bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dendritic Cell-Derived Exosomes Express a
Streptococcus pneumoniae
Capsular Polysaccharide Type 14 Cross-Reactive Antigen That Induces Protective Immunoglobulin Responses against Pneumococcal Infection in Mice
Authors: Colino Jesus , Snapper Clifford M. 
Published: December 2006

ABSTRACT

Exosomes activate T cells in vivo, but whether exosomes are able to induce humoral immune responses is still unknown. We found that dendritic cells, but not other immune cells, constitutively release an exosome-associated glycoconjugate that is cross-reactive with the capsular polysaccharide of
Streptococcus pneumoniae
type 14 (Cps14-CRA). Cps14-CRA was localized to the cholesterol-enriched microdomains or rafts of the exosomes and was mapped to the β1→6 branched
N
-acetyl-lactosamine derivatives of the Cps14-CRA. Injection of CFA-primed naive mice with purified dendritic cell exosomes induced immunoglobulin (Ig) anti-Cps14 responses composed predominantly of IgM, IgG3, and IgG1. These responses were associated with protection against a lethal challenge with live
S. pneumoniae
type 14, but not with type 3 bacteria, and was correlated with the titer of elicited IgM and IgG3 anti-Cps14. These data show, for the first time, that exosomes can induce a humoral immune response to an associated unprocessed, autologous antigen. Although anti-Cps14 Ig responses are specifically demonstrated, these could reflect a broader mechanism that modulates both natural immunity and autoimmunity to other glycotopes.
AcpA Is aFrancisellaAcid Phosphatase That Affects Intramacrophage Survival and Virulence
Authors: Mohapatra Nrusingh P. , Balagopal Ashwin , Soni Shilpa , Schlesinger Larry S. , Gunn John S. 
Published: December 2006

ABSTRACTAcpA ofFrancisellaspp. is a respiratory-burst-inhibiting acid phosphatase that also exhibits phospholipase C activity. To better understand the molecular basis of AcpA in virulence, a deletion ofacpAwas constructed inFrancisella novicida. The phosphatase and lipase activities were reduced 10-fold and 8-fold, respectively, in theacpAmutant compared to the wild type and were found mostly associated with the outer membrane. TheacpAmutant was more susceptible to intracellular killing than the wild-type strain in the THP-1 human macrophage-like cell line. In addition, mice infected with theacpAmutant survived longer than the wild-type strain and were less fit than the wild-type strain in competition infection assays. Transmission electron microscopy showed that theacpAmutant was delayed in escape from macrophage phagosomes, as more than 75% ofacpAmutant bacteria could still be found inside phagosomes after 12 h of infection in THP-1 cells and human monocyte-derived macrophages, whereas most of the wild-type bacteria had escaped from the phagosome by 6 h postinfection. Thus, AcpA affects intracellular trafficking and the fate ofFrancisellawithin host macrophages.
Limited Role for CD4
+
T-Cell Help in the Initial Priming of
Trypanosoma cruzi-
Specific CD8
+
T Cells
Authors: Padilla Angel , Xu Dan , Martin Diana , Tarleton Rick 
Published: December 2006

ABSTRACT

Immune control of the protozoan parasite
Trypanosoma cruzi
requires the activation of both CD4
+
and CD8
+
T cells. We recently identified two
T. cruzi trans
-sialidase peptides that are targets of approximately 30% of all CD8
+
T cells during acute
T. cruzi
infection in mice. To determine whether CD4
+
T cells are required for generation of these dominant CD8
+
T-cell responses, major histocompatibility complex class II (MHC II)-deficient mice were infected with the Brazil strain of
T. cruzi
and examined for the generation of antigen-specific CD8
+
T cells. Strong
trans
-sialidase TSKB18- and TSKB20-specific CD8
+
T-cell responses were generated in both the presence and the absence of CD4
+
help. However, the magnitudes of the immunodominant TSKB20-specific CD8
+
T-cell responses detectable using class I MHC-peptide tetramers were consistently lower in the blood and spleens of MHC II-deficient mice. Spleen cells from infected MHC II-deficient mice produced gamma interferon after in vitro stimulation with
T. cruzi
peptides at levels similar to those in wild-type mice, and MHC II-deficient mice displayed strong
T. cruzi
peptide-specific cytotoxic T-lymphocyte activity in vivo. Thus, primary CD8
+
T-cell responses in experimental
T. cruzi
infection are generated in the absence of CD4
+
T cells, providing further evidence that
T. cruzi
directly activates and licenses antigen-presenting cells. Nevertheless, unhelped CD8
+
T cells in
T. cruzi-
infected mice fail to reach the frequencies achieved in the presence of CD4 T-cell help and are unable to prevent acute-phase death of these mice.
Intranasal Inoculation of Mice withYersinia pseudotuberculosisCauses a Lethal Lung Infection That Is Dependent onYersiniaOuter Proteins andPhoP
Authors: Fisher Michael L. , Castillo Cynthia , Mecsas Joan 
Published: December 2006

ABSTRACTYersinia pseudotuberculosisinfects many mammals and birds including humans, livestock, and wild rodents and can be recovered from the lungs of infected animals. To determine theY. pseudotuberculosisfactors important for growth during lung infection, we developed an intranasal model of infection in mice. Following intranasal inoculation, we monitored both bacterial growth in lungs and dissemination to systemic tissues. Intranasal inoculation with as few as 18 CFU ofY. pseudotuberculosiscaused a lethal lung infection in some mice. Over the course of 7 days, wild-typeY. pseudotuberculosisreplicated to nearly 1 × 108CFU/g of lung in BALB/c mice, induced histopathology in lungs consistent with pneumonia, but disseminated sporadically to other tissues. In contrast, a ΔyopBdeletion strain was attenuated in this model, indicating that translocation ofYersiniaouter proteins (Yops) is essential for virulence. Additionally, a ΔyopHnull mutant failed to grow to wild-type levels by 4 days postintranasal inoculation, but deletions of any other single effector YOP did not attenuate lung colonization 4 days postinfection. Strains with deletions inyopHand any one of the other known effectoryopgenes were more attenuated that the ΔyopHstrain, indicating a unique role foryopHin lungs. In summary, we have characterized the progression of a lung infection with an entericYersiniapathogen and shown that YopB and YopH are important in lung colonization and dissemination. Furthermore, this lung infection model withY. pseudotuberculosiscan be used to test potential therapeutics againstYersiniaand other gram-negative infections in lungs.
Role of Monocyte-Acquired Hemozoin in Suppression of Macrophage Migration Inhibitory Factor in Children with Severe Malarial Anemia
Authors: Awandare Gordon A. , Ouma Yamo , Ouma Collins , Were Tom , Otieno Richard , Keller Christopher C. , Davenport Gregory C. , Hittner James B. , Vulule John , Ferrell Robert , Ong'echa John M. , Perkins Douglas J. 
Published: December 2006

ABSTRACTSevere malarial anemia (SMA), caused byPlasmodium falciparuminfections, is one of the leading causes of childhood mortality in sub-Saharan Africa. Although the molecular determinants of SMA are largely undefined, dysregulation in host-derived inflammatory mediators influences disease severity. Macrophage migration inhibitory factor (MIF) is an important regulator of innate inflammatory responses that has recently been shown to suppress erythropoiesis and promote pathogenesis of SMA in murine models. To examine the role of MIF in the development of childhood SMA, peripheral blood MIF production was examined in Kenyan children (aged <3 years,n= 357) withP. falciparummalarial anemia. All children in the study were free from bacteremia and human immunodeficiency virus type 1. Since deposition of malarial pigment (hemozoin [Hz]) contributes to suppression of erythropoiesis, the relationship between MIF concentrations and monocytic acquisition of Hz was also examined in vivo and in vitro. Circulating MIF concentrations declined with increasing severity of anemia and significantly correlated with peripheral blood leukocyte MIF transcripts. However, MIF concentrations in peripheral blood were not significantly associated with reticulocyte production. Multivariate regression analyses, controlling for age, gender, and parasitemia, further revealed that elevated levels of pigment-containing monocytes (PCM) was associated with SMA and decreased MIF production. In addition, PCM levels were a better predictor of hemoglobin and MIF concentrations than parasite density. Additional experiments in malaria-naive individuals demonstrated that hemozoin caused both increased and decreased MIF production in cultured peripheral blood mononuclear cells (PBMC) in a donor-specific manner, independent of apoptosis. However, PBMC MIF production in children with acute malaria progressively declined with increasing anemia severity. Results presented here demonstrate that acquisition of hemozoin by monocytes is associated with suppression of peripheral blood MIF production and enhanced severity of anemia in childhood malaria.
TheMoraxella catarrhalisAutotransporter McaP Is a Conserved Surface Protein That Mediates Adherence to Human Epithelial Cells through Its N-Terminal Passenger Domain
Authors: Lipski Serena L. , Akimana Christine , Timpe Jennifer M. , Wooten R. Mark , Lafontaine Eric R. 
Published: December 2006

ABSTRACTThe protein McaP was previously shown to be an adhesin expressed by theMoraxella catarrhalisstrain O35E, which also displays esterase and phospholipase B activities (J. M. Timpe et al., Infect. Immun. 71:4341-4350, 2003). In the present study, sequence analysis suggests that McaP is a conventional autotransporter protein that contains a 12-stranded β-barrel transporter module (amino acids [aa] 383 to 650) linked to a surface-exposed passenger domain exhibiting lipolytic activity (aa 62 to 330). An in-frame deletion removing most of this predicted N-terminal passenger domain was engineered, andEscherichia coliexpressing the truncated McaP protein exhibited greatly reduced adherence to A549 human lung epithelial cells compared toE. coliexpressing wild-type McaP. Site-directed mutagenesis of a serine residue at position 62 of McaP, predicted to be important for the lipolytic activity of the protein, resulted in loss of hydrolysis ofp-nitrophenyl ester of caproate.E. coliexpressing this mutated McaP, however, adhered to A549 monolayers at levels greater than recombinant bacteria expressing the wild-type adhesin. These results indicate that the predicted passenger domain of McaP is involved in both the binding and the lipolytic activity of the molecule and demonstrate that the adhesive properties of McaP do not require its lipolytic activity. Sequence analysis ofmcaPfrom eightMoraxella catarrhalisstrains revealed that the gene product is highly conserved at the amino acid level (98 to 100% identity), and Western blot analysis demonstrated that a panel of 16 isolates all express McaP. Flow cytometry experiments using antibodies raised against various portions of McaP indicated that its predicted passenger domain as well as transporter module contain surface-exposed epitopes. In addition to binding to the surface of intact bacteria, these antibodies were found to decrease adherence ofM. catarrhalisto A549 human lung cells by up to 47% and to reduce binding of recombinantE. coliexpressing McaP by 98%. These results suggest that McaP should be considered as a potential vaccine antigen.
Protein P200 Is Dispensable for
Mycoplasma pneumoniae
Hemadsorption but Not Gliding Motility or Colonization of Differentiated Bronchial Epithelium
Authors: Jordan Jarrat L. , Chang How-Yi , Balish Mitchell F. , Holt Lynley S. , Bose Stephanie R. , Hasselbring Benjamin M. , Waldo Robert H. , Krunkosky Thomas M. , Krause Duncan C. 
Published: December 2006

ABSTRACT

Mycoplasma pneumoniae
protein P200 was localized to the terminal organelle, which functions in cytadherence and gliding motility. The loss of P200 had no impact on binding to erythrocytes and A549 cells but resulted in impaired gliding motility and colonization of differentiated bronchial epithelium. Thus, gliding may be necessary to overcome mucociliary clearance.
Long-Term Staphylococcal Enterotoxin C1 Exposure Induces Soluble Factor-Mediated Immunosuppression by Bovine CD4+and CD8+T Cells
Authors: Seo Keun Seok , Lee Sang Un , Park Yong Ho , Davis William C. , Fox Lawrence K. , Bohach Gregory A. 
Published: December 2006

ABSTRACTRegulatory T cells (Tregs) help control the development and maintenance of protective immunity and can lead to aberrant immune responses to some pathogens. Several lines of evidence suggest that Tregsare induced by exposure to superantigens (SAgs) in vitro or in vivo. In this study, bovine peripheral blood mononuclear cells (PBMC) were exposed in vitro to a relatively low dose (5 ng/ml) of staphylococcal enterotoxin C1 (SEC1) for up to 10 days. Upon stimulation, CD4+and CD8+T cells initially proliferated at similar rates. Subsequently, from days 6 through 10, most CD4+and CD8+T cells proliferated regardless of Vβ specificity, but the proliferation of CD8+T cells occurred more vigorously. The transcription of CD25 and CD152 genes increased, whereas that of interleukin-2 (IL-2) decreased. γδ T cells appeared to be unresponsive. An increase in the transcription of IL-10 and transforming growth factor β (TGF-β) genes in SEC1-stimulated cultures was attributed to the CD4+CD25+T-cell subpopulation. The expression of Foxp3 mRNA also increased and was accompanied by the upregulation of CD152 and the downregulation of IL-2 transcription, suggesting that cells in this subpopulation are Tregs. Functionally, SEC1-stimulated CD4+T cells suppressed the proliferation of naive PBMC in response to heat-killed-fixedStaphylococcus aureus. The suppression was partially mediated by IL-10 and TGF-β, another characteristic of certain types of Tregs.The CD8+T-cell population also suppressed naive PBMC through another mechanism not mediated by IL-10 or TGF-β. These results provide further insight into the potential mechanisms by which SAgs could contribute to evasion of the immune response, affecting the outcome of infection or colonization.
p38 Mitogen-Activated Protein Kinase Controls NF-κB Transcriptional Activation and Tumor Necrosis Factor Alpha Production through RelA Phosphorylation Mediated by Mitogen- and Stress-Activated Protein Kinase 1 in Response toBorrelia burgdorferiAntigens
Authors: Olson Chris M. , Hedrick Michael N. , Izadi Hooman , Bates Tonya C. , Olivera Elias R. , Anguita Juan 
Published: December 2006

ABSTRACTThe interaction ofBorrelia burgdorferi, the causative agent of Lyme borreliosis, with phagocytic cells induces the activation of NF-κB and the expression of proinflammatory cytokines including tumor necrosis factor alpha (TNF-α).B. burgdorferi-induced TNF-α production is also dependent on the activation of p38 mitogen-activated protein (MAP) kinase. The specific contribution of these signaling pathways to the response of phagocytic cells to the spirochete and the molecular mechanisms underlying this response remain unresolved. We now show that p38 MAP kinase activity regulates the transcriptional activation of NF-κB in response to spirochetal lysate stimulation of phagocytic cells. The regulation occurs at the nuclear level and is independent of the translocation of the transcription factor to the nucleus or its capacity to bind to specific DNA target sequences. In RAW264.7 cells, p38α MAP kinase regulates the phosphorylation of NF-κB RelA. p38 MAP kinase phosphorylates the nuclear kinase mitogen- and stress-activated protein kinase 1 (MSK1). MSK1 in turn phosphorylates the transcriptionally active subunit of NF-κB, RelA. The repression of MSK1 expression with small interfering RNA results in reduced RelA phosphorylation and a significant decrease in the production of TNF-α in response toB. burgdorferilysates. Overall, these results clarify the contribution of the signaling pathways that are activated in response to the interaction of spirochetes with phagocytic cells to TNF-α production. Our results situate p38 MAP kinase activity as a central regulator of the phagocytic proinflammatory response through MSK1-mediated transcriptional activation of the transcription factor NF-κB.
Role of the
wbt
Locus of
Francisella tularensis
in Lipopolysaccharide O-Antigen Biogenesis and Pathogenicity
Authors: Raynaud Catherine , Meibom Karin L. , Lety Marie-Annick , Dubail Iharilalao , Candela Thomas , Frapy Eric , Charbit Alain 
Published: December 2006

ABSTRACT

Francisella tularensis
is a highly infectious bacterial pathogen, responsible for the zoonotic disease tularemia. We screened a bank of transposon insertion mutants of
F. tularensis
subsp.
holarctica
LVS for colony morphology alterations and selected a mutant with a transposon insertion in
wbtA
, the first gene of the predicted lipopolysaccharide O-antigen gene cluster. Inactivation of
wbtA
led to the complete loss of O antigen, conferred serum sensitivity, impaired intracellular replication, and severely attenuated virulence in the mouse model. Notably, this mutant afforded protection against a challenge against virulent LVS.
The
blp
Bacteriocins of
Streptococcus pneumoniae
Mediate Intraspecies Competition both In Vitro and In Vivo
Authors: Dawid Suzanne , Roche Aoife M. , Weiser Jeffrey N. 
Published: December 2006

ABSTRACT

The introduction of the conjugate seven-valent pneumococcal vaccine has led to the replacement of vaccine serotypes with nonvaccine serotypes of
Streptococcus pneumoniae
. This observation implies that intraspecies competition between pneumococci occurs during nasopharyngeal colonization, allowing one strain or set of strains to predominate over others. We investigated the contribution of the
blp
locus, encoding putative bacteriocins and cognate immunity peptides, to intraspecies competition. We sequenced the relevant regions of the
blp
locus of a type 6A strain able to inhibit the growth of the type 4 strain, TIGR4, in vitro. Using deletional analysis, we confirmed that inhibitory activity is regulated by the function of the response regulator, BlpR, and requires the two putative bacteriocin genes
blpM
and
blpN
. Comparison of the TIGR4 BlpM and -N amino acid sequences demonstrated that only five amino acid differences were sufficient to target the heterologous strain. Analysis of a number of clinical isolates suggested that the BlpMN bacteriocins divide into two families. A mutant in the
blpMN
operon created in the clinically relevant type 19A background was deficient in both bacteriocin activity and immunity. This strain was unable to compete with both its parent strain and a serotype 4 isolate during cocolonization in the mouse nasopharynx, suggesting that the locus is functional in vivo and confirming its role in promoting intraspecies competition.
Block-Structured Adaptive Grids on the Sphere: Advection Experiments
Authors: Jablonowski Christiane , Herzog Michael , Penner Joyce E. , Oehmke Robert C. , Stout Quentin F. , van Leer Bram , Powell Kenneth G. 
Published: December 2006

Abstract
A spherical 2D adaptive mesh refinement (AMR) technique is applied to the so-called Lin–Rood advection algorithm, which is built upon a conservative and oscillation-free finite-volume discretization in flux form. The AMR design is based on two modules: a block-structured data layout and a spherical AMR grid library for parallel computer architectures. The latter defines and manages the adaptive blocks in spherical geometry, provides user interfaces for interpolation routines, and supports the communication and load-balancing aspects for parallel applications. The adaptive grid simulations are guided by user-defined adaptation criteria. Both statically and dynamically adaptive setups that start from a regular block-structured latitude–longitude grid are supported. All blocks are logically rectangular, self-similar, and independent data units that are split into four in the event of refinement requests, thereby doubling the horizontal resolution. Grid coarsenings reverse this refinement principle. Refinement and coarsening levels are constrained so that there is a uniform 2:1 mesh ratio at all fine–coarse-grid interfaces. The adaptive advection model is tested using three standard advection tests with increasing complexity. These include the transport of a cosine bell around the sphere, the advection of a slotted cylinder, and a smooth deformational flow that describes the roll-up of two vortices. The latter two examples exhibit very sharp edges and gradients that challenge not only the numerical scheme but also the AMR approach. The adaptive simulations show that all features of interest are reliably detected and tracked with high-resolution grids. These are steered by either a threshold- or gradient-based adaptation criterion that depends on the characteristics of the advected tracer field. The additional resolution clearly helps preserve the shape and amplitude of the transported tracer while saving computing resources in comparison to uniform-grid model runs.
Frequency Modes of Monsoon Precipitation in Arizona and New Mexico
Authors: Nolin Anne W. , Hall-McKim Eileen A. 
Published: December 2006

Abstract
The interannual and intraseasonal variability of the North American monsoon is of great interest because a large proportion of the annual precipitation for Arizona and New Mexico arrives during the summer monsoon. Forty-one years of daily monsoon season precipitation data for Arizona and New Mexico were studied using wavelet analysis. This time-localized spectral analysis method reveals that periodicities of less than 8 days are positively correlated with mean daily precipitation during the 1 July–15 September monsoon period. Roughly 17% of the years indicate no significant periodicity during the monsoon period for either region and are associated with low monsoon precipitation. High- and low-frequency modes explain an equivalent percentage of the variance in monsoon precipitation in both Arizona and New Mexico, and in many years concurrent multiple periodicities occur. Wavelet analysis was effective in identifying the contribution of high-frequency modes that had not been discerned in previous studies. These results suggest that precipitation processes during the monsoon season are modulated by phenomena operating at synoptic (2–8 days) and longer (&gt;8 days) time scales and point to the need for further studies to better understand the associated atmospheric processes.