bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of Contact Lens Wear, Bacterial Flora, and Mannose-Induced Pathogenic Protease in the Pathogenesis of Amoebic Keratitis
Authors: Alizadeh Hassan , Neelam Sudha , Hurt Michael , Niederkorn Jerry Y. 
Published: January 2005

ABSTRACT

The ocular surface is continuously exposed to potential pathogens, including free-living amoebae.
Acanthamoeba
species are among the most ubiquitous amoebae, yet
Acanthamoeba
keratitis is remarkably rare. The pathogenesis of
Acanthamoeba
keratitis is a complex, sequential process. Here we show that
Acanthamoeba
keratitis is profoundly affected by mannosylated proteins on the ocular surface, which stimulate the amoebae to elaborate a 133-kDa pathogenic protease. The mannose-induced protease (MIP133) mediates apoptosis of the corneal epithelium, facilitates corneal invasion, and degrades the corneal stroma. We show that contact lens wear upregulates mannosylated proteins on the corneal epithelium, stimulates MIP133 secretion, and exacerbates corneal disease.
Corynebacterium xerosis
, a constituent of the ocular flora, contains large amounts of mannose and is associated with
Acanthamoeba
keratitis. The present results show that amoebae exposed to
C. xerosis
produce increased amounts of MIP133 and more severe corneal disease. Oral immunization with MIP133 mitigates
Acanthamoeba
keratitis and demonstrates the feasibility of antidisease vaccines for pathogens that resist immune elimination.
Murine Macrophage Transcriptional Responses to
Bacillus anthracis
Infection and Intoxication
Authors: Bergman Nicholas H. , Passalacqua Karla D. , Gaspard Renee , Shetron-Rama Lynne M. , Quackenbush John , Hanna Philip C. 
Published: January 2005

ABSTRACT

Interactions between
Bacillus anthracis
and host macrophages represent critical early events in anthrax pathogenesis, but their details are not clearly understood. Here we report the first genomewide characterization of the transcriptional changes within macrophages infected with
B. anthracis
and the identification of several hundred host genes that were differentially expressed during this intracellular stage of infection. These loci included both genes that are known to be regulated differentially in response to many other bacterial pathogens and those that appear to be differentially regulated in response to
B. anthracis
but not other bacterial species that have been tested. These data provide a transcriptional basis for a variety of physiological changes observed during infection, including the induction of apoptosis caused by the infecting bacteria. The expression patterns underlying
B. anthracis
-induced apoptosis led us to test further the importance of one very highly induced macrophage gene, that for ornithine decarboxylase. Our data show that this enzyme plays an important and previously unrecognized role in suppressing apoptosis in
B. anthracis
-infected cells. We have also characterized the transcriptional response to anthrax lethal toxin in activated macrophages and found that, following toxin treatment, many of the host inflammatory response pathways are dampened. These data provide insights into
B. anthracis
pathogenesis as well as potential leads for the development of new diagnostic and therapeutic options.
Murein Lipoprotein Is a Critical Outer Membrane Component Involved inSalmonella entericaSerovar Typhimurium Systemic Infection
Authors: Fadl A. A. , Sha J. , Klimpel G. R. , Olano J. P. , Niesel D. W. , Chopra A. K. 
Published: January 2005

ABSTRACTLipopolysaccharide (LPS) and Braun (murein) lipoprotein (Lpp) are major components of the outer membrane of gram-negative enteric bacteria that function as potent stimulators of inflammatory and immune responses. In a previous paper, we provided evidence that two functional copies of the lipoprotein gene (lppAandlppB) located on the chromosome ofSalmonella entericaserovar Typhimurium contributed to bacterial virulence. In this study, we characterizedlppAandlppBsingle-knockout (SKO) mutants and compared them with anlppdouble-knockout (DKO) mutant using in vitro and in vivo models. Compared to thelppDKO mutant, which was nonmotile, the motility of thelppSKO mutants was significantly increased (73 to 77%), although the level of motility did not reach the level of wild-type (WT)S. entericaserovar Typhimurium. Likewise, the cytotoxicity was also significantly increased when T84 human intestinal epithelial cells and RAW264.7 murine macrophages were infected with thelppSKO mutants compared to the cytotoxicity when cells were infected with thelppDKO mutant. The level of interleukin-8 (IL-8) in polarized T84 cells infected with thelppBSKO mutant was significantly higher (two- to threefold higher), reaching the level in cells infected with WTS. entericaserovar Typhimurium, than the level in host cells infected with thelppASKO mutant. ThelppDKO mutant induced minimal levels of IL-8. Similarly, sera from mice infected with thelppBSKO mutant contained 4.5- to 10-fold-higher levels of tumor necrosis factor-α and IL-6; the levels of these cytokines were 1.7- to 3.0-fold greater in thelppASKO mutant-infected mice than in animals challenged with thelppDKO mutant. The increased cytokine levels observed with thelppBSKO mutant in mice correlated with greater tissue damage in the livers and spleens of these mice than in the organs of animals infected with thelppASKO andlppDKO mutants. Moreover, thelppBSKO mutant-infected mice had increased susceptibility to death. Since thelppDKO mutant retained intact LPS, we constructed anS. entericaserovar Typhimurium triple-knockout (TKO) mutant in which thelppAandlppBgenes were deleted from an existingmsbBmutant (msbBencodes an enzyme required for the acylation of lipid A). Compared to thelppDKO andmsbBSKO mutants, thelpp-msbBTKO mutant was unable to induce cytotoxicity and to produce cytokines and chemokines in vitro and in vivo. These studies provided the first evidence of the relative contributions of Lpp and lipid A acylation toSalmonellapathogenesis.
Phagosomal Processing ofMycobacterium tuberculosisAntigen 85B Is Modulated Independently of Mycobacterial Viability and Phagosome Maturation
Authors: Ramachandra Lakshmi , Smialek Jamie L. , Shank Sam S. , Convery Marilyn , Boom W. Henry , Harding Clifford V. 
Published: January 2005

ABSTRACTControl ofMycobacterium tuberculosisinfection requires CD4 T-cell responses and major histocompatibility complex class II (MHC-II) processing ofM. tuberculosisantigens (Ags). We have previously demonstrated that macrophages process heat-killed (HK)M. tuberculosismore efficiently than liveM. tuberculosis. These observations suggested that liveM. tuberculosismay inhibit Ag processing by inhibiting phagosome maturation or that HKM. tuberculosismay be less resistant to Ag processing. In the present study we examined the correlation betweenM. tuberculosisviability and phagosome maturation and efficiency of Ag processing. Since heat treatment could renderM. tuberculosisAgs more accessible to proteolysis,M. tuberculosiswas additionally killed by antibiotic treatment and radiation. Processing of HK, live, radiation-killed (RadK), or rifampin-killed (RifK)M. tuberculosisin activated murine bone marrow macrophages was examined by using an I-Ab-restricted T-cell hybridoma cell line (BB7) that recognizes an epitope derived from Ag 85B. Macrophages processed HKM. tuberculosismore rapidly and efficiently than they processed live, RadK, or RifKM. tuberculosis. Live, RadK, and RifKM. tuberculosiscells were processed with similar efficiencies for presentation to BB7 T hybridoma cells. Furthermore, phagosomes containing live or RadKM. tuberculosisexpressed fewerM. tuberculosispeptide-MHC-II complexes than phagosomes containing HKM. tuberculosisexpressed. Since only liveM. tuberculosiswas able to prevent acidification of the phagosome, our results suggest that regulation of phagosome maturation does not explain the differences in processing of different forms ofM. tuberculosis. These findings suggest that the mechanisms used byM. tuberculosisto inhibit phagosomal maturation differ from the mechanisms involved in modulating phagosome Ag processing.
The Capsular Polysaccharide ofBurkholderia pseudomalleiContributes to Survival in Serum by Reducing Complement Factor C3b Deposition
Authors: Reckseidler-Zenteno Shauna L. , DeVinney Rebekah , Woods Donald E. 
Published: January 2005

ABSTRACTBurkholderia pseudomalleiproduces an extracellular polysaccharide capsule -3)-2-O-acetyl-6-deoxy-β-d-manno-heptopyranose-(1- which has been shown to be an essential virulence determinant. The addition of purified capsule was shown to increase the virulence of a capsule mutant strain in the Syrian hamster model of acute melioidosis. An increase in the number of wild-typeB. pseudomalleicells in the blood was seen by 48 h, while the number of capsule mutant cells in the blood declined by 48 h. Capsule expression was shown to be induced in the presence of serum using aluxreporter fusion to the capsule genewcbB. The addition of purifiedB. pseudomalleicapsule to serum bactericidal assays increased the survival ofB. pseudomalleiSLR5, a serum-sensitive strain, by 1,000-fold in normal human serum. Capsule production byB. pseudomalleicontributed to reduced activation of the complement cascade by reducing the levels of complement factor C3b deposition. An increase in phagocytosis of the capsule mutant compared to the wild type was observed in the presence of normal human serum. These results suggest that the production of this capsule contributes to resistance to phagocytosis by reducing C3b deposition on the surface of the bacterium, thereby contributing to the persistence of bacteria in the blood of the infected host. Continued studies to characterize this capsule are essential for understanding the pathogenesis ofB. pseudomalleiinfections and the development of preventive strategies for treatment of this disease.
Localized Multigene Expression Patterns Support an Evolving Th1/Th2-Like Paradigm in Response to Infections withToxoplasma gondiiandAscaris suum
Authors: Dawson Harry D. , Beshah Ethiopia , Nishi Sandra , Solano-Aguilar Gloria , Morimoto Motoko , Zhao Aiping , Madden Kathleen B. , Ledbetter Tonya K. , Dubey J. P. , Shea-Donohue Terez , Lunney Joan K. , Urban Joseph F. 
Published: January 2005

ABSTRACTHuman infectious diseases have been studied in pigs because the two species have common microbial, parasitic, and zoonotic organisms, but there has been no systematic evaluation of cytokine gene expression in response to infectious agents in porcine species. In this study, pigs were inoculated with two clinically and economically important parasites,Toxoplasma gondiiandAscaris suum, and gene expression in 11 different tissues for 20 different swine Th1/Th2-related cytokines, cytokine receptors, and markers of immune activation were evaluated by real-time PCR. A generalized Th1-like pattern of gene expression was evident in pigs infected withT. gondii, along with an increased anti-inflammatory gene expression pattern during the recovery phase of the infection. In contrast, an elevated Th2-like pattern was expressed during the period of expulsion ofA. suumfourth-stage larvae from the small intestine of pigs, along with low-level Th1-like and anti-inflammatory cytokine gene expression. Prototypical immune and physiological markers of infection were observed in bronchial alveolar lavage cells, small intestinal smooth muscle, and epithelial cells. This study validated the use of a robust quantitative gene expression assay to detect immune and inflammatory markers at multiple host tissue sites, enhanced the definition of two important swine diseases, and supported the use of swine as an experimental model for the study of immunity to infectious agents relevant to humans.
The Region Comprising Amino Acids 100 to 255 ofNeisseria meningitidisLipoprotein GNA 1870 Elicits Bactericidal Antibodies
Authors: Giuliani Marzia Monica , Santini Laura , Brunelli Brunella , Biolchi Alessia , Aricò Beatrice , Di Marcello Federica , Cartocci Elena , Comanducci Maurizio , Masignani Vega , Lozzi Luisa , Savino Silvana , Scarselli Maria , Rappuoli Rino , Pizza Mariagrazia 
Published: January 2005

ABSTRACTGNA 1870 is a novel surface-exposed lipoprotein, identified by genome analysis ofNeisseria meningitidisstrain MC58, which induces bactericidal antibodies. Three sequence variants of the protein were shown to be sufficient to induce bactericidal antibodies against a panel of strains representative of the diversity of serogroup B meningococci. Here, we studied the antigenic and immunogenic properties of GNA 1870, which for convenience was divided into domains A, B, and C. The immune responses of mice immunized with each of the three variants were tested using overlapping peptides scanning the entire protein length and using recombinant fragments. We found that while most of the linear epitopes are located in the A domain, the bactericidal antibodies are directed against conformational epitopes located in the BC domain. This was also confirmed by the isolation of a bactericidal murine monoclonal antibody, which failed to recognize linear peptides on the A, B, and C domains separately but recognized a conformational epitope formed only by the combination of the B and C domains. Arginine in position 204 was identified as important for binding of the monoclonal antibody. The identification of the region containing bactericidal epitopes is an important step in the design of new vaccines against meningococci.
Mouse Model of Enteropathogenic
Escherichia coli
Infection
Authors: Savkovic Suzana D. , Villanueva Jennilee , Turner Jerrold R. , Matkowskyj Kristina A. , Hecht Gail 
Published: January 2005

ABSTRACT

Enteropathogenic
Escherichia coli
(EPEC) is an important cause of diarrhea in humans. EPEC infection of cultured intestinal epithelial cells induces attaching and effacing (A/E) lesions, alters intestinal ion transport, increases paracellular permeability, and stimulates inflammation. The lack of a small-animal model has restricted in vivo studies examining EPEC-host interactions. The aim of this study was to characterize the C57BL/6J mouse as a model of EPEC infection. We have shown that EPEC can adhere to and colonize the intestinal epithelium of C57BL/6J mice. Animal weight and water intake were not altered during 10 days of EPEC infection. The proximal colon of infected mice contained semisolid stool, with stool pellets forming only in the distal colon. In contrast, the entire colon of control mice contained formed stool. Microvillous effacement and actin rearrangement, characteristic of A/E lesions, were seen in the intestine of infected mice but not control mice. Histological assessment revealed increased numbers of lamina propria neutrophils with occasional crypt abscesses, intraepithelial lymphocytes, and goblet cells in the intestine of EPEC-infected mice. Altogether, these data suggest that the C57BL/6J mouse is susceptible to infection by EPEC and will provide a suitable in vivo model for studying the consequences of EPEC infection.
Long-Term Survival and Intracellular Replication of
Mycoplasma hominis
in
Trichomonas vaginalis
Cells: Potential Role of the Protozoon in Transmitting Bacterial Infection
Authors: Dessì Daniele , Delogu Giuseppe , Emonte Eleonora , Catania Maria Rosaria , Fiori Pier Luigi , Rappelli Paola 
Published: January 2005

ABSTRACT

The existence of a symbiotic relationship between
Trichomonas vaginalis
and
Mycoplasma hominis
, which is the first reported example of symbiosis between two obligate human pathogens, has been recently reported by our research group. In this work, we examined the cellular location of
M. hominis
in respect to
T. vaginalis
. By using gentamicin protection assays, double immunofluorescence, and confocal microscopy, we obtained strong evidence that
M. hominis
is located within protozoan cells. 5-Bromodeoxyuridine incorporation assays showed that intracellularly located mycoplasmas actively synthesize DNA. Our results demonstrate that
M. hominis
has the capability of entering trichomonad cells and of replicating inside the protozoon. These findings suggest that symbiosis might provide the bacteria, during human infection, with the capability to resist to environmental stresses, such as host defense mechanisms and pharmacological therapies.
Defective Phagocytosis in
Anaplasma phagocytophilum
- Infected Neutrophils
Authors: Garyu Justin W. A. , Choi Kyoung-seong , Grab Dennis J. , Dumler J. Stephen 
Published: January 2005

ABSTRACT

Anaplasma phagocytophilum
infection induces functional neutrophil changes. Using both
Candida albicans
and fluorescent-aggregate phagocytosis assays, we examined whether neutrophil and dimethyl sulfoxide-differentiated HL-60 cell infection impairs internalization.
A. phagocytophilum
infection significantly decreased phagocytosis compared to that of controls (
P
< 0.05). This further impairment of neutrophil function may promote opportunistic infections and exacerbate disease.
Long-Term Protection against Tuberculosis following Vaccination with a Severely Attenuated Double Lysine and Pantothenate Auxotroph ofMycobacterium tuberculosis
Authors: Sambandamurthy Vasan K. , Derrick Steven C. , Jalapathy Kripa V. , Chen Bing , Russell Robert G. , Morris Sheldon L. , Jacobs William R. 
Published: January 2005

ABSTRACTWe report the safety and immunogenicity of a double lysine and pantothenate auxotroph ofMycobacterium tuberculosisin mice. The ΔlysAΔpanCDmutant is completely attenuated in immunocompromised SCID and gamma interferon knockout mice yet induces short-term and long-term protection in immunocompetent and CD4-deficient mice following single-dose subcutaneous vaccination.
Salmonella
-Induced Filament Formation Is a Dynamic Phenotype Induced by Rapidly Replicating
Salmonella enterica
Serovar Typhimurium in Epithelial Cells
Authors: Birmingham Cheryl L. , Jiang Xiuju , Ohlson Maikke B. , Miller Samuel I. , Brumell John H. 
Published: January 2005

ABSTRACT

Salmonella enterica
serovar Typhimurium has the fascinating ability to form tubular structures known as
Salmonella
-induced filaments (Sifs) in host cells. Here, we show that the prevalence of the Sif phenotype in HeLa cells is affected by host cell density, growth, and the multiplicity of infection. Sif formation was observed in cells that displayed rapid intracellular bacterial replication and was found to be dynamic, being maximal 8 to 10 h postinfection and declining thereafter. The virulence factors SpvB and SseJ were found to negatively modulate Sif formation. Our findings demonstrate the complex and dynamic nature of the Sif phenotype.
Colonization of Gnotobiotic Piglets by a
luxS
Mutant Strain of
Escherichia coli
O157:H7
Authors: Jordan Dianna M. , Sperandio Vanessa , Kaper James B. , Dean-Nystrom Evelyn A. , Moon Harley W. 
Published: January 2005

ABSTRACT

Gnotobiotic piglets inoculated with
Escherichia coli
O157:H7, its
luxS
mutant derivative, or nonpathogenic
E. coli
were evaluated for attaching and effacing lesions. Although no differences in clinical symptoms were seen between pigs inoculated with the parent and those inoculated with the
luxS
mutant, the
luxS
mutant-inoculated pigs had a lower frequency of attaching and effacing lesions in the spiral colon than parent strain-inoculated pigs.
Modulation of an Outer Membrane Protease Contributes to the Virulence Defect of
Shigella flexneri
Strains Carrying a Mutation in the
virK
Locus
Authors: Wing Helen J. , Goldman Seth R. , Ally Shabeen , Goldberg Marcia B. 
Published: January 2005

ABSTRACT

The
Shigella
actin assembly protein IcsA is removed from the bacterial surface by the protease IcsP. We show that decreased intracellular spreading of
virK
::Tn
10
mutants is due in part to significant increases in IcsP and IcsP-mediated cleavage of IcsA and that IcsP expression is a critical determinant of
Shigella
virulence.
Identification of New
hmwA
Alleles from Nontypeable
Haemophilus influenzae
Authors: Ecevit I. Zafer , McCrea Kirk W. , Marrs Carl F. , Gilsdorf Janet R. 
Published: January 2005

ABSTRACT

High-molecular-weight proteins of
Haemophilus influenzae
mediate attachment to epithelial cells. Previous reports describe several allelic versions of
hmwA
genes that have different adherence properties. Here we report three new alleles of
hmwA
(
hmwA
from strain AAr96,
hmwA
from strain AAr105, and
hmwA
from strain G822), demonstrating the high degree of DNA variation of these genes among different strains.
Down-Regulation of the
kps
Region 1 Capsular Assembly Operon following Attachment of
Escherichia coli
Type 1 Fimbriae to
d
-Mannose Receptors
Authors: Schwan William R. , Beck Michael T. , Hultgren Scott J. , Pinkner Jerry , Woolever Nathan L. , Larson Thomas 
Published: January 2005

ABSTRACT

A differential-display PCR procedure identified the capsular assembly gene
kpsD
after
Escherichia coli
type 1 fimbrial binding to mannose-coated Sepharose beads. Limiting-dilution reverse-transcribed PCRs confirmed down-regulation of the
kpsD
gene, and Northern blot and
lacZ
fusion analyses showed down-regulation of the
kpsFEDUCS
region 1 operon. KpsD protein levels fell, and an agglutination test showed less K capsular antigen on the surface following the bacterial ligand-receptor interaction. These data show that binding of type 1 fimbriae (pili) to
d
-mannose receptors triggers a cross talk that leads to down-regulation of the capsule assembly region 1 operon in uropathogenic
E. coli
.
Plasmodium falciparum
Merozoite Surface Protein 6 Displays Multiple Targets for Naturally Occurring Antibodies That Mediate Monocyte-Dependent Parasite Killing
Authors: Singh Subhash , Soe Soe , Roussilhon Christian , Corradin Giampietro , Druilhe Pierre 
Published: January 2005

ABSTRACT

Plasmodium falciparum
MSP6 is a merozoite surface antigen that shows organization and sequence homologies similar to those of MSP3. Within its C-terminus conserved region, it presents some epitopes that are cross-reactive with MSP3 and others that are not, both being targets of naturally occurring antibodies that block the
P. falciparum
erythrocytic cycle in cooperation with monocytes.
CaNAT1
, a Heterologous Dominant Selectable Marker for Transformation of
Candida albicans
and Other Pathogenic
Candida
Species
Authors: Shen Junqing , Guo Weihui , Köhler Julia R. 
Published: January 2005

ABSTRACT

A dominant selectable marker for
Candida albicans
and other
Candida
species, which confers resistance to nourseothricin, was characterized. In a heterologous promoter system and a recyclable cassette, the marker efficiently permitted deletion and complementation of
C. albicans
genes. Neither growth nor filamentous development was affected in strains expressing this marker.
Interaction of Enteropathogenic
Escherichia coli
with Human Intestinal Mucosa: Role of Effector Proteins in Brush Border Remodeling and Formation of Attaching and Effacing Lesions
Authors: Shaw Robert K , Cleary Jennifer , Murphy Michael S. , Frankel Gad , Knutton Stuart 
Published: January 2005

ABSTRACT

Enteropathogenic
Escherichia coli
(EPEC) strains deliver effector proteins Tir, EspB, Map, EspF, EspH, and EspG into host cells to induce brush border remodeling and produce attaching and effacing (A/E) lesions on small intestinal enterocytes. In this study, the role of individual EPEC effectors in brush border remodeling and A/E lesion formation was investigated with an in vitro human small intestinal organ culture model of EPEC infection and specific effector mutants.
tir
,
map
,
espB
, and
espH
mutants produced “footprint” phenotypes due to close bacterial adhesion but subsequent loss of bacteria; an
espB
mutant and other type III secretion system mutants induced a “noneffacing footprint” associated with intact brush border microvilli, whereas a
tir
mutant was able to efface microvilli resulting in an “effacing footprint”;
map
and
espH
mutants produced A/E lesions, but loss of bacteria resulted in a “pedestal footprint.” An
espF
mutant produced typical A/E lesions without associated microvillous elongation. An
espG
mutant was indistinguishable from the wild type. These observations indicate that Tir, Map, EspF, and EspH effectors play a role in brush border remodeling and production of mature A/E lesions.