platelet activation assay (PIPAA) with and without blocking the platelet-FcγRIIa and found positivity in both tests, suggesting VITT with mechanisms similar to those in VITT. RESULTS: We identified 65 patients with both thrombocytopenia and thrombosis among 275 clinically suspected VITT cases. Of these 65 patients, 14 (22%) tested positive for anti-PF4 and PF4-dependent platelet activation. The essential role of platelet-FcγRIIa in VITT with mechanisms similar to those in HIT was evident, as platelet activation was inhibited by an FcγRIIa-blocking antibody in all 14 patients. CONCLUSION: Our study shows that only a small proportion of clinically suspected VITT patients with thrombocytopenia and thrombosis have anti-PF4-inducing, FcɣRIIa-dependent platelet activation, suggesting an HIT-like pathophysiology. This leaves the possibility for the presence of another type of pathophysiology ('non-HIT like') leading to VITT. More research on pathophysiology is warranted to improve the diagnostic algorithm and to identify novel therapeutic and preventive strategies.
Assuntos
Vacinas contra COVID-19 , Ativação Plaquetária , Fator Plaquetário 4 , Receptores de IgG , Trombocitopenia , Trombose , Humanos , Países Baixos , Fator Plaquetário 4/imunologia , Feminino , Masculino , Pessoa de Meia-Idade , Trombocitopenia/induzido quimicamente , Trombocitopenia/diagnóstico , Trombocitopenia/sangue , Trombose/sangue , Trombose/imunologia , Trombose/diagnóstico , Trombose/etiologia , Vacinas contra COVID-19/efeitos adversos , Vacinas contra COVID-19/imunologia , Ativação Plaquetária/imunologia , Adulto , Idoso , COVID-19 , Heparina/efeitos adversos , Plaquetas/imunologia , Plaquetas/metabolismo , Imunoglobulina G/sangueRESUMO
Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare but dangerous side effect of adenoviral-vectored COVID-19 vaccines. VITT had been linked to production of autoantibodies recognizing platelet factor 4 (PF4). Here, we characterize anti-PF4 antibodies obtained from a VITT patient's blood. Intact mass measurements indicate that a significant fraction of these antibodies represent a limited number of clones. MS analysis of large antibody fragments (the light chain and the Fc/2 and Fd fragments of the heavy chain) confirms the monoclonal nature of this component of the anti-PF4 antibodies repertoire and reveals the presence of a mature complex biantennary N-glycan within the Fd segment. Peptide mapping using two complementary proteases and LC-MS/MS was used to determine the amino acid sequence of the entire light chain and over 98% of the heavy chain (excluding a short N-terminal segment). The sequence analysis allows the monoclonal antibody to be assigned to the IgG2 subclass and verifies that the light chain belongs to the λ-type. Incorporation of enzymatic de-N-glycosylation into the peptide mapping routine allows the N-glycan in the Fab region of the antibody to be localized to the framework 3 region of the VH domain. This novel N-glycosylation site is the result of a single mutation within the germline sequence. Peptide mapping also provides information on lower-abundance (polyclonal) components of the anti-PF4 antibody ensemble, revealing the presence of all four subclasses (IgG1-IgG4) and both types of the light chain (λ and κ). This case study demonstrates the power of combining the intact, middle-down, and bottom-up MS approaches for meaningful characterization of ultralow quantities of pathogenic antibodies extracted directly from patients' blood.
Assuntos
Fator Plaquetário 4 , Humanos , Fator Plaquetário 4/imunologia , Fator Plaquetário 4/química , Vacinas contra COVID-19/efeitos adversos , Vacinas contra COVID-19/imunologia , Vacinas contra COVID-19/química , Autoanticorpos/imunologia , Autoanticorpos/sangue , Anticorpos Monoclonais/imunologia , Anticorpos Monoclonais/química , Sequência de Aminoácidos , Púrpura Trombocitopênica Trombótica/induzido quimicamente , Púrpura Trombocitopênica Trombótica/imunologiaRESUMO
INTRODUCTION: Fcγ-receptors (FcγR) are membrane receptors expressed on a variety of immune cells, specialized in recognition of the Fc part of immunoglobulin G (IgG) antibodies. FcγRIIA-dependent platelet activation in platelet factor 4 (PF4) antibody-related disorders have gained major attention, when these antibodies were identified as the cause of the adverse vaccination event termed vaccine-induced immune thrombocytopenia and thrombosis (VITT) during the COVID-19 vaccination campaign. With the recognition of anti-PF4 antibodies as cause for severe spontaneous and sometimes recurrent thromboses independent of vaccination, their clinical relevance extended far beyond heparin-induced thrombocytopenia (HIT) and VITT. AREAS COVERED: Patients developing these disorders show life-threatening thromboses, and the outcome is highly dependent on effective treatment. This narrative literature review summarizes treatment options for HIT and VITT that are currently available for clinical application and provides the perspective toward new developments. EXPERT OPINION: Nearly all these novel approaches are based on in vitro, preclinical observations, or case reports with only limited implementation in clinical practice. The therapeutic potential of these approaches still needs to be proven in larger cohort studies to ensure treatment efficacy and long-term patient safety.
Assuntos
Vacinas contra COVID-19 , Heparina , Receptores de IgG , Trombocitopenia , Trombose , Humanos , Anticoagulantes/efeitos adversos , COVID-19/complicações , COVID-19/prevenção & controle , COVID-19/imunologia , Vacinas contra COVID-19/efeitos adversos , Vacinas contra COVID-19/imunologia , Heparina/efeitos adversos , Ativação Plaquetária/efeitos dos fármacos , Fator Plaquetário 4/imunologia , Púrpura Trombocitopênica Idiopática/induzido quimicamente , Púrpura Trombocitopênica Idiopática/imunologia , Púrpura Trombocitopênica Idiopática/tratamento farmacológico , Receptores de IgG/metabolismo , Receptores de IgG/imunologia , Trombocitopenia/induzido quimicamente , Trombocitopenia/imunologia , Tromboinflamação/tratamento farmacológico , Trombose/tratamento farmacológico , Trombose/imunologiaRESUMO
Hematology is a clinical specialty with strong roots in the laboratory; accordingly, the lab can help solve perplexing clinical problems. This review highlights clinical-pathological conundrums addressed during my 35-year hematology career at McMaster University. Heyde syndrome is the association between aortic stenosis and bleeding gastrointestinal (GI) angiodysplasia where the bleeding is usually cured by aortic valve replacement; the chance reading of a neonatal study showing reversible deficiency of high-molecular-weight (HMW) multimers of von Willebrand factor (vWF) following surgical correction of congenital heart disease provided the key insight that a subtle deficiency of HMW multimers of vWF explains Heyde syndrome. The unusual immunobiology of heparin-induced thrombocytopenia (HIT)-a highly prothrombotic, antibody-mediated, anti-platelet factor 4 (PF4) disorder featuring rapid appearance and then disappearance (seroreversion) of the pathological heparin-dependent platelet-activating antibodies-permitted identification of key clinical features that informed development of a scoring system (4Ts) to aid in HIT diagnosis. Atypical clinical presentations of HIT prompted identification of heparin-independent anti-PF4 antibodies, now recognized as the explanation for vaccine-induced immune thrombotic thrombocytopenia (VITT), as well as VITT-like disorders triggered by adenovirus infection. Another unusual feature of HIT is its strong association with limb ischemia, including limb necrosis secondary to deep-vein/microvascular thrombosis (venous limb gangrene). The remarkable observation that supratherapeutic warfarin anticoagulation predisposes to HIT- and cancer-associated venous limb gangrene provided insight into disturbed procoagulant/anticoagulant balance; these concepts are relevant to microvascular thrombosis in critical illness (symmetrical peripheral gangrene), including a pathophysiological role for proximate "shock liver" (impaired hepatic synthesis of natural anticoagulants).
Assuntos
Fator Plaquetário 4 , Humanos , Fator Plaquetário 4/imunologia , Fator Plaquetário 4/metabolismo , Necrose , Isquemia/etiologia , Isquemia/patologia , Isquemia/metabolismo , Heparina/efeitos adversos , Estenose da Valva Aórtica , Trombocitopenia/etiologia , Trombocitopenia/patologia , Autoanticorpos/imunologiaRESUMO
Heparin-induced thrombocytopenia (HIT) is rare, affecting fewer than 1 in 1500 hospital admissions. Despite the increasing adoption of new therapies in HIT, such as direct oral anticoagulants and pooled immunoglobulins, there is limited high-quality evidence to guide clinicians. Numerous uncommon presentations of HIT and HIT-like entities have recently been recognized, and a harmonized approach to their classification is required to study them better. We present the results of an international survey of opinions from experts and practitioners in the field of platelet immunology regarding the role of direct oral anticoagulants in HIT, novel definitions of subclassifications of HIT-like platelet factor 4 immune conditions (spontaneous autoimmune HIT, persistent autoimmune HIT, and treatment-refractory HIT), and the role for intravenous immunoglobulins in the treatment paradigm of HIT and these HIT-like conditions. From 102 survey responses, there was broad acceptance of rivaroxaban (74.5%) and apixaban (73.5%) even before platelet recovery, as well as for intravenous immunoglobulin in the management of spontaneous (85.6%), persistent (83.7%), and treatment-refractory HIT (87.4%). With this mandate for harmonizing terminologies and treatment approaches in special situations without robust clinical data owing to their rarity, we plan to conduct a robust survey, establish international consensus, and draft management guidelines for HIT and platelet factor 4 immune diseases in the near future.
Assuntos
Anticoagulantes , Heparina , Imunoglobulinas Intravenosas , Fator Plaquetário 4 , Trombocitopenia , Humanos , Heparina/efeitos adversos , Heparina/imunologia , Imunoglobulinas Intravenosas/uso terapêutico , Imunoglobulinas Intravenosas/efeitos adversos , Trombocitopenia/induzido quimicamente , Trombocitopenia/imunologia , Trombocitopenia/diagnóstico , Anticoagulantes/efeitos adversos , Fator Plaquetário 4/imunologia , Inquéritos e Questionários , Pirazóis/efeitos adversos , Pirazóis/uso terapêutico , Plaquetas/imunologia , Plaquetas/efeitos dos fármacos , Plaquetas/metabolismo , Piridonas/efeitos adversos , Piridonas/uso terapêutico , Rivaroxabana/efeitos adversos , Púrpura Trombocitopênica Idiopática/induzido quimicamente , Púrpura Trombocitopênica Idiopática/imunologia , Púrpura Trombocitopênica Idiopática/diagnóstico , Púrpura Trombocitopênica Idiopática/sangue , Púrpura Trombocitopênica Idiopática/tratamento farmacológico , Pesquisas sobre Atenção à Saúde , Terminologia como AssuntoAssuntos
Fator Plaquetário 4 , Púrpura Trombocitopênica Idiopática , Trombose , Humanos , Trombose/etiologia , Trombose/imunologia , Trombose/sangue , Feminino , Púrpura Trombocitopênica Idiopática/imunologia , Púrpura Trombocitopênica Idiopática/sangue , Púrpura Trombocitopênica Idiopática/induzido quimicamente , Masculino , Fator Plaquetário 4/imunologia , Pessoa de Meia-Idade , Adulto , Autoanticorpos/sangue , Autoanticorpos/imunologia , IdosoRESUMO
INTRODUCTION: Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a highly prothrombotic reaction to COVID-19 (coronavirus disease 2019) adenoviral vector vaccines. Its distinct bleeding and thrombotic patterns compared with other platelet consumptive disorders remain unclear. METHODS: We performed a systematic review of the literature (PubMed and Embase) up to July 31, 2022, including case reports and case series providing nonaggregate data of VITT patients. Accurate VITT diagnosis required fulfillment of the following criteria: (1) endorsement by the authors, (2) consistent vaccine type and timing, (3) presence of thrombocytopenia and thrombosis, (4) detection of anti-platelet factor 4 antibodies. Data are presented as frequencies with 95% confidence intervals (CIs) calculated with the exact binomial method. RESULTS: We retrieved 143 eligible studies, describing 366 patients. Of 647 thrombotic events, 53% (95% CI: 49-56) were venous thromboses at unusual sites and 30% (95% CI: 27-34) were cerebral venous sinus thromboses (CVSTs). The ratio of venous-to-arterial events was 4.1. Thromboses in most sites were associated with at least another thrombotic event, with the exception of CVST and CNS arterial thrombosis (isolated in 49 and 39% of cases, respectively). Bleeding occurred in 36% (95% CI: 31-41) of patients; 68% (95% CI: 59-75) of bleeding events were intracranial hemorrhages (ICHs). Overall mortality was 24% (95% CI: 19-29), and 77% (95% CI: 58-90) in patients with isolated CVST complicated by ICH. CONCLUSION: VITT displays a venous-to-arterial thrombosis ratio comparable to heparin-induced thrombocytopenia. However, VITT is characterized by a higher prevalence of CVST and ICH, which contribute to the increased bleeding frequency and mortality.
Assuntos
Vacinas contra COVID-19 , COVID-19 , Hemorragia , Humanos , Anticoagulantes/efeitos adversos , Relatos de Casos como Assunto , COVID-19/complicações , Vacinas contra COVID-19/efeitos adversos , Fator Plaquetário 4/imunologia , Fatores de Risco , SARS-CoV-2/imunologia , Trombose dos Seios Intracranianos/etiologia , Trombose/etiologia , Trombose VenosaRESUMO
Intermittent hemodialysis (HD) is almost invariably performed with heparin, and thus HD patients are at risk of developing the immune-mediated adverse effect heparin-induced thrombocytopenia (HIT), caused by anti-platelet factor 4/heparin IgG, which strongly activates platelets. HIT patients develop hypercoagulability with greatly increased risk of thrombosis, both venous and arterial. Certain HIT-associated complications are more likely to develop among HD patients, including hemofilter thrombosis despite heparin, intravascular catheter and/or arteriovenous fistula-associated thrombosis, post-heparin bolus anaphylactoid/anaphylactic reactions, and thrombotic stroke and acute limb artery thrombosis (reflecting the high frequency of underlying arteriopathy in many patients with renal failure). Management of HIT in HD usually requires use of an alternative (non-heparin) anticoagulant; for example, danaparoid sodium (outside the USA) or argatroban (USA and elsewhere). Whether heparin-grafted hemodialyzers (without systemic heparin) can be used safely in acute HIT is unknown. The HIT immune response is remarkably transient and usually not retriggered by subsequent heparin administration. Accordingly, since renal failure patients often require long-term HD, there may be the opportunity-following seroreversion (loss of platelet-activating HIT antibodies)-to restart heparin for HD, a practice that appears to have a low likelihood of retriggering HIT.
Assuntos
Anticoagulantes , Heparina , Diálise Renal , Trombocitopenia , Humanos , Heparina/efeitos adversos , Heparina/imunologia , Trombocitopenia/induzido quimicamente , Trombocitopenia/imunologia , Anticoagulantes/efeitos adversos , Anticoagulantes/imunologia , Fator Plaquetário 4/imunologia , Trombose/imunologia , Trombose/induzido quimicamenteRESUMO
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.
Assuntos
COVID-19 , Púrpura Trombocitopênica Idiopática , Trombocitopenia , Trombose , Vacinas , Anticorpos , Heparina/efeitos adversos , Humanos , Fator Plaquetário 4/imunologia , Trombocitopenia/induzido quimicamente , Trombocitopenia/diagnóstico , Trombose/etiologia , Vacinas/efeitos adversosRESUMO
Regulation of endosomal Toll-like receptor (TLR) responses by the chemokine CXCL4 is implicated in inflammatory and fibrotic diseases, with CXCL4 proposed to potentiate TLR responses by binding to nucleic acid TLR ligands and facilitating their endosomal delivery. Here we report that in human monocytes/macrophages, CXCL4 initiates signaling cascades and downstream epigenomic reprogramming that change the profile of the TLR8 response by selectively amplifying inflammatory gene transcription and interleukin (IL)-1ß production, while partially attenuating the interferon response. Mechanistically, costimulation by CXCL4 and TLR8 synergistically activates TBK1 and IKKε, repurposes these kinases towards an inflammatory response via coupling with IRF5, and activates the NLRP3 inflammasome. CXCL4 signaling, in a cooperative and synergistic manner with TLR8, induces chromatin remodeling and activates de novo enhancers associated with inflammatory genes. Our findings thus identify new regulatory mechanisms of TLR responses relevant for cytokine storm, and suggest targeting the TBK1-IKKε-IRF5 axis may be beneficial in inflammatory diseases.
Assuntos
Quinase I-kappa B , Fatores Reguladores de Interferon , Monócitos , Fator Plaquetário 4 , Proteínas Serina-Treonina Quinases , Receptor 8 Toll-Like , Epigênese Genética , Humanos , Quinase I-kappa B/genética , Quinase I-kappa B/imunologia , Quinase I-kappa B/metabolismo , Inflamação/genética , Inflamação/imunologia , Inflamação/metabolismo , Fatores Reguladores de Interferon/genética , Fatores Reguladores de Interferon/imunologia , Fatores Reguladores de Interferon/metabolismo , Macrófagos/imunologia , Macrófagos/metabolismo , Monócitos/imunologia , Monócitos/metabolismo , Fator Plaquetário 4/imunologia , Fator Plaquetário 4/metabolismo , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/imunologia , Proteínas Serina-Treonina Quinases/metabolismo , Receptor 8 Toll-Like/genética , Receptor 8 Toll-Like/imunologia , Receptor 8 Toll-Like/metabolismoRESUMO
Rare cases of thrombocytopenia and thrombosis after anti-COVID-19 adenovirus-associated mRNA vaccines (VITT) due to platelet-activating anti-platelet-factor 4 (PF4)/polyanion antibodies have been reported. VITT laboratory diagnosis, similarly to heparin-induced thrombocytopenia (HIT) diagnosis, requires immunoassays for anti-PF4/polyanion antibodies identification, such as ELISA assays and platelet-activating functional tests, such as heparin-induced platelet activation test (HIPA), to confirm their pathogenicity. We compared the flow cytometry (FC) measurement of platelet p-selectin exposure to the gold standard functional test HIPA for diagnosis confirmation in 13 patients with a clinical VITT syndrome (6M/7F; median age 56 (33-78)) who resulted positive to anti-PF4/polyanion antibodies ELISA assays (12/13). FC and HIPA similarly identified three different patterns: (1) a typical non-heparin-dependent VITT pattern (seven and six patients by FC and HIPA, respectively); (2) low/no platelet activation in patients under IvIg therapy (five out of five and two out of four patients by FC and HIPA, respectively); (3) a HIT pattern. Antibodies investigated by FC became negative after 7, 17, and 24 days of therapy in three patients. FC measurement of P-selectin exposure was as sensitive as HIPA but simpler to detect anti-PF4/polyanion antibodies in VITT patients. FC could reliably discriminate VITT from HIT, thus helping for the choice of the anticoagulant.
Assuntos
Anticorpos , Vacinas contra COVID-19 , Trombocitopenia , Trombose , Anticorpos/isolamento & purificação , Vacinas contra COVID-19/efeitos adversos , Citometria de Fluxo , Heparina , Humanos , Pessoa de Meia-Idade , Selectina-P , Fator Plaquetário 4/imunologia , Trombocitopenia/induzido quimicamente , Trombocitopenia/diagnóstico , Trombose/induzido quimicamente , Trombose/diagnósticoRESUMO
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.
Assuntos
ChAdOx1 nCoV-19/efeitos adversos , Heparina/efeitos adversos , Púrpura Trombocitopênica Idiopática/etiologia , Diálise Renal/efeitos adversos , Trombocitopenia/etiologia , Idoso , Anticoagulantes/efeitos adversos , Autoanticorpos/sangue , Diagnóstico Diferencial , Humanos , Imunoglobulina G/sangue , Lítio/toxicidade , Masculino , Contagem de Plaquetas , Fator Plaquetário 4/imunologia , Púrpura Trombocitopênica Idiopática/sangue , Púrpura Trombocitopênica Idiopática/diagnóstico , Diálise Renal/métodos , Trombocitopenia/sangue , Trombocitopenia/diagnósticoRESUMO
BACKGROUND: Antibodies against cationic platelet chemokine, platelet factor 4 (PF4/CXCL4), have been described in heparin-induced thrombocytopenia (HIT), but also in patients positive for antiphospholipid antibodies (aPL) even in the absence of heparin treatment and HIT-related clinical manifestations. Anti-PF4 antibodies have been recently described also in subjects who developed thrombosis with thrombocytopenia syndrome (TTS) in association with adenoviral vector-based, but not with mRNA-based, COVID-19 vaccines. OBJECTIVE: To investigate whether COVID-19 vaccination affects the production of anti-PF4 antibodies in aPL-positive patients and in control groups. METHODS: Anti-PF4 immunoglobulins were detected in patients' and controls' serum samples by ELISA and their ability to activate normal platelets was assessed by the platelet aggregation test. RESULTS: Anti-PF4 were found in 9 of 126 aPL-positive patients, 4 of 50 patients with COVID-19, 9 of 49 with other infections, and 1 of 50 aPL-negative patients with systemic lupus erythematosus. Clinical manifestations of TTS were not observed in any aPL patient positive for anti-PF4, whose serum failed to cause platelet aggregation. The administration of COVID-19 vaccines did not affect the production of anti-PF4 immunoglobulins or their ability to cause platelet aggregation in 44 aPL-positive patients tested before and after vaccination. CONCLUSIONS: Heparin treatment-independent anti-PF4 antibodies can be found in aPL-positive patients and asymptomatic carriers, but their presence, titre as well as in vitro effect on platelet activation are not affected by COVID-19 vaccination.