bluuebunny/crossref_metadata_2025_split huggingface dataset:
Active and Passive Immunity againstBorrelia burgdorferiDecorin Binding Protein A (DbpA) Protects against Infection
Authors: Hanson Mark S. , Cassatt David R. , Guo Betty P. , Patel Nita K. , McCarthy Michael P. , Dorward David W. , Höök Magnus 
Published: December 2019

ABSTRACTBorrelia burgdorferi, the spirochete that causes Lyme disease, binds decorin, a collagen-associated extracellular matrix proteoglycan found in the skin (the site of entry for the spirochete) and in many other tissues. Two borrelial adhesins that recognize this proteoglycan, decorin binding proteins A and B (DbpA and DbpB, respectively), have recently been identified. Infection of mice by low-doseB. burgdorferichallenge elicited antibodies against DbpA and DbpB that were sustained at high levels, suggesting that these antigens are expressed in vivo. Scanning immunoelectron microscopy showed that DbpA was surface accessible on intact borreliae. Passive administration of DbpA antiserum protected mice from infection following challenge with heterologousB. burgdorferisensu stricto isolates, even when serum administration was delayed for up to 4 days after challenge. DbpA is the first antigen target identified that is capable of mediating immune resolution of early, localizedB. burgdorferiinfections. DbpA immunization also protected mice fromB. burgdorferichallenge; DbpB immunization was much less effective. DbpA antiserum inhibited in vitro growth of manyB. burgdorferisensu lato isolates of diverse geographic, phylogenetic, and clinical origins. In combination, these findings support a role for DbpA in the immunoprophylaxis of Lyme disease and suggest that DbpA vaccines have the potential to eliminate early-stageB. burgdorferiinfections.
Production of Proinflammatory Cytokines and Inflammatory Mediators in Human Intestinal Epithelial Cells after Invasion by
Trichinella spiralis
Authors: Li Chris K. F. , Seth Rashmi , Gray Trevor , Bayston Roger , Mahida Yashwant R. , Wakelin Derek 
Published: December 2019

ABSTRACT

Epithelial cells are the first point of host contact for invasive intestinal pathogens and may initiate mucosal inflammatory responses via production of proinflammatory cytokines and mediators. The aim of the present study was to investigate in vitro the initial invasion of a parasitic nematode (
Trichinella spiralis
), to measure the early production of specific epithelial cytokines and inflammatory mediators after invasion, and to compare these responses with those to invasive bacteria. Monolayers of human colonic epithelial cell lines (HT29, T84, and Caco-2) were infected by
T. spiralis
or
Listeria monocytogenes
. Bile-activated infective larvae of
T. spiralis
invaded and migrated into the epithelial cell monolayers, leaving trails of dead cells. Transmission electron microscopy studies of damaged cells along the trail showed a progressive increase in size, disruption of cell membranes, loss or dilution of cytoplasmic proteins, and swelling of mitochondria and nuclei. However, no nuclear fragmentation was observed. With reverse transcription-PCR and an enzyme-linked oligonucleotide chemiluminescent assay, mRNA transcripts of interleukin-1β (IL-1β), IL-8, and epithelial neutrophil-activating peptide 78 were shown to increase in epithelial cells invaded by
T. spiralis
or
L. monocytogenes
, but only
L. monocytogenes
elicited increased inducible nitric oxide synthase (iNOS) mRNA. No increase in tumor necrosis factor alpha or transforming growth factor β mRNA was seen after
T. spiralis
invasion. Increased levels of IL-8 were also released from the basolateral surfaces of infected monolayers as detected by sandwich enzyme-linked immunosorbent assay. Induction and secretion of proinflammatory cytokines in epithelial cells after nematode or bacterial invasion may initiate the acute inflammatory response of the small intestine. The upregulation of iNOS in bacterial infections may contribute to mucosal defense and may also be associated with subsequent cell death, whereas different mechanisms appear to operate after nematode invasion.
TheLegionella pneumophila icmGCDJBFGenes Are Required for Killing of Human Macrophages
Authors: Purcell Mary , Shuman Howard A. 
Published: December 2019

ABSTRACTPreviously, a collection of mutants ofLegionella pneumophilathat had lost the ability to multiply within and kill human macrophages was generated by Tn903dIIlacZ transposon mutagenesis and classified into DNA hybridization groups. A subset of these mutants was complemented by a plasmid, pMW100, containing a 13.5-kb genomic DNA insert. This plasmid restored the ability to multiply within and produce cytopathic effects on human macrophages to members of DNA hybridization groups II, IV, VI, and XVII. A region of the genomic insert of pMW100 was sequenced, and eight potential genes were identified and namedicmE,icmG,icmC,icmD,icmJ,icmB,icmF, andtphA. None of the genes encode potential protein products with significant homology to previously characterized proteins, except fortphA, whose product has significant homology to a family of metabolite/H+symport proteins from gram-negative bacteria. The positions of the Tn903dIIlacZ insertions within the genes were determined by nucleotide sequencing. No Tn903dIIlacZ insertions mapped toicmG,icmJ, ortphA; therefore, these loci were mutated to test whether they were required for macrophage killing. Complementation analysis was used to evaluate the roles of the potential gene products and provide information on the organization of transcriptional units within the region. The results indicate that all identified open reading frames excepttphAare required for killing of human macrophages.
Identification and Characterization of Heparin Binding Regions of the Fim2 Subunit ofBordetella pertussis
Authors: Geuijen Cecile A. W. , Willems Rob J. L. , Hoogerhout Peter , Puijk Wouter C. , Meloen Rob H. , Mooi Frits R. 
Published: December 2019

ABSTRACTBordetella pertussisfimbriae bind to sulfated sugars such as heparin through the major subunit Fim2. The Fim2 subunit contains two regions, designated H1 and H2, which show sequence similarity with heparin binding regions of fibronectin, and the role of these regions in heparin binding was investigated with maltose binding protein (MBP)-Fim2 fusion proteins. Deletion derivatives of MBP-Fim2 showed that both regions are important for binding to heparin. The role of H2 in heparin binding was confirmed by site-directed mutagenesis in which basic amino acids were replaced by alanine. These studies revealed that Lys-186 and Lys-187 are important for heparin binding of MBP-Fim2, whereas Arg-179 is not required. Peptides derived from H1 and H2 (pepH1 and pepH2) also showed heparin binding activity. Using a series of peptides, in each of which a different basic amino acid was substituted for alanine, we demonstrated that the structural requirements for heparin binding differ significantly among pepH1 and pepH2 peptides. A Pepscan analysis of Fim2 revealed regions outside H1 and H2 which bind heparin and showed that not only basic amino acids but also tyrosines may be important for binding to sulfated sugars. A comparison of the heparin binding regions of Fim2 with homologous regions of Fim3 and FimX, two closely related but antigenically distinct fimbrial subunits, showed that basic amino acids and tyrosines are generally conserved. The major heparin binding regions identified in Fim2 are part of epitopes recognized by human antibodies, suggesting that the heparin binding regions are exposed at the fimbrial surface and are immunodominant. SinceB. pertussisfimbriae show weak serological cross-reactivity, the differences in primary structure in the heparin binding regions of Fim2, Fim3, and FimX may affect antibody binding but not heparin binding, allowing the bacteria to evade antibody-mediated immunity by switching the fimbrial gene expressed.
Soluble CD14 Activates Monocytic Cells Independently of Lipopolysaccharide
Authors: Landmann Regine , Link Susanne , Sansano Sebastiano , Rajacic Zarko , Zimmerli Werner 
Published: December 2019

ABSTRACTThe glycoprotein CD14 acts as a receptor for lipopolysaccharide (LPS), either when anchored in the myeloid cell membrane (mCD14) or as a soluble molecule (sCD14) in serum. sCD14-LPS complexes activate cells devoid of mCD14. However, the role of sCD14 independent of LPS is unknown. Therefore, the effect of sCD14 on monocyte functions was investigated in the monocytic cell lines THP1 and Mono Mac 6 and in fresh human monocytes. Under serum-free conditions, endotoxin-free human recombinant sCD141–348(rsCD141–348) induced tumor necrosis factor alpha (TNF-α). The TNF-α effect was stronger in THP1 cells than in Mono Mac 6 cells or monocytes. It was dose dependent, with a maximum at 1 μg/ml, and time dependent, with a maximum after 2 h. sCD14 purified from urine had the same cytokine-activating capacity. In contrast, C-terminally truncated rsCD141–152was inactive. The rsCD14 effect was not due to LPS contamination, since it was resistant to polymyxin and lipid IVa but sensitive to heat and trypsin. The rsCD14-induced cytokine induction was blocked by preincubation of rsCD14 with a monoclonal anti-CD14 antibody that did not recognize the LPS-binding site. Release of the TNF-α disappeared upon pretreatment of rsCD14 in 50% plasma or in complete, heat-inactivated or sCD14-depleted serum. Moreover, cytokine production was no longer observed when rsCD14 was pretreated with thrombocytes. The thrombocyte effect was dose and time dependent. In conclusion, sCD14 is able to activate myeloid cells, and the effect is prevented by the presence of plasma, serum, or thrombocytes.
Effects of the Antioxidant α-Lipoic Acid on Human Umbilical Vein Endothelial Cells Infected with
Rickettsia rickettsii
Authors: Eremeeva Marina E. , Silverman David J. 
Published: December 2019

ABSTRACT

Rickettsia rickettsii
infection of endothelial cells is manifested in very distinctive changes in cell morphology, consisting of extensive dilatation of the membranes of the endoplasmic reticulum and outer nuclear envelope and blebbing of the plasma membrane, as seen by transmission electron microscopy (D. J. Silverman, Infect. Immun. 44:545–553, 1984). These changes in cellular architecture are thought to be due to oxidant-mediated cell injury, since their occurrence correlates with dramatic alterations in cellular metabolism, particularly with regard to antioxidant systems. In this study, it was shown that
R. rickettsii
infection of human umbilical vein endothelial cells resulted in a significant depletion of intracellular reduced glutathione (thiol) content at 72 and 96 h and decreased glutathione peroxidase activity at 72 h postinfection. Infected cells displayed a dramatic increase in the concentration of intracellular peroxides by 72 h. Supplementation of the cell culture medium with 100, 200, or 500 μM α-lipoic acid, a metabolic antioxidant, after inoculation with
R. rickettsii
restored the intracellular levels of thiols and glutathione peroxidase and reduced the intracellular peroxide levels in infected cells. These effects were dose dependent. Treated infected monolayers maintained better viability at 96 h after inoculation with
R. rickettsii
than did untreated infected cells. Moreover, supplementation of the cell culture medium with 100 μM α-lipoic acid for 72 h after infection prevented the occurrence of morphological changes in the infected cells. The presence of 100 or 200 μM α-lipoic acid did not influence rickettsial growth in endothelial cells, nor did it affect the ability of
R. rickettsii
to form lytic plaques in Vero cells. Treatment with 500 μM α-lipoic acid decreased by 50% both the number and size of lytic plaques in Vero cells, and it also decreased the recovery of viable rickettsiae from endothelial cells. However, under all treatment conditions, a significant number of rickettsiae could be detected microscopically. Furthermore, the rickettsiae apparently retained their capacity for intracellular movement, since they possessed long polymerized actin tails after 72 and 96 h of treatment regardless of the concentration of α-lipoic acid used. Since α-lipoic acid does not seem to exhibit direct antirickettsial activity except with long-term exposure at very high concentrations, the mechanism of its protective activity for endothelial cells infected with rickettsiae may involve complex changes in cellular metabolism that only indirectly affect rickettsiae.
Protection against Lethal Murine Coccidioidomycosis by a Soluble Vaccine from Spherules
Authors: Zimmermann C. Roger , Johnson Suzanne M. , Martens Gregory W. , White Andrew G. , Zimmer Barbara L. , Pappagianis Demosthenes 
Published: December 2019

ABSTRACTThe formaldehyde-killed, whole-spherule vaccine, which is protective against lethal challenge of laboratory animals withCoccidioides immitis, was fractionated. It yielded a soluble, multicomponent, subcellular fraction termed the 27K vaccine. This vaccine, when it was accompanied by adjuvant, protected mice against lethal intranasal and intravenous challenge withC. immitis.
Chlamydia trachomatisInfection of Human Mesothelial Cells Alters Proinflammatory, Procoagulant, and Fibrinolytic Responses
Authors: van Westreenen Mireille , Pronk Apollo , Diepersloot Rob J. A. , de Groot Philip G. , Leguit Piet 
Published: December 2019

ABSTRACTIn this study we demonstrate the capability ofChlamydia trachomatisto infect cultured human mesothelial cell (MC) monolayers and to induce the production of the proinflammatory cytokines interleukin 1β (IL-1β) and IL-8. Seventy-two hours after initial infection, both the procoagulant activity of MC and the activity of the fibrinolytic inhibitor (plasminogen activator inhibitor 1) in the supernatants were enhanced. These findings support the hypothesis that provoked proinflammatory responses contribute to the development of complications after chlamydial infection.
Clot Formation by Group A Streptococci
Authors: Donabedian Haig , Boyle Michael D. P. 
Published: December 2019

ABSTRACT

Group A streptococci of several different M serotypes can cause human plasma to clot in nutrient-poor media. Addition of glucose to the medium prevents clot formation. Once formed, clots are stable for several days and can be lysed on addition of exogenous streptokinase or urokinase. Clot lysis can also be achieved by addition of glucose to a clot containing wild-type group A streptococci but not clots containing an isogenic mutant in which the
ska
gene was inactivated.
Lipoprotein(a) Inhibits Lipopolysaccharide-Induced Tumor Necrosis Factor Alpha Production by Human Mononuclear Cells
Authors: Netea Mihai G. , de Bont Natasja , Demacker Pierre N. M. , Kullberg Bart Jan , Jacobs Liesbeth E. H. , Verver-Jansen Trees J. G. , Stalenhoef Anton F. H. , Van der Meer Jos W. M. 
Published: December 2019

ABSTRACTLipoproteins can bind lipopolysaccharide (LPS) and decrease LPS-stimulated cytokine production. Lipoprotein(a) [Lp(a)] was as potent as low-density lipoproteins (LDL) in inhibiting LPS-stimulated tumor necrosis factor synthesis by human mononuclear cells. The kinetics of LPS inhibition by Lp(a) was similar to that of LDL. This suggests that circulating Lp(a) may be an important factor determining the amplitude of the response to LPS in humans.
Roles for Tumor Necrosis Factor and Gamma Interferon in Resistance to Enteric Listeriosis
Authors: Beretich Guy R. , Carter Philip B. , Havell Edward A. 
Published: December 2019

ABSTRACTListeria monocytogenesnormally infects the host by translocating from the intestinal lumen. Experiments were carried out to determine if, when, and where tumor necrosis factor (TNF) and gamma interferon (IFN-γ) function in antibacterial resistance during enteric listeriosis. Groups of normal mice and severe combined immunodeficient (SCID) mice were injected with neutralizing monoclonal antibodies (MAb) specific for each cytokine and then inoculated intragastrically withL. monocytogenes. The course of infection was monitored by enumerating listeriae in gut-associated lymphoid tissues, livers, and spleens. By the third day of infection, bacterial numbers in infected tissues and organs were greatly exacerbated in all mice treated with anti-TNF MAb, whereas bacterial numbers in the organs of mice treated with anti-IFN-γ MAb did not differ from those present in the respective organs of control mice. However, by the fifth day of infection, bacterial numbers in the organs of anti-IFN-γ MAb-treated normal mice and SCID mice were much greater than in the corresponding organs of control mice. Experiments withListeria-immune mice revealed that TNF and IFN-γ are involved in the expression of anti-Listeriamemory immunity; however, it was also found that the anti-IFN-γ MAb was relatively ineffective in inhibiting the expression of anti-Listeriaimmunity, whereas a polyclonal anti-IFN-γ was quite effective.
Mapping and Identification of the Major Cell Wall-Associated Components of
Mycobacterium leprae
Authors: M. Marques Maria Angela , Chitale Sadhana , Brennan Patrick J. , Pessolani Maria Cristina V. 
Published: December 2019

ABSTRACT

Mycobacterium leprae
, an obligate intracellular pathogen, can be derived only from host tissue and thus affords the opportunity to study in vivo-expressed products responsible for the particular pathogenesis of leprosy. Despite considerable progress in the characterization of the proteins and secondary gene products of
M. leprae
, there is little information on the nature of the proteins associated with the cell envelope.
M. leprae
has been fractionated into its major subcellular components, cell wall, cytoplasmic membrane, and soluble cytosol. A number of biochemical markers, including diaminopimelic acid content, monosaccharide composition, mycolic acid, and glycolipid distribution, were applied to their characterization, and two-dimensional gel electrophoresis was used to map the component proteins. A total of 391 major proteins spots were resolved, and 8 proteins were identified based on their reactivity to a panel of monoclonal antibodies and/or relative pI size. Microsequencing of six protein spots present in the cell wall fraction allowed identification of new proteins, including the protein elongation factor EF-Tu and a homolog for the
Mycobacterium tuberculosis
MtrA response regulator. These results, together with previous studies, contribute to the progressive knowledge of the composition of the in vivo-expressed proteins of
M. leprae.
Borrelia burgdorferi
Erp Proteins Are Immunogenic in Mammals Infected by Tick Bite, and Their Synthesis Is Inducible in Cultured Bacteria
Authors: Stevenson Brian , Bono James L. , Schwan Tom G. , Rosa Patricia 
Published: December 2019

ABSTRACT

Borrelia burgdorferi
, the causative agent of Lyme disease, can contain multiple genes encoding different members of the Erp lipoprotein family. Some arthropod-borne bacteria increase the synthesis of proteins required for transmission or mammalian infection when cultures are shifted from cool, ambient air temperature to a warmer, blood temperature. We found that all of the
erp
genes known to be encoded by infectious isolate B31 were differentially expressed in culture after a change in temperature, with greater amounts of message being produced by bacteria shifted from 23 to 35°C than in those maintained at 23°C. Mice infected with B31 by tick bite produced antibodies that recognized each of the Erp proteins within 4 weeks of infection, suggesting that the Erp proteins are produced by the bacteria during the early stages of mammalian infection and may play roles in transmission from ticks to mammals. Several of the B31 Erp proteins were also recognized by antibodies from patients with Lyme disease and may prove to be useful antigens for diagnostic testing or as components of a protective vaccine.
Effects of Granulocyte-Macrophage Colony-Stimulating Factor and Tumor Necrosis Factor Alpha onTrypanosoma cruziTrypomastigotes
Authors: Fontt Elizabeth Olivares , De Baetselier Patrick , Heirman Carlo , Thielemans Kris , Lucas Ralph , Vray Bernard 
Published: December 2019

ABSTRACTWe have previously shown that the addition of exogenous granulocyte-macrophage colony-stimulating factor (GM-CSF) to nonactivated mouse peritoneal macrophages (MPM) limitsTrypanosoma cruziinfections in vitro (E. Olivares Fontt and B. Vray, Parasite Immunol. 17:135–141, 1995). Lower levels of infection were correlated with a higher level of production of tumor necrosis factor alpha (TNF-α) in the absence of nitric oxide (NO) release. These data suggested that GM-CSF and/or TNF-α might have a direct parasitocidal effect onT. cruzitrypomastigotes, independently of NO release. To address this question,T. cruzitrypomastigotes were treated with recombinant murine GM-CSF (rmGM-CSF), recombinant murine TNF-α (rmTNF-α), or both cytokines in a cell-free system. Treatment with rmGM-CSF but not rmTNF-α caused morphological changes in the parasites, and most became spherical after 7 h of incubation. Both cytokines exerted a cytolytic activity on the trypomastigotes, yet the trypanolytic activity of rmTNF-α was more effective than that of rmGM-CSF. Viable rmGM-CSF- and rmTNF-α-treated parasites were less able to infect MPM than untreated parasites, and this reduction in infectivity was greatest for rmGM-CSF. Treatments with both cytokines resulted in more lysis and almost complete inhibition of infection. The direct parasitocidal activity of rmTNF-α was inhibited by carbohydrates and monoclonal antibodies specific for the lectin-like domain of TNF-α. Collectively, these results suggest that cytokines such as GM-CSF and TNF-α may directly control the level ofT. cruzitrypomastigotes at least in vitro and so could determine the outcome of infection in vivo.
Effects of Toxin A fromClostridium difficileon Mast Cell Activation and Survival
Authors: Calderón Gloria M. , Torres-López Javier , Lin Tong-Jun , Chavez Bibiana , Hernández Manuel , Muñoz Onofre , Befus A. Dean , Enciso J. Antonio 
Published: December 2019

ABSTRACTToxins A and B fromClostridium difficileare the main cause of antibiotic-associated diarrhea and pseudomembranous colitis. They cause fluid accumulation, necrosis, and a strong inflammatory response when inoculated in intestinal loops. Since mast cells are a rich source of inflammatory mediators, abundant in the gut, and known to be involved inC. difficile-induced enteritis, we studied the in vitro effect of toxin A on isolated mast cells. Normal rats sensitized by infection withNippostrongilus brasiliensiswere used to isolate peritoneal mast cells (PMC). PMC from naive rats were stimulated with calcium ionophore A23187 as a model of antigen-independent activation, and PMC from sensitized rats were stimulated withN. brasiliensisantigens to study immunoglobulin E-dependent mast cell activation. After 4 h, toxin A did not induce release of nitric oxide or histamine in naive PMC. However, 10 ng of toxin per ml caused a significant release of tumor necrosis factor alpha (TNF-α). In contrast, 1 μg of toxin per ml inhibited antigen or A23187-induced histamine release by PMC. Toxin A at 1 μg/ml for 4 h caused disruption of actin which aggregated in the cytoplasm and around the nucleus. After 24 h, chromatin condensation, cytoplasmic blebbing, and apoptotic-like vesicles were observed; DNA fragmentation was documented also. These results suggest that mast cells may participate in the initial inflammatory response toC. difficileinfection by releasing TNF-α upon interaction with toxin A. However, longer exposure to toxin A affects the release of inflammatory mediators, perhaps because of the alteration of the cytoskeleton and induction of apoptosis. The impaired functions and survival of mast cells byC. difficiletoxin A could hamper the capacity of these cells to counteract the infection, thus prolonging the pathogenic effects ofC. difficiletoxins.