bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Strong Antigen-Specific T-Cell Response Is Associated with Age and Genetically Dependent Resistance to Avian Enteric Salmonellosis
Authors: Beal Richard K. , Powers Claire , Wigley Paul , Barrow Paul A. , Kaiser Pete , Smith Adrian L. 
Published: October 2005

ABSTRACTChicken genetics and age affect resistance to enteric infection withSalmonella entericaserovar Typhimurium and were used to identify the immune responses that may contribute to rapid clearance. When birds were infected at 40 days of age, line 61chickens cleared the infection more effectively than line N chickens, whereas when birds were infected at 10 days of age, both chicken lines were highly susceptible to infection. Antibody levels, T-cell responsiveness, and cytokine mRNA levels were all elevated during infection. A negative correlation between resistance and antigen-specific antibody production was observed in older chickens. However, this finding was not replicated for age-related resistance; we found that older chickens exhibited a stronger and more rapid antibody response than younger chickens. The levels of interleukin-1β (IL-1β) and gamma interferon (IFN-γ) mRNA were similar in the spleens and cecal tonsils of both line 61and line N chickens, except for higher levels of IL-1β in the spleens of line 61chickens at 6 days postinfection. Differences in the levels of IFN-γ and IL-1β 1β mRNA between the lines were more apparent in younger chickens, but while the increases were greater than those observed in the older chickens, the clearance of entericS. entericaserovar Typhimurium was much slower. The level of antigen-specific proliferation of splenocytes was associated with increased resistance in both experimental systems, and the strongest responses were observed in older and genetically resistant chickens. The data presented here implicate T-cell responses in the clearance ofS. entericaserovar Typhimurium from the intestine of infected chickens.
Bordetella bronchisepticaFlagellin Is a Proinflammatory Determinant for Airway Epithelial Cells
Authors: López-Boado Yolanda S. , Cobb Laura M. , Deora Rajendar 
Published: October 2005

ABSTRACTMotility is an important virulence phenotype for many bacteria, and flagellin, the monomeric component of flagella, is a potent proinflammatory factor. Of the threeBordetellaspecies,Bordetella pertussisandBordetella parapertussisare nonmotile human pathogens, whileBordetella bronchisepticaexpresses flagellin and causes disease in animals and immunocompromised human hosts. The BvgAS two-component signal transduction system regulates phenotypic-phase transition (Bvg+, Bvg−, and Bvgi) in bordetellae. The Bvg−phase ofB. bronchisepticais characterized by the expression of flagellin and the repression of adhesins and toxins necessary for the colonization of the respiratory tract.B. bronchisepticanaturally infects a variety of animal hosts and constitutes an excellent model to studyBordetellapathogenesis. Using in vitro coculture models of bacteria and human lung epithelial cells, we studied the effects ofB. bronchisepticaflagellin on host defense responses. Our results show thatB. bronchisepticaflagellin is a potent proinflammatory factor that induces chemokine, cytokine, and host defense gene expression. Furthermore, we investigated receptor specificity in the response toB. bronchisepticaflagellin. Our results show thatB. bronchisepticaflagellin is able to signal effectively through both human and mouse Toll-like receptor 5.
Coordinate Expression of Fimbriae in Uropathogenic
Escherichia coli
Authors: Snyder Jennifer A. , Haugen Brian J. , Lockatell C. Virginia , Maroncle Nathalie , Hagan Erin C. , Johnson David E. , Welch Rodney A. , Mobley Harry L. T. 
Published: October 2005

ABSTRACT

Uropathogenic
Escherichia coli
is the most common etiological agent of urinary tract infections. Bacteria can often express multiple adhesins during infection in order to favor attachment to specific niches within the urinary tract. We have recently demonstrated that type 1 fimbria, a phase-variable virulence factor involved in adherence, was the most highly expressed adhesin during urinary tract infection. Here, we examine whether the expression of type 1 fimbriae can affect the expression of other adhesins. Type 1 fimbrial phase-locked mutants of
E. coli
strain CFT073, which harbors genes for numerous adhesins, were employed in this study. CFT073-specific DNA microarray analysis of these strains demonstrates that the expression of type 1 fimbriae coordinately affects the expression of P fimbriae in an inverse manner. This represents evidence for direct communication between genes relating to pathogenesis, perhaps to aid the sequential occupation of different urinary tract tissues. While the role of type 1 fimbriae during infection has been clear, the role of P fimbriae must be further defined to assert the relevance of coordinated regulation in vivo. Therefore, we examined the ability of P fimbrial isogenic mutants, constructed in a type 1 fimbrial-negative background, to compete in the murine urinary tract over a period of 168 h. No differences in the colonization of these mutants were observed. However, comparison of these results with previous studies suggests that inversely coordinated expression of adhesin gene clusters does occur in vivo. Interestingly, the mutant that was incapable of expressing either type 1 or P fimbriae compensated by synthesizing F1C fimbriae.
Regulation of RANTES Promoter Activation in Gastric Epithelial Cells Infected withHelicobacter pylori
Authors: Kudo Takahiko , Lu Hong , Wu Jeng Yih , Graham David Y. , Casola Antonella , Yamaoka Yoshio 
Published: October 2005

ABSTRACTRANTES, a CC chemokine, plays an important role in the inflammatory response associated withHelicobacter pyloriinfection. However, the mechanism by whichH. pyloriinduces RANTES expression in the gastric mucosa is unknown. We cocultured gastric epithelial cells with wild-typeH. pylori, isogenicoipAmutants,cagpathogenicity island (PAI) mutants, or double knockout mutants. Reverse transcriptase PCR showed that RANTES mRNA was induced byH. pyloriand that the expression was both OipA andcagPAI dependent. Luciferase reporter gene assays and electrophoretic mobility shift assays showed that maximalH. pylori-inducedRANTESgene transcription required the presence of the interferon-stimulated responsive element (ISRE), the cyclic AMP-responsive element (CRE), nuclear factor-interleukin 6 (NF-IL-6), and two NF-κB sites. OipA- andcagPAI-dependent pathways included NF-κB→NF-κB/NF-IL-6/ISRE pathways, andcagPAI-dependent pathways additionally included Jun N-terminal kinase→CRE/NF-κB pathways. The OipA-dependent pathways additionally included p38→CRE/ISRE pathways. We confirmed the in vitro effects in vivo by examining RANTES mRNA levels in biopsy specimens from human gastric antral mucosa. RANTES mRNA levels in the antral mucosa were significantly higher for patients infected withcagPAI/OipA-positiveH. pylorithan for those infected withcagPAI/OipA-negativeH. pylorior uninfected patients. The mucosal inflammatory response toH. pyloriinfection involves different signaling pathways for activation of the RANTES promoter, with both OipA and thecagPAI being required for full activation of the RANTES promoter.
Interleukin-4 (IL-4) and IL-10 Collude in Vaccine Failure for Novel Exacerbatory Antigens in Murine
Leishmania major
Infection
Authors: Roberts Mark T. M. , Stober Carmel B. , McKenzie Andrew N , Blackwell Jenefer M. 
Published: October 2005

ABSTRACT

Leishmaniasis affects 12 million people but there are no vaccines in routine use. Recently, we used DNA vaccination in a susceptible BALB/c high-dose model of infection to screen 100 novel
Leishmania major
genes as vaccine candidates. In addition to finding novel protective antigens, we identified several antigens that reproducibly exacerbated disease. Here we examined the immune response to two of these antigens, lmd29 and 584C, that were originally identified in an expressed sequence tag cDNA sequencing project. We show that, in addition to exacerbating disease in susceptible BALB/c mice, these antigens retain a propensity to exacerbate disease in resistant C57BL/6 mice. This ability to exacerbate disease was lost when susceptible BALB/c mice were rendered resistant by disruption of the genes encoding interleukin-4 (IL-4) alone, IL-4/IL-13, or IL-4, IL-5, IL-9, and IL-13. Failure to exacerbate disease was associated with reduced IL-5 and IL-10 production in IL-4 knockout mice. Treatment of lmd29-vaccinated mice with anti-IL-10 receptor antibody prior to challenge infection converted exacerbation in wild-type BALB/c mice into highly significant antigen-specific protection. These studies demonstrate that some highly immunogenic antigens of
L. major
, while having an intrinsic capacity to exacerbate disease in the context of otherwise T helper 1-promoting DNA vaccine delivery, can be rendered protective by the removal of functional IL-10.
Effects of
Anaplasma phagocytophilum
on Host Cell Ferritin mRNA and Protein Levels
Authors: Carlyon Jason A. , Ryan Dara , Archer Kristina , Fikrig Erol 
Published: October 2005

ABSTRACT

Ferritin is a major intracellular iron storage protein and also functions as a cytoprotectant by sequestering iron to minimize the formation of reactive oxygen species.
Anaplasma phagocytophilum
, the causative agent of human granulocytic anaplasmosis, is an obligate intracellular bacterium that colonizes neutrophils. We have previously reported that human promyelocytic HL-60 cells infected with
A. phagocytophilum
demonstrate increased transcription of ferritin heavy chain and also that the bacterium stimulates neutrophil NADPH oxidase assembly and degranulation during the initial hours of infection (J. A. Carlyon, W. T. Chan, J. Galan, D. Roos, and E. Fikrig, J. Immunol.
169:
7009-7018, 2002, and J. A. Carlyon, D. Abdel-Latif, M. Pypaert, P. Lacy, and E. Fikrig, Infect. Immun. 72:4772-4783, 2004). In this study, we assessed ferritin mRNA and protein levels during
A. phagocytophilum
infection in vitro using HL-60 cells and neutrophils and in vivo using neutrophils from infected mice. The addition of
A. phagocytophilum
, as well as
Escherichia coli
and serum-opsonized zymosan, to neutrophils results in a pronounced increase in ferritin light-chain transcription and a concomitant rise in ferritin protein levels. Neutrophils from
A. phagocytophilum
-infected mice demonstrate elevated ferritin heavy-chain mRNA expression, a phenomenon consistent with infections by intracellular pathogens. Notably, ferritin protein levels of infected HL-60 cells were markedly diminished in a dose- and time-dependent manner. These studies provide insight into the effects
A. phagocytophilum
has on the ferritin levels of its host cell.
Apical Spore Phagocytosis Is Not a Significant Route of Infection of Differentiated Enterocytes by
Encephalitozoon intestinalis
Authors: Leitch Gordon J. , Ward Tarsha L. , Shaw Andrew P. , Newman Gale 
Published: October 2005

ABSTRACT

Encephalitozoon intestinalis
is a microsporidian species that infects the intestinal mucosal epithelium, primarily in immunodeficient individuals. The present study employed undifferentiated and differentiated human colonic carcinoma cell lines to determine if this parasite species infected polarized epithelial cells by spore phagocytosis or by impalement with the deployed spore polar tube. Apical surface spore attachment differed between cell lines such that SW480>HT-29>Caco-2>HCT-8, with attachment being greater to undifferentiated Caco-2 cells than differentiated cells and greater to partially differentiated HCT-8 cells than differentiated HCT-8 cells. Attachment was inhibited by chondroitin sulfate A, suggesting that it was mediated by host cell sulfated glycoaminoglycans. Infection rates 3 days postinfection paralleled spore attachment in the various cell lines. The undifferentiated cell line SW480 and undifferentiated Caco-2 and HCT-8 cells exhibited modest spore phagocytosis while the more differentiated cell line HT29 and differentiated Caco-2 and HCT-8 cells did not. All cell lines were impaled by the polar tubes of germinating spores. When normalized to the number of spores attached to the apical membrane, such impalement was greatest in the more differentiated Caco-2 and HCT-8 cells. The host cell apical surface influenced parasite spore germination, as in populations of large undifferentiated Caco-2 cells to which >3 spores had attached, the frequency distribution of the percentages of spores germinated per cell was bimodal, indicating that the surface of some cells favored germination, while others did not. This study suggests that phagocytosis is not a biologically significant mode of infection in differentiated intestinal epithelial cells.
Host and Bacterial Factors Contributing to the Clearance of Colonization byStreptococcus pneumoniaein a Murine Model
Authors: van Rossum Annemarie M. C. , Lysenko Elena S. , Weiser Jeffrey N. 
Published: October 2005

ABSTRACTNasopharyngeal colonization is the first step in the interaction betweenStreptococcus pneumoniae(the pneumococcus) and its human host. Factors that contribute to clearance of colonization are likely to affect the spread of the pneumococcus and the rate of pneumococcal disease in the population. To identify host and bacterial factors contributing to this process, we examined the time course of colonization using genetically modified mice and pneumococci. Severe combined immunodeficient mice remained persistently colonized (>6 weeks). Major histocompatibility complex II-deficient mice, but not μMT mice, were unable to clear colonization and showed a diminished T helper 1 response. Thus, CD4+T cells, rather than the generation of specific antibody, appear to be required for effective Th1-mediated clearance. In addition, the microbial pattern recognition receptor toll-like receptor 2 (TLR2), but not TLR4, was necessary for efficient clearance of colonization. In contrast, no role of complement component 3, inducible nitric oxide synthetase, interleukin 12 (IL-12), or IL-4 could be demonstrated. Expression of the pneumococcal toxin pneumolysin enhanced acute localized inflammatory responses and promoted clearance of colonization in a TLR4-independent manner. We conclude that both innate and CD4+T-cell-mediated immunity and proinflammatory bacterial factors, rather than a humoral adaptive immune response, are important for clearance ofS. pneumoniaefrom the murine nasopharynx.
Redundant Roles for Nucleocapsid and Matrix RNA-Binding Sequences in Human Immunodeficiency Virus Type 1 Assembly
Authors: Ott David E. , Coren Lori V. , Gagliardi Tracy D. 
Published: October 2005

ABSTRACT

RNA appears to be required for the assembly of retroviruses. This is likely due to binding of RNA by multiple Gags, which in turn organizes and stabilizes the Gag-Gag interactions that form the virion. While the nucleocapsid (NC) domain is the most conspicuous RNA-binding region of the human immunodeficiency virus type 1 (HIV-1) Gag polyprotein, we have previously shown that NC is not strictly required for efficient particle production. To determine if an RNA requirement for HIV-1 assembly exists, we analyzed virions produced by an NC deletion mutant for the presence of RNA. The results revealed that virions without NC still contained significant amounts of RNA. Since these packaged RNAs are probably incorporated by other RNA-binding sequences in Gag, an RNA-binding site in the matrix protein (MA) of Gag was mutated. While this mutation did not interfere with HIV-1 replication, a construct with both MA and NC mutations (MX/NX) failed to produce particles. The MX/NX mutant was rescued in
trans
by coassembly with several forms of Gag: wild-type Gag, either of the single-mutant Gags, or Gag truncations that contain MA or NC sequences. Addition of basic sequences to the MX/NX mutant partially restored particle production, consistent with a requirement for Gag-RNA binding in addition to Gag-Gag interactions. Together, these results support an RNA-binding requirement for Gag assembly, which relies on binding of RNA by MA or NC sequences to condense, organize, and stabilize the HIV-1 Gag-Gag interactions that form the virion.
Assembly of Severe Acute Respiratory Syndrome Coronavirus RNA Packaging Signal into Virus-Like Particles Is Nucleocapsid Dependent
Authors: Hsieh Ping-Kun , Chang Shin C. , Huang Chu-Chun , Lee Ting-Ting , Hsiao Ching-Wen , Kou Yi-Hen , Chen I-Yin , Chang Chung-Ke , Huang Tai-Huang , Chang Ming-Fu 
Published: October 2005

ABSTRACT

The severe acute respiratory syndrome coronavirus (SARS-CoV) was recently identified as the etiology of SARS. The virus particle consists of four structural proteins: spike (S), small envelope (E), membrane (M), and nucleocapsid (N). Recognition of a specific sequence, termed the packaging signal (PS), by a virus N protein is often the first step in the assembly of viral RNA, but the molecular mechanisms involved in the assembly of SARS-CoV RNA are not clear. In this study, Vero E6 cells were cotransfected with plasmids encoding the four structural proteins of SARS-CoV. This generated virus-like particles (VLPs) of SARS-CoV that can be partially purified on a discontinuous sucrose gradient from the culture medium. The VLPs bearing all four of the structural proteins have a density of about 1.132 g/cm
3
. Western blot analysis of the culture medium from transfection experiments revealed that both E and M expressed alone could be released in sedimentable particles and that E and M proteins are likely to form VLPs when they are coexpressed. To examine the assembly of the viral genomic RNA, a plasmid representing the GFP-PS580 cDNA fragment encompassing the viral genomic RNA from nucleotides 19715 to 20294 inserted into the 3′ noncoding region of the green fluorescent protein (GFP) gene was constructed and applied to the cotransfection experiments with the four structural proteins. The SARS-CoV VLPs thus produced were designated VLP(GFP-PS580). Expression of GFP was detected in Vero E6 cells infected with the VLP(GFP-PS580), indicating that GFP-PS580 RNA can be assembled into the VLPs. Nevertheless, when Vero E6 cells were infected with VLPs produced in the absence of the viral N protein, no green fluorescence was visualized. These results indicate that N protein has an essential role in the packaging of SARS-CoV RNA. A filter binding assay and competition analysis further demonstrated that the N-terminal and C-terminal regions of the SARS-CoV N protein each contain a binding activity specific to the viral RNA. Deletions that presumably disrupt the structure of the N-terminal domain diminished its RNA-binding activity. The GFP-PS-containing SARS-CoV VLPs are powerful tools for investigating the tissue tropism and pathogenesis of SARS-CoV.
Kinetic Analyses of the Surface-Transmembrane Disulfide Bond Isomerization-Controlled Fusion Activation Pathway in Moloney Murine Leukemia Virus
Authors: Wallin Michael , Löving Robin , Ekström Maria , Li Kejun , Garoff Henrik 
Published: October 2005

ABSTRACT

The surface (SU) and transmembrane (TM) subunits of Moloney murine leukemia virus (Mo-MLV) Env are disulfide linked. The linking cysteine in SU is part of a conserved CXXC motif in which the other cysteine carries a free thiol. Recently, we showed that receptor binding activates its free thiol to isomerize the intersubunit disulfide bond into a disulfide within the motif instead (M. Wallin, M. Ekström and H. Garoff, EMBO J.
23:
54-65, 2004). This facilitated SU dissociation and activation of TM for membrane fusion. The evidence was mainly based on the finding that alkylation of the CXXC-thiol prevented isomerization. This arrested membrane fusion, but the activity could be rescued by cleaving the intersubunit disulfide bond with dithiothreitol (DTT). Here, we demonstrate directly that receptor binding causes SU-TM disulfide bond isomerization in a subfraction of the viral Envs. The kinetics of the isomerization followed that of virus-cell membrane fusion. Arresting the fusion with lysophosphatidylcholine did not arrest isomerization, suggesting that isomerization precedes the hemifusion stage of fusion. Our earlier finding that native Env was not possible to alkylate but required isomerization induction by receptor binding intimated that alkylation trapped an intermediate form of Env. To further clarify this possibility, we analyzed the kinetics by which the alkylation-sensitive Env was generated during fusion. We found that it followed the fusion kinetics. In contrast, the release of fusion from alkylated, isomerization-blocked virus by DTT reduction of the SU-TM disulfide bond was much faster. These results suggest that the alkylation-sensitive form of Env is a true intermediate in the fusion activation pathway of Env.
Transcriptional Regulation of Early Transposon Elements, an Active Family of Mouse Long Terminal Repeat Retrotransposons
Authors: Maksakova Irina A. , Mager Dixie L. 
Published: October 2005

ABSTRACT
While early transposon (ETn) endogenous retrovirus (ERV)-like elements are known to be active insertional mutagens in the mouse, little is known about their transcriptional regulation. ETns are transcribed during early mouse embryogenesis in embryonic stem (ES) and embryonic carcinoma (EC) cell lines. Despite their lack of coding potential, some ETns remain transposition competent through their use of reverse transcriptase encoded by a related group of ERVs—MusD elements. In this study, we have confirmed high expression levels of ETn and MusD elements in ES and EC cells and have demonstrated an increase in the copy number of ETnII elements in the EC P19 cell line. Using transient transfections, we have shown that ETnII and MusD LTRs are much more active as promoters in P19 cells than in NIH 3T3 cells, indicating that genomic context and methylation are not the only factors determining endogenous transcriptional activity of ETns. Three sites in the 5′ part of the long terminal repeat (LTR) were demonstrated to bind Sp1 and Sp3 transcription factors and were found to be important for high LTR promoter activity in P19 cells, suggesting that as yet unidentified Sp binding partners are involved in the regulation of ETn activity in undifferentiated cells. Finally, we found multiple transcription start sites within the ETn LTR and have shown that the LTR retains significant promoter activity in the absence of its noncanonical TATA box. These findings lend insight into the transcriptional regulation of this family of mobile mouse retrotransposons.
Stress-Activated Protein Kinases Are Involved in Coxsackievirus B3 Viral Progeny Release
Authors: Si Xiaoning , Luo Honglin , Morgan Andrew , Zhang Jingchun , Wong Jerry , Yuan Ji , Esfandiarei Mitra , Gao Guang , Cheung Caroline , McManus Bruce M. 
Published: October 2005

ABSTRACT
Stress-activated protein kinases (SAPKs), consisting of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK), are activated upon various environmental stimuli, including viral infections. Cellular survival and death signaling events following coxsackievirus B3 (CVB3) infection have been studied in relationship to viral replication, but the role of SAPKs has not been scrutinized. In this study, we found that the phosphorylation of JNK1/2 and p38 MAPK was increased during active replication of CVB3 and that their phosphorylation was independent of CVB3-induced caspase activation or production of reactive oxygen species. The roles of these kinases in CVB3 infection were further evaluated using specific inhibitors: SP600125 for JNK1/2 and SB203580 for p38 MAPK. JNK1/2 inhibitors reduced CVB3-induced phosphorylation of activating transcription factor 2, and the p38 MAPK inhibitor reduced CVB3-induced phosphorylation of heat shock protein 27. Although inhibition of these kinases by specific inhibitors did not affect CVB3 viral protein synthesis, inhibition of p38 MAPK but not of JNK1/2 resulted in significant reduction of viral progeny release, suppression of CVB3-induced cell death, and blockage of CVB3-induced caspase-3 activation in infected cells. We conclude that SAPK pathways play critical roles in the life cycle of CVB3, particularly in viral progeny release.