Regulation of host weight gain and lipid metabolism by bacterial bile acid modification in the gut

Alterations in the gastrointestinal microbiota have been implicated in obesity in mice and humans, but the key microbial functions influencing host energy metabolism and adiposity remain to be determined. Despite an increased understanding of the genetic content of the gastrointestinal microbiome, functional analyses of common microbial gene sets are required. We established a controlled expression system for the parallel functional analysis of microbial alleles in the murine gut. Using this approach we show that bacterial bile salt hydrolase (BSH) mediates a microbe-host dialogue that functionally regulates host lipid metabolism and plays a profound role in cholesterol metabolism and weight gain in the host. Expression of cloned BSH enzymes in the gastrointestinal tract of gnotobiotic or conventionally raised mice significantly altered plasma bile acid signatures and regulated transcription of key genes involved in lipid metabolism (Pparγ, Angptl4), cholesterol metabolism (Abcg5/8), gastrointestinal homeostasis (RegIIIγ), and circadian rhythm (Dbp, Per1/2) in the liver or small intestine. High-level expression of BSH in conventionally raised mice resulted in a significant reduction in host weight gain, plasma cholesterol, and liver triglycerides, demonstrating the overall impact of elevated BSH activity on host physiology. In addition, BSH activity in vivo varied according to BSH allele group, indicating that subtle differences in activity can have significant effects on the host. In summary, we demonstrate that bacterial BSH activity significantly impacts the systemic metabolic processes and adiposity in the host and represents a key mechanistic target for the control of obesity and hypercholesterolemia.

Relationship of vaccine efficacy to the kinetics of DC and T-cell responses induced by PLG-based cancer vaccines

Cancer vaccines are typically formulated for bolus injection and often produce short-lived immunostimulation resulting in poor temporal control over immune cell activation and weak oncolytic activity. One means of overcoming these limitations utilizes immunologically active biomaterial constructs. We previously reported that antigen-laden, macroporous PLG scaffolds induce potent dendritic cell (DC) and cytotoxic T-lymphocyte (CTL) responses via the controlled signaling of inflammatory cytokines, antigen and toll-like receptor agonists. In this study, we describe the kinetics of these responses and illustrate their fundamental relationship to potent tumor rejection when implanted subcutaneously in a mouse B16 model of melanoma. By explanting scaffolds from mice at times ranging from 1–7 d, a seamless relationship was observed between the production of controlled CTL responses, tumor growth and long-term survival in both prophylactic and therapeutic models. Scaffolds must be implanted for > 7 d to augment CTL responses via the prolonged presentation of tumor antigen, and the benefits included a notable regression of established tumors. Host DC infiltration into the porous material persisted for 12 days (peaking at day 5 ~1.4 x 10⁶ cells), and a sharp attenuation in DC numbers coincided with peak CD8⁺ CTL infiltration at day 12 (~8 x 10⁵ cells). Importantly, these PLG systems enhanced DC numbers in the draining lymph node, resulting in increased CD8(+) CTL subsets at days 10–16 of vaccination. These results indicate that material systems can finely control innate and adaptive immune cell responses to kill typically untreatable melanoma tumors and provide critical kinetic data for the design of vaccine carriers.

Is the interleukin 8 promoter polymorphism rs4073/-251T >A associated with Clostridium difficile infection?

The interleukin 8 gene single-nucleotide polymorphism rs4073/-251T >A predisposes to Clostridium difficile infection (CDI), but this association has not been independently validated. In this study, we were unable to replicate this association in either a white cohort or by meta-analysis, suggesting that rs4073/-251T >A is unlikely to constitute a major risk factor for CDI.

Monocyte/macrophage inflammatory response pathways to combat Francisella infection: possible therapeutic targets?

Francisella tularensis can bypass and suppress host immune responses, even to the point of manipulating immune cell phenotypes and intercellular inflammatory networks. Strengthening these responses such that immune cells more readily identify and destroy the bacteria is likely to become a viable (and perhaps necessary) strategy for combating infections with Francisella, especially given the likelihood of antibiotic resistance in the foreseeable future. Monocytes and macrophages offer a niche wherein Francisella can invade and replicate, resulting in substantially higher bacterial load that can overcome the host. As such, understanding their responses to Francisella may uncover potential avenues of therapy that could promote a lowering of bacterial burden and clearance of infection. These response pathways include Toll-like Receptor 2 (TLR2), the caspase-1 inflammasome, Interferons, NADPH oxidase, Phosphatidylinositide 3-kinase (PI3K), and the Ras pathway. In this review we summarize the literature pertaining to the roles of these pathways during Francisella infection, with an emphasis on monocyte/macrophage responses. The therapeutic targeting of one or more such pathways may ultimately become a valuable tool for the treatment of tularemia, and several possibilities are discussed.

Staphylococcus aureus Colonization: Modulation of Host Immune Response and Impact on Human Vaccine Design

In apparent contrast to its invasive potential Staphylococcus aureus colonizes the anterior nares of 20–80% of the human population. The relationship between host and microbe appears particularly individualized and colonization status seems somehow predetermined. After decolonization, persistent carriers often become re-colonized with their prior S. aureus strain, whereas non-carriers resist experimental colonization. Efforts to identify factors facilitating colonization have thus far largely focused on the microorganism rather than on the human host. The host responds to S. aureus nasal colonization via local expression of anti-microbial peptides, lipids, and cytokines. Interplay with the co-existing microbiota also influences colonization and immune regulation. Transient or persistent S. aureus colonization induces specific systemic immune responses. Humoral responses are the most studied of these and little is known of cellular responses induced by colonization. Intriguingly, colonized patients who develop bacteremia may have a lower S. aureus-attributable mortality than their non-colonized counterparts. This could imply a staphylococcal-specific immune “priming” or immunomodulation occurring as a consequence of colonization and impacting on the outcome of infection. This has yet to be fully explored. An effective vaccine remains elusive. Anti-S. aureus vaccine strategies may need to drive both humoral and cellular immune responses to confer efficient protection. Understanding the influence of colonization on adaptive response is essential to intelligent vaccine design, and may determine the efficacy of vaccine-mediated immunity. Clinical trials should consider colonization status and the resulting impact of this on individual patient responses. We urgently need an increased appreciation of colonization and its modulation of host immunity.

Host response, malnutrition and oral diseases. Part 1

Effective defense response of the body requires the proper nutritional and metabolic preparation and adequate energy expenditure. Every pathological process with coexisting malnutrition is subject to an increased risk of failure and complications in medical treatment, which is a serious threat to human health and life. Malnutrition, particularly protein-calorie malnutrition, is characterized by a decrease in resistance, particularly involving cellular immune deficiency, which in turn causes a significant decrease in resistance to infections. Inflammation is the price that the organism has to pay for the effective antimicrobial defense. Therefore, uncontrolled changes may occur in the immune system in nutrition disorders, especially in a significant protein-calorie malnutrition, which in turn prevents the correct response to microbial infection, including bacterial infection, which occurs in the course of periodontitis or untreated caries disease. Research determining the relationship between the clinical state of oral health, selected immune parameters and indicators of nutritional status of the organism, is an alternative to other attempts undertaken to reduce these risks.

Host response, malnutrition and oral diseases. Part 2

Acute phase proteins enhance antioxidant defenses; they are involved in the activation of complement components, opsonization and increase in platelet aggregation as well as inhibition of the respiratory burst in the course of inflammation. Malnutrition plays an important role in the course of response of acute phase proteins. The role of nutrients as antioxidants or as key components of antioxidant enzymes is commonly known. In the course of various inflammatory states, including oral diseases, disorders are observed in caloric requirements of the organism and the requirements for specific amino acids. Numerous experimental studies in animals have also confirmed the relationship between protein- calorie malnutrition and hypofunction of the salivary glands. Studies in children with malnutrition syndrome showed a significantly lower volume of saliva compared to properly nourished children. Depleted nutritional reserves due to long-term chronic malnutrition cause a significant reduction in resistance, progressive damage to the oral mucosa, and reduce resistance to colonization and invasion of pathogenic microorganisms.

Dengue pathogenesis: a disease driven by the host response

Dengue viruses cause mild disease in the majority of infected individuals. In most cases, the disease is characterised by fever, headache, pain behind the eyes, muscle ache, joint pains, vomiting and diarrhoea. In a low percentage of patients, bleeding and loss of plasma (haemorrhage and plasma leakage) may occur. The hyper-permeability syndrome results in plasma leakage and, if the compensatory mechanisms of the body fail to control the plasma leakage or if medical intervention is late, shock may set in. Profound shock will subsequently lead to acidic blood (metabolic acidosis) and development of disseminated intravascular coagulation (DIC). During DIC multiple micro thromboses occur, leading to organ failure. The mechanisms governing pathogenesis of these forms of severe disease are not clear. High amounts of virus in the blood are believed to cause vascular fragility which, together with infection of endothelial cells and high levels of cytokines and other soluble mediators, may result in bleeding. In the absence of a correlation between the amount of virus in the blood and disease severity, it is likely that response to infection is an important cause of disease. The aberrant immune response to infection is believed to result in a cytokine storm, defined as an imbalance between cytokines driving an inflammation (pro-inflammatory) and those silencing an inflammation (anti-inflammatory). Several lines of evidence indicate that displacement of viral genotype and host genetic background are key factors driving the production of a cytokine storm. Several cytokines are known to induce apoptosis, a form of cell suicide (cause of haemorrhage), and/or affect adherens junctions (cause permeability) in vitro. Whether these cytokines may have such effects in vivo remains to be established.

Evaluation of six synthetic surgical meshes implanted subcutaneously in a rat model

The long-term efficacy and mechanical integrity of implanted materials is largely determined by early host response. Therefore, implanting materials with well-characterized tissue responses provides the greatest chance of 'one-hit' surgical successes, without repeated interventions to replace, repair or remove non-compliant biomaterials. Six synthetic meshes were implanted subcutaneously in a rat model to deduce and quantify modulations in host response, based on material fabrication variables. The materials consisted of knitting variations of polypropylene (PP), polyethyleneterephthalate (PET) and polyglycolic acid (PGA) yarns and were implanted for 2, 5, 7, 14 and 28 days before fixation and both semi- and fully quantitative histopathology. In a subcutaneous niche, material weight did not influence foreign body response. PET stimulated earlier inflammation than PP and PGA, which normalized over 28 days. Multifilament meshes recruited foreign body giant cells, which were largely absent from monofilaments. Using CD68, PGA was demonstrated to be the greatest leukocyte-activating polymer at a number of the time points analysed. This research therefore highlights that underlying polymer composition may be more over-arching in deciding the inflammatory properties of surgical meshes, based on increased macrophagic responses to PGA vs alternative base polymers of comparable weights and porosities. Copyright © 2013 John Wiley & Sons, Ltd.

Physiological change under OsHV-1 contamination in Pacific oyster Crassostrea gigas through massive mortality events on fields

BACKGROUND

Massive mortalities have been observed in France since 2008 on spat and juvenile Pacific oysters, Crassostrea gigas. A herpes virus called OsHV-1, easily detectable by PCR, has been implicated in the mortalities as demonstrated by the results of numerous field studies linking mortality with OsHV-1 prevalence. Moreover, experimental infections using viral particles have documented the pathogenicity of OsHV-1 but the physiological responses of host to pathogen are not well known.

RESULTS

The aim of this study was to understand mechanisms brought into play against the virus during infection in the field. A microarray assay has been developed for a major part of the oyster genome and used for studying the host transcriptome across mortality on field. Spat with and without detectable OsHV-1 infection presenting or not mortality respectively were compared by microarray during mortality episodes. In this study, a number of genes are regulated in the response to pathogen infection on field and seems to argue to an implication of the virus in the observed mortality. The result allowed establishment of a hypothetic scheme of the host cell's infection by, and response to, the pathogen.

CONCLUSIONS

This response shows a "sensu stricto" innate immunity through genic regulation of the virus OsHV-1 life cycle, but also others biological processes resulting to complex interactions between host and pathogens in general.

The role of Serpine-1 and Tissue inhibitor of metalloproteinase type-1 in early host responses to Staphylococcus aureus intracutaneous infection of mice

Staphylococcus aureus is a common cause of skin and soft tissue infections in animal and humans. In the current study, we hypothesized that early host responses to S. aureus infection leading to the recruitment of neutrophils and control of the bacterium at the site of infection depend on the expression of Serpine-1 and Tissue inhibitor of metalloproteinase type-1, two important endogenous proteinase inhibitors that possess regulatory properties on a variety of pathophysiological conditions. Using a mouse model of skin infection and single-gene and double-gene knockout mice, however, our observations showed that Serpine-1 and Tissue inhibitor of metalloprotease type-1 did not impact the number of bacteria accumulating at the site of infection. Double-gene knockout mice further had the same volume of accumulating host cells at the site of infection, while single Tissue inhibitor of metalloprotease type-1 knockout mice showed a decreased number of cells. Follow-up studies demonstrated changes in Serpine-1, Tissue inhibitor of metalloprotease type-1 and IL-6 plasma levels following challenge. In addition, double-gene knockout mice did not differ from wild-type mice in white blood cell, granulocyte and leucocyte counts, while single-gene genotypes differed in these phenotypes.

Association of interleukin-4 and interleukin-17F polymorphisms in periodontitis in Dravidian ethnicity

BACKGROUND:

Complex network of pro and anti-inflammatory cytokines are known to act in inflamed periodontal tissue. This study explores the distribution of interleukin (IL)-4 (+33 C/T) and IL-17F (7383A/G, 7488A/G) gene polymorphism in chronic and aggressive periodontitis subjects of Dravidian ethnicity.

MATERIALS AND METHODS:

This case control study consisted of 124 periodontitis individuals comprising of 63 chronic and 61 aggressive periodontitis subjects as cases, and control group consisted of 101 healthy subjects. All subjects were genotyped for IL-4 + 33C/T, IL-17F 7383A/G, 7488A/G by polymerase chain reaction amplification followed by TaqMan assay for IL-4 + 33C/T, restriction enzyme digestion and gel electrophoresis for IL-17F 7383A/G and sequencing for IL-17F 7488A/G.

RESULTS:

IL-4 + 33C/T was significantly associated with periodontitis (P < 0.05) at both allelic and genotypic level. In subgroup analysis also significant difference (P < 0.05) in allelic distribution between aggressive periodontitis and control group for loci IL-4 + 33C/T was noted. However, there was a lack of association between IL-17F 7383A/G and IL-17F 7488A/G with periodontitis and its sub-groups at both allelic and genotypic levels.

CONCLUSIONS:

In Malayalam speaking Dravidian population IL-4 + 33C/T loci appears to be an important risk factor for periodontal disease with a leaning towards aggressive periodontitis. The association between IL-17F at 7383A/G and 7488A/G loci with either chronic or an aggressive periodontitis could not be ascertained.

Biocompatibility and potential of decellularized porcine small intestine to support cellular attachment and growth

The aim of this study was to decellularize a 30 cm long segment of porcine small intestine, determine its in vivo behaviour and assess the type of immunological reaction it induces in a quantitative manner. A segment of porcine ileum up to 30 cm long, together with its attached vasculature, was decellularized via its mesenteric arcade as a single entity. The quality of the acellular scaffold was assessed histologically and using molecular tools. The host response to the scaffold was evaluated in a rodent model. Stereological techniques were incorporated into quantitative analysis of the phenotype of the macrophages infiltrating the scaffold in vivo. Lengths of ileal scaffold, together with its attached vasculature, were successfully decellularized, with no evidence of intact cells and DNA or collagen and GAGs overdegradation. Analysis of explants harvested over 2 months postimplantation revealed full-thickness recellularization and no signs of foreign body or immune reactions. Macrophage profiling proved that between weeks 4 and 8 in vivo there was a switch from an M1 (pro-inflammatory) to an M2 (pro-remodelling) type of response. We show here that the decellularization process results in a biocompatible and non-toxic matrix that upon implantation triggers cellular infiltration and angiogenesis, primarily characterized by a pro-remodelling type of mononuclear response, without inducing foreign body reaction or fibrosis.

The effect of 'Candidatus Liberibacter asiaticus' infection on the proteomic profiles and nutritional status of pre-symptomatic and symptomatic grapefruit (Citrus paradisi) plants

BACKGROUND

Huanglongbing (HLB) is a highly destructive citrus disease which threatens citrus production worldwide and 'Candidatus Liberibacter asiaticus' (Las), a non-culturable phloem-limited bacterium, is an associated causal agent of the disease. To better understand the physiological and molecular processes involved in host responses to Las, 2-DE and mass spectrometry analyses, as well as ICP spectroscopy analysis were employed to elucidate the global protein expression profiles and nutrient concentrations in leaves of Las-infected grapefruit plants at pre-symptomatic or symptomatic stages for HLB.

RESULTS

This study identified 123 protein spots out of 191 spots that showed significant changes in the leaves of grapefruit plants in response to Las infection and all identified spots matched to 69 unique proteins/peptides. A down-regulation of 56 proteins including those associated with photosynthesis, protein synthesis, and metabolism was correlated with significant reductions in the concentrations of Ca, Mg, Fe, Zn, Mn, and Cu in leaves of grapefruit plants in response to Las infection, particularly in symptomatic plants. Oxygen-evolving enhancer (OEE) proteins, a PSI 9 kDa protein, and a Btf3-like protein were among a small group of proteins that were down-regulated in both pre-symptomatic and symptomatic plants in response to Las infection. Furthermore, a Las-mediated up-regulation of 13 grapefruit proteins was detected, which included Cu/Zn superoxide dismutase, chitinases, lectin-related proteins, miraculin-like proteins, peroxiredoxins and a CAP 160 protein. Interestingly, a Las-mediated up-regulation of granule-bound starch synthase was correlated with an increase in the K concentrations of pre-symptomatic and symptomatic plants.

CONCLUSIONS

This study constitutes the first attempt to characterize the interrelationships between protein expression and nutritional status of Las-infected pre-symptomatic or symptomatic grapefruit plants and sheds light on the physiological and molecular mechanisms associated with HLB disease development.

Rheumatoid arthritis in the elderly and its relationship with periodontitis: a review

Periodontitis and rheumatoid arthritis are chronic inflammatory diseases commonly seen in the elderly. It has been proposed that the two conditions are interrelated and influence the severity of each other. Recently, the role of Porphyromonas gingivalis, a periodontopathogen, has been explained in the pathogenesis and progression of rheumatoid arthritis. It can be inferred from the present review that the two conditions share a common pathobiology, genetics and environmental risk factors. Furthermore, a thorough understanding of the aforementioned mechanisms might enable the development of conjoint treatment modalities beneficial in treating the geriatric population afflicted by both the disorders.

Host response to xenograft ECM implantation is not different between the shoulder and body wall sites in the rat model

In the context of tendon and ligament repair, mechanical loading and the presence of joint synovial fluid are known to profoundly influence the form and function of the repair tissue and potentially the host response to biomaterials. Previously, we demonstrated that a xenograft extra cellular matrix (ECM) scaffold implanted in the rat shoulder elicited a unique host response from that seen in the body wall. However, the host response to xenografts implanted in shoulders with a tendon/capsule injury was not different from xenografts implanted in shoulders with no injury. In the current study, we hypothesized that varying clinically relevant surgical and environmental factors would introduce significant differences in host response to xenograft implantation at the shoulder. Contrary to our hypothesis, we found no significant differences in host response between any shoulder implantation conditions or between shoulder and body wall implantation in the rat model. These findings suggest that there is no advantage to using an orthotopic shoulder model to investigate the host response to rotator cuff scaffold materials in the rat model, and due to the insensitivity of its host response to various clinically relevant surgical conditions, may suggest that the rat does not provide a surrogate for directly translating the host response to biomaterials to the human application.

The core mouse response to infection by neospora caninum defined by gene set enrichment analyses

In this study, the BALB/c and Qs mouse responses to infection by the parasite Neospora caninum were investigated in order to identify host response mechanisms. Investigation was done using gene set (enrichment) analyses of microarray data. GSEA, MANOVA, Romer, subGSE and SAM-GS were used to study the contrasts Neospora strain type, Mouse type (BALB/c and Qs) and time post infection (6 hours post infection and 10 days post infection). The analyses show that the major signal in the core mouse response to infection is from time post infection and can be defined by gene ontology terms Protein Kinase Activity, Cell Proliferation and Transcription Initiation. Several terms linked to signaling, morphogenesis, response and fat metabolism were also identified. At 10 days post infection, genes associated with fatty acid metabolism were identified as up regulated in expression. The value of gene set (enrichment) analyses in the analysis of microarray data is discussed.

Chemically modified tetracyclines: Novel therapeutic agents in the management of chronic periodontitis

Chronic periodontitis is a complex infection initiated by gram-negative bacteria which destroy the supporting structures of the tooth. Recently, it has been recognized that it is the host response to bacterial infection which causes greater destruction of the connective tissue elements, periodontal ligament and alveolar bone in periodontitis. This has led to the development of various host modulating approaches to target cells and their destructive mediators involved in tissue degradation. Chemically modified tetracyclines (CMTs) are derivatives of tetracycline group of drugs which lack antimicrobial action but have potent host modulating affects. They inhibit pathologically elevated matrix metal loproteinases, pro-inflammtory cytokines and other destructive mediators. Bone resorption is also suppressed due to their combined anti-proteinase and apoptotic affects on osteoblasts and osteoclasts, respectively. Development of resistant bacteria and gastrointestinal toxicity seen with parent tetracyclines is not produced by CMTs. Hence, CMTs are viewed as potential therapeutic agents in the management of chronic diseases like periodontitis that involve destruction of connective tissue and bone.

Analysis of gut microbial regulation of host gene expression along the length of the gut and regulation of gut microbial ecology through MyD88

BACKGROUND

The gut microbiota has profound effects on host physiology but local host-microbial interactions in the gut are only poorly characterised and are likely to vary from the sparsely colonised duodenum to the densely colonised colon. Microorganisms are recognised by pattern recognition receptors such as Toll-like receptors, which signal through the adaptor molecule MyD88.

METHODS

To identify host responses induced by gut microbiota along the length of the gut and whether these required MyD88, transcriptional profiles of duodenum, jejunum, ileum and colon were compared from germ-free and conventionally raised wild-type and Myd88-/- mice. The gut microbial ecology was assessed by 454-based pyrosequencing and viruses were analysed by PCR.

RESULTS

The gut microbiota modulated the expression of a large set of genes in the small intestine and fewer genes in the colon but surprisingly few microbiota-regulated genes required MyD88 signalling. However, MyD88 was essential for microbiota-induced colonic expression of the antimicrobial genes Reg3β and Reg3γ in the epithelium, and Myd88 deficiency was associated with both a shift in bacterial diversity and a greater proportion of segmented filamentous bacteria in the small intestine. In addition, conventionally raised Myd88-/- mice had increased expression of antiviral genes in the colon, which correlated with norovirus infection in the colonic epithelium.

CONCLUSION

This study provides a detailed description of tissue-specific host transcriptional responses to the normal gut microbiota along the length of the gut and demonstrates that the absence of MyD88 alters gut microbial ecology.

Effect of implantation site and injury condition on host response to human-derived fascia lata ECM in a rat model

The host response and remodeling of ECM scaffolds are believed to be critical determinants of success or failure in repair or reconstructive procedures. Host response has been investigated in subcutaneous or abdominal wall implantation models. The extent to which evaluation of the host response to ECM intended for tendon or ligament repair should be performed in an orthotopic site is not known. This study compared the host response to human-derived fascia lata ECM among various implantation sites in the rat model. Results showed that a xenograft in the rat shoulder does not exhibit a different host response at 7 days from xenograft in the body wall, suggesting that either site may be appropriate to study the early host response to biologic grafts as well as the effect of various treatments aimed to modify the early host response. By 28 days, a xenograft in the rat shoulder does elicit a unique host response from that seen in the body wall. Therefore, it may be more appropriate to use an orthotopic shoulder model for investigating the long-term host response and remodeling of biologic grafts to be used for rotator cuff repair.

Discovery proteomics and nonparametric modeling pipeline in the development of a candidate biomarker panel for dengue hemorrhagic fever

Secondary dengue viral infection can produce capillary leakage associated with increased mortality known as dengue hemorrhagic fever (DHF). Because the mortality of DHF can be reduced by early detection and intensive support, improved methods for its detection are needed. We applied multidimensional protein profiling to predict outcomes in a prospective dengue surveillance study in South America. Plasma samples taken from initial clinical presentation of acute dengue infection were subjected to proteomics analyses using ELISA and a recently developed biofluid analysis platform. Demographics, clinical laboratory measurements, nine cytokines, and 419 plasma proteins collected at the time of initial presentation were compared between the DF and DHF outcomes. Here, the subject's gender, clinical parameters, two cytokines, and 42 proteins discriminated between the outcomes. These factors were reduced by multivariate adaptive regression splines (MARS) that a highly accurate classification model based on eight discriminant features with an area under the receiver operator curve (AUC) of 0.999. Model analysis indicated that the feature-outcome relationship were nonlinear. Although this DHF risk model will need validation in a larger cohort, we conclude that approaches to develop predictive biomarker models for disease outcome will need to incorporate nonparametric modeling approaches.

Expression quantitative trait Loci for extreme host response to influenza a in pre-collaborative cross mice

Outbreaks of influenza occur on a yearly basis, causing a wide range of symptoms across the human population. Although evidence exists that the host response to influenza infection is influenced by genetic differences in the host, this has not been studied in a system with genetic diversity mirroring that of the human population. Here we used mice from 44 influenza-infected pre-Collaborative Cross lines determined to have extreme phenotypes with regard to the host response to influenza A virus infection. Global transcriptome profiling identified 2671 transcripts that were significantly differentially expressed between mice that showed a severe ("high") and mild ("low") response to infection. Expression quantitative trait loci mapping was performed on those transcripts that were differentially expressed because of differences in host response phenotype to identify putative regulatory regions potentially controlling their expression. Twenty-one significant expression quantitative trait loci were identified, which allowed direct examination of genes associated with regulation of host response to infection. To perform initial validation of our findings, quantitative polymerase chain reaction was performed in the infected founder strains, and we were able to confirm or partially confirm more than 70% of those tested. In addition, we explored putative causal and reactive (downstream) relationships between the significantly regulated genes and others in the high or low response groups using structural equation modeling. By using systems approaches and a genetically diverse population, we were able to develop a novel framework for identifying the underlying biological subnetworks under host genetic control during influenza virus infection.

The active contribution of Toll-like receptors to allergic airway inflammation

Epithelia lining the respiratory tract represent a major portal of entry for microorganisms and allergens and are equipped with innate and adaptive immune signaling receptors for host protection. These include Toll-like receptors (TLRs) that recognize microbial components and evoke diverse responses in cells of the respiratory system. TLR stimulation by microorganism-derived molecules activates antigen presenting cells, control T helper (Th) 1, Th2, and Th17 immune cell differentiation, cytokine production by mast cells, and activation of eosinophils. It is clear that TLR are involved in the pathophysiology of allergic airway diseases such as asthma. Dendritic cells (DCs), a kind of antigen presenting cells, which play a key role in the induction of allergic airway inflammation, are privileged targets for pathogen associated molecular patterns (PAMPs). During the allergic responses, engagement of TLRs on DCs determines the Th2 polarization of the T cells. TLR signaling in mast cells increases the release of IL-5, and TLR activation of airway epithelial cells forces the generation of proallergic Th2 type of cytokines. Although these responses aim to protect the host, they may also result in inflammatory tissue damage in the airway. Under certain conditions, stimulation of TLRs, in particular, TLR9, may reduce Th2-dependent allergic inflammation by induction of Th1 responses. Therefore, understanding the complex regulatory roles of TLRs in the pathogenesis of allergic airway inflammation should facilitate the development of preventive and therapeutic measures for asthmatic patients.

Francisella Subverts Innate Immune Signaling: Focus On PI3K/Akt

Intracellular bacterial pathogens exploit host cells as a part of their lifecycle, and they do so by manipulating host cell signaling events. Many such bacteria are known to produce effector proteins that promote cell invasion, alter membrane trafficking, and disrupt signaling cascades. This review highlights recent advances in our understanding of signaling pathways involved in host cell responses to Francisella tularensis, a facultative Gram-negative intracellular pathogen that causes tularemia. We highlight several key pathways that are targeted by Francisella, with a focus on the phosphatidylinositol 3-kinase/Akt pathway. Lastly, we discuss the emerging role of microRNAs (miRs), specifically miR-155, as a key regulator of host signaling and defense.

Francisella Subverts Innate Immune Signaling: Focus On PI3K/Akt

Intracellular bacterial pathogens exploit host cells as a part of their lifecycle, and they do so by manipulating host cell signaling events. Many such bacteria are known to produce effector proteins that promote cell invasion, alter membrane trafficking, and disrupt signaling cascades. This review highlights recent advances in our understanding of signaling pathways involved in host cell responses to Francisella tularensis, a facultative Gram-negative intracellular pathogen that causes tularemia. We highlight several key pathways that are targeted by Francisella, with a focus on the phosphatidylinositol 3-kinase/Akt pathway. Lastly, we discuss the emerging role of microRNAs (miRs), specifically miR-155, as a key regulator of host signaling and defense.