bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dendritic Cells Stimulated withActinobacillus actinomycetemcomitansElicit Rapid Gamma Interferon Responses by Natural Killer Cells
Authors: Kikuchi T. , Hahn C. L. , Tanaka S. , Barbour S. E. , Schenkein H. A. , Tew J. G. 
Published: August 2004

ABSTRACTHuman immunoglobulin G2 (IgG2) responses are gamma interferon (IFN-γ) dependent, and monocyte-derived dendritic cells (mDCs) promote IgG2 production. DCs spontaneously emerge from monocytes in cultures prepared from localized aggressive periodontitis (LagP) patients, and these patients have high levels of IgG2 that is reactive withActinobacillus actinomycetemcomitans. These results prompted the hypothesis that an interaction between mDCs andA. actinomycetemcomitanspromotes IFN-γ production, and IFN-γ is known to promote both immunopathology and protective IgG2.A. actinomycetemcomitansinduced mDCs to produce interleukin-12 (IL-12), and the addition ofA. actinomycetemcomitansand DCs to cultured peripheral blood lymphocytes elicited high levels of IFN-γ within just 24 h. In contrast, IL-4 was not detectable although DC-derived IL-10 production was apparent.A. actinomycetemcomitans-stimulated macrophages prepared from the same monocytes lacked the ability to induce IL-12 or IFN-γ responses. NK cells of the innate immune system were the primary source of this early IFN-γ, although CD8 T cells also contributed some. The NK cell-derived IFN-γ was IL-12 dependent, andA. actinomycetemcomitans-DC interactions were Toll-like receptor 4 dependent.A. actinomycetemcomitansandA. actinomycetemcomitanslipopolysaccharide (LPS) were more potent thanEscherichia coliandE. coliLPS in the ability to induce DC IL-12 and IFN-γ. The ability ofA. actinomycetemcomitans-stimulated DCs to induce NK cells to rapidly produce IFN-γ in the absence of detectable IL-4 suggests their potential for skewing responses toward Th1. This may help explain the presence of Th1-associated cytokines in gingival crevicular fluid (GCF) from LagP patients and the high levels of IgG2 in their serum and GCF that is reactive withA. actinomycetemcomitans.
Major Histocompatibility Complex Class I Peptide Presentation afterSalmonella entericaSerovar Typhimurium Infection Assessed via Stable Isotope Tagging of the B27-Presented Peptide Repertoire
Authors: Ringrose Jeffrey H. , Meiring Hugo D. , Speijer Dave , Feltkamp Theodorus E. W. , van Els Cecile A. C. M. , de Jong Ad P. J. M. , Dankert Jacob 
Published: August 2004

ABSTRACTReactive arthritis (ReA) induced by infection with several gram-negative bacteria is strongly associated with expression of the major histocompatibility complex class I molecule HLA-B27. It is thought that due to the intracellular lifestyle of ReA-inducing bacteria, bacterial fragments can be presented by HLA-B27. Cytotoxic T cells recognizing such bacterial peptides or other induced host peptides could cross-react with self peptides presented in the joints, giving rise to disease. Studies to analyze the B27 peptide repertoire in relation to infection were severely hampered, as complex peptide profiles obtained from separate infected and noninfected cell preparations had to be compared. For this study, we applied a new approach to examine the effect ofSalmonella entericaserovar Typhimurium infection on the B27 peptide repertoire presented by the HLA-B*2704 subtype associated with disease. Firstly, we showed that both host cell andS. entericaserovar Typhimurium proteins can be tagged metabolically with stable-isotope-labeled arginine. We then designed experiments so that either the tagged endogenous or tagged bacterial B*2704-presented peptide repertoires from infected cells could be analyzed by mass spectrometry from single peptide preparations that included uninfected controls. Using this new approach, we found no evidence for significant changes in endogenous B*2704 peptide presentation after infection or for anyS. entericaserovar Typhimurium-derived B27-bound peptide. In conclusion, the hypothesis thatS. entericaserovar Typhimurium induces changes in B27 peptide presentation could not be supported.
Senescent BALB/c Mice Are Able To Develop Resistance toLeishmania majorInfection
Authors: Ehrchen Jan , Sindrilaru Anca , Grabbe Stephan , Schönlau Frank , Schlesiger Christian , Sorg Clemens , Scharffetter-Kochanek Karin , Sunderkötter Cord 
Published: August 2004

ABSTRACTAging has been associated with a decline in immunocompetence and resistance to infections, partially due to dysregulated NO production by macrophages and deficits in mounting Th2 cell responses. We wondered if these alterations would reverse the immune response in experimental leishmaniasis. Bone-marrow-derived macrophages from 2- and 18-month-old (senescent) C57BL/6 or BALB/c mice showed no marked difference in leishmanicidal functions. In vivo infections of resistant C57BL/6 mice withLeishmania majorrevealed no difference between senescent and young mice. However, among susceptible BALB/c mice, senescent animals showed less foot-pad swelling than young mice, and 40 to 60% of them even showed healing of ulcers, reduced parasite dissemination, and a Th1 cell response. These changes were associated with a spontaneous release of interleukin-12 (IL-12) by macrophages from aged but not from young mice. Since exogenous microbial stimulation can influence immune responses during aging, we also infected senescent mice who were raised under specific-pathogen-free (SPF) conditions. They showed neither resistance nor a Th1 response, but their macrophages still spontaneously released IL-12. A microbiological analysis showed that conventionally kept mice, but not SPF mice, had experienced infection with murine hepatitis virus (MHV), an infection associated with a Th1-like response. We conclude that for the reversal of the immune response, senescence is the premier requirement but needs to be completed by another mandatory event such as microbial stimulation. One of the age-related, but not environment-related, factors is the spontaneous release of IL-12 by macrophages, while confrontation with MHV presents an environment-related difference, with both having the potential to support a Th1 response.
SseK1 and SseK2 Are Novel Translocated Proteins ofSalmonella entericaSerovar Typhimurium
Authors: Kujat Choy Sonya L. , Boyle Erin C. , Gal-Mor Ohad , Goode David L. , Valdez Yanet , Vallance Bruce A. , Finlay B. Brett 
Published: August 2004

ABSTRACTSalmonella entericais a gram-negative, facultative intracellular pathogen that causes disease symptoms ranging from gastroenteritis to typhoid fever. A key virulence strategy is the translocation of bacterial effector proteins into the host cell, mediated by the type III secretion systems (TTSSs) encoded inSalmonellapathogenicity island 1 (SPI-1) and SPI-2. InS. entericaserovar Typhimurium LT2, we identified the protein products ofSTM4157andSTM2137as novel candidate secreted proteins by comparison to known secreted proteins from enterohemorrhagicEscherichia coliandCitrobacter rodentium. The STM4157 and STM2137 proteins, which we have designated SseK1 and SseK2, respectively, are 61% identical at the amino acid level and differ mainly in their N termini. Western analysis showed that in vitro accumulation and secretion of these proteins in serovar Typhimurium were affected by mutations in the two-component systems SsrA/B and PhoP/Q, which are key mediators of intracellular growth and survival. SPI-2 TTSS-dependent translocation of recombinant SseK1::Cya was evident at 9 h postinfection of epithelial cells, while translocation of SseK2::Cya was not detected until 21 h. Remarkably, the translocation signal for SseK1 was contained within the N-terminal 32 amino acids. Fractionation of infected epithelial cells revealed that following translocation SseK1 localizes to the host cytosol, which is unusual among the currently knownSalmonellaeffectors. Phenotypic analysis of ΔsseK1, ΔsseK2, and ΔsseK1/ΔsseK2mutants provided evidence for a role that was not critical during systemic infection. In summary, this work demonstrates that SseK1 and SseK2 are novel translocated proteins of serovar Typhimurium.
Contribution of
Burkholderia cenocepacia
Flagella to Infectivity and Inflammation
Authors: Urban Teresa A. , Griffith Adam , Torok Anastasia M. , Smolkin Mark E. , Burns Jane L. , Goldberg Joanna B. 
Published: August 2004

ABSTRACT

Burkholderia cenocepacia
is an opportunistic pathogen that can cause severe lung infections in cystic fibrosis patients. To understand the contribution of
B. cenocepacia
flagella to infection, a strain mutated in the major flagellin subunit,
fliCII
, was constructed in
B. cenocepacia
K56-2 and tested in a murine agar bead model of lung infection. C57/BL6 mice infected with ∼10
8
wild-type K56-2 bacteria exhibited 40% mortality after 3 days, whereas no mortality was noted in mice infected with the
fliCII
mutant. Among the mice surviving the infection with either strain, there was no significant difference in the bacterial loads in the lungs and spleen, bacteremia, weight loss, or infiltration of immune effector cells at 3 days postinfection. Similar results were observed at 24 h, prior to expression of the lethality phenotype. KC, a murine interleukin-8 (IL-8) homolog, was elevated in both the bronchoalveolar lavage fluid and serum of mice infected with the wild type compared to the
fliCII
mutant at 24 h, suggesting that flagella stimulated host cells. To demonstrate that flagella contributed to these responses, the interaction between
B. cenocepacia
and Toll-like receptor 5 (TLR5) was investigated. Infection of HEK293 cells with heat-killed wild-type K56-2, but not infection with the
fliCII
mutant, resulted in both NF-κB activation and IL-8 secretion that was dependent upon expression of TLR5. Together, these results demonstrate that
B. cenocepacia
flagella contribute to virulence in an in vivo infection model, and that induction of host immune responses through interaction with TLR5 may contribute to its overall pathogenic potential.
Gamma Interferon Responses toPlasmodium falciparumLiver-Stage Antigen 1 and Thrombospondin-Related Adhesive Protein and Their Relationship to Age, Transmission Intensity, and Protection against Malaria
Authors: John Chandy C. , Moormann Ann M. , Sumba Peter O. , Ofulla Ayub V. , Pregibon Daniel C. , Kazura James W. 
Published: August 2004

ABSTRACTGamma interferon (IFN-γ) responses to thePlasmodium falciparumantigens liver-stage antigen 1 (LSA-1) and thrombospondin-related adhesive protein (TRAP) are thought to be important in protection against malaria. Optimal methods of testing and the effects of age and transmission intensity on these responses are unknown. IFN-γ responses to LSA-1 and TRAP peptides were assessed by the enzyme-linked immunospot assay (ELISPOT) and enzyme-linked immunosorbent assay (ELISA) in children and adults from areas of stable and unstable malaria transmission in Kenya. Adults in the areas of stable and unstable transmission had similar frequencies and levels of IFN-γ responses to LSA-1 and TRAP as determined by ELISPOT and ELISA. In contrast, IFN-γ responses to the LSA-1 T3 peptide (assessed by ELISPOT) and to any LSA-1 peptide (assessed by ELISA) were less frequent in children in the area of unstable transmission than in children in the area of stable transmission. IFN-γ responses to LSA-1 were more frequently detected by ELISA than by ELISPOT in the stable-transmission area. IFN-γ responses detected by ELISA and ELISPOT did not correlate with each other. In children in the stable-transmission area, IFN-γ responses to LSA-1 peptides assessed by ELISA, but not by ELISPOT, were associated with protection against clinical malaria and anemia. IFN-γ responses to LSA-1 appear to require repeatedP. falciparumexposure and/or increased age and, as measured by ELISA, are associated with protection against clinical malaria and anemia.
Differential Requirements for VirB1 and VirB2 during
Brucella abortus
Infection
Authors: den Hartigh Andreas B. , Sun Yao-Hui , Sondervan David , Heuvelmans Niki , Reinders Marjolein O. , Ficht Thomas A. , Tsolis Renée M. 
Published: August 2004

ABSTRACT

The
Brucella abortus virB
operon, encoding a type IV secretion system (T4SS), is required for intracellular replication and persistent infection in the mouse model. The products of the first two genes of the
virB
operon,
virB1
and
virB2
, are predicted to be localized at the bacterial surface, where they could potentially interact with host cells. Studies to date have focused on characterization of transposon mutations in these genes, which are expected to exert polar effects on downstream genes in the operon. In order to determine whether VirB1 and VirB2 are required for the function of the T4SS apparatus, we constructed and characterized nonpolar deletion mutations of
virB1
and
virB2
. Both mutants were shown to be nonpolar, as demonstrated by their ability to express the downstream gene
virB5
during stationary phase of growth in vitro. Both VirB1 and VirB2 were essential for intracellular replication in J774 macrophages. The nonpolar
virB2
mutant was unable to cause persistent infection in the mouse model, demonstrating the essential role of VirB2 in the function of the T4SS apparatus during infection. In contrast, the nonpolar
virB1
mutant persisted at wild-type levels, showing that the function of VirB1 is dispensable in the mouse model of persistent infection.
Mycobacterium tuberculosisTriggers Apoptosis in Peripheral Neutrophils Involving Toll-Like Receptor 2 and p38 Mitogen Protein Kinase in Tuberculosis Patients
Authors: Alemán Mercedes , Schierloh Pablo , de la Barrera Silvia S. , Musella Rosa M. , Saab María A. , Baldini Matías , Abbate Eduardo , Sasiain María C. 
Published: August 2004

ABSTRACTPolymorphonuclear neutrophils (PMN) exposed toMycobacterium tuberculosisdisplay bactericidal responses and produce inflammatory proteins. This PMN-mediated inflammatory response is regulated by an activation of the apoptotic program, which collaborates to avoid tissue injury. In vitro, circulating PMN from patients with tuberculosis (TB) show an increased spontaneous apoptosis, andM. tuberculosis-induced activation accelerates the PMN apoptosis. In this study, we evaluated the mechanisms involved in spontaneous andM. tuberculosis-induced apoptosis. We demonstrate that apoptosis of PMN is not induced by lipoarabinomannan or by a whole-cell lysate ofM. tuberculosisand that neither tumor necrosis factor alpha nor CD11b, CD14, and Fcγ receptors are involved. Apoptosis of PMN from patients with active TB (TB-PMN) is induced by the interaction with the wholeM. tuberculosisvia Toll-like receptor 2 (TLR2), and, in contrast to spontaneous apoptosis, it involves the p38 mitogen-activated protein kinase (MAPK) pathway. These results correlate with a high expression of phosphorylated p38 (p-p38) in circulating TB-PMN and with the ability ofM. tuberculosisto induce in vitro the expression of p-p38 in PMN. Therefore, when the bacterial burden is low, TB-PMN could be detecting nonopsonizedM. tuberculosisvia TLR2, leading to the activation of the p38 MAPK pathway, which in turn would induce PMN activation and apoptosis. This mechanism needs further confirmation at the site of infection.
Proteus mirabilis
ZapA Metalloprotease Degrades a Broad Spectrum of Substrates, Including Antimicrobial Peptides
Authors: Belas Robert , Manos Jim , Suvanasuthi Rooge 
Published: August 2004

ABSTRACT

The 54-kDa extracellular metalloprotease ZapA is an important virulence factor of uropathogenic
Proteus mirabilis
. While ZapA has the ability to degrade host immunoglobulins (Igs), the dramatic attenuation of virulence in ZapA mutants suggests that this enzyme may have a broader spectrum of activity. This hypothesis was tested by in vitro assays with purified ZapA and an array of purified protein or peptide substrates. The data reveal that many proteins found in the urinary tract are substrates of ZapA proteolysis, including complement (C1q and C3), cell matrix (collagen, fibronectin, and laminin), and cytoskeletal proteins (actin and tubulin). Proteolysis of IgA and IgG was significantly enhanced by conditions that denatured the Igs. It was discovered that the antimicrobial peptides human β-defensin 1 (hBD1) and LL-37 are readily cleaved by the enzyme. To the best of our knowledge, this is the first report of a bacterial protease capable of cleaving hBD1, a component of the human renal tubule innate immune response. Proteolysis of hBD1 resulted in ca. six peptides, while proteolysis of LL-37 resulted in at least nine products. Matrix-assisted laser desorption ionization-time of flight mass spectrometry analysis of the molecular masses of the reaction products indicated that ZapA preferred no distinct peptide bond. The antimicrobial activity of hBD1 and LL-37 was significantly reduced following ZapA treatment, suggesting that proteolysis results in inactivation of these peptides. The data suggest that a function of ZapA during urinary tract infections is the proteolysis of antimicrobial peptides associated with the innate immune response.
Chemokine Gene Expression in Toll-Like Receptor-Competent and -Deficient Mice Infected with
Leishmania major
Authors: Antoniazi Simone , Price Helen P. , Kropf Pascale , Freudenberg Marina A. , Galanos Chris , Smith Deborah F. , Müller Ingrid 
Published: August 2004

ABSTRACT

We studied the expression of a subset of chemokines, including RANTES/CCL5, MIP-1α/CCL3, IP-10/CXCL10, and MCP-1/CCL2, in Toll-like receptor (TLR)-competent and -deficient mice after infection with
Leishmania major
. Chemokine expression at the site of infection (the footpad), in the draining lymph nodes and in the spleens of infected animals was determined by using two different methods of analysis. The results indicate that
L. major
infection causes overall upregulation of RANTES/CCL5, MIP-1α/CCL3, IP-10/CXCL10, and MCP-1/CCL2 in the footpads and lymph nodes, while expression of these chemokines is constitutive in the spleens of TLR4-competent mice (C57BL/10ScSn) and TLR4-deficient mice (C57BL10/ScN). Different patterns of expression were detected depending on the time postinfection, but there was little variation in the expression of these four chemokines in the presence or absence of TLR4.
Age-Related Resistance of C57BL/6 Mice toCryptococcus neoformansIs Dependent on Maturation of NKT Cells
Authors: Blackstock Rebecca , Murphy Juneann W. 
Published: August 2004

ABSTRACTConflicting results have been reported regarding the ability of C57BL/6 mice to clear infections due toCryptococcus neoformans. Examination of the various experimental protocols used suggested that C57BL/6 mice might develop the ability to resist infection as they mature. We analyzed the ability of C57BL/6 mice of different ages to respond to immunization with cryptococcal antigen or to clear a cryptococcal infection. Mice were immunized with a soluble cryptococcal culture filtrate antigen (CneF) emulsified in complete Freund's adjuvant (CneF-CFA). Delayed-type hypersensitivity (DTH) reactions elicited by the immunization were significantly stronger in 15-week-old C57BL/6 mice than in 7-week-old mice. Analysis of cryptococcal CFU 8 weeks following intratracheal infection of 7-week-old mice or 15-week-old mice revealed a relative inability of the younger animals to control the infection. Six-week-old immunized and infected mice cleared cryptococci from brain, spleen, and liver in a manner similar to that of immunized and infected 15-week-old mice. However, the older mice cleared cryptococci much more efficiently from the lungs. The possible role for NKT cells was determined by passive transfer of thymocytes from 10-week-old mice (containing mature NKT cells) or 2-week-old mice (containing immature NKT cells) to 6-week-old mice. The 10-week-old thymocytes significantly enhanced the ability of the mice to develop a DTH response after immunization with CneF-CFA, while animals treated with 2-week-old thymocytes did not improve their DTH response after immunization. The cells in the 10-week-old thymocyte population responsible for improvement of DTH responses were identified as being NK1.1 positive.
Helicobacter pylori
Infection Targets Adherens Junction Regulatory Proteins and Results in Increased Rates of Migration in Human Gastric Epithelial Cells
Authors: Conlin Victoria S. , Curtis Susan B. , Zhao Ying , Moore Edwin D. W. , Smith Valerie C. , Meloche R. Mark , Finlay B. Brett , Buchan Alison M. J. 
Published: August 2004

ABSTRACT

The human gastric pathogen
Helicobacter pylori
attaches to antral epithelial cells in vivo. Cultured human antral epithelial cells, AGS and NCI-N87 cell lines, were grown in the absence or presence of
H. pylori
and compared with respect to gene transcript levels, protein expression, organization of the actin cytoskeleton, and the regulation of cell migration. The Clontech Neurobiology array detected differentially expressed transcripts, while Western blots were used to investigate related changes in protein levels. Infection with
H. pylori
consistently upregulated annexin II, S100 A7, Rho-GTP, and IQGAP-1, whereas SSTR-1 was downregulated upon
H. pylori
infection. In the adherens junction, E-cadherin and IQGAP-1 were translocated from the plasma membrane to intracellular vesicles. The primary and NCI-N87 cells were similar with respect to cell-cell and cell-matrix adhesion and cell migratory behavior; in contrast the AGS cells were significantly different from the primary gastric epithelial cell preparations, and thus caution must be used when using this cell line for studies of gastric disease. These studies demonstrate a correlation between
H. pylori
infection and alterations to epithelial cell adhesion molecules, including increased levels of Rho-GTP and cell migration. These data indicate that destabilizing epithelial cell adherence is one of the factors increasing the risk of
H. pylori
-infected individuals developing gastric cancer.
The Cyclic AMP-Dependent Protein Kinase A Network Regulates Development and Virulence in
Aspergillus fumigatus
Authors: Liebmann Burghard , Müller Meike , Braun Armin , Brakhage Axel A. 
Published: August 2004

ABSTRACT

Aspergillus fumigatus
is an important pathogen of immunocompromised hosts, causing pneumonia and invasive disseminated disease with high mortality. To determine the importance of the cyclic AMP (cAMP) signaling pathway for virulence, the
pkaC1
gene encoding a protein kinase A (PKA) catalytic subunit was cloned and characterized. Deletion of
pkaC1
led to reduced conidiation and growth. PKA activity was not detectable in Δ
pkaC1
, Δ
gpaB
, and Δ
acyA
mutant strains.
gpaB
and
acyA
encode a G protein α subunit involved in cAMP signal transduction and adenylate cyclase, respectively. Addition of cAMP led to PKA activity in crude extracts of both the Δ
gpaB
and Δ
acyA
strains but not in crude extracts of the Δ
pkaC1
strain. These findings provide evidence that PKAC1 represents the predominant form of PKA under the conditions tested, and GPAB and ACYA are members of the cAMP signaling cascade. Analysis of a
pksP
p-
lacZ
gene fusion indicated that the expression of the pathogenicity determinant-encoding
pksP
gene was reduced in Δ
pkaC1
mutant strains compared with the expression of the gene fusion in the parental strain. In a low-dose murine inhalation model, conidia of both the Δ
pkaC1
and Δ
gpaB
mutant strains were almost avirulent. Taken together, these findings indicate that the cAMP-PKA signal transduction pathway is required for
A. fumigatus
pathogenicity.