The role of thymic antigen presenting cells and T cell intrinsic factors in the development of Foxp3+<<[Foxp3 hoch+]>> regulatory T cells

Ein Großteil der regulatorischen T Zellen (Treg) der Maus ist thymischen Ursprungs. Erklärungsmodelle dafür beinhalten unter anderem Thymus spezifische Zell-extrinsische Signale, möglicherweise in einer durch spezialisierte Antigen präsentierende Zellen (APC) geschaffenen Nische. Zusätzlich oder alternativ dazu könnten T-Zell-intrinsische Faktoren die Entwicklung von regulatorischen T Zellen im Thymus beeinflussen. Im Rahmen dieser Arbeit wurden monoklonale T Zellen unterschiedlicher Entwicklungsstadien in Thymi transferiert, die das spezifische Antigen für diese T Zellen exprimieren. Die Effizienz, mit der Zellen sich in Treg entwickelten, korrelierte dabei invers mit dem Reifegrad der transferierten Zellen. Diese verstärkte Neigung unreifer T Zellen in regulatorische T Zellen zu differenzieren konnte in einem APC-freien System, das nur einen T-Rezeptor-Stimulus und Interleukin-2 beinhaltet, bestätigt werden. Weiters konnte gezeigt werden, dass sowohl Thymus Epithelzellen, als auch unterschiedliche Typen von thymischen Dendritischen Zellen die Entwicklung von Treg aus unreifen Thymozyten induzieren, sofern optimale Antigen Konzentrationen vorherrschten. Dies deutet darauf hin, dass die Quantität und nicht die Qualität T-Zell-extrinsischer Signale entscheidend für die intrathymische Entwicklung von Treg ist. Zusammenfassend deuten die in dieser Studie vorgestellten Resultate darauf hin, dass der intrathymische Ursprung eines Großteils der Treg das Resultat einer verstärkten Prädisposition unreifer Thymozyten ist, in Treg zu differenzieren. Die dafür notwendigen extrinsischen Signale können dabei sowohl von hämatopoietischen als auch epithelialen APC geliefert werden.The majority of regulatory T cells (Tregs) are believed to be of thymic origin. It has been hypothesized that this may result from unique intrathymic environmental cues, possibly requiring a dedicated antigen presenting cell (APC). However, T cell intrinsic developmental regulation of the susceptibility to Treg differentiation remains a mutually non-exclusive scenario. We found that upon exposure of monoclonal T cells of sequential developmental stages to a thymic microenvironment expressing cognate antigen, the efficiency of Treg induction inversely correlated with progressive maturation. This inclination of immature thymocytes towards Treg differentiation was even seen in an APC-free in vitro system providing only TCR stimulation and IL-2. In support of quantitative but not qualitative features of external cues being critical, thymic epithelial cells as well as different thymic dendritic cell (DC) -subtypes efficiently induced Treg development of immature thymocytes, albeit at strikingly different optimal doses of cognate antigen. We propose that the intrinsically high predisposition of immature thymocytes to Treg development may contribute to the predominantly thymic origin of the Treg repertoire. The underlying instructive stimulus, however, does not require unique features of a dedicated APC and can be delivered by hematopoietic as well as epithelial thymic stromal cells

B7/CD28 in Central Tolerance: Costimulation Promotes Maturation of Regulatory T Cell Precursors and Prevents Their Clonal Deletion

According to the “two-step model,” the intrathymic generation of CD4+ regulatory T (Treg) cells segregates into a first, T cell receptor (TCR)-driven phase and a second, cytokine-dependent phase. The initial TCR stimulus gives rise to a CD25+Foxp3− developmental intermediate. These precursors subsequently require cytokine signaling to establish the mature CD25+Foxp3+ Treg cell phenotype. In addition, costimulation via CD28/B7 (CD80/86) axis is important for the generation of a Treg cell repertoire of normal size. Recent data suggest that CD28 or B7 deficient mice lack CD25+Foxp3− Treg cell progenitors. However, these data leave open whether costimulation is also required at subsequent stages of Treg differentiation. Also, the fate of “presumptive” Treg cells carrying a permissive TCR specificity in the absence of costimulation remains to be established. Here, we have used a previously described TCR transgenic model of agonist-driven Treg differentiation in order to address these issues. Intrathymic adoptive transfer of Treg precursors indicated that costimulation is dispensable once the intermediate CD25+Foxp3− stage has been reached. Furthermore, lack of costimulation led to the physical loss of presumptive Treg cells rather than their escape from central tolerance and differentiation into the conventional CD4+ T cell lineage. Our findings suggest that CD28 signaling does not primarily operate through enhancing the TCR signal strength in order to pass the threshold intensity required to initiate Treg cell specification. Instead, costimulation seems to deliver unique and qualitatively distinct signals that coordinately foster the developmental progression of Treg precursors and prevent their negative selection

Effectiveness of multi-professional educational interventions to train Comprehensive Geriatric Assessment (CGA) – a Systematic Review

Introduction: As the world population ages, health and social care professionals are increasingly confronted with patients with chronic long-term conditions and multimorbidity, requiring an extensive assessment and integrated care management strategy. The aim of this paper was to systematically collect and assess evidence of interprofessional education and training strategies for Comprehensive Geriatric Assessment (CGA) to build a competent health workforce. Methods: A systematic review was conducted according to PRISMA guidelines and the databases Medline, CINAHL, Cochrane and Embase were searched for studies illustrating effectiveness of educational interventions for teaching and training CGA in an interprofessional context. Results: Based on 21 identified studies, a great variability and heterogeneity in duration, setting and design of the interventions was identified. Promising results were found in the domains analysed, ranging from knowledge and skills; practices and behaviour; patient health outcomes; attitudes and perceptions to collaboration and quality of care. Discussion: Education and training of transversal skills within a continuous learning approach is key to equip the health care workforce for successful CGA performance in an interprofessional environment. Conclusion: Further research in this field is recommended to strengthen the evidence-base towards development of a resilient and integrated health care workforce for an ageing population. Kurzfassung Hintergrund: Aufgrund der zunehmenden Alterung der Weltbevölkerung sehen sich Fachkräfte des Gesundheits- und Sozialwesens immer häufiger mit Patient*innen mit chronischen Erkrankungen (bzw. Langzeiterkrankungen) und Multimorbidität, welche eine umfassende Beurteilung und eine integrierte Versorgungsmanagementstrategie erfordern, konfrontiert. Ziel der vorliegenden Arbeit war es, systematisch Evidenz für interprofessionelle Aus- und Weiterbildungsstrategien für ein Comprehensive Geriatric Assessment (CGA) zu sammeln und zu bewerten, um Kompetenz im Gesundheits- und Sozialwesen zu generieren. Methodik: Es wurde eine systematische Übersichtsarbeit gemäß den PRISMA-Richtlinien durchgeführt und die Datenbanken Medline, CINAHL, Cochrane und Embase im Zuge dessen nach Studien durchsucht, welche die Wirksamkeit von Bildungsmaßnahmen zur Vermittlung und Ausbildung von CGA in einem interprofessionellen Kontext belegen. Ergebnisse: Basierend auf 21 identifizierten Studien wurde eine große Variabilität und Heterogenität in Bezug auf Dauer, Setting und Design der Interventionen festgestellt. Vielversprechende Ergebnisse wurden in den analysierten Bereichen gefunden, welche von Wissen und Fähigkeiten, Praktiken und Verhalten, gesundheitlichen Ergebnissen für Patient*innen, Einstellungen und Wahrnehmungen bis hin zu Zusammenarbeit und Qualität der Versorgung reichen. Diskussion: Die Aus- und Weiterbildung von transversalen Fähigkeiten im Rahmen eines kontinuierlichen Lernansatzes ist der Schlüssel dazu, Angehörige der Gesundheits- und Sozialprofessionen mit entsprechendem Werkzeug auszustatten, um geriatrische Assessments (CGA) erfolgreich im interprofessionellen Umfeld durchführen zu können. Schlussfolgerung: Es besteht der Bedarf für weitere Forschungsvorhaben in diesem Bereich, um die Evidenzbasis für die Entwicklung eines zuverlässigen, integrierten Gesundheitspersonals für eine alternde Bevölkerung zu stärken. Schlüsselwörter: Integrierte Versorgung; Comprehensive Geriatric Assessment; Ausund Weiterbildung; interprofessionelle Bildung; Alterun

Human soluble ACE2 improves the effect of remdesivir in SARS-CoV-2 infection

There is a critical need for safe and effective drugs for COVID-19. Only remdesivir has received authorization for COVID-19 and has been shown to improve outcomes but not decrease mortality. However, the dose of remdesivir is limited by hepatic and kidney toxicity. ACE2 is the critical cell surface receptor for SARS-CoV-2. Here, we investigated additive effect of combination therapy using remdesivir with recombinant soluble ACE2 (high/low dose) on Vero E6 and kidney organoids, targeting two different modalities of SARS-CoV-2 life cycle: cell entry via its receptor ACE2 and intracellular viral RNA replication. This combination treatment markedly improved their therapeutic windows against SARS-CoV-2 in both models. By using single amino-acid resolution screening in haploid ES cells, we report a singular critical pathway required for remdesivir toxicity, namely, Adenylate Kinase 2. The data provided here demonstrate that combining two therapeutic modalities with different targets, common strategy in HIV treatment, exhibit strong additive effects at sub-toxic concentrations. Our data lay the groundwork for the study of combinatorial regimens in future COVID-19 clinical trials

ACE2 is the critical in vivo receptor for SARS-CoV-2 in a novel COVID-19 mouse model with TNF-and IFN?-driven immunopathology

Despite tremendous progress in the understanding of COVID-19, mechanistic insight into immunological, disease-driving factors remains limited. We generated maVie16, a mouse-adapted SARS-CoV-2, by serial passaging of a human isolate. In silico modeling revealed how only three Spike mutations of maVie16 enhanced interaction with murine ACE2. maVie16 induced profound pathology in BALB/c and C57BL/6 mice, and the resulting mouse COVID-19 (mCOVID-19) replicated critical aspects of human disease, including early lymphopenia, pulmonary immune cell infiltration, pneumonia, and specific adaptive immunity. Inhibition of the proinflammatory cyto-kines IFN? and TNF substantially reduced immunopathology. Importantly, genetic ACE2-deficiency completely prevented mCOVID-19 development. Finally, inhalation therapy with recombinant ACE2 fully protected mice from mCOVID-19, revealing a novel and efficient treatment. Thus, we here present maVie16 as a new tool to model COVID-19 for the discovery of new therapies and show that disease severity is determined by cytokine-driven immunopathology and critically dependent on ACE2 in vivo. © Gawish et al

Clinical grade ACE2 as a universal agent to block SARS-CoV-2 variants

The recent emergence of multiple SARS-CoV-2 variants has caused considerable concern due to both reduced vaccine efficacy and escape from neutralizing antibody therapeutics. It is, therefore, paramount to develop therapeutic strategies that inhibit all known and future SARS-CoV-2 variants. Here, we report that all SARS-CoV-2 variants analyzed, including variants of concern (VOC) Alpha, Beta, Gamma, Delta, and Omicron, exhibit enhanced binding affinity to clinical grade and phase 2 tested recombinant human soluble ACE2 (APN01). Importantly, soluble ACE2 neutralized infection of VeroE6 cells and human lung epithelial cells by all current VOC strains with markedly enhanced potency when compared to reference SARS-CoV-2 isolates. Effective inhibition of infections with SARS-CoV-2 variants was validated and confirmed in two independent laboratories. These data show that SARS-CoV-2 variants that have emerged around the world, including current VOC and several variants of interest, can be inhibited by soluble ACE2, providing proof of principle of a pan-SARS-CoV-2 therapeutic

Signaling mechanisms, interaction partners, and target genes of STAT6

Like other members of the signal transducer and activator of transcription (STAT) family of proteins, STAT6 has a dual role as signaling molecule and transcription factor. STAT6 is tightly connected to IL-4 and IL-13 signaling, and plays a key role in TH2 polarization of the immune system, as studies on knockout mice have illustrated impressively. The last 5 years have yielded many new insights into various aspects of STAT6 signaling. While the canonical view of STAT6 activation and biology remains largely unaltered, significant progress has been made in the identification of factors involved in STAT6 activity and STAT6-mediated gene regulation. About 35 different STAT6 target genes have been identified to date, many of which are involved in TH2-associated processes. This review summarizes the existing data on STAT6. Older landmark studies are discussed, as well as surprising recent additions, like hints on inactive STAT6 dimers and the discovery of novel STAT6 isoforms. There is a particular focus on molecular aspects such as modifications of STAT6 and regulation of STAT6-dependent genes, since studies on these aspects have been particularly fruitful during the last few years

Identification of a distal tandem STAT6 element within the CCL17 locus

The CC chemokine ligand CCL17 is one of the major chemo-attractants for TH2 cells. Interleukin-4–induced activation of CCL17 expression was recently demonstrated to result from two STAT6 motifs in the proximal promoter. Here we provide evidence that a distal tandem STAT6 element further elevates expression from the CCL17 locus approximately twofold. This is demonstrated by reporter gene assays using different fragments of the CCL17 promoter and the region 2.5 kb upstream from the transcriptional start site. By electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation experiments, we show that STAT6 binds to the motifs in vitro and in vivo, respectively. Insertion of nucleotide exchanges into the STAT6 core motifs results in diminished promoter activation and abrogated STAT6 binding, as demonstrated by reporter gene and EMSA studies. Collectively these data reveal an additional element involved in the regulation of CCL17 expression