Experimental Meningococcal Sepsis in Congenic Transgenic Mice Expressing Human Transferrin

Severe meningococcal sepsis is still of high morbidity and mortality. Its management may be improved by an experimental model allowing better understanding of its pathophysiology. We developed an animal model of meningococcal sepsis in transgenic BALB/c mice expressing human transferrin. We studied experimental meningococcal sepsis in congenic transgenic BALB/c mice expressing human transferrin by transcriptional profiling using microarray analysis of blood and brain samples. Genes encoding acute phase proteins, chemokines and cytokines constituted the largest strongly regulated groups. Dynamic bioluminescence imaging further showed high blood bacterial loads that were further enhanced after a primary viral infection by influenza A virus. Moreover, IL-1 receptor–associated kinase–3 (IRAK-3) was induced in infected mice. IRAK-3 is a negative regulator of Toll-dependant signaling and its induction may impair innate immunity and hence result in an immunocompromised state allowing bacterial survival and systemic spread during sepsis. This new approach should enable detailed analysis of the pathophysiology of meningococcal sepsis and its relationships with flu infection

Translocated LPS Might Cause Endotoxin Tolerance in Circulating Monocytes of Cystic Fibrosis Patients

Cystic Fibrosis (CF) is an inherited pleiotropic disease that results from abnormalities in the gene codes of a chloride channel. The lungs of CF patients are chronically infected by several pathogens but bacteraemia have rarely been reported in this pathology. Besides that, circulating monocytes in CF patients exhibit a patent Endotoxin Tolerance (ET) state since they show a significant reduction of the inflammatory response to bacterial stimulus. Despite a previous description of this phenomenon, the direct cause of ET in CF patients remains unknown. In this study we have researched the possible role of microbial/endotoxin translocation from a localized infection to the bloodstream as a potential cause of ET induction in CF patients. Plasma analysis of fourteen CF patients revealed high levels of LPS compared to healthy volunteers and patients who suffer from Chronic Obstructive Pulmonary Disease. Experiments in vitro showed that endotoxin concentrations found in plasma of CF patients were enough to induce an ET phenotype in monocytes from healthy controls. In agreement with clinical data, we failed to detect bacterial DNA in CF plasma. Our results suggest that soluble endotoxin present in bloodstream of CF patients causes endotoxin tolerance in their circulating monocytes

Evaluation of appendicitis risk prediction models in adults with suspected appendicitis

Background Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis. Methods A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis). Results Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent). Conclusion Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified

Metabolic reprogramming of host cells upon bacterial infection: Why shift to a Warburg‐like metabolism?

This article also appears in: State-of-the-Art ReviewsInternational audienceThe finding that the Warburg effect observed in proliferating cancer cells is also observed during immune responses renewed the interest in the study of metabolic reprogramming of immune cells, a field of investigation called immunometabolism. However, the specific mechanisms and processes underlying metabolic changes of host cells upon bacterial infection remain poorly understood. Several recent reports have reported that mammalian cells infected with intracellular bacteria have an altered metabolism that resembles the Warburg effect seen in cancer cells. In this Review, we will summarize current knowledge on metabolic reprogramming and discuss putative causes underlying the preferential remodelling of host cells to Warburg-like metabolic programs during infection by intracellular bacteria

Mitochondrial Dynamics and Activity in Legionella-Infected Cells

International audienceThe study of Legionella pneumophila interactions with host mitochondria during infection has been historically limited by the techniques available to analyze and quantify mitochondrial dynamics and activity in living cells. Recently, new, powerful techniques such as high-content microscopy or mitochondrial respiration assays (Seahorse) have been developed to quantitatively analyze mitochondrial parameters. Here we present state-of-the-art methods adapted to analyze mitochondrial dynamics and activity during Legionella infection of living human primary macrophages

Neuronal injury external to the retina rapidly activates retinal glia, followed by elevation of markers for cell cycle re-entry and death in retinal ganglion cells

Retinal ganglion cells (RGCs) are neurons that relay visual signals from the retina to the brain. The RGC cell bodies reside in the retina and their fibers form the optic nerve. Full transection (axotomy) of the optic nerve is an extra-retinal injury model of RGC degeneration. Optic nerve transection permits time-kinetic studies of neurodegenerative mechanisms in neurons and resident glia of the retina, the early events of which are reported here. One day after injury, and before atrophy of RGC cell bodies was apparent, glia had increased levels of phospho-Akt, phospho-S6, and phospho-ERK1/2; however, these signals were not detected in injured RGCs. Three days after injury there were increased levels of phospho-Rb and cyclin A proteins detected in RGCs, whereas these signals were not detected in glia. DNA hyperploidy was also detected in RGCs, indicative of cell cycle re-entry by these post-mitotic neurons. These events culminated in RGC death, which is delayed by pharmacological inhibition of the MAPK/ERK pathway. Our data show that a remote injury to RGC axons rapidly conveys a signal that activates retinal glia, followed by RGC cell cycle re-entry, DNA hyperploidy, and neuronal death that is delayed by preventing glial MAPK/ERK activation. These results demonstrate that complex and variable neuro-glia interactions regulate healthy and injured states in the adult mammalian retina. © 2014 Galan et al.Peer Reviewe

Sorting of Phagocytic Cells Infected with Legionella pneumophila

International audienceThe ability of Legionella pneumophila to colonize host cells and to form a replicative vacuole depends on its ability to counteract the host cell response by secreting more than 300 effectors. The host cell responds to this bacterial invasion with extensive intracellular signaling to counteract the replication of the pathogen. When studying L. pneumophila infection in vitro, only a small proportion of the cell lines or primary cells used to analyze the host response are infected; the study of such a mixed cell population leads to unprecise results. In order to study the multitude of pathogen-induced phenotypic changes occurring in the host cell, the separation of infected from uninfected cells is a top priority. Here we describe a highly efficient FACS-derived protocol to separate cells infected with a L. pneumophila strain encoding a fluorescent protein. Indeed, the highly infected, homogenous cell population obtained after sorting is the best possible starting point for the studies of infection-induced effects