bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biological Trojan Horse: Antigen 43 Provides Specific Bacterial Uptake and Survival in Human Neutrophils
Authors: Fexby Sara , Bjarnsholt Thomas , Jensen Peter Østrup , Roos Viktoria , Høiby Niels , Givskov Michael , Klemm Per 
Published: December 2006

ABSTRACTEscherichia coliis a versatile pathogen causing millions of infections in humans every year. This bacterium can form multicellular aggregates when it expresses a self-associating protein, antigen 43 (Ag43), on its surface. We have discovered that Ag43-expressingE. colicells are efficiently taken up by human defense cells, polymorphonuclear neutrophils (PMNs), in an opsonin-independent manner. Surprisingly, the phagocytosed bacteria were not immediately killed but resided as tight aggregates within the PMNs. Our observations indicate that Ag43-mediated uptake and survival in PMNs constitute a mechanism to subvert one of the primary defense mechanisms of the human body.
Escherichia coli
from Urine of Female Patients with Urinary Tract Infections Is Competent for Intracellular Bacterial Community Formation
Authors: Garofalo Corinne K. , Hooton Thomas M. , Martin Steven M. , Stamm Walter E. , Palermo Joseph J. , Gordon Jeffrey I. , Hultgren Scott J. 
Published: December 2006

ABSTRACT

Nearly 50% of women experience at least one urinary tract infection (UTI) in their lifetime. Studies with mice have revealed that uropathogenic
Escherichia coli
(UPEC) isolates invade superficial umbrella cells that line the bladder, allowing them to find a safe haven and subvert clearance by innate host responses. Rapid intracellular replication results in the formation of distinctive intracellular bacterial communities (IBCs). In this study, we evaluated whether UPEC strains cultured from the urine of women and classified as causing acute cystitis, recurrent cystitis, asymptomatic bacteriuria, or pyelonephritis could progress through the IBC cascade in a well-characterized mouse model of cystitis. Of 18 UPEC isolates collected from women, 15 formed IBCs. Variations in the size, number, and kinetics of IBC formation were observed with strains isolated from women with different clinical syndromes. Two of the three isolates that did not form IBCs when inoculated alone were able to do so when coinoculated with an isolate that was capable of generating IBCs. The mixed infections dramatically altered the behavior of the coinfecting bacteria relative to their behavior in a single infection. The study also showed that mice with five different genetic backgrounds can support IBC formation. Although UPEC isolates differ genetically in their virulence factors, the majority of UPEC isolates from different types of UTI proceed through the IBC pathway, confirming the generality of IBCs in UTI pathogenesis in mice.
Differential Clearance and Immune Responses to Tick Cell-Derived versus Macrophage Culture-DerivedEhrlichia chaffeensisin Mice
Authors: Ganta Roman R. , Cheng Chuanmin , Miller Elizabeth C. , McGuire Bridget L. , Peddireddi Lalitha , Sirigireddy Kamesh R. , Chapes Stephen K. 
Published: December 2006

ABSTRACTHuman monocytic ehrlichiosis is caused by a tick-transmitted rickettsia,Ehrlichia chaffeensis. We recently reported thatE. chaffeensisgrown in tick cells expresses different proteins than bacteria grown in macrophages. Therefore, we tested the hypothesis that immune responses againstE. chaffeensiswould be different if the mice are challenged with bacteria grown in macrophages or tick cells. We assessed theE. chaffeensisclearance from the peritoneum, spleen, and liver by C57BL/6J mice using a TaqMan-based real-time reverse transcription-PCR assay. Macrophage-grownE. chaffeensiswas cleared in 2 weeks from the peritoneum, whereas the pathogen from tick cells persisted for nine additional days and included three relapses of increasing bacterial load separated by three-day intervals. Tick cell-grown bacteria also persisted in the livers and spleens with higher bacterial loads compared to macrophage-grown bacteria and fluctuated over a period of 35 days. Three-day periodic cycles were detected in T-cell CD62L/CD44 ratios in the spleen and bone marrow in response to infections with both tick cell- and macrophage-grown bacteria and were accompanied by similar periodic cycles of spleen cell cytokine secretions and nitric oxide and interleukin-6 by peritoneal macrophages. TheE. chaffeensis-specific immunoglobulin G response was considerably higher and steadily increased in mice infected with the tick cell-derivedE. chaffeensiscompared to DH82-grown bacteria. In addition, antigens detected by the immunoglobulins were significantly different between mice infected with theE. chaffeensisoriginating from tick cells or macrophages. The differences in the immune response to tick cell-grown bacteria compared to macrophage-grown bacteria reflected a delay in the shift of gene expression from the tick cell-specific Omp 14 gene to the macrophage-specific Omp 19 gene. These data suggest that the host response toE. chaffeensisdepends on the source of the bacteria and that this experimental model requires the most natural inoculum possible to allow for a realistic understanding of host resistance.
Staphylococcal Enterotoxin B In Vivo Modulates both Gamma Interferon Receptor Expression and Ligand-Induced Activation of Signal Transducer and Activator of Transcription 1 in T Cells
Authors: Plaza R. , Rodriguez-Sanchez J. L. , Juarez C. 
Published: December 2006

ABSTRACTSuperantigens (SAg) are bacterial exotoxins that provoke extreme responses in the immune system; for example, the acute hyperactivation of SAg-reactive T cells that leads to toxic shock syndrome is followed within days by strong immunosuppression. The gamma interferon (IFN-γ) response is deeply affected in both extremes. The implication of IFN-γ in the pathophysiology of lethal shock induced in mice after a secondary challenge with the SAg staphylococcal enterotoxin B (SEB) prompted us to study the regulation of IFN-γ secretion and the intracellular response. We demonstrate in this study that a rechallenge with SEB becomes lethal only when given inside a critical time window after SEB priming and is associated with an increase of IFN-γ serum release 72 h after priming. However, at this time, a selective blockade of IFN-γ/STAT1 signaling develops in spleen cells, correlating with a lack of expression of the IFN-γ receptor beta subunit and STAT1 in the T-cell population. Selective blockade of the STAT1 signaling pathway—while simultaneously maintaining STAT3 signaling and expression—may be a protective mechanism that shortens IFN-γ production during the Th1 effector response. This blockade may also have consequences on switching towards a suppressor phenotype with chronic exposure to the superantigen.
High Levels of CXCL10 Are Produced by Intestinal Epithelial Cells in AIDS Patients with Active Cryptosporidiosis but Not after Reconstitution of Immunity
Authors: Wang Heuy-Ching , Dann Sara M. , Okhuysen Pablo C. , Lewis Dorothy E. , Chappell Cynthia L. , Adler Douglas G. , White A. Clinton 
Published: December 2006

ABSTRACT

Chemokines play key roles in attracting immune cells to sites of infections. However, few data on chemokine expression in the gut during human infections are available. We examined expression of chemokines in intestinal tissues of AIDS patients during active
Cryptosporidium
infection and during resolution of such an infection. The chemokines and cytokines in cell lysates from jejunal biopsy tissues were assayed by a 22-multiplex bead immunoassay. CXCL10 (IP-10) and its receptor, CXCR3, in sections were studied by immunohistochemistry. In biopsies from AIDS patients with active cryptosporidiosis, four chemokines (CXCL10, CCL11 [eotaxin], CCL5 [RANTES], and CCL2 [monocyte chemoattractant protein 1]) and three cytokines (interleukin-1α [IL-1α], IL-10, and granulocyte colony-stimulating factor) were detected. The level of CXCL10 was significantly increased in AIDS patients with cryptosporidiosis compared to the level in AIDS patients without cryptosporidiosis or in normal volunteers (median in AIDS patients with cryptosporidiosis, 508 pg/mg protein, compared to 111 pg/mg and 72 pg/mg protein in AIDS patients without cryptosporidiosis and in normal volunteers, respectively [
P
< 0.05 and
P
< 0.005, respectively, as determined by a Mann-Whitney test]). The level of CXCL10 correlated with the parasite burden (as measured by the number of
Cryptosporidium
oocysts in the stools) and also with the IL-1α concentration (Pearson correlation values, 0.961 [
P
< 0.01] and 0.737 [
P
< 0.05]). As determined by immunohistochemistry, CXCL10 localized to epithelial cells at the site of infection. Following effective antiparasite and antiretroviral therapy,
Cryptosporidium
infections resolved, and the levels of CXCL10 decreased to normal levels. We hypothesized that CXCL10 plays an important role in the resolution of cryptosporidiosis by attracting immune effector cells to the site of infection. By contrast, in AIDS patients lacking effector cells, CXCL10 may contribute to the immunopathogenesis by recruiting inflammatory cells.
Serratia marcescensSerralysin Induces Inflammatory Responses through Protease-Activated Receptor 2
Authors: Kida Yutaka , Inoue Hiroyoshi , Shimizu Takashi , Kuwano Koichi 
Published: December 2006

ABSTRACTTheSerratia marcescens-derived protease serralysin is considered to play an important role in the pathogenesis of infection. Protease-activated receptor 2 (PAR-2) is activated by trypsin and also several other trypsin-like serine proteases, leading to the modulation of inflammatory and immune responses. However, little is known about the activation of PAR-2 by bacterial proteases and its roles in bacterial infection. In this study, we investigated whetherS. marcescensserralysin activates host inflammatory responses through PAR-2. Our results demonstrated that serralysin induces interleukin-6 (IL-6) and IL-8 mRNA expression in a human lung squamous cell carcinoma, EBC-l cells. In addition, serralysin activated activator protein 1 (AP-1)-, CCAAT/enhancer-binding protein (C/EBP)-, and nuclear factor-κB (NF-κB)-driven promoters in EBC-1 cells. An electrophoretic mobility shift assay showed that serralysin activates the binding of AP-1, C/EBPβ, and NF-κB in the cells. Inactivation of serralysin resulted in the failure of transactivation of AP-1-, C/EBP-, and NF-κB-driven promoters in the cells. Furthermore, serralysin activated AP-1-, C/EBP-, and NF-κB-driven promoters via PAR-2 in HeLa cells. PAR-2 antagonist peptides decreased serralysin-induced transactivation of AP-1-, C/EBP-, and NF-κB-driven promoters in EBC-1 cells. Considered together, these results suggest that serralysin requires PAR-2 to activate the critical transcription factors AP-1, C/EBPβ, and NF-κB for host inflammatory responses.
Respiratory Tract Infection withMycoplasma pneumoniaein Interleukin-12 Knockout Mice Results in Improved Bacterial Clearance and Reduced Pulmonary Inflammation
Authors: Salvatore C. M. , Fonseca-Aten M. , Katz-Gaynor K. , Gomez A. M. , Mejias A. , Somers C. , Chavez-Bueno S. , McCracken G. H. , Hardy R. D. 
Published: December 2006

ABSTRACTMycoplasma pneumoniaeis a leading cause of pneumonia and is associated with asthma. Evidence linksM. pneumoniaerespiratory disease severity with interleukin-12 (IL-12) concentration in respiratory secretions. We evaluated the microbiologic, inflammatory, and pulmonary function indices ofM. pneumoniaepneumonia in IL-12 (p35) knockout (KO) mice and wild-type (WT) mice to determine the role of IL-12 inM. pneumoniaerespiratory disease. Eight-week-old wild-type BALB/c mice and 8-week-old IL-12 (p35) KO BALB/c mice were inoculated once intranasally with 107CFU ofM. pneumoniae. Mice were evaluated at days 2, 4, and 7 after inoculation. Outcome variables included quantitative bronchoalveolar lavage (BAL)M. pneumoniaeculture, lung histopathologic scores (HPS), BAL cytokine concentrations determined by enzyme-linked immunosorbent assay (tumor necrosis factor alpha [TNF-α], gamma interferon [IFN-γ], IL-1β, IL-2, IL-4, IL-5, IL-6, IL-10, and granulocyte-macrophage colony-stimulating factor) and plethysmography, before and after methacholine, to assess airway obstruction (AO) and airway hyperreactivity (AHR). IL-12 (p35) KO mice infected withM. pneumoniaewere found to have significantly lower BALM. pneumoniaeconcentrations compared withM. pneumoniae-infected WT mice. Lung HPS and the parenchymal pneumonia subscores (neutrophilic alveolar infiltrate), as well as AO, were significantly lower in infected KO mice. No difference was found for AHR. Infected KO mice had significantly lower BAL concentrations of IFN-γ than WT mice; a trend toward lower BAL concentrations was observed for IL-10 (P= 0.065) and TNF-α (P= 0.078). No differences were found for IL-1β, IL-2, IL-4, IL-5, or IL-6. The lack of IL-12 in experimentalM. pneumoniaepneumonia was associated with less severe pulmonary disease and more rapid microbiologic and histologic resolution.
In Vivo Gene Expression Analysis Identifies Genes Required for Enhanced Colonization of the Mouse Urinary Tract by Uropathogenic
Escherichia coli
Strain CFT073
dsdA
Authors: Haugen Brian J. , Pellett Shahaireen , Redford Peter , Hamilton Holly L. , Roesch Paula L. , Welch Rodney A. 
Published: December 2006

ABSTRACT

Deletional inactivation of the gene encoding
d
-serine deaminase,
dsdA
, in uropathogenic
Escherichia coli
strain CFT073 results in a hypermotile strain with a hypercolonization phenotype in the bladder and kidneys of mice in a model of urinary tract infection (UTI). The in vivo gene expression profiles of CFT073 and CFT073
dsdA
were compared by isolating RNA directly from the urine of mice challenged with each strain individually. Hybridization of cDNAs derived from these samples to CFT073-specific microarrays allowed identification of genes that were up- or down-regulated in the
dsdA
deletion strain during UTI. Up-regulated genes included the known
d
-serine-responsive gene
dsdX
, suggesting in vivo intracellular accumulation of
d
-serine by CFT073
dsdA.
Genes encoding F1C fimbriae, both copies of P fimbriae, hemolysin, OmpF, a dipeptide transporter DppA, a heat shock chaperone IbpB, and clusters of open reading frames with unknown functions were also up-regulated. To determine the role of these genes as well as motility in the hypercolonization phenotype, mutants were constructed in the CFT073
dsdA
background and tested in competition against the wild type in the murine model of UTI. Strains with deletions of one or both of the two P fimbrial operons,
hlyA
,
fliC
,
ibpB
, c0468, locus c3566 to c3568, or c2485 to c2490 colonized mouse bladders and kidneys at levels indistinguishable from wild type. CFT073
dsdA
c2398 and CFT073
dsdA focA
maintained a hypercolonization phenotype. A CFT073
dsdA dppA
mutant was attenuated 10- to 50-fold in its colonization ability compared to CFT073. Our results support a role for
d
-serine catabolism and signaling in global virulence gene regulation of uropathogenic
E. coli
.
Microbial Metalloproteinases Mediate Sensing of Invading Pathogens and Activate Innate Immune Responses in the Lepidopteran Model Host
Galleria mellonella
Authors: Altincicek Boran , Linder Monica , Linder Dietmar , Preissner Klaus T. , Vilcinskas Andreas 
Published: December 2006

ABSTRACT

Thermolysin-like metalloproteinases such as aureolysin, pseudolysin, and bacillolysin represent virulence factors of diverse bacterial pathogens. Recently, we discovered that injection of thermolysin into larvae of the greater wax moth,
Galleria mellonella
, mediated strong immune responses. Thermolysin-mediated proteolysis of hemolymph proteins yielded a variety of small-sized (<3 kDa) protein fragments (protfrags) that are potent elicitors of innate immune responses. In this study, we report the activation of a serine proteinase cascade by thermolysin, as described for bacterial lipopolysaccharides (LPS), that results in subsequent prophenoloxidase activation leading to melanization, an elementary immune defense reaction of insects. Quantitative real-time reverse transcription-PCR analyses of the expression of immune-related genes encoding the inducible metalloproteinase inhibitor, gallerimycin, and lysozyme demonstrated increased transcriptional rates after challenge with purified protfrags similar to rates after challenge with LPS. Additionally, we determined the induction of a similar spectrum of immune-responsive proteins that were secreted into the hemolymph by using comparative proteomic analyses of hemolymph proteins from untreated larvae and from larvae that were challenged with either protfrags or LPS. Since
G. mellonella
was recently established as a valuable pathogenicity model for
Cryptococcus neoformans
infection, the present results add to our understanding of the mechanisms of immune responses in
G. mellonella
. The obtained results support the proposed danger model, which suggests that the immune system senses endogenous alarm signals during infection besides recognition of microbial pattern molecules.
Characterization of the
Mycobacterium tuberculosis
Sigma Factor SigM by Assessment of Virulence and Identification of SigM-Dependent Genes
Authors: Agarwal Nisheeth , Woolwine Samuel C. , Tyagi Sandeep , Bishai William R. 
Published: December 2006

ABSTRACT

Alternate sigma factors have been implicated in the survival of mycobacteria in response to specific stresses. To characterize the role of SigM in
Mycobacterium tuberculosis
, a
sigM
deletion mutant was generated by allelic exchange in the virulent CDC1551 strain. Comparing the wild-type and Δ
sigM
strains by complete genomic microarray, we observed a low level of baseline expression of
sigM
in wild-type
M. tuberculosis
and no significant differences in the gene expression patterns between these two strains. Alternatively, a SigM-overexpressing
M. tuberculosis
strain was constructed and microarray profiling revealed SigM-dependent expression of a relatively small group of genes, which included four
esat-6
homologues:
esxE
,
esxF
,
esxT
, and
esxU
. An assessment of SigM-dependent promoters from the microarray analysis revealed a putative consensus sequence for
M. tuberculosis
SigM of −35 GGAAC and −10 CGTCR. In vitro expression studies showed that
M. tuberculosis sigM
transcripts accumulate slightly in stationary phase and following heat shock. To understand the role of SigM in pathogenesis, the
M. tuberculosis sigM
deletion strain was compared with the isogenic wild-type strain and the complemented mutant strain for survival in murine macrophages and in the mouse model. The mutant was found to have similar abilities to survive in both the resting and activated J774A.1 macrophages. Mouse organ bacterial burdens indicated that the mutant proliferated and persisted at the same level as that of the wild-type and complemented strains in lung and spleen tissues. In time-to-death experiments in the mouse model, the Δ
sigM
mutant exhibited lethality times comparable to those observed for the wild-type and complemented strains. These data indicate that
M. tuberculosis
SigM governs the expression of a small set of genes, including four
esat-6
homologues, and that the loss of
sigM
does not confer a detectable virulence defect in the macrophages and mouse models of infection.
Capsule Enhances Pneumococcal Colonization by Limiting Mucus-Mediated Clearance
Authors: Nelson Aaron L. , Roche Aoife M. , Gould Jane M. , Chim Kannie , Ratner Adam J. , Weiser Jeffrey N. 
Published: December 2006

ABSTRACTExpression of a polysaccharide capsule is required for the full pathogenicity of many mucosal pathogens such asStreptococcus pneumoniae. Although capsule allows for evasion of opsonization and subsequent phagocytosis during invasive infection, its role during mucosal colonization, the organism's commensal state, remains unknown. Using a mouse model, we demonstrate that unencapsulated mutants remain capable of nasal colonization but at a reduced density and duration compared to those of their encapsulated parent strains. This deficit in colonization was not due to increased susceptibility to opsonophagocytic clearance involving complement, antibody, or the influx of Ly-6G-positive cells, including neutrophils seen during carriage. Rather, unencapsulated mutants remain agglutinated within lumenal mucus and, thus, are less likely to transit to the epithelial surface where stable colonization occurs. Studies of in vitro binding to immobilized human airway mucus confirmed the inhibitory effect of encapsulation. Likewise, pneumococcal variants expressing larger amounts of negatively charged capsule per cell were less likely to adhere to surfaces coated with human mucus and more likely to evade initial clearance in vivo. Removal of negatively charged sialic acid residues by pretreatment of mucus with neuraminidase diminished the antiadhesive effect of encapsulation. This suggests that the inhibitory effect of encapsulation on mucus binding may be mediated by electrostatic repulsion and offers an explanation for the predominance of anionic polysaccharides among the diverse array of unique capsule types. In conclusion, our findings demonstrate that capsule confers an advantage to mucosal pathogens distinct from its role in inhibition of opsonophagocytosis—escape from entrapment in lumenal mucus.
Evaluation of Radar Multiple-Scattering Effects from a GPM Perspective. Part I: Model Description and Validation
Authors: Battaglia A. , Ajewole M. O. , Simmer C. 
Published: January 2007

Abstract
A numerical model based on the Monte Carlo solution of the vector radiative transfer equation has been adopted to simulate radar signals. The model accounts for general radar configurations such as airborne/spaceborne/ground based and monostatic/bistatic and includes the polarization and the antenna pattern as particularly relevant features. Except for contributions from the backscattering enhancement, the model is particularly suitable for evaluating multiple-scattering effects. It has been validated against some analytical methods that provide solutions for the first and second order of scattering of the copolar intensity for pencil-beam/Gaussian antennas in the transmitting/receiving segment. The model has been applied to evaluate the multiple scattering when penetrating inside a uniform hydrometeor layer. In particular, the impact of the phase function, the range-dependent scattering optical thickness, and the effects of the antenna footprint are considered.