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.

Confronting the next influenza pandemic with anti-inflammatory and immunomodulatory agents: why they are needed and how they might work

Despite the best efforts of influenza scientists, companies and health officials to prepare for the next pandemic, most of the world's people will not have access to affordable supplies of vaccines and antiviral agents. They will have to rely on 19th century public health 'technologies' to see them through. In the 21st century, science ought to be able to provide something better. Influenza scientists study the molecular characteristics of influenza viruses and their signaling effects in cell culture and animal models of infection. While these studies have been enormously informative, they have been unable to explain the system-wide effects of influenza on the host, the increased mortality of younger adults in the 1918 influenza pandemic and the much lower mortality rates in children who were more commonly infected with the 1918 virus. Experiments by non-influenza scientists have defined common cell signaling pathways for acute lung injury caused by different agents, including inactivated H5N1 influenza virus. These pathways include several molecular targets that are up-regulated in acute lung injury and down-regulated by anti-inflammatory and immunomodulatory agents, including statins, fibrates, and glitazones. These agents also help reverse the mitochondrial dysfunction that accompanies multi-organ failure, something often seen in fatal Influenza. Observational studies suggest that statins are beneficial in treating patients with pneumonia (there are no such studies for fibrates and glitazones). Other studies suggest that these agents might be able to 'roll back' the self-damaging host response of young adults to the less damaging response of children and thus save lives. Research is urgently needed to determine whether these and other agents that modify the host response might be useful in managing H5N1 influenza and the next pandemic.

Molecular responses of Lotus japonicus to parasitism by the compatible species Orobanche aegyptiaca and the incompatible species Striga hermonthica

Lotus japonicus genes responsive to parasitism by the compatible species Orobanche aegyptiaca and the incompatible species Striga hermonthica were isolated by using the suppression subtractive hybridization (SSH) strategy. O. aegyptiaca and S. hermonthica parasitism specifically induced the expression of genes involved in jasmonic acid (JA) biosynthesis and phytoalexin biosynthesis, respectively. Nodulation-related genes were almost exclusively found among the Orobanche-induced genes. Temporal gene expression analyses revealed that 19 out of the 48 Orobanche-induced genes and 5 out of the 48 Striga-induced genes were up-regulated at 1 dai. Four genes, including putative trypsin protease inhibitor genes, exhibited systemic up-regulation in the host plant parasitized by O. aegyptiaca. On the other hand, S. hermonthica attachment did not induce systemic gene expression.

Semliki Forest virus strongly reduces mosquito host defence signaling

The Alphavirus genus within the Togaviridae family contains several important mosquito-borne arboviruses. Other than the antiviral activity of RNAi, relatively little is known about alphavirus interactions with insect cell defences. Here we show that Semliki Forest virus (SFV) infection of Aedes albopictus-derived U4.4 mosquito cells reduces cellular gene expression. Activation prior to SFV infection of pathways involving STAT/IMD, but not Toll signaling reduced subsequent virus gene expression and RNA levels. These pathways are therefore not only able to mediate protective responses against bacteria but also arboviruses. However, SFV infection of mosquito cells did not result in activation of any of these pathways and suppressed their subsequent activation by other stimuli.

Anti-inflammatory polymeric coatings for implantable biomaterials and devices

Synthetic polymer coatings are used extensively in modern medical devices and implants because of their material versatility and processability. These coatings are designed for specific applications by controlling composition and physical and chemical properties, and they can be formed into a variety of complex structures and shapes. However, implantation of these materials into the body elicits a strong inflammatory host response that significantly limits the integration and biological performance of devices. Biomaterial-mediated inflammation is a complex reaction involving protein adsorption, leukocyte recruitment and activation, secretion of inflammatory mediators, and fibrous encapsulation of the implant. Significant research efforts have focused on modifying material properties using various anti-inflammatory polymeric surface coatings to generate more biocompatible implants. This minireview provides a brief background on the events of biomaterial-mediated inflammation and highlights various approaches used for modifying material surfaces to modulate inflammatory responses. These include both passive and active strategies, such as nonfouling surface treatments and delivery of anti-inflammatory agents, respectively. Novel approaches will be needed to extend the in vivo lifetime and performance of devices and reduce the need for multiple implantation surgeries.

The damage-response framework of microbial pathogenesis and infectious diseases

Historical and most currently held views of microbial pathogenesis and virulence are plagued by confusing and imprecise terminology and definitions that require revision and exceptions to accommodate new basic science and clinical information about microbes and infectious diseases. These views are also inherently unable to account for the ability of some microbes to cause disease in certain, but not other hosts, because they are grounded in singular, either microbe-or host-centric views. The damage-response framework is an integrated theory of microbial pathogenesis that puts forth the view that microbial pathogenesis reflects the outcome of an interaction between a host and a microbe, with each entity contributing to the nature of the outcome, which in turn depends on the amount of host damage that results from the host-microbe interaction. This view is able to accommodate new information and explain why infection with the same microbe can have different outcomes in different hosts. This chapter describes the origins and conceptual underpinnings of and the outcomes of infection put forth in, the damage-response framework.

Control of antiviral defenses through hepatitis C virus disruption of retinoic acid-inducible gene-I signaling

Hepatitis C virus (HCV) is a major human pathogen that infects 170 million people. A hallmark of HCV is its ability to establish persistent infections reflecting the evasion of host immunity and interference with alpha/beta-IFN innate immune defenses. We demonstrate that disruption of retinoic acid-inducible gene I (RIG-I) signaling by the viral NS3/4A protease contributes to the ability of HCV to control innate antiviral defenses. RIG-I was essential for virus or HCV RNA-induced signaling to the IFN-beta promoter in human hepatoma cells. This signaling was disrupted by the protease activity of NS3/4A, which ablates RIG-I signaling of downstream IFN regulatory factor 3 and NF-kappaB activation, attenuating expression of host antiviral defense genes and interrupting an IFN amplification loop that otherwise suppresses HCV replication. Treatment of cells with an active site inhibitor of the NS3/4A protease relieved this suppression and restored intracellular antiviral defenses. Thus, NS3/4A control of RIG-I supports HCV persistence by preventing IFN regulatory factor 3 and NF-kappaB activation. Our results demonstrate that these processes are amenable to restoration through pharmacologic inhibition of viral protease function.

Risk factors for periodontitis

In recent years, it has become apparent that the pathogenesis of periodontal diseases is more complex than the presence of virulent microorganisms. In fact, it is now widely accepted that susceptibility to periodontitis varies greatly between individuals who harbor the same pathogenic microflora. To date, the bulk of evidence points to the host response to bacterial challenge as a major determinant of susceptibility. In this review, we will assess the data implicating various inherited and acquired risk factors for susceptibility to periodontal diseases.

Histology of White Pine Blister Rust in Needles of Resistant and Susceptible Eastern White Pine

White pine blister rust, Cronartium ribicola, has plagued the forests of North America for almost a century. Over past decades, eastern white pine (Pinus strobus) that appear to tolerate the disease have been selected and incorporated into breeding programs. Seeds from P. strobus with putative resistance were collected from Oconto River Seed Orchard, Nicolet National Forest, WI. Seedlings were grown for 5 months and artificially inoculated with basidiospores of C. ribicola in two replicated greenhouse experiments. Needles from infected seedlings were fixed, sectioned, and stained with a variety of histological reagents, and rate of mortality for the remaining seedlings was monitored. The most susceptible families suffered 50% mortality in approximately half the time of the more resistant families. Extensive inter- and intracellular hyphae were observed in needles from seedlings of susceptible families, whereas hyphal proliferation was restricted in needles of resistant seedlings. Needles from resistant families had pronounced responses to infection. Phenolics, observed with phloroglucinol-HCl staining, were deposited around infection sites where dense mycelial masses were present. Abnormal host cell growth and rapid cell death in the immediate area of infection were also observed in some eastern white pine families.

Histological features and HLA class II alleles in hepatitis C virus chronically infected patients with persistently normal alanine aminotransferase levels

OBJECTIVE

A significant proportion of individuals with chronic hepatitis C virus (HCV) infection have persistently normal alanine aminotransferase (ALT) levels. Although data are controversial, such patients usually have weaker histological damage and a lower progression rate of fibrosis. The aims of this study were: (1) to compare demographic, virological, and histological parameters of HCV patients with normal ALT values with those of HCV patients with elevated ALT levels; and (2) to determine whether HLA class II alleles contribute to the persistence of normal ALT levels in HCV patients.

PATIENTS AND METHODS

Eighty three patients with chronic HCV infection and persistently normal ALT values (group 1) and 233 patients with chronic HCV infection and elevated ALT levels (group 2) were studied. Histological features were expressed using Knodell and Metavir scores. HLA DRB1* and DQB1* genotyping was performed using hybridisation with sequence specific oligonucleotides after genomic amplification. The kappa2 and Fisher's exact tests were used to compare discrete variables and phenotype frequencies between the two groups, and Wilcoxon's test was used for continuous variables. A multivariate logistic regression model was used to determine which variables predicted normal ALT values.

RESULTS

ALT levels were correlated with the severity of liver damage. In group 1, 93% of patients had an F0 or F1 Metavir index of fibrosis compared with 47% of patients in group 2 (p<0.001). A longer duration of infection (p<0.001) and increased DRB1*11 phenotype frequency (pc=0.03) were observed among patients with normal ALT. The two groups did not differ with regard to the mode of contamination or viral genotype. After logistic regression, young age (p=0.0008), female sex (p=0.01), long duration of infection (p=0.0001), and HLA DRB1*11 (p=0.050) were more strongly associated with persistence of normal ALT.

CONCLUSIONS

Our study confirms that patients with chronic hepatitis C and normal ALT levels have less severe liver disease than those with elevated ALT levels. This particular biochemical outcome may be explained, at least in part, by host immunogenetic factors such as the presence of HLA-DRB1*11.

Surface Colonization, Penetration, and Lesion Formation on Grapes Inoculated Fresh or After Cold Storage with Single Airborne Conidia of Botrytis cinerea

Infection of grapes by different densities of airborne conidia of Botrytis cinerea was investigated on table grapes (cultivar Dauphine) harvested ripe (16°Brix) and inoculated fresh, or after SO₂ treatment and 8-week storage at -0.5°C. Berries were detached at each inoculation and dusted with dry conidia in a settling tower. Following inoculation, the fresh berries were incubated for 24 h at high relative humidity (≥93%), or were overlaid with wet sterile paper towels. Cold-stored berries were incubated at high relative humidity. The effect of conidial density on surface colonization, penetration, and lesion formation was determined by surface sterilization, isolation, and freezing studies on fresh berries. Only symptom expression was determined on cold-stored berries. Fluorescence microscopy of skin segments showed that conidia were consistently deposited as single cells, and not in pairs or groups, on berry surfaces. Individual conidia, at all densities tested, readily infected the cold-stored berries and formed separate lesions after 2 days. Although the cold-stored berries were highly susceptible, lesion numbers were not related to conidial density at low inoculum dosages (0.67 to 2.60 conidia per mm² berry surface). Lesion numbers tended to increase exponentially at higher dosages (3.24 to 3.88 conidia per mm² berry surface). Individual conidia, however, did not induce any disease symptoms on fresh berries. Removal of the pathogen after 24-h incubation from the surface of fresh berries by ethanol, and subsequent incubation of excised skin segments revealed that, irrespective of the conidial density or the wetness regime, less than 2% of skin segments were penetrated. Furthermore, increasing densities of conidia did not lead to higher rates of surface colonization and skin penetration. The low incidence of disease caused on fresh berries and high disease incidence induced after prolonged cold storage indicated that infection was not governed by conidial density on berry surfaces, but by the level of host resistance.

A secreted Salmonella protein with homology to an avirulence determinant of plant pathogenic bacteria

Bacterial pathogens have evolved sophisticated mechanisms to interact with their hosts. A specialized type III protein secretion system capable of translocating bacterial proteins into host cells has emerged as a central factor in the interaction between a variety of mammalian and plant pathogenic bacteria with their hosts. Here we describe AvrA, a novel target of the centisome 63 type III protein secretion system of Salmonella enterica. AvrA shares sequence similarity with YopJ of the animal pathogen Yersinia pseudotuberculosis and AvrRxv of the plant pathogen Xanthomonas campestris pv. vesicatoria. These proteins are the first examples of putative targets of type III secretion systems in animal and plant pathogenic bacteria that share sequence similarity. They may therefore constitute a novel family of effector proteins with related functions in the cross-talk of these pathogens with their hosts.

Early Root Response to Meloidogyne incognita in Resistant and Susceptible Alfalfa Cultivars

The early events of Meloidogyne incognita behavior and associated host responses following root penetration were studied in resistant (cv. Moapa 69) and susceptible (cv. Lahontan) alfalfa. Ten-day-old seedlings of alfalfa cultivars were inoculated with second-stage juveniles (J2) and harvested 12, 24, 48, and 72 hours and 7, 14, and 21 days later. Both cultivars supported similar root penetration and initial J2 migration. By 72 hours after inoculation the majority of J2 were amassed inside the vascular cylinder in roots of susceptible Lahontan, while J2 had not entered the vascular cylinder of resistant Moapa 69 and remained clumped at the root apex. Nematode development progressed normally in Lahontan, but J2 were not observed in Moapa 69 after day 7. The greatest differences between RNA translation products isolated from inoculated and uninoculated roots of Lahanton occurred 72 hours after inoculation. Only minor differences in gene expression were observed between inoculated and uninoculated Moapa 69 roots at 72 hours. Comparison of translation products from inoculated versus mechanically wounded Lahontan roots revealed products that were specific to or enhanced in nematode-infected plants. Moapa 69 appears to possess a type of resistance to M. incognita that does not depend on a conventional hypersensitive response.

Effect of Simulated Acid Rain on Bursaphelenchus xylophilus Infection of Pine Seedlings

White, Scots, and Austrian 3-year-old pine seedlings were treated with conditions simulating acid rain and inoculated with the white pine specific pathotype of Bursaphelenchus xylophilus, VPSt-1. Oleoresin concentration increased slightly and carbohydrate concentration decreased in all seedlings treated with simulated acid rain (SAR). The changes were significantly increased after inoculation of SAR-treated white and Scots pine seedlings with VPSt-1. Wilting was delayed and nematode reproduction decreased in SAR-treated white pine seedlings inoculated with VPSt-1. SAR-treated Austrian pine seedlings were resistant to VPSt-1, but SAR-treated Scots pine seedlings lost tolerance to VPSt-1 and wilted 50-60 days after inoculation.

Carbohydrate Concentration in Pine as Affected by Inoculation with Bursaphelenchus xylophilus

Pines responded to inoculation with Bursaphelenchus xylophilus by changes in reducing and nonreducing carbohydrate concentrations dependent on the pine species and the pathotype of B. xylophilus with which the trees were inoculated. Carbohydrate concentrations, in compatible pine-nematode pathotype combinations, decreased initially after inoculation and then increased slightly before decreasing to approximately 10% of the control levels as the seedlings wilted. In compatible nematode pathotype-pine species combinations, carbohydrate concentrations decreased and then increased as the nematode population densities declined.

Varietal Response and Estimates of Heritability of Resistance to Meloidogyne javanica in Carrots

With methods developed in this study, varietal responses to M. javanica were evaluated and heritability of resistance of two promising carrot cultivars was estimated. More egg masses were found on root systems inoculated with eggs added to the soil in three holes in 250 cm(3) cups than by mixing the inoculum with soil in the cups. A resistant breeding line, CNPH 1437, was discriminated from susceptible cultivar Nova Kuroda with inoculum levels higher than 2,000 eggs per cup. Greenhouse and field results suggested that cultivars Nantes Superior and Shin Kuroda were susceptible, Kuronan was somewhat tolerant, and Brasilia and Tropical were resistant to M. javanica. Nantes Superior or Shin Kuroda yielded less in carbofuran-treated soil (3 kg a.i./ha) than Kuronan, Brasilia, and Tropical did in nontreated soil. However, incorporation of the nematicide greatly increased yields of Kuronan (32%), Brasilia (62%), and Tropical (91%). Primary root galling at the seedling stage was an adequate parameter for resistance evaluation. Estimated heritability were 0.48 +/- 0.07 for primary root galling and 0.35 +/- 0.08 for egg mass production in Brasilia, and 0.16 +/- 0.11 for primary root galling and 0.31 +/- 0.09 for egg mass production in Kuronan.

Morphometrics, Illustration, and Histopathology of Sphaeronema rumicis on Cottonwood in Utah

The morphology of a population of Sphaeronema rumicis Kir'yanova found on cottonwood in Utah is illustrated by light and scanning electron micrographs, as well as by drawings. This is the first report of males of S. rumicis, a species also not known previously to occur in North America. S. rumicis females on cottonwood in the United States were smaller than those found by Kir'yanova on sorrel in the USSR. Females and second-stage juveniles (J2) from the United States had slightly shorter stylets than did females and J2 from the USSR. Males were vermiform and had degenerate esophagi. On secondary cottonwood roots S. rumicis induces formation of a syncytium originating from proliferated pericyclic cells. Thick outer walls, wall protuberances, absence of cell wall ingrowths, dense cytoplasm, and hypertrophied nuclei were the main characteristics of syncytia observed in S. rumicis-infected cottonwood roots.

Cactodera eremica n. sp., Afenestrata africana (Luc et al., 1973) n. gen., n. comb., and an Emended Diagnosis of Sarisodera Wouts and Sher, 1971 (Heteroderidae)

Systematic contributions to Heteroderidae include description of Cactodera eremica n. sp., an emended diagnosis of Sarisodera Wouts and Sher, 1971, and proposal of a new genus and new combination, Afenestrata africana (synonym Sarisodera africana Luc et al., 1973). Cactodera eremica, from the roots of shadscale in Utah, most closely resembles Cactodera thornei (Golden and Raski, 1977) but differs by the presence of a finely striated cuticle, a fine surface pattern on eggs, a shorter female stylet, distance of the DGO from the stylet, vulval slit, and smaller diameter of circumfenestra, as well as a shorter tail in second-stage juveniles. The response of the host to C. eremica is similar to other Heterodera sensu lato including a large syncytium with wall ingrowths. The diagnosis of Sarisodera is emended to exclude cysts, which do not form in the type species, S. hydrophila. Afenestrata africana differs from S. hydrophila by the formation of cysts, the dorsal position of the anus in females, the shorter stylet, and a pore-like phasmid opening in second-stage juveniles. In addition, the lip pattern of males and juveniles is characterized by a greater degree of fusion of lip parts, the host response is a syncytium (versus a single uninucleate giant cell in S. hydrophila), and the cuticle is thinner and lacks a D layer. Unlike Heterodera, the cyst of Afenestrata lacks fenestrae.