A microbially produced AhR ligand promotes a Tph1-driven tolerogenic program in multiple sclerosis.

Multiple sclerosis is a debilitating autoimmune disease, characterized by chronic inflammation of the central nervous system. While the significance of the gut microbiome on multiple sclerosis pathogenesis is established, the underlining mechanisms are unknown. We found that serum levels of the microbial postbiotic tryptophan metabolite indole-3-carboxaldehyde (3-IAld) inversely correlated with disease duration in multiple sclerosis patients. Much like the host-derived tryptophan derivative L-Kynurenine, 3-IAld would bind and activate the Aryl hydrocarbon Receptor (AhR), which, in turn, controls endogenous tryptophan catabolic pathways. As a result, in peripheral lymph nodes, microbial 3-IAld, affected mast-cell tryptophan metabolism, forcing mast cells to produce serotonin via Tph1. We thus propose a protective role for AhR-mast-cell activation driven by the microbiome, whereby natural metabolites or postbiotics will have a physiological role in immune homeostasis and may act as therapeutic targets in autoimmune diseases.

Phenotype and oxidative burst of low-density neutrophil subpopulations are altered in common variable immunodeficiency patients.

Common variable immunodeficiency disorder (CVID) is the most common form of primary antibody immunodeficiency. Due to low antibody levels, CVID patients receive intravenous or subcutaneous immunoglobulin replacement therapy as treatment. CVID is associated with the chronic activation of granulocytes, including an increased percentage of low-density neutrophils (LDNs). In this study, we examined changes in the percentage of LDNs and the expression of their surface markers in 25 patients with CVID and 27 healthy donors (HD) after in vitro stimulation of whole blood using IVIg. An oxidative burst assay was used to assess the functionality of LDNs. CVID patients had increased both relative and absolute LDN counts with a higher proportion of mLDNs compared to iLDNs, distinguished based on the expression of CD10 and CD16. Immature LDNs in the CVID and HD groups had significantly reduced oxidative burst capacity compared to mature LDNs. Interestingly we observed reduced oxidative burst capacity, reduced expression of CD10 after stimulation of WB, and higher expression of PD-L1 in mature LDNs in CVID patients compared to HD cells. Our data indicate that that the functional characteristics of LDNs are closely linked to their developmental stage. The observed reduction in oxidative burst capacity in mLDNs in CVID patients could contribute to an increased susceptibility to recurrent bacterial infections among CVID patients.

Hepcidin and ferritin levels as markers of immune cell activation during septic shock, severe COVID-19 and sterile inflammation.

Introduction: Major clinically relevant inflammatory events such as septic shock and severe COVID-19 trigger dynamic changes in the host immune system, presenting promising candidates for new biomarkers to improve precision diagnostics and patient stratification. Hepcidin, a master regulator of iron metabolism, has been intensively studied in many pathologies associated with immune system activation, however these data have never been compared to other clinical settings. Thus, we aimed to reveal the dynamics of iron regulation in various clinical settings and to determine the suitability of hepcidin and/or ferritin levels as biomarkers of inflammatory disease severity. Cohorts: To investigate the overall predictive ability of hepcidin and ferritin, we enrolled the patients suffering with three different diagnoses - in detail 40 patients with COVID-19, 29 patients in septic shock and eight orthopedic patients who were compared to nine healthy donors and all cohorts to each other. Results: We showed that increased hepcidin levels reflect overall immune cell activation driven by intrinsic stimuli, without requiring direct involvement of infection vectors. Contrary to hepcidin, ferritin levels were more strongly boosted by pathogen-induced inflammation - in septic shock more than four-fold and in COVID-19 six-fold in comparison to sterile inflammation. We also defined the predictive capacity of hepcidin-to-ferritin ratio with AUC=0.79 and P = 0.03. Discussion: Our findings confirm that hepcidin is a potent marker of septic shock and other acute inflammation-associated pathologies and demonstrate the utility of the hepcidin-to-ferritin ratio as a predictor of mortality in septic shock, but not in COVID-19.

Influence of protein corona on the interaction of glycogen-siRNA constructs with ex vivo human blood immune cells.

Glycogen-nucleic acid constructs i.e., glycoplexes are emerging promising platforms for the alteration of gene expression and transcription. Understanding the interaction of glycoplexes with human blood components, such as serum proteins and peripheral blood mononuclear cells (PBMCs), is important to overcome immune cell activation and control biodistribution upon administration of the glycoplexes in vivo. Herein, we investigated the interactions of polyethylene glycol (PEG)ylated and non-PEGylated glycoplexes carrying siRNA molecules with PBMCs isolated from the blood of healthy donors. We found that both types of glycoplexes were non-toxic and were primarily phagocytosed by monocytes without triggering a pro-inflammatory interleukin 6 cytokine production. Furthermore, we investigated the role of the protein corona on controlling the internalization efficiency in immune cells - we found that the adsorption of serum proteins, in particular haptoglobin, alpha-1-antitrypsin and apolipoprotein A-II, onto the non-PEGylated glycoplexes, significantly reduced the uptake of the glycoplexes by PBMCs. Moreover, the non-PEGylated glycoplexes were efficient in the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) knockdown in monocytic THP-1 cell line. This study provides an insight into the rational design of glycogen-based nanocarriers for the safe delivery of siRNA without eliciting unwanted immune cell activation and efficient siRNA activity upon its delivery.

Triggering the nanophase separation of albumin through multivalent binding to glycogen for drug delivery in 2D and 3D multicellular constructs.

Engineered nanoparticles for the encapsulation of bioactive agents hold promise to improve disease diagnosis, prevention and therapy. To advance this field and enable clinical translation, the rational design of nanoparticles with controlled functionalities and a robust understanding of nanoparticle-cell interactions in the complex biological milieu are of paramount importance. Herein, a simple platform obtained through the nanocomplexation of glycogen nanoparticles and albumin is introduced for the delivery of chemotherapeutics in complex multicellular 2D and 3D systems. We found that the dendrimer-like structure of aminated glycogen nanoparticles is key to controlling the multivalent coordination and phase separation of albumin molecules to form stable glycogen-albumin nanocomplexes. The pH-responsive glycogen scaffold conferred the nanocomplexes the ability to undergo partial endosomal escape in tumour, stromal and immune cells while albumin enabled nanocomplexes to cross endothelial cells and carry therapeutic agents. Limited interactions of nanocomplexes with T cells, B cells and natural killer cells derived from human blood were observed. The nanocomplexes can accommodate chemotherapeutic drugs and release them in multicellular 2D and 3D constructs. The drugs loaded on the nanocomplexes retained their cytotoxic activity, which is comparable with the activity of the free drugs. Cancer cells were found to be more sensitive to the drugs in the presence of stromal and immune cells. Penetration and cytotoxicity of the drug-loaded nanocomplexes in tumour mimicking tissues were validated using a 3D multicellular-collagen construct in a perfusion bioreactor. The results highlight a simple and potentially scalable strategy for engineering nanocomplexes made entirely of biological macromolecules with potential use for drug delivery.

High CD4-to-CD8 ratio identifies an at-risk population susceptible to lethal COVID-19.

Around half of people with severe COVID-19 requiring intensive care unit (ICU) treatment will survive, but it is unclear how the immune response to SARS-CoV-2 differs between ICU patients that recover and those that do not. We conducted whole-blood immunophenotyping of COVID-19 patients upon admission to ICU and during their treatment and uncovered marked differences in their circulating immune cell subsets. At admission, patients who later succumbed to COVID-19 had significantly lower frequencies of all memory CD8+ T cell subsets, resulting in increased CD4-to-CD8 T cell and neutrophil-to-CD8 T cell ratios. ROC and Kaplan-Meier analyses demonstrated that both CD4-to-CD8 and neutrophil-to-CD8 ratios at admission were strong predictors of in-ICU mortality. Therefore, we propose the use of the CD4-to-CD8 T cell ratio as a marker for the early identification of those individuals likely to require enhanced monitoring and/or pro-active intervention in ICU.

Polymorphonuclear Cells Show Features of Dysfunctional Activation During Fatal Sepsis.

Sepsis and septic shock remain leading causes of morbidity and mortality for patients in the intensive care unit. During the early phase, immune cells produce various cytokines leading to prompt activation of the immune system. Polymorphonuclear leukocytes (PMNs) respond to different signals producing inflammatory factors and executing their antimicrobial mechanisms, resulting in the engulfment and elimination of invading pathogens. However, excessive activation caused by various inflammatory signals produced during sepsis progression can lead to the alteration of PMN signaling and subsequent defects in their functionality. Here, we analyzed samples from 34 patients in septic shock, focusing on PMNs gene expression and proteome changes associated with septic shock. We revealed that, compared to those patients who survived longer than five days, PMNs from patients who had fulminant sepsis were characterized by a dysfunctional hyper-activation, show altered metabolism, and recent exit from the cell cycle and signs of cellular lifespan. We believe that this multi-omics approach, although limited, pinpoints the alterations in PMNs' functionality, which may be rescued by targeted treatments.

Immunosenescence in Childhood Cancer Survivors and in Elderly: A Comparison and Implication for Risk Stratification.

The population of childhood cancer survivors (CCS) has grown rapidly in recent decades. Although cured of their original malignancy, these individuals are at increased risk of serious late effects, including age-associated complications. An impaired immune system has been linked to the emergence of these conditions in the elderly and CCS, likely due to senescent immune cell phenotypes accompanied by low-grade inflammation, which in the elderly is known as "inflammaging." Whether these observations in the elderly and CCS are underpinned by similar mechanisms is unclear. If so, existing knowledge on immunosenescent phenotypes and inflammaging might potentially serve to benefit CCS. We summarize recent findings on the immune changes in CCS and the elderly, and highlight the similarities and identify areas for future research. Improving our understanding of the underlying mechanisms and immunosenescent markers of accelerated immune aging might help us to identify individuals at increased risk of serious health complications.

How immune-cell fate and function are determined by metabolic pathway choice: The bioenergetics underlying the immune response.

Immune cells are highly dynamic in their response to the tissue environment. Most immune cells rapidly change their metabolic profile to obtain sufficient energy to engage in defensive or homeostatic processes. Such "immunometabolism" is governed through intermediate metabolites, and has a vital role in regulating immune-cell function. The underlying metabolic reactions are shaped by the abundance and accessibility of specific nutrients, as well as the overall metabolic status of the host. Here, we discuss how different immune-cell types gain a sufficient energy supply. We then explain how immune cells perform various functions under challenged conditions and expend energy to sustain homeostasis. Finally, we speculate on how the immune-cell metabolic profile might be modulated in health and disease, by manipulating nutrient availability. By such intervention, the recovery of patient with dysregulated immune system responses might be sped up and the fitness of an individual efficiently restored.

Differences in monocyte subsets are associated with short-term survival in patients with septic shock.

Sepsis is characterized by dynamic changes of the immune system resulting in deregulated inflammation and failure of homoeostasis and can escalate to septic shock. Circulating monocytes and other innate immune cells are among the first ones to recognize and clear pathogens. Monocytes have an important role in sepsis and septic shock and have been studied as potential diagnostic markers. In total, forty-two patients with septic shock were recruited and blood samples obtained within first 12 hours of ICU admission. We showed that frequency of classical and intermediate monocytes assessed at the time of admission to the intensive care unit are significantly distinct in patients with septic shock who survived longer that five days from those who died. These parameters correlate significantly with differences in serum levels of inflammatory cytokines MCP-1, IL-6, IL-8, IL-10, and IL-18, and with the proportion of helper and cytotoxic T cells. The described changes in frequency of monocyte subsets and their activation status may predict short-term septic shock survival and help with fast identification of the group of vulnerable patients, who may profit from tailored therapy.

The Effect of Mindfulness-Based Stress Reduction (MBSR) on Depression, Cognition, and Immunity in Mild Cognitive Impairment: A Pilot Feasibility Study.

BACKGROUND: Mindfulness-based programs have shown a promising effect on several health factors associated with increased risk of dementia and the conversion from mild cognitive impairment (MCI) to dementia such as depression, stress, cognitive decline, immune system and brain structural and functional changes. Studies on mindfulness in MCI subjects are sparse and frequently lack control intervention groups. OBJECTIVE: To determine the feasibility and the effect of mindfulness-based stress reduction (MBSR) practice on depression, cognition and immunity in MCI compared to cognitive training. METHODS: Twenty-eight MCI subjects were randomly assigned to two groups. MBSR group underwent 8-week MBSR program. Control group underwent 8-week cognitive training. Their cognitive and immunological profiles and level of depressive symptoms were examined at baseline, after each 8-week intervention (visit 2, V2) and six months after each intervention (visit 3, V3). MBSR participants completed feasibility questionnaire at V2. RESULTS: Twenty MCI patients completed the study (MBSR group n=12, control group n=8). MBSR group showed significant reduction in depressive symptoms at both V2 (p=0.03) and V3 (p=0.0461) compared to the baseline. There was a minimal effect on cognition - a group comparison analysis showed better psychomotor speed in the MBSR group compared to the control group at V2 (p=0.0493) but not at V3. There was a detectable change in immunological profiles in both groups, more pronounced in the MBSR group. Participants checked only positive/neutral answers concerning the attractivity/length of MBSR intervention. More severe cognitive decline (PVLT≤36) was associated with the lower adherence to home practice. CONCLUSION: MBSR is well-accepted potentially promising intervention with positive effect on cognition, depressive symptoms and immunological profile.

Childhood survivors of high-risk neuroblastoma show signs of immune recovery and not immunosenescence.

Neuroblastoma survivors show signs of immunosenescence early after therapy in CD8+ T cell compartment and elevated plasma TNF-α but in later follow-up immune recovery comes into play. Whether the recovery phenotype is long lasting or transient remains to be elucidated, however, late adverse effects often occur in childhood cancer survivors.