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Immunocompromised individuals are at significantly elevated risk for severe courses of coronavirus disease 2019 (COVID-19). In addition to vaccination, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing antibodies (nAbs) have been applied throughout the pandemic, with time of treatment onset and potency against the currently prevailing virus variant identified as relevant factors for medical benefit. Using data from the European Society for Immunodeficiencies (ESID) registry, the present study evaluated COVID-19 cases in three groups of patients with inborn errors of immunity (IEI; 981 agammaglobulinemia patients on immunoglobulin replacement therapy (IGRT); 8960 non-agammaglobulinemia patients on IGRT; 14 428 patients without IGRT), and the neutralizing capacity of 1100 immunoglobulin lots against SARS-CoV-2 ("Wuhan" and Omicron strains), throughout 3 years. From the first (2020/2021) to the second (2021/2022) cold season, i.e., during the virus drift to the more contagious Omicron variants, an increase in case numbers was recorded that was comparable (~2- to 3-fold) for all three study groups. During the same period, immunoglobulin lots showed a profound nAb increase against the archetypal SARS-CoV-2 strain, yet only low levels of Omicron nAbs. Notably, shortly before the third (2022/2023) cold season, Omicron-neutralizing capacity of released immunoglobulin lots had plateaued at high levels. From the second to the third cold season, COVID-19 cases dropped markedly. While a ~6-fold case reduction was recorded for the groups of non-agammaglobulinemia patients on IGRT and IEI patients not receiving IGRT, the decline was ~30-fold for the group of agammaglobulinemia patients on IGRT. These findings suggest a substantial COVID-19-protective effect of IGRT, at least for distinct groups of antibody-deficient patients., (© 2024 Takeda Manufacturing Austria AG and The Authors. Journal of Medical Virology published by Wiley Periodicals LLC.)

Introduction: Several well-established clinical laboratory methods are available to measure von Willebrand factor (VWF) in plasma samples, but few data are available on their use for analysing recombinant VWF (rVWF)., Aim: To evaluate how clinical diagnostic laboratories analyse rVWF and plasma-derived VWF (pdVWF) spiked in vitro into VWF-deficient plasma using quantitative protein and functional assays of VWF., Methods: Human VWF-deficient plasma samples were spiked with rVWF (vonicog alfa; Takeda) or pdVWF/factor VIII (pdVWF/FVIII; antihemophilic factor/VWF complex [human], CSL Behring), each at final concentrations of 1.0, 0.6, 0.2, 0.1 IU/mL VWF:ristocetin cofactor activity (VWF:RCo) according to labelled VWF activity. The ISTH SSC secondary coagulation standard was used as a control. Participating laboratories received three sets of these blinded aliquots. Mean results per assay were compared with the expected potency based on the labelled VWF:RCo activity., Results: Among 39 laboratories, the most commonly established assay was VWF:RCo; 22 laboratories reported data from 2214 tests. Despite a trend to lower values, VWF:RCo activities for rVWF were in agreement with target concentrations (71%-109%), whereas VWF:platelet glycoprotein Ib (VWF:GpIb) and VWF collagen-binding activity (VWF:CB) assays gave high recoveries (up to 132% and 127%, respectively). In contrast, pdVWF/FVIII was substantially underestimated by VWF:GpIb and VWF:CB assays (56%-86% recoveries), whereas the VWF:RCo assay gave recoveries of 47%-112% for pdVWF/FVIII., Conclusion: The results of VWF assays used in clinical laboratories differ between rVWF and pdVWF, particularly for VWF:GpIb and VWF:CB assays. These differences may arise from the higher multimeric structure of rVWF compared to pdVWF., (© 2023 Takeda Development Center Americas, Inc. Haemophilia published by John Wiley & Sons Ltd.)

Immunoglobulin lots (N = 176) released since March 2020 were tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing antibodies, with first positive results for September 2020 lots (mean, 1.7 IU/mL; 46% of lots positive). From there, values steadily increased, in correlation with the cumulative coronavirus disease 2019 (COVID-19) incidence, to reach a mean of 31.2 IU/mL and 93% of lots positive by January 2021. Extrapolating the correlation, immunoglobulins could reach an anti-SARS-CoV-2 potency of approximately 345 IU/mL by July 2021. At that stage, prophylactic immunoglobulin treatment for primary/secondary immunodeficiency could contain similar doses of anti-SARS-CoV-2 as convalescent plasma that is used for treatment of COVID-19., Competing Interests: Potential conflicts of interest. The authors are employees of Baxter AG, Vienna, Austria, now part of the Takeda group of companies. M. R. F., M. K., R. I., and T. R. K. have Takeda stock interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed., (© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America.)

Background: Coronavirus disease 2019 (COVID-19) convalescent individuals carry antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that, through a plasma donation, can be used as a potential therapeutic either in direct transfusion or for the manufacture of hyperimmune globulin (HIG). The success of such interventions depends on the antibody potency in such plasma donations, but little information on the collection of potent units is currently available., Study Design and Methods: A total of 8749 plasma units, collected from April until September 2020 from first-time U.S. COVID-19 convalescent plasma donors, were characterized for SARS-CoV-2 immunoglobulin G (IgG) antibodies by Abbott chemiluminescent microparticle immunoassay (CMIA). The period between COVID-19 onset until donation and donor age, ethnicity, sex, and COVID-19 severity were evaluated against the obtained signal (index S/C)., Results: A marked decrease in mean index S/C was seen over the plasma collection period surveyed, which was significantly correlated to decreases in mean plasma donor age (p < .0001; R 2 = .726) and percentage of donations obtained from COVID-19 convalescent patients who had been hospitalized (p = .001; R 2 = .4426). The highest titer plasma units were obtained soon after convalescence from COVID-19 patients who required hospitalization, from advanced age donors, and from Black/African/Hispanic American versus White/Caucasian ethnicities, whereas there was no effect of donor sex on the values obtained with the Abbott CMIA., Conclusion: Since the onset of the pandemic, the average SARS-CoV-2 IgG values of first-time U.S. COVID-19 convalescent plasma donations have significantly dropped, mainly due to donations from progressively younger aged donors who tend to experience less severe COVID-19., (© 2021 The Authors. Transfusion published by Wiley Periodicals LLC. on behalf of AABB.)

Gene therapy product release requires reliable and consistent demonstration of biopotency. In hemophilia B vectors, this is usually determined in vivo by measuring the plasma levels of the expressed human factor IX (FIX) transgene product in FIX knockout mice. To circumvent this laborious assay, we developed an in vitro method in which the HepG2 human liver cell line was infected with the vector, and the resulting FIX activity was determined in the conditioned medium using a chromogenic assay. The initial low sensitivity of the assay, particularly toward adeno-associated viral serotype 8 (AAV8), increased approximately 100-fold and allowed linear measurement in a broad range of multiplicities of infection. Statistical parameters indicated high assay repeatability (relative standard deviation (RSD) < 5%) and intra-assay reproducibility (RSD < 20%). To compare the performance of the in vitro and in vivo biopotency assay, we applied statistical analyses including regression techniques and variation decomposition to the results obtained for 25 AAV8-FIX vector lots (BAX 335). These showed a highly significant correlation, with the cell culture-based assay demonstrating less variation than the in vivo test. The in vitro assay thus constitutes a viable alternative to using animals for lot release testing., (© 2020 Shire International GmbH, now part of Takeda, Zurich, Switzerland.)

Vaccination against measles has reduced disease, although measles virus antibody (MVAb) levels are lower after vaccination than natural infection. Immunoglobulin (IG) preparations thus contain decreasing MVAb titers. US IG lot release requires a minimum titer of MVAb, yet equivalent information is not available for other geographies. Using a measles virus neutralization assay, IG fractionated from US or EU plasma is shown to contain similar levels of MVAb always above US regulatory requirements, supportive of equivalent protection against MV infection. Thus, the dosage for post-exposure prophylaxis in the EU could be aligned with the US FDA's treatment recommendations., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Unlabelled: Studies evaluating the immunogenicity of two pediatric tick-borne encephalitis virus (TBEV) vaccines have reported contradictory results. These vaccines are based on two different strains of the European TBEV subtype: FSME-Immun Junior is based on the Neudörfl (Nd) strain, whereas Encepur Children is based on the Karlsruhe (K23) strain. The antibody (Ab) response induced by these two vaccines might be influenced by antigenic differences in the envelope (E) protein, which is the major target of neutralizing antibodies. We used an established hybrid virus assay platform to compare the levels of induction of neutralizing antibodies against the two vaccine virus strains in children aged 1 to 11 years who received two immunizations with FSME-Immun Junior or Encepur Children. The influence of amino acid differences between the E proteins of the Nd and K23 vaccine strains was investigated by mutational analyses and three-dimensional computer modeling. FSME-Immun Junior induced 100% seropositivity and similar neutralizing antibody titers against hybrid viruses containing the TBEV E protein of the two vaccine strains. Encepur Children induced 100% seropositivity only against the hybrid virus containing the E protein of the homologous K23 vaccine strain. Antibody responses induced by Encepur Children to the hybrid virus containing the E protein of the heterologous Nd strain were substantially and significantly (P < 0.001) lower than those to the K23 vaccine strain hybrid virus. Structure-based mutational analyses of the TBEV E protein indicated that this is due to a mutation in the DI-DII hinge region of the K23 vaccine strain E protein which may have occurred during production of the vaccine seed virus and which is not present in any wild-type TBE viruses., Importance: Our data suggest that there are major differences in the abilities of two European subtype pediatric TBEV vaccines to induce antibodies capable of neutralizing heterologous TBEV strains. This is a result of a mutation in the DI-DII hinge region of the E protein of the K23 vaccine virus strain used to manufacture Encepur Children which is not present in the Nd strain used to manufacture FSME-Immun Junior or in any other known naturally occurring TBEVs., (Copyright © 2016 Beck et al.)

Neuraminidase-inhibiting (NAi) antibodies have been reported to be an independent correlate of protection from influenza disease, but the NAi antibody response to influenza vaccination has never been assessed in chronically ill or immunocompromised participants. Using an enzyme-linked lectin assay, we demonstrated that 2 immunizations with a Vero cell culture-derived, whole-virus H5N1 A/Vietnam vaccine induces NAi antibodies in 94.3% of chronically ill and 83.8% of immunocompromised participants. A booster with a heterologous A/Indonesia H5N1 vaccine induced comparable NAi antibody titers in both groups and resulted in 100% seropositivity. These data support prepandemic H5N1 vaccination strategies for these highly vulnerable risk groups.

A Vero cell-derived whole-virus H5N1 influenza vaccine has been shown to induce neutralizing antibodies directed against the hemagglutinin (HA) protein of diverse H5N1 strains in animal studies and clinical trials. However, neuraminidase-inhibiting (NAi) antibodies can reduce viral spread and may be of particular importance in the event of an H5N1 pandemic, where immunity due to HA antibodies is likely absent in the general population. Here we demonstrate the effective induction of NAi antibody titers after H5N1 vaccination in humans. In contrast to the immune response directed toward HA, a single vaccine dose induced a strong NAi response that was not significantly boosted by a second dose, most probably due to priming by previous vaccination or infection with seasonal influenza viruses. After 2 immunizations, seroconversion rates based on antibody titers against HA and NA were similar, indicating the induction of equally strong immune responses against both proteins by this H5N1 vaccine.