610 Medizin und Gesundheit
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Viruses play a key role in explaining the pathogenesis of various autoimmune disorders, whose underlying principle is defined by the activation of autoreactive T-cells. In many cases, T-cells escape self-tolerance due to the failure in encountering certain MHC-I self-peptide complexes at substantial levels, whose peptides remain invisible from the immune system. Over the years, contribution of unstable defective ribosomal products (DRiPs) in immunosurveillance has gained prominence. A class of unstable products emerge from non-canonical translation and processing of unannotated mammalian and viral ORFs and their peptides are cryptic in nature. Indeed, high throughput sequencing and proteomics have revealed that a substantial portion of our genomes comprise of non-canonical ORFs, whose generation is significantly modulated during disease. Many of these ORFs comprise short ORFs (sORFs) and upstream ORFs (uORFs) that resemble DRiPs and may hence be preferentially presented. Here, we discuss how such products, normally “hidden” from the immune system, become abundant in viral infections activating autoimmune T-cells, by discussing their emerging role in infection and disease. Finally, we provide a perspective on how these mechanisms can explain several autoimmune disorders in the wake of the COVID-19 pandemic.
ESPED survey on newly diagnosed immune thrombocytopenia in childhood: how much treatment do we give?
(2021)
Background
Immune thrombocytopenia (ITP) is an autoimmune disease associated with isolated thrombocytopenia, which is caused by an imbalance between platelet production and platelet destruction. Petechial and mucous membrane hemorrhages are characteristic of ITP, but life-threatening bleeding rarely occurs. Depending on the bleeding symptoms, ITP can be treated with glucocorticoids (GC), intravenous immunoglobulins (IVIG), or in severe cases, platelet transfusions. Mild bleeding does not necessarily require therapy. Using the German Surveillance Unit for rare Pediatric Diseases (ESPED) we conducted a prospective survey on ITP patients in all German Children's Hospitals between September 2018 and August 2019. We collected data on ITP, including the clinical course, therapy implementation recommendations (according to the Association of German Scientific Medical Societies guidelines), outcome, and influence of treatment regimens depending on the treating physician´s experience with ITP patients.
Results
Of the 287 recorded cases of children with ITP, 268 questionnaires were sent to the authors. Two hundred seventeen of the questionnaires fulfilled the inclusion criteria. ITP affected boys and girls similarly, and the median age of manifestation was 3.5 years. The main reasons for hospitalization were thrombocytopenia, bleeding signs, hematomas, and/or petechiae. Bleeding scores were ≤ 3 in 96% of children, which corresponded to a low-to-moderately low risk of bleeding. No life-threatening bleeding was documented. The most common therapies were IVIG (n = 59), GC (n = 33), or a combination of these (n = 17). Blood products (i.e., red blood cells, platelet concentrate, and fresh frozen plasma) were given to 13 patients. Compared to the established guidelines, 67 patients were over-treated, and 2 patients were under-treated.
Conclusions
Adherence to German ITP treatment guidelines is currently limited. To improve patient safety and medical care, better medical training and dissemination of the guidelines are required in line with targeted analyses of patients with serious bleeding events to identify potential risk constellations.
This evidence‐based clinical guideline provides consensus‐recommendations for the treatment and care of patients with primary antibody deficiencies (PADs). The guideline group comprised 20 clinical and scientific expert associations of the German, Swiss, and Austrian healthcare system and representatives of patients. Recommendations were based on results of a systematic literature search, data extraction, and evaluation of methodology and study quality in combination with the clinical expertise of the respective representatives. Consensus‐based recommendations were determined via nominal group technique. PADs are the largest clinically relevant group of primary immunodeficiencies. Most patients with PADs present with increased susceptibility to infections, however immune dysregulation, autoimmunity, and cancer affect a significant number of patients and may precede infections. This guideline therefore covers interdisciplinary clinical and therapeutic aspects of infectious (e.g., antibiotic prophylaxis, management of bronchiectasis) and non‐infectious manifestations (e.g., management of granulomatous disease, immune cytopenia). PADs are grouped into disease entities with definitive, probable, possible, or unlikely benefit of IgG‐replacement therapy. Summary and consensus‐recommendations are provided for treatment indication, dosing, routes of administration, and adverse events of IgG‐replacement therapy. Special aspects of concomitant impaired T‐cell function are highlighted as well as clinical data on selected monogenetic inborn errors of immunity formerly classified into PADs (APDS, CTLA‐4‐, and LRBA‐deficiency).
Common variable immunodeficiency (CVID) is the most common primary immunodeficiency in adults. It is associated with hypogammaglobulinemia, recurring infections and autoimmune phenomena. Treatment includes immunoglobulin substitution and immunosuppressants. Autoimmune neurological manifestations of CVID are rare and occur predominantly as granulomatous disease. We report the case of a 35-year-old woman with CVID who developed autoimmune encephalitis as demonstrated by double cerebral biopsy. Infectious or malignant causes could be excluded. Despite intensive immunosuppressive therapy with common regimens no significant improvement could be achieved. Ultimately, an autologous hematopoietic stem cell transplantation (HSCT) was performed, resulting in lasting complete remission of the encephalitis. To our knowledge, this is the first report of refractory autoimmune phenomena in CVID treated by autologous HSCT.
The RNA-binding protein RC3H1 (also known as ROQUIN) promotes TNF\(\alpha\) mRNA decay via a 3'UTR constitutive decay element (CDE). Here we applied PAR-CLIP to human RC3H1 to identify ~3,800 mRNA targets with >16,000 binding sites. A large number of sites are distinct from the consensus CDE and revealed a structure-sequence motif with U-rich sequences embedded in hairpins. RC3H1 binds preferentially short-lived and DNA damage-induced mRNAs, indicating a role of this RNA-binding protein in the post-transcriptional regulation of the DNA damage response. Intriguingly, RC3H1 affects expression of the NF-\(\kappa\)B pathway regulators such as I\(\kappa\)B\(\alpha\) and A20. RC3H1 uses ROQ and Zn-finger domains to contact a binding site in the A20 3'UTR, demonstrating a not yet recognized mode of RC3H1 binding. Knockdown of RC3H1 resulted in increased A20 protein expression, thereby interfering with I\(\kappa\)B kinase and NF-\(\kappa\)B activities, demonstrating that RC3H1 can modulate the activity of the IKK/NF-\(\kappa\)B pathway.
B cell aggregates in the central nervous system (CNS) have been associated with rapid disease progression in patients with multiple sclerosis (MS). Here we demonstrate a key role of carcinoembryogenic antigen-related cell adhesion molecule1 (CEACAM1) in B cell aggregate formation in MS patients and a B cell-dependent mouse model of MS. CEACAM1 expression was increased on peripheral blood B cells and CEACAM1\(^+\) B cells were present in brain infiltrates of MS patients. Administration of the anti-CEACAM1 antibody T84.1 was efficient in blocking aggregation of B cells derived from MS patients. Along these lines, application of the monoclonal anti-CEACAM1 antibody mCC1 was able to inhibit CNS B cell aggregate formation and significantly attenuated established MS-like disease in mice in the absence of any adverse effects. CEACAM1 was co-expressed with the regulator molecule T cell immunoglobulin and mucin domain −3 (TIM-3) on B cells, a novel molecule that has recently been described to induce anergy in T cells. Interestingly, elevated coexpression on B cells coincided with an autoreactive T helper cell phenotype in MS patients. Overall, these data identify CEACAM1 as a clinically highly interesting target in MS pathogenesis and open new therapeutic avenues for the treatment of the disease.
B-Zellen spielen eine wichtige Rolle in der Pathogenese der Rheumatoiden Arthritis. Seit dem Jahr 2006 ist der Anti-CD20-Antikörper Rituximab, welcher eine passagere B-Zell-Depletion induziert, zur Therapie der Rheumatoiden Arthritis zugelassen. In dieser Arbeit wurde das variable Kappa- und Lambda-Leichtkettenrepertoire der CD19+CD27+ B-Gedächtniszellen bei einer Patientin mit aktiver Rheumatoider Arthritis vor und nach B-Zell-Depletion durch Rituximab verglichen. Hierzu wurden nach der Einzelzellsortierung von mononuklären Zellen des peripheren Blutes die Rearrangements des Kappa- und Lambda-Leichtkettenrepertoires amplifiziert, sequenziert und analysiert. Die gefundenen Daten sprechen für die Neubildung eines diversen, polyklonalen und hochmutierten Kappa- und Lambda-Leichtkettenrepertoires. Somit ist davon auszugehen, dass nach der CD20+ B-Zell-Depletion ein funktionsfähiges Repertoire entsteht, welches keine Restriktion für die Infektabwehr aufweist.
Genome wide association studies (GWAS) have identified Clec16a as disease suscepti-bility gene for numerous auto-immune disorders in particular type 1 diabetes. In spite of this strong genetic link, the role of Clec16a for immune regulation continues to be largely unknown. To study the function of Clec16a in an environment susceptible to autoimmune diseases a Clec16a deficient non obese diabetic (NOD) mouse strain was generated by means of lentiviral RNA interference. Clec16a knock down (KD) mice prove to be strongly protected against developing type 1 diabetes, an effect that is mediated by hyporeactive T effector cells. T cell hyporeactivity seems to result from an impairment of proximal TCR signalling and its cause is likely to be external to T cells. Given evidence on the involvement of the Clec16a Drosophila ortholog ema in endo- and autophagosomal processes, alterations in peripheral and/or central antigen presenting cells appeared to be potential reasons for the observed T cell hyporeactivity. While we are not able to identify any changes in quantity and quality of peripheral antigen presenting cells due to Clec16a silencing activation status of thymic epithelial cells in Clec16a KD mice deviates from NOD WT. The findings presented here suggest that thymic T cell development is affected by Clec16a variation. Such a relationship could explain the genetic association between Clec16a variations in humans and susceptibility to immune-mediated diseases, yet further investigations are needed to confirm this notion.
Multiple sclerosis is an autoimmune disease of the central nervous system characterized by inflammatory, demyelinating lesions and neuronal death. Formerly regarded as a variant of MS, neuromyelitis optica (NMO)/Devic’s disease is now recognized as a distinct neurological disorder exhibiting characteristic inflammatory and demyelinated foci in the optic nerves and the spinal cord sparing the brain. With the introduction of the double-transgenic “Devic mouse” model featuring spontaneous, adjuvant-free incidence of autoimmune neuroinflammation due to the interaction of transgenic MOG-specific T and B cells, a promising tool was found for the analysis of factors triggering or preventing autoimmunity. The co-inhibitory molecule B7-H1 has been proposed to contribute to the maintenance of peripheral tolerance and to confine autoimmune inflammatory damage via the PD-1/B7-H1 pathway. Compared to Devic B7-H1+/+ mice, Devic B7-H1-/- mice developed clinical symptoms with a remarkably higher incidence rate and faster kinetics emphasized by deteriorated disease courses and a nearly quadrupled mortality rate. Remarkably enlarged immune-cell accumulation in the CNS of Devic B7-H1-/- mice, in particular of activated MOG-specific CD4+ T cells, correlated with the more severe clinical features. Our studies showed that the CNS not only was the major site of myelin-specific CD4+ T-cell activation but also that B7-H1 expression within the target organ significantly influenced T-cell activation and differentiation levels. Analysis at disease maximum revealed augmented accumulation of MOG-specific CD4+ T cells in the peripheral lymphoid organs of Devic B7-H1-/- mice partly due to increased T-cell proliferation rates. Transgenic MOG-specific B cells of Devic B7-H1-/- mice activated MOG-specific CD4+ T cells more efficiently than B cells of Devic B7-H1+/+ mice. This observation indicated a relevant immune-modulating role of B7-H1 on APCs (antigen-presenting cells) in this mouse model. We also assumed altered thymic selection processes to be involved in increased peripheral CD4+ T-cell numbers of Devic B7-H1-/- mice as we found more thymocytes expressing the transgenic MOG-specific T-cell receptor (TCR). Moreover, preliminary in vitro experiments hinted on an enhanced survival of TCRMOG-transgenic CD4+ T cells of Devic B7-H1-/- mice; a mechanism that might as well have led to higher peripheral T-cell accumulation. Elevated levels of MOG-specific CD4+ T cells in the periphery of Devic B7-H1-/- mice could have entailed the higher quantities in the CNS. However, mechanisms such as CNS-specific proliferation and/or apoptosis/survival could also have contributed. This should be addressed in future investigations. Judging from in vitro migration assays and adoptive transfer experiments on RAG-1-/- recipient mice, migratory behavior of MOG-specific CD4+ T cells of Devic B7-H1+/+ and Devic B7-H1-/- mice seemed not to differ. However, enhanced expression of the transmigration-relevant integrin LFA-1 on CD4+ T cells in young symptom-free Devic B7-H1-/- mice might hint on temporally differently pronounced transmigration capacities during the disease course. Moreover, we attributed the earlier conversion of CD4+ T cells into Th1 effector cells in Devic B7-H1-/- mice during the initiation phase to the lack of co-inhibitory signaling via PD-1/B7-H1 possibly leading to an accelerated disease onset. Full blown autoimmune inflammatory processes could have masked these slight effects of B7-H1 in the clinical phase. Accordingly, at peak of the disease, Th1 and Th17 effector functions of peripheral CD4+ T cells were comparable in both mouse groups. Moreover, judging from titers of MOG-specific IgG1 and IgM antibodies, alterations in humoral immunity were not detected. Therefore, clinical differences could not be explained by altered T-cell or B-cell effector functions at disease maximum. B7-H1 rather seemed to take inhibitory effect in the periphery during the initiation phase only and consistently within the target organ by parenchymal expression. Our observations indicate that B7-H1 plays a relevant role in the regulation of T-cell responses in this mouse model for spontaneous CNS autoimmunity. By exerting immune-modulating effects in the preclinical as well as the clinical phase of the disease, B7-H1 contributed to the confinement of the immunopathological tissue damage in Devic B7-H1+/+ mice mirrored by later disease onsets and lower disease scores. As a model for spontaneous autoimmunity featuring a close to 100 % incidence rate, the Devic B7-H1-/- mouse may prove instrumental in clarifying disease-triggering and -limiting factors and in validating novel therapeutic approaches in the field of autoimmune neuroinflammation, in particular the human Devic’s disease.
Die Multiple Sklerose (MS) ist eine schwere, momentan noch unheilbare Autoimmunerkrankung des Zentralnervensystems, die weltweit ca. 1 Mio. Menschen betrifft. Da die zur Zeit verfügbaren, anti-inflammatorischen und immunsuppressiven Therapieformen lediglich krankheitsverzögernd wirken, ist es Gegenstand intensiver Forschungsbemühungen, Möglichkeiten zur spezifischen Interferenz mit bei der MS ablaufenden Pathomechanismen zu ergründen und im Tiermodell zu testen. Das von uns für diese Arbeit verwendete Mausmodell einer CD8+ T-Zell vermittelten Experimentellen Autoimmunen Enzephalomyelitis (EAE) trägt dabei neuen Erkenntnissen Rechnung, die zeigen, dass zytotoxische T-Lymphozyten bei der Pathogenese der humanen MS von entscheidender Bedeutung sind. Es handelt sich um doppelt transgene Nachkommen von Mäusen, die das Modell-Antigen Ovalbumin (OVA) unter der Kontrolle eines Oligodendrozyten (ODC-)-spezifischen MBP-Promotors im ZNS exprimieren, und Mäusen, die Ovalbumin-spezifische CD8+ T-Zellen besitzen (OT-I Zellen). Es kommt in diesem Modell zur Autoantigenerkennung durch die CD8+ T-Zellen mit konsekutiver Ausbildung einer fulminanten, letal verlaufenden EAE. Ziel der vorliegenden Arbeit war es nun, die therapeutische Potenz des monoklonalen Antikörpers 25-D1.16 zu evaluieren, der gegen das Autoantigen Ovalbumin in Kombination mit einem MHC-I-Molekül gerichtet ist. Mit Hilfe von FACS-Analysen und Fluoreszenz-Mikroskopie konnten wir zunächst bestätigen, dass 25-D1.16 spezifisch den Komplex aus dem Peptid SIINFEKL (antigenes Epitop von Ovalbumin) gebunden an ein MHC-I-Molekül (H-2Kb) erkennt. In nachfolgenden in vitro Versuchen wurde der Einfluss des Antikörpers auf Aktivierung und Proliferation von durch SIINFEKL:MHC-I-Komplex stimulierten OT-I Zellen untersucht. Es wurden hierfür Zellproliferation (Proliferations-Assays), Expression des Oberflächenmoleküls CD69 (FACS-Analysen) sowie IFN-γ-Sekretion (ELISA) gemessen. In Gegenwart von 25-D1.16 zeigte sich durchweg eine hochsignifikante Reduktion der jeweiligen Proliferations-/Aktivierungsmarker. Wir konnten somit in vitro zeigen, dass der gegen das Autoantigen Ovalbumin/H-2Kb gerichtete, monoklonale Antikörper 25-D1.16 kompetitiv die Aktivierung und Proliferation entsprechender T-Lymphozyten inhibieren kann. Um diese Daten in vivo zu validieren und die pathogenetische Relevanz zu überprüfen, haben wir ODC-OVA/OT-I doppelt transgenen Mäusen verschiedene Dosen von 25-D1.16 vor Auftreten erster EAE-Symptome einmalig intraperitoneal verabreicht. Anschließend wurde der Krankheitsverlauf klinisch beurteilt. Im EAE-Stadium 4 ohne Besserungstendenz oder bei Versuchsende wurden außerdem histologische Schnitte des Zentralnervensystems angefertigt, gefärbt (H.E., CD3, Mac-3, Luxol Fast Blue/PAS) und mit unbehandelten Tieren verglichen. Ein Teil der ODC-OVA/OT-I doppelt transgenen Tiere blieb nach Applikation des Antikörpers völlig gesund, während bei einem anderen Teil der Ausbruch der EAE zwar nicht vollständig verhindert, ihr Schweregrad aber deutlich gemildert wurde. Der Effekt der Antikörpertherapie war jedoch nicht nur klinisch, sondern auch histopathologisch überzeugend. So zeigte das Zentralnervensystem erfolgreich therapierter Mäuse eine weitgehend bis vollständig intakte Gewebsarchitektur (H.E.-Färbung) mit im Vergleich zu unbehandelten Mäusen drastisch reduzierter OT-I Zell- und Makrophagen/Mikroglia-Infiltration (Immunhistochemie CD3 und Mac-3). In der Luxol Fast Blue/PAS-Färbung fanden sich keinerlei Entmarkungsherde sondern durchgängig myelinisierte Axone. Es gelang uns somit durch hohe Antikörperdosen (500 μg pro ODC-OVA/OT-I doppelt transgener Maus) bei 83 % der behandelten Versuchstiere den Ausbruch der EAE ganz zu verhindern bzw. deren Verlauf deutlich abzumildern. Zusammenfassend beschreiben wir hier erstmals die antigen-spezifische Therapie einer CD8+ T-Zell mediierten EAE mittels eines gegen Peptid:MHC-I-Komplex gerichteten, monoklonalen Antikörpers. Durch Interferenz mit der Erkennung des Autoantigens durch die CD8+ T-Zellen waren wir in vivo in der Lage, den Pathomechanismus der EAE zu inhibieren. Hieraus ergibt sich ein vielversprechendes Behandlungskonzept für die Therapie der Multiplen Sklerose am Menschen.