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Infection and Immunity

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https://www.readbyqxmd.com/read/28396325/metabolic-genetic-screens-reveal-multidimensional-regulation-of-virulence-gene-expression-in-listeria-monocytogenes-and-an-aminopeptidase-that-is-critical-for-prfa-protein-activation
#1
Sivan Friedman, Marika Linsky, Lior Lobel, Lev Rabinovich, Nadejda Sigal, Anat A Herskovits
Listeria monocytogenes is an environmental saprophyte and intracellular bacterial pathogen. Upon invading mammalian cells, the bacterium senses abrupt changes in its metabolic environment, which are rapidly transduced to regulation of virulence gene expression. To explore the relationship between L. monocytogenes metabolism and virulence, we monitored virulence gene expression dynamics across a library of genetic mutants grown under two metabolic conditions known to activate the virulent state: charcoal-treated rich medium containing glucose 1-phosphate and minimal defined medium containing limiting concentrations of branched-chain amino acids (BCAAs)...
April 10, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28396324/giardia-alters-commensal-microbial-diversity-throughout-the-murine-gut
#2
N R Barash, J G Maloney, S M Singer, S C Dawson
Giardia lamblia is the most frequently identified protozoan cause of intestinal infection. Over one billion people are estimated to have acute or chronic giardiasis, with infection rates approaching 90% in endemic areas. Despite its significance in global health, the mechanisms of pathogenesis associated with giardiasis remain unclear as the parasite neither produces a known toxin nor induces a robust inflammatory response. Giardia colonization and proliferation in the small intestine of the host may, however, disrupt the ecological homeostasis of gastrointestinal commensal microbes and contribute to diarrheal disease associated with giardiasis...
April 10, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28396323/attenuated-phenotype-of-a-recent-house-finch-associated-mycoplasma-gallisepticum-isolate-for-domestic-poultry
#3
K Pflaum, E R Tulman, J Beaudet, X Liao, K V Dhondt, A A Dhondt, D M Hawley, D H Ley, K M Kerr, S J Geary
Mycoplasma gallisepticum, known primarily as a respiratory pathogen of domestic poultry, has emerged since 1994 as a significant pathogen of the house finch (Haemorhous mexicanus) causing severe conjunctivitis and mortality. House finch-associated M. gallisepticum (HFMG) spread rapidly and increased in virulence for the finch host in the Eastern United States. In the current study, we assessed virulence in domestic poultry with two temporally distant, yet geographically consistent, HFMG isolates which differ in virulence for house finches - Virginia 1994 (VA1994), the index isolate of the epidemic, and Virginia 2013 (VA2013), a recent isolate of increased house finch virulence...
April 10, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28396322/camp-elevating-capacity-of-the-adenylate-cyclase-toxin-hemolysin-is-sufficient-for-lung-infection-but-not-for-full-virulence-of-bordetella-pertussis
#4
Karolina Skopova, Barbora Tomalova, Ivan Kanchev, Pavel Rossmann, Martina Svedova, Irena Adkins, Ilona Bibova, Jakub Tomala, Jiri Masin, Nicole Guiso, Radim Osicka, Radislav Sedlacek, Marek Kovar, Peter Sebo
The adenylate cyclase toxin-hemolysin (CyaA, ACT or AC-Hly) of Bordetella pertussis targets phagocytic cells expressing the complement receptor 3 (CR3, Mac-1, αMβ2 integrin or CD11b/CD18). CyaA delivers into cells an N-terminal adenylyl cyclase (AC) enzyme domain that is activated by cytosolic calmodulin and catalyzes unregulated conversion of cellular ATP into cAMP, a key second messenger subverting bactericidal activities of phagocytes. In parallel, the hemolysin (Hly) moiety of CyaA forms cation-selective hemolytic pores that permeabilize target cell membranes...
April 10, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28396321/albumin-in-the-presence-of-calcium-elicits-a-massive-increase-in-extracellular-bordetella-adenylate-cyclase-toxin
#5
Laura A Gonyar, Mary C Gray, Gregory J Christianson, Borna Mehrad, Erik L Hewlett
Pertussis (whooping cough), caused by Bordetella pertussis (Bp), is resurging in the United States and worldwide. Adenylate cyclase toxin (ACT) is a critical factor in establishing infection with Bp and acts by specifically inhibiting the response of myeloid leukocytes to the pathogen. We report here that serum components, as discovered during growth in fetal bovine serum (FBS), elicit a robust increase in the amount of ACT, and ≥90% of this ACT is localized to the supernatant, unlike growth without FBS in which ≥90% is associated with the bacterium...
April 10, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28396320/dynamic-expression-of-the-baba-adhesin-and-its-babb-paralog-during-helicobacter-pylori-infection-in-rhesus-macaques
#6
Lori M Hansen, Pär Gideonsson, Don R Canfield, Thomas Borén, Jay V Solnick
Most Helicobacter pylori strains express the BabA adhesin, which binds to ABO/Leb blood group antigens on gastric mucin and epithelial cells, and is found more commonly in strains that cause peptic ulcer or gastric cancer, rather than asymptomatic infection. We and others have previously reported that in mice, gerbils, and rhesus macaques, Expression of babA is lost, either by phase variation or by gene conversion, in which the babB paralog recombines into the babA locus. The functional significance of loss of babA expression is unknown...
April 10, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28396319/host-resistance-to-plasmodium-induced-acute-immune-pathology-is-regulated-by-il-10-receptor-signalling
#7
Carla Claser, J Brian De Souza, Samuel G Thorburn, Georges Emile Grau, Eleanor M Riley, Laurent Rénia, Julius C R Hafalla
The resolution of malaria infection is dependent on a balance between pro-inflammatory and regulatory immune responses. Whilst early effector T cell responses are required for limiting parasitaemia, these responses need to be switched off by regulatory mechanisms in a timely manner to avoid immune-mediated tissue damage. Interleukin-10 (IL-10) receptor (IL-10R) signalling is considered to be a vital component of regulatory responses although its role in host resistance to severe immune pathology during acute malaria infections is not fully understood...
April 10, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28373357/the-legionella-pneumophila-incomplete-phosphotransferase-system-pts-is-required-for-optimal-intracellular-growth-and-maximal-expression-of-pmra-regulated-effectors
#8
Yariv Speiser, Tal Zusman, Anna Pasechnek, Gil Segal
The nitrogen phosphotransferase system (PTS(Ntr)) is a regulatory cascade present in many bacteria, where it controls different functions. This system is usually composed of three basic components: EI(Ntr), NPr and EIIA(Ntr) (encoded by the ptsP, ptsO and ptsN genes, respectively). In Legionella pneumophila, as well as in many other Legionella species, the EIIA(Ntr) component is missing. However, we found that deletion mutations in both ptsP and ptsO are partially attenuated for intracellular growth. Furthermore, these two PTS(Ntr) components were found to be required for maximal expression of effector-encoding genes regulated by the transcriptional activator PmrA...
April 3, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28373356/the-agr-like-quorum-sensing-system-is-required-for-necrotic-enteritis-pathogenesis-in-poultry-caused-by-clostridium-perfringens
#9
Qiang Yu, Dion Lepp, Iman Mehdizadeh Gohari, Tao Wu, Hongzhuan Zhou, Xianhua Yin, Hai Yu, John F Prescott, Shao-Ping Nie, Ming-Yong Xie, Joshua Gong
Recent studies have highlighted the importance of quorum sensing (QS) systems in the regulation of toxin production and virulence in Clostridium perfringens, which encodes at least two different systems: the Agr-like and LuxS. The role of QS in the pathogenesis of necrotic enteritis (NE) in poultry and the regulation of NetB, the key toxin involved, has not yet been investigated. We have generated isogenic agrB-null and complemented strains from parent CP1, and demonstrated that the virulence of the agrB-null mutant was strongly attenuated in a chicken NE model system, and restored by complementation...
April 3, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28373355/the-rhomboid-protease-glpg-promotes-the-persistence-of-extraintestinal-pathogenic-escherichia-coli-within-the-gut
#10
Colin W Russell, Amanda C Richards, Alexander S Chang, Matthew A Mulvey
Extraintestinal pathogenic Escherichia coli (ExPEC) strains are typically benign within the mammalian gut, but can disperse to extraintestinal sites to cause disease. As occupation of the intestinal tract is often a prerequisite for ExPEC-mediated pathogenesis, we set out to understand how ExPEC colonizes this niche. A screen using transposon sequencing (Tn-seq) was performed to search for genes within the ExPEC isolate F11 that are important for growth in intestinal mucus, which is thought to be a major source of nutrients for E...
April 3, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28373354/a-protective-role-for-macrophages-in-respiratory-francisella-tularensis-infection
#11
Donald J Steiner, Yoichi Furuya, Michael B Jordan, Dennis W Metzger
Francisella tularensis causes lethal pneumonia following infection of the lungs by targeting macrophages for intracellular replication; however, macrophages stimulated with interferon gamma (IFN-γ) can resist infection in vitro We therefore hypothesized that the protective effect of IFN-γ against F. tularensisin vivo requires macrophages receptive to stimulation. We found that lethality of pulmonary F. tularensis LVS infection was exacerbated under conditions of alveolar macrophage depletion, and in mice with a macrophage-specific defect in IFN-γ signaling (MIIG) mice...
April 3, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28373353/clumping-factor-b-promotes-adherence-of-staphylococcus-aureus-to-corneocytes-in-atopic-dermatitis
#12
Orla M Fleury, Maeve A McAleer, Cécile Feuillie, Cécile Formosa-Dague, Emily Sansevere, Désirée E Bennett, Aisling M Towell, W H Irwin McLean, Sanja Kezic, D Ashley Robinson, Padraic G Fallon, Timothy J Foster, Yves F Dufrêne, Alan D Irvine, Joan A Geoghegan
Staphylococcus aureus skin infection is a frequent and recurrent problem in children with the common inflammatory skin disease atopic dermatitis (AD). S. aureus colonises the skin of the majority of children with AD and exacerbates the disease. The first step during colonisation and infection is bacterial adhesion to the cornified envelope of corneocytes in the outer layer stratum corneum. Corneocytes from AD skin are structurally different to corneocytes from normal healthy skin. The objective of this study was to identify bacterial proteins that promote the adherence of S...
April 3, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28373352/the-perr-regulated-p1b-4-type-atpase-pmta-acts-as-a-ferrous-iron-efflux-pump-in-streptococcus-pyogenes
#13
Andrew G Turner, Cheryl-Lynn Y Ong, Karrera Y Djoko, Nicholas P West, Mark R Davies, Alastair G McEwan, Mark J Walker
Streptococcus pyogenes (group A Streptococcus; GAS) is an obligate human pathogen responsible for a broad spectrum of human disease. GAS has a requirement for metal homeostasis within the human host and as such, tightly modulates metal uptake and efflux during infection. Metal acquisition systems are required to combat metal sequestration by the host, while metal efflux systems are essential to protect against metal overload poisoning. Here, we investigated the function of PmtA (PerR-regulated metal transporter A), a P1B-4 type ATPase efflux pump, in the invasive GAS M1T1 strain 5448...
April 3, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28373351/key-role-of-capsular-polysaccharide-in-the-induction-of-systemic-infection-and-abortion-by-hypervirulent-campylobacter-jejuni
#14
Orhan Sahin, Samantha A Terhorst, Eric R Burrough, Zhangqi Shen, Zuowei Wu, Lei Dai, Yizhi Tang, Paul J Plummer, Ju Ji, Michael J Yaeger, Qijing Zhang
Campylobacter jejuni is a zoonotic pathogen, and a hypervirulent strain, named clone SA, has recently emerged as the predominant cause of ovine abortion in the United States. To induce abortion, orally ingested Campylobacter must translocate across the intestinal epithelium, spread systemically in the circulation, and reach the fetoplacental tissue. Bacterial factors involved in these steps are not well understood. C. jejuni is known to produce capsular polysaccharide (CPS), but the specific role CPS plays in systemic infection and particularly abortion in animals remains to be determined...
April 3, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28348057/host-immune-recognition-of-the-epidemic-cystic-fibrosis-pathogen-burkholderia-dolosa
#15
Damien Roux, Molly Weatherholt, Bradley Clark, Mihaela Gadjeva, Diane Renaud, David Scott, David Skurnik, Gregory P Priebe, Gerald Pier, Craig Gerard, Deborah R Yoder-Himes
Burkholderia dolosa caused an outbreak in the cystic fibrosis (CF) clinic at Boston Children's Hospital from 1998 to 2005 and led to the infection of over 40 patients, many of whom died due to complications from infection by this organism. To assess whether B. dolosa significantly contributes to disease or is recognized by the host immune response, mice were infected with a sequenced outbreak B. dolosa strain, AU0158, and responses compared to the well-studied CF pathogen, Pseudomonas aeruginosa In parallel, mice were also infected with a polar flagellin mutant of B...
March 27, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28348056/analysis-of-shigella-flexneri-resistance-biofilm-formation-and-transcriptional-profile-in-response-to-bile-salts
#16
Kourtney P Nickerson, Rachael B Chanin, Jeticia R Sistrunk, David A Rasko, Peter J Fink, Eileen M Barry, James P Nataro, Christina S Faherty
The Shigella species cause millions of cases of watery or bloody diarrhea each year, mostly in children in developing countries. While many aspects of Shigella colonic cell invasion are known, crucial gaps in knowledge remain regarding how the bacteria survive, transit, and regulate gene expression prior to infection. In this study, we define mechanisms of bile salts resistance and build on previous research highlighting induced virulence in S. flexneri strain 2457T following bile salts exposure. Typical growth patterns were observed within the physiological range of bile salts; however, growth was inhibited at higher concentrations...
March 27, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28348055/the-enigmatic-pe-ppe-multi-gene-family-of-mycobacteria-and-tb-vaccination
#17
Michael J Brennan
The genome of Mycobacterium tuberculosis (Mtb), the bacteria responsible for the disease tuberculosis, contains an unusual family of abundant antigens (PE/PPEs) . To date certain members of this multigene family occur only in mycobacteria that cause disease. It is possible that the numerous proteins encoded by these mycobacterial genes dictate the immune-pathogenesis of this bacterial pathogen. There is also evidence that some of these antigens are present at the cell surface and that they affect the pathology and immunology of the organism in many ways...
March 27, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28348054/the-oppd-gene-and-putative-peptidase-genes-may-be-required-for-virulence-in-mycoplasma-gallisepticum
#18
Chi-Wen Tseng, Chien-Ju Chiu, Anna Kanci, Christine Citti, Renate Rosengarten, Glenn F Browning, Philip F Markham
Relatively few virulence genes have been identified in pathogenic mycoplasmas, so we used signature-tagged mutagenesis to identify mutants of the avian pathogen Mycoplasma gallisepticum with reduced capacity to persist in vivo and compared the virulence of selected mutants in experimentally infected chickens. Four mutants had insertions in one of the two incomplete oppABCDF operons and a further three had insertions in distinct hypothetical genes, two containing peptidase motifs and one a member of a gene family...
March 27, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28348053/acanthamoeba-activates-macrophages-predominantly-through-tlr4-and-myd88-dependent-mechanisms-to-induce-il-12-and-il-6
#19
Antonella Cano, Antonella Mattana, Stuart Woods, Fiona L Henriquez, James Alexander, Craig W Roberts
Acanthamoeba castellanii is a free-living ubiquitous amoeba, with a worldwide distribution, that can occasionally infect humans, causing particularly severe infections in immune compromised individuals. Dissecting the immunology of Acanthamoeba infections has been considered problematic due to the very low incidence of disease despite the high exposure rates. Whilst macrophages are acknowledged as playing a significant role in Acanthamoeba infections little is known about how this facultative parasite influences macrophage activity...
March 27, 2017: Infection and Immunity
https://www.readbyqxmd.com/read/28348052/bile-acid-administration-elicits-an-intestinal-antimicrobial-program-and-reduces-the-bacterial-burden-in-two-mouse-models-of-enteric-infection
#20
Sarah Tremblay, Guillaume Romain, Mélisange Roux, Xi-Lin Chen, Kirsty Brown, Deanna L Gibson, Sheela Ramanathan, Alfredo Menendez
In addition to their chemical antimicrobial nature, bile acids (BA) are thought to have other functions in the homeostatic control of gastrointestinal immunity. However, those functions have remained largely undefined. In this work, we used ileal explants and mouse models of BA administration to investigate the role of BA in the regulation of the intestinal antimicrobial response. Mice fed on a diet supplemented with 0.1% chenodeoxycholic acid (CDCA) showed an upregulated expression of Paneth cell α-defensins as well as an increased synthesis of the type-C lectins Reg3b and Reg3g by the ileal epithelium...
March 27, 2017: Infection and Immunity
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