bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contribution of NK, NK T, γδ T, and αβ T Cells to the Gamma Interferon Response Required for Liver Protection againstTrypanosoma cruzi
Authors: Sardinha Luiz Roberto , Elias Rosa Maria , Mosca Tainá , Bastos Karina R. B. , Marinho Cláudio R. F. , D'Império Lima Maria Regina , Álvarez José M. 
Published: March 2006

ABSTRACTIn the present work, we show that intracellularTrypanosoma cruziis rarely found in the livers of acutely infected mice, but inflammation is commonly observed. The presence of numerous intrahepatic amastigotes in infected gamma interferon (IFN-γ)-deficient mice corroborates the notion that the liver is protected by an efficient local immunity. The contribution of different cell populations was suggested by data showing that CD4- and CD8-deficient mice were able to restrain liver parasite growth. Therefore, we have characterized the liver-infiltrating lymphocytes and determined the sources of IFN-γ during acuteT. cruziinfection. We observed that natural killer (NK) cells increased by day 7, while T and B cells increased by day 14. Among CD3+cells, CD4+, CD8+, and CD4−CD8−cell populations were greatly expanded. A large fraction of CD3+cells were positive for PanNK, a β1 integrin expressed by NK and NK T cells. However, these lymphocytes were not classic NK T cells because they did not express NK1.1 and showed no preferential usage of Vβ8. Otherwise, liver NK T (CD3+NK1.1+) cells were not increased in acutely infected mice. The majority of PanNK+CD4+and PanNK+CD8+cells expressed T-cell receptor αβ (TCRαβ), whereas PanNK+CD4−CD8−cells were positive for TCRγδ. In fact, γδ T cells showed the most remarkable increase (40- to 100-fold) among liver lymphocytes. Most importantly, intracellular analysis revealed high levels of IFN-γ production at day 7 by NK cells and at day 14 by CD4+, CD8+, and CD4−CD8−TCRγδ+cells. We concluded that NK cells are a precocious source of IFN-γ in the livers of acutely infected mice, and, as the disease progresses, conventional CD4+and CD8+T cells and γδ T cells, but not classic NK-T cells, may provide the IFN-γ required for liver protection againstT. cruzi.
Exposure of Lymphocytes to High Doses of
Actinobacillus actinomycetemcomitans
Cytolethal Distending Toxin Induces Rapid Onset of Apoptosis-Mediated DNA Fragmentation
Authors: Shenker Bruce J. , Demuth Donald R. , Zekavat Ali 
Published: March 2006

ABSTRACT

We have shown previously that treatment of human lymphocytes with the
Actinobacillus actinomycetemcomitans
cytolethal distending toxin (Cdt) results in dose-dependent G
2
arrest, followed 24 h later by apoptotic cell death. Here we demonstrated that for Jurkat cells exposed to high concentrations of Cdt (>0.2 ng/ml) there was a dose-dependent increase in the level of S-phase cells and a concomitant decrease in the level of G
2
cells. Fluorescence-activated cell sorter analysis demonstrated that the S-phase cells did not incorporate BrdU and likely represented cells that arrested in G
2
and underwent significant DNA fragmentation. Analysis of the kinetics of the appearance of both S-phase cells and apoptotic cells supported this interpretation. Cells exposed to low doses of toxin exhibited G
2
arrest at 24 h, but at 48 and 72 h there were also decreases in the level of G
2
cells and concomitant increases in the levels of S, G
0
/G
1
, and sub-G
0
cells; these changes were paralleled by increased numbers of apoptotic cells. Cells exposed to high doses of toxin exhibited these changes 24 to 48 h earlier. We also examined the relationship between G
2
arrest, DNA fragmentation, and activation of the apoptotic cascade. We employed two inhibitors of apoptosis, overexpression of Bcl-2 and the caspase-3 inhibitor zvad. Both inhibitors blocked Cdt-induced apoptosis, Cdt-induced DNA fragmentation, and phosphorylation of the histone H2AX. However, the cells retained the ability to undergo G
2
arrest in the presence of the toxin. Thus, it appears that high doses of Cdt induce rapid onset of DNA degradation resulting from activation of the apoptotic cascade.
Mapping of a Domain Required for Protein-Protein Interactions and Inhibitory Activity of a
Helicobacter pylori
Dominant-Negative VacA Mutant Protein
Authors: Torres Victor J. , McClain Mark S. , Cover Timothy L. 
Published: March 2006

ABSTRACT

The
Helicobacter pylori
VacA toxin is an 88-kDa secreted protein that causes multiple alterations in mammalian cells and is considered an important virulence factor in the pathogenesis of peptic ulcer disease and gastric cancer. We have shown previously that a VacA mutant protein lacking amino acids 6 to 27 (Δ6-27p88 VacA) is able to inhibit many activities of wild-type VacA in a dominant-negative manner. Analysis of a panel of C-terminally truncated Δ6-27p88 VacA proteins indicated that a fragment containing amino acids 1 to 478 (Δ6-27p48) exhibited a dominant-negative phenotype similar to that of the full-length Δ6-27p88 VacA protein. In contrast, a shorter VacA fragment lacking amino acids 6 to 27 (Δ6-27p33) did not exhibit detectable inhibitory activity. The Δ6-27p48 protein physically interacted with wild-type p88 VacA, whereas the Δ6-27p33 protein did not. Mutational analysis indicated that amino acids 351 to 360 are required for VacA protein-protein interactions and for dominant-negative inhibitory activity. The C-terminal portion (p55 domain) of wild-type p88 VacA could complement either Δ6-27p33 or Δ(6-27/351-360)p48, reconstituting dominant-negative inhibitory activity. Collectively, our data provide strong evidence that the inhibitory properties of dominant-negative VacA mutant proteins are dependent on interactions between the mutant VacA proteins and wild-type VacA, and they allow mapping of a domain involved in the formation of oligomeric VacA complexes.
An IncI1 Plasmid Contributes to the Adherence of the Atypical EnteroaggregativeEscherichia coliStrain C1096 to Cultured Cells and Abiotic Surfaces
Authors: Dudley Edward G. , Abe Cecilia , Ghigo Jean-Marc , Latour-Lambert Patricia , Hormazabal Juan Carlos , Nataro James P. 
Published: March 2006

ABSTRACTEnteroaggregativeEscherichia coli(EAEC) is defined by a characteristic “stacked-brick” aggregative adherence (AA) pattern to cultured cells. In well-studied EAEC prototype strains (called typical EAEC strains), the AA phenotype requires aggregative adherence fimbriae (AAFs). However, previous studies suggest that known AAF alleles are not found in all EAEC strains. To define mechanisms contributing to adherence in an atypical strain, we studied EAEC strain C1096. AnE. coliK12 derivative carrying two plasmids, designated pSERB1 and pSERB2, from C1096 adhered to cell lines and exhibited an AA pattern. Nucleotide sequence analysis of pSERB1 indicated that it is related to plasmids of the IncI1 incompatibility group. These plasmids encode genes involved in pilus-mediated conjugal transfer, as well aspilL-V, which encodes a second pilus of the type IV family. Insertional inactivation of the gene predicted to encode the major type IV pilin subunit (pilS) reduced conjugal transfer of the plasmid by 4 orders of magnitude. Adherence of the mutant strain to polystyrene and to HT29 cells was reduced by approximately 21% and 75%, respectively. In a continuous-flow microfermentor, thepilSinactivation reduced mature biofilm formation on a glass slide by approximately 50%. In addition, the simultaneous presence of both pSERB1 and pSERB2 plasmids promotedpilS-independent biofilm formation. We conclude that the IncI1 plasmid of EAEC C1096 encodes a type IV pilus that contributes to plasmid conjugation, epithelial cell adherence, and adherence to abiotic surfaces. We also observe that AA can be mediated by factors distinct from AAF adhesins.
MyD88 Deficiency Enhances Acquisition and Transmission of
Borrelia burgdorferi
by
Ixodes scapularis
Ticks
Authors: Bockenstedt Linda K. , Liu Nengyin , Schwartz Ira , Fish Durland 
Published: March 2006

ABSTRACT

Borrelia burgdorferi
strains exhibit various degrees of infectivity and pathogenicity in mammals, which may be due to their relative ability to evade initial host immunity. Innate immune cells recognize
B. burgdorferi
by Toll-like receptors (TLRs) that use the intracellular molecule MyD88 to mediate effector functions. To determine whether impaired TLR signaling enhances
Ixodes scapularis
acquisition of
B. burgdorferi
, we fed nymphs on wild-type (WT) and MyD88
−/−
mice previously infected with two clinical isolates of
B. burgdorferi
, BL206, a high-virulence strain, and B348, an attenuated strain. Seventy-three percent of the nymphs that fed on BL206-infected WT mice and 40% of the nymphs that fed on B348-infected WT mice acquired
B. burgdorferi
, whereas 100% of the nymphs that fed on MyD88
−/−
mice became infected, irrespective of
B. burgdorferi
strain. Ticks that acquired infection after feeding on MyD88
−/−
mice harbored more spirochetes than those that fed on WT mice, as assessed by quantitative PCR for
B. burgdorferi
DNA. Vector transmission of BL206 and B348 was also enhanced when MyD88
−/−
mice were the blood meal hosts, with the mean pathogen burden at the skin inoculation site significantly higher than levels in WT mice. These results show that the absence of MyD88 facilitates passage of both low- and high-infectivity
B. burgdorferi
strains between the tick vector and the mammal and enhances the infectivity of a low-infectivity
B. burgdorferi
strain.
Correlation between Eosinophils and Protection against Reinfection withSchistosoma mansoniand the Effect of Human Immunodeficiency Virus Type 1 Coinfection in Humans
Authors: Ganley-Leal Lisa M. , Mwinzi Pauline N. , Cetre-Sossah Catherine B. , Andove Julius , Hightower Allen W. , Karanja Diana M. S. , Colley Daniel G. , Secor W. Evan 
Published: March 2006

ABSTRACTLongitudinal investigations of an adult male population of Kenyan car washers who have heavy and quantifiable occupational exposure toSchistosoma mansonicercariae revealed that some individuals develop resistance to reinfection while others remain highly susceptible. We sought to characterize immune correlates associated with host protection in this population. Previous studies have demonstrated an association of peripheral eosinophilia with resistance to reinfection with schistosomes. Thus, we investigated the relationship between the percentage of circulating eosinophils and the effect of human immunodeficiency virus type 1 (HIV-1) coinfection on the susceptibility of the car washers to reinfection with schistosomes. Elevated percentages of circulating eosinophils were associated with resistance to reinfection byS. mansoniin HIV-1-seronegative persons. In the HIV-1-seropositive cohort, low CD4+-T-cell counts were associated with a less intense eosinophilia. Moreover, eosinophils from the car washers expressed high levels of FcεRI β chain, a molecule important in immunoglobulin E (IgE)-mediated immunity. Levels of FcεRI β chain expression correlated with serum levels of total and antigen-specific IgE for HIV-1-negative car washers, but this was not the case for individuals coinfected with HIV-1. Overall, these data further implicate eosinophils as having a potential role in development of protective immunity against schistosomes and suggest that changes associated with HIV-1 coinfection increase susceptibility to reinfection.
Immunization with theHaemophilus ducreyiHemoglobin Receptor HgbA Protects against Infection in the Swine Model of Chancroid
Authors: Afonina Galyna , Leduc Isabelle , Nepluev Igor , Jeter Chrystina , Routh Patty , Almond Glen , Orndorff Paul E. , Hobbs Marcia , Elkins Christopher 
Published: March 2006

ABSTRACTThe etiologic agent of chancroid isHaemophilus ducreyi. To fulfill its obligate requirement for heme,H. ducreyiuses two TonB-dependent receptors: the hemoglobin receptor (HgbA) and a receptor for free heme (TdhA). Expression of HgbA is necessary forH. ducreyito survive and initiate disease in a human model of chancroid. In this study, we used a swine model ofH. ducreyiinfection to demonstrate that an experimental HgbA vaccine efficiently prevents chancroid, as determined by several parameters. Histological sections of immunized animals lacked typical microscopic features of chancroid. All inoculated sites from mock-immunized pigs yielded viableH. ducreyicells, whereas no viableH. ducreyicells were recovered from inoculated sites of HgbA-immunized pigs. Antibodies from sera of HgbA-immunized animals bound to and initiated antibody-dependent bactericidal activity against homologousH. ducreyistrain 35000HP and heterologous strain CIP542 ATCC; however, an isogenichgbAmutant of 35000HP was not killed, proving specificity. Anti-HgbA immunoglobulin G blocked hemoglobin binding to the HgbA receptor, suggesting a novel mechanism of protection through the limitation of heme/iron acquisition byH. ducreyi. Such a vaccine strategy might be applied to other bacterial pathogens with strict heme/iron requirements. Taken together, these data suggest continuing the development of an HgbA subunit vaccine to prevent chancroid.
Cloning, Expression, and Characterization of Fimbrial Operon F9 from Enterohemorrhagic
Escherichia coli
O157:H7
Authors: Low Alison S. , Dziva Francis , Torres Alfredo G. , Martinez Jessenya L. , Rosser Tracy , Naylor Stuart , Spears Kevin , Holden Nicola , Mahajan Arvind , Findlay John , Sales Jill , Smith David G. E. , Low J. Christopher , Stevens Mark P. , Gally David L. 
Published: March 2006

ABSTRACT

Recent transposon mutagenesis studies with two enterohemorrhagic
Escherichia coli
(EHEC) strains, a sero- type O26:H- strain and a serotype O157:H7 strain, led to identification of a putative fimbrial operon that promotes colonization of young calves (1 to 2 weeks old). The distribution of the gene encoding the major fimbrial subunit present in O-island 61 of EHEC O157:H7 in a characterized set of 78 diarrheagenic
E. coli
strains was determined, and this gene was found in 87.2% of the strains and is therefore not an EHEC-specific region. The cluster was amplified by long-range PCR and cloned into the inducible expression vector pBAD18. Induced expression in
E. coli
K-12 led to production of fimbriae, as demonstrated by transmission electron microscopy and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. The fimbriae were purified, and sera to the purified major subunit were raised and used to demonstrate expression from wild-type
E. coli
O157:H7 strains. Induced expression of the fimbriae, designated F9 fimbriae, was used to characterize binding to bovine epithelial cells, bovine gastrointestinal tissue explants, and extracellular matrix components. The fimbriae promoted increases in the levels of
E. coli
K-12 binding only to bovine epithelial cells. In contrast, induced expression of F9 fimbriae in
E. coli
O157:H7 significantly reduced adherence of the bacteria to bovine gastrointestinal explant tissue. This may have been due to physical hindrance of type III secretion-dependent attachment. The main F9 subunit gene was deleted in
E. coli
O157:H7, and the resulting mutant was compared with the wild-type strain for colonization in weaned cattle. While the shedding levels of the mutant were reduced, the animals were still colonized at the terminal rectum, indicating that the adhesin is not responsible for the rectal tropism observed but may contribute to colonization at other sites, as demonstrated previously with very young animals.
Immunization Enhances Inflammation and Tissue Destruction in Response toPorphyromonas gingivalis
Authors: Leone Cataldo W. , Bokhadhoor Haneen , Kuo David , Desta Tesfahun , Yang Julia , Siqueira Michelle F. , Amar Salomon , Graves Dana T. 
Published: March 2006

ABSTRACTIt is well established that host-bacterium interactions play a critical role in the initiation and progression of periodontal diseases. By the use of inhibitors, it has been shown that mediators associated with the innate immune response significantly contribute to the disease process. Less is known regarding the role of the acquired immune response. To investigate mechanisms by which the acquired immune response toPorphyromonas gingivaliscould affect connective tissue, we used a well-documented calvarial model to study host-bacterium interactions. Injection ofP. gingivalisstimulated gamma interferon, interleukin 6, macrophage inflammatory protein 2, and monocyte chemoattractant protein 1 expression as determined by real-time PCR. Prior immunization againstP. gingivalissignificantly enhanced the mRNA levels of these cytokines and chemokines. Similarly, immunization significantly increased and prolonged the formation of a polymorphonuclear leukocyte and mononuclear cell infiltrate (P< 0.05). In addition, the area of connective tissue destruction, osteoclastogenesis, bone loss, mRNA expression of proapoptotic genes, and degree of fibroblast apoptosis were increased in immunized mice (P< 0.05). These results indicate that activation of the acquired immunity byP. gingivalisincreases the inflammatory and destructive responses which occur in part through up-regulating the innate immune response and enhancing osteoclastogenesis and fibroblast apoptosis.
The Host Defense Peptide Beta-Defensin 1 Confers Protection againstBordetella pertussisin Newborn Piglets
Authors: Elahi Shokrollah , Buchanan Rachelle M. , Attah-Poku Sam , Townsend Hugh G. G. , Babiuk Lorne A. , Gerdts Volker 
Published: March 2006

ABSTRACTInnate immunity plays an important role in protection against respiratory infections in humans and animals. Host defense peptides such as beta-defensins represent major components of innate immunity. We recently developed a novel porcine model of pertussis, an important respiratory disease of young children and infants worldwide. Here, we investigated the role of porcine beta-defensin 1 (pBD-1), a porcine defensin homologue of human beta-defensin 2, in conferring protection against respiratory infection withBordetella pertussis. In this model, newborn piglets were fully susceptible to infection and developed severe bronchopneumonia. In contrast, piglets older than 4 weeks of age were protected against infection withB. pertussis. Protection was associated with the expression of pBD-1 in the upper respiratory tract. In fact, pBD-1 expression was developmentally regulated, and the absence of pBD-1 was thought to contribute to the increased susceptibility of newborn piglets to infection withB. pertussis. Bronchoalveolar lavage specimens collected from older animals as well as chemically synthesized pBD-1 displayed strong antimicrobial activity againstB. pertussisin vitro. Furthermore, in vivo treatment of newborn piglets with only 500 μg pBD-1 at the time of challenge conferred protection against infection withB. pertussis. Interestingly, pBD-1 displayed no bactericidal activity in vitro againstBordetella bronchiseptica, a closely related natural pathogen of pigs. Our results demonstrate that host defense peptides play an important role in protection against pertussis and are essential in modulating innate immune responses against respiratory infections.
Monoclonal Antibody Detection of CD46 Clustering beneath
Neisseria gonorrhoeae
Microcolonies
Authors: Weyand Nathan J. , Lee Shaun W. , Higashi Dustin L. , Cawley Daniel , Yoshihara Paul , So Magdalene 
Published: March 2006

ABSTRACT

CD46 (membrane cofactor protein), a complement-regulatory protein that participates in innate and acquired immunity, also serves as a receptor for viral and bacterial pathogens. CD46 isoforms terminate in one of two cytoplasmic tails, Cyt1 or Cyt2, which differ in signaling and trafficking properties. Dissecting the functions of the two cytoplasmic tails in these cellular processes has been hampered by the absence of specific reagents. Here we report the construction of Cyt1- and Cyt2-specific monoclonal antibodies (MAbs). These MAbs recognize unique epitopes within the tails and can be used for immunofluorescence microscopy, immunoblotting, and immunoprecipitation. Studies of
Neisseria gonorrhoeae
-infected cells with the CD46 tail MAbs demonstrate the differential recruitment of Cyt1 and Cyt2 to the cortical plaque.
MyD88 Innate Immune Function in a Zebrafish Embryo Infection Model
Authors: van der Sar Astrid M. , Stockhammer Oliver W. , van der Laan Carina , Spaink Herman P. , Bitter Wilbert , Meijer Annemarie H. 
Published: March 2006

ABSTRACT

Innate immunity signaling mechanisms during vertebrate embryogenesis are largely unknown. To study Toll-like receptor (TLR) signaling function in the zebrafish embryo model, we designed an experimental setup for antisense morpholino knockdown under conditions of bacterial infection. Clearance of
Salmonella enterica
serovar Typhimurium Ra bacteria was significantly impaired after knockdown of myeloid differentiation factor 88 (MyD88), a common adaptor protein in TLR and interleukin-1 receptor signaling. Thereby, we demonstrate for the first time that the innate immune response of the developing embryo involves MyD88-dependent signaling, which further establishes the zebrafish embryo as a model for the study of vertebrate innate immunity.
Active Immunization against
Pneumocystis carinii
with a Recombinant
P. carinii
Antigen
Authors: Wells Jesse , Haidaris Constantine G. , Wright Terry W. , Gigliotti Francis 
Published: March 2006

ABSTRACT

Mice immunized with recombinant mouse
Pneumocystis carinii
antigen A12-thiredoxin fusion protein developed an antibody response that recognized
P. carinii
antigens, as determined by Western blotting and immunofluorescence analysis. Compared to mice immunized with thioredoxin alone, mice immunized with A12-thioredoxin had significantly reduced lung
P. carinii
burdens after CD4
+
T-cell depletion and challenge with
P. carinii
.
Human Neutrophil Calprotectin Reduces the Susceptibility ofBorrelia burgdorferito Penicillin
Authors: Montgomery Ruth R. , Schreck Kimberly , Wang Xiaomei , Malawista Stephen E. 
Published: March 2006

ABSTRACTBorrelia burgdorferi, the spirochetal agent of Lyme disease, is susceptible to killing by a variety of polymorphonuclear leukocyte (PMN) components. Some are most effective against metabolically activeB. burgdorferi. The abundant PMN cytoplasmic protein calprotectin, elevated 10- to 100-fold in inflammation, inhibits the growth of spirochetes through chelation of the essential cation, Zn. Since the action of some therapeutic antibiotics depends on bacterial division, we investigated the antibiotic sensitivities of spirochetes in calprotectin. In physiologic calprotectin,B. burgdorferiis not eliminated by therapeutic doses of penicillin G; in contrast, doxycycline is effective. Calprotectin may modify the clearance of spirochetes at sites of inflammation.
Adaptive Immunity-Dependent Intestinal Hypermotility Contributes to Host Defense againstGiardiaspp
Authors: Andersen Yolanda S. , Gillin Frances D. , Eckmann Lars 
Published: March 2006

ABSTRACTHumans infected withGiardiaexhibit intestinal hypermotility, but the underlying mechanisms and functional significance are uncertain. Here we show in murine models of giardiasis that small-intestinal hypermotility occurs in a delayed fashion relative to peak parasite burden, is dependent on adaptive immune defenses, and contributes to giardial clearance.
Chlamydiae Modulate Gamma Interferon, Interleukin-1β, and Tumor Necrosis Factor Alpha Receptor Expression in HeLa Cells
Authors: Shirey Kari Ann , Carlin Joseph M. 
Published: March 2006

ABSTRACTChlamydia psittaciwas found to modulate receptor expression for the cytokine receptors that are involved in the synergistic induction of indoleamine dioxygenase in epithelial cells. Increases in receptor expression were seen even with inactivatedChlamydia, suggesting that chlamydial antigens and not products of infection are important for up-regulating cytokine receptor expression.