bluuebunny/crossref_metadata_2025_split huggingface dataset:
TRAF6-Dependent Mitogen-Activated Protein Kinase Activation Differentially Regulates the Production of Interleukin-12 by Macrophages in Response toToxoplasma gondii
Authors: Mason Nicola J. , Fiore Jim , Kobayashi Takashi , Masek Katherine S. , Choi Yongwon , Hunter Christopher A. 
Published: September 2004

ABSTRACTThe production of interleukin-12 (IL-12) is critical to the development of innate and adaptive immune responses required for the control of intracellular pathogens. Many microbial products signal through Toll-like receptors (TLR) and activate NF-κB family members that are required for the production of IL-12. Recent studies suggest that components of the TLR pathway are required for the production of IL-12 in response to the parasiteToxoplasma gondii; however, the production of IL-12 in response to this parasite is independent of NF-κB activation. The adaptor molecule TRAF6 is involved in TLR signaling pathways and associates with serine/threonine kinases involved in the activation of both NF-κB and mitogen-activated protein kinase (MAPK). To elucidate the intracellular signaling pathways involved in the production of IL-12 in response to soluble toxoplasma antigen (STAg), wild-type and TRAF6−/−mice were inoculated with STAg, and the production of IL-12(p40) was determined. TRAF6−/−mice failed to produce IL-12(p40) in response to STAg, and TRAF6−/−macrophages stimulated with STAg also failed to produce IL-12(p40). Studies using Western blot analysis of wild-type and TRAF6−/−macrophages revealed that stimulation with STAg resulted in the rapid TRAF6-dependent phosphorylation of p38 and extracellular signal-related kinase, which differentially regulated the production of IL-12(p40). The studies presented here demonstrate for the first time that the production of IL-12(p40) in response to toxoplasma is dependent upon TRAF6 and p38 MAPK.
Wolbachia-Induced Neutrophil Activation in a Mouse Model of Ocular Onchocerciasis (River Blindness)
Authors: Gillette-Ferguson Illona , Hise Amy G. , McGarry Helen F. , Turner Joseph , Esposito Andrew , Sun Yan , Diaconu Eugenia , Taylor Mark J. , Pearlman Eric 
Published: September 2004

ABSTRACTEndosymbioticWolbachiabacteria are abundant in the filarial nematodes that cause onchocerciasis (river blindness), including the larvae (microfilariae) that migrate into the cornea. Using a mouse model of ocular onchocerciasis, we recently demonstrated that it is these endosymbiotic bacteria rather than the nematodes per se that induce neutrophil infiltration to the corneal stroma and loss of corneal clarity (Saint Andre et al., Science295:1892-1895, 2002). To better understand the role ofWolbachiaorganisms in the pathogenesis of this disease, we examined the fate of these bacteria in the cornea by immunoelectron microscopy. Microfilariae harboringWolbachiaorganisms were injected into mouse corneas, and bacteria were detected with antibody toWolbachiasurface protein. Within 18 h of injection, neutrophils completely surrounded the nematodes and were in close proximity toWolbachiaorganisms.Wolbachiasurface protein labeling was also prominent in neutrophil phagosomes, indicating neutrophil ingestion ofWolbachiaorganisms. Furthermore, the presence of numerous electron-dense granules around the phagosomes indicated that neutrophils were activated. To determine ifWolbachiaorganisms directly activate neutrophils, peritoneal neutrophils were incubated with either parasite extracts containingWolbachiaorganisms, parasite extracts depleted ofWolbachiaorganisms (by antibiotic treatment of worms), orWolbachiaorganisms isolated from filarial nematodes. After 18 h of incubation, we found that isolatedWolbachiaorganisms stimulated production of tumor necrosis factor alpha and CXC chemokines macrophage inflammatory protein 2 and KC by neutrophils in a dose-dependent manner. Similarly, these cytokines were induced by filarial extracts containingWolbachiaorganisms but not byWolbachia-depleted extracts. Taken together, these findings indicate that neutrophil activation is an important mechanism by whichWolbachiaorganisms contribute to the pathogenesis of ocular onchocerciasis.
Release of Periplasmic Proteins of
Brucella suis
upon Acidic Shock Involves the Outer Membrane Protein Omp25
Authors: Boigegrain Rose-Anne , Salhi Imed , Alvarez-Martinez Maria-Teresa , Machold Jan , Fedon Yann , Arpagaus Martine , Weise Christoph , Rittig Michael , Rouot Bruno 
Published: September 2004

ABSTRACT

The survival and replication of
Brucella
in macrophages is initially triggered by a low intraphagosomal pH. In order to identify proteins released by
Brucella
during this early acidification step, we analyzed
Brucella suis
conditioned medium at various pH levels. No significant proteins were released at pH 4.0 in minimal medium or citrate buffer, whereas in acetate buffer,
B. suis
released a substantial amount of soluble proteins. Comparison of 13 N-terminal amino acid sequences determined by Edman degradation with their corresponding genomic sequences revealed that all of these proteins possessed a signal peptide indicative of their periplasmic location. Ten proteins are putative substrate binding proteins, including a homologue of the nopaline binding protein of
Agrobacterium tumefaciens
. The absence of this homologue in
Brucella melitensis
was due to the deletion of a 7.7-kb DNA fragment in its genome. We also characterized for the first time a hypothetical 9.8-kDa basic protein composed of five amino acid repeats. In
B. suis
, this protein contained 9 repeats, while 12 were present in the
B. melitensis
orthologue.
B. suis
in acetate buffer depended on neither the
virB
type IV secretory system nor the
omp31
gene product. However, the integrity of the
omp25
gene was required for release at acidic pH, while the absence of
omp25b
or
omp25c
displayed smaller effects. Together, these results suggest that Omp25 is involved in the membrane permeability of
Brucella
in acidic medium.
The Phosphatidylinositol 3-Kinase/Protein Kinase B Signaling Pathway Is Activated by Lipoteichoic Acid and Plays a Role in Kupffer Cell Production of Interleukin-6 (IL-6) and IL-10
Authors: Dahle Maria K. , Øverland Gunhild , Myhre Anders E. , Stuestøl Jon Fredrik , Hartung Thomas , Krohn Claus Danckert , Mathiesen Øystein , Wang Jacob E. , Aasen Ansgar O. 
Published: September 2004

ABSTRACTSepsis caused by gram-positive bacteria lacking lipopolysaccharide (LPS) has become a major and increasing cause of mortality in intensive-care units. We have recently demonstrated that the gram-positive-specific bacterial cell wall component lipoteichoic acid (LTA) stimulates the release of the proinflammatory cytokines in Kupffer cells in culture. In the present study, we have started to assess the signal transduction events by which LTA induces the production of tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and the anti-inflammatory cytokine IL-10 in rat Kupffer cells. LTA was found to trigger phosphorylation of mitogen-activated protein kinases (MAPK) (p38 MAPK and ERK 1/2) and protein kinase B (PKB). Compared to LPS, LTA was more potent in inducing PKB phosphorylation after 40 min, although we found that the cytokine responses were similar. For both bacterial molecules, blocking phosphatidylinositol 3-kinase (PI3-K; Ly294002) or Janus kinase 2 (JAK-2; AG490) particularly affected the induction of IL-6 and IL-10 release, whereas TNF-α levels were strongly reduced by inhibition of Src family tyrosine kinases (PP2). All three cytokines were reduced by inhibition of p38 MAPK (SB202190) or the broad-range tyrosine kinase inhibitor genistein, whereas IL-6 release was particularly blocked by inhibition of ERK 1/2 (PD98059). Divergences in the regulatory pathways controlling TNF-α, IL-10, and IL-6 production in Kupffer cells following LPS or LTA stimulation may create a basis for understanding how the balance between pro- and anti-inflammatory cytokines is regulated in the liver following infections by gram-positive or gram-negative bacteria.
Escherichia coli
Cytotoxic Necrotizing Factor 1 Inhibits Intestinal Epithelial Wound Healing In Vitro after Mechanical Injury
Authors: Brest Patrick , Turchi Laurent , Le'Negrate Gaëlle , Berto Frédérick , Moreilhon Chimène , Mari Bernard , Ponzio Gilles , Hofman Paul 
Published: September 2004

ABSTRACT

Cytotoxic necrotizing factor type 1 (CNF1) from
Escherichia coli
activates the small GTP-binding proteins of the Rho family (Rho, Rac, and Cdc42) by catalyzing their deamidation at a specific glutamine residue. Since RhoA, Rac, and Cdc42 play a pivotal role in cell migration during the early phase of wound repair, we investigated whether CNF1 was able to interfere with wound healing in intestinal epithelial monolayers (T84 cells). After mechanical injury, we found that CNF1 blocks epithelial wound repair within 48 h. This effect was characterized by cell elongation and filopodium formation on the leading edge, in association with permanent phosphorylation of the focal adhesion kinase (FAK) via Rho activation. Moreover, inhibition of Rho kinase with Y-27632 decreased CNF1-mediated permanent FAK phosphorylation, leading to complete restitution of wound repair within 24 h. In addition, we found that CNF1 induced upregulation of mitogen-activated protein kinases (MAPK) activation. Moreover, activation of Rac and MAPK by CNF1 increased matrix metalloproteinase 9 expression in wounded T84 monolayers. Taken together, these results provide evidence that CNF1 strongly impairs intestinal epithelial wound healing.
Increased Rate of Apoptosis and Diminished Phagocytic Ability of Human Neutrophils Infected with Afa/Dr Diffusely AdheringEscherichia coliStrains
Authors: Brest Patrick , Bétis Frédéric , Çuburu Nicolas , Selva Eric , Herrant Magali , Servin Alain , Auberger Patrick , Hofman Paul 
Published: September 2004

ABSTRACTThe proinflammatory effect of Afa/Dr diffusely adheringEscherichia coli(Afa/Dr DAEC) strains have been recently demonstrated in vitro by showing that polymorphonuclear leukocyte (PMN) transepithelial migration is induced after bacterial colonization of apical intestinal monolayers. The effect of Afa/Dr DAEC-PMN interaction on PMN behavior has been not investigated. Because of the putative virulence mechanism of PMN apoptosis during infectious diseases and taking into account the high level of expression of the decay-accelerating factor (DAF, or CD55), the receptor of Afa/Dr DAEC on PMNs, we sought to determine whether infection of PMNs by Afa/Dr DAEC strains could promote cell apoptosis. We looked at the behavior of PMNs incubated with Afa/Dr DAEC strains once they had transmigrated across polarized monolayers of intestinal (T84) cells. Infection of PMNs by Afa/Dr DAEC strains induced PMN apoptosis characterized by morphological nuclear changes, DNA fragmentation, caspase activation, and a high level of annexin V expression. However, transmigrated and nontransmigrated PMNs incubated with Afa/Dr DAEC strains showed similar elevated global caspase activities. PMN apoptosis depended on their agglutination, induced by Afa/Dr DAEC, and was still observed after preincubation of PMNs with anti-CD55 and/or anti-CD66 antibodies. Low levels of phagocytosis of Afa/Dr DAEC strains were observed both in nontransmigrated and in transmigrated PMNs compared to that observed with the controlE. coliDH5α strain. Taken together, these data strongly suggest that interaction of Afa/Dr DAEC with PMNs may increase the bacterial virulence both by inducing PMN apoptosis through an agglutination process and by diminishing their phagocytic capacity.
Borrelia burgdorferiChanges Its Surface Antigenic Expression in Response to Host Immune Responses
Authors: Liang Fang Ting , Yan Jun , Mbow M. Lamine , Sviat Steven L. , Gilmore Robert D. , Mamula Mark , Fikrig Erol 
Published: September 2004

ABSTRACTThe Lyme disease spirochete,Borrelia burgdorferi, causes persistent mammalian infection despite the development of vigorous immune responses against the pathogen. To examine spirochetal phenotypes that dominate in the hostile immune environment, the mRNA transcripts of four prototypic surface lipoproteins, decorin-binding protein A (DbpA), outer surface protein C (OspC), BBF01, and VlsE, were analyzed by quantitative reverse transcription-PCR under various immune conditions. We demonstrate thatB. burgdorferichanges its surface antigenic expression in response to immune attack.dbpAexpression was unchanged while the spirochetes decreasedospCexpression by 446 times and increased BBF01 andvlsEexpression up to 20 and 32 times, respectively, under the influence of immune pressure generated in immunocompetent mice during infection. This change in antigenic expression could be induced by passively immunizing infected severe combined immunodeficiency mice with specificBorreliaantisera or OspC antibody and appears to allowB. burgdorferito resist immune attack.
Comparison of Immunogenicities of RecombinantPlasmodium vivaxMerozoite Surface Protein 1 19- and 42-Kilodalton Fragments Expressed inEscherichia coli
Authors: Sachdeva Suraksha , Ahmad Gul , Malhotra Pawan , Mukherjee Paushali , Chauhan V. S. 
Published: September 2004

ABSTRACTThe 42- and 19-kDa C-terminal fragments of merozoite surface protein 1 (MSP-142and MSP-119, respectively) are both promising blood-stage vaccine candidate antigens. At present, it is not clear which of the two antigens will be more suitable for inclusion in a cocktail malaria vaccine. In the present study, we expressed the two C-terminal fragments ofPlasmodium vivaxMSP-1 (PvMSP-1) in anEscherichia coliexpression system and purified them by using a rapid two-step protocol. Both of the products were recognized by monoclonal antibodies against PvMSP-1 as well as by immune sera from several individuals exposed toP. vivax. We analyzed and compared the immunological responses to recombinant PvMSP-119and PvMSP-142in mice by using six different adjuvant formulations. Moderate to high antibody responses were observed with both of the antigens in different adjuvant formulations. Surprisingly, alum, which is generally considered to be a poor adjuvant for recombinant malaria antigens, was found to be as good an adjuvant as Montanide ISA 720, ASO2A, and other adjuvant formulations. Most adjuvant formulations induced high levels of immunoglobulin G1 (IgG1), followed by IgG3 and IgG2. Lymphocytes from animals in the PvMSP-142- and PvMSP-119-immunized groups showed proliferative responses upon stimulation with the respective antigens, and high levels of interleukin-4 (IL-4), IL-5, and gamma interferon were detected in the culture supernatants. Immunodepletion studies with sera from mice immunized with these two antigens showed that while immunization with PvMSP-142does produce a PvMSP-119-specific response, a substantial portion is also focused on structures in PvMSP-142not represented by the epidermal growth factor-like domains of PvMSP-119. These findings may have implications for the design of MSP-1-based vaccine constructs.
The Ton System, an ABC Transporter, and a Universally Conserved GTPase Are Involved in Iron Utilization by
Brucella melitensis
16M
Authors: Danese Isabelle , Haine Valerie , Delrue Rose-May , Tibor Anne , Lestrate Pascal , Stevaux Olivier , Mertens Pascal , Paquet Jean-Yves , Godfroid Jacques , De Bolle Xavier , Letesson Jean-Jacques 
Published: September 2004

ABSTRACT

Brucella
spp. are gram-negative intracellular facultative pathogens that are known to produce 2,3-dihydroxybenzoic acid (DHBA), a catechol siderophore that is essential for full virulence in the natural host. The mechanism of DHBA entry into
Brucella
and other gram-negative bacteria is poorly understood. Using mini-Tn
5Kmcat
mutagenesis, we created a transposon library of
Brucella melitensis
16M and isolated 32 mutants with a defect in iron acquisition or assimilation. Three of these transposon mutants are deficient in utilization of DHBA. Analysis of these three mutants indicated that the ExbB, DstC, and DugA proteins are required for optimal assimilation of DHBA and/or citrate. ExbB is part of the Ton complex, and DstC is a permease homologue of an iron(III) ABC transporter; in gram-negative bacteria these two complexes are involved in the uptake of iron through the outer and inner membranes, respectively. DugA is a new partner in iron utilization that exhibits homology with the bacterial conserved GTPase YchF. Based on this homology, DugA could have a putative regulatory function in iron assimilation in
Brucella
. None of the three mutants was attenuated in cellular models or in the mouse model of infection, which is consistent with the previous suggestion that DHBA utilization is not required in these models.
Limited Role of Antibody in Clearance of
Streptococcus pneumoniae
in a Murine Model of Colonization
Authors: McCool Tera L. , Weiser Jeffrey N. 
Published: September 2004

ABSTRACT

Colonization is the first step in the interaction between
Streptococcus pneumoniae
and its human host. To better understand the mechanisms contributing to natural carriage, a mouse model of pneumococcal colonization was developed with a clinical isolate of
S. pneumoniae
previously characterized in experimental colonization of humans. Similar to carriage events in humans, colonization of mice was self-limited and there was no evidence of lower respiratory tract or invasive disease. Carriage induced a serum antibody response to whole pneumococci that was associated temporally with clearance of colonization in three inbred strains of mice. Individual mice, however, did not demonstrate a correlation between the density of colonization and amounts of serum or of mucosal antibodies, including antibodies of different isotypes and antigenic specificities. The role of antibody in the clearance of carriage was then examined in mice with genetic defects in humoral immunity.
xid
mice, which have deficient responses to polysaccharide antigens, cleared colonization at the same rate as the parent strain. Finally, we showed that μMT mice, which lack mature B cells and fail to produce antibody, were unaffected in the density or duration of colonization. These results demonstrate that antibody is not required for clearance of pneumococcal colonization in mice.
Role of B7 Costimulatory Molecules in Mediating Systemic and Mucosal Antibody Responses to AttenuatedSalmonella entericaSerovar Typhimurium and Its Cloned Antigen
Authors: Garcia Carlos A. , Martin Michael , Michalek Suzanne M. 
Published: September 2004

ABSTRACTThe purpose of the present study was to evaluate the ability of an attenuatedSalmonella entericaserovar Typhimurium vaccine strain to up-regulate B7-1 and B7-2 on antigen-presenting cells and to examine the functional roles these costimulatory molecules play in mediating immune responses toSalmonellaand to an expressed cloned antigen, the saliva-binding region (SBR) of antigen I/II. In vitro stimulation of B cells (B220+), macrophages (CD11b+), and dendritic cells (CD11c+) withS. entericaserovar Typhimurium induced an up-regulation of B7-2 and, especially, B7-1 expression. The in vivo functional roles of B7-1, B7-2, and B7-1/2 were evaluated in BALB/c wild-type and B7-1, B7-2, and B7-1/2 knockout (KO) mice following intranasal immunization with theSalmonellaexpressing the cloned SBR. Differential requirements for B7-1 and B7-2 were observed upon primary and secondary immunizations. Compared to wild-type controls, B7-1 and B7-2 KO mice had reduced mucosal and systemic anti-Salmonellaantibody responses after a single immunization, while only B7-1 KO mice exhibited suppressed anti-Salmonellaantibody responses following the second immunization. Mucosal and systemic antibody responses to SBR were reduced following the primary immunization, whereas a compensatory role for either B7-1 or B7-2 was observed after the second immunization. B7-1/2 double KO mice failed to induce detectable levels of mucosal or systemic immunoglobulin A (IgA) or IgG antibody responses to eitherSalmonellaor SBR. These findings demonstrate that B7-1 and B7-2 can play distinct as well as redundant roles for mediating mucosal and systemic antibody responses, which are likely dependent upon the nature of the antigen.
Bacteroides fragilisEnterotoxin Induces Intestinal Epithelial Cell Secretion of Interleukin-8 through Mitogen-Activated Protein Kinases and a Tyrosine Kinase-Regulated Nuclear Factor-κB Pathway
Authors: Wu Shaoguang , Powell Jan , Mathioudakis Nes , Kane Sheryl , Fernandez Ellen , Sears Cynthia L. 
Published: September 2004

ABSTRACTEnterotoxigenicBacteroides fragilis(ETBF) secretes a 20-kDa metalloprotease toxin termedB. fragilistoxin (BFT). ETBF disease in animals is associated with an acute inflammatory response in the intestinal mucosa, and lethal hemorrhagic colitis may occur in rabbits. In this study, we confirmed recent reports (J. M. Kim, Y. K. Oh, Y. J. Kim, H. B. Oh, and Y. J. Cho, Clin. Exp. Immunol. 123:421-427, 2001; L. Sanfilippo, C. K. Li, R. Seth, T. J. Balwin, M. J. Menozzi, and Y. R. Mahida, Clin. Exp. Immunol. 119:456-463, 2000) that purified BFT stimulates interleukin-8 (IL-8) secretion by human intestinal epithelial cells (HT29/C1 cells) and demonstrate that stimulation of IL-8 production is dependent on biologically active BFT and independent of serum. Induction of IL-8 mRNA expression occurs rapidly and ceases by 6 h after BFT treatment, whereas IL-8 secretion continues to increase for at least 18 h. Our data suggest that BFT-stimulated IL-8 secretion involves tyrosine kinase-dependent activation of nuclear factor-κB (NF-κB) as well as activation of the mitogen-activated protein kinases (MAPKs), p38 and extracellular signal-related kinase. Simultaneous activation of NF-κB and MAPKs appears necessary for secretion of IL-8 by HT29/C1 cells treated with BFT.
Merozoite Surface Protein 4/5 Provides Protection against Lethal Challenge with a Heterologous Malaria Parasite Strain
Authors: Goschnick M. W. , Black C. G. , Kedzierski L. , Holder A. A. , Coppel R. L. 
Published: September 2004

ABSTRACTImmunization with merozoite surface protein 4/5 (MSP4/5), the murine malaria homologue ofPlasmodium falciparumMSP4 and MSP5, has been shown to protect mice against challenge by parasites expressing the homologous form of the protein. The gene encoding MSP4/5 was sequenced from a number ofPlasmodium yoeliiisolates in order to assess the level of polymorphism in the protein. The gene was found to be highly conserved among the 13P. yoeliiisolates sequenced, even though many of the same isolates showed pronounced variability in their MSP119sequences. Nonsynonymous mutations were detected only for the isolatesPlasmodium yoelii nigeriensisN67 andPlasmodium yoelii killicki193L and 194ZZ. Immunization and challenge of BALB/c mice showed that the heterologous MSP4/5 proteins were able to confer a level of protection against lethalPlasmodium yoelii yoeliiYM challenge infection similar to that induced by immunization with the homologous MSP4/5 protein. To explore the limits of heterologous protection, mice were immunized with recombinant MSP4/5 protein fromPlasmodium bergheiANKA andPlasmodium chabaudi adamiDS and challenged withP. y. yoeliiYM. Interestingly, significant protection was afforded byP. bergheiANKA MSP4/5, which shows 81% sequence identity withP. y. yoeliiYM MSP4/5, but it was abolished upon reduction and alkylation. Significant protection was not observed for mice immunized with recombinantP. c. adamiDS MSP4/5, which shows 55.7% sequence identity withP. y. yoeliiYM MSP4/5. This study demonstrates the robustness of MSP4/5 in conferring protection against variant forms of the protein in a murine challenge system, in contrast to the situation found for other asexual-stage proteins, such as MSP119and AMA1.