bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell membrane surface expression and tyrosine kinase regulate the osmolyte channel (skAE1) in skate erythrocytes
Authors: Perlman D. F. , Musch M. W. , Goldstein L. 
Published: May 2006

AbstractA regulatory volume decrease response occurs when skate (Raja erinacea) erythrocytes are exposed to hyposmotic medium; they swell and then reduce their volume by releasing organic osmolytes (primarily taurine) and associated water. The response involves the red blood cell anion‐exchanger skate anion‐exchanger 1 (skAE1), which has been previously shown to be affected by tyrosine phosphorylation, to form tetramers and to change binding affinities to the cytoskeletal proteins, ankyrin and band 4.1. Our recent studies are focused on determining the sequence and mechanism of these events to better understand the activation of skAE1 upon hyposmotic stimulation. Under isosmotic conditions a large portion of skAE1 is found not only on the plasma membranes but also associated intracellularly in detergent‐resistant membranes or lipid rafts. We hypothesize that an important step in the hyposmotic‐induced increase in taurine transport involves the movement of skAE1 from an intracellular association with lipid rafts into the cell membrane. Inhibition of tyrosine phosphorylation of skAE1 with piceatannol reduces the hyposmotic‐induced increase in taurine transport and also inhibits both the decreased binding of skAE1 to band 4.1 and the increased affinity to ankyrin. However, the phosphorylation inhibitor does not block the movement of the transporter into the plasma membrane or the formation of tetramers. This suggests that tyrosine phosphorylation is important in the hyposmotic‐induced taurine transport but other steps that do not require phosphorylation play an important role.
Involvement of Gonadal Steroids and Gamma Interferon in Sex Differences in Response to Blood-Stage Malaria Infection
Authors: Cernetich Amy , Garver Lindsey S. , Jedlicka Anne E. , Klein Pamela W. , Kumar Nirbhay , Scott Alan L. , Klein Sabra L. 
Published: May 2006

ABSTRACT

To examine the hormonal and immunological mechanisms that mediate sex differences in susceptibility to malaria infection, intact and gonadectomized (gdx) C57BL/6 mice were inoculated with
Plasmodium chabaudi
AS-infected erythrocytes, and the responses to infection were monitored. In addition to reduced mortality, intact females recovered from infection-induced weigh loss and anemia faster than intact males. Expression microarrays and real-time reverse transcription-PCR revealed that gonadally intact females exhibited higher expression of interleukin-10 (IL-10), IL-15Rα, IL-12Rβ, Gadd45γ, gamma interferon (IFN-γ), CCL3, CXCL10, CCR5, and several IFN-inducible genes in white blood cells and produced more IFN-γ than did intact males and gdx females, with these differences being most pronounced during peak parasitemia. Intact females also had higher anti-
P. chabaudi
immunoglobulin G (IgG) and IgG1 responses than either intact males or gdx females. To further examine the effector mechanisms mediating sex differences in response to
P. chabaudi
infection, responses to infection were compared among male and female wild-type (WT), T-cell-deficient (TCRβδ
−/−
), B-cell-deficient (μMT), combined T- and B-cell-deficient (RAG1), and IFN-γ knockout (IFN-γ
−/−
) mice. Males were 3.5 times more likely to die from malaria infection than females, with these differences being most pronounced among TCRβδ
−/−
, μMT, and RAG1 mice. Male mice also exhibited more severe weight loss, anemia, and hypothermia, and higher peak parasitemia than females during infection, with WT, RAG1, TCRβδ
−/−
, and μMT mice exhibiting the most pronounced sexual dimorphism. The absence of IFN-γ reduced the sex difference in mortality and was more detrimental to females than males. These data suggest that differential transcription and translation of IFN-γ, that is influenced by estrogens, may mediate sex differences in response to malaria.
Infection of Human Fallopian Tube Epithelial Cells withNeisseria gonorrhoeaeProtects Cells from Tumor Necrosis Factor Alpha-Induced Apoptosis
Authors: Morales Priscilla , Reyes Paz , Vargas Macarena , Rios Miguel , Imarai Mónica , Cardenas Hugo , Croxatto Horacio , Orihuela Pedro , Vargas Renato , Fuhrer Juan , Heckels John E. , Christodoulides Myron , Velasquez Luis 
Published: May 2006

ABSTRACTFollowing infection withNeisseria gonorrhoeae, bacteria may ascend into the Fallopian tubes (FT) and induce salpingitis, a major cause of infertility. In the FT, interactions between mucosal epithelial cells and gonococci are pivotal events in the pathogen's infection cycle and the inflammatory response. In the current study, primary FT epithelial cells were infected in vitro with different multiplicities of infection (MOI) of Pil+Opa+gonococci. Bacteria showed a dose-dependent association with cells and induced the secretion of tumor necrosis factor alpha (TNF-α). A significant finding was that gonococcal infection (MOI = 1) induced apoptosis in approximately 30% of cells, whereas increasing numbers of bacteria (MOI = 10 to 100) did not induce apoptosis. Apoptosis was observed in only 11% of cells with associated bacteria, whereas >84% of cells with no adherent bacteria were apoptotic. TNF-α was a key contributor to apoptosis, since (i) culture supernatants from cells infected with gonococci (MOI = 1) induced apoptosis in naïve cultures, suggesting that a soluble factor was responsible; (ii) gonococcal infection-induced apoptosis was inhibited with anti-TNF-α antibodies; and (iii) the addition of exogenous TNF-α induced apoptosis, which was inhibited by the presence of increasing numbers of bacteria (MOI = 10 to 100). These data suggest that TNF-α-mediated apoptosis of FT epithelial cells is likely a primary host defense mechanism to prevent pathogen colonization. However, epithelial cell-associated gonococci have evolved a mechanism to protect the cells from undergoing TNF-α-mediated apoptosis, and this modulation of the host innate response may contribute to establishment of infection. Understanding the antiapoptotic mechanisms used byNeisseria gonorrhoeaewill inform the pathogenesis of salpingitis and could suggest new intervention strategies for prevention and treatment of the disease.
The
Babesia bovis
Merozoite Surface Antigen 1 Hypervariable Region Induces Surface-Reactive Antibodies That Block Merozoite Invasion
Authors: LeRoith Tanya , Berens Shawn J. , Brayton Kelly A. , Hines Stephen A. , Brown Wendy C. , Norimine Junzo , McElwain Terry F. 
Published: May 2006

ABSTRACT

A hypervariable region (HVR) previously identified in the carboxy-terminal one-third of the
Babesia bovis
variable merozoite surface antigen family was more extensively analyzed in merozoite surface antigen 1 (MSA-1) from 16 strains and isolates. The MSA-1 HVR is proline rich and contains three semiconserved motifs nearly identical to those described for the related family member MSA-2. Two MSA-1-specific monoclonal antibodies previously shown to be reactive with the merozoite surface bound to a recombinant construct encoding the HVR, indicating that the HVR is surface exposed and accessible to antibody binding. Importantly, these surface-reactive, HVR-specific monoclonal antibodies were capable of inhibiting merozoite infectivity of the host erythrocyte in vivo. The results indicate that the MSA-1 HVR is involved in erythrocyte invasion and suggest that selection of MSA-1 variants may be driven by invasion-blocking antibodies.
Role for Erbin in Bacterial Activation of Nod2
Authors: Kufer T. A. , Kremmer E. , Banks D. J. , Philpott D. J. 
Published: May 2006

ABSTRACT

Intracellular peptidoglycan (PG) recognition in human cells is mediated by the NACHT-LRR proteins Nod1 and Nod2. Elicitation of these proteins by PG motifs released from invasive bacteria triggers signaling events, resulting in the activation of the NF-κB pathway. In order to decipher the molecular components involved in Nod2 signal transduction, we set out to identify new interaction partners of Nod2 by using a yeast two-hybrid screen. Besides the known interaction partner RIP2, the screen identified the leucine-rich repeat (LRR)- and PDZ domain-containing family member Erbin as a binding partner of Nod2. Erbin showed a specific interaction with Nod2 in coimmunoprecipitation experiments with human HEK 293T cells. Immunofluorescence microscopy with a newly generated anti-Nod2 monoclonal antibody showed that Erbin and Nod2 partially colocalize in human cells. Subsequent analysis of the Erbin/Nod2 interaction revealed that the LRR of Erbin and the caspase activating and recruiting domains of Nod2 were necessary for this interaction. No significant interaction was observed with a Walker B box mutant of Nod2 or a Crohn's disease-associated frameshift mutant of Nod2, indicating that complex formation is dependent on the activity of the molecule. In addition, a change in the dynamics of the Erbin/Nod2 complex was observed during
Shigella flexneri
infection. Furthermore, ectopic expression of increasing amounts of Erbin or short hairpin RNA-mediated knockdown of Erbin showed a negative influence of Erbin on Nod2/muramyl-dipeptide-mediated NF-κB activation. These results implicate Erbin as a potential negative regulator of Nod2 and show that bacterial infection has an impact on Nod2/Erbin complex formation within cells.
Genomic Diversity between Strains of the Same Serotype and Multilocus Sequence Type among Pneumococcal Clinical Isolates
Authors: Silva Nuno A. , McCluskey Jackie , Jefferies Johanna M. C. , Hinds Jason , Smith Andrew , Clarke Stuart C. , Mitchell Tim J. , Paterson Gavin K. 
Published: May 2006

ABSTRACT

The important human pathogen
Streptococcus pneumoniae
is known to be a genetically diverse species. We have used comparative genome hybridization (CGH) microarray analysis to investigate this diversity in a collection of clinical isolates including several capsule serotype 14 pneumococci, a dominant serotype among disease isolates. We have identified three new regions of diversity among pneumococcal isolates and, importantly, clearly demonstrate genetic differences between strains of the same multilocus sequence type (ST) and capsule serotype. CGH may therefore, under certain circumstances, prove to be a valuable tool to supplement current typing methods. Finally, we show that these clonal strains with the same serotype and ST behave differently in an animal model. Strains of the same ST and serotype therefore have important genetic and phenotypic differences.
Resistance of
Streptococcus gordonii
to Polymorphonuclear Leukocyte Killing Is a Potential Virulence Determinant of Infective Endocarditis
Authors: Young Lee Si , Cisar John O. , Bryant Joseph L. , Eckhaus Michael A. , Sandberg Ann L. 
Published: May 2006

ABSTRACT

Significant differences in virulence among seven representative
Streptococcus gordonii
strains were observed by using the rat model of infective endocarditis. Five strains, including
S. gordonii
DL1, caused severe disease, while the other two strains, including
S. gordonii
SK12, caused minimal or no disease. The differences in virulence were evident from the visible presence of streptococci in the vegetations present on the aortic valves of catheterized rats that were challenged with individual strains and also from the much greater recovery of rifampin-resistant
S. gordonii
DLl than of streptomycin-resistant
S. gordonii
SK12 from the hearts of animals coinfected with both organisms. Each
S. gordonii
strain aggregated with human platelets and bound to polymorphonuclear leukocytes (PMNs), as shown by the stimulation of PMN superoxide anion production. These interactions were reduced or abolished by pretreatment of the platelets or PMNs with sialidase, indicating that there was bacterial recognition of host sialic acid-containing receptors. Adhesin-mediated binding of each
S. gordonii
strain to PMNs also triggered phagocytosis. However, the subsequent PMN-dependent killing differed significantly for the seven strains. The five virulent strains included three strains that were not killed and two strains whose numbers were reduced by approximately 50%. In contrast, the level of killing of each avirulent strain under the same conditions was significantly greater and approached 90% of the bacteria added. Parallel studies performed with rat PMNs revealed comparable differences in the resistance or susceptibility of representative virulent and avirulent strains. Thus, the ability of
S. gordonii
to survive in PMNs following adhesin-mediated phagocytosis may be an important virulence determinant of infective endocarditis.
Interaction ofYersinia pestiswith Macrophages: Limitations in YopJ-Dependent Apoptosis
Authors: Zauberman Ayelet , Cohen Sara , Mamroud Emanuelle , Flashner Yehuda , Tidhar Avital , Ber Raphael , Elhanany Eytan , Shafferman Avigdor , Velan Baruch 
Published: May 2006

ABSTRACTThe enteropathogenicYersiniastrains are known to downregulate signaling pathways in macrophages by effectors of the type III secretion system, in which YopJ/YopP plays a crucial role. The adverse effects ofYersinia pestis, the causative agent of plague, were examined by infecting J774A.1 cells, RAW264.7 cells, and primary murine macrophages with the EV76 strain and with the fully virulent Kimberley53 strain.Y. pestisexerts YopJ-dependent suppression of tumor necrosis factor alpha secretion and phosphorylation of mitogen-activated protein kinases and thus resembles enteropathogenicYersinia. However,Y. pestisis less able to activate caspases, to suppress NF-κB activation, and to induce apoptosis in macrophages than the high-virulenceY. enterocoliticaWA O:8 strain. These differences appear to be related to lower efficiency of YopJ effector translocation byY. pestis. The efficiencies of effector translocation and of apoptosis induction can be enhanced either by using a high bacterial load in a synchronized infection or by overexpressing exogenous YopJ inY. pestis. Replacing YopJ with the homologousY. enterocoliticaeffector YopP can further enhance these effects. Overexpression of YopP in ayopJ-deletedY. pestisbackground leads to rapid and effective translocation into target cells, providingY. pestiswith the high cytotoxic potential ofY. enterocoliticaWA O:8. We suggest that the relative inferiority ofY. pestisin triggering cell death in macrophages may be advantageous for its in vivo propagation in the early stages of infection.
Iha from an
Escherichia coli
Urinary Tract Infection Outbreak Clonal Group A Strain Is Expressed In Vivo in the Mouse Urinary Tract and Functions as a Catecholate Siderophore Receptor
Authors: Léveillé Simon , Caza Mélissa , Johnson James R. , Clabots Connie , Sabri Mourad , Dozois Charles M. 
Published: May 2006

ABSTRACT

Virulence factors of pathogenic
Escherichia coli
belonging to a recently emerged and disseminated clonal group associated with urinary tract infection (UTI), provisionally designated clonal group A (CGA), have not been experimentally investigated. We used a mouse model of ascending UTI with CGA member strain UCB34 in order to identify genes of CGA that contribute to UTI.
iha
was identified to be expressed by strain UCB34 in the mouse kidney using selective capture of transcribed sequences.
iha
from strain UCB34 demonstrated a siderophore receptor phenotype when cloned in a catecholate siderophore receptor-negative
E. coli
K-12 strain, as shown by growth promotion experiments and uptake of
55
Fe complexed to enterobactin or its linear 2, 3-dihydroxybenzoylserine (DHBS) siderophore derivatives. Siderophore-mediated growth promotion by Iha was TonB dependent. Growth and iron uptake were more marked with linear DHBS derivatives than with purified enterobactin. The reported phenotype of adherence to epithelial cells conferred by expressing
iha
from a multicopy cloning vector in a poorly adherent
E. coli
K-12 host strain was confirmed to be specific to
iha
, in comparison with other siderophore receptor genes.
iha
expression was regulated by the ferric uptake regulator Fur and by iron availability, as shown by real-time reverse transcriptase PCR. In a competitive infection experiment using the mouse UTI model, wild-type strain UCB34 significantly outcompeted an isogenic
iha
null mutant. Iha thus represents a Fur-regulated catecholate siderophore receptor that, uniquely, exhibits an adherence-enhancing phenotype and is the first described urovirulence factor identified in a CGA strain.
Constitutive Differences in Gene Expression Profiles Parallel Genetic Patterns of Susceptibility to Tuberculosis in Mice
Authors: Orlova Marianna O. , Majorov Konstantin B. , Lyadova Irina V. , Eruslanov Eugenii B. , M'lan Cyr E. , Greenwood Celia M. T. , Schurr Erwin , Apt Alexander S. 
Published: May 2006

ABSTRACTInterstitial lung macrophages from tuberculosis-susceptible I/St and tuberculosis-resistant A/Sn mice demonstrated significant constitutive differences in gene expression levels, whereas in vitro infection of these cells withMycobacterium tuberculosishad only a modulatory impact on gene expression. We conclude that intrinsic gene expression profiles are an important determinant of tuberculosis pathogenesis in mice.
Environmental Signals Generate a Differential and Coordinated Expression of the Heme Receptor Gene Family of
Bartonella quintana
Authors: Battisti James M. , Sappington Kate N. , Smitherman Laura S. , Parrow Nermi L. , Minnick Michael F. 
Published: May 2006

ABSTRACT

Of all bacteria,
Bartonella quintana
has the highest reported in vitro hemin requirement, yet an explanation for this remains elusive. To produce diseases such as trench fever, endocarditis, and bacillary angiomatosis,
B. quintana
must survive and replicate in the disparate environments of the
Pediculus humanus corporis
(body louse) gut and the human vasculature. We previously identified a five-member family of hemin binding proteins (Hbps) synthesized by
B. quintana
that bind hemin on the outer surface but share no similarity to known bacterial heme receptors. In the present study, we examine the transcription, regulation, and synthesis of this virulence factor family by cultivation of the bacterium in environments that simulate natural heme, oxygen, and temperature conditions encountered in the host and insect vector. First, quantitative real-time PCR data show that
hbpC
expression is regulated by temperature, where a >100-fold increase in transcript quantity was seen at 30°C relative to 37°C, suggesting that HbpC synthesis would be greatest in the cooler temperature of the louse. Second, cultivation at human bloodstream oxygen concentration (5% relative to 21% atmospheric) significantly decreases the transcript quantity of all
hbp
genes, indicating that expression is influenced by O
2
and/or reactive oxygen species. Third, a differential expression pattern within the
hbp
family is revealed when
B. quintana
is grown in a range of hemin concentrations: subgroup I (
hbpC
and
hbpB
) predominates in a simulated louse environment (high heme), and subgroup II (
hbpA
,
hbpD
, and
hbpE
) is preferentially expressed in a simulated human background (low heme). By using two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblotting, and matrix-assisted laser desorption ionization—time of flight mass spectrometry fingerprinting, we demonstrate that synthesis of HbpA correlates with
hbpA
transcript increases observed at low hemin concentrations. Finally, an
hbpA
promoter-
lacZ
reporter construct in
B. quintana
demonstrates that a transcriptional regulator(s) is controlling the expression of
hbpA
through a
cis
-acting regulatory element located in the
hbpA
promoter region.
Characterization of a Novel High-Affinity Monoclonal Immunoglobulin G Antibody against the Ricin B Subunit
Authors: McGuinness Carolyn R. , Mantis Nicholas J. 
Published: May 2006

ABSTRACTThere is an urgent need for the development of a passive immunotherapy against the category B select agent ricin, a lethal ribosome-inactivating toxin composed of an enzymatic A subunit (RTA) and a single binding B subunit (RTB). To date, only one monoclonal antibody (MAb), a mouse immunoglobulin G (IgG1) against RTA called R70, has been deemed sufficiently potent in animal models to warrant further testing in humans. In this study, we have identified and characterized MAb 24B11, a murine IgG1 directed against RTB. In a Vero cell cytotoxicity assay, 24B11 was approximately two times more effective at neutralizing ricin than was R70. The equilibrium dissociation constants of 24B11 (KD= 4.2 × 10−9M) and R70 (KD= 3.2 × 10−9M) were virtually identical, suggesting that the difference in neutralization activity between the two MAbs was not due to differing affinities for the toxin. 24B11 blocked ricin attachment to galactoside receptors on primary mouse splenocytes and on the apical surfaces of human mucosal epithelial cell monolayers. Surprisingly, R70 also effectively interfered with ricin attachment to receptors on cell surfaces. Using a phage-displayed peptide library, we determined that 24B11 binds an epitope on RTB adjacent to, but not within, one of the two galactose binding domains. Finally, we demonstrate that R70 and 24B11, when combined, function synergistically to neutralize ricin in vitro, raising the possibility that these two MAbs could serve as a novel immunotherapeutic in vivo.
Human Recombinant Antibodies againstPlasmodium falciparumMerozoite Surface Protein 3 Cloned from Peripheral Blood Leukocytes of Individuals with Immunity to Malaria Demonstrate Antiparasitic Properties
Authors: Lundquist Rasmus , Nielsen Leif Kofoed , Jafarshad Ali , SoeSoe Daw , Christensen Lars Harder , Druilhe Pierre , Dziegiel Morten Hanefeld 
Published: May 2006

ABSTRACTImmunoglobulins from individuals with immunity to malaria have a strong antiparasitic effect when transferred toPlasmodium falciparummalaria infected patients. One prominent target of antiparasitic antibodies is the merozoite surface antigen 3 (MSP-3). We have investigated the antibody response against MSP-3 residues 194 to 257 (MSP-3194-257) on the molecular level. mRNA from peripheral blood leukocytes from clinically immune individuals was used as a source of Fab (fragment antibody) genes. A Fab-phage display library was made, and three distinct antibodies designated RAM1, RAM2, and RAM3 were isolated by panning. Immunoglobulin G1 (IgG1) and IgG3 full-length antibodies have been produced in CHO cells. Reactivity with the native parasite protein was demonstrated by immunofluorescence microscopy, flow cytometry, and immunoblotting. Furthermore, the antiparasitic effect of RAM1 has been tested in vitro in an antibody-dependent cellular inhibition (ADCI) assay. Both the IgG1 and the IgG3 versions of the antibody show an inhibitory effect on parasite growth.