bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pregenomic Comparative Analysis betweenBordetella bronchisepticaRB50 andBordetella pertussisTohama I in Murine Models of Respiratory Tract Infection
Authors: Harvill Eric T. , Cotter Peggy A. , Miller Jeff F. 
Published: December 2019

ABSTRACTWe describe here a side-by-side comparison of murine respiratory infection byBordetella pertussisandBordetella bronchisepticastrains whose genomes are currently being sequenced (Tohama I and RB50, respectively).B. pertussisandB. bronchisepticaare most appropriately classified as subspecies. Their high degree of genotypic and phenotypic relatedness facilitates comparative studies of pathogenesis. RB50 and Tohama I differ in their abilities to grow in the nose, trachea, and lungs of BALB/c mice and to induce apoptosis, lung pathology, and an antibody response. To focus on the interactions between the bacteria and particular aspects of the host immune response, we used mice with specific immune defects. Mice lacking B cells and T cells were highly susceptible toB. bronchisepticaand were killed by intranasal inoculation with doses as low as 500 CFU. These mice were not killed byB. pertussis, even when doses as high as 105CFU were delivered to the lungs.B. bronchiseptica, which was highly resistant to naive serum in vitro, caused bacteremia in these immunodeficient mice, whileB. pertussis, which was highly sensitive to naive serum, did not cause bacteremia.B. bronchisepticawas, however, killed by immune serum in vitro, and adoptive transfer of anti-Bordetellaantibodies protected SCID-beige mice fromB. bronchisepticalethal infection. Neutropenic mice were similarly killed byB. bronchisepticabut notB. pertussisinfection, suggesting neutrophils are critical to the early inflammatory response to the former but not the latter.B. bronchisepticawas dramatically more active thanB. pertussisin mediating the lysis of J774 cells in vitro and in inducing apoptosis of inflammatory cells in mouse lungs. This side-by-side comparison describes phenotypic differences that may be correlated with genetic differences in the comparative analysis of the genomes of these two highly related organisms.
Bacterial Species- and Strain-Dependent Induction of Tissue Factor in Human Vascular Endothelial Cells
Authors: Veltrop M. H. A. M. , Beekhuizen H. , Thompson J. 
Published: December 2019

ABSTRACTA cardinal process in bacterial endocarditis (BE) is the activation of the clotting system and the formation of a fibrin clot on the inner surface of the heart, the so-called endocardial vegetation. The processes that lead to the activation of the clotting system on endothelial surfaces upon exposure to bacteria are largely unknown. In the present study, we investigated in an in vitro model whether infection of human endothelial cells (EC) with bacteria that are relevant to BE, such asStaphylococcus aureus,Streptococcus sanguis, andStaphylococcus epidermidis, leads to induction of tissue factor (TF)-dependent procoagulant activity (TFA) and whether this process is influenced by host factors, such as interleukin-1 (IL-1), that are produced in response to the bacteremia in vivo. The results show thatS. aureusbinds to and is internalized by EC, resulting in expression of TF mRNA and TF surface protein as well as generation of TFA within 4 to 8 h after infection. No TFA was found when EC were exposed to UV-irradiatedS. aureusor bacterial cell wall fragments.S. sanguisandS. epidermidis, although also binding to EC, did not induce endothelial TFA. This indicates a species and strain dependency. EC also expressed TFA after exposure to IL-1. The enhanced TFA of EC after exposure toS. aureuswas not prevented by IL-1 receptor antagonist, arguing against an auto- or paracrine contribution of endogenous IL-1. When IL-1 was applied together with bacteria, this had a synergistic effect on the induction of EC TFA. This was found in particular withS. aureusbut also, although to a lesser degree, withS. sanguisandS. epidermidis. This influence of IL-1 on the species- and strain-dependent induction of EC TFA suggests that bacterial factors as well as host factors orchestrate the induction of coagulation in an early stage in the pathogenesis of endovascular disease, such as BE.
Analysis of
Pneumocystis carinii
Introns
Authors: Thomas Charles F. , Leof Edward B. , Limper Andrew H. 
Published: December 2019

ABSTRACT

Pneumocystis carinii
is an ascomycete phylogenetically related to
Schizosaccharomyces pombe
. Little is known about gene regulation in
P. carinii
. The removal of introns from pre-mRNA requires spliceosomal recognition of the intron-exon boundary. In
S. pombe
and higher eukaryotes, this boundary and a branch site within the intron are conserved. We recently demonstrated that
P. carinii cdc2
cDNA can complement
S. pombe
containing conditional mutations of
cdc2
, an essential gene involved in cell cycle regulation. We next tested whether
P. carinii
genomic
cdc2
(with six introns) could also complement
S. pombe cdc2
mutants and found genomic sequences incapable of this activity. Reverse transcriptase PCR confirmed the inability of the
S. pombe cdc2
mutants to splice the
P. carinii
genomic
cdc2
. Analysis of 83 introns from 19
P. carinii
protein-encoding genes demonstrated that the sequence GTWWDW functions as a donor consensus in
P. carinii
, whereas YAG serves as an acceptor consensus. These sequences are similar in
S. pombe
; however, a branch site sequence was not found in the
P. carinii
genes studied.
The Outer Membrane ofBrucella ovisShows Increased Permeability to Hydrophobic Probes and Is More Susceptible to Cationic Peptides than Are the Outer Membranes of Mutant RoughBrucella abortusStrains
Authors: Freer Enrique , Pizarro-Cerdá Javier , Weintraub Andrej , Bengoechea José-Antonio , Moriyón Ignacio , Hultenby Kjell , Gorvel Jean-Pierre , Moreno Edgardo 
Published: December 2019

ABSTRACTThe permeability of the outer membrane (OM) to hydrophobic probes and its susceptibility to bactericidal cationic peptides were investigated for natural roughBrucella ovisand for mutant roughBrucella abortusstrains. The OM ofB. ovisdisplayed an abrupt and faster kinetic profile than roughB. abortusduring the uptake of the hydrophobic probeN-phenyl-naphthylamine.B. oviswas more sensitive than roughB. abortusto the action of cationic peptides. Bactenecins 5 and 7 induced morphological alterations on the OMs of both roughBrucellastrains.B. ovislipopolysaccharide (LPS) captured considerably more polymyxin B than LPSs from both rough and smoothB. abortusstrains. Polymyxin B, poly-l-lysine, and poly-l-ornithine produced a thick coating on the surfaces of both strains, which was more evident inB. ovisthan in roughB. abortus. The distinct functional properties of the OMs of these two rough strains correlate with some structural differences of their OMs and with their different biological behaviors in animals and culture cells.
Syntheses and Immunologic Properties of
Escherichia coli
O157 O-Specific Polysaccharide and Shiga Toxin 1 B Subunit Conjugates in Mice
Authors: Konadu Edward , Donohue-Rolfe Arthur , Calderwood Stephen B. , Pozsgay Vince , Shiloach Joseph , Robbins John B. , Szu Shousun C. 
Published: December 2019

ABSTRACT

Escherichia coli
O157 is the major cause of diarrhea-associated hemolytic uremic syndrome (HUS). Strains causing HUS contain either Shiga toxin 1 (Stx1) or Stx2, or both. In adult volunteers, conjugate vaccines of detoxified lipopolysaccharide (LPS) elicited bactericidal antibodies to
E. coli
O157. Here, the detoxified LPS was conjugated with improved schemes to the nontoxic B subunit of Stx1. Mice injected with these bivalent conjugates elicited both bactericidal antibodies to
E. coli
O157 and neutralization antibodies to Stx1.
Urease-Based Mucosal Immunization againstHelicobacter heilmanniiInfection Induces Corpus Atrophy in Mice
Authors: Dieterich Christine , Bouzourène Hanifa , Blum André L. , Corthésy-Theulaz Irène E. 
Published: December 2019

ABSTRACTMucosal immunization withHelicobacter heilmanniiurease B orHelicobacter pyloriurease, given nasally with cholera toxin, protects BALB/c mice againstH. heilmanniiinfection and significantly reduces a preexisting infection. However, immunization aggravates gastric corpus atrophy. Our results underline the necessity of defining immunization regimens that do not enhance mucosal damage.
Interleukin 18 Contributes to Host Resistance and Gamma Interferon Production in Mice Infected with VirulentSalmonella typhimurium
Authors: Mastroeni Pietro , Clare S. , Khan S. , Harrison J. A. , Hormaeche C. E. , Okamura H. , Kurimoto M. , Dougan G. 
Published: December 2019

ABSTRACTSpleen and peritoneal macrophages obtained from innately resistant A/J mice released low levels of interleukin 18 (IL-18) upon infection withSalmonella typhimuriumC5 RP4. Incubating the cells with recombinant gamma interferon (rIFN-γ) enhanced IL-18 production. A/J mice treated in vivo with anti-IL-18 antibodies showed impaired resistance to infection, with increased bacterial loads in the liver and spleen. Administration of rIL-18 could protect A/J mice from challenge with a lethal dose of virulent salmonellae, with a dramatic reduction in bacterial numbers in the tissues. rIL-18 administration did not ameliorate the disease in IFN-γ-R−/−mice. IL-18 proved to be required for IFN-γ production by mouse splenocytes from conventional,scid, andrag-1−/−mice; in vivo IL-18 neutralization caused a decrease in circulating IFN-γ levels. Thus, IL-18 is a key factor in early host resistance toSalmonellaand probably acts via IFN-γ.
Role of Adult Worm Antigen-Specific Immunoglobulin E in Acquired Immunity toSchistosoma mansoniInfection in Baboons
Authors: Nyindo Mramba , Kariuki Thomas M. , Mola Paul W. , Farah Idle O. , Elson Lynne , Blanton Ronald E. , King Christopher L. 
Published: December 2019

ABSTRACTAllergic-type immune responses, particularly immunoglobulin E (IgE), correlate with protective immunity in human schistosomiasis. To better understand the mechanisms of parasite elimination we examined the immune correlates of protection in baboons (Papio cynocephalus anubis), which are natural hosts forSchistosoma mansoniand also develop allergic-type immunity with infection. In one experiment, animals were exposed to a single infection (1,000 cercariae) or were exposed multiple times (100 cercariae per week for 10 weeks) and subsequently were cured with praziquantel prior to challenge with 1,000 cercariae. Singly and multiply infected animals mounted 59 and 80% reductions in worm burden, respectively (P< 0.01). In a second experiment, animals were inoculated withS. mansoniova and recombinant human interleukin 12 (IL-12). This produced a 37 to 39% reduction in adult worm burden after challenge (P< 0.05). Parasite-specific IgG, IgE, IgM, and peripheral blood cytokine production were evaluated. The only immune correlate of protection in both experiments was levels of soluble adult worm antigen (SWAP)-specific IgE in serum at the time of challenge infection and/or 6 weeks later. Baboons repeatedly infected with cercariae or immunized with ova and IL-12 developed two- to sixfold-greater levels of SWAP-specific IgE in serum than did controls, and this correlated with reductions in worm burden (r2, −0.40 to −0.64;P, <0.01). Thus, in baboons and unlike mice, adult worm-specific IgE is uniquely associated with acquired immunity toS. mansoniinfection. This similar association of parasite-specific IgE and protection among primates infected with schistosomiasis, along with similar pathology, anatomy, and genetic make-up, indicates that baboons provide an excellent permissive experimental model for better understanding the mechanisms of innate and acquired immunity to schistosomiasis in humans.
Increased Type 1 Fimbrial Expression among CommensalEscherichia coliIsolates in the Murine Cecum following Catabolic Stress
Authors: Hendrickson Barbara A. , Guo Jun , Laughlin Robert , Chen Yimei , Alverdy John C. 
Published: December 2019

ABSTRACTAlthough indigenous bacteria intimately colonize the intestinal mucosa, under normal conditions the intestinal epithelial cell is free of adherent bacteria. Nonetheless, commensal bacteria such asEscherichia coliadhere to and translocate across the intestinal epithelium in association with a number of pathologic states including hemorrhagic shock, immunosuppression, traumatic tissue injury, and lack of enteral feedings. The adhesins involved in the adherence of indigenousE. colito the intestinal epithelium in vivo following catabolic stress are unknown. We have developed a mouse model to study the bacterial adhesins which mediate the increased intestinal adherence ofE. coliafter partial hepatectomy and short-term starvation. Our studies demonstrated that hepatectomy and starvation in the mouse were associated with a 7,500-fold increase in the numbers ofE. colibacteria adhering to the cecum. In addition, erythrocyte agglutination studies, as well as immunostaining of fimbrial preparations and electron micrographs of the bacteria, revealed that surface type 1 fimbriae were more abundant in the commensalE. coliharvested from the ceca of the stressed mice. TheseE. coliisolates adhered to a mouse colon cell line and injected cecal loops in a mannose-inhibitable manner, which suggests a role for type 1 fimbriae in the adherence of theE. coliisolates to the cecum in vivo following host catabolic stress.
Characterization of the Avian PathogenicEscherichia coliHemagglutinin Tsh, a Member of the Immunoglobulin A Protease-Type Family of Autotransporters
Authors: Stathopoulos Christos , Provence David L. , Curtiss Roy 
Published: December 2019

ABSTRACTWe reported earlier that a single gene,tsh, isolated from a strain of avian pathogenicEscherichia coli(APEC) was sufficient to confer onE. coliK-12 a hemagglutinin-positive phenotype and that the deduced sequence of the Tsh protein shared homology to the serine-type immunoglobulin A (IgA) proteases ofNeisseria gonorrhoeaeandHaemophilus influenzae. In this report we show thatE. coliK-12 containing the recombinanttshgene produced two proteins, a 106-kDa extracellular protein and a 33-kDa outer membrane protein, and was also able to agglutinate chicken erythrocytes. N-terminal sequence data indicated that the 106-kDa protein, designated Tshs, was derived from the N-terminal end of Tsh after the removal of a 52-amino-acid N-terminal signal peptide, while the 33-kDa protein, designated Tshβ, was derived from the C-terminal end of Tsh starting at residue N1101. The Tshsdomain contains the 7-amino-acid serine protease motif that includes the active-site serine (S259), found also in the secreted domains of the IgA proteases. However, site-directed mutagenesis of S259did not abolish the hemagglutinin activity or the extracellular secretion of Tshsindicating that host-directed proteolysis was mediating the release of Tshs. Studies with anE. coliK-12ompTmutant strain showed that the surface protease OmpT was not needed for the secretion of Tshs. Tsh belongs to a subclass of the IgA protease family, which also includes EspC of enteropathogenicE. coli, EspP of enterohemorragicE. coli, and SepA and VirG ofShigella flexneri, which seem to involve a host endopeptidase to achieve extracellular release of their N-terminal domains. In proteolytic studies conducted in vitro, Tshsdid not cleave the substrate of the IgA proteases, human IgA1 or chicken IgA, and did not show proteolytic activity in a casein-based assay. Correlation of Tsh expression and hemagglutination activity appears to be a very complex phenomenon, influenced by strain and environmental conditions. Nevertheless, for both APEC and recombinantE. coliK-12 strains containing thetshgene, it was only the whole bacterial cells and not the cell-free supernatants that could confer hemagglutinin activity. Our results provide insights into the expression, secretion, and proteolytic features of the Tsh protein, which belongs to the growing family of gram-negative bacterial extracellular virulence factors, named autotransporters, which utilize a self-mediated mechanism to achieve export across the bacterial cell envelope.
Cytotoxic Action of
Serratia marcescens
Hemolysin on Human Epithelial Cells
Authors: Hertle Ralf , Hilger Martina , Weingardt-Kocher Sandra , Walev Iwan 
Published: December 2019

ABSTRACT

Incubation of human epithelial cells with nanomolar concentrations of chromatographically purified
Serratia marcescens
hemolysin (ShlA) caused irreversible vacuolation and subsequent lysis of the cells. Vacuolation differed from vacuole formation by
Helicobacter pylori
VacA. Sublytic doses of ShlA led to a reversible depletion of intracellular ATP. Restoration to the initial ATP level was presumably due to the repair of the toxin damage and was inhibited by cycloheximide. Pores formed in epithelial cells and fibroblasts without disruption of the plasma membrane, and the pores appeared to be considerably smaller than those observed in artificial lipid membranes and in erythrocytes and did not allow the influx of propidium iodide or trypan blue. All cytotoxic effects induced by isolated recombinant ShlA were also obtained with exponentially growing
S. marcescens
cells. The previously suggested role of the hemolysin in the pathogenicity of
S. marcescens
is supported by these data.
Roles of PilC and PilE Proteins in Pilus-Mediated Adherence of
Neisseria gonorrhoeae
and
Neisseria meningitidis
to Human Erythrocytes and Endothelial and Epithelial Cells
Authors: Scheuerpflug Ina , Rudel Thomas , Ryll Roland , Pandit Jasmine , Meyer Thomas F. 
Published: December 2019

ABSTRACT

Unlike other type 4 pili, the neisserial pili consist of at least two distinct proteins, the highly variable major subunit PilE forming the pilus fiber and the tip-associated adhesin PilC. PilC protein purified either from gonococci or from
Escherichia coli
interacted with different human epithelial cell lines, primary epithelial and endothelial cells. The binding of PilC protein efficiently prevented the attachment of piliated
Neisseria gonorrhoeae
and
Neisseria meningitidis
to these cell types. Fluorescent beads coated with pili prepared from piliated wild-type
N. gonorrhoeae
also adhered to these cells, in contrast to beads coated with pili prepared from a piliated PilC-deficient mutant. In the latter case, the binding of fluorescent beads was restored after pretreatment of the pilus-loaded beads with purified PilC. Piliated wild-type
N. gonorrhoeae
, the piliated PilC-deficient mutant, and
N. gonorrhoeae
pili assembled in
Pseudomonas aeruginosa
agglutinated human erythrocytes, while nonpiliated gonococci did not. Consistently, purified PilC did not agglutinate or bind to human erythrocytes, suggesting that
N. gonorrhoeae
PilE is responsible for pilus-mediated hemagglutination.
Apoptosis in Macrophages and Alveolar Epithelial Cells during Early Stages of Infection byLegionella pneumophilaand Its Role in Cytopathogenicity
Authors: Gao Lian-Yong , Abu Kwaik Yousef 
Published: December 2019

ABSTRACTThe hallmark of Legionnaires’ disease is intracellular replication ofLegionella pneumophilawithin cells in the alveolar spaces. Cytopathogenicity of this bacterium to the host cell has been well demonstrated, but the mechanisms of host cell death due to infection byL. pneumophilaare not well understood. In this study, induction of apoptosis in macrophages and alveolar epithelial cells byL. pneumophiladuring early stages of infection was confirmed by using multiple criteria, including DNA fragmentation by agarose gel electrophoresis, terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling, surface exposure of phosphatidylserine, and cellular morphology by transmission electron microscopy. Induction of nuclear apoptosis inL. pneumophila-infected macrophages is mediated by activation of the caspase cascade death machinery. We provide genetic and biochemical evidence thatL. pneumophila-induced apoptosis in macrophages and alveolar epithelial cells does not require intracellular bacterial replication or new protein synthesis. In addition, extracellularL. pneumophilais capable of inducing apoptosis. Furthermore, induction of apoptosis byL. pneumophilacorrelates with cytopathogenicity. We conclude thatL. pneumophila-induced apoptosis in macrophages and alveolar epithelial cells plays an important role in cytopathogenicity to the host cell during early stages of infection.
Cryptococcus neoformansResides in an Acidic Phagolysosome of Human Macrophages
Authors: Levitz Stuart M. , Nong Shu-Hua , Seetoo Kurt F. , Harrison Thomas S. , Speizer Robert A. , Simons Elizabeth R. 
Published: December 2019

ABSTRACTRecently, we demonstrated that human monocyte-derived macrophages (MDM) treated with chloroquine or ammonium chloride had markedly increased antifungal activity against the AIDS-related pathogenCryptococcus neoformans. Both of these agents raise the lysosomal pH, which suggested that the increased antifungal activity was a function of alkalinizing the phagolysosome. Moreover, there was an inverse correlation between growth ofC. neoformansin cell-free media and pH. These data suggested thatC. neoformanswas well adapted to survive within acidic compartments. To test this hypothesis, we performed studies to determine the pH of human MDM and neutrophil phagosomes containingC. neoformans. Fungi were labeled with the isothiocyanate derivatives of two pH-sensitive probes: fluorescein and 2′,7′-difluorofluorescein (Oregon Green). These probes have pKas of 6.4 and 4.7, respectively, allowing sensitive pH detection over a broad range. The phagosomal pH averaged approximately 5 after ingestion of either live or heat-killed fungi and remained relatively constant over time, which suggested thatC. neoformansdoes not actively regulate the pH of its phagosome. The addition of 10 and 100 μM chloroquine resulted in increases in the phagosomal pH from a baseline of 5.1 up to 6.5 and 7.3, respectively. Finally, by immunofluorescence, colocalization ofC. neoformansand the MDM lysosomal membrane protein LAMP-1 was demonstrated, establishing that fusion ofC. neoformans-laden phagosomes with lysosomal compartments takes place. Thus, unlike many other intracellular pathogens,C. neoformansdoes not avoid fusion with macrophage lysosomal compartments but rather resides and survives in an acidic phagolysosome.