bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolution of EnterohemorrhagicEscherichia coliHemolysin Plasmids and the Locus for Enterocyte Effacement in Shiga Toxin-ProducingE. coli
Authors: Boerlin Patrick , Chen Shu , Colbourne John K. , Johnson Roger , De Grandis Stephanie , Gyles Carlton 
Published: December 2019

ABSTRACTThis study assessed the diversity of the enterohemorrhagicEscherichia coli(EHEC) hemolysin gene (ehxA) in a variety of Shiga toxin-producingE. coli(STEC) serotypes and the relationship betweenehxAtypes and virulence markers on the locus for enterocyte effacement (LEE). Restriction fragment length polymorphism of theehxAgene and flanking sequences and of theE. coliattaching and effacing (eae) gene was determined for 79 EHEC hemolysin-positive STEC isolates of 37 serotypes. Two main groups of EHEC hemolysin sequences and associated plasmids, which corresponded to theeae-positive and theeae-negative isolates, were delineated. Comparisons of theehxAgene sequences of representative isolates of each group showed that this gene and the rest of the EHEC hemolysin operon are highly conserved. Digestion of anehxAPCR product with the restriction endonucleaseTaqI showed a unique restriction pattern foreae-negative isolates and another one for isolates of serotypes O157:H7 and O157:NM. A conserved fragment of 5.6 kb with four potential open reading frames was identified on the EHEC hemolysin plasmid ofeae-positive STEC. Phylogenetic analysis of a subset of 27 STEC isolates, one enteropathogenicE. coliisolate, and a K-12 reference isolate showed thateae-positive STEC isolates all belong to a single evolutionary lineage and that the EHEC hemolysin plasmid and theehxAgene evolved within this lineage without recent horizontal transfer. However, theeaegene and the LEE appear to have been transferred horizontally within this STEC lineage on several occasions. The reasons for the lack of transfer or maintenance of the LEE in other STEC lineages are not clear and require further study.
Conformational Dependence ofAnaplasma marginaleMajor Surface Protein 5 Surface-Exposed B-Cell Epitopes
Authors: Munodzana Devere , McElwain Terry F. , Knowles Donald P. , Palmer Guy H. 
Published: December 2019

ABSTRACTTheAnaplasma marginaleouter membrane is composed of immunogenic major surface proteins (MSPs) linked both covalently and noncovalently in multimeric complexes (M. C. Vidotto, T. C. McGuire, T. F. McElwain, G. H. Palmer, and D. P. Knowles, Infect. Immun. 62:2940–2946). Consequently, effective induction of antibody against surface-exposed MSP epitopes has been postulated to require maintenance of MSP secondary through quatenary structures. Using MSP5 as a model and the approach of epitope mapping with recombinant expressed full-length and truncated proteins, we demonstrated that the immunodominant surface epitope bound by monoclonal antibody (MAb) ANAF16C1 required disparate amino- and carboxy-terminal regions of MSP5, indicating the conformational dependence of this epitope. The required amino-terminal MSP5 region included the cysteines involved in intramolecular disulfide bonding. The dependence of the immunodominant epitope on disulfide bonding was confirmed by loss of MAb ANAF16C1 binding to MSP5 following disulfide bond reduction and covalent modification of the reduced sulfhydryl groups. The recognition of the MSP5 immunodominant epitope by antibody induced by protective immunization withA. marginaleouter membranes was also conformationally dependent, as shown by the loss of epitope binding following serum adsorption with native but not reduced and denaturedA. marginale. Importantly, the antibody response to all immunodominant MSP5 surface epitopes was restricted to conformationally dependent epitopes, since the binding of polyclonal anti-MSP5 antibody to theA. marginalesurface could be blocked by adsorption with native but not denatured and reduced MSP5. These results confirm the importance of the secondary and tertiary structures of MSP epitopes as immune system targets and support the testing of immunogens which maintain the required conformation.
Antibody-Secreting Cells in the Stomachs of Symptomatic and AsymptomaticHelicobacter pylori-Infected Subjects
Authors: Mattsson A. , Quiding-Järbrink M. , Lönroth H. , Hamlet A. , Ahlstedt I. , Svennerholm A.-M. 
Published: December 2019

ABSTRACTIn this study we analyzed whether infection withHelicobacter pylorigives rise to specific B-cell responses against a number of putative virulence factors ofH. pylori, e.g., urease, flagellin, and different bacterial surface antigens, locally in the gastric mucosa. This was studied in antrum and corpus biopsies collected from 11H. pylori-infected patients with duodenal ulcers, 11 asymptomaticH. pyloricarriers, and 13 noninfected, healthy controls. Mononuclear cells were isolated from the biopsies and assayed for frequencies of total andH. pylori-specific antibody-secreting cells (ASCs) by means of the enzyme-linked immunospot technique. TheH. pylori-infected subjects had remarkably higher frequencies of total immunoglobulin A (IgA)- and IgM-secreting cells than the noninfected subjects, while the frequencies of IgG-secreting cells were virtually the same in the different groups. In addition, most of the infected subjects had IgA ASCs reacting withH. pylorimembrane proteins, flagellin, and urease, while none of the noninfected subjects had any detectableH. pylori-reactive ASCs. Furthermore, half of the infected subjects also had ASCs reacting with aHelicobacter-specific 26-kDa protein, while only a few of them had ASCs reacting with neutrophil-activating protein, the neuraminyllactose-binding hemagglutinin HpaA, or lipopolysaccharides purified from differentH. pyloristrains. The frequencies ofH. pylori-specific ASCs in the antrum and corpus were almost identical, and no differences in either antigen specificity or magnitude of the B-cell response in the stomach could be detected between the ulcer patients and the asymptomaticH. pyloricarriers. This study demonstrates thatH. pyloriinfection induces strong antibody responses in the human gastric mucosa, both in asymptomatic carriers and in duodenal ulcer patients. However, the outcome of infection could not be explained by differences in the local B-cell response to any of the antigens used in this study.
Strain-Dependent Activation of Monocytes and Inflammatory Macrophages by Lipopolysaccharide ofPorphyromonas gingivalis
Authors: Shapira Lior , Champagne Catherine , Van Dyke Thomas E. , Amar Salomon 
Published: December 2019

ABSTRACTPorphyromonas gingivalisis one of the pathogens associated with periodontal diseases, and its lipopolysaccharide (LPS) has been suggested as a possible virulence factor, acting by stimulation of host cells to secrete proinflammatory mediators. However, recent studies have shown thatP. gingivalisLPS inhibited some components of the inflammatory response. The present study was designed to test the hypothesis that there are strain-dependent variations in the ability ofP. gingivalisLPS to elicit the host inflammatory response. By using LPS preparations from two strains ofP. gingivalis, W50 and A7346, the responses of mouse macrophages and human monocytes were evaluated by measuring the secretion of nitric oxide (NO) and tumor necrosis factor alpha (TNF-α). Both direct and indirect (priming) effects were investigated. LPS fromSalmonella typhosawas used as a reference LPS.P. gingivalisA7436 LPS induced lower secreted levels of NO from the tested cells thanS. typhosaLPS but induced similar levels of TNF-α. In contrast, LPS fromP. gingivalisW50 did not induce NO or TNF-α secretion. Preincubation of macrophages with LPS fromS. typhosaorP. gingivalisA7436 prior to stimulation withS. typhosaLPS upregulated NO secretion and downregulated TNF-α secretion, while preincubation withP. gingivalisW50 LPS enhanced both TNF-α and NO secretory responses. These results demonstrate that LPSs derived from different strains ofP. gingivalisvary in their biological activities in vitro. The findings may have an impact on our understanding of the range ofP. gingivalisvirulence in vivo.
Multiple Fimbrial Adhesins Are Required for Full Virulence of
Salmonella typhimurium
in Mice
Authors: van der Velden Adrianus W. M. , Bäumler Andreas J. , Tsolis Renée M. , Heffron Fred 
Published: December 2019

ABSTRACT

Adhesion is an important initial step during bacterial colonization of the intestinal mucosa. However, mutations in the
Salmonella typhimurium
fimbrial operons
lpf
,
pef
, or
fim
only moderately alter mouse virulence. The respective adhesins may thus play only a minor role during infection or
S. typhimurium
may encode alternative virulence factors that can functionally compensate for their loss. To address this question, we constructed mutations in all four known fimbrial operons of
S. typhimurium
:
fim
,
lpf
,
pef
, and
agf
. A mutation in the
agfB
gene resulted in a threefold increase in the oral 50% lethal dose (LD
50
) of
S. typhimurium
for mice. In contrast, an
S. typhimurium
strain carrying mutations in all four fimbrial operons (quadruple mutant) had a 26-fold increased oral LD
50
. The quadruple mutant, but not the
agfB
mutant, was recovered in reduced numbers from murine fecal pellets, suggesting that a reduced ability to colonize the intestinal lumen contributed to its attenuation. These data are evidence for a synergistic action of fimbrial operons during colonization of the mouse intestine and the development of murine typhoid fever.
A Low Concentration of Ethanol Reduces the Chemiluminescence of Human Granulocytes and Monocytes but Not the Tumor Necrosis Factor Alpha Production by Monocytes after Endotoxin Stimulation
Authors: Parlesak Alexandr , Diedrich Jens P. , Schäfer Christian , Bode Christiane 
Published: December 2019

ABSTRACTThe ability of polymorphonuclear neutrophils (PMNs) and monocytes (Mφ) to produce reactive oxygen species (ROS) has been related closely to their potential in the killing of microorganisms. Ethanol has been shown to impair the generation of ROS in these phagocytes after stimulation with some immunogens and to increase the susceptibility of alcohol abusers to infectious diseases. As endotoxemia is common in alcohol abusers, we investigated the effect of ethanol (21.7 mmol/liter) on the luminol-amplified chemiluminescence of PMNs and Mφ after endotoxin stimulation and the release of tumor necrosis factor alpha (TNF-α) from Mφ. Further, the efficiency of ethanol to inactivate chemically generated ROS was tested. Significant stimulation of ROS release occurred at endotoxin concentrations of 1 ng/ml or higher in both PMNs and Mφ. Ethanol significantly suppressed the formation of ROS in both cell types, the decrease being more pronounced in Mφ (−73.8%) than in PMNs (−45.7%). The correlations between endotoxin concentration and the amount of released ROS showed a dose-dependent, sigmoidal course. Concentrations of endotoxin necessary for half-maximum stimulation were nearly identical (6 to 8 ng/ml) in both PMNs and Mφ, independent of the presence of ethanol. In contrast to ROS formation, ethanol had no effect on the amount of TNF-α produced by endotoxin-stimulated Mφ. Ethanol was shown to be unable to decrease the levels of chemically generated ROS under physiological conditions. Therefore, ethanol cannot be assumed to be an “antioxidative” compound but rather seems to modify processes of endotoxin recognition, intracellular signal transduction, or metabolism.
Humoral Immunity toBorrelia burgdorferiN40 Decorin Binding Proteins during Infection of Laboratory Mice
Authors: Feng Sunlian , Hodzic Emir , Stevenson Brian , Barthold Stephen W. 
Published: December 2019

ABSTRACTABorrelia burgdorferiN40 genomic expression library was screened with serum from actively infected mice to identify gene products that elicit protective immunity. A clone that contained a putative bicistronic operon containing two genes that encoded 20- and 22-kDa lipoproteins was identified and sequenced. These genes showed homology with the genes encoding decorin binding proteins DbpB and DbpA, respectively, ofB. burgdorferi297 and B31.N40-dbpADNA hybridized withB. burgdorferiN40 DNA on a single 48-kb linear plasmid. Homologous genes could be amplified under various degrees of stringency by PCR or hybridized by Southern blotting fromB. burgdorferisensu stricto N40 and B31, and fromB. burgdorferisensu lato PBi and 25015, but not PKo. Recombinant N40-DbpB and N40-DbpA were reactive with antibody in serum from infected mice, and serum was more reactive against N40-DbpA than againstB. burgdorferiN40 recombinant P39, OspC, or OspA. Sera from mice infected withB. burgdorferisensu lato strains PKo and PBi were weakly reactive against N40-DbpB and N40-DbpA, and sera from mice infected with 25015 were moderately reactive, compared to sera from mice infected withB. burgdorferiN40. Hyperimmunization of mice with N40-DbpA, but not N40-DbpB, induced protective immunity against syringe challenge with culturedB. burgdorferiN40. DbpA may therefore be one of the antigens responsible for eliciting protective antibody known to exist in serum from infected mice. DNA amplification and serology suggest that DbpB and DbpA are likely to have homologs throughout theB. burgdorferisensu lato family, but they are likely to be heterogeneous.
Liposomes Containing Lipid A Serve as an Adjuvant for Induction of Antibody and Cytotoxic T-Cell Responses against RTS,S Malaria Antigen
Authors: Richards Roberta L. , Rao Mangala , Wassef Nabila M. , Glenn Gregory M. , Rothwell Stephen W. , Alving Carl R. 
Published: December 2019

ABSTRACTEncapsulation of soluble protein antigens in liposomes was previously shown to result in processing of antigen via the major histocompatibility complex class I pathway, as evidenced by costaining of thetrans-Golgi region of murine bone marrow-derived macrophages (BMs) by fluorophore-labeled liposomal antigen and by atrans-Golgi-specific fluorescent lipid. Evidence is presented here that free or liposome-encapsulated RTS,S, a particulate malaria antigen consisting of hepatitis B particles coexpressed with epitopes from thePlasmodium falciparumcircumsporozoite protein, also was localized in thetrans-Golgi after incubation with BMs, suggesting processing by the class I pathway. An in vivo cytotoxic T-lymphocyte (CTL) response was detected, however, only after immunization with RTS,S encapsulated in liposomes containing lipid A and not after immunization with free RTS,S or with RTS,S encapsulated in liposomes lacking lipid A. Therefore, intracellular delivery of antigen containing CTL epitopes to the Golgi of BMs does not necessarily result in a CTL response in vivo unless an additional adjuvant, such as liposomes containing lipid A, is utilized. Encapsulation of RTS,S in liposomes containing monophosphoryl lipid A (MPL) resulted in a dose-dependent enhancement of the NANP-specific immunoglobulin G (IgG) antibody response compared to that of free RTS,S. The IgG1 and IgG2a subclasses predominated after immunization with RTS,S encapsulated in liposomes containing MPL. These results demonstrate that encapsulation of a lipid-containing particulate antigen, such as RTS,S, in liposomes containing lipid A can enhance both humoral and cellular immune responses.
Signal Transduction duringLegionella pneumophilaEntry into Human Monocytes
Authors: Coxon Patricia Y. , Summersgill James T. , Ramirez Julio A. , Miller Richard D. 
Published: December 2019

ABSTRACTLegionella pneumophilacauses Legionnaires’ disease by replication in alveolar macrophages and monocytes. The bacteria are internalized most efficiently by opsonin-dependent, CR3-mediated phagocytosis. This investigation focused on determining the role of actin polymerization and phosphorylation signals in this uptake mechanism. Uptake inhibition assays and confocal microscopic analysis indicated that entry ofL. pneumophilaactivated tyrosine kinase (TK) and protein kinase C (PKC) and induced actin polymerization at the site of bacterial entry. UponL. pneumophilaentry, six major cellular proteins (75, 71, 59, 56, 53, and 52 kDa) were TK phosphorylated in soluble fractions of monocytes, and three of these proteins (52, 53, and 56 kDa) were consistently found in insoluble (i.e., cytoskeletal) fractions of monocytes as well. Tyrosine phosphorylation was suppressed when cells were pretreated with the kinase inhibitor genistein, tyrphostin, or staurosporine. A similar tyrosine-phosphorylated protein pattern was observed with CR3-mediated entry of avirulentL. pneumophila,Escherichia coli, or zymosan into monocytes. This study has shown that PKC and TK signals which activate actin polymerization during the process of phagocytosis are induced uponL. pneumophilaentry. In addition, CR3 receptor-mediated phagocytosis into monocytes may involve tyrosine phosphorylation of similar proteins, regardless of the particle being phagocytosed. Therefore, the tyrosine-induced phosphorylation observed during opsonizedL. pneumophilaentry is not a virulence-associated event.
Goldfish,
Carassius auratus
, a Novel Animal Model for the Study of
Mycobacterium marinum
Pathogenesis
Authors: Talaat Adel M. , Reimschuessel Renate , Wasserman Steven S. , Trucksis Michele 
Published: December 2019

ABSTRACT

We have developed an animal model for studying mycobacterial pathogenesis using
Mycobacterium marinum
and the goldfish,
Carassius auratus
. Goldfish are injected intraperitoneally with doses between 10
2
and 10
9
CFU of
M. marinum
organisms. Depending on the dose of
M. marinum
organisms administered, an acute or chronic disease is produced. The acute disease is characterized by systemic mycobacterial infection, severe peritonitis, tissue necrosis, and a short median survival time. The chronic disease is characterized by granuloma formation in all organs and survival of animals to the end point of the experiment (56 days). Colony counts in organ homogenates showed recovery of mycobacteria from a high percentage of inoculated animals. We believe this well-characterized animal model will be useful for studying mycobacterial pathogenesis.
Secreted Aspartyl Proteinases and Interactions of
Candida albicans
with Human Endothelial Cells
Authors: Ibrahim Ashraf S. , Filler Scott G. , Sanglard Dominique , Edwards John E. , Hube Bernhard 
Published: December 2019

ABSTRACT

The endothelial cell interactions of homozygous null mutants of
Candida albicans
that were deficient in secreted aspartyl proteinase 1 (Sap1), Sap2, or Sap3 were investigated. Only Sap2 was found to contribute to the ability of
C. albicans
to damage endothelial cells and stimulate them to express E-selectin. None of the Saps studied appears to play a role in
C. albicans
adherence to endothelial cells.
Clearance ofShigella flexneriInfection Occurs through a Nitric Oxide-Independent Mechanism
Authors: Way Sing Sing , Goldberg Marcia B. 
Published: December 2019

ABSTRACTNitric oxide (NO) generated by gamma interferon (IFN-γ) activation of macrophages mediates the killing of many intracellular pathogens. IFN-γ is essential to innate resistance toShigella flexneriinfection. We demonstrate that NO is produced followingS. flexneriinfection both in mice and in activated cells in vitro and that while it is able to killS. flexneriin a cell-free system, it is not required for clearance ofS. flexneriin either infected mice or in activated cells in vitro.
Heterogeneous Expression and Release of CD14 by Human Gingival Fibroblasts: Characterization and CD14-Mediated Interleukin-8 Secretion in Response to Lipopolysaccharide
Authors: Sugawara Shunji , Sugiyama Akiko , Nemoto Eiji , Rikiishi Hidemi , Takada Haruhiko 
Published: December 2019

ABSTRACTTo identify the role in periodontal inflammatory diseases of human gingival fibroblasts (HGF), the major constituents of gingival tissue, the expression of CD14, a possible lipopolysaccharide (LPS) receptor, and the release of soluble CD14 (sCD14) by HGF were examined. Among the HGF samples from the nine donors tested, more than 50% of the HGF from five donors expressed CD14 but less than 20% of HGF from the other four donors did so, as determined by flow cytometric analysis. The CD14 expression on the cell surface was correlated with the expression of CD14 mRNA. The HGF and skin and lung fibroblasts tested expressed no CD18, which indicates that fibroblasts do not possess other LPS receptors, such as CD11b/CD18 and CD11c/CD18. The CD14 expression by the HGF was decreased after subculturing and was highest at the confluent stage of culture. The treatment of high-CD14-expressing (CD14high) HGF with phosphatidylinositol-phospholipase C reduced CD14 expression; this result and the increase in a 55-kDa CD14 indicate that the membrane CD14 (mCD14) on the HGF may be a 55-kDa glycosylphosphatidylinositol-anchored protein. CD14highHGF spontaneously released 48- and 57-kDa sCD14. The total release of sCD14 by the HGF was augmented by gamma interferon andEscherichia coliLPS in accordance with the increased expression of mCD14. The CD14highHGF secreted interleukin-8 in response to LPS, and the secretion was completely inhibited by anti-CD14 antibody. These results suggest that (i) HGF consist of populations that are heterogeneous on the basis of different levels of expression of CD14 and (ii) CD14highHGF secrete inflammatory cytokines in response to LPS via CD14.
Role of Alveolar Macrophages in Initiation and Regulation of Inflammation inPseudomonas aeruginosaPneumonia
Authors: Kooguchi Kunihiko , Hashimoto Satoru , Kobayashi Atsuko , Kitamura Yoshihiro , Kudoh Ichidai , Wiener-Kronish Jeanine , Sawa Teiji 
Published: December 2019

ABSTRACTTo evaluate the role of alveolar macrophages (AMs) in acutePseudomonas aeruginosapneumonia in mice, AMs were depleted by aerosol inhalation of liposomes containing clodronate disodium. AM-depleted mice were then intratracheally infected with 5 × 105CFU ofP. aeruginosa. In addition to monitoring neutrophil recruitment and chemokine releases, lung injury was evaluated soon after infection (8 h) and at a later time (48 h). At 8 h, depletion of AMs reduced neutrophil recruitment, chemokine release, and lung injury. At 48 h, however, depletion of AMs decreased bacterial clearance and resulted in delayed movement of neutrophils from the site of inflammation with aggravated lung injury. With instillation of 5 × 107CFU of bacteria, AM-depleted mice showed low mortality within 24 h of infection but high mortality at a later time, in contrast to non-AM-depleted mice. These results demonstrate that depletion of AMs has beneficial early effects but deleterious late effects on lung injury and survival in cases ofP. aeruginosapneumonia.
Intestinal Immune Responses to an Inactivated Oral Enterotoxigenic
Escherichia coli
Vaccine and Associated Immunoglobulin A Responses in Blood
Authors: Åhrén Christina , Jertborn Marianne , Svennerholm Ann-Mari 
Published: December 2019

ABSTRACT

An inactivated oral enterotoxigenic
Escherichia coli
(ETEC) vaccine against ETEC diarrhea was given to 25 adult Swedish volunteers. The vaccine consisted of formalin-killed
E. coli
bacteria expressing the most common colonization factor antigens (CFAs), i.e., CFA/I, -II, and -IV, and recombinantly produced cholera B subunit (CTB). Immunoglobulin A (IgA) antibody responses in intestinal lavage fluid to CTB and CFAs were determined and compared with corresponding responses in stool extracts and serum as well as with IgA antibody-secreting cell (ASC) responses in peripheral blood. Two doses of vaccine induced significant IgA responses to the different CFAs in lavage fluid in 61 to 87% of the vaccinees and in stool in 38 to 81% of them. The most frequent responses were seen against CFA/I. The magnitudes of the antibody responses against CTB and CFA/I in stool correlated significantly (CTB,
P
< 0.01; CFA/I,
P
< 0.05) with those in intestinal lavage. Intestinal lavage responses against CFAs were best reflected by the ASC responses, with the sensitivity of the ASC assay being 80 to 85%, followed by stool (sensitivity of 50 to 88%) and serum antibody (sensitivity of 7 to 65%) analyses. CTB-specific immune responses were seen in >90% of the vaccinees in all assays.