bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genomic Subtractive Hybridization and Selective Capture of Transcribed Sequences Identify a NovelSalmonella typhimuriumFimbrial Operon and Putative Transcriptional Regulator That Are Absent from theSalmonella typhiGenome
Authors: Morrow Brian J. , Graham James E. , Curtiss Roy 
Published: December 2019

ABSTRACTSalmonella typhi, the etiologic agent of typhoid fever, is adapted to the human host and unable to infect nonprimate species. The genetic basis for host specificity inS. typhiis unknown. The avirulence ofS. typhiin animal hosts may result from a lack of genes present in the broad-host-range pathogenSalmonella typhimurium. Genomic subtractive hybridization was successfully employed to isolateS. typhimuriumgenomic sequences which are absent from theS. typhigenome. These genomic subtracted sequences mapped to 17 regions distributed throughout theS. typhimuriumchromosome. A positive cDNA selection method was then used to identify subtracted sequences which were transcribed byS. typhimuriumfollowing macrophage phagocytosis. A novel putative transcriptional regulator of the LysR family was identified as transcribed by intramacrophageS. typhimurium. This putative transcriptional regulator was absent from the genomes of the human-adapted serovarsS. typhiandSalmonella paratyphiA. Mutations within this gene did not alter the level ofS. typhimuriumsurvival within macrophages or virulence within mice. A subtracted genomic fragment derived from the ferrichrome operon also hybridized to the intramacrophage cDNA. Nucleotide sequence analysis ofS. typhimuriumandS. typhichromosomal sequences flanking the ferrichrome operon identified a novelS. typhimuriumfimbrial operon with a high level of similarity to sequences encodingProteus mirabilismannose-resistant fimbriae. The novel fimbrial operon was absent from theS. typhigenome. The absence of specific genes may have allowedS. typhito evolve as a highly invasive, systemic human pathogen.
Exposure ofN-Formyl-l-Methionyl-l-Leucyl-l-Phenylalanine-Activated Human Neutrophils to thePseudomonas aeruginosa-Derived Pigment 1-Hydroxyphenazine Is Associated with Impaired Calcium Efflux and Potentiation of Primary Granule Enzyme Release
Authors: Ramafi Grace , Anderson Ronald , Theron Annette , Feldman Charles , Taylor Graham W. , Wilson Robert , Cole Peter J. 
Published: December 2019

ABSTRACTThe effects of pathologically relevant concentrations (0.38 to 12.5 μM) of the proinflammatory,Pseudomonas aeruginosa-derived pigment 1-hydroxyphenazine (1-hp) on Ca2+metabolism and intracellular cyclic AMP (cAMP) inN-formyl-l-methionyl-l-leucyl-l-phenylalanine (FMLP; 1 μM)-activated human neutrophils, as well as on the release of myeloperoxidase (MPO) and elastase from these cells, have been investigated in vitro. Ca2+fluxes were measured by the combination of a fura-2/AM-based spectrofluorimetric method and radiometric procedures, which together enable distinction between net efflux and influx of the cation, while radioimmunoassay and colorimetric methods were used to measure cAMP and granule enzymes, respectively. Coincubation of neutrophils with 1-hp did not affect intracellular cAMP levels or the FMLP-activated release of Ca2+from intracellular stores but did retard the subsequent decline in the chemoattractant-induced increase in the concentration of cytosolic free Ca2+. These effects of 1-hp on the clearance of Ca2+from the cytosol of activated neutrophils were associated with decreased efflux of the cation from the cells and increased release of MPO and elastase, while the delayed store-operated influx of the cation into the cells was unaffected by the pigment. The plasma membrane Ca2+-ATPase rather than a Na+-Ca2+exchanger appeared to be the primary target of 1-hp. These observations suggest that the proinflammatory interactions of 1-hp with activated human neutrophils are a consequence of interference with the efflux of cytosolic Ca2+from these cells.
Streptococcus parasanguis pepOEncodes an Endopeptidase with Structure and Activity Similar to Those of Enzymes That Modulate Peptide Receptor Signaling in Eukaryotic Cells
Authors: Froeliger Eunice H. , Oetjen Joyce , Bond Jeffrey P. , Fives-Taylor Paula 
Published: December 2019

ABSTRACTStudies in our laboratory have identified two fimbria-associated adhesins, FimA and Fap1, ofStreptococcus parasanguisFW213. In this study, we isolated and sequenced DNA fragments linked tofimAto determine if they contained additional factors associated with adherence, virulence, or survival in the host. An open reading frame just upstream and divergently transcribed from thefimAoperon was identified and namedpepO. Northern hybridization indicated thatpepOis transcribed as a monocistronic message.pepOencodes a predicted 631-amino-acid protein with a molecular mass of approximately 70.6 kDa. PepO contains the essential motif HEXXH, typical of many zinc-dependent metalloproteases and metallopeptidases. PepO has significant sequence identity to mammalian metallopeptidases, including endothelin-converting enzyme, which converts a potent vasoconstrictor into its active form, and neutral endopeptidase (NEP), which is involved in terminating the activity of opioid peptides. The opioid peptide metenkephalin is a natural substrate of NEP. Cell extracts of FW213 cleaved metenkephalin at the same site as does NEP, while an extract from an insertionally inactivatedpepOmutant did not. These results indicate that FW213pepOencodes an enzyme with activity similar to that of known mammalian endopeptidases. Phylogenetic analysis of PepO and its homologues suggests lateral genetic exchange between bacteria and eukaryotes.
CD40-CD40 Ligand Interactions Augment Survival of Normal Mice, but Not CD40 Ligand Knockout Mice, Challenged Orally withSalmonella dublin
Authors: Marriott Ian , Thomas Elaine K. , Bost Kenneth L. 
Published: December 2019

ABSTRACTInteractions between CD40 expressed on macrophages and CD40 ligand expressed on T lymphocytes can be an important signal for optimal macrophage activation. Previous studies have demonstrated that the optimal response against certain intracellular pathogens (e.g.,CrytosporidiumandLeishmaniaspp.) by macrophages requires CD40-CD40 ligand interactions. However, this finding is not universal, since two recent reports utilizing CD40 knockout mice have shown no such contribution to the protective immune response againstMycobacterium tuberculosisorHistoplasma capsulatum. We demonstrate here that CD40-CD40 ligand interactions are significant events in the protective response against the intracellular pathogenSalmonella dublinin normal mice but not for animals genetically deficient in CD40 ligand expression. Treating BALB/c mice exogenously with a CD40 agonist (i.e., soluble trimeric CD40 ligand) increased resistance against a lethal, orally administered dose ofS. dublin. Conversely, in vivo administration of a monoclonal antibody against CD40 ligand to block endogenous CD40-CD40 ligand interactions resulted in a decreased resistance to salmonellosis. In contrast, CD40 ligand knockout mice demonstrated no increased susceptibility to salmonellosis. In vitro treatment ofSalmonella-infected macrophages from BALB/c mice with soluble trimeric CD40 ligand resulted in an elevated production of interleukin 12p70 by these cells, suggesting a mechanism whereby CD40-CD40 ligand interactions might enhance protective immune responses to this pathogen. Taken together, these studies strongly suggest that CD40-CD40 ligand interactions in normal mice play an important protective role in immune responses against the gram-negative, intracellular pathogenS. dublin.
Expression of Herpes Simplex Virus Thymidine Kinase inToxoplasma gondiiAttenuates Tachyzoite Virulence in Mice
Authors: Radke Jay R. , White Michael W. 
Published: December 2019

ABSTRACTWe tested the virulence in mice ofToxoplasma gondiiRH strain tachyzoites containing various copies of the chloramphenicol acetyl transferase-herpes simplex virus thymidine kinase fusion sequence (CAT-HSTK). Tachyzoite isolates containing ≥five copies of the fusion sequence were not lethal to female CD-1 outbred or BALB/c inbred mice, at doses up to 106parasites, while the parental RH strain caused 100% mortality within 2 weeks at doses as low as 10 parasites. Mice infected with CTK11, an isolate containing five copies of the fusion sequence, showed no overt symptoms of disease and were protected from lethal challenge with the parental RH strain. The CTK11 isolate showed no difference in growth rate, the rate of host cell invasion, or extracellular viability in cell culture compared with parental RH parasites, demonstrating that the CAT-HSTK fusion protein does not affect the normal viability of this isolate. B11, B11C, and D1 isolates contained one or two copies of the CAT-HSTK coding sequence, were not sensitive to thymidine in cell culture, and caused 100% mortality in CD-1 outbred mice in <12 days. A fourth isolate, D1C, contained seven copies of the CAT-HSTK fusion sequence and was sensitive to exogenous thymidine (50% inhibitory concentration = 5.5 μM). Mice infected with D1C showed no symptoms of disease and survived beyond 90 days, thus correlating increased CAT-HSTK gene copies with thymidine sensitivity in cell culture and attenuated virulence in mice. BALB/c mice containing a targeted disruption of the gamma interferon gene (gko) were also susceptible to infection with CTK11 parasites but could be rescued by administration of subcutaneous thymidine once each day for 5 or 10 days following infection. These results suggest that the attenuation of CAT-HSTK+isolates in mice is directly due to active thymidine kinase that likely alters the pyrimidine biosynthetic pathway in these parasites.
Analysis of Receptor for
Vibrio cholerae
El Tor Hemolysin with a Monoclonal Antibody That Recognizes Glycophorin B of Human Erythrocyte Membrane
Authors: Zhang Dongyan , Takahashi Junko , Seno Taiko , Tani Yoshihiko , Honda Takeshi 
Published: December 2019

ABSTRACT

El Tor hemolysin (ETH), a pore-forming toxin secreted by
Vibrio cholerae
O1 biotype El Tor and most
Vibrio cholerae
non-O1 isolates, is able to lyse erythrocytes and other mammalian cells. To study the receptor for this toxin or the related molecule(s) on erythrocyte, we first isolated a monoclonal antibody, B1, against human erythrocyte membrane, which not only blocks the binding of ETH to human erythrocyte but also inhibits the hemolytic activity of ETH. Biochemical characterization and immunoblotting revealed that this antibody recognized an epitope on the extracellular domain of glycophorin B, a sialoglycoprotein of erythrocyte membrane. Erythrocytes lacking glycophorin B but not glycophorin A were less sensitive to the toxin than were normal human erythrocytes. These results indicate that glycophorin B is a receptor for ETH or at least an associated molecule of the receptor for ETH on human erythrocytes.
Virulence Role of V Antigen ofYersinia pestisat the Bacterial Surface
Authors: Fields Kenneth A. , Nilles Matthew L. , Cowan Clarissa , Straley Susan C. 
Published: December 2019

ABSTRACTYersinia pestis, the etiologic agent of plague, secretes a set of environmentally regulated, plasmid pCD1-encoded virulence proteins termed Yops and V antigen (LcrV) by a type III secretion mechanism (Ysc). LcrV is a multifunctional protein that has been shown to act at the level of secretion control by binding the Ysc inner-gate protein LcrG and to modulate the host immune response by altering cytokine production. LcrV also is essential for the unidirectional targeting of Yops to the cytosol of infected eukaryotic cells. In this study, we constructed an in-frame deletion withinlcrG(ΔlcrG3) to further analyze the requirement of LcrV in Yop targeting. We confirmed the essentiality of LcrV and found that LcrG may have a facilitative role, perhaps by promoting efficient secretion of LcrV. We also constructed mutants oflcrVexpressing LcrV truncated at the N or C terminus. Both the N and C termini of LcrV were required for the secretion of LcrV into the medium and targeting of Yops. LcrV was detected in punctate zones on the surface of fixedY. pestisby laser-scanning confocal microscopy, and this localization required a functional Ysc. However, the truncated LcrV proteins were not found on the bacterial surface. Finally, we tested the ability of LcrV-specific Fab antibody fragments or full-length antibody to interfere with Yop targeting and found no interference, even though this antibody protects mice against plague. These results indicate that LcrV may function in Yop targeting at the extracellular surface of yersiniae and that the protective efficacy of LcrV-specific antibodies can be manifested without blocking Yop targeting.
Conformational Nature of the
Borrelia burgdorferi
B31 Outer Surface Protein C Protective Epitope
Authors: Gilmore Robert D. , Mbow M. Lamine 
Published: December 2019

ABSTRACT

Active immunization with
Escherichia coli
-expressed recombinant outer surface protein C (OspC) of
Borrelia burgdorferi
has been demonstrated to confer protection against a tick-transmitted infection on laboratory animals. A previous study in this laboratory showed that OspC antibody raised against a denatured immunogen isolated from
B. burgdorferi
cells failed to provide protective immunity. Therefore, to determine whether the protective epitope of the recombinant antigen was sensitive to denaturation, recombinant OspC preparations were subjected to heat and chemical treatments prior to animal immunization. Following seroconversion to OspC, the animals were challenged with an infectious dose of
B. burgdorferi
B31 by tick bite. Whereas mice immunized with a soluble, nondenatured form continued to show protection rates close to 100%, mice that had been immunized with denatured antigen were not protected. Furthermore, mice that were immunized with an insoluble (rather than a soluble), nondenatured form of the recombinant OspC showed a protection rate of only 40%. Protective epitope localization experiments showed that either the amino or the carboxy end of the recombinant protein was required to react with a protective OspC-specific monoclonal antibody. The data from these experiments demonstrate that a conformational organization of the protein is essential for the protective capability of the strain B31 OspC immunogen.
An OspC-Specific Monoclonal Antibody Passively Protects Mice from Tick-Transmitted Infection by
Borrelia burgdorferi
B31
Authors: Mbow M. Lamine , Gilmore Robert D. , Titus Richard G. 
Published: December 2019

ABSTRACT

A murine monoclonal antibody directed against
Borrelia burgdorferi
B31 outer surface protein C (OspC) antigen was generated by a method whereby borreliae were inoculated into the mouse via the natural transmission mode of tick feeding. Passive immunization with this antibody resulted in protection of C3H/HeJ and outbred mice from a tick-transmitted challenge infection. Immunofluorescence staining of borrelia cells indicated surface exposure of the OspC epitope reactive with the monoclonal antibody.
Tumor Necrosis Factor (TNF) and a TNF-Mimetic Peptide Modulate the Granulomatous Response toMycobacterium bovisBCG Infection In Vivo
Authors: Roach D. R. , Briscoe H. , Baumgart K. , Rathjen D. A. , Britton W. J. 
Published: December 2019

ABSTRACTTumor necrosis factor (TNF) is a critical mediator in the immune response to mycobacteria, particularly in the formation and maintenance of granulomas. Treatment ofMycobacterium bovisBCG-infected mice with TNF and a TNF-mimetic peptide (TNF70–80) altered the number and cellular composition of granulomas. This change was associated with a moderate decrease in the bacterial burden.
Evidence ThatCryptococcus neoformansIs Melanized in Pigeon Excreta: Implications for Pathogenesis
Authors: Nosanchuk Joshua D. , Rudolph Joseph , Rosas Angel L. , Casadevall Arturo 
Published: December 2019

ABSTRACTStructures similar to the melanin “ghosts” of melanized cryptococcal cells were isolated from pigeon excreta contaminated withCryptococcus neoformans, and their growth in pigeon excreta supported melanization. The results suggest that environmentalC. neoformanscells are melanized and imply that initial infection may involve exposure to melanized cells.
Growth Rate of Mycobacteria in Mice as an Unreliable Indicator of Mycobacterial Virulence
Authors: North Robert J. , Ryan Lynn , LaCource Ronald , Mogues Tirsit , Goodrich Mariam E. 
Published: December 2019

ABSTRACTThe CDC1551 strain ofMycobacterium tuberculosiswas compared with the H37Rv strain ofM. tuberculosisand the Ravenel strain ofMycobacterium bovisfor virulence in mice. Although all three strains gave rise to the same level of stationary infection in major organs, mice infected with the Ravenel strain died much earlier from lung disease.
Expression of
Chlamydia psittaci
- and Human Immunodeficiency Virus-Derived Antigens on the Cell Surface of
Lactobacillus fermentum
BR11 as Fusions to BspA
Authors: Turner Mark S. , Giffard Philip M. 
Published: December 2019

ABSTRACT

The basic surface protein, BspA, has been used as a fusion partner to direct peptide antigens from the human immunodeficiency virus gp41 protein and the
Chlamydia psittaci
OmpA protein to the cell surface of
Lactobacillus fermentum
BR11. BspA has potential utility in the construction of live vaccines and diagnostic reagents.
Growth-Phase-Dependent Expression of Virulence Factors in an M1T1 Clinical Isolate of
Streptococcus pyogenes
Authors: Unnikrishnan Meera , Cohen Jonathan , Sriskandan Shiranee 
Published: December 2019

ABSTRACT

The effect of growth phase on expression of virulence-associated factors was studied by Northern hybridization in an M1T1 clinical isolate of
Streptococcus pyogenes
. Expression of M protein, C5a peptidase, and capsule was maximal in the exponential phase of growth, while streptococcal pyrogenic exotoxins A and B and mitogenic factor were maximally expressed in later phases of growth.
Role of Gamma Interferon in Controlling Murine Chlamydial Genital Tract Infection
Authors: Ito James I. , Lyons Joseph M. 
Published: December 2019

ABSTRACTEarlier investigations have not shown an important role for gamma interferon (IFN-γ) in the early clearance of chlamydial infection from the murine female genital tract. In a model using a human genital isolate ofChlamydia trachomatisin IFN-γ and IFN-γ receptor knockout mice, we were able to demonstrate a major role for IFN-γ in mediating control of infection throughout the course of infection.
Type III Secretion-Dependent Hemolytic Activity of Enteropathogenic
Escherichia coli
Authors: Warawa Jonathan , Finlay B. Brett , Kenny Brendan 
Published: December 2019

ABSTRACT

Enteropathogenic
Escherichia coli
(EPEC) was found to exhibit a type III secretion-dependent, contact-mediated, hemolytic activity requiring the EspA, EspB, and EspD secreted proteins. EspB and EspD display homology to pore-forming molecules. Our data suggest a mechanism to explain the requirement for all three Esp proteins in the transfer of EPEC proteins, such as Tir, into target cells.
Alpha-Toxin Damages the Air-Blood Barrier of the Lung in a Rat Model ofStaphylococcus aureus-Induced Pneumonia
Authors: McElroy Mary C. , Harty Helen R. , Hosford Gayle E. , Boylan Gráinne M. , Pittet Jean-François , Foster Timothy J. 
Published: December 2019

ABSTRACTWe have shown that injury to alveolar epithelial type I cells may account, in part, for damage to the air-blood barrier of the lung in a rat model ofStaphylococcus aureuspneumonia. We have also shown that alpha-toxin is an important cause of damage to the air-blood barrier; however, our data suggest that the toxin is not acting directly on alveolar type I cells.
Control ofLeishmania infantumInfection Is Associated with CD8+and Gamma Interferon- and Interleukin-5-Producing CD4+Antigen-Specific T Cells
Authors: Mary Charles , Auriault Valérie , Faugère Bernard , Dessein Alain J. 
Published: December 2019

ABSTRACTVisceral leishmaniasis is a severe and lethal disease caused by the protozoan parasites of the genusLeishmania. In areas where leishmaniasis is endemic, most infected individuals control the infection and remain asymptomatic; chemotherapy of visceral leishmaniasis restores some immunity which protects against relapses. In the present study,Leishmania-specific T-cell clones were established from six asymptomatic and five cured patients. Cytokines production by these clones was analyzed. A large fraction of the parasite-specific T-cell clones from asymptomatic patients were CD8+and produced high amounts of gamma interferon (IFN-γ). Most CD4+T-cell clones from two asymptomatic subjects exhibited an unusual phenotype: production of high levels of IFN-γ low levels of interleukin-4, (IL-4), but high levels of IL-5. In contrast, only few parasite-specific CD8+T-cell clones were obtained from cured patients after chemotherapy; moreover, CD4+T-cell clones from these patients exhibited an heterogeneous profile of cytokines from Th1-like to Th2-like phenotypes. These results point to CD8+T cells and to IL-5- and IFN-γ-producing CD4+T cells as possible contributors to human resistance toLeishmaniainfection. They should stimulate new immunological approaches in the control of this disease.
Interleukin-1 Inhibits Gamma Interferon-Induced Bacteriostasis in Human Uroepithelial Cells
Authors: Däubener Walter , Hucke Christian , Seidel Kerstin , Hadding Ulrich , MacKenzie Colin R. 
Published: December 2019

ABSTRACTThe most prominent gamma interferon (IFN-γ)-induced antimicrobial effector mechanisms are the induction of nitric oxide (NO) synthase (NOS) and of indoleamine 2,3-dioxygenase (IDO) activity. We have recently found that human glioblastoma cells and human macrophages inhibit the growth of group B streptococci after stimulation with IFN-γ. In this report, we show that in addition, human RT4 (uroepithelial) cells can inhibit the growth of enterococci. Murine macrophages (RAW cells) are unable to inhibit bacterial growth after IFN-γ stimulation. Stimulation of human glioblastoma cells, macrophages, and RT4 cells with human IFN-γ results in a strong expression of IDO activity; however, NO production remains undetectable. In strong contrast, murine RAW cells produce large amounts of NO when stimulated with murine IFN-γ and IDO activity is not detectable. Interleukin-1 (IL-1) induces NO synthase in human RT4 cells when the cells are costimulated with IFN-γ. We found that IL-1 inhibits IFN-γ-stimulated IDO activity and antimicrobial effects in RT4 cells, while in human glioblastoma cells, which lack detectable NO synthase activity, neither of these effects was altered by costimulation with IFN-γ and IL-1. The IL-1-mediated inhibition of IDO activity and of subsequent antibacterial effect is due to the production of NO. This conclusion was supported by evidence thatNG-monomethyl-l-arginine, a competitive inhibitor of inducible NOS activity, is able to block the inhibitory action of IL-1 on IFN-γ-induced bacteriostasis. We therefore conclude that NO production does not inhibit the growth of enterococci but might be involved in the regulation of IDO activity in some human cells.