bluuebunny/crossref_metadata_2025_split huggingface dataset:
Activation of Vα14+Natural Killer T Cells by α-Galactosylceramide Results in Development of Th1 Response and Local Host Resistance in Mice Infected withCryptococcus neoformans
Authors: Kawakami Kazuyoshi , Kinjo Yuki , Yara Satomi , Koguchi Yoshinobu , Uezu Kaori , Nakayama Toshinori , Taniguchi Masaru , Saito Atsushi 
Published: July 2002

ABSTRACTWe examined the effect of α-galactosylceramide (α-GalCer) on the synthesis of gamma interferon (IFN-γ) and local resistance in mice infected intravenously withCryptococcus neoformans. The level of IFN-γ in serum increased on day 3, reached a peak level on day 7, and decreased to the basal level on day 14 postinfection in mice treated with α-GalCer, while in vehicle-treated mice, no increase was detected at any time points except for a small increase on day 7. Such effects were not observed in NKT-KO mice. In CD4KO mice, minor synthesis of IFN-γ was detected on day 3 in sera but was completely abolished by day 7. The α-GalCer-induced IFN-γ production on day 3 was partially reduced in mice depleted of NK cells by treatment with anti-asialo-GM1antibody (Ab). Spleen cells obtained from infected and α-GalCer-treated mice on day 7 produced a large amount of IFN-γ upon restimulation with live organisms, while only a marginal level of production was detected in splenocytes from infected and vehicle-treated mice. Such effects were abolished in CD4KO and NKT-KO mice. Finally, the fungal loads in the lungs and spleen on days 7 and 14 were significantly reduced in α-GalCer-treated mice compared to those in control mice. In NKT-KO mice, local resistance elicited by α-GalCer was completely abolished, although no obvious exacerbation of infection was detected. Furthermore, treatment with anti-IFN-γ monoclonal Ab mostly abrogated the protective effect of this agent. Thus, our results indicated that activation of Vα14+NKT cells resulted in an increased Th1 response and local resistance toC. neoformansthrough production of IFN-γ.
Ferric Dicitrate Transport System (Fec) of
Shigella flexneri
2a YSH6000 Is Encoded on a Novel Pathogenicity Island Carrying Multiple Antibiotic Resistance Genes
Authors: Luck Shelley N. , Turner Sally A. , Rajakumar Kumar , Sakellaris Harry , Adler Ben 
Published: July 2002

ABSTRACT

Iron uptake systems which are critical for bacterial survival and which may play important roles in bacterial virulence are often carried on mobile elements, such as plasmids and pathogenicity islands (PAIs). In the present study, we identified and characterized a ferric dicitrate uptake system (Fec) in
Shigella flexneri
serotype 2a that is encoded by a novel PAI termed the
Shigella
resistance locus (SRL) PAI. The
fec
genes are transcribed in
S. flexneri
, and complementation of a
fec
deletion in
Escherichia coli
demonstrated that they are functional. However, insertional inactivation of
fecI
, leading to a loss in
fec
gene expression, did not impair the growth of the parent strain of
S. flexneri
in iron-limited culture media, suggesting that
S. flexneri
carries additional iron uptake systems capable of compensating for the loss of Fec-mediated iron uptake. DNA sequence analysis showed that the
fec
genes are linked to a cluster of multiple antibiotic resistance determinants, designated the SRL, on the chromosome of
S. flexneri
2a. Both the SRL and
fec
loci are carried on the 66,257-bp SRL PAI, which has integrated into the
serX
tRNA gene and which carries at least 22 prophage-related open reading frames, including one for a P4-like integrase. This is the first example of a PAI that carries genes encoding antibiotic resistance and the first report of a ferric dicitrate uptake system in
Shigella
.
Motility and Chemotaxis in Tissue Penetration of Oral Epithelial Cell Layers byTreponema denticola
Authors: Lux Renate , Miller James N. , Park No-Hee , Shi Wenyuan 
Published: July 2002

ABSTRACTThe ability to penetrate tissue is an important virulence factor for pathogenic spirochetes. Previous studies have recognized the role of motility in allowing pathogenic spirochetes to invade tissues and migrate to sites favorable for bacterial proliferation. However, the nature of the movements, whether they are random or controlled by chemotaxis systems, has yet to be established. In this study, we addressed the role of motility and chemotaxis in tissue penetration by the periodontal disease-associated oral spirocheteTreponema denticolausing an oral epithelial cell line-based experimental approach. Wild-typeT. denticolaATCC 35405 was found to penetrate the tissue layers effectively, whereas a nonmotile mutant was unable to overcome the tissue barrier. Interestingly, the chemotaxis mutants also showed impaired tissue penetration. AcheAmutant that is motile but lacks the central kinase of the chemotaxis pathway showed only about 2 to 3% of the wild-type penetration rate. The two known chemoreceptors ofT. denticola, DmcA and DmcB, also appear to be involved in the invasion process. Thedmcmutants were actively motile but exhibited reduced tissue penetration of about 30 and 10% of the wild-type behavior, respectively. These data suggest that not only motility but also chemotaxis is involved in the tissue penetration byT. denticola.
Characterization of Saa, a Novel Autoagglutinating Adhesin Produced by Locus of Enterocyte Effacement-Negative Shiga-Toxigenic
Escherichia coli
Strains That Are Virulent for Humans
Authors: Paton Adrienne W. , Srimanote Potjanee , Woodrow Matthew C. , Paton James C. 
Published: July 2002

ABSTRACT

The capacity of Shiga toxigenic
Escherichia coli
(STEC) to adhere to the intestinal mucosa undoubtedly contributes to pathogenesis of human disease. The majority of STEC strains isolated from severe cases produce attaching and effacing lesions on the intestinal mucosa, a property mediated by the locus of enterocyte effacement (LEE) pathogenicity island. This element is not essential for pathogenesis, as some cases of severe disease, including hemolytic uremic syndrome (HUS), are caused by LEE-negative STEC strains, but the mechanism whereby these adhere to the intestinal mucosa is not understood. We have isolated a gene from the megaplasmid of a LEE-negative O113:H21 STEC strain (98NK2) responsible for an outbreak of HUS, which encodes an auto-agglutinating adhesin designated Saa (STEC autoagglutinating adhesin). Introduction of
saa
cloned in pBC results in a 9.7-fold increase in adherence of
E. coli
JM109 to HEp-2 cells and a semilocalized adherence pattern. Mutagenesis of
saa
in 98NK2, or curing the wild-type strain of its megaplasmid, resulted in a significant reduction in adherence. Homologues of
saa
were found in several unrelated LEE-negative STEC serotypes, including O48:H21 (strain 94CR) and O91:H21 (strain B2F1), which were also isolated from patients with HUS. Saa exhibits a low degree of similarity (25% amino acid [aa] identity) with YadA of
Yersinia enterocolitica
and Eib, a recently described phage-encoded immunoglobulin binding protein from
E. coli
. Saa produced by 98NK2 is 516 aa long and includes four copies of a 37-aa direct repeat sequence. Interestingly, Saa produced by other STEC strains ranges in size from 460 to 534 aa as a consequence of variation in the number of repeats and/or other insertions or deletions immediately proximal to the repeat domain.
Relative Importance of NF-κB p50 in Mycobacterial Infection
Authors: Yamada Hiroyuki , Mizuno Satoru , Reza-Gholizadeh Mohammad , Sugawara Isamu 
Published: July 2002

ABSTRACTTo understand the role of NF-κB in the development of murine tuberculosis in vivo, NF-κB p50 knockout mice were infected withMycobacterium tuberculosisby placing them in the exposure chamber of an airborne-infection apparatus. These mice developed multifocal necrotic pulmonary lesions or lobar pneumonia. Compared with the levels in wild-type mice, pulmonary inducible nitric oxide synthase, interleukin-2 (IL-2), gamma interferon, and tumor necrosis factor alpha mRNA levels were significantly low but expression of IL-10 and transforming growth factor β mRNAs were within the normal ranges. The pulmonary IL-6 mRNA expression level was higher. Therefore, NF-κB and its interaction with host cells play an important role in the pathogenesis of tuberculosis.
Intra- and Interspecies Regulation of Gene Expression byActinobacillus actinomycetemcomitansLuxS
Authors: Fong Karen P. , Chung Whasun O. , Lamont Richard J. , Demuth Donald R. 
Published: July 2002

ABSTRACTThe cell density-dependent control of gene expression is employed by many bacteria for regulating a variety of physiological functions, including the generation of bioluminescence, sporulation, formation of biofilms, and the expression of virulence factors. Although periodontal organisms do not appear to secrete acyl-homoserine lactone signals, several species, e.g.,Porphyromonas gingivalis,Prevotella intermedia, andFusobacterium nucleatum, have recently been shown to secrete a signal related to the autoinducer II (AI-2) of the signal system 2 pathway inVibrio harveyi. Here, we report that the periodontal pathogenActinobacillus actinomycetemcomitansexpresses a homolog ofV. harveyi luxSand secretes an AI-2-like signal. Cell-free conditioned medium fromA. actinomycetemcomitansor from a recombinantEscherichia colistrain (E. coliAIS) expressingA. actinomycetemcomitans luxSinduced luminescence inV. harveyiBB170 >200-fold over controls. AI-2 levels peaked in mid-exponential-phase cultures ofA. actinomycetemcomitansand were significantly reduced in late-log- and stationary-phase cultures. Incubation of early-log-phaseA. actinomycetemcomitanscells with conditioned medium fromA. actinomycetemcomitansor fromE. coliAIS resulted in a threefold induction of leukotoxic activity and a concomitant increase in leukotoxin polypeptide. In contrast, no increase in leukotoxin expression occurred when cells were exposed to sterile medium or to conditioned broth fromE. coliAIS−, a recombinant strain in whichluxSwas insertionally inactivated.A. actinomycetemcomitansAI-2 also induced expression ofafuA, encoding a periplasmic iron transport protein, approximately eightfold, suggesting that LuxS-dependent signaling may play a role in the regulation of iron acquisition byA. actinomycetemcomitans. Finally,A. actinomycetemcomitansAI-2 added intranscomplemented aluxSknockout mutation inP. gingivalisby modulating the expression of theluxS-regulated genesuvrBandhasFin this organism. Together, these results suggest that LuxS-dependent signaling may modulate aspects of virulence and the uptake of iron byA. actinomycetemcomitansand induce responses in other periodontal organisms in mixed-species oral biofilm.
Immunological Studies of Chronic Ocular Toxoplasmosis: Up-Regulation of Major Histocompatibility Complex Class I and Transforming Growth Factor β and a Protective Role for Interleukin-6
Authors: Lyons R. E. , Anthony J. P. , Ferguson D. J. P. , Byrne N. , Alexander J. , Roberts F. , Roberts C. W. 
Published: July 2002

ABSTRACTA murine model was used to characterize the local immune and inflammatory response during ocular toxoplasmosis. Major histocompatibility complex (MHC) class I, normally expressed at low levels in immune-privileged sites such as the eye, was up-regulated during infection as determined by competitive reverse transcriptase (RT)-PCR and immunocytochemistry for both β2-microglobulin and the MHC class I heavy chain. However, the eyes of chronically infected mice also had increased levels of mRNA transcripts for transforming growth factor β, a cytokine associated with immune privilege and constitutively expressed in normal eyes. Transcripts for a number of inflammatory mediators, including interleukin-6 (IL-6), were increased during chronic infection. The role of IL-6 was further investigated by comparing disease progression and the development of the local immune response in wild-type (WT) and IL-6-deficient mice (IL-6−/−mice). Following infection, IL-6−/−mice developed more severe inflammation in the retina and vitreous humor compared with WT mice. This increased severity of disease was associated with reduced ocular IL-1α and increased tumor necrosis factor α mRNA production compared with WT mice. Moreover, the increased severity of disease in IL-6−/−mice correlated with increased eye parasite burden as determined by RT-PCR for theToxoplasma gondiibradyzoite-specificLDH2gene. These results demonstrate alterations to components of immune privilege as a result of ocular toxoplasmosis and a role for IL-6 in controlling parasite numbers and inflammation in the eye.
Passive Immunization with Melanin-Binding Monoclonal Antibodies Prolongs Survival of Mice with Lethal
Cryptococcus neoformans
Infection
Authors: Rosas Ángel L. , Nosanchuk Joshua D. , Casadevall Arturo 
Published: July 2002

ABSTRACT

Passive immunization with monoclonal antibodies (MAbs) to melanin prolonged the survival of and reduced the fungal burden in
Cryptococcus neoformans
-infected mice in comparison to controls. MAbs to melanin reduced the growth rate of in vitro-melanized
C. neoformans
cells, suggesting a new mechanism of antibody-mediated protection.
Molecular Basis for Variable Expression of Merozoite Surface Antigen gp45 among American Isolates ofBabesia bigemina
Authors: Fisher Tina G. , McElwain Terry F. , Palmer Guy H. 
Published: July 2002

ABSTRACTImmunization with the merozoite surface glycoprotein gp45 induces protection against challenge using the homologousBabesia bigeminastrain. However, gp45 B-cell epitopes are highly polymorphic amongB. bigeminastrains isolated from different geographical locations within North and South America. The molecular basis for this polymorphism was investigated using the JG-29 biological clone of a Mexico strain ofB. bigeminaand comparison with the Puerto Rico, St. Croix, and Texcoco strains. The molecular size and antibody reactivity of gp45 expressed by the JG-29 clone were identical to those of the parental Mexico strain.gp45cDNA and the genomic locus encompassinggp45were cloned and sequenced from JG-29. The locus sequence and Southern blot data were consistent with a singlegp45copy in the JG-29 genome. The JG-29 cDNA expressed the full-length protein recognized by the gp45-specific monoclonal antibody 14/1.3.2. The genomes of the Puerto Rico and St. Croix strains ofB. bigeminawere shown to lack a closely relatedgp45-like gene by PCR using multiple primer sets and by Southern blots using both full-length and region-specificgp45probes. This genomic difference was confirmed using unpassaged isolates from a 1999 disease outbreak in Puerto Rico. In contrast, the Texcoco strain retains agp45gene, encoding an open reading frame identical to that of JG-29. However, the Texcocogp45gene is not transcribed. These two mechanisms, lack of a closely relatedgp45-like gene and failure to transcribegp45, result in generation of antigenic polymorphism amongB. bigeminastrains, and the latter mechanism is unique compared to prior mechanisms of antigenic polymorphism identified in babesial parasites.
Induction of Autoimmune Valvular Heart Disease by Recombinant Streptococcal M Protein
Authors: Quinn Anthony , Kosanke Stanley , Fischetti Vincent A. , Factor Stephen M. , Cunningham Madeleine W. 
Published: July 2002

ABSTRACTRheumatic heart disease is an autoimmune sequela of group A streptococcal infection. Previous studies have established that streptococcal M protein is structurally and immunologically similar to cardiac myosin, a well-known mediator of inflammatory heart disease. In this study, we investigated the hypothesis that streptococcal M protein could produce inflammatory valvular heart lesions similar to those seen in rheumatic fever (RF). Fifty percent (3 of 6) of Lewis rats immunized with recombinant type 6 streptococcal M protein (rM6) developed valvulitis as well as focal lesions of myocarditis. Valvular lesions initiated at the valve surface endothelium spread into the valve. Anitschkow cells and verruca-like lesions were present. T cells from rM6-immunized rats proliferated in the presence of purified cardiac myosin, but not skeletal myosin. A T-cell line produced from rM6-treated rats proliferated in the presence of cardiac myosin and rM6 protein. The study demonstrates that the Lewis rat is a model of valvular heart disease and that streptococcal M protein can induce an autoimmune cell-mediated immune attack on the heart valve in an animal model. The data support the hypothesis that a bacterial antigen can break immune tolerance in vivo, an important concept in autoimmunity.
Arginine-Specific Protease fromPorphyromonas gingivalisActivates Protease-Activated Receptors on Human Oral Epithelial Cells and Induces Interleukin-6 Secretion
Authors: Lourbakos Afrodite , Potempa Jan , Travis James , D'Andrea Michael R. , Andrade-Gordon Patricia , Santulli Rosemary , Mackie Eleanor J. , Pike Robert N. 
Published: July 2002

ABSTRACTPeriodontitis is a chronic inflammatory disease affecting oral tissues. Oral epithelial cells represent the primary barrier against bacteria causing the disease. We examined the responses of such cells to an arginine-specific cysteine proteinase (RgpB) produced by a causative agent of periodontal disease,Porphyromonas gingivalis. This protease caused an intracellular calcium transient in an oral epithelial cell line (KB), which was dependent on its enzymatic activity. Since protease-activated receptors (PARs) might mediate such signaling, reverse transcription-PCR was used to characterize the range of these receptors expressed in the KB cells. The cells were found to express PAR-1, PAR-2, and PAR-3, but not PAR-4. In immunohistochemical studies, human gingival epithelial cells were found to express PAR-1, PAR-2, and PAR-3 on their surface, but not PAR-4, indicating that the cell line was an effective model for the in vivo situation. PAR-1 and PAR-2 expression was confirmed in intracellular calcium mobilization assays by treatment of the cells with the relevant receptor agonist peptides. Desensitization experiments strongly indicated that signaling of the effects of RgpB was occurring through PAR-1 and PAR-2. Studies with cells individually transfected with each of these two receptors confirmed that they were both activated by RgpB. Finally, it was shown that, in the oral epithelial cell line, PAR activation by the bacterial protease-stimulated secretion of interleukin-6. This induction of a powerful proinflammatory cytokine suggests a mechanism whereby cysteine proteases fromP. gingivalismight mediate inflammatory events associated with periodontal disease on first contact with a primary barrier of cells.
CpG Oligodeoxynucleotides Enhance Host Defense during Murine Tuberculosis
Authors: Juffermans Nicole P. , Leemans Jaklien C. , Florquin Sandrine , Verbon Annelies , Kolk Arend H. , Speelman Peter , van Deventer Sander J. H. , van der Poll Tom 
Published: July 2002

ABSTRACTOligodeoxynucleotides (ODNs) containing unmethylated CpG motifs activate immune cells to produce cytokines. CpG ODNs protect mice against infections with intracellular bacteria by the induction of a T helper 1 (Th1) response. To determine the effect of CpG ODNs in pulmonary tuberculosis, mice were treated with CpG ODNs or control ODNs at the time of intranasal infection. CpG ODNs reduced mycobacterial outgrowth for up to 5 weeks afterMycobacterium tuberculosisinfection and were associated with a decrease in inflammation in lung tissue. CpG treatment was also associated with elevated levels of gamma interferon (IFN-γ) and decreased levels of interleukin 4 in the lungs and an increased capacity of splenocytes to secrete Th1-type cytokines. CpG ODNs given 2 weeks after infection were still able to reduce mycobacterial outgrowth and to enhance a Th1 response 5 weeks postinfection. Administration of CpG ODNs to IFN-γ-gene-deficient mice failed to reduce mycobacterial outgrowth. These data suggest that CpG ODNs improve host defense during pulmonary tuberculosis by an IFN-γ-dependent mechanism.
Role of CsrR, Hyaluronic Acid, and SpeB in the Internalization ofStreptococcus pyogenesM Type 3 Strain by Epithelial Cells
Authors: Jadoun Jeries , Eyal Osnat , Sela Shlomo 
Published: July 2002

ABSTRACTInternalization of group A streptococcus by human epithelial cells has been extensively studied during the past 6 years. It is now clear that multiple mechanisms are involved in this process. We have previously demonstrated that the CsrR global regulator controls the internalization of an invasive M type 3 strain through regulation of thehas(hyaluronic acid synthesis) operon, as well as another, unknown gene(s). Recently, it was reported that the CsrR-regulated cysteine protease (SpeB) is also involved in bacterial uptake. In this study we have examined the roles of CsrR, hyaluronic acid capsule, and SpeB in streptococcal internalization. We have constructed isogenic mutants of the M3 serotype deficient in thecsrR,hasA, andspeBgenes and tested their ability to be internalized by HEp-2 epithelial cells. Inactivation ofcsrRabolished internalization, while inactivation of eitherhasAorspeBincreased the internalization efficiency. Mutation incsrRderepressedhasAtranscription and lowered the activity of SpeB, while no effect onspeBtranscription was observed. ThespeBmutant expressed smaller amounts of capsule, while thehasAmutant transcribed morecsrRandspeBmRNAs. Thus, it seems that complex interactions between CsrR, SpeB, and capsule are involved in modulation of group A streptococcus internalization.
Identification of Major Outer Surface Proteins of
Streptococcus agalactiae
Authors: Hughes Martin J. G. , Moore Joanne C. , Lane Jonathan D. , Wilson Rebecca , Pribul Philippa K. , Younes Zabin N. , Dobson Richard J. , Everest Paul , Reason Andrew J. , Redfern Joanne M. , Greer Fiona M. , Paxton Thanai , Panico Maria , Morris Howard R. , Feldman Robert G. , Santangelo Joseph D. 
Published: July 2002

ABSTRACT

To identify the major outer surface proteins of
Streptococcus agalactiae
(group B streptococcus), a proteomic analysis was undertaken. An extract of the outer surface proteins was separated by two-dimensional electrophoresis. The visualized spots were identified through a combination of peptide sequencing and reverse genetic methodologies. Of the 30 major spots identified as
S. agalactiae
specific, 27 have been identified. Six of these proteins, previously unidentified in
S. agalactiae
, were sequenced and cloned. These were ornithine carbamoyltransferase, phosphoglycerate kinase, nonphosphorylating glyceraldehyde-3-phosphate dehydrogenase, purine nucleoside phosphorylase, enolase, and glucose-6-phosphate isomerase. Using a gram-positive expression system, we have overexpressed two of these proteins in an in vitro system. These recombinant, purified proteins were used to raise antisera. The identification of these proteins as residing on the outer surface was confirmed by the ability of the antisera to react against whole, live bacteria. Further, in a neonatal-animal model system, we demonstrate that some of these sera are protective against lethal doses of bacteria. These studies demonstrate the successful application of proteomics as a technique for identifying vaccine candidates.