bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cellular Internalization of Cytolethal Distending Toxin fromHaemophilus ducreyi
Authors: Cortes-Bratti Ximena , Chaves-Olarte Esteban , Lagergård Teresa , Thelestam Monica 
Published: July 2002

ABSTRACTThe chancroid bacteriumHaemophilus ducreyiproduces a toxin (HdCDT) which is a member of the recently discovered family of cytolethal distending toxins (CDTs). These protein toxins prevent the cyclin-dependent kinase cdc2 from being activated, thus blocking the transition of cells from the G2phase into mitosis, with the consequent arrest of intoxicated cells in G2. It is not known whether these toxins act by signaling from the cell surface or intracellularly only. Here we report that HdCDT has to undergo at least internalization before being able to act. Cellular intoxication was inhibited (i) by removal of clathrin coats via K+depletion, (ii) by treatment with drugs that inhibit receptor clustering into coated pits, and (iii) in cells genetically manipulated to fail in clathrin-dependent endocytosis. Intoxication was also completely inhibited in cells treated with bafilomycin A1 or nocodazole and in cells incubated at 18°C, i.e., under conditions known to block the fusion of early endosomes with downstream compartments. Moreover, disruption of the Golgi complex by treatment with brefeldin A or ilimaquinone blocked intoxication. In conclusion, our data indicate that HdCDT enters cells via clathrin-coated pits and has to be transported via the Golgi complex in order to intoxicate cells. This is the first member of the family of CDTs for which cellular internalization and some details of the pathway have been demonstrated.
Early Induction of Interleukin-12 by Human Monocytes Exposed toCryptococcus neoformansMannoproteins
Authors: Pitzurra Lucia , Cherniak Robert , Giammarioli Monica , Perito Stefano , Bistoni Francesco , Vecchiarelli Anna 
Published: July 2002

ABSTRACTInterleukin-12 (IL-12) production by human monocytes stimulated with mannoproteins (MPs) ofCryptococcus neoformanswas investigated. The results reported show that secreted or cell-associated MPs induce an early and significant production of IL-12. MPs show different capabilities to quantitatively affect IL-12 production; MP2, an 8.2-kDa MP purified from the culture supernatant ofC. neoformans, appears to be the most potent stimulator. Cytochalasin B inhibits both internalization and IL-12 induction by MP. In addition, a drastic reduction of IL-12 was observed when monocytes were cultured in the absence of normal human serum or treated with soluble mannan. Early production of IL-12 promotes early secretion of gamma interferon by T cells but does not influence the magnitude of the MP-induced lymphoproliferative response. Overall our results identify cryptococcal antigens responsible for rapid and potent induction of IL-12 in monocytes. MPs appear to regulate IL-12 secretion by internalization via the endocytic pathway and by interaction with monocyte receptors or serum factors.
Isolation, Affinity Purification, and Identification of Piglet Small Intestine Mucosa Receptor for Enterotoxigenic
Escherichia coli
K88ac+ Fimbriae
Authors: Fang Lin , Gan Zhibo , Marquardt Ronald R. 
Published: July 2002

ABSTRACT

An affinity chromatography technique was utilized to isolate and purify the receptors of
Escherichia coli
K88ac
+
fimbriae from the mucus of the small intestines of newborn piglets. Purified K88ac+ fimbriae were covalently immobilized onto a beaded agarose matrix (Sepharose 4B). The immobilized fimbriae were used for the affinity purification of the K88ac+ receptors. Only two major proteins were tightly and specifically bound to the immobilized fimbriae after the column containing bound receptor was washed exhaustively with a buffer containing a high concentration of salt and a detergent. The receptors were eluted as a single component at a low pH. The isolated proteins were then subjected to enzyme-linked immunosorbent assay, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and Western blot (immunoblot) analyses. The two proteins were of high purity, were responsible for nearly all of the fimbrial binding capacity of the crude mucus, and had molecular masses of 26 and 41 kDa. The method for isolation of
E. coli
binding proteins is simple and yields purified intestinal receptors in a single chromatographic run. The intestinal mucus of different piglets has different proportions of the two receptor proteins.
Cytokine Expression and Production by PurifiedHelicobacter pyloriUrease in Human Gastric Epithelial Cells
Authors: Tanahashi Toshihito , Kita Masakazu , Kodama Tadashi , Yamaoka Yoshio , Sawai Naoki , Ohno Tomoyuki , Mitsufuji Shoji , Wei Ya-Ping , Kashima Kei , Imanishi Jiro 
Published: July 2002

ABSTRACTCytokines have been proposed to play an important role inHelicobacter pylori-associated gastroduodenal diseases, but the exact mechanism of the cytokine induction remains unclear.H. pyloriurease, a major component of the soluble proteins extracted from bacterial cells, is considered to be one of the virulence factors for the inflammation in the gastric mucosa that is produced inH. pyloriinfection. However, the response of human gastric epithelial cells to the stimulation of urease has not been investigated. In the present study, we used human gastric epithelial cells in a primary culture system and examined whetherH. pyloriurease stimulates the gastric epithelial cells to induce proinflammatory cytokines by reverse transcription-PCR and enzyme-linked immunosorbent assay. First, by using peripheral blood mononuclear cells (PBMC) and a gastric cancer cell line (MKN-45 cells), we confirmed the ability of purifiedH. pyloriurease to induce the production of proinflammatory cytokines. Furthermore, we demonstrated that the human gastric epithelial cells produced interleukin-6 (IL-6) and tumor necrosis factor alpha, but not IL-8, following stimulation with purified urease. The patterns of cytokine induction differed among human PBMC, MKN-45 cells, and human gastric epithelial cells. These results suggest that the human gastric epithelial cells contribute to the induction of proinflammatory cytokines by the stimulation ofH. pyloriurease, indicating that the epithelial cells were involved in the mucosal inflammation that accompaniedH. pyloriinfection.
Streptococcus sobrinus
Antigens That React to Salivary Antibodies Induced by Tonsillar Application of Formalin-Killed
S. sobrinus
in Rabbits
Authors: Fukuizumi Takaki , Inoue Hiromasa , Tsujisawa Toshiyuki , Uchiyama Choji 
Published: July 2002

ABSTRACT

We previously found that tonsillar application of antigen induces a strong antibody response to
Streptococcus sobrinus
in saliva and blood plasma. Rabbits immunized against
S. sobrinus
by tonsillar application were highly resistant to experimental dental caries triggered by oral inoculation of living
S. sobrinus
organisms with sucrose. In the present study, we examined the reaction of
S. sobrinus
antigens to the antibodies induced by the tonsillar application of
S. sobrinus
AHT-k in rabbits and compared them to those antibodies induced by intramuscular injection. In an enzyme-linked immunosorbent assay using ultrasonic fragments from mutans group streptococci, the saliva and blood plasma selectively reacted to
S. sobrinus
AHT-k (serotype g) and serologically related streptococci (serotypes a, d, and h) in the sixth week after tonsillar application, whereas the blood plasma in the sixth week after intramuscular injection reacted to the unrelated streptococci (serotypes b, c, e, and f) in addition to the aforementioned streptococci. The antibody reactivity induced after tonsillar application was not lost after treatment of the antigen with heat or proteinase digestion, whereas these treatments resulted in a 70% decrease of the antibody reactivity induced by intramuscular injection. The inhibition by haptenic sugars and the decrease in immunoreactivity by heat treatment and proteinase digestion suggested that 80% of the antibodies induced by tonsillar application reacted to saccharides. These saccharide antigens appeared to be involved in a specific reaction with
S. sobrinus
-specific streptococci and a selective reaction with serologically related streptococci. These antigens are probably involved in anticaries reactions in experimental dental caries.
Absence of SpeB Production in Virulent Large Capsular Forms of Group A Streptococcal Strain 64
Authors: Raeder Roberta , Harokopakis Evlambia , Hollingshead Susan , Boyle Michael D. P. 
Published: July 2002

ABSTRACT
Passage in human blood of group A streptococcal isolate 64p was previously shown to result in the enhanced expression of M and M-related proteins. Similarly, when this isolate was injected into mice via an air sac model for skin infection, organisms recovered from the spleens showed both increased expression of M and M-related proteins and increased skin-invasive potential. We show that these phenotypic changes were not solely the result of increased transcription of the mRNAs encoding the M and M-related gene products. Rather, the altered expression was associated with posttranslational modifications of the M and M-related proteins that occur in this strain, based on the presence or absence of another virulence protein, the streptococcal cysteine protease SpeB. The phenotypic variability also correlates with colony size variation. Large colonies selected by both regimens expressed more hyaluronic acid, which may explain differences in colony morphology. All large-colony variants were SpeB negative and expressed three distinct immunoglobulin G (IgG)-binding proteins in the M and M-related protein family. Small-colony variants were SpeB positive and bound little IgG through their M and M-related proteins because these proteins, although made, were degraded or altered in profile by the SpeB protease. We conclude that passage in either human blood or a mouse selects for a stable, phase-varied strain of group A streptococci which is altered in many virulence properties.
Use of Defined Mutants To Assess the Role of theCampylobacter rectusS-Layer in Bacterium-Epithelial Cell Interactions
Authors: Wang Beinan , Kraig Ellen , Kolodrubetz David 
Published: July 2002

ABSTRACTCampylobacter rectusis a periodontal pathogen with a 150-kDa protein on its cell surface. This protein forms a paracrystalline lattice, called the S-layer, surrounding the outer membrane of this gram-negative bacterium. To initiate a genetic analysis of the possible role of the S-layer in the initial interaction ofC. rectuswith host epithelial cells,C. rectusstrains lacking the S-layer protein gene (crsA) were constructed by allelic exchange mutagenesis. Surprisingly, the lack of the S-layer had only a minor effect on the interaction ofC. rectuswith HEp-2 epithelial cells; CrsA+cells were 30 to 50% more adherent than were CrsA−bacteria. Since the host cell expression of cytokines appears to play an important role in the pathogenesis of periodontal diseases, the effect of the S-layer on the epithelial cell cytokine response was also examined by quantitative reverse transcriptase PCR and enzyme-linked immunosorbent assay. Although there were no changes in the mRNA levels for the anti-inflammatory cytokines interleukin-1 receptor agonist (IL-1ra), IL-13, and transforming growth factor β, the expression and secretion of the proinflammatory cytokines IL-6, IL-8, and tumor necrosis factor alpha (TNF-α) were significantly induced by both wild-typeC. rectusand CrsA−bacteria. Interestingly, the kinetics of cytokine induction differed for the CrsA+and CrsA−bacteria. At early time points, the HEp-2 cells challenged with CrsA−bacteria produced higher levels of IL-6, IL-8, and TNF-α mRNA and protein than did cells challenged with CrsA+bacteria. We conclude thatC. rectusmay help initiate periodontitis by increasing the expression of proinflammatory cytokines and that the S-layer may temper this response to facilitate the survival ofC. rectusat the site of infection.
Immune Responses to Specific Antigens of
Streptococcus pneumoniae
and
Moraxella catarrhalis
in the Respiratory Tract
Authors: Samukawa Takao , Yamanaka Noboru , Hollingshead Susan , Klingman Karin , Faden Howard 
Published: July 2002

ABSTRACT

Streptococcus pneumoniae
and
Moraxella catarrhalis
are two common respiratory pathogens, colonizing as many as 54 and 72% of children, respectively, by 1 year of age. The immune responses to surface protein A of
S. pneumoniae
(PspA) and the high-molecular-weight outer membrane protein of
M. catarrhalis
(UspA) in the sera of various age groups in the general population and in the nasopharynges of 30 children monitored from birth through 1 year of age were evaluated. Immunoglobulin G (IgG) was the dominant serum antibody to PspA and UspA. Whereas the serum antibody response to PspA peaked in childhood, the antibody response to UspA peaked in adulthood. In the first 2 years of life, comparable amounts of IgM and IgG antibodies to both proteins were observed. In older persons, IgG antibodies to both antigens predominated over IgM antibodies. The levels of IgA antibody to these antigens in serum remained low during the first 2 years of life. The levels of IgM antibody to the two antigens in serum exceeded the levels of IgA antibody to the same two antigens throughout life. Although IgA was the dominant antibody to PspA and UspA in airway secretions, it was detected in a minority of the children (3 of 15 for PspA and 0 of 15 for UspA). Even the majority of the children previously colonized with these pathogens lacked antibody to them in their secretions.
Expression of Polymorphic
msp1
β Genes during Acute
Anaplasma marginale
Rickettsemia
Authors: Camacho-Nuez Minerva , de Lourdes Muñoz Maria , Suarez Carlos E. , McGuire Travis C. , Brown Wendy C. , Palmer Guy H. 
Published: July 2002

ABSTRACT

Immunization of cattle with native MSP1 induces protection against
Anaplasma marginale
. The native immunogen is composed of a single MSP1a protein and multiple, undefined MSP1b polypeptides. In addition to the originally sequenced gene, designated
msp1β(F1)
, we identified three complete
msp1
β genes in the Florida strain:
msp1β(F2)
,
msp1β(F3)
, and
msp1β(F4)
. Each of these polymorphic genes encodes a structurally unique MSP1b protein, and unique transcripts can be identified during acute
A. marginale
rickettsemia. The structural polymorphism is clustered in discrete variable regions, and each MSP1b protein results from a unique mosaic of five variable regions. Although each of the MSP1b proteins in the Florida strain contains epitopes recognized by serum antibody induced by protective immunization with the native MSP1 complex, the variable regions also include epitopes expressed by some but not all of the MSP1b proteins. These data support testing recombinant vaccines composed of the multiple antigenically and structurally unique MSP1b proteins combined with MSP1a in order to mimic the efficacy of native MSP1 immunization.
Molecular Epidemiologic Approaches to Urinary Tract Infection Gene Discovery in Uropathogenic
Escherichia coli
Authors: Zhang Lixin , Foxman Betsy , Manning Shannon D. , Tallman Patricia , Marrs Carl F. 
Published: July 2002

ABSTRACT

Urinary tract infection (UTI) is one of the most frequently acquired bacterial infections. The vast majority of UTIs are caused by a large, genetically heterogeneous group of
Escherichia coli
. This genetic diversity has hampered identification of UTI-related genes. A three-step experimental strategy was used to identify genes potentially involved in
E. coli
UTI transmission or virulence: epidemiologic pairing of a UTI-specific strain with a fecal control, differential cloning to isolated UTI strain-specific DNA, and epidemiologic screening to identify sequences among isolated DNAs that are associated with UTI. The 37 DNA sequences initially isolated were physically located all over the tester strain genome. Only two hybridized to the total DNA of the sequenced
E. coli
K-12 strain; eight sequences were present significantly more frequently in UTI isolates than in fecal isolates. Three of the eight sequences matched to genes for multidrug efflux proteins, usher proteins, and pathogenicity island insertion sites, respectively. Using population characteristics to direct gene discovery and evaluation is a productive strategy applicable to any system.
Staphylococcus aureusProtein A Recognizes Platelet gC1qR/p33: a Novel Mechanism for Staphylococcal Interactions with Platelets
Authors: Nguyen Truc , Ghebrehiwet Berhane , Peerschke Ellinor I. B. 
Published: July 2002

ABSTRACTThe adhesion ofStaphylococcus aureusto platelets is a major determinant of virulence in the pathogenesis of endocarditis. Molecular mechanisms mediatingS. aureusinteractions with platelets, however, are incompletely understood. The present study describes the interaction betweenS. aureusprotein A and gC1qR/p33, a multifunctional, ubiquitously distributed cellular protein, initially described as a binding site for the globular heads of C1q. Suspensions of fixedS. aureusor purified protein A, chemically cross-linked to agarose support beads, were found to capture native gC1qR from whole platelets. Moreover, biotinylated protein A bound specifically to fixed, adherent, human platelets. This interaction was inhibited by unlabeled protein A, soluble recombinant gC1qR (rgC1qR), or anti-gC1qR antibody F(ab′)2fragments. The interaction between protein A and platelet gC1qR was underscored by studies illustrating preferential recognition of the protein A-bearingS. aureusCowan I strain by gC1qR compared to recognition of the protein A-deficient Wood 46 strain, as well as inhibition ofS. aureusCowan I strain adhesion to immobilized platelets by soluble protein A. Further characterization of the protein A-gC1qR interaction by solid-phase enzyme-linked immunosorbent assay techniques measuring biotinylated gC1qR binding to immobilized protein A revealed specific binding that was inhibited by soluble protein A with a 50% inhibitory concentration of (3.3 ± 0.7) × 10−7M (mean ± standard deviation;n= 3). Rabbit immunoglobulin G (IgG) also prevented gC1qR-protein A interactions, and inactivation of protein A tyrosil residues by hyperiodination, previously reported to prevent the binding of IgG Fc, but not Fab, domains to protein A, abrogated gC1qR binding. These results suggest similar protein A structural requirements for gC1qR and IgG Fc binding. Further studies of structure and function using a truncated gC1qR mutant lacking amino acids 74 to 95 demonstrated that the protein A binding domain lies outside of the gC1qR amino-terminal alpha helix, which contains binding sites for the globular heads of C1q. In conclusion, the data implicate the platelet gC1qR as a novel cellular binding site for staphylococcal protein A and suggest an additional mechanism for bacterial cell adhesion to sites of vascular injury and thrombosis.
A Large Toxin from Pathogenic
Escherichia coli
Strains That Inhibits Lymphocyte Activation
Authors: Klapproth Jan-Michael A. , Scaletsky Isabel C. A. , McNamara Barry P. , Lai Li-Ching , Malstrom Carol , James Stephen P. , Donnenberg Michael S. 
Published: July 2002

ABSTRACT

The mechanisms by which bacteria resist cell-mediated immune responses to cause chronic infections are largely unknown. We report the identification of a large gene present in enteropathogenic strains of
Escherichia coli
(EPEC) that encodes a toxin that specifically inhibits lymphocyte proliferation and interleukin-2 (IL-2), IL-4, and gamma interferon production in response to a variety of stimuli. Lymphostatin, the product of this gene, is predicted to be 366 kDa and shares significant homology with the catalytic domains of the large clostridial cytotoxins. A mutant EPEC strain that has a disruption in this gene lacks the ability to inhibit lymphokine production and lymphocyte proliferation. Enterohemorrhagic
E. coli
strains of serotype O157:H7 possess a similar gene located on a large plasmid. Loss of the plasmid is associated with loss of the ability to inhibit IL-2 expression while transfer of the plasmid to a nonpathogenic strain of
E. coli
is associated with gain of this activity. Among 89 strains of
E. coli
and related bacteria tested,
lifA
sequences were detected exclusively in strains capable of attaching and effacing activity. Lymphostatin represents a new class of large bacterial toxins that blocks lymphocyte activation.
Intracellular Trafficking and Killing ofStreptococcus pneumoniaeby Human Alveolar Macrophages Are Influenced by Opsonins
Authors: Gordon Stephen B. , Irving Glen R. B. , Lawson Roderick A. , Lee Margaret E. , Read Robert C. 
Published: July 2002

ABSTRACTHuman alveolar macrophages (HAM) are the major resident phagocytic cells of the gas-exchanging areas of the lung. Following contact with macrophages, bacteria enter phagosomes, which gradually acquire the characteristics of terminal phagolysosomes, with incorporation of lysosome-associated membrane protein (LAMP). We measured the binding of type 1Streptococcus pneumoniaeto the surface of HAM and then measured subsequent internalization and phagosomal incorporation of LAMP-1 under various opsonic conditions. Opsonization with serum containing immunoglobulin resulted in significantly greater binding of pneumococci to HAM compared with opsonization with immunoglobulin G (IgG)-depleted serum containing complement, which in turn resulted in marginally increased binding over that observed in the absence of opsonization. Internalization of opsonizedS. pneumoniaegradually increased to a maximum of 20% of bound bacteria by 120 min of warm incubation, with 20% of internalized pneumococci being localized within LAMP-containing compartments by 80 min. Internalization of opsonizedS. pneumoniaeby HAM correlated with a reduction of bacterial viability. When inocula were adjusted so that pneumococcal binding under different conditions was equalized, subsequent internalization, trafficking to LAMP-containing compartments, and reduction of bacterial viability were less efficient in the absence of opsonization than that observed following opsonization with adsorbed or IgG-replete adsorbed serum. Once bound to the surface of HAM, pneumococci opsonized with adsorbed serum with or without IgG were internalized, processed, and killed equally well. In conclusion, binding, intracellular trafficking, and killing ofS. pneumoniaeby HAM are each significantly increased by opsonization with serum containing immunogloblin and/or complement.
Bactericidal/Permeability-Increasing Protein Prevents Mucosal Damage in an Experimental Rat Model of Chronic Otitis Media with Effusion
Authors: Nell Marja J. , Koerten Henk K. , Grote Jan J. 
Published: July 2002

ABSTRACT
In this study, the efficacy of bactericidal/permeability-increasing protein (BPI) was assessed in a rat model of chronic otitis media with effusion. BPI injection prevented disturbance of the mucociliary clearance system of the middle ear. Hence, it is postulated that BPI can be a new therapy for chronic otitis media with effusion.
Apoptosis Induced byStaphylococcus aureusin Epithelial Cells Utilizes a Mechanism Involving Caspases 8 and 3
Authors: Wesson Carla A. , Deringer James , Liou Linda E. , Bayles Kenneth W. , Bohach Gregory A. , Trumble William R. 
Published: July 2002

ABSTRACTIn this study, we demonstrate that the mechanism by whichStaphylococcus aureusinduces apoptosis in bovine mammary epithelial (MAC-T) cells involves caspases 8 and 3, two key components of a proteolytic cascade leading to apoptosis. In addition, internalizedS. aureusinduces expression of the inflammatory cytokines tumor necrosis factor alpha and interleukin-1β by MAC-T cells. These data suggest that the internalization ofS. aureuscould induce specific cellular responses in vivo that may ultimately impact the course of infection.