Characterisation of two key virulence factors in Escherichia coli O157:H7

Enterohaemorrhagic Escherichia coli (EHEC) are a subset of pathogenic E. coli which can cause diarrhoeal disease, with the majority of infections due to serovar O157:H7. Successful infection by EHEC is determined by the expression of two key virulence factors, flagella and the type three secretion system (T3SS), a bacterially encoded needle-like filament. Flagella are responsible for directional and targeted swimming of the bacteria as well as for initiating bacteria: host cell attachment. A subsequent switch to T3SS expression promotes enhanced binding via the transmission of bacterial proteins (termed effectors) into the host cell. Once in the host cell these effectors act to manipulate host cell pathways and further facilitate infection. This thesis sets out to explore these two important virulence factors; firstly by exploring the regulation of flagella rotation, and thus motility, in a series of Acetaldehyde coA dehydrogenase (AdhE) deletion mutants; and secondly by assessing the potential of a novel fluorescent reporter molecule, LOV, in imaging the expression, translocation and host cell localisation of T3SS injected effector proteins. Findings from this study show that the LOV domain can be used to fluorescently tag the bacterial effector, Tir, and monitor it’s expression, translocation through the T3SS and localisation within the host cell, in real-time. This opens up exciting new possibilities in using LOV to fluorescently monitor the localisation of bacterial effector proteins within the host cell and thus give information on potential cellular partners and mechanism of action. Additionally, exploration of flagella rotation regulation, through the isolation and genomic sequencing of a set of AdhE deletion mutants, suggested a role for AdhE in bacterial motility via indirect acetylation of the chemotaxis protein CheY. A better understanding of both of these virulence factors will render us more capable in our ability to carry out treatment and prevention of EHEC mediated disease

A Perfusion Bioreactor for Longitudinal Monitoring of Bioengineered Liver Constructs

In the field of in vitro liver disease models, decellularised organ scaffolds maintain the original biomechanical and biological properties of the extracellular matrix and are established supports for in vitro cell culture. However, tissue engineering approaches based on whole organ decellularized scaffolds are hampered by the scarcity of appropriate bioreactors that provide controlled 3D culture conditions. Novel specific bioreactors are needed to support long-term culture of bioengineered constructs allowing non-invasive longitudinal monitoring. Here, we designed and validated a specific bioreactor for long-term 3D culture of whole liver constructs. Whole liver scaffolds were generated by perfusion decellularisation of rat livers. Scaffolds were seeded with Luc(+)HepG2 and primary human hepatocytes and cultured in static or dynamic conditions using the custom-made bioreactor. The bioreactor included a syringe pump, for continuous unidirectional flow, and a circuit built to allow non-invasive monitoring of culture parameters and media sampling. The bioreactor allowed non-invasive analysis of cell viability, distribution, and function of Luc(+)HepG2-bioengineered livers cultured for up to 11 days. Constructs cultured in dynamic conditions in the bioreactor showed significantly higher cell viability, measured with bioluminescence, distribution, and functionality (determined by albumin production and expression of CYP enzymes) in comparison to static culture conditions. Finally, our bioreactor supports primary human hepatocyte viability and function for up to 30 days, when seeded in the whole liver scaffolds. Overall, our novel bioreactor is capable of supporting cell survival and metabolism and is suitable for liver tissue engineering for the development of 3D liver disease models

Genetic deficiency of indoleamine 2,3-dioxygenase promotes gut microbiota-mediated metabolic health.

The association between altered gut microbiota, intestinal permeability, inflammation and cardiometabolic diseases is becoming increasingly clear but remains poorly understood1,2. Indoleamine 2,3-dioxygenase is an enzyme induced in many types of immune cells, including macrophages in response to inflammatory stimuli, and catalyzes the degradation of tryptophan along the kynurenine pathway. Indoleamine 2,3-dioxygenase activity is better known for its suppression of effector T cell immunity and its activation of regulatory T cells3,4. However, high indoleamine 2,3-dioxygenase activity predicts worse cardiovascular outcome5-9 and may promote atherosclerosis and vascular inflammation6, suggesting a more complex role in chronic inflammatory settings. Indoleamine 2,3-dioxygenase activity is also increased in obesity10-13, yet its role in metabolic disease is still unexplored. Here, we show that obesity is associated with an increase of intestinal indoleamine 2,3-dioxygenase activity, which shifts tryptophan metabolism from indole derivative and interleukin-22 production toward kynurenine production. Indoleamine 2,3-dioxygenase deletion or inhibition improves insulin sensitivity, preserves the gut mucosal barrier, decreases endotoxemia and chronic inflammation, and regulates lipid metabolism in liver and adipose tissues. These beneficial effects are due to rewiring of tryptophan metabolism toward a microbiota-dependent production of interleukin-22 and are abrogated after treatment with a neutralizing anti-interleukin-22 antibody. In summary, we identify an unexpected function of indoleamine 2,3-dioxygenase in the fine tuning of intestinal tryptophan metabolism with major consequences on microbiota-dependent control of metabolic disease, which suggests indoleamine 2,3-dioxygenase as a potential therapeutic target

Visualizing the Translocation and Localization of Bacterial Type III Effector Proteins by Using a Genetically Encoded Reporter System

Bacterial Type Three Secretion System (T3SS) effector proteins are critical determinants of infection for many animal and plant pathogens. However, monitoring of the translocation and delivery of these important virulence determinants has proved to be technically challenging. Here, we used a genetically engineered LOV (light-oxygen-voltage) sensing domain derivative to monitor the expression, translocation and localization of bacterial T3SS effectors. We found the Escherichia coli O157:H7 bacterial effector fusion Tir-LOV was functional following its translocation and localized to the host cell membrane in discrete foci demonstrating that LOV-based reporters can be used to visualize the effector translocation with minimal manipulation and interference. Further evidence for the versatility of the reporter was demonstrated by fusing LOV to the C-terminus of the Shigella flexneri effector IpaB. IpaB-LOV localized preferentially at bacterial poles before translocation. We observed the rapid translocation of IpaB-LOV in a T3SS-dependent manner into host cells, where it localized at the bacterial entry site within membrane ruffles

The use of erythropoiesis-stimulating agents with ruxolitinib in patients with myelofibrosis in COMFORT-II: an open-label, phase 3 study assessing efficacy and safety of ruxolitinib versus best available therapy in the treatment of myelofibrosis

BACKGROUND: Anemia is considered a negative prognostic risk factor for survival in patients with myelofibrosis. Most patients with myelofibrosis are anemic, and 35–54 % present with anemia at diagnosis. Ruxolitinib, a potent inhibitor of Janus kinase (JAK) 1 and JAK2, was associated with an overall survival benefit and improvements in splenomegaly and patient-reported outcomes in patients with myelofibrosis in the two phase 3 COMFORT studies. Consistent with the ruxolitinib mechanism of action, anemia was a frequently reported adverse event. In clinical practice, anemia is sometimes managed with erythropoiesis-stimulating agents (ESAs). This post hoc analysis evaluated the safety and efficacy of concomitant ruxolitinib and ESA administration in patients enrolled in COMFORT-II, an open-label, phase 3 study comparing the efficacy and safety of ruxolitinib with best available therapy for treatment of myelofibrosis. Patients were randomized (2:1) to receive ruxolitinib 15 or 20 mg twice daily or best available therapy. Spleen volume was assessed by magnetic resonance imaging or computed tomography scan. RESULTS: Thirteen of 146 ruxolitinib-treated patients had concomitant ESA administration (+ESA). The median exposure to ruxolitinib was 114 weeks in the +ESA group and 111 weeks in the overall ruxolitinib arm; the median ruxolitinib dose intensity was 33 mg/day for each group. Six weeks before the first ESA administration, 10 of the 13 patients had grade 3/4 hemoglobin abnormalities. These had improved to grade 2 in 7 of the 13 patients by 6 weeks after the first ESA administration. The rate of packed red blood cell transfusions per month within 12 weeks before and after first ESA administration remained the same in 1 patient, decreased in 2 patients, and increased in 3 patients; 7 patients remained transfusion independent. Reductions in splenomegaly were observed in 69 % of evaluable patients (9/13) following first ESA administration. CONCLUSIONS: Concomitant use of an ESA with ruxolitinib was well tolerated and did not affect the efficacy of ruxolitinib. Further investigations evaluating the effects of ESAs to alleviate anemia in ruxolitinib-treated patients are warranted (ClinicalTrials.gov identifier, NCT00934544; July 6, 2009)

Specificities of the intestinal microbiota in patients with inflammatory bowel disease and Clostridium difficile infection

International audienceBackground and Aims: Clostridium difficile infection (CDI) is a common complication in inflammatory bowel disease (IBD) and has been associated with poor IBD outcome. Intestinal microbiota composition in IBD patients with CDI has not been specifically evaluated to date.Methods: The fecal microbiota of 56 IBD patients, including 8 in flare with concomitant CDI, 24 in flare without CDI, and 24 in remission, as well as 24 healthy subjects, was studied using 16S sequencing. Analysis was performed using the Qiime pipeline.Results: Compared to IBD patients without CDI, IBD patients with CDI had more pronounced dysbiosis with higher levels of Ruminococcus gnavus and Enterococcus operational taxonomic units (OTUs) and lower levels of Blautia and Dorea OTUs. Correlation network analysis suggested a disrupted ecosystem in IBD patients in flare, particularly in those with CDI.Conclusions: In patients with IBD, CDI is associated with a more pronounced intestinal dysbiosis with specific alterations in intestinal microorganisms

JAK inhibition with ruxolitinib versus best available therapy for myelofibrosis

BACKGROUND: Treatment options for myelofibrosis are limited. We evaluated the efficacy and safety of ruxolitinib, a potent and selective Janus kinase (JAK) 1 and 2 inhibitor, as compared with the best available therapy, in patients with myelofibrosis. METHODS: We assigned 219 patients with intermediate-2 or high-risk primary myelofibrosis, post-polycythemia vera myelofibrosis, or post-essential thrombocythemia myelofibrosis to receive oral ruxolitinib or the best available therapy. The primary end point and key secondary end point of the study were the percentage of patients with at least a 35% reduction in spleen volume at week 48 and at week 24, respectively, as assessed with the use of magnetic resonance imaging or computed tomography. RESULTS: A total of 28% of the patients in the ruxolitinib group had at least a 35% reduction in spleen volume at week 48, as compared with 0% in the group receiving the best available therapy (P<0.001); the corresponding percentages at week 24 were 32% and 0% (P<0.001). At 48 weeks, the mean palpable spleen length had decreased by 56% with ruxolitinib but had increased by 4% with the best available therapy. The median duration of response with ruxolitinib was not reached, with 80% of patients still having a response at a median follow-up of 12 months. Patients in the ruxolitinib group had an improvement in overall quality-of-life measures and a reduction in symptoms associated with myelofibrosis. The most common hematologic abnormalities of grade 3 or higher in either group were thrombocytopenia and anemia, which were managed with a dose reduction, interruption of treatment, or transfusion. One patient in each group discontinued treatment owing to thrombocytopenia, and none discontinued owing to anemia. Nonhematologic adverse events were rare and mostly grade 1 or 2. Two cases of acute myeloid leukemia were reported with the best available therapy. CONCLUSIONS: Continuous ruxolitinib therapy, as compared with the best available therapy, was associated with marked and durable reductions in splenomegaly and disease-related symptoms, improvements in role functioning and quality of life, and modest toxic effects. An influence on overall survival has not yet been shown. (Funded by Novartis Pharmaceuticals; ClinicalTrials.gov number, NCT00934544.)

Three-year efficacy, safety, and survival findings from COMFORT-II, a phase 3 study comparing ruxolitinib with best available therapy for myelofibrosis.

Ruxolitinib is a potent Janus kinase (JAK)1/JAK2 inhibitor that has demonstrated rapid reductions in splenomegaly and marked improvement in disease-related symptoms and quality of life in patients with myelofibrosis (MF). The present analysis reports the 3-year follow-up (median, 151 weeks) of the efficacy and safety of Controlled Myelofibrosis Study With Oral Janus-associated Kinase (JAK) Inhibitor Treatment-II (the COMFORT-II Trial), comparing ruxolitinib with the best available therapy (BAT) in 219 patients with intermediate-2 and high-risk MF. In the ruxolitinib arm, with continued therapy, spleen volume reductions of ≥35% by magnetic resonance imaging (equivalent to approximately 50% reduction by palpation) were sustained for at least 144 weeks, with the probability of 50% (95% confidence interval [CI], 36-63) among patients achieving such degree of response. At the time of this analysis, 45% of the patients randomized to ruxolitinib remained on treatment. Ruxolitinib continues to be well tolerated. Anemia and thrombocytopenia were the main toxicities, but they were generally manageable, improved over time, and rarely led to treatment discontinuation (1% and 3.6% of patients, respectively). No single nonhematologic adverse event led to definitive ruxolitinib discontinuation in more than 1 patient. Additionally, patients randomized to ruxolitinib showed longer overall survival than those randomized to BAT (hazard ratio, 0.48; 95% CI, 0.28-0.85; log-rank test, P = .009)

Comparison of placebo and best available therapy for the treatment of myelofibrosis in the phase 3 COMFORT studies

Prior to Janus kinase inhibitors, available therapies for myelofibrosis were generally supportive and did not improve survival. This analysis compares efficacy outcomes of patients with myelofibrosis in the control arms (placebo [n=154] and best available therapy [n=73]) from the two phase 3 COntrolled MyeloFibrosis study with ORal JAK inhibitor Treatment (COMFORT) studies. Spleen volume was assessed by magnetic resonance imaging/computed tomography at baseline and every 12 weeks through week 72; spleen length was assessed by palpation at each study visit. Health-related quality of life and symptoms were assessed using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 Items at baseline and in weeks 4, 8, 12, 16 and 24 in COMFORT-I and in weeks 8, 16, 24 and 48 in COMFORT-II. The demographic and baseline characteristics were similar between the control arms of the two studies. One patient who received placebo and no patients who received best available therapy had a ≥35% reduction in spleen volume from baseline at week 24. At 24 weeks, neither placebo nor best available therapy had produced clinically meaningful changes in global quality of life or symptom scales. Non-hematologic adverse events were mostly grade 1/2; the most frequently reported adverse events in each group were abdominal pain, fatigue, peripheral edema and diarrhea. These data suggest that non-Janus kinase inhibitor therapies provide little improvement in splenomegaly, symptoms or quality of life as compared with placebo. Both COMFORT-I (NCT00952289) and COMFORT-II (NCT00934544) studies have been appropriately registered with clinicaltrials.gov