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In patients with severe and recurrent infections, minimal diagnostic workup to test for Inborn Errors of Immunity (IEI) includes a full blood count, IgG, IgA and IgM. Vaccine antibodies against tetanus toxoid are also frequently measured, whereas testing for anti-polysaccharide IgG antibodies and IgG subclasses is not routinely performed by primary care physicians. This basic approach may cause a significant delay in diagnosing monogenic IEI that can present with an impaired IgG response to polysaccharide antigens with or without IgG subclass deficiency at an early stage. Our article reviews genetically defined IEI, that may initially present with an impaired IgG response to polysaccharide antigens, but normal or only slightly decreased IgG levels and normal responses to protein or conjugate vaccine antigens. We summarize clinical, genetic, and immunological findings characteristic for these IEI. This review may help clinicians to identify patients that require extended immunologic and genetic evaluations despite unremarkable basic immunologic findings. We recommend the inclusion of anti-polysaccharide IgG antibodies as part of the initial routine work-up for possible IEI., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (© 2024 Fasshauer, Dinges, Staudacher, Völler, Stittrich, von Bernuth, Wahn and Krüger.)

Heterozygous germline variants in human IKZF1 encoding for IKAROS define an inborn error of immunity with immunodeficiency, immune dysregulation and risk of malignancy with a broad phenotypic spectrum. Growing evidence of underlying pathophysiological genotype-phenotype correlations helps to improve our understanding of IKAROS-associated diseases. We describe 6 patients from 4 kindreds with two novel IKZF1 variants leading to haploinsufficiency from 3 centers in Germany. We also provide an overview of first symptoms to a final diagnosis including data from the literature., Competing Interests: Author AS and HB were employed by the company Labor Berlin Charité-Vivantes GmbH and author MF was employed by the company Hospital St. Georg GGmbH Leipzig. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (© 2024 Strauss, Körholz, Kuehn, Gil Silva, Taube, Trautmann-Grill, Stittrich, Pietzsch, Wiedemuth, Wahn, von Bernuth, Rosenzweig, Fasshauer, Krüger and Schuetz.)

Background: Pulmonary manifestations are the major cause of morbidity and mortality in patients with inborn errors of immunity (IEI). New and more sensitive diagnostic methods can potentially lead to earlier recognition and treatment of IEI lung disease and improve outcome. The aim of this study was to compare multiple-breath washout (MBW) and spirometry in patients with IEI and cystic fibrosis (CF) as well as healthy controls (HC) and to evaluate the sensitivity of lung clearance index (LCI) to assess lung disease in IEI., Methods: IEI patients (n=114) were recruited from our paediatric and adult immunodeficiency outpatient clinics and compared to age-matched CF patients (n=114) and HC (n=114). MBW measurements and spirometry were performed in the study participants, and MBW testing was repeated after 63-707 days in IEI patients (n=70)., Results: The LCI was significantly higher in IEI patients than in HC ( p <0.001) and significantly lower than in CF patients (p<0.001). The forced expiratory volume in 1 s (FEV 1 ) z-score was significantly lower in IEI patients than in HC (p<0.01) and significantly higher than in CF patients (p<0.01). LCI and FEV 1 z-score correlated moderately negatively in the total cohort, the IEI group and the CF group. Nineteen (20.7%) of 92 IEI patients and 35 (33.3%) of 105 CF patients had an elevated LCI but a normal FEV 1 z-score. After a median of 364 days, the median LCI of 70 IEI patients increased significantly by 0.2., Conclusion: MBW is useful to detect lung disease in IEI and is more sensitive than spirometry., Competing Interests: Conflict of interest: S. Thee declares grants to their institution from the German Innovation Fond; payment or honoraria from Chiesi (European Cystic Fibrosis Society meeting 2022) and Vertex (LEAD meeting, adherence forum); and travel expenses from Chiesi to attend the European Cystic Fibrosis Society meeting 2022. Conflict of interest: O. Staudacher declares a Travel Grant for Young Immunologists from Arbeitsgemeinschaft Pädiatrische Immunologie in the 36 months prior to manuscript submission. Conflict of interest: E. Steinke declares grants or contracts from the Clinician Scientist Program of the Berlin Institute of Health (funded by the German Federal Ministry of Education and Research); payment or honoraria for review of educational manuscripts from Vertex Pharmaceuticals Inc.; and a travel grant for conference attendance from the European Cystic Fibrosis Society, all in the 36 months prior to manuscript submission. Conflict of interest: J. Röhmel declares payment or honoraria, and support for attending meetings and/or travel from Vertex Pharmaceuticals in the 36 months prior to manuscript submission (with permission from their institution); and an unpaid role as a work package leader in BEAT-PCD, a European Research Society Clinical Research Collaboration. Conflict of interest: V. Wahn declares payment or honoraria from CSL Behring (related to www.immundefekt.de) and Pharming (related to a manuscript on APDS); and an honorarium and travel expenses from Pharming for attendance at the DGKJ congress, all in the 36 months prior to manuscript submission. Conflict of interest: H. von Bernuth declares consulting fees from Infill Healthcare Communication (2022); payment or honoraria from Deutsche Selbsthilfe Angeborene Immundefekte) (2023) and CSL Behring (2021); and payment for expert testimony from Bundessozialgericht (2023); as well as that they are a member of the Standing Comission on Vaccination at the Robert Koch Insitut, Ständige Impfkommission (STIKO). Conflict of interest: M.A. Mall declares funding to their institution in connection to the present work from the German Ministry for Education and Research (BMBF; Grant #82DZL009B1); and an unpaid role as a Fellow of the European Respiratory Society. Conflict of interest: M. Stahl declares funding to their institution (Heisenberg professorship) from the German Research Foundation (Deutsche Forschungsgemeinschaft) in connection to the present work; as well as unpaid roles as Chairman of the Forschungsgemeinschaft Mukoviszidose; Secretary of the Cystic Fibrosis Group of the European Respiratory Society; and Treasurer of the German Society of Paediatric Pulmonology. Conflict of interest: All other authors declare no competing interests., (Copyright ©The authors 2024.)

Activated PI3Kδ syndrome (APDS) is a rare inborn error of immunity (IEI) characterized primarily by frequent infections, lymphoproliferation and autoimmunity. Since its initial description in 2013, APDS has become part of the growing group of nearly 500 IEIs affecting various components of the immune system. The two subtypes of APDS - APDS1 and APDS2 - are caused by variants in the PIK3CD and PIK3R1 genes, respectively. Due to the rarity of the disease and the heterogeneous clinical picture, many patients are not diagnosed until years after symptom onset. Another challenge is the large number of PIK3CD and PIK3R1 variants whose functional significance for developing APDS is inconclusive. Treatment of APDS has so far been mostly symptom-oriented with immunoglobulin replacement therapy, immunosuppressive therapies and antibiotic or antiviral prophylaxes. Additionally, allogeneic stem cell transplantation as well as new targeted therapies are options targeting the root cause that may improve patients' quality of life and life expectancy. However, the clinical course of the disease is difficult to predict which complicates the choice of appropriate therapies. This review article discusses diagnostic procedures and current and future treatment options, and highlights the difficulties that physicians, patients and their caretakers face in managing this complex disease. This article is based on cohort studies, the German and US guidelines on the management of primary immunodeficiencies as well as on published experience with diagnosis and compiled treatment experience for APDS., Competing Interests: Author SV was employed by Infill Healthcare Communication. Author VW received a honorarium from Pharming Group N.V. for the supervision of the writing of this article. His homepage www.immundefekt.de is supported by CSL Behring. Author CS has declined a honorarium for her contribution to this manuscript. She was PI for Phase 3 Study CCDZ173X2201 Novartis and PI for the open extension study CCDZ173X2201E1 Novartis/Pharming. The authors declare that this study received funding from Pharming Group N.V.. The funder had the following involvement in the study: writing of the article., (Copyright © 2023 Vanselow, Wahn and Schuetz.)

In common variable immunodeficiency (CVID), heterozygous damaging NFKB1 variants represent the most frequent monogenic cause. NFKB1 encodes the precursor p105, which undergoes proteasomal processing to generate the mature NF-κB transcription factor subunit p50. The majority of NFKB1 sequence changes comprises missense variants of uncertain significance (VUS), each requiring functional evaluation to assess causality, particularly in families with multiple affected members presenting with different phenotypes. In four affected members of a German family, all diagnosed with CVID, we identified a previously uncharacterized heterozygous NFKB1 missense variant (c.1049A>G; p.Tyr350Cys). The clinical phenotypes varied markedly regarding onset, frequency and severity of infections. Consistent immunologic findings were hypogammaglobulinemia with normal specific antibody response to protein- and polysaccharide-based vaccinations, reduced switched memory B cells and decreased lymphocyte proliferation upon stimulation with the B cell mitogen SAC. To assess the pathogenicity of the NFKB1 missense variant, we employed immunophenotyping and functional analyses in a routine in vitro cell culture model. Following site-directed mutagenesis to introduce the variant into overexpression vectors encoding EGFP-fused p105 or p50, we analyzed transiently transfected HEK293T cells by confocal imaging and Western blotting. The cytoplasmic p105-Tyr350Cys precursor gained only weak expression levels indicating accelerated decay. The missense change disabled processing of the precursor to prevent the generation of mutant p50. Unlike the wildtype p50, the overexpressed mutant p50-Tyr350Cys was also not sustainable and showed a conspicuous subnuclear mislocalization with accumulation in dense aggregates instead of a homogenous distribution. Electrophoretic mobility shift assays, fluorescence-based reporter gene analyses and co-transfection experiments however demonstrated, that the DNA-binding activity of p50-Tyr350Cys and the interaction with RelA(p65), IκBα and wildtype p50 were preserved. Mutation carriers had reduced p105 and p50 levels, indicating insufficient protein amounts as the most likely primary defect. In conclusion, the missense variant c.1049A>G caused a detrimental defect, preventing the persistent expression of both, the p105-Tyr350Cys precursor and the mature p50-Tyr350Cys. The variable clinical phenotypes among affected family members sharing an identical pathogenic NFKB1 variant support a disease mechanism provoked by a p105/p50 (haplo)insufficient condition., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Fliegauf, Krüger, Steiner, Hanitsch, Büchel, Wahn, von Bernuth and Grimbacher.)

The autosomal recessive immunodeficiency-centromeric instability-facial anomalies syndrome (ICF) is characterized by immunodeficiency, developmental delay, and facial anomalies. ICF2, caused by biallelic ZBTB24 gene mutations, is acknowledged primarily as an isolated B-cell defect. Here, we extend the phenotype spectrum by describing, in particular, for the first time the development of a combined immune defect throughout the disease course as well as putative autoimmune phenomena such as granulomatous hepatitis and nephritis. We also demonstrate impaired cell-proliferation and increased cell death of immune and non-immune cells as well as data suggesting a chromosome separation defect in addition to the known chromosome condensation defect.

The granule enzyme myeloperoxidase (MPO) plays an important role in neutrophil antimicrobial responses. However, the severity of immunodeficiency in patients carrying mutations in MPO is variable. Serious microbial infections, especially with Candida species, have been observed in a subset of completely MPO-deficient patients. Here we show that neutrophils from donors who are completely deficient in MPO fail to form neutrophil extracellular traps (NETs), indicating that MPO is required for NET formation. In contrast, neutrophils from partially MPO-deficient donors make NETs, and pharmacological inhibition of MPO only delays and reduces NET formation. Extracellular products of MPO do not rescue NET formation, suggesting that MPO acts cell-autonomously. Finally, NET-dependent inhibition of Candida albicans growth is compromised in MPO-deficient neutrophils. The inability to form NETs may contribute in part to the host defense defects observed in completely MPO-deficient individuals.

Patients infected with human immunodeficiency virus type 1 (HIV-1) are considered to be at increased risk for 2009 H1N1 influenza-related complications. We performed an observational study after an outbreak of 2009 H1N1 influenza virus infection among a group of 15 HIV-1-infected school-aged children in Germany in October 2009. Clinical course, kinetics of viral shedding, and antibody response among children with CD4 cell counts >350 cells/μL and 2009 H1N1 influenza virus coinfection did not appear to differ from that among healthy children. Oseltamivir shortened the duration of viral shedding.

For intensively pretreated pediatric patients with human immunodeficiency virus type 1 (HIV-1) infection, the treatment options available are limited. We report the case of a highly treatment-experienced 12-year-old boy with multidrug-resistant HIV-1, who was successfully treated with highly active antiretroviral therapy (HAART) including ritonavir-boosted tipranavir oral solution, a novel non-peptic protease inhibitor, and enfuvirtide.

Objective: A prospective observational study to investigate hematologic alterations during the first 3 months of life in HIV-exposed uninfected infants subjected to antiretroviral medication before and after birth., Methods: Two hundred twenty-one consecutive uninfected infants born to HIV-positive mothers on antiretroviral medication during pregnancy were included. Perinatal transmission prophylaxis comprised zidovudine (ZDV) administered intravenously intrapartum and 10 days after birth. Blood counts and differentials were determined at birth and at 2, 4, 6, and 12 weeks of age, and hematologic toxicity was graded according to pediatric toxicity scales. Data were analyzed according to the kind of prenatal medication (ZDV alone or with another nucleoside reverse transcriptase inhibitor [NRTI] vs. highly active antiretroviral therapy [HAART])., Results: Median hemoglobin was significantly lower in HAART-exposed newborns from birth (P = 0.004) until day 28. During follow-up, 119 (53.8%) infants had anemia grade 2 or higher on at least 1 occasion; 16 (7.2%) received red blood cell transfusion at 23 (range: 1-56) days of age. Neutropenia grade 2 or higher occurred in 106 (48.0%) infants at least once; 8 infants had staphylococcal infections, and 2 infections were severe. After adjustment for possible confounders (prematurity, birth weight, ethnicity, gender, duration of maternal antiretroviral therapy, maternal Centers for Disease Control and Prevention stage, and maternal illicit drug use), HAART exposure was the only independent risk factor for anemia (odds ratio [OR] = 2.22, 95% confidence interval [CI]: 1.06 to 4.64; P = 0.034) and neutropenia (OR = 2.15, CI: 1.02 to 4.55; P = 0.045)., Conclusions: Antiretroviral transmission prophylaxis is associated with significant anemia and neutropenia in HIV-uninfected infants during the first 3 months of life. Anemia was more profound in HAART-exposed infants.

Neutrophil extracellular traps (NETs) are extracellular structures composed of chromatin and granule proteins that bind and kill microorganisms. We show that upon stimulation, the nuclei of neutrophils lose their shape, and the eu- and heterochromatin homogenize. Later, the nuclear envelope and the granule membranes disintegrate, allowing the mixing of NET components. Finally, the NETs are released as the cell membrane breaks. This cell death process is distinct from apoptosis and necrosis and depends on the generation of reactive oxygen species (ROS) by NADPH oxidase. Patients with chronic granulomatous disease carry mutations in NADPH oxidase and cannot activate this cell-death pathway or make NETs. This novel ROS-dependent death allows neutrophils to fulfill their antimicrobial function, even beyond their lifespan.

Amorphic mutations in the NF- kappa B essential modulator (NEMO) cause X-dominant incontinentia pigmenti, which is lethal in males in utero, whereas hypomorphic mutations cause X-recessive anhidrotic ectodermal dysplasia with immunodeficiency, a complex developmental disorder and life-threatening primary immunodeficiency. We characterized the NEMO mutation 110&#95;111insC, which creates the most-upstream premature translation termination codon (at codon position 49) of any known NEMO mutation. Surprisingly, this mutation is associated with a pure immunodeficiency. We solve this paradox by showing that a Kozakian methionine codon located immediately downstream from the insertion allows the reinitiation of translation. The residual production of an NH(2)-truncated NEMO protein was sufficient for normal fetal development and for the subsequent normal development of skin appendages but was insufficient for the development of protective immune responses.