bluuebunny/crossref_metadata_2025_split huggingface dataset:
Survival ofMycobacterium aviumandMycobacterium tuberculosisin Acidified Vacuoles of Murine Macrophages
Authors: Gomes Maria Salomé , Paul Simon , Moreira Andre L. , Appelberg Rui , Rabinovitch Michel , Kaplan Gilla 
Published: December 2019

ABSTRACTDespite the antimicrobial mechanisms of vertebrate phagocytes, mycobacteria can survive within the phagosomes of these cells. These organisms use various strategies to evade destruction, including inhibition of acidification of the phagosome and inhibition of phagosome-lysosome fusion. In contrast to mycobacteria,Coxiella burnetii, the etiologic agent of Q fever, inhabits a spacious acidified intracellular vacuole which is prone to fusion with other vacuoles of the host cell, including phagosomes containing mycobacteria. TheCoxiella-infected cell thus provides a unique model for investigating the survival of mycobacteria in an acidified phagosome-like compartment. In the present study, murine bone marrow-derived macrophages were infected with eitherMycobacterium aviumorMycobacterium tuberculosisand then coinfected withC. burnetii. We observed that the majority of phagocytosed mycobacteria colocalized to theC. burnetii-containing vacuole, which maintained its acidic properties. In coinfected macrophages, the growth ofM. aviumwas not impaired following fusion with the acidified vacuole. In contrast, the growth rate ofM. tuberculosiswas reduced in acidified vacuoles. These results suggest that although both species of mycobacteria inhibit phagosome-lysosome fusion, they may be differentially susceptible to the toxic effects of the acidic environment in the mature phagolysosome.
Innate Antimicrobial Activity of Nasal Secretions
Authors: Cole Alexander M. , Dewan Puneet , Ganz Tomas 
Published: December 2019

ABSTRACT

Minimally manipulated nasal secretions, an accessible form of airway surface fluid, were tested against indigenous and added bacteria by using CFU assays. Antimicrobial activity was found to vary between donors and with different target bacteria and was markedly diminished by dilution of the airway secretions. Donor-to-donor differences in electrophoresis patterns of nasal secretions in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE) and acid urea-PAGE analyses were readily observed, suggesting that polymorphic genes encode the secreted proteins. Three donors (of twenty-four total), whose nasal fluid yielded similar protein band patterns and did not kill indigenous bacteria, were determined to be heavy nasal carriers of
Staphylococcus aureus
. Their fluid was deficient in microbicidal activity toward a colonizing strain of
S. aureus
but the defect was corrected in vitro by a 1:1 addition of nasal fluid from noncarriers. The microbicidal activity of normal fluid was inactivated by heating it for 10 min to 100°C and could not be restored solely by the addition of two major nasal antimicrobial proteins, lysozyme and lactoferrin. Several other known antimicrobial proteins and peptides, including statherin, secretory phospholipase A
2
, and defensins, were identified in nasal secretions and likely contribute to their total antimicrobial properties. Nasal fluid may serve as a useful model for the analysis of lower-airway secretions and their role in host defense against airway colonization and pulmonary infections.
Role of Lactosyl Glycan Sequences in Inhibiting Enteropathogenic
Escherichia coli
Attachment
Authors: Vanmaele Rosa P. , Heerze Louis D. , Armstrong Glen D. 
Published: December 2019

ABSTRACT

Previously, we found that asialo-lactosamine sequences served as receptors for enteropathogenic
Escherichia coli
(EPEC) binding to Chinese hamster ovary (CHO) cells. In the present report, we have extended these earlier results by examining the ability of lactosamine- or fucosylated lactosamine-bovine serum albumin (BSA) glycoconjugates to inhibit EPEC, strain E2348/69, binding to HEp-2 cells. We found that, consistent with our previous findings with CHO cells,
N
-acetyllactosamine-BSA was the most effective inhibitor of EPEC localized adherence to HEp-2 cells, with Lewis X-BSA being the next best inhibitor. Further investigation revealed that coincubating EPEC E2348/69 with these BSA glycoconjugates alone caused a decrease in the expression of the bundle-forming pilus structural subunit (BfpA) and intimin by the bacteria. BfpA and intimin expression were reduced to the greatest extent by
N
-acetyllactosamine–BSA and Lewis X-BSA, respectively. These results suggest that the glycoconjugate inhibition of EPEC binding to HEp-2 cells might be achieved, wholly or in part, by an active mechanism that is distinct from simple competitive antagonism of receptor-adhesin interactions.
T-Cell Responses duringTrypanosoma bruceiInfections in Mice Deficient in Inducible Nitric Oxide Synthase
Authors: Millar Amanda E. , Sternberg Jerry , McSharry Charlie , Wei Xiao-Qing , Liew F. Y. , Turner C. Michael R. 
Published: December 2019

ABSTRACTWe have investigated the possibility that nitric oxide (NO) synthesis may affect the course of a trypanosome infection via T-cell responses using mice deficient in inducible NO synthase (iNOS). Parasitemia levels increased at the same rate in both iNOS-deficient homozygous and control heterozygous mice, and peak parasitemia values were the same in both groups. However, the heterozygous mice maintained higher parasitemia levels after the peak of an infection than the homozygous mice due to a decrease in the rate of clearance of parasites. In iNOS-deficient mice there was an increase in the numbers of total CD4+cells and activated (interleukin-2 receptor-expressing) CD4+cells in infected mice compared with the numbers in uninfected mice. Spleen cells from infected iNOS-deficient mice displayed increased proliferative responses and gamma interferon secretion when stimulated in vitro than those of control mice. These data suggest that NO production depresses T-helper 1-like responses generated duringTrypanosoma bruceiinfections, thus promoting the survival of the parasite.
Pathogenesis of Gram-Positive Bacterial Endophthalmitis
Authors: Callegan Michelle C. , Booth Mary C. , Jett Bradley D. , Gilmore Michael S. 
Published: December 2019

ABSTRACTThe severity of endophthalmitis has been associated generally with the virulence of the offending pathogen. However, precisely what constitutes the virulence in intraocular infections remains ill defined. We therefore sought to identify the basis for virulence for three common ocular pathogens (Bacillus cereus,Enterococcus faecalis, andStaphylococcus aureus) in terms of intraocular growth rates, bacterial localization patterns, and the contribution of cell walls and secreted products to the pathogenesis of endophthalmitis. Rabbit eyes were injected intravitreally with (i) viableB. cereus,E. faecalis, orS. aureus, (ii) metabolically inactiveB. cereus,E. faecalis, orS. aureus, (iii) sacculus preparations from each strain, or (iv) culture fluid containing products secreted by each strain. Eyes were assessed at various times following injection by slit lamp biomicroscopy, electroretinography (ERG), bacterial and inflammatory cell enumeration, and histology.B. cereusendophthalmitis followed a more rapid and virulent course thanE. faecalisorS. aureusendophthalmitis, eliminating retinal responsiveness, as measured by ERG, by 12 h. Analysis of bacterial localization revealed thatB. cereusuniquely migrated rapidly from posterior to anterior segment during infection. Although injection of neither metabolically inactive bacteria nor cell wall sacculi greatly affected ERG, significant intraocular inflammation was observed. Injection ofB. cereusorS. aureusculture fluids caused both significant reductions in retinal responsiveness and significant intraocular inflammation, paralleling that seen in natural infections. The results demonstrate that toxins, intraocular localization, and, to a lesser extent, the intraocular host response to cell walls all contribute to the pathogenesis ofB. cereus,S. aureus, andE. faecalisendophthalmitis in a pathogen-specific manner. The key pathophysiologic differences in these intraocular diseases highlight opportunities for optimizing conventional therapies and deriving new ones.
Deacylation of Purified Lipopolysaccharides by Cellular and Extracellular Components of a Sterile Rabbit Peritoneal Inflammatory Exudate
Authors: Weinrauch Yvette , Katz Seth S. , Munford Robert S. , Elsbach Peter , Weiss Jerrold 
Published: December 2019

ABSTRACTThe extent to which the mammalian host is capable of enzymatic degradation and detoxification of bacterial lipopolysaccharides (LPS) is still unknown. Partial deacylation of LPS by the enzyme acyloxyacyl hydrolase (AOAH) provides such a mechanism, but its participation in the disposal of LPS under physiological conditions has not been established. In this study, deacylation of isolated radiolabeled LPS by both cellular and extracellular components of a sterile inflammatory peritoneal exudate elicited in rabbits was examined ex vivo. AOAH-like activity, tested under artificial conditions (pH 5.4, 0.1% Triton X-100), was evident in all components of the exudate (mononuclear cells [MNC] > polymorphonuclear leukocytes [PMN] > inflammatory [ascitic] fluid [AF]). Under more physiological conditions, in a defined medium containing purified LPS-binding protein, the LPS-deacylating activity of MNC greatly exceeded that of PMN. In AF, MNC (but not PMN) also produced rapid and extensive CD14-dependent LPS deacylation. Under these conditions, almost all MNC-associated LPS underwent deacylation within 1 h, a rate greatly exceeding that previously found in any cell type. The remaining extracellular LPS was more slowly subject to CD14-independent deacylation in AF. Quantitative analysis showed a comparable release of laurate and myristate but no release of 3-hydroxymyristate, consistent with an AOAH-like activity. These findings suggest a major role for CD14+MNC and a secondary role for AF in the deacylation of cell-free LPS at extravascular inflammatory sites.
Isolation of T-Cell Antigens by Using a Recombinant Protein Library and Its Application to the Identification of Novel Vaccine Candidates against Schistosomiasis
Authors: Eberl Matthias , Mountford Adrian P. , Jankovic Dragana , Beck Ewald 
Published: December 2019

ABSTRACTWe present here a novel approach to identify T-cell antigens from any infectious agent by use of a library of purified recombinant proteins. Essential features of this strategy include (i) a highly efficient cDNA cloning system which negatively selects against nonrecombinant transformants by making use of the bacterialEcoK restriction system, (ii) affinity staining of cDNA clones expressing recombinant proteins, and (iii) a procedure of simultaneous purification of recombinant proteins from large numbers of isolated clones (representing the protein library) in a single step from pools consisting of up to 24 individual clones. The feasibility of the screening system was confirmed by constructing a protein library of the human parasiteSchistosoma mansoni. The recombinant antigens of this library were used to stimulate CD4+T cells derived from the axillary lymph nodes of mice vaccinated with irradiated cercariae. In initial screening experiments, we detected parasite-specific proliferation and gamma interferon (IFN-γ) secretion in response to several pools of cDNA clones. Further analysis of one particular pool revealed that only one of its constituents stimulated considerable IFN-γ secretion by CD4+T cells and that the expressed antigen is identical to a small fragment of myosin heavy chain.
A Localized Adherence-Like Pattern as a Second Pattern of Adherence of Classic Enteropathogenic
Escherichia coli
to HEp-2 Cells That Is Associated with Infantile Diarrhea
Authors: Scaletsky Isabel C. A. , Pedroso Margareth Z. , Oliva Carlos A. G. , Carvalho Rozane L. B. , Morais Mauro B. , Fagundes-Neto Ulysses 
Published: December 2019

ABSTRACT

Escherichia coli
strains that cause nonbloody diarrhea in infants are known to present three distinct patterns of adherence to epithelial cells, namely, localized (LA), diffuse (DA), and aggregative (AA) adherence. Strains with LA (typical Enteropathogenic
Escherichia coli
[EPEC]) are well recognized as a cause of secretory diarrhea, but the role of strains with DA (DAEC) is controversial, and strains with AA (EAEC) have been more frequently related to persistent diarrhea whereas its relationship with acute diarrhea is not well defined. To determine the relationship of the different types of
E. coli
adherence patterns with acute diarrhea (lasting less than 14 days) and persistent diarrhea (lasting more than 14 days) in São Paulo, Brazil, we studied stool specimens from 40 infants under 1 year of age with diarrhea and 40 age-matched control infants without any gastrointestinal symptoms. Twenty-eight (35.0%) of eighty cases yielded adherent
E. coli
(HEp-2 cells). Strains with localized and aggregative adherence were associated with acute and persistent diarrhea. A total of 11.2% of the adherent strains were typical EPEC serotypes and hybridized with the enteroadherence factor probe; 5.0% were EAEC and hybridized with the EAEC probe. DAEC strains were isolated from 10.0% of patients and 7.5% of controls and did not hybridize with the two probes used (
daaC
and AIDA-I). Strains with a localized adherence-like pattern (atypical EPEC) were found significantly more frequently (
P
= 0.028) in cultures from children with diarrhea (17.5%) than in controls (2.5%).
Neisseria gonorrhoeae
Coordinately Uses Pili and Opa To Activate HEC-1-B Cell Microvilli, Which Causes Engulfment of the Gonococci
Authors: Griffiss J. McLeod , Lammel Claudia J. , Wang Jun , Dekker Nusi P. , Brooks G. F. 
Published: December 2019

ABSTRACT

This study was undertaken to examine concomitant roles of pili and colony opacity-associated proteins (Opa) in promoting
Neisseria gonorrhoeae
adherence to and invasion of human endometrial HEC-1-B cells. Adherence of
N. gonorrhoeae
to cultured HEC-1-B cells was saturable, even though organisms adhered to <50% of the cells. During 4 to 6 h of incubation, adherent mono- and diplococci formed microcolonies on the surfaces of the cells. Microvilli of the HEC-1-B cells adhered by their distal ends to individual cocci within the microcolonies. When the microcolonies grew from isogenic pilus-negative (P
−
) Opa
−
, P
−
Opa
+
, or P
+
Opa
−
gonococci, microvilli did not elongate, and the colonies were not engulfed. In contrast, the microvilli markedly elongated during exposure to P
+
Opa
+
gonococci. The microvilli adhered to the organisms along their full lengths and appeared to actively participate in the engulfment of the microcolonies. Internalized microcolonies, with P
+
Opa
+
gonococci, contained dividing cocci and appeared to be surrounded by cell membrane but were not clearly within vacuoles. In contrast, degenerate individual organisms were within vacuoles. Low doses of chloramphenicol, which inhibits protein synthesis by both prokaryotes and eukaryotes, prevented the microvillar response to and internalization of the P
+
Opa
+
gonococci; higher doses caused internalization without microvillus activation. Cycloheximide and anisomycin, which inhibit only eukaryotic protein synthesis, caused dose-dependent enhancement of uptake. Cytochalasins reduced engulfment; colchicine had no effect. These results show that gonococci must express both pili and Opa to be engulfed efficiently by HEC-1-B cells.
Effect of
Escherichia coli
Cytotoxic Necrotizing Factor 1 on Repair of Human Bladder Cell Monolayers In Vitro
Authors: Island Michael D. , Cui Xaioling , Warren John W. 
Published: December 2019

ABSTRACT

We hypothesized that
Escherichia coli
cytotoxic necrotizing factor 1 (CNF1) might impair migration or proliferation of bladder cells and could potentially interfere with repair of the bladder epithelium. Using experimentally wounded human T24 bladder epithelial cell monolayers as an in vitro model, we found that both the number of T24 cells and the maximum distance they migrated into wounded regions was significantly decreased by bacterial extracts containing
E. coli
CNF1.
Effect of Intrastrain Variation in the Amount of Capsular Polysaccharide on Genetic Transformation of
Streptococcus pneumoniae
: Implications for Virulence Studies of Encapsulated Strains
Authors: Weiser Jeffrey N. , Kapoor Miki 
Published: December 2019

ABSTRACT

The degrees of competence of opaque and transparent colony variants of
Streptococcus pneumoniae
were compared. The transparent variants were transformed at 9- to 670-fold-higher rates than the opaque variants, independent of the DNA incorporated, due to decreased expression of capsular polysaccharide. Genetic transformation, therefore, tends to select for a less-encapsulated subpopulation.
Recombination betweengtfBandgtfCIs Required for Survival of a dTDP-Rhamnose Synthesis-Deficient Mutant ofStreptococcus mutansin the Presence of Sucrose
Authors: Yamashita Yoshihisa , Tomihisa Kiyotaka , Nakano Yoshio , Shimazaki Yoshihiro , Oho Takahiko , Koga Toshihiko 
Published: December 2019

ABSTRACTThermlgenes are involved in dTDP-rhamnose synthesis inStreptococcus mutans. A gene fusion betweengtfBandgtfC, which both encode extracellular water-insoluble glucan-synthesizing enzymes, accompanied by inactivation of thermlgenes was observed for cells grown in the presence of sucrose. The survival rates ofrmlmutants isolated in the absence of sucrose were drastically reduced in the presence of sucrose. The rates were consistent with the frequency of spontaneous gene fusions betweengtfBandgtfC, suggesting that the spontaneous recombinant organisms were selected in the presence of sucrose. Thermlmutants with agtfB-gtfCfusion gene had markedly reduced water-insoluble glucan synthetic activity and lost the ability to colonize glass surfaces in the presence of sucrose. These results suggest that thermlmutants ofS. mutans, which are defective in dTDP-rhamnose synthesis, can survive only in the absence of water-insoluble glucan synthesis.
Vibrio cholerae
Intestinal Population Dynamics in the Suckling Mouse Model of Infection
Authors: Angelichio Michael J. , Spector Jonathon , Waldor Matthew K. , Camilli Andrew 
Published: December 2019

ABSTRACT

The suckling mouse has been used as a model to identify
Vibrio cholerae
intestinal colonization factors for over two decades, yet little is known about the location of recoverable organisms along the gastrointestinal (GI) tract following intragastric inoculation. In the present study, we determined the population dynamics of wild-type and avirulent mutant derivatives of both classical and El Tor biotype strains throughout the entire suckling mouse GI tract at various times after intragastric inoculation. Wild-type strains preferentially colonized the middle small bowel with a sharp demarcation between more proximal segments which had manyfold-fewer recoverable cells. Surprisingly, large and stable populations of viable cells were also recovered from the cecum and large bowel. Strains lacking toxin-coregulated pili (TCP
−
) were cleared from the small bowel; however, an El Tor TCP
−
strain colonized the cecum and large bowel almost as well as the wild-type strain. Strains lacking lipopolysaccharide O antigen (OA
−
) were efficiently cleared from the small bowel at early times but then showed net growth for the remainder of the infections. Moreover, large populations of the OA
−
strains were maintained in the large bowel. These results show that for the El Tor biotype neither TCP nor OA is required for colonization of the suckling mouse large bowel. Finally, similar percent recoveries of wild-type, TCP
−
, and OA
−
strains from the small bowel at an early time after infection suggest that TCP and OA are not required for strains of either biotype to resist bactericidal mechanisms in the suckling mouse GI tract.
Target Cell Range of
Haemophilus ducreyi
Hemolysin and Its Involvement in Invasion of Human Epithelial Cells
Authors: Wood Gwendolyn E. , Dutro Susan M. , Totten Patricia A. 
Published: December 2019

ABSTRACT

Haemophilus ducreyi
, the causative agent of chancroid, produces a hemolysin, whose role in virulence is not well defined. To assess the possible role of hemolysin in pathogenesis, we evaluated its target cell range by using wild-type
H. ducreyi
35000, nonhemolytic mutants with the hemolysin structural gene deleted, and isogenic strains expressing different amounts of hemolytic activity. The cytotoxicity of the various cell types was assessed by quantitating the release of lactate dehydrogenase into culture supernatants as a measure of cell lysis. In these experiments, human foreskin fibroblasts, human foreskin epithelial cells, and, to a lesser extent, HEp-2 cells were lysed by
H. ducreyi
hemolysin. Hemolysin also lysed human blood mononuclear cells and immune system cell lines including U937 macrophage-like cells, T lymphocytes, and B lymphocytes. In contrast, human polymorphonuclear leukocytes were not sensitive to hemolysin under the conditions tested. We also analyzed the effect of hemolysin on invasion of human epithelial cells and found that
H. ducreyi
strains expressing cloned hemolysin genes showed a 10-fold increase in invasion compared to the control strain. These data support the hypothesis that the
H. ducreyi
hemolysin is important in the pathogenesis of chancroid and may contribute to ulcer formation, invasion of epithelial cells, and evasion of the immune response.
Predominance of CD4 Th1 and CD8 Tc1 Cells Revealed by Characterization of the Cellular Immune Response Generated by Immunization with a DNA Vaccine Containing aTrypanosoma cruziGene
Authors: Rodrigues Mauricio M. , Ribeirão Marcelo , Pereira-Chioccola Vera , Renia Laurent , Costa Fabio 
Published: December 2019

ABSTRACTImmunization with a plasmid DNA containing the gene encoding the catalytic domain oftrans-sialidase (TS) elicits protective immune responses against experimentalTrypanosoma cruziinfection. As several studies provided strong evidence that during infection CD4 Th1 and CD8 T cytotoxic type 1 (Tc1) cells are important factors in host resistance, the present study was designed to evaluate which T-cell types were activated in DNA-vaccinated BALB/c mice. We found that bulk cells from DNA-immunized mice had CD4 and CD8 T cells that produced gamma interferon (IFN-γ) but not interleukin-4 (IL-4) or IL-10. To characterize the TS-specific T cells at the clonal level, we generated CD4 and CD8 clones. We obtained cytotoxic CD4 clones of the Th1 type that secreted large amounts of IFN-γ but not IL-4 or IL-10. Unexpectedly, we obtained other CD4 clones with a Th2 phenotype, secreting IL-4 and IL-10 but not IFN-γ. All CD8 clones were cytotoxic and produced IFN-γ. IL-4 and IL-10 were not secreted by these cells. Using synthetic peptides, we determined a CD8 epitope recognized by several clones as being represented by amino acids IYNVGQVSI. The antiparasitic activity of a CD4 Th1 and a CD8 Tc1 clone was assessed in vitro. CD4 or CD8 T cells significantly inhibitedT. cruzidevelopment in infected macrophages or fibroblasts, respectively. We concluded that DNA vaccine efficiently generates potentially protective CD4 Th1 and CD8 Tc1 cells specific for aT. cruziantigen, therefore reinforcing the possibility of using this strategy for developing a preventive or therapeutic vaccine against Chagas’ disease.