Longevity of antibody responses is associated with distinct antigen-specific B cell subsets early after infection.

Introduction: Upon infection, T cell-driven B cell responses in GC reactions induce memory B cells and antibody-secreting cells that secrete protective antibodies. How formation of specifically long-lived plasma cells is regulated via the interplay between specific B and CD4+ T cells is not well understood. Generally, antibody levels decline over time after clearance of the primary infection.

Sensitive liquid biopsy monitoring correlates with outcome in the prospective international GPOH-DCOG high-risk neuroblastoma RT-qPCR validation study.

Background: Liquid biopsies offer less burdensome sensitive disease monitoring. Bone marrow (BM) metastases, common in various cancers including neuroblastoma, is associated with poor outcomes. In pediatric high-risk neuroblastoma most patients initially respond to treatment, but in the majority the disease recurs with only 40% long-term survivors, stressing the need for more sensitive detection of disseminated disease during therapy.

Real-world performance of a clinical droplet digital polymerase chain reaction assay for non-invasive foetal blood group and platelet antigen genotyping of alloimmunized pregnant women with antibodies directed against RhD, RhE, Rhc, RhC, K1, HPA-1a or HPA-5b: A 1-year experience.

Background And Objectives: To test the performance of a new droplet digital polymerase chain reaction (ddPCR) non-invasive foetal blood group and platelet antigen genotyping assay in the setting of a Dutch reference laboratory for foetal blood group and platelet antigen genotyping. Our population comprised 229 consecutive alloimmunized pregnant women who presented between April 2022 and March 2023 with 250 requests for non-invasive foetal RHD, RHE, RHc, RHC, K1, HPA-1a or HPA-5b blood group and platelet antigen genotyping.

Materials And Methods: Samples were genotyped for blood group and platelet antigen alleles along with methylated RASSF1a (mRASSF1a) and sex-determining region of Y (SRY) and DYS14 as positive foetal controls.

Screening of pregnant women for foetal neonatal alloimmune thrombocytopenia: A cost-utility analysis.

Background And Objectives: Foetal and neonatal alloimmune thrombocytopenia (FNAIT) results from maternal platelet-directed antibodies and can result in severe intracranial haemorrhage (ICH) in foetuses and newborns. Screening for human platelet antigen-1a (HPA-1a)-directed antibodies during pregnancy could allow timely intervention with antenatal treatment and prevent ICH. We assessed the cost effectiveness of HPA-1a typing and anti-HPA-1a-screening as part of the prenatal screening programme.

Are measurable residual disease results after consolidation therapy useful in children with acute lymphoblastic leukemia?

Measurable residual disease (MRD) is regularly tested at later timepoints after the end of first consolidation (EOC) in children with acute lymphoblastic leukemia (ALL). The question remains whether this is useful for detecting (molecular) relapse. We investigated the clinical relevance of MRD after EOC in intermediate risk patients treated on DCOG-ALL-10 (n = 271) and DCOG-ALL-9 (n = 122), with MRD <0.

Antibodies against Platelet Glycoproteins in Clinically Suspected VITT Patients.

Vaccine-induced thrombotic thrombocytopenia (VITT) is a rare but severe complication following COVID-19 vaccination, marked by thrombocytopenia and thrombosis. Analogous to heparin-induced thrombocytopenia (HIT), VITT shares similarities in anti-platelet factor 4 (PF4) IgG-mediated platelet activation via the FcγRIIa. To investigate the involvement of platelet-antibodies in VITT, we analyzed the presence of platelet-antibodies directed against glycoproteins (GP)IIb/IIIa, GPV and GPIb/IX in the serum of 232 clinically suspected VITT patients determined based on (suspicion of) occurrence of thrombocytopenia and/or thrombosis in relation to COVID-19 vaccination.

Disease severity in subsequent pregnancies with RhD immunization: A nationwide cohort.

Background And Objectives: To evaluate the severity of haemolytic disease of the foetus and newborn (HDFN) in subsequent pregnancies with RhD immunization and to identify predictive factors for severe disease.

Materials And Methods: Nationwide prospective cohort study, including all pregnant women with RhD antibodies. All women with at least two pregnancies with RhD antibodies and RhD-positive foetuses were selected.

Laboratory approach for vaccine-induced thrombotic thrombocytopenia diagnosis in the Netherlands.

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.

Generation of human antibodies targeting human platelet antigen (HPA)-1a.

Background: Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a condition during pregnancy, which can lead to thrombocytopenia and a bleeding tendency with intracranial hemorrhage (ICH) being the most concerning complication in the fetus or neonate. An incompatibility between human platelet antigen (HPA)-1a accounts for the majority of FNAIT cases. Binding of HPA-1a-specific alloantibodies to their target on fetal platelets and endothelial cells can induce apoptosis of megakaryocytes, disrupt platelet function, and impair angiogenesis.

Noninvasive fetal blood group antigen genotyping.

Noninvasive fetal blood group antigen genotyping serves as a diagnostic tool to predict the risk of hemolytic disease of the fetus and newborn in pregnancies of immunized women. In addition, fetal RHD genotyping is used as an antenatal screening to guide targeted use of immunoglobulin prophylaxis in non-immunized RhD negative, pregnant women. Based on testing of cell-free DNA extracted from maternal plasma, these noninvasive assays demonstrate high performance accuracies.

Extensive red blood cell matching considering patient alloimmunization risk.

Background And Objectives: Red blood cell (RBC) transfusions pose a risk of alloantibody development in patients. For patients with increased alloimmunization risk, extended preventive matching is advised, encompassing not only the ABO-D blood groups but also the most clinically relevant minor antigens: C, c, E, e, K, Fy, Fy, Jk, Jk, S and s. This study incorporates patient-specific data and the clinical consequences of mismatching into the allocation process.

Assessment of IgG-Fc glycosylation from individual RhD-specific B cell clones reveals regulation at clonal rather than clonotypic level.

The type and strength of effector functions mediated by immunoglobulin G (IgG) antibodies rely on the subclass and the composition of the N297 glycan. Glycosylation analysis of both bulk and antigen-specific human IgG has revealed a marked diversity of the glycosylation signatures, including highly dynamic patterns as well as long-term stability of profiles, yet information on how individual B cell clones would contribute to this diversity has hitherto been lacking. Here, we assessed whether clonally related B cells share N297 glycosylation patterns of their secreted IgG.

Cellular surface plasmon resonance-based detection of anti-HPA-1a antibody glycosylation in fetal and neonatal alloimmune thrombocytopenia.

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) can occur due to maternal IgG antibodies targeting platelet antigens, causing life-threatening bleeding in the neonate. However, the disease manifests itself in only a fraction of pregnancies, most commonly with anti-HPA-1a antibodies. We found that in particular, the core fucosylation in the IgG-Fc tail is highly variable in anti-HPA-1a IgG, which strongly influences the binding to leukocyte IgG-Fc receptors IIIa/b (FcγRIIIa/b).

Complement activation drives antibody-mediated transfusion-related acute lung injury via macrophage trafficking and formation of NETs.

Transfusion-related acute lung injury (TRALI) is one of the leading causes of transfusion-related fatalities and, to date, is without available therapies. Here, we investigated the role of the complement system in TRALI. Murine anti-major histocompatibility complex class I antibodies were used in TRALI mouse models, in combination with analyses of plasma samples from patients with TRALI.

Comparative analysis of spike-specific IgG Fc glycoprofiles elicited by adenoviral, mRNA, and protein-based SARS-CoV-2 vaccines.

IgG antibodies are important mediators of vaccine-induced immunity through complement- and Fc receptor-dependent effector functions. Both are influenced by the composition of the conserved -linked glycan located in the IgG Fc domain. Here, we compared the anti-Spike (S) IgG1 Fc glycosylation profiles in response to mRNA, adenoviral, and protein-based COVID-19 vaccines by mass spectrometry (MS).

Case series on clinical applications of liquid biopsy in pediatric solid tumors: towards improved diagnostics and disease monitoring.

Background And Aims: Solid tumors account for about 30% of all pediatric cancers. The diagnosis is typically based on histological and molecular analysis of a primary tumor biopsy. Liquid biopsies carry several advantages over conventional tissue biopsy.

Quality assessment and harmonization of laboratories across Europe for multiple SARS-CoV-2 serology assays.

Background And Objectives: There is a need for conversion of SARS-CoV-2 serology data from different laboratories to a harmonized international unit. We aimed to compare the performance of multiple SARS-CoV-2 antibody serology assays among 25 laboratories across 12 European countries.

Materials And Methods: To investigate this we have distributed to all participating laboratories a panel of 15 SARS-CoV-2 plasma samples and a single batch of pooled plasma calibrated to the WHO IS 20/136 standard.

Targeted locus amplification to develop robust patient-specific assays for liquid biopsies in pediatric solid tumors.

Background: Liquid biopsies combine minimally invasive sample collection with sensitive detection of residual disease. Pediatric malignancies harbor tumor-driving copy number alterations or fusion genes, rather than recurrent point mutations. These regions contain tumor-specific DNA breakpoint sequences.

Early, very high-titre convalescent plasma therapy in clinically vulnerable individuals with mild COVID-19 (COVIC-19): protocol for a randomised, open-label trial.

Introduction: COVID-19 convalescent plasma (CCP) is a possible treatment option for COVID-19. A comprehensive number of clinical trials on CCP efficacy have already been conducted. However, many aspects of CCP treatment still require investigations: in particular (1) Optimisation of the CCP product, (2) Identification of the patient population in need and most likely to benefit from this treatment approach, (3) Timing of administration and (4) CCP efficacy across viral variants in vivo.

Cell-Free RNA from Plasma in Patients with Neuroblastoma: Exploring the Technical and Clinical Potential.

Neuroblastoma affects mostly young children, bearing a high morbidity and mortality. Liquid biopsies, e.g.