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Membrane lymphotoxin-α\(_2\)β is a novel tumor necrosis factor (TNF) receptor 2 (TNFR2) agonist
(2021)
In the early 1990s, it has been described that LTα and LTβ form LTα\(_2\)β and LTαβ\(_2\) heterotrimers, which bind to TNFR1 and LTβR, respectively. Afterwards, the LTαβ\(_2\)–LTβR system has been intensively studied while the LTα\(_2\)β–TNFR1 interaction has been ignored to date, presumably due to the fact that at the time of identification of the LTα\(_2\)β–TNFR1 interaction one knew already two ligands for TNFR1, namely TNF and LTα. Here, we show that LTα\(_2\)β interacts not only with TNFR1 but also with TNFR2. We furthermore demonstrate that membrane-bound LTα\(_2\)β (memLTα\(_2\)β), despite its asymmetric structure, stimulates TNFR1 and TNFR2 signaling. Not surprising in view of its ability to interact with TNFR2, LTα\(_2\)β is inhibited by Etanercept, which is approved for the treatment of rheumatoid arthritis and also inhibits TNF and LTα.
Aspergillus fumigatus causes life-threatening opportunistic infections in immunocompromised patients. As therapeutic outcomes of invasive aspergillosis (IA) are often unsatisfactory, the development of targeted immunotherapy remains an important goal. Linking the innate and adaptive immune system, dendritic cells are pivotal in anti-Aspergillus defense and have generated interest as a potential immunotherapeutic approach in IA. While monocyte-derived dendritic cells (moDCs) require ex vivo differentiation, antigen-pulsed primary myeloid dendritic cells (mDCs) may present a more immediate platform for immunotherapy. To that end, we compared the response patterns and cellular interactions of human primary mDCs and moDCs pulsed with an A. fumigatus lysate and two A. fumigatus proteins (CcpA and Shm2) in a serum-free, GMP-compliant medium. CcpA and Shm2 triggered significant upregulation of maturation markers in mDCs and, to a lesser extent, moDCs. Furthermore, both A. fumigatus proteins elicited the release of an array of key pro-inflammatory cytokines including TNF-α, IL-1β, IL-6, IL-8, and CCL3 from both DC populations. Compared to moDCs, CcpA- and Shm2-pulsed mDCs exhibited greater expression of MHC class II antigens and stimulated stronger proliferation and IFN-γ secretion from autologous CD4\(^+\) and CD8\(^+\) T-cells. Moreover, supernatants of CcpA- and Shm2-pulsed mDCs significantly enhanced the oxidative burst in allogeneic neutrophils co-cultured with A. fumigatus germ tubes. Taken together, our in vitro data suggest that ex vivo CcpA- and Shm2-pulsed primary mDCs have the potential to be developed into an immunotherapeutic approach to tackle IA.
Understanding the mechanisms of early invasion and epithelial defense in opportunistic mold infections is crucial for the evaluation of diagnostic biomarkers and novel treatment strategies. Recent studies revealed unique characteristics of the immunopathology of mucormycoses. We therefore adapted an alveolar Transwell® A549/HPAEC bilayer model for the assessment of epithelial barrier integrity and cytokine response to Rhizopus arrhizus, Rhizomucor pusillus, and Cunninghamella bertholletiae. Hyphal penetration of the alveolar barrier was validated by 18S ribosomal DNA detection in the endothelial compartment. Addition of dendritic cells (moDCs) to the alveolar compartment led to reduced fungal invasion and strongly enhanced pro-inflammatory cytokine response, whereas epithelial CCL2 and CCL5 release was reduced. Despite their phenotypic heterogeneity, the studied Mucorales species elicited the release of similar cytokine patterns by epithelial and dendritic cells. There were significantly elevated lactate dehydrogenase concentrations in the alveolar compartment and epithelial barrier permeability for dextran blue of different molecular weights in Mucorales-infected samples compared to Aspergillus fumigatus infection. Addition of monocyte-derived dendritic cells further aggravated LDH release and epithelial barrier permeability, highlighting the influence of the inflammatory response in mucormycosis-associated tissue damage. An important focus of this study was the evaluation of the reproducibility of readout parameters in independent experimental runs. Our results revealed consistently low coefficients of variation for cytokine concentrations and transcriptional levels of cytokine genes and cell integrity markers. As additional means of model validation, we confirmed that our bilayer model captures key principles of Mucorales biology such as accelerated growth in a hyperglycemic or ketoacidotic environment or reduced epithelial barrier invasion upon epithelial growth factor receptor blockade by gefitinib. Our findings indicate that the Transwell® bilayer model provides a reliable and reproducible tool for assessing host response in mucormycosis.
Objectives
The severity of Coronavirus Disease 2019 (COVID-19) is largely determined by the immune response. First studies indicate altered lymphocyte counts and function. However, interactions of pro- and anti-inflammatory mechanisms remain elusive. In the current study we characterized the immune responses in patients suffering from severe COVID-19-induced acute respiratory distress syndrome (ARDS).
Methods
This was a single-center retrospective study in patients admitted to the intensive care unit (ICU) with confirmed COVID-19 between March 14th and May 28th 2020 (n = 39). Longitudinal data were collected within routine clinical care, including flow-cytometry of lymphocyte subsets, cytokine analysis and growth differentiation factor 15 (GDF-15). Antibody responses against the receptor binding domain (RBD) of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Spike protein were analyzed.
Results
All patients suffered from severe ARDS, 30.8% died. Interleukin (IL)-6 was massively elevated at every time-point. The anti-inflammatory cytokine IL-10 was concomitantly upregulated with IL-6. The cellular response was characterized by lymphocytopenia with low counts of CD8+ T cells, natural killer (NK) and naïve T helper cells. CD8+ T and NK cells recovered after 8 to 14 days. The B cell system was largely unimpeded. This coincided with a slight increase in anti-SARS-CoV-2-Spike-RBD immunoglobulin (Ig) G and a decrease in anti-SARS-CoV-2-Spike-RBD IgM. GDF-15 levels were elevated throughout ICU treatment.
Conclusions
Massively elevated levels of IL-6 and a delayed cytotoxic immune defense characterized severe COVID-19-induced ARDS. The B cell response and antibody production were largely unimpeded. No obvious imbalance of pro- and anti-inflammatory mechanisms was observed, with elevated GDF-15 levels suggesting increased tissue resilience.
Background
Surfactant replacement therapy is the standard of care for the prevention and treatment of neonatal respiratory distress syndrome. New generation synthetic surfactants represent a promising alternative to animal-derived surfactants. CHF5633, a new generation reconstituted synthetic surfactant containing SP-B and SP-C analogs and two synthetic phospholipids has demonstrated biophysical effectiveness in vitro and in vivo. While several surfactant preparations have previously been ascribed immunomodulatory capacities, in vitro data on immunomodulation by CHF5633 are limited, so far. Our study aimed to investigate pro- and anti-inflammatory effects of CHF5633 on native and LPS-stimulated human adult monocytes.
Methods
Highly purified adult CD14\(^{+}\) cells, either native or simultaneously stimulated with LPS, were exposed to CHF5633, its components, or poractant alfa (Curosurf\(^{®}\)). Subsequent expression of TNF-α, IL-1β, IL-8 and IL-10 mRNA was quantified by real-time quantitative PCR, corresponding intracellular cytokine synthesis was analyzed by flow cytometry. Potential effects on TLR2 and TLR4 mRNA and protein expression were monitored by qPCR and flow cytometry.
Results
Neither CHF5633 nor any of its components induced inflammation or apoptosis in native adult CD14\(^{+}\) monocytes. Moreover, LPS-induced pro-inflammatory responses were not aggravated by simultaneous exposure of monocytes to CHF5633 or its components. In LPS-stimulated monocytes, exposure to CHF5633 led to a significant decrease in TNF-α mRNA (0.57 ± 0.23-fold, p = 0.043 at 4h; 0.56 ± 0.27-fold, p = 0.042 at 14h). Reduction of LPS-induced IL-1β mRNA expression was not significant (0.73 ± 0.16, p = 0.17 at 4h). LPS-induced IL-8 and IL-10 mRNA and protein expression were unaffected by CHF5633. For all cytokines, the observed CHF5633 effects paralleled a Curosurf®-induced modulation of cytokine response. TLR2 and TLR4 mRNA and protein expression were not affected by CHF5633 and Curosurf®, neither in native nor in LPS-stimulated adult monocytes.
Conclusion
The new generation reconstituted synthetic surfactant CHF5633 was tested for potential immunomodulation on native and LPS-activated adult human monocytes. Our data confirm that CHF5633 does not exert unintended pro-inflammatory effects in both settings. On the contrary, CHF5633 significantly suppressed TNF-α mRNA expression in LPS-stimulated adult monocytes, indicating potential anti-inflammatory effects.
Aging is an independent risk factor for cardiovascular diseases and therefore of particular interest for the prevention of cardiovascular events. However, the mechanisms underlying vascular aging are not well understood. Since carcinoembryonic antigen‐related cell adhesion molecule 1 (CEACAM1) is crucially involved in vascular homeostasis, we sought to identify the role of CEACAM1 in vascular aging. Using human internal thoracic artery and murine aorta, we show that CEACAM1 is upregulated in the course of vascular aging. Further analyses demonstrated that TNF‐α is CEACAM1‐dependently upregulated in the aging vasculature. Vice versa, TNF‐α induces CEACAM1 expression. This results in a feed‐forward loop in the aging vasculature that maintains a chronic pro‐inflammatory milieu. Furthermore, we demonstrate that age‐associated vascular alterations, that is, increased oxidative stress and vascular fibrosis, due to increased medial collagen deposition crucially depend on the presence of CEACAM1. Additionally, age‐dependent upregulation of vascular CEACAM1 expression contributes to endothelial barrier impairment, putatively via increased VEGF/VEGFR‐2 signaling. Consequently, aging‐related upregulation of vascular CEACAM1 expression results in endothelial dysfunction that may promote atherosclerotic plaque formation in the presence of additional risk factors. Our data suggest that CEACAM1 might represent an attractive target in order to delay physiological aging and therefore the transition to vascular disorders such as atherosclerosis.
Each positive well in ELISPOT assays contains spots of variable sizes that can range from tens of micrometers up to a millimeter in diameter. Therefore, when it comes to counting these spots the decision on setting the lower and the upper spot size thresholds to discriminate between non-specific background noise, spots produced by individual T cells, and spots formed by T cell clusters is critical. If the spot sizes follow a known statistical distribution, precise predictions on minimal and maximal spot sizes, belonging to a given T cell population, can be made. We studied the size distributional properties of IFN-γ, IL-2, IL-4, IL-5 and IL-17 spots elicited in ELISPOT assays with PBMC from 172 healthy donors, upon stimulation with 32 individual viral peptides representing defined HLA Class I-restricted epitopes for CD8 cells, and with protein antigens of CMV and EBV activating CD4 cells. A total of 334 CD8 and 80 CD4 positive T cell responses were analyzed. In 99.7% of the test cases, spot size distributions followed Log Normal function. These data formally demonstrate that it is possible to establish objective, statistically validated parameters for counting T cell ELISPOTs.
Immature or semi-mature dendritic cells (DCs) represent tolerogenic maturation stages that can convert naive T cells into Foxp3\(^{+}\) induced regulatory T cells (iTreg). Here we found that murine bone marrow-derived DCs (BM-DCs) treated with cholera toxin (CT) matured by up-regulating MHC-II and costimulatory molecules using either high or low doses of CT (CT\(^{hi}\), CT\(^{lo}\)) or with cAMP, a known mediator CT signals. However, all three conditions also induced mRNA of both isoforms of the tolerogenic molecule cytotoxic T lymphocyte antigen 2 (CTLA-2α and CTLA-2β). Only DCs matured under CT\(^{hi}\) conditions secreted IL-1β, IL-6 and IL-23 leading to the instruction of Th17 cell polarization. In contrast, CT\(^{lo}\)- or cAMP-DCs resembled semi-mature DCs and enhanced TGF-β-dependent Foxp3\(^{+}\) iTreg conversion. iTreg conversion could be reduced using siRNA blocking of CTLA-2 and reversely, addition of recombinant CTLA-2α increased iTreg conversion in vitro. Injection of CT\(^{lo}\)- or cAMP-DCs exerted MOG peptide-specific protective effects in experimental autoimmune encephalomyelitis (EAE) by inducing Foxp3\(^{+}\) Tregs and reducing Th17 responses. Together, we identified CTLA-2 production by DCs as a novel tolerogenic mediator of TGF-β-mediated iTreg induction in vitro and in vivo. The CT-induced and cAMP-mediated up-regulation of CTLA-2 also may point to a novel immune evasion mechanism of Vibrio cholerae.
Background
Enteric glial cells (EGCs) are the main constituent of the enteric nervous system and share similarities with astrocytes from the central nervous system including their reactivity to an inflammatory microenvironment. Previous studies on EGC pathophysiology have specifically focused on mucosal glia activation and its contribution to mucosal inflammatory processes observed in the gut of inflammatory bowel disease (IBD) patients. In contrast knowledge is scarce on intestinal inflammation not locally restricted to the mucosa but systemically affecting the intestine and its effect on the overall EGC network.
Methods and Results
In this study, we analyzed the biological effects of a systemic LPS-induced hyperinflammatory insult on overall EGCs in a rat model in vivo, mimicking the clinical situation of systemic inflammation response syndrome (SIRS). Tissues from small and large intestine were removed 4 hours after systemic LPS-injection and analyzed on transcript and protein level. Laser capture microdissection was performed to study plexus-specific gene expression alterations. Upon systemic LPS-injection in vivo we observed a rapid and dramatic activation of Glial Fibrillary Acidic Protein (GFAP)-expressing glia on mRNA level, locally restricted to the myenteric plexus. To study the specific role of the GFAP subpopulation, we established flow cytometry-purified primary glial cell cultures from GFAP promotor-driven EGFP reporter mice. After LPS stimulation, we analyzed cytokine secretion and global gene expression profiles, which were finally implemented in a bioinformatic comparative transcriptome analysis. Enriched GFAP+ glial cells cultured as gliospheres secreted increased levels of prominent inflammatory cytokines upon LPS stimulation. Additionally, a shift in myenteric glial gene expression profile was induced that predominantly affected genes associated with immune response.
Conclusion and Significance
Our findings identify the myenteric GFAP-expressing glial subpopulation as particularly susceptible and responsive to acute systemic inflammation of the gut wall and complement knowledge on glial involvement in mucosal inflammation of the intestine.
Background
Natural surfactant preparations, commonly isolated from porcine or bovine lungs, are used to treat respiratory distress syndrome in preterm infants. Besides biophysical effectiveness, several studies have documented additional immunomodulatory properties. Within the near future, synthetic surfactant preparations may be a promising alternative. CHF5633 is a new generation reconstituted synthetic surfactant preparation with defined composition, containing dipalmitoyl-phosphatidylcholine, palmitoyl-oleoyl-phosphatidylglycerol and synthetic analogs of surfactant protein (SP-) B and SP-C. While its biophysical effectiveness has been demonstrated in vitro and in vivo, possible immunomodulatory abilities are currently unknown.
Aim
The aim of the current study was to define a potential impact of CHF5633 and its single components on pro- and anti-inflammatory cytokine responses in human CD4\(^+\) lymphocytes.
Methods
Purified human CD4\(^+\) T cells were activated using anti CD3/CD28 antibodies and exposed to CHF5633, its components, or to the well-known animal-derived surfactant Poractant alfa (Curosurf®). Proliferative response and cell viability were assessed using flow cytometry and a methylthiazolyldiphenyltetrazolium bromide colorimetric assay. The mRNA expression of IFNγ, IL-2, IL-17A, IL-22, IL-4, and IL-10 was measured by quantitative PCR, while intracellular protein expression was assessed by means of flow cytometry.
Results
Neither CHF5633 nor any of its phospholipid components with or without SP-B or SP-C analogs had any influence on proliferative ability and viability of CD4\(^+\) lymphocytes under the given conditions. IFNγ, IL-2, IL-17A, IL-22, IL-4, and IL-10 mRNA as well as IFNγ, IL-2, IL-4 and IL-10 protein levels were unaffected in both non-activated and activated CD4+ lymphocytes after exposure to CHF5633 or its constituents compared to non-exposed controls. However, in comparison to Curosurf®, expression levels of anti-inflammatory IL-4 and IL-10 mRNA were significantly increased in CHF5633 exposed CD4\(^+\) lymphocytes.
Conclusion
For the first time, the immunomodulatory capacity of CHF5633 on CD4\(^+\) lymphocytes was evaluated. CHF5633 did not show any cytotoxicity on CD4\(^+\) cells. Moreover, our in vitro data indicate that CHF5633 does not exert unintended pro-inflammatory effects on non-activated and activated CD4+ T cells. As far as anti-inflammatory cytokines are concerned, it might lack an overall reductive ability in comparison to animal-derived surfactants, potentially leaving pro- and anti-inflammatory cytokine response in balance.