bluuebunny/crossref_metadata_2025_split huggingface dataset:
CD4+-T-Cell Responses Generated during MurineSalmonella entericaSerovar Typhimurium Infection Are Directed towards Multiple Epitopes within the Natural Antigen FliC
Authors: Bergman Molly A. , Cummings Lisa A. , Alaniz Robert C. , Mayeda Laura , Fellnerova Ivana , Cookson Brad T. 
Published: October 2005

ABSTRACTThe flagellar filament protein FliC is a natural antigen recognized by memory CD4+T cells recovered fromSalmonella entericaserovar Typhimurium-infected humans and mice. To further investigate T-cell responses to FliC, we derived FliC-specific CD4+-T-cell clones from mice of two different haplotypes following oralS. entericaserovar Typhimurium infection. Using C-terminal truncations of MalE-FliC recombinant fusion proteins, we mapped antigenic activity to four different regions of FliC; three of the four epitope-containing regions were present in both FliC and the alternate flagellin subunit FljB. We determined that two novel FliC epitopes were also present in flagellins from several gram-negative enteric bacterial species: Ek-restricted FliC 80-94 (amino acids 80 to 94) and Ab-restricted FliC 455-469. Further mapping confirmed the presence of two previously identified FliC epitopes: Ak-restricted FliC 339-350 and Ab-restricted FliC 428-442. Therefore, like the recognition site of the innate immune receptor Toll-like receptor 5, three of four FliC epitopes recognized by CD4+T cells colocalize in the D0/D1 domains of FliC.Salmonella-infected macrophages and dendritic cells stimulated epitope-specific CD4+-T-cell proliferation; infected dendritic cells also activated T cells to produce gamma interferon. These data demonstrate thatSalmonellainfection generates murine CD4+-T-cell responses to multiple epitopes in the natural antigen FliC and that recognition of infected phagocytes by FliC-specific CD4+T cells triggers effector functions known to be essential for protective immunity. Together, these data suggest that FliC-specific CD4+T cells may contribute to cell-mediated host defenses againstSalmonella.
The Nickel-Responsive Regulator NikR Controls Activation and Repression of Gene Transcription inHelicobacter pylori
Authors: Ernst Florian D. , Kuipers Ernst J. , Heijens Angela , Sarwari Roya , Stoof Jeroen , Penn Charles W. , Kusters Johannes G. , van Vliet Arnoud H. M. 
Published: October 2005

ABSTRACTThe NikR protein is a nickel-dependent regulatory protein which is a member of the ribbon-helix-helix family of transcriptional regulators. The gastric pathogenHelicobacter pyloriexpresses a NikR ortholog, which was previously shown to mediate regulation of metal metabolism and urease expression, but the mechanism governing the diverse regulatory effects had not been described until now. In this study it is demonstrated that NikR can regulateH. pylorinickel metabolism by directly controlling transcriptional repression of NixA-mediated nickel uptake and transcriptional induction of urease expression. Mutation of the nickel uptake genenixAin anH. pylori26695nikRmutant restored the ability to grow in Brucella media supplemented with 200 μM NiCl2but did not restore nickel-dependent induction of urease expression. Nickel-dependent binding of NikR to the promoter of thenixAgene resulted in nickel-repressed transcription, whereas nickel-dependent binding of NikR to the promoter of theureAgene resulted in nickel-induced transcription. Subsequent analysis of NikR binding to thenixAandureApromoters showed that the regulatory effect was dependent on the location of the NikR-recognized binding sequence. NikR recognized the region from −13 to +21 of thenixApromoter, encompassing the +1 and −10 region, and this binding resulted in repression ofnixAtranscription. In contrast, NikR bound to the region from −56 to −91 upstream of theureApromoter, resulting in induction of urease transcription. In conclusion, the NikR protein is able to function both as a repressor and as an activator of gene transcription, depending on the position of the binding site.
Partially Assembled K99 Fimbriae Are Required for Protection
Authors: Ascón Miguel A. , Ochoa-Repáraz Javier , Walters Nancy , Pascual David W. 
Published: October 2005

ABSTRACTAntibodies to K99 fimbriae afford protection to F5+bovine enterotoxigenicEscherichia coli(ETEC). Previous studies show that murine dams immunized withSalmonellavaccine vectors stably expressing K99 fimbriae confer protection to ETEC-challenged neonatal pups. To begin to address adaptation of the K99 scaffold to display heterologous B- and T-cell epitopes, studies were conducted to determine how much of the assembled K99 fimbria is required to maintain protective immunity. Sequential deletions in the K99 gene clusters were made, resulting in diminished localization of the K99 fimbrial subunit in the outer membrane. As placement of the K99 fimbrial subunit became progressively contained within the vaccine vector, diminished immunoglobulin A (IgA) and IgG1 antibody titers, as well as diminished Th2-type cytokine responses, were observed in orally immunized mice. Deletion offanGH, which greatly reduced the export of the fimbrial subunit to the outer membrane, showed only partial reduction in protective immunity. By contrast, deletion offanDEFGH, which also reduced the export of the fimbrial subunit to the outer membrane but retained more subunit in the cytoplasm, resulted in protective immunity being dramatically reduced. Thus, these studies showed that retention of K99 fimbrial subunit as native fimbriae or with the deletion offanGHis sufficient to confer protection.
Intestinal Innate Immunity toCampylobacter jejuniResults in Induction of Bactericidal Human Beta-Defensins 2 and 3
Authors: Zilbauer Matthias , Dorrell Nick , Boughan Parjeet K. , Harris Andrew , Wren Brendan W. , Klein Nigel J. , Bajaj-Elliott Mona 
Published: October 2005

ABSTRACTCampylobacter jejuniis the most prevalent cause of bacterial diarrhea worldwide. Despite the serious health problems caused by this bacterium, human innate immune responses toC. jejuniinfection remain poorly defined. Human β-defensins, a family of epithelial antimicrobial peptides, are a major component of host innate defense at the gastrointestinal mucosal surface. In this study, the effect of two differentC. jejuniwild-type strains on human intestinal epithelial innate responses was investigated. Up-regulation of β-defensin gene and peptide expression during infection was observed and recombinant β-defensins were shown to have a direct bactericidal effect againstC. jejunithrough disruption of cell wall integrity. Further studies using an isogenic capsule-deficient mutant showed that, surprisingly, the absence of the bacterial polysaccharide capsule did not change the innate immune responses induced byC. jejunior the ability ofC. jejunito survive exposure to recombinant β-defensins. This study suggests a major role for this family of antimicrobial peptides in the innate immune defense against this human pathogen.
Effects of Forskolin on Kupffer Cell Production of Interleukin-10 and Tumor Necrosis Factor Alpha Differ from Those of Endogenous Adenylyl Cyclase Activators: Possible Role for Adenylyl Cyclase 9
Authors: Dahle Maria K. , Myhre Anders E. , Aasen Ansgar O. , Wang Jacob E. 
Published: October 2005

ABSTRACTProinflammatory cytokines like tumor necrosis factor alpha (TNF-α) that are released from Kupffer cells may trigger liver inflammation and damage. Hence, endogenous mechanisms for limiting TNF-α expression are crucial for avoiding the development of sepsis. Such mechanisms include the anti-inflammatory actions of interleukin-10 (IL-10) as well as signaling induced by the intracellular second messenger cyclic AMP (cAMP). Kupffer cells express several receptors that activate cAMP synthesis, including E-prostanoid receptors and β-adrenergic receptors. The expression and role of specific adenylyl cyclases in the inhibition of Kupffer cell activation have so far not been subject to study. Pretreatment of rat Kupffer cell cultures with cAMP analogues [8-(4-chlorophenyl)-thio-cAMP], adenylyl cyclase activator (forskolin), or ligands for G-coupled receptors (isoproterenol or prostaglandin E2) 30 min before the addition of lipopolysaccharide (LPS) (1 μg/ml) caused attenuated TNF-α levels in culture medium (forskolin/isoproterenol,P≤ 0.05; prostaglandin E2,P≤ 0.01). Forskolin also reduced IL-10 mRNA and protein (P≤ 0.05), which was not observed with the other cAMP-inducing agents. Furthermore, we found that rat Kupffer cells express high levels of the forskolin-insensitive adenylyl cyclase 9 compared to whole liver and that this expression is down-regulated by LPS (P≤ 0.05). We conclude that regulation of TNF-α and IL-10 in Kupffer cells depends on the mechanism by which cAMP is elevated. Forskolin and prostaglandin E2differ in their effects, which suggests a possible role of forskolin-insensitive adenylyl cyclases like adenylyl cyclase 9.
Role of Complement Receptor Type 2 and Endogenous Complement in the Humoral Immune Response to Conjugates of Complement C3d and Pneumococcal Serotype 14 Capsular Polysaccharide
Authors: Mitsuyoshi Joyce K. , Hu Yong , Test Samuel T. 
Published: October 2005

ABSTRACTConjugation of the complement fragment C3d to both T-cell-dependent (TD) protein and T-cell-independent type 2 (TI-2) polysaccharide antigens enhances the humoral immune response in mice immunized with either type of antigen. However, the ability of C3d-protein conjugates to enhance the antibody response in mice deficient in complement receptor types 1 and 2 (CR1 and CR2) has raised questions about the role of C3d-CR2 interactions in the adjuvant effect of C3d. In this study, we examined the role of CR2 binding and endogenous complement activation in the antibody response to conjugates of C3d and serotype 14 pneumococcal capsular polysaccharide (PPS14). To block binding of PPS14-C3d conjugates to CR2, mice were immunized with a mixture of vaccine and (CR2)2-immunoglobulin G1 (IgG1). Mice receiving (CR2)2-IgG1 at the time of primary immunization had a marked reduction in the primary anti-PPS14 antibody response but an enhanced secondary anti-PPS14 response, suggesting that C3d-CR2 interactions are required for the primary response but can have negative effects on the memory response. Further, compared with mice receiving PPS14-C3d having a high C3d/PPS14 ratio, mice immunized with PPS14-C3d with low C3d/PPS14 ratios had an enhanced secondary antibody response. Treatment of mice with cobra venom factor to deplete complement had insignificant effects on the antibody response to PPS14-C3d. Experiments with CBA/Nxidmice confirmed that PPS14-C3d conjugates retain the characteristics of TI-2 rather than TD antigens. Thus, the adjuvant effect of C3d conjugated to PPS14 requires C3d-CR2 interactions, does not require activation of endogenous complement, and is not mediated by TD carrier effects.
Influence of CR3 (CD11b/CD18) Expression on Phagocytosis ofBordetella pertussisby Human Neutrophils
Authors: Mobberley-Schuman Paula S. , Weiss Alison A. 
Published: October 2005

ABSTRACTCR3 (CD11b/CD18) is expressed on neutrophils, and the engagement of CR3 can promote phagocytosis. CR3 serves as the receptor for theBordetella pertussisadhesin filamentous hemagglutinin (FHA) and for the adenylate cyclase toxin (ACT), which blocks neutrophil function. The influence of CR3, FHA, and ACT on the phagocytosis ofB. pertussisby human neutrophils was examined. The surface expression and function of CR3 are regulated. Tumor necrosis factor alpha (TNF-α) and gamma interferon (IFN-γ) increased CR3 surface expression, but only TNF-α increased the ability of neutrophils to phagocytoseB. pertussis, suggesting that elevated CR3 expression alone is not sufficient to promote phagocytosis. Purified FHA and pertussis toxin also increased the surface expression of CR3 on neutrophils, while ACT and the B subunit of pertussis toxin did not affect CR3 expression. FHA-mediated attachment to CR3 can lead to phagocytosis, especially in the absence of ACT. FHA mutants failed to attach and were not phagocytosed by neutrophils. Similarly, an antibody to CR3 blocked both attachment and phagocytosis. The addition of exogenous FHA enhanced the attachment and phagocytosis of wild-typeB. pertussisand FHA mutants. Mutants lacking the SphB1 protease, which cleaves FHA and allows the release of FHA from the bacterial surface, were phagocytosed more efficiently than wild-type bacteria. ACT mutants were efficiently phagocytosed, but wild-typeB. pertussisor ACT mutants plus exogenous ACT resisted phagocytosis. These studies suggest that the activation and surface expression of CR3, FHA expression, and the efficiency of ACT internalization all influence whetherB. pertussiswill be phagocytosed and ultimately killed by neutrophils.
Intraspecies and Temperature-Dependent Variations in Susceptibility of
Yersinia pestis
to the Bactericidal Action of Serum and to Polymyxin B
Authors: Anisimov Andrey P. , Dentovskaya Svetlana V. , Titareva Galina M. , Bakhteeva Irina V. , Shaikhutdinova Rima Z. , Balakhonov Sergey V. , Lindner Buko , Kocharova Nina A. , Senchenkova Sof'ya N. , Holst Otto , Pier Gerald B. , Knirel Yuriy A. 
Published: October 2005

ABSTRACT

Lipopolysaccharide (LPS) structure impacts the bactericidal action of cationic peptides, such as polymyxin B (PMB), and sensitivity to killing by normal human serum (NHS). Cultivation of different subspecies strains of
Yersinia pestis
isolated from unrelated geographic origins at various temperatures (mammals, 37°C; fleas, 25°C; or winter hibernation, 6°C) affects LPS composition and structure. We tested the susceptibilities of various strains of
Y. pestis
grown at these different temperatures to PMB and serum bactericidal killing. Both properties varied significantly in response to temperature changes. In
Y. pestis
subsp.
pestis
(the main subspecies causing human plague), high levels of resistance to PMB and NHS were detected at 25°C. However, at the same temperature,
Y. pestis
subsp.
caucasica
was highly sensitive to PMB. At both of the extreme temperatures, all strains were highly susceptible to PMB. At 25°C and 37°C,
Y. pestis
subsp.
caucasica
strain 1146 was highly susceptible to the bactericidal activity of 80% NHS. All
Y. pestis
strains studied were able to grow in heat-inactivated human serum or in 80% normal mouse serum. At 6°C, all strains were highly sensitive to NHS. Variations in the PMB resistance of different bacterial cultures related to both the content of cationic components (4-amino-4-deoxyarabinose in lipid A and glycine in the core) and a proper combination of terminal monosaccharides in the LPS. The NHS resistance correlated with an elevated content of
N
-acetylglucosamine in the LPS. Structural variation in the LPS of
Y. pestis
correlates with the organism's ability to resist innate immunity in both fleas and mammals.
Burkholderia pseudomallei-Induced Expression of Suppressor of Cytokine Signaling 3 and Cytokine-Inducible Src Homology 2-Containing Protein in Mouse Macrophages: a Possible Mechanism for Suppression of the Response to Gamma Interferon Stimulation
Authors: Ekchariyawat P. , Pudla S. , Limposuwan K. , Arjcharoen S. , Sirisinha S. , Utaisincharoen P. 
Published: October 2005

ABSTRACTBurkholderia pseudomallei, the causative agent of melioidosis, is a facultative intracellular gram-negative bacterium that is able to survive and multiply in macrophages. Previously, we reported thatB. pseudomalleiwas able to escape macrophage killing by interfering with the expression of inducible nitric oxide synthase (iNOS). In the present study, we extended this finding and demonstrated thatB. pseudomalleiwas able to activate the expression of suppressor of cytokine signaling 3 (SOCS3) and cytokine-inducible Src homology 2-containing protein (CIS) but not SOCS1 in a mouse macrophage cell line (RAW 264.7). The expression of SOCS3 and CIS inB. pseudomallei-infected macrophages directly correlated with a decreased gamma interferon (IFN-γ) signaling response, as indicated by a reduction in Y701-STAT-1 phosphorylation (pY701-STAT-1). Moreover, a reduction in the expression of IFN-γ-induced proteins, such as interferon regulatory factor 1 (IRF-1), was observed inB. pseudomallei-infected macrophages that were treated with IFN-γ. Since pY701-STAT-1 and IRF-1 are essential transcription factors for regulating iNOS expression, the failure to activate these factors could also result in depression of iNOS expression and a loss of macrophage killing capacity. Taken together, the data indicate that the activation of SOCS3 and CIS expression inB. pseudomallei-infected macrophages interfered with IFN-γ signaling, thus allowing the bacteria to escape killing by these phagocytic cells.
Characterization of Two Novel Cryptococcal Mannoproteins Recognized by Immune Sera
Authors: Biondo Carmelo , Messina Luciano , Bombaci Mauro , Mancuso Giuseppe , Midiri Angelina , Beninati Concetta , Cusumano Valentina , Gerace Elisabetta , Papasergi Salvatore , Teti Giuseppe 
Published: October 2005

ABSTRACT

Host defenses against the encapsulated yeast
Cryptococcus neoformans
involve both humoral and cell-mediated immunity. Mannoproteins (MPs) are a heterogeneous class of immunodominant glycoproteins which have been only incompletely characterized. In this study, we report on the molecular features of two novel MPs that are recognized by serum antibodies during cryptococcosis. After fractionation of extracellular cryptococcal products, MPs reacted more strongly than other components with sera from
C. neoformans
-infected AIDS patients. Further fractionation and Western blot analysis of MPs evidenced the presence of highly reactive bands with molecular masses of 250, 125, 115, and 84 kDa. The 115- and 84-kDa bands contained significant amounts of N-linked oligosaccharides, as shown by decreased molecular mass after peptide-
N
-glycosidase F treatment. N-terminal amino acid sequences of the two bands were used to search
C. neoformans
nucleotide databases. Homologous genomic sequences were used to synthesize DNA probes and isolate cDNA clones containing the full-length genes, which were designated
MP84
and
MP115.
Both genes showed the presence of a serine/threonine-rich region, a potential site for heavy glycosylation.
MP84
and
MP115
showed homology with, respectively, polysaccharide deacetylases and carboxylesterases from other organisms. Recombinant, deglycosylated proteins expressed in
Escherichia coli
still reacted with sera from patients, albeit more weakly than natural MPs, indicating that at least some of the reactive epitopes were retained in the recombinant forms. In conclusion, we identified two novel MPs that are important targets of antibody responses during cryptococcosis. These data may be useful to devise alternative immunity-based strategies to control the disease.
Immune Responses against a Single CD8+-T-Cell Epitope Induced by Virus Vector Vaccination Can Successfully ControlTrypanosoma cruziInfection
Authors: Miyahira Yasushi , Takashima Yasuhiro , Kobayashi Seiki , Matsumoto Yasunobu , Takeuchi Tsutomu , Ohyanagi-Hara Mutsuko , Yoshida Ayako , Ohwada Akihiko , Akiba Hisaya , Yagita Hideo , Okumura Ko , Ogawa Hideoki 
Published: October 2005

ABSTRACTIn order to develop CD8+-T-cell-mediated immunotherapy against intracellular infectious agents, vaccination using recombinant virus vectors has become a promising strategy. In this study, we generated recombinant adenoviral and vaccinia virus vectors expressing a single CD8+-T-cell epitope, ANYNFTLV, which is derived from aTrypanosoma cruziantigen. Immunogenicity of these two recombinant virus vectors was confirmed by the detection of ANYNFTLV-specific CD8+T cells in the spleens of immunized mice. Priming/boosting immunization using combinations of these two recombinant virus vectors revealed that the adenovirus vector was efficient for priming and the vaccinia virus vector was effective for boosting the CD8+-T-cell responses. Moreover, we also demonstrated that the ANYNFTLV-specific CD8+-T-cell responses were further augmented by coadministration of recombinant vaccinia virus vector expressing the receptor activator of NFκB (RANK) ligand as an adjuvant. By priming with the adenovirus vector expressing ANYNFTLV and boosting with the vaccinia virus vectors expressing ANYNFTLV and RANK ligand, the immunized mice were efficiently protected from subsequent challenge with lethal doses ofT. cruzi. These results indicated, for the first time, that the induction of immune responses against a single CD8+-T-cell epitope derived from an intrinsicT. cruziantigen was sufficient to control lethalT. cruziinfection.
Effects of Ploidy and Mating Type on Virulence of
Candida albicans
Authors: Ibrahim Ashraf S. , Magee B. B. , Sheppard D. C. , Yang Molly , Kauffman Sarah , Becker Jeff , Edwards John E. , Magee P. T. 
Published: October 2005

ABSTRACT

Candida albicans
is the most common fungal pathogen of humans. The recent discovery of sexuality in this organism has led to the demonstration of a mating type locus which is usually heterozygous, although some isolates are homozygous. Tetraploids can be formed between homozygotes of the opposite mating type. However, the role of the mating process and tetraploid formation in virulence has not been investigated. We describe here experiments using a murine model of disseminated candidiasis which demonstrate that in three strains, including CAI-4, the most commonly used strain background, tetraploids are less virulent than diploids and can undergo changes in ploidy during infection. In contrast to reports with other strains, we find that
MTL
homozygotes are almost as virulent as the heterozygotes. These results show that the level of ploidy in
Candida albicans
can affect virulence, but the mating type configuration does not necessarily do so.
Nasal Immunization with a Malaria Transmission-Blocking Vaccine Candidate, Pfs25, Induces Complete Protective Immunity in Mice against Field Isolates of
Plasmodium falciparum
Authors: Arakawa Takeshi , Komesu Ai , Otsuki Hitoshi , Sattabongkot Jetsumon , Udomsangpetch Rachanee , Matsumoto Yasunobu , Tsuji Naotoshi , Wu Yimin , Torii Motomi , Tsuboi Takafumi 
Published: October 2005

ABSTRACT

Malaria transmission-blocking vaccines based on antigens expressed in sexual stages of the parasites are considered one promising strategy for malaria control. To investigate the feasibility of developing noninvasive mucosal transmission-blocking vaccines against
Plasmodium falciparum
, intranasal immunization experiments with
Pichia pastoris
-expressed recombinant Pfs25 proteins were conducted. Mice intranasally immunized with the Pfs25 proteins in the presence of a potent mucosal adjuvant cholera toxin induced robust systemic as well as mucosal antibodies. All mouse immunoglobulin G (IgG) subclasses except IgG3 were found in serum at comparable levels, suggesting that the immunization induced mixed Th1 and Th2 responses. Consistent with the expression patterns of the Pfs25 proteins in the parasites, the induced immune sera specifically recognized ookinetes but not gametocytes. In addition, the immune sera recognized Pfs25 proteins with the native conformation but not the denatured forms, indicating that mucosal immunization induced biologically active antibodies capable of recognizing conformational epitopes of native Pfs25 proteins. Feeding
Anopheles dirus
mosquitoes with a mixture of the mouse immune sera and gametocytemic blood derived from patients infected with
P. falciparum
resulted in complete interference with oocyst development in mosquito midguts. The observed transmission-blocking activities were strongly correlated with specific serum antibody titers. Our results demonstrated for the first time that a
P. falciparum
transmission-blocking vaccine candidate is effective against field-isolated parasites and may justify the investigation of noninvasive mucosal vaccination regimens for control of malaria, a prototypical mucosa-unrelated mosquito-borne parasitic disease.