ß-glucans from Agaricus bisporus mushroom products drive Trained Immunity.

Introduction: Macrofungi, such as edible mushrooms, have been used as a valuable medical resource for millennia as a result of their antibacterial and immuno-modulatory components. Mushrooms contain dietary fibers known as ß-glucans, a class of polysaccharides previously linked to the induction of Trained Immunity. However, little is known about the ability of mushroom-derived ß-glucans to induce Trained Immunity. Methods & results: Using various powdered forms of the white button mushroom (Agaricus bisporus), we found that mouse macrophages pre-treated with whole mushroom powder (WMP) displayed enhanced responses to restimulation with TLR ligands, being particularly sensitive to Toll-like receptor (TLR)-2 stimulation using synthetic lipopeptides. This trained response was modest compared to training observed with yeast-derived ß-glucans and correlated with the amount of available ß-glucans in the WMP. Enriching for ß-glucans content using either a simulated in-vitro digestion or chemical fractionation retained and boosted the trained response with WMP, respectively. Importantly, both WMP and digested-WMP preparations retained ß-glucans as identified by nuclear magnetic resonance analysis and both displayed the capacity to train human monocytes and enhanced responses to restimulation. To determine if dietary incorporation of mushroom products can lead to Trained Immunity in myeloid cells in vivo, mice were given a regimen of WMP by oral gavage prior to sacrifice. Flow cytometric analysis of bone-marrow progenitors indicated alterations in hematopoietic stem and progenitor cells population dynamics, with shift toward myeloid-committed multi-potent progenitor cells. Mature bone marrow-derived macrophages derived from these mice displayed enhanced responses to restimulation, again particularly sensitive to TLR2. Discussion: Taken together, these data demonstrate that ß-glucans from common macrofungi can train innate immune cells and could point to novel ways of delivering bio-available ß-glucans for education of the innate immune system.

von Willebrand factor links primary hemostasis to innate immunity.

The plasma multimeric glycoprotein von Willebrand factor (VWF) plays a critical role in primary hemostasis by tethering platelets to exposed collagen at sites of vascular injury. Recent studies have identified additional biological roles for VWF, and in particular suggest that VWF may play an important role in regulating inflammatory responses. However, the molecular mechanisms through which VWF exerts its immuno-modulatory effects remain poorly understood. In this study, we report that VWF binding to macrophages triggers downstream MAP kinase signaling, NF-κB activation and production of pro-inflammatory cytokines and chemokines. In addition, VWF binding also drives macrophage M1 polarization and shifts macrophage metabolism towards glycolysis in a p38-dependent manner. Cumulatively, our findings define an important biological role for VWF in modulating macrophage function, and thereby establish a novel link between primary hemostasis and innate immunity.

Mycobacterium tuberculosis Limits Host Glycolysis and IL-1ß by Restriction of PFK-M via MicroRNA-21.

Increased glycolytic metabolism recently emerged as an essential process driving host defense against Mycobacterium tuberculosis (Mtb), but little is known about how this process is regulated during infection. Here, we observe repression of host glycolysis in Mtb-infected macrophages, which is dependent on sustained upregulation of anti-inflammatory microRNA-21 (miR-21) by proliferating mycobacteria. The dampening of glycolysis by miR-21 is mediated through targeting of phosphofructokinase muscle (PFK-M) isoform at the committed step of glycolysis, which facilitates bacterial growth by limiting pro-inflammatory mediators, chiefly interleukin-1ß (IL-1ß). Unlike other glycolytic genes, PFK-M expression and activity is repressed during Mtb infection through miR-21-mediated regulation, while other less-active isoenzymes dominate. Notably, interferon-γ (IFN-γ), which drives Mtb host defense, inhibits miR-21 expression, forcing an isoenzyme switch in the PFK complex, augmenting PFK-M expression and macrophage glycolysis. These findings place the targeting of PFK-M by miR-21 as a key node controlling macrophage immunometabolic function.

Biomarkers Predict Relapse in Granulomatosis with Polyangiitis.

Granulomatosis with polyangiitis (GPA) is a small blood vessel vasculitic disorder with a high mortality rate if undiagnosed or treated inadequately. Disease relapse is a key feature of this disease and early identification of relapse episodes is very important in limiting end-organ damage. The advent of indirect immunofluorescence to detect antineutrophil cytoplasmic antibody (ANCA) with specific reactivity against the enzyme proteinase-3 (PR3) has been very useful in the diagnosis of GPA but is less helpful in predicting relapse. Indeed, up to date no satisfactory biomarker has been identified that can reliably predict relapse. This study assessed the probability of the occurrence of a relapse when a change was noted in a range of commonly used laboratory tests. These tests included levels of C-reactive protein (CRP), anti-PR3 antibodies, ANCA titre, and the neutrophil count. A group of 30 GPA patients with a total of 66 relapse episodes was investigated and a novel clinical yield score was devised. When a combined rise in CRP, anti-PR3 antibodies, and neutrophil count was observed in the 6-month period before a relapse event, 59% of patient relapses could be predicted. Monitoring changes in this set of parameters helps identify disease relapse.