Antiplatelet Antibodies Research Articles

Efgartigimod alfa for the treatment of primary immune thrombocytopenia.

Primary immune thrombocytopenia (ITP) is an acquired autoimmune disorder characterized by isolated thrombocytopenia. Most patients with ITP have antiplatelet antibodies of the immunoglobulin G (IgG) subtype which through interaction with platelet and megakaryocyte glycoproteins result in increased platelet destruction and inhibition of platelet production. There are a variety of therapeutic options available for the treatment of ITP including corticosteroids, IVIgG, TPO-RA, rituximab, fostamatinib, and splenectomy. Long-term remissions with any of these therapies can vary widely and patients may require additional therapy. The neonatal Fc receptor (FcRn) plays a pivotal role in IgG and albumin physiology through recycling pathways. Efgartigimod is a human IgG1-derived fragment that has been modified by ABDEG technology to increase its affinity for FcRn at both physiologic and acidic pH. The binding of efgartigimod to FcRn blocks the interaction of IgG with FcRn facilitating increased lysosomal degradation of IgG and decreasing total IgG levels. Based on the mechanism of action and the known pathophysiology of ITP as well as the efficacy of other therapies such as intravenous immunoglobulin (IVIG), the use of efgartigimod in patients with ITP is attractive. This article will briefly discuss the pathophysiology of ITP, current treatments, and the data available on efgartigimod in ITP.

Whole Blood Procoagulant Platelet Flow Cytometry Protocol for Heparin-Induced Thrombocytopenia (HIT) and Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT) Testing.

Heparin-induced thrombocytopenia (HIT) is a well-characterized, iatrogenic complication of heparin anticoagulation with significant morbidity. In contrast, vaccine-induced immune thrombotic thrombocytopenia (VITT) is a recently recognized severe prothrombotic complication of adenoviral vaccines, including the ChAdOx1 nCoV-19 (Vaxzevria, AstraZeneca) and Ad26.COV2.S (Janssen, Johnson & Johnson) vaccines against COVID-19. The diagnosis of HIT and VITT involve laboratory testing for antiplatelet antibodies by immunoassays followed by confirmation by functional assays to detect platelet-activating antibodies. Functional assays are critical to detect pathological antibodies due to the varying sensitivity and specificity of immunoassays. This chapter presents a protocol for a novel whole blood flow cytometry-based assay to detect procoagulant platelets in healthy donor blood in response to plasma from patients suspected of HIT or VITT. A method to identify suitable healthy donors for HIT and VITT testing is also described.

The complexities of transfusion reactions: Coexistence of a delayed haemolytic transfusion reaction and post-transfusion purpura.

Immune-mediated acute or delayed transfusion reactions occur when there is immunological incompatibility between transfused blood products and recipient's antibodies. Acute haemolytic transfusion reactions occur within 24 h and are delayed after 24 h up to 10 days following transfusion, whereas post-transfusion purpura (PTP) typically occurs 7-10 days post-transfusion. We present a case of a previously transfused and recently post-partum female who developed both delayed haemolytic transfusion reaction (DHTR) and PTP. A 42-year-old woman, G2P1, with non-alcoholic liver disease, portal hypertension and previous transfusion history with allogeneic anti-E, developed a severe DHTR and PTP following a complicated post-partum course and multiple transfusions. The antenatal and initial post-partum pre-transfusion antibody screens were negative. Subsequently five red cell antibodies, including anti-c, anti-Fya, anti-Jkb and anti-S and the reappearance of anti-E were, however, identified during follow-up investigations along with the anti-platelet antibody HPA-3a and human leukocyte antigen class I antibodies. Anti-E, anti-Jkb and anti-S were eluted from the circulating red blood cells. To our knowledge, there have been only two other case reports of DHTR and PTP occurring in the same patient.

Real-World Study of the Use of Iguratimod to Treat Chronic/Refractory ITP

Introduction: Immune thrombocytopenia (ITP) is an acquired, organ-specific, autoimmune disease and one of the most common bleeding disorders that seriously endangers human health. Iguratimod is a small molecule compound that is widely used as a novel antirheumatic drug in the treatment of rheumatoid arthritis in China and Japan. Iguratimod inhibits the production of several inflammatory cytokines, including IL-1, IL-6, IL-8, and tumor necrosis factor (TNF), and reduces the production of immunoglobulins. Th1 and Th17 cell counts were significantly reduced in patients with rheumatoid arthritis after treatment with iguratimod. The low long-term remission rate of ITP makes the investigation of its pathogenesis and the search for new treatments important clinical problems to be solved. Abnormal T-cell function and anti-platelet antibody production play important roles in the pathogenesis of ITP, and iguratimod is a therapeutic agent that could potentially be used to treat ITP. Previous clinical studies have shown that iguratimod can increase platelet levels in patients with dry syndrome. The potential of iguratimod for treating anti-platelet antibody-mediated thrombocytopenia in mice with ITP by modulating T-cell differentiation suggests that iguratimod may be a new approach for the prevention and treatment of ITP. Recent retrospective clinical studies and case reports have also shown that the use of iguratimod in autoimmune diseases is associated with good safety and efficacy. In conclusion, the aim of this study was to investigate the effect of iguratimod on the treatment of ITP. Methods: The study began in December 2020 and is ongoing. A total of 76 patients who were treated with iguratimod for at least 3 months were selected. Of these, 51 patients were treated for more than 6 months, and 30 patients were treated for at least 12 months. Five patients withdrew from observation after 3 months: two patients due to NR, three patients due to epidemic and financial reasons, and no patients due to AE. Key secondary endpoints included initial response by Day 14 (OR, platelet count ≥30×109/L, at least a 2-fold increase in baseline platelet count, and absence of bleeding; and CR, platelet count ≥ 100×109/L), duration of response, bleeding scores, and adverse events (AEs). This study was registered with ClinicalTrials.gov (). Results: At baseline, 73.5% of the patients reported symptoms of grade 1 to 4 bleeding. After 3 months of treatment, the proportion of patients with any bleeding symptoms decreased to 61.8% and remained below baseline throughout the study period. At baseline, 63 patients reported the use of concomitant medications, which decreased by 36.5% between 3 and 6 months. The most frequently discontinued or reduced medications were glucocorticoids and rituximab. All the patients took the medication in strict accordance with the instructions and medical advice. The patients were monitored monthly to assess blood, liver, kidney function, and no abnormalities in laboratory tests, such as elevated transaminases or lymphocytopenia, were observed. Conclusions: Iguratimod has good efficacy and safety in the treatment of ITP and has the potential to become a new treatment for ITP.

Sars-Cov-2 Vaccination in Pre-Existing and De Novo ITP: A Single Center Experience with Long-Term Follow-up

Introduction: SARS-CoV-2 vaccines can induce de novo immune thrombocytopenia (ITP) and worsen pre-existing ITP. Almost all cases of vaccine-induced or -exacerbated ITP respond to ITP therapies. We investigated longer-term outcomes of patients with ITP de novo or relapsed post-SARS-CoV-2 vaccination requiring treatment. We included outcomes following SARS-CoV-2 booster vaccines and considered that some post-vaccination relapses may NOT be related to vaccination. Methods: This is a single-center retrospective study of patients ≥18 years old with pre-existing ITP or de novo ITP following SARS-CoV-2 vaccination seen at The Center for Blood Disorders at New York-Presbyterian/Weill Cornell Medicine from January 2021 to May 2022. We included consecutive ITP patients with at least one platelet count following initial SARS-CoV-2 vaccinations or boosters. The study was approved by the NYP-WCM Institutional Review Board. An "ITP exacerbation” was defined as: a) ≥50% decline in platelet count from pre-vaccination baseline; b) >20% decline from pre-vaccination baseline to a platelet nadir <30x109/L; and/or c) receiving rescue therapy for ITP. Results: Among 95 patients with pre-existing ITP, sixteen (17%) experienced at least one ITP exacerbation after one (or several) SARS-CoV-2 vaccinations. Ten of 84 (12%) had an ITP exacerbation after dose#1. Among these, 7 experienced another exacerbation: 6 after dose#2 (with 3 receiving boosters, all without exacerbation) and 1 only after a booster. Of the remaining 3 who had had an ITP exacerbation after dose#1, 2 tolerated dose#2, and 1 was not re-challenged. Seventy-four received dose#2 of a SARS-CoV-2 vaccine. Nine (12%) experienced ITP exacerbations, including 6 who also had exacerbations following dose#1. Three tolerated dose#1 and an ITP exacerbation following dose#2. Two of these patients received booster vaccines, with 1 experiencing another ITP exacerbation. Of 24 patients who received at least one booster, 5 (21%) had ITP exacerbations after their boosters. While 3 of the 5 patients had tolerated previous vaccinations well, 1 had had an exacerbation following dose#1 and 1 following dose#2. Eleven of 16 patients experiencing ITP exacerbation(s) following SARS-CoV-2 vaccine(s) received rescue treatment, of whom seven (64%) had difficult-to-control ITP on chronic treatment, including intravenous immune globulin (IVIG) every 2 to 8 weeks. All responded to rescue treatment; the frequency of intermittent IVIG infusions did not increase following SARS-CoV-2 vaccination. Excluding these 7 whose ITP exacerbations were possibly not related to vaccination, 5/77 (6.5%) patients had exacerbations after dose #1, 4/68 (5.9%) after dose #2, and 4/20 (20%) after a booster. Four patients had exacerbations after more than 1 vaccination. Six patients had presumed de novo ITP post-SARS-CoV-2 vaccine: 2 females, 4 males, median age 35 years (range 30-72), and median follow-up 11 months (range 3-15) post ITP diagnosis. All presented with mucocutaneous bleeding and a median platelet count of 4 x109/L (1-29x109/L) at a median of 12 days post-vaccination (range 1-21). De novo ITP developed following dose#1 in 4 patients (mRNA-1273 = 2, BNT162b2 mRNA COVID-19 = 1, Ad26COV2 =1) and a first booster vaccine in 2 (BNT162b2 mRNA COVID-19). All 6 responded to IVIG and corticosteroids; 3 did not require further treatment remaining in complete response (CR) at 7-15 months post-vaccination. One completed a steroid taper and remains in CR 1 month off steroids; the other 2 patients remain on TPO-RA in on-treatment CR - at 3 and 12 months, 1 being tapered. Two received additional doses of the same vaccine and did well, both in CR off treatment up to 15 months since the initial diagnosis of ITP. Conclusions: ITP exacerbations and de novo ITP can occur with subsequent vaccination doses (including boosters) of the SARS-CoV-2 vaccine despite tolerance to previous doses. Conversely, many tolerate subsequent doses well, implying that the mechanism is unlikely to involve the generation of anti-platelet antibodies. Furthermore, in certain patients, ITP "exacerbations” may not be due to the vaccination but part of the course of their ITP. ITP exacerbation post-SARS-CoV-2 vaccination does not seem to cause lasting change in the state of the ITP on follow-up. Cases of de novo ITP generally responded well to standard treatments for ITP and, in our small cohort, had favorable longer-term outcomes.

Enhancing regulatory T-cell function via inhibition of high mobility group box 1 protein signaling in immune thrombocytopenia.

Primary immune thrombocytopenia (ITP) is the most common acquired autoimmune bleeding disorder. Abnormally increased levels of High Mobility Group Box 1 (HMGB1) protein associate with thrombocytopenia and therapeutic outcome in ITP. Previous studies proposed that a natural inhibitor of HMGB1, 18β-glycyrrhetinic acid (18β-GA), could be used for its anti-inflammatory and immune-modulatory effects, although its ability to correct immune balance in ITP is unclear. In this study, we showed that plasma HMGB1 correlated negatively with platelet counts in ITP patients, and confirmed that 18β-GA stimulated the production of regulatory T cells (Treg), restored the balance of CD4+ T-cell subsets and enhanced the suppressive function of Treg through blocking the effect on HMGB1 in patients with ITP. HMGB1 short hairpin RNA interference masked the effect of 18β-GA in Treg of ITP patients. Furthermore, we found that 18β-GA alleviated thrombocytopenia in mice with ITP. Briefly, anti-CD61 immune-sensitized splenocytes were transferred into severe combined immunodeficient mice to induce a murine model of severe ITP. The proportion of circulating Treg increased significantly, while the level of plasma HMGB1 and serum antiplatelet antibodies decreased significantly in ITP mice along 18β-GA treatment. In addition, 18β-GA reduced phagocytic activity of macrophages towards platelets both in ITP patients and ITP mice. These results indicate that 18β-GA has the potential to restore immune balance in ITP via inhibition of HMGB1 signaling. In short, this study reveals the role of HMGB1 in ITP, which may serve as a potential target for thrombocytopenia therapy.

Idiopathic thrombocytopenic purpura in tuberculosis (Case Report)

Tuberculosis (TB) is a contagious disease in both developing and developed countries. The incidence is increasing due to bacilli resistant to many drugs and the human immunodeficiency virus (HIV). Since 2012, India has the highest incidence of the disease at around 2.2 million cases, accounting for 26% of the global incidence according to World Health Organization statistics. A wide range of hematological manifestations is observed in TB, where thrombocytopenia is common in miliary TB and thrombocytosis in pulmonary TB. Immune thrombocytopenic purpura (ITP) is characterized by a low platelet count accompanied by the presence of autoantibodies. The association of immune thrombocytopenic purpura and tuberculosis is a rare condition. In the case presented, anti-tuberculosis therapy was effective for both tuberculosis and thrombocytopenia, suggesting a causal link between tuberculosis and immune thrombocytopenic purpura. Purpose: Reporting a case of association of PTI and TBC Method: Clinical case study and correlation with literature Discussion: The pathophysiology of thrombocytopenia in tuberculosis remains unanswered. This is a rare condition, estimated to occur in less than 1% of tuberculosis cases. Mycobacterium tuberculosis can break down the antigen with platelets leading to the formation of antiplatelet antibodies. HLA-specific presentation of tuberculosis may also lead to an antiplatelet immune response in some patients.

Expression of B-cell activating factor in pediatric patients with immune thrombocytopenia: a single institutional series and review of literature

ABSTRACT B-cell-activating factor (BAFF) is a crucial cytokine supporting survival and differentiation of B cells. Dysregulation of BAFF is involved in the pathogenesis of B-cell related autoimmune diseases including immune thrombocytopenia (ITP). The aim of this study was to evaluate the significance of BAFF expression in pediatric ITP patients. Eighty pediatric patients with ITP are subdivided in three groups. Group I included (32 patients) diagnosed with acute ITP less than 3 months, group II (48 patients) diagnosed with persistent ITP (from 3 to 12 months) and chronic ITP (more than 12 months) and group III 20 healthy controls. Complete blood picture, autoimmune profile, antiplatelet antibodies, coagulation profile, bone marrow examination, and RT-PCR were performed to detect the expression for BAF for all participants in this study. BAFF expression levels significantly increased in cases rather than in controls. BAFF Expression Value significantly increased in groups I & II (3.10 ± 1.99&3.29 ± 2.58) compared to controls (0.83 ± 0.45) as p < .001 for both. On the other hand, groups I & II were comparable in BAFF Expression Value (p = .470). BAFF expression increased in ITP patients, implying a function in the disease’s pathogenesis.

Temporal in vivo platelet labeling in mice reveals age-dependent receptor expression and conservation of specific mRNAs

AbstractThe proportion of young platelets, also known as newly formed or reticulated, within the overall platelet population has been clinically correlated with adverse cardiovascular outcomes. However, our understanding of this is incomplete because of limitations in the technical approaches available to study platelets of different ages. In this study, we have developed and validated an in vivo temporal labeling approach using injectable fluorescent antiplatelet antibodies to subdivide platelets by age and assess differences in functional and molecular characteristics. With this approach, we found that young platelets (<24 hours old) in comparison with older platelets respond to stimuli with greater calcium flux and degranulation and contribute more to the formation of thrombi in vitro and in vivo. Sequential sampling confirmed this altered functionality to be independent of platelet size, with distribution of sizes of tracked platelets commensurate with the global platelet population throughout their 5-day lifespan in the circulation. The age-associated decrease in thrombotic function was accompanied by significant decreases in the surface expression of GPVI and CD31 (PECAM-1) and an increase in CD9. Platelet messenger RNA (mRNA) content also decreased with age but at different rates for individual mRNAs indicating apparent conservation of those encoding granule proteins. Our pulse-chase–type approach to define circulating platelet age has allowed timely reexamination of commonly held beliefs regarding size and reactivity of young platelets while providing novel insights into the temporal regulation of receptor and protein expression. Overall, future application of this validated tool will inform age-based platelet heterogeneity in physiology and disease.

Transient pseudothrombocytopenia (PTCP) in the neonate due to the mother.

Thrombocytopenia with platelet count <50×109/L is common laboratory finding in a severely ill newborn in neonatal intensive care units (ICU). Neonates with severe thrombocytopenia are at risk of bleeding. Most dangerous is intracerebral hemorrhage (ICH) frequently leading to death or lifelong neurological sequels. Pseudothrombocytopenia (PTCP) is a rare in vitro phenomenon of falsely low platelet count determined on hematology analyzers due to platelet clumping in ethylenediaminetetraacetic acid (EDTA) anticoagulated blood. PTCP was also reported in pregnant women with isolated thrombocytopenia. EDTA-PTCP in the neonate due to the transplacental transmission of maternal antibodies has been reported only in a few cases. Although PTCP is rare phenomenon, it should always be excluded in newborns with isolated thrombocytopenia to avoid erroneous interpretation of platelet and leukocyte count, unnecessary laboratory investigation of false positive antiplatelet antibodies and needless platelet transfusions. We report on two cases of transient PTCP in a neonate due to transplacental transfer of maternal EDTA-dependent autoantibodies of IgG class from the same mother.

Immune-Mediated Neonatal Thrombocytopenia.

Immune-mediated thrombocytopenia in neonates is caused by the transplacental passage of maternally derived antiplatelet antibodies. The 2 most common causes include neonatal alloimmune thrombocytopenia, which leads to significant thrombocytopenia and risk of intracranial hemorrhage, and autoimmune thrombocytopenia, which is generally less severe. No specific guidelines for prenatal management exist for either disease; however, intravenous immune globulin treatments and systemic steroids for women with at-risk pregnancies can be useful in both diseases. In this review, we discuss the current literature and management strategies for both pregnant women and newborns with immune-mediated thrombocytopenia.

Idiopathic Thrombocytopenic Purpura in Tuberculosis

Tuberculosis (TB) is a contagious disease in both developing and developed countries. The incidence is increasing due to bacilli resistant to many drugs and the human immunodeficiency virus (HIV). Since 2012, India has the highest incidence of the disease at around 2.2 million cases, accounting for 26% of the global incidence according to World Health Organization statistics. A wide range of hematological manifestations is observed in TB, where thrombocytopenia is common in miliary TB and thrombocytosis in pulmonary TB. Immune thrombocytopenic purpura (ITP) is characterized by a low platelet count accompanied by the presence of autoantibodies. The association of immune thrombocytopenic purpura and tuberculosis is a rare condition. In the case presented, anti-tuberculosis therapy was effective for both tuberculosis and thrombocytopenia, suggesting a causal link between tuberculosis and immune thrombocytopenic purpura. Purpose: Reporting a case of association of PTI and TBC Method: Clinical case study and correlation with literature Discussion: The pathophysiology of thrombocytopenia in tuberculosis remains unanswered. This is a rare condition, estimated to occur in less than 1% of tuberculosis cases. Mycobacterium tuberculosis can break down the antigen with platelets leading to the formation of antiplatelet antibodies. HLA-specific presentation of tuberculosis may also lead to antiplatelet immune response in some patients.

Anchoring IgG-degrading enzymes to the surface of platelets selectively neutralizes antiplatelet antibodies

AbstractImmune thrombocytopenia (ITP) is an acquired bleeding disorder characterized by immunoglobulin G (IgG)–mediated platelet destruction. Current therapies primarily focus on reducing antiplatelet antibodies using immunosuppression or increasing platelet production with thrombopoietin mimetics. However, there are no universally safe and effective treatments for patients presenting with severe life-threatening bleeding. The IgG-degrading enzyme of Streptococcus pyogenes (IdeS), a protease with strict specificity for IgG, prevents IgG-driven immune disorders in murine models, including ITP. In clinical trials, IdeS prevented IgG-mediated kidney transplant rejection; however, the concentration of IdeS used to remove pathogenic antibodies causes profound hypogammaglobulinemia, and IdeS is immunogenic, which limits its use. Therefore, this study sought to determine whether targeting IdeS to FcγRIIA, a low-affinity IgG receptor on the surface of platelets, neutrophils, and monocytes, would be a viable strategy to decrease the pathogenesis of antiplatelet IgG and reduce treatment-related complications of nontargeted IdeS. We generated a recombinant protein conjugate by site-specifically linking the C-terminus of a single-chain variable fragment from an FcγRIIA antibody, clone IV.3, to the N-terminus of IdeS (scIV.3-IdeS). Platelets treated with scIV.3-IdeS had reduced binding of antiplatelet IgG from patients with ITP and decreased platelet phagocytosis in vitro, with no decrease in normal IgG. Treatment of mice expressing human FcγRIIA with scIV.3-IdeS reduced thrombocytopenia in a model of ITP and significantly improved the half-life of transfused platelets expressing human FcγRIIA. Together, these data suggest that scIV.3-IdeS can selectively remove pathogenic antiplatelet IgG and may be a potential treatment for patients with ITP and severe bleeding.

Autoimmune Cytopenias in Common Variable Immunodeficiency Are a Diagnostic and Therapeutic Conundrum: An Update.

Common variable immunodeficiency (CVID) is the most common symptomatic primary immunodeficiency (PID). CVID is a heterogenous condition and clinical manifestations may vary from increased susceptibility to infections to autoimmune manifestations, granulomatous disease, polyclonal lymphoproliferation, and increased risk of malignancy. Autoimmune manifestations may, at times, be the first and only clinical presentation of CVID, resulting in diagnostic dilemma for the treating physician.Autoimmune cytopenias (autoimmune haemolytic anaemia and/or thrombocytopenia) are the most common autoimmune complications seen in patients with CVID. Laboratory investigations such as antinuclear antibodies, direct Coomb’s test and anti-platelet antibodies may not be useful in patients with CVID because of lack of specific antibody response. Moreover, presence of autoimmune cytopenias may pose a significant therapeutic challenge as use of immunosuppressive agents can be contentious in these circumstances. It has been suggested that serum immunoglobulins must be checked in all patients presenting with autoimmune cytopenia such as immune thrombocytopenia or autoimmune haemolytic anaemia.It has been observed that patients with CVID and autoimmune cytopenias have a different clinical and immunological profile as compared to patients with CVID who do not have an autoimmune footprint. Monogenic defects have been identified in 10-50% of all patients with CVID depending upon the population studied. Monogenic defects are more likely to be identified in patients with CVID with autoimmune complications. Common genetic defects that may lead to CVID with an autoimmune phenotype include nuclear factor kappa B subunit 1 (NF-kB1), Lipopolysaccharide (LPS)-responsive beige-like anchor protein (LRBA), cytotoxic T lymphocyte antigen 4 (CTLA4), Phosphoinositide 3-kinase (PI3K), inducible T-cell costimulatory (ICOS), IKAROS and interferon regulatory factor-2 binding protein 2 (IRF2BP2). In this review, we update on recent advances in pathophysiology and management of CVID with autoimmune cytopenias.

In vivo nanotracer for the detection of brain thrombi in an AD mouse model.

Background: Alzheimer’s disease (AD) is the most common cause of dementia. It is a multifactorial degenerative disease pathologically characterized by intracellular neurofibrillary tangles and extracellular deposition of amyloid. An early hemostatic dysregulation is also present and contributes to an increment in clot formation, leading to hypoperfusion, blood brain barrier disruption and neuronal loss. The detection of this prothrombotic state is of the upmost importance in diagnostic approaches to identify AD patients who would benefit from anticoagulation. Method: The aim of this project is to use an in vivo nanotracer for the detection of brain thrombi in an AD mouse model by fast pre-targeted positron emission tomography (PET) imaging. For that purpose, AD animals and their wild-type littermates were intravenously injected with the antiplatelet antibody against CD41 conjugated with transcyclooctene (TCO-antiCD41). Twenty-four hours later, [68Ga]core-doped iron oxide nanoparticles (NP) functionalized with tetrazine (TZ) were intravenously administered. TCO and TZ produce a rapid in vivo reaction by means of bioorthogonal chemistry, allowing to non-invasively evaluate platelets’ levels by PET. Two hours after [68Ga]NP-TZ injection, a static PET study of each mouse was acquired with a scanner for small animals (nanoScan® PET/CT, Mediso, USA). Finally, biodistribution assays of different organs after the PET study were performed. All PET images were analyzed by regions of interest and voxel-wise analyses. Conclusions: Our results provide a neuroimaging strategy to diagnose the prothrombotic state towards the personalization of anticoagulation treatment in AD patients.

Acute Tubular Necrosis and Thrombocytopenia Associated With Rifampin Use: Case Report and Review.

A case of rifampin-induced acute tubular necrosis requiring hemodialysis in a patient receiving thrice-weekly rifampin with daily dapsone for retreatment of relapsed Hansen’s disease is reported. The patient had positive rifampin-dependent antiplatelet antibodies. Case reports of acute renal failure associated with the use of rifampin are summarized.

Thrombocytopenia and splenic platelet-directed immune responses after IV ChAdOx1 nCov-19 administration

AbstractVaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are based on a range of novel platforms, with adenovirus-based approaches (like ChAdOx1 nCov-19) being one of them. Recently, a novel complication of SARS-CoV-2–targeted adenovirus vaccines has emerged: immune thrombocytopenia, either isolated, or accompanied by thrombosis (then termed VITT). This complication is characterized by low platelet counts, and in the case of VITT, also by platelet-activating platelet factor 4 antibodies reminiscent of heparin-induced thrombocytopenia, leading to a prothrombotic state with clot formation at unusual anatomic sites. Here, we detected antiplatelet antibodies targeting platelet glycoprotein receptors in 30% of patients with proven VITT (n = 27) and 42% of patients with isolated thrombocytopenia after ChAdOx1 nCov-19 vaccination (n = 26), indicating broad antiplatelet autoimmunity in these clinical entities. We use in vitro and in vivo models to characterize possible mechanisms of these platelet-targeted autoimmune responses leading to thrombocytopenia. We show that IV but not intramuscular injection of ChAdOx1 nCov-19 triggers platelet-adenovirus aggregate formation and platelet activation in mice. After IV injection, these aggregates are phagocytosed by macrophages in the spleen, and platelet remnants are found in the marginal zone and follicles. This is followed by a pronounced B-cell response with the emergence of circulating antibodies binding to platelets. Our work contributes to the understanding of platelet-associated complications after ChAdOx1 nCov-19 administration and highlights accidental IV injection as a potential mechanism of platelet-targeted autoimmunity. Hence, preventing IV injection when administering adenovirus-based vaccines could be a potential measure against platelet-associated pathologies after vaccination.

Hematological and Extra-Hematological Autoimmune Complications after Checkpoint Inhibitors.

Checkpoint inhibitors (CPI) represent a novel therapeutical strategy with a high efficacy both in solid and hematological cancers. They act by reactivating the immune system against neoplastic cells but may, in turn, cause immune-related adverse events (IRAEs) involving several organs with variable frequency and severity. Up to 10% of CPI-treated patients experience hematological IRAEs, mainly cytopenias. The differential diagnosis is challenging due to underlying disease, previous treatments and the variable liability of available tests (i.e., the direct antiglobulin test, anti-platelet antibodies, etc.). Among extra-hematological IRAEs, cutaneous and endocrine ones are the most frequent (up to 30–50%), ranging from mild (pruritus, eczema and thyroid dysfunctions) to severe forms (bullous disorders, hypophysitis and diabetes), mostly requiring topic or replacement therapy. Gastroenteric and kidney toxicities occur in about 5% of patients, biopsies may support the diagnosis, and immunosuppressive treatment is required in severe cases. Finally, neurologic and cardiologic IRAEs, although rare, may be life-threatening and require prompt intervention. By reviewing the most recent literature on post-CPI IRAEs, it emerged that clinical suspicion and monitoring of laboratory markers of organ damage is pivotal to a prompt diagnosis. In severe cases, CPI should be discontinued and immunosuppressive therapy started, whilst rechallenge is anecdotal and should be carefully evaluated.

Preliminary evaluation of a flow cytometric assay with microsphere controls for the detection of platelet-bound antibodies in canine immune thrombocytopenia.

Canine immune thrombocytopenia (ITP) ranges from a mild to severe bleeding disorder, and platelet counts do not reliably predict clinical disease course. The detection of platelet autoantibodies may further define the disease phenotype, but variability in assay configurations and a lack of well-characterized controls limit the diagnostic utility of anti-platelet antibody assays. We aimed to develop control reagents to facilitate the characterization of canine platelet surface-associated immunoglobulin (PSAIg) in flow cytometric assays. Silica microspheres were coated with canine IgG and IgM to assess the reactivity of goat and rabbit origin anti-canine immunoglobulin reagents. They were also used as positive controls in the PSAIg assay. Preliminary assay evaluation and determination of sample stability used PRP isolated from seven healthy dogs and 26 dogs newly diagnosed with thrombocytopenia. Blood sample stability was established for up to a 48-hour storage time. The conjugated positive control microspheres demonstrated stable fluorescent labeling over a 2-year observation period. Rabbit and goat origin anti-dog IgM fluorescent antibody labels reacted nonspecifically with canine IgG. Rabbit origin anti-dog IgG antibody demonstrated greater class specificity for canine IgG than a goat origin antibody. Thrombocytopenic dogs had a broad range of membrane-bound immunoglobulin. Median PSAIgG for dogs with primary or secondary ITP (18.4%, 34.1%, respectively) were significantly higher than controls (3.8%, P<.05). The described assay reagents and procedures provide positive controls and allow consistent thresholding to define a positive test result, suitable for any flow cytometer. A rabbit anti-dog IgG fluorescent label demonstrated specificity for canine IgG and was useful for the detection of PSAIgG in thrombocytopenic dogs.

Cerebral Venous Thrombosis in Patients With Heparin-Induced Thrombocytopenia a Systematic Review.

Cerebral venous thrombosis (CVT) has recently been reported as a common thrombotic manifestation in association with vaccine-induced thrombotic thrombocytopenia, a syndrome that mimics heparin-induced thrombocytopenia (HIT) and occurs after vaccination with adenovirus-based SARS-CoV-2 vaccines. We aimed to systematically review the incidence, clinical features, and prognosis of CVT occurring in patients with HIT. The study protocol was registered with PROSPERO (CRD42021249652). MEDLINE, EMBASE and Cochrane CENTRAL were searched up to June 1, 2021 for HIT case series including >20 patients, or any report of HIT-related CVT. Demographic, neuroradiological, clinical, and mortality data were retrieved. Meta-analysis of proportions with random-effect modeling was used to derive rate of CVT in HIT and in-hospital mortality. Pooled estimates were compared with those for CVT without HIT and HIT without CVT, to determine differences in mortality. From 19073 results, we selected 23 case series of HIT (n=1220) and 27 cases of HIT-related CVT (n=27, 71% female). CVT developed in 1.6% of 1220 patients with HIT (95% CI,1.0%-2.5%, I2=0%). Hemorrhagic brain lesions occurred in 81.8% of cases of HIT-related CVT and other concomitant thrombosis affecting other vascular territory was reported in 47.8% of cases. In-hospital mortality was 33.3%. HIT-related CVT carried a 29% absolute increase in mortality rate compared with historical CVT controls (33.3% versus 4.3%, P<0.001) and a 17.4% excess mortality compared with HIT without CVT (33.3% versus 15.9%, P=0.046). CVT is a rare thrombotic manifestation in patients with HIT. HIT-related CVT has higher rates of intracerebral hemorrhage and a higher mortality risk, when compared with CVT in historical controls. The recently reported high frequency of CVT in patients with vaccine-induced thrombotic thrombocytopenia was not observed in HIT, suggesting that additional pathophysiological mechanisms besides anti-platelet factor-4 antibodies might be involved in vaccine-induced thrombotic thrombocytopenia-related CVT.