bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inoculum Composition and
Salmonella
Pathogenicity Island 1 Regulate M-Cell Invasion and Epithelial Destruction by
Salmonella typhimurium
Authors: Clark M. Ann , Hirst Barry H. , Jepson Mark A. 
Published: December 2019

ABSTRACT

In the mouse model of
Salmonella typhimurium
infection, the specialized antigen-sampling intestinal M cells are the primary route of
Salmonella
invasion during the early stages of infection. Under certain experimental conditions, M-cell invasion is accompanied by M-cell destruction and loss of adjacent regions of the follicle-associated epithelium (FAE), although the conditions responsible for expression of the cytotoxic phenotype in a proportion of previous studies have not been defined. In the present study, we have demonstrated that the cytotoxic effect exerted by wild-type
S. typhimurium
on mouse Peyer’s patch FAE is dependent on the inoculum composition. We have also demonstrated that the extent of FAE destruction correlates with the extent of M-cell invasion. Bacteria inoculated in Luria-Bertani (LB) broth induce extensive FAE loss and exhibit efficient M-cell invasion, whereas bacteria inoculated in phosphate-buffered saline fail to induce significant FAE disruption and invade M cells at significantly lower levels. Similarly, inoculation in LB significantly enhances invasion of Madin-Darby canine kidney cells by wild-type
S. typhimurium
. Mutants defective for expression of
invA
, a component of
Salmonella
pathogenicity island 1 which is vital for efficient invasion of cultured cells, fail to induce FAE destruction and, when inoculated in LB, are attenuated for M-cell invasion. Variation in
inv
gene expression is, therefore, one possible mechanism by which inoculate composition may regulate the virulence of wild-type
S. typhimurium
. Our findings suggest that the composition of the gut luminal contents may be critical in determining the outcome of naturally acquired
Salmonella
infections and that both vaccine formulation and dietary status of vaccine recipients may significantly affect the efficacy and safety of live
Salmonella
oral vaccine delivery systems.
Protective Role of Gamma Interferon in Experimental Pulmonary Paracoccidioidomycosis
Authors: Cano Luz E. , Kashino Suely S. , Arruda Celina , André Denise , Xidieh Cynthia F. , Singer-Vermes Lucia M. , Vaz Celidéia A. C. , Burger Eva , Calich Vera L. G. 
Published: December 2019

ABSTRACTWe have developed a murine model of pulmonary infection byParacoccidioides brasiliensisin which resistance was associated with immunological activities governed by gamma interferon (IFN-γ). To better characterize this model, we measured type 1 and type 2 cytokines in the lungs and investigated the effect of endogenous IFN-γ depletion by monoclonal antibodies in the course of infection of susceptible (B10.A) and resistant (A/Sn) mice. At weeks 4 and 8 after infection, lungs from susceptible animals presented levels of IFN-γ, interleukin-4 (IL-4), IL-5, and IL-10 higher than those in resistant mice. In both mouse strains, neutralization of endogenous IFN-γ induced exacerbation of the pulmonary infection, earlier fungal dissemination to the liver and spleen, impairment of the specific cellular immune response resulting in significantly lower delayed-type hypersensitivity reactions, and increased levels of immunoglobulin G1 (IgG1)- and IgG2b-specific antibodies. Histopathological analysis demonstrated that depletion of IFN-γ changes the focal granulomatous lesions found in the lungs of B10.A and A/Sn mice into coalescent granulomata which destroy the pulmonary architecture. These results suggest that irrespective of the mouse strain, IFN-γ plays a protective role and that this cytokine is one major mediator of resistance againstP. brasiliensisinfection in mice.
Adherence of
Streptococcus pneumoniae
to Human Bronchial Epithelial Cells (BEAS-2B)
Authors: Adamou John E. , Wizemann Theresa M. , Barren Philip , Langermann Solomon 
Published: December 2019

ABSTRACT

Pneumococcal adherence to alveolar epithelial cells and nasopharyngeal epithelial cells has been well characterized. However, the interaction of
Streptococcus pneumoniae
with bronchial epithelial cells has not been studied. We have now shown that pneumococci bind specifically to a human bronchial epithelial cell line (BEAS-2B cells). Pneumococci adhered to BEAS-2B cells in a time- and dose-dependent manner. These results suggest that the bronchial epithelium may serve as an additional site of attachment for pneumococci and demonstrate the utility of the BEAS-2B cell line for studying mechanisms of pneumococcal infection.
Use of Representational Difference Analysis To Identify Genomic Differences between Pathogenic Strains of
Vibrio cholerae
Authors: Calia Kerstin E. , Waldor Matthew K. , Calderwood Stephen B. 
Published: December 2019

ABSTRACT

Representational difference analysis (RDA) is a recently developed technique used for amplifying genetic differences between two closely related genomes. We compared RDA and a modified version of RDA to examine genomic differences between the two
Vibrio cholerae
serogroups that cause epidemic cholera, O1 and O139, and between the two biotypes of the O1 serogroup. With both techniques, we recovered several sequences known to be found only in
V. cholerae
O139 but absent in its presumed progenitor,
V. cholerae
O1 El Tor. A greater number of unique fragments were generated in comparing the two
V. cholerae
O1 biotypes, consistent with the probable greater genetic differences between the two biotypes.
The
Pseudomonas aeruginosa
Flagellar Cap Protein, FliD, Is Responsible for Mucin Adhesion
Authors: Arora Shiwani K. , Ritchings Bruce W. , Almira Ernesto C. , Lory Stephen , Ramphal Reuben 
Published: December 2019

ABSTRACT

Mucin-specific adhesion of
Pseudomonas aeruginosa
plays an important role in the initial colonization of this organism in the airways of cystic fibrosis patients. We report here that the flagellar cap protein, FliD, participates in this adhesion process. A polar chromosomal insertional mutation in the
P. aeruginosa fliD
gene made this organism nonadhesive to mucin in an in vitro mucin adhesion assay. The adhesive phenotype was restored by providing the
fliD
gene alone on a multicopy plasmid, suggesting involvement of this gene in mucin adhesion of
P. aeruginosa
. Further supporting this observation, the in vitro competition experiments demonstrated that purified FliD protein inhibited the mucin adhesion of nonpiliated
P. aeruginosa
PAK-NP, while the same concentrations of PilA and FlaG proteins of
P. aeruginosa
were ineffective in this function. The regulation of the
fliD
gene was studied and was found to be unique in that the transcription of the
fliD
gene was independent of the flagellar sigma factor ς
28
. Consistent with this finding, no ς
28
binding sequence could be identified in the
fliD
promoter region. The results of the β-galactosidase assays suggest that the
fliD
gene in
P. aeruginosa
is regulated by the newly described transcriptional regulator FleQ and the alternate sigma factor ς
54
(RpoN).
Nonopsonic Phagocytosis of Group C
Neisseria meningitidis
by Human Neutrophils
Authors: Estabrook Michele M. , Zhou Daoguo , Apicella Michael A. 
Published: December 2019

ABSTRACT

Although complement-mediated bactericidal activity in serum has long been known to be very important in host defense against
Neisseria meningitidis
, recent studies have shown that opsonic phagocytosis by neutrophils is also important. The purpose of this study was to determine if endemic group C
N. meningitidis
strains were susceptible to nonopsonic (complement- and antibody-independent) phagocytosis by human neutrophils, which is a well-described phenomenon for
Neisseria gonorrhoeae
. Gonococci that possess one or more of a group of heat-modifiable outer membrane proteins (called opacity-associated [Opa] proteins) are phagocytosed by neutrophils in the absence of serum. We found that four serogroup C meningococcal strains bearing the lacto-
N
-neotetraose (LNnT) structure on lipooligosaccharide (LOS) were phagocytosed by neutrophils in the absence of antibody and active complement. Confocal microscopy confirmed that the organisms were internalized by neutrophils. This susceptibility was not restricted to carrier isolates, since two of the strains were cultured from blood or cerebrospinal fluid. All four strains expressed Opa protein and had relatively less endogenous LOS and capsule sialylation compared to six strains that were resistant to this type of phagocytosis. Nonopsonic phagocytosis of two of the four strains was inhibited by exogenous sialylation of LOS LNnT and the binding of monoclonal antibody to LNnT. However, an isogenic mutant that lacked the LNnT structure was fully susceptible to nonopsonic phagocytosis. We conclude that group C meningococci can be phagocytosed by neutrophils in the absence of antibody and active complement possibly by two different mechanisms. Expression of Opa protein and downregulation of endogenous surface sialic acids analogous to what is seen for
N. gonorrhoeae
might be necessary for
N. meningitidis
as well.
M-Cell Surface β1 Integrin Expression and Invasin-Mediated Targeting of
Yersinia pseudotuberculosis
to Mouse Peyer’s Patch M Cells
Authors: Clark M. Ann , Hirst Barry H. , Jepson Mark A. 
Published: December 2019

ABSTRACT

Quantitative analysis of
Yersinia pseudotuberculosis
infection of murine gut loops revealed that significantly more wild-type bacteria associated with Peyer’s patch M cells than with dome enterocytes or goblet cells. An invasin-deficient mutant was significantly attenuated for M-cell invasion, while β1 integrin expression was demonstrated in the apical membranes of M cells but not enterocytes. M-cell targeting by
Yersinia pseudotuberculosis
in vivo may, therefore, be mediated primarily by the interaction of invasin with cell surface β1 integrins.
Expression of Heat-Stable Enterotoxin STb by AdherentEscherichia coliIs Not Sufficient To Cause Severe Diarrhea in Neonatal Pigs
Authors: Casey Thomas A. , Herring Cheryl J. , Schneider Robert A. , Bosworth Brad T. , Whipp Shannon C. 
Published: December 2019

ABSTRACTThe role ofEscherichia coliheat-stable enterotoxin B (STb) in neonatal porcine diarrhea caused by enterotoxigenicE. coliwas examined by comparing adherent isogenic strains with or without STb. The cloned STb gene (in the plasmid pRAS1) was electroporated into a nonenterotoxigenic strain (226M) which expresses the F41 adhesin. Strain 226M pRAS1 adhered and expressed STb in vivo, causing fluid secretion in ligated ileal loops in neonatal pigs. Although strain 226M pRAS1 caused very mild diarrhea in some orally inoculated neonatal pigs, the weight loss in these pigs was similar to that caused by the parental strain without STb. We conclude that STb does not significantly contribute to diarrhea caused by enterotoxigenicE. coliin neonatal pigs.
The
Haemophilus influenzae
HtrA Protein Is a Protective Antigen
Authors: Loosmore Sheena M. , Yang Yan-ping , Oomen Ray , Shortreed Jean M. , Coleman Debbie C. , Klein Michel H. 
Published: December 2019

ABSTRACT

The
htrA
gene from two strains of nontypeable
Haemophilus influenzae
has been cloned and sequenced, and the encoded approximately 46-kDa HtrA proteins were found to be highly conserved.
H. influenzae
HtrA has approximately 55% identity with the
Escherichia coli
and
Salmonella typhimurium
HtrA stress response proteins, and expression of the
H. influenzae htrA
gene was inducible by high temperature. Recombinant HtrA (rHtrA) was expressed from
E. coli
, and the purified protein was found to have serine protease activity. rHtrA was found to be very immunogenic and partially protective in both the passive infant rat model of bacteremia and the active chinchilla model of otitis media. Immunoblot analysis indicated that HtrA is antigenically conserved in encapsulated and nontypeable
H. influenzae
species. Site-directed mutagenesis was performed on the
htrA
gene to ablate the endogenous serine protease activity of wild-type HtrA, and it was found that eight of nine recombinant mutant proteins had no measurable residual proteolytic activity. Two mutant proteins were tested in the animal protection models, and one, H91A, was found to be partially protective in both models. H91A HtrA may be a good candidate antigen for a vaccine against invasive
H. influenzae
type b disease and otitis media and is currently in phase I clinical trials.
Protein Deficiency Induces Alterations in the Distribution of T-Cell Subsets in Experimental Pulmonary Tuberculosis
Authors: Mainali Elsie S. , McMurray David N. 
Published: December 2019

ABSTRACT

Previous research has suggested that dietary protein deficiency alters resistance to experimental pulmonary tuberculosis, in part, by affecting the distribution and trafficking of antigen-reactive T cells. In this study, guinea pigs were maintained on either a protein-deficient (10% ovalbumin) or control (30% ovalbumin) diet and infected 4 to 6 weeks later with a low dose of virulent
Mycobacterium tuberculosis
H37Rv by the respiratory route. Monoclonal antibodies directed against the CD4 or CD8 markers on guinea pig lymphocytes were used in a flow cytofluorometric assay to determine the proportion of each subset in the peripheral circulation, spleen, and bronchotracheal lymph nodes at 4 weeks after infection. In uninfected guinea pigs, only the spleen exhibited an effect of diet on T-cell distribution, with small but consistent reductions in the proportions of both CD4 and CD8 T lymphocytes. However, following infection, protein deficiency exerted a profound effect on T-cell distribution. Malnourished, tuberculous guinea pigs harbored only 20 and 60% of the T cells (as a proportion of total lymphoid cells) found in the spleen and blood, respectively, of their well-nourished counterparts. Normal relative proportions of CD4 and CD8 cells were observed, however. In striking contrast, the bronchotracheal lymph nodes of protein-deprived guinea pigs with tuberculosis contained more than twice the numbers of T cells of control guinea pigs, and the normal CD4-to-CD8 ratio was reversed. Peripheral T-cell function, as measured by the delayed hypersensitivity skin test to tuberculin, and antigen-induced lymphoproliferation in vitro were markedly suppressed in protein-malnourished animals. Conversely, purified protein derivative-induced (but not concanavalin A-induced) proliferation was significantly enhanced in cultures of lymph node cells from protein-deprived tuberculous animals. Taken together, these results suggest that immunological abnormalities and loss of antimycobacterial resistance in the lungs of protein-deficient guinea pigs may be explained, in part, by sequestration of antigen-reactive T cells in the lymph nodes draining the site of infection.
Mutation in the
peb1A
Locus of
Campylobacter jejuni
Reduces Interactions with Epithelial Cells and Intestinal Colonization of Mice
Authors: Pei Zhiheng , Burucoa Christophe , Grignon Bernadette , Baqar Shahida , Huang Xiao-Zhe , Kopecko Dennis J. , Bourgeois A. L. , Fauchere Jean-Louis , Blaser Martin J. 
Published: December 2019

ABSTRACT

Campylobacter jejuni
is one of the leading causes of bacterial diarrhea throughout the world. We previously found that PEB1 is a homolog of cluster 3 binding proteins of bacterial ABC transporters and that a
C. jejuni
adhesin, cell-binding factor 1 (CBF1), if not identical to, contains PEB1. A single protein migrating at approximately 27 to 28 kDa was recognized by anti-CBF1 and anti-PEB1. To determine the role that the operon encoding PEB1 plays in
C. jejuni
adherence,
peb1A
, the gene encoding PEB1, was disrupted in strain 81-176 by insertion of a kanamycin resistance gene through homologous recombination. Inactivation of this operon completely abolished expression of CBF1, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. In comparison to the wild-type strain, the mutant strain showed 50- to 100-fold less adherence to and 15-fold less invasion of epithelial cells in culture. Mouse challenge studies showed that the rate and duration of intestinal colonization by the mutant were significantly lower and shorter than with the wild-type strain. In summary, PEB1 is identical to a previously identified cell-binding factor, CBF1, in
C. jejuni
, and the
peb1A
locus plays an important role in epithelial cell interactions and in intestinal colonization in a mouse model.
Curli, Fibrous Surface Proteins ofEscherichia coli, Interact with Major Histocompatibility Complex Class I Molecules
Authors: Olsén Arne , Wick Mary Jo , Mörgelin Matthias , Björck Lars 
Published: December 2019

ABSTRACTCurli are thin, coiled fibers expressed on the surface ofEscherichia colithat bind several matrix and plasma proteins such as fibronectin, laminin, plasminogen, tissue plasminogen activator, and H-kininogen. In this work, we examined the interactions between curli-expressingE. coliand human major histocompatibility complex class I (MHC-I) and class II (MHC-II) molecules. CurliatedE. coliwas found to interact with an MHC-I-expressing lymphoma cell line as shown by scanning electron microscopy, whereas the binding to a mutant variant of this cell line expressing small amounts of MHC-I molecules was significantly lower. Moreover, curli-expressingE. colibound purified radiolabeled MHC-I but not MHC-II molecules, whereas an isogenic curli-deficient mutant strain showed no affinity for either MHC-I or MHC-II. Purified insoluble curli could also bind125I-labeled MHC-I molecules, and in Western blot experiments the 15-kDa curlin subunit protein bound intact MHC-I molecules as well as β2-microglobulin, the light chain of MHC-I molecules. A direct interaction between monomeric MHC-I molecules and a bacterial surface protein has previously not been reported. The binding of curli to MHC-I molecules, which are present on virtually all cells in higher vertebrates, will provide curliatedE. coliwith ample opportunities to interact with a great variety of hosts and host cells. This should facilitate the adaptation ofE. colito different ecological niches, and in human infections the interaction between curli and MHC-I molecules could contribute to adherence and colonization.
Chlamydial Infection in Inducible Nitric Oxide Synthase Knockout Mice
Authors: Igietseme Joseph U. , Perry Linda L. , Ananaba Godwin A. , Uriri Ijindah M. , Ojior Omegbhai O. , Kumar Shantha N. , Caldwell Harlan D. 
Published: December 2019

ABSTRACTType 1 CD4+-T-cell-mediated immunity is crucial for the resolution of chlamydial infection of the murine female genital tract. Previous studies demonstrating a correlation between CD4+-T-cell-mediated inhibition of chlamydial growth and gamma interferon (IFN-γ)-mediated induction of nitric oxide synthase suggested a potential role for the nitric oxide (NO) effector pathway in the clearance ofChlamydiafrom genital epithelial cells by the immune system. To clarify the role of this pathway, the growth levels ofChlamydia trachomatisorganisms in normal (iNOS+/+) mice and in genetically engineered mice lacking the inducible nitric oxide synthase (iNOS) gene (iNOS−/−mice) were compared. There was no significant difference in the course of genital chlamydial infections in iNOS+/+and iNOS−/−mice as determined by recovery ofChlamydiaorganisms shed from genital epithelial cells. Dissemination ofChlamydiato the spleen and lungs occurred to a greater extent in iNOS−/−than in iNOS+/+mice, which correlated with a marginal increase in the susceptibility of macrophages from iNOS−/−mice to chlamydial infection in vitro. However, infections were rapidly cleared from all affected tissues, with no clinical signs of disease. The finding of minimal dissemination in iNOS−/−mice suggested that activation of the iNOS effector pathway was not the primary target of IFN-γ during CD4+-T-cell-mediated control of chlamydial growth in macrophages because previous reports demonstrated extensive and often fatal dissemination ofChlamydiain mice lacking IFN-γ. In summary, these results indicate that the iNOS effector pathway is not required for elimination ofChlamydiafrom epithelial cells lining the female genital tract of mice although it may contribute to the control of dissemination ofC. trachomatisby infected macrophages.
Toxoplasma gondiiTriggers Granulocyte-Dependent Cytokine-Mediated Lethal Shock ind-Galactosamine-Sensitized Mice
Authors: Marshall Anthony J. , Denkers Eric Y. 
Published: December 2019

ABSTRACTTo investigate the capacity ofToxoplasma gondiito induce cytokine-mediated toxicity, we employed a murine model of lethal shock in which hypersensitivity to microbial toxins is induced byd-galactosamine (d-Gal). Animals injected withd-Gal and tachyzoite lysate died within 12 to 24 h, whereas administration ofd-Gal or lysate alone was nonlethal. Analyses of plasma cytokines revealed peaks of tumor necrosis factor (TNF) alpha and interleukin-12 (IL-12) 1 and 3 to 5 h after injection, respectively, and gradually rising levels of gamma interferon (IFN-γ) continuing until death. Nitric oxide (NO) levels in serum paralleled IFN-γ production. Transaminase assays revealed elevated levels of liver-associated enzymes in sera of lethally injected mice, indicating severe hepatic damage. Depletion of IL-12, TNF, IFN-γ, and NO rescued mice from the lethal effect of antigen (Ag) andd-Gal. T-cell-deficient animals remained sensitive tod-Gal and lysate, suggesting that T lymphocytes do not contribute to the response. Nevertheless, monoclonal antibody (MAb)-mediated granulocyte depletion completely abrogatedd-Gal- and Ag-induced mortality and accompanying liver pathology. Finally, mice acutely infected withT. gondiidisplayed highly elevated NO and liver enzyme levels in serum immediately prior to death, and administration of anti-TNF MAb prolonged survival by approximately 24 h. Our results demonstrate thatT. gondiiinduces lethal inflammatory cytokine shock ind-Gal-sensitized animals and suggest that a similar pathology may contribute to manifestations of acute toxoplasmosis.
The N-Terminal Part of the Enzyme Component (C2I) of the Binary
Clostridium botulinum
C2 Toxin Interacts with the Binding Component C2II and Functions as a Carrier System for a Rho ADP-Ribosylating C3-Like Fusion Toxin
Authors: Barth H. , Hofmann F. , Olenik C. , Just I. , Aktories K. 
Published: December 2019

ABSTRACT

The binary actin–ADP-ribosylating
Clostridium botulinum
C2 toxin consists of the enzyme component C2I and the binding component C2II, which are separate proteins. The active component C2I enters cells through C2II by receptor-mediated endocytosis and membrane translocation. The N-terminal part of C2I (C2IN), which consists of 225 amino acid residues but lacks ADP-ribosyltransferase activity, was identified as the C2II contact site. A fusion protein (C2IN-C3) of C2IN and the full-length C3-like ADP-ribosyltransferase from
Clostridium limosum
was constructed. The fusion protein C2IN-C3 ADP-ribosylated Rho but not actin in CHO cell lysates. Together with C2II, C2IN-C3 induced complete rounding up of CHO and HeLa cells after incubation for 3 h. No cell rounding was observed without C2II or with the original C3-like transferase from
C. limosum
. The data indicate that the N-terminal 225 amino acid residues of C2I are sufficient to cause the cellular uptake of
C. limosum
transferase via the binding component of C2II, thereby increasing the cytotoxicity of the C3-like exoenzyme several hundred-fold.