Trained Immunity Confers Prolonged Protection From Listeriosis.

Trained immunity refers to the ability of the innate immune system exposed to a first challenge to provide an enhanced response to a secondary homologous or heterologous challenge. We reported that training induced with β-glucan one week before infection confers protection against a broad-spectrum of lethal bacterial infections. Whether this protection persists over time is unknown. To tackle this question, we analyzed the immune status and the response to Listeria monocytogenes (L. monocytogenes) of mice trained 9 weeks before analysis. The induction of trained immunity increased bone marrow myelopoiesis and blood counts of Ly6C <sup>high</sup> inflammatory monocytes and polymorphonuclear neutrophils (PMNs). Ex vivo, whole blood, PMNs and monocytes from trained mice produced increased levels of cytokines in response to microbial products and limited the growth of L. monocytogenes. In vivo, following challenge with L. monocytogenes, peripheral blood leukocytes were massively depleted in control mice but largely preserved in trained mice. PMNs were reduced also in the spleen from control mice, and increased in the spleen of trained mice. In transwell experiments, PMNs from trained mice showed increased spontaneous migration and CXCL2/MIP2α-induced chemotaxis, suggesting that training promotes the migration of PMNs in peripheral organs targeted by L. monocytogenes. Trained PMNs and monocytes had higher glycolytic activity and mitochondrial respiration than control cells when exposed to L. monocytogenes. Bacterial burden and dissemination in blood, spleen and liver as well as systemic cytokines and inflammation (multiplex bead assay and bioluminescence imaging) were reduced in trained mice. In full agreement with these results, mice trained 9 weeks before infection were powerfully protected from lethal listeriosis. Altogether, these data suggest that training increases the generation and the antimicrobial activity of PMNs and monocytes, which may confer prolonged protection from lethal bacterial infection

COVID-19 rapidly increases MDSCs and prolongs innate immune dysfunctions.

We used unsupervised immunophenotyping of blood leukocytes and measured cytokine production by innate immune cell exposed to LPS and R848. We show that COVID-19 induces a rapid, transient upregulation of myeloid-derived suppressor cells (MDSCs) accompanied by a rapid, sustained (up to 3 months) hyporesponsiveness of dendritic cells and monocytes. Blood MDSCs may represent biomarkers and targets for intervention strategies in COVID-19 patients

Engineering cytokine therapeutics

Cytokines have pivotal roles in immunity, making them attractive as therapeutics for a variety of immune-related disorders. However, the widespread clinical use of cytokines has been limited by their short blood half-lives and severe side effects caused by low specificity and unfavourable biodistribution. Innovations in bioengineering have aided in advancing our knowledge of cytokine biology and yielded new technologies for cytokine engineering. In this Review, we discuss how the development of bioanalytical methods, such as sequencing and high-resolution imaging combined with genetic techniques, have facilitated a better understanding of cytokine biology. We then present an overview of therapeutics arising from cytokine re-engineering, targeting and delivery, mRNA therapeutics and cell therapy. We also highlight the application of these strategies to adjust the immunological imbalance in different immune-mediated disorders, including cancer, infection and autoimmune diseases. Finally, we look ahead to the hurdles that must be overcome before cytokine therapeutics can live up to their full potential

Resolving sepsis-induced immunoparalysis via trained immunity by targeting interleukin-4 to myeloid cells.

Immunoparalysis is a compensatory and persistent anti-inflammatory response to trauma, sepsis or another serious insult, which increases the risk of opportunistic infections, morbidity and mortality. Here, we show that in cultured primary human monocytes, interleukin-4 (IL4) inhibits acute inflammation, while simultaneously inducing a long-lasting innate immune memory named trained immunity. To take advantage of this paradoxical IL4 feature in vivo, we developed a fusion protein of apolipoprotein A1 (apoA1) and IL4, which integrates into a lipid nanoparticle. In mice and non-human primates, an intravenously injected apoA1-IL4-embedding nanoparticle targets myeloid-cell-rich haematopoietic organs, in particular, the spleen and bone marrow. We subsequently demonstrate that IL4 nanotherapy resolved immunoparalysis in mice with lipopolysaccharide-induced hyperinflammation, as well as in ex vivo human sepsis models and in experimental endotoxemia. Our findings support the translational development of nanoparticle formulations of apoA1-IL4 for the treatment of patients with sepsis at risk of immunoparalysis-induced complications.We thank M. Jaeger (Radboudumc) for kindly providing flourescein isothiocyanate-labelled Candida albicans. D. Williams (East Tennessee State University) provided the β-glucan we used in our initial experiments. H. Lemmers (Radboudumc) kindly prepared the purified lipopolysaccharide used for stimulation of primary human monocytes and macrophages. Part of the figures were prepared using (among other software) Biorender.com. B.N. is supported by a National Health and Medical Research Council (Australia) Investigator Grant (APP1173314). This work was supported by National Institutes of Health grants R01 HL144072, R01 CA220234 and P01 HL131478, as well as a Vici grant from the Dutch Research Council NWO and an ERC Advanced Grant (all to W.J.M.M.). M.G.N. was supported by a Spinoza grant from Dutch Research Council NWO and an ERC Advanced Grant (#833247).S

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

Parity polytopes and binarization

We consider generalizations of parity polytopes whose variables, in addition to a parity constraint, satisfy certain ordering constraints. More precisely, the variable domain is partitioned into k contiguous groups, and within each group, we require xi≥xi+1 for all relevant i. Such constraints are used to break symmetry after replacing an integer variable by a sum of binary variables, so-called binarization. We provide extended formulations for such polytopes, derive a complete outer description, and present a separation algorithm for the new constraints. It turns out that applying binarization and only enforcing parity constraints on the new variables is often a bad idea. For our application, an integer programming model for the graphic traveling salesman problem, we observe that parity constraints do not improve the dual bounds, and we provide a theoretical explanation of this effect

Identification of novel small molecule inhibitors of activated protein C

Introduction: Activated protein C (APC) is the central enzyme of the anticoagulant protein C pathway. Low concentrations of APC circulate in plasma and are believed to contribute to the maintenance of a normal haemostatic balance. Materials and Methods: We have used a structure-based virtual screening approach to discover small drug-like molecules that inhibit the interaction between APC and its substrate FVa through inhibition of a predominant APC exosite, known to be involved in FVa substrate binding. We have combined in silico selection with functional screening and direct binding analysis to identify novel molecules and to ascertain and characterize the inhibition of the interaction between APC and FVa. Results: We have identified a number of novel molecules that bind to APC and protein C with Kd values in the range of 10(-3)-10(-5) M. Inhibition by these molecules is incomplete, which most likely reflects the extended surface that is involved in the interaction between APC and its substrates. Direct binding of hit molecules to variant APC molecules that were mutated in the targeted binding site revealed that several of the molecules presented a 100-500 fold lower affinity for the variant molecule, suggesting that these molecules indeed bind the exosite of APC. Conclusions: The protein-protein interaction inhibitors discovered here, could function as starting molecules for further development of small molecules with anti-APC properties. Such molecules may be of clinical interest, in particular in individuals where thrombin formation is compromised and the haemostatic balance is tipped towards bleeding tendencies, such as in haemophilia A