bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analyses of Five Gallinacin Genes and the
Salmonella enterica
Serovar Enteritidis Response in Poultry
Authors: Hasenstein Jason R. , Zhang Guolong , Lamont Susan J. 
Published: May 2006

ABSTRACT

Gallinacins in poultry are functional equivalents of mammalian beta-defensins, which constitute an integral component of the innate immune system.
Salmonella enterica
serovar Enteritidis is a gram-negative bacterium that negatively affects both human and animal health. To analyze the association of genetic variations of the gallinacin genes with the phenotypic response to
S. enterica
serovar Enteritidis, an F
1
population of chickens was created by crossing four outbred broiler sires to dams of two highly inbred lines. The F
1
chicks were evaluated for bacterial colonization after pathogenic
S. enterica
serovar Enteritidis inoculation and for circulating antibody levels after inoculation with
S. enterica
serovar Enteritidis bacterin vaccine. Five candidate genes were studied, including gallinacins 2, 3, 4, 5, and 7. Gene fragments were sequenced from the founder individuals of the resource population, and a mean of 13.2 single-nucleotide polymorphisms (SNP) per kilobase was identified. One allele-defining SNP per gene was utilized to test for statistical associations of sire alleles with progeny response to
S. enterica
serovar Enteritidis. Among the five gallinacin genes evaluated, the
Gal3
and
Gal7
SNPs in broiler sires were found to be associated with antibody production after
S. enterica
serovar Enteritidis vaccination. Utilization of these SNPs as molecular markers for the response to
S. enterica
serovar Enteritidis may result in the enhancement of the immune response in poultry.
Infectivity of the Highly Transformable BBE02−lp56−Mutant ofBorrelia burgdorferi, the Lyme Disease Spirochete, via Ticks
Authors: Jacobs Mary B. , Norris Steven J. , Phillippi-Falkenstein Kathrine M. , Philipp Mario T. 
Published: May 2006

ABSTRACTInfectiousBorrelia burgdorferistrains that have increased transformability with the shuttle vector pBSV2 were recently constructed by inactivating the gene encoding BBE02, a putative restriction-modification gene product expressed by the linear plasmid lp25 (Kawabata et al., Infect. Immun. 72:7147-7154, 2004). The absence of the linear plasmid lp56, which carries another putative restriction-modification gene, further enhanced transformation rates. The infectivity of these mutants was assessed previously in mice that were inoculated with needle and syringe and was found to be equivalent to that of wild-type spirochetes. Here we examined the infectivity of spirochetes to ticks after capillary inoculation ofIxodes scapularisnymphs and the subsequent spirochetal infectivity to mice via ticks by usingB. burgdorferiB31 clonal isolates lacking lp56 and/or BBE02. The absence of lp56 (but not BBE02) correlated with a lower number of spirochetes in ticks after feeding on mice; this plasmid thus may play a role, albeit not an essential one, in supporting spirochetal survival in the feeding tick. Importantly, however, the absence of lp56 and BBE02 did not detectably influence infectivity to mice via ticks.
Transcriptional Induction of the
Pseudomonas aeruginosa
Type III Secretion System by Low Ca
2+
and Host Cell Contact Proceeds through Two Distinct Signaling Pathways
Authors: Dasgupta Nandini , Ashare Alix , Hunninghake Gary W. , Yahr Timothy L. 
Published: May 2006

ABSTRACT

The opportunistic pathogen
Pseudomonas aeruginosa
utilizes a type III secretion system (T3SS) to intoxicate eukaryotic host cells. Transcription of the T3SS is induced under calcium-limited growth conditions or following intimate contact of
P. aeruginosa
with host cells. In the present study, we demonstrate that expression of the T3SS is controlled by two distinct regulatory mechanisms and that these mechanisms are differentially activated in a host cell-dependent manner. The first mechanism is dependent upon ExsC, a regulatory protein that couples transcription of the T3SS to the activity of the type III secretion machinery. ExsC is essential for induction of the T3SS under low-calcium-growth conditions and for T3SS-dependent cytotoxicity towards social amoebae, insect cells, and erythrocytes. The second regulatory mechanism functions independently of ExsC and is sufficient to elicit T3SS-dependent cytotoxicity towards certain types of mammalian cells. Although this second pathway (ExsC independent) is sufficient, an
exsC
mutant demonstrates a lag in the induction of cytotoxicity towards Chinese hamster ovary cells and is attenuated for virulence in a mouse pneumonia model. We propose that the ExsC-dependent pathway is required for full cytotoxicity towards all host cell types tested whereas the ExsC-independent pathway may represent an adaptation that allows
P. aeruginosa
to increase expression of the T3SS in response to specific types of mammalian cells.
MyD88-Dependent Signaling Affects the Development of Meningococcal Sepsis by Nonlipooligosaccharide Ligands
Authors: Plant Laura , Wan Hong , Jonsson Ann-Beth 
Published: May 2006

ABSTRACTThe Toll-like receptors (TLRs) and the adaptor myeloid differentiation factor 88 (MyD88) are important in the innate immune defenses of the host to microbial infections. Meningococcal ligands signaling via TLRs control inflammatory responses, and stimulation can result in fulminant meningococcal sepsis. In this study, we show that the responses to nonlipooligosaccharide (non-LOS) ligands of meningococci are MyD88 dependent. An isogenic LOS-deficient mutant of the serogroup C meningococcal strain FAM20 caused fatal disease in wild type C57BL/6 mice that was not observed in MyD88−/−mice. Fatality correlated with high proinflammatory cytokine and C5a levels in serum, high neutrophil numbers in blood, and increased bacteremia at 24 h postinfection in the wild-type mice. Infection with the parent strain FAM20 resulted in fatality in 100% of the wild-type mice and 50% of the MyD88−/−mice. We conclude that both LOS and another neisserial ligand cause meningococcal sepsis in an in vivo mouse model and confirm that meningococcal LOS can act via both the MyD88- dependent and -independent pathways, while the non-LOS meningococcal ligand(s) acts only via the MyD88-dependent pathway.
Delineating the Requirement for theBorrelia burgdorferiVirulence Factor OspC in the Mammalian Host
Authors: Stewart Philip E. , Wang Xiaohui , Bueschel Dawn M. , Clifton Dawn R. , Grimm Dorothee , Tilly Kit , Carroll James A. , Weis Janis J. , Rosa Patricia A. 
Published: May 2006

ABSTRACTWe previously demonstrated that outer surface protein C (OspC) ofBorrelia burgdorferiis essential for establishing mammalian infection. However, the role of OspC in mammalian infection is unknown. Here, we report experiments designed to distinguish between two models of OspC function in the mammalian host: (i) OspC fulfills an essential physiological role for growth and host adaptation or (ii) OspC provides a protective role for evasion of components of the innate immune response. We found that aB. burgdorferi ospCmutant, previously demonstrated to be noninfectious in both immunocompetent and SCID mice, could survive in the relatively immune-privileged environment of dialysis membrane chambers implanted within the peritoneum of a rat. TheospCmutant also adapts to the mammalian environment, as determined by the protein profiles of the chamber-cultivated spirochetes. Therefore, OspC does not appear to provide a physiological function for the survival ofB. burgdorferiwithin the mammalian host. The second model, evasion of the innate immune system, was tested by assessing the infectivity of theospCmutant in mice deficient for myeloid differentiation protein 88 (MyD88). Recent studies have shown thatB. burgdorferiis prevented from reaching high cell numbers in the mammalian host by MyD88-dependent signaling pathways. TheospCmutant was incapable of infecting MyD88-deficient mice, suggesting that the role of OspC cannot be related solely to evasion of MyD88-mediated innate immunity. These results reiterate the importance of OspC in mammalian infection and eliminate simple models of function for this enigmatic protein.
Bile Acids Enhance Invasiveness of
Cryptosporidium
spp. into Cultured Cells
Authors: Feng Hanping , Nie Weijia , Sheoran Abhineet , Zhang Quanshun , Tzipori Saul 
Published: May 2006

ABSTRACT

Bile salts such as sodium taurocholate (NaTC) are routinely used to induce the excystation of
Cryptosporidium
oocysts. Here we show that NaTC significantly enhanced the invasion of several cultured cell lines by freshly excysted
Cryptosporidium parvum
and
Cryptosporidium hominis
sporozoites. A variety of purified bile salts or total bile from bovine also enhanced the invasion of cultured cells by
C. parvum
. Further studies demonstrated that NaTC increased protein secretion and gliding motility of sporozoites, the key processes for successful invasion. These observations may lead to improved
Cryptosporidium
infectivity of cultured cells and help future studies on the host-parasite interaction.
Gamma Interferon, Tumor Necrosis Factor Alpha, and Nitric Oxide Synthase 2, Key Elements of Cellular Immunity, Perform Critical Protective Functions during Humoral Defense against Lethal PulmonaryYersinia pestisInfection
Authors: Parent Michelle A. , Wilhelm Lindsey B. , Kummer Lawrence W. , Szaba Frank M. , Mullarky Isis K. , Smiley Stephen T. 
Published: May 2006

ABSTRACTPulmonary infection byYersinia pestiscauses pneumonic plague, a rapidly progressing and often fatal disease. To aid the development of safe and effective pneumonic plague vaccines, we are deciphering mechanisms used by the immune system to protect against lethal pulmonaryY. pestisinfection. In murine pneumonic plague models, passive transfer of convalescent-phase sera confers protection, as does active vaccination with liveY. pestis. Here, we demonstrate that protection by either protocol relies upon both gamma interferon (IFN-γ) and tumor necrosis factor alpha (TNF-α) cytokines classically associated with type 1 cellular immunity. In both protocols, abrogating IFN-γ or TNF-α activity significantly decreases survival and increases the bacterial burden in pulmonary, splenic, and hepatic tissues. Neutralization of either cytokine also counteracts challenge-induced, vaccination-dependent upregulation of nitric oxide synthase 2 (NOS2). Moreover, genetic depletion of NOS2 suppresses protection conferred by serotherapy. We conclude that IFN-γ, TNF-α, and NOS2, key elements of cellular immunity, perform critical protective functions during humoral defense against lethal pulmonaryY. pestischallenge. These observations strongly suggest that plague vaccines should strive to maximally prime both cellular and humoral immunity.
Identification of
Staphylococcus aureus
Proteins Recognized by the Antibody-Mediated Immune Response to a Biofilm Infection
Authors: Brady Rebecca A. , Leid Jeff G. , Camper Anne K. , Costerton J. William , Shirtliff Mark E. 
Published: May 2006

ABSTRACT

Staphylococcus aureus
causes persistent, recurrent infections (e.g., osteomyelitis) by forming biofilms. To survey the antibody-mediated immune response and identify those proteins that are immunogenic in an
S. aureus
biofilm infection, the tibias of rabbits were infected with methicillin-resistant
S. aureus
to produce chronic osteomyelitis. Sera were collected prior to infection and at 14, 28, and 42 days postinfection. The sera were used to perform Western blot assays on total protein from biofilm grown in vitro and separated by two-dimensional gel electrophoresis. Those proteins recognized by host antibodies in the harvested sera were identified via matrix-assisted laser desorption ionization-time of flight analysis. Using protein from mechanically disrupted total and fractionated biofilm protein samples, we identified 26 and 22 immunogens, respectively. These included a cell surface-associated β-lactamase, lipoprotein, lipase, autolysin, and an ABC transporter lipoprotein. Studies were also performed using microarray analyses and confirmed the biofilm-specific up-regulation of most of these genes. Therefore, although the biofilm antigens are recognized by the immune system, the biofilm infection can persist. However, these proteins, when delivered as vaccines, may be important in directing the immune system toward an early and effective antibody-mediated response to prevent chronic
S. aureus
infections. Previous works have identified
S. aureus
proteins that are immunogenic during acute infections, such as sepsis. However, this is the first work to identify these immunogens during chronic
S. aureus
biofilm infections and to simultaneously show the global relationship between the antigens expressed during an in vivo infection and the corresponding in vitro transcriptomic and proteomic gene expression levels.
Biogenesis of the
Actinobacillus actinomycetemcomitans
Cytolethal Distending Toxin Holotoxin
Authors: Ueno Yoko , Ohara Masaru , Kawamoto Toru , Fujiwara Tamaki , Komatsuzawa Hitoshi , Oswald Eric , Sugai Motoyuki 
Published: May 2006

ABSTRACT

The cell cycle G
2
/M specific inhibitor cytolethal distending toxin (CDT) from
Actinobacillus actinomycetemcomitans
is composed of CdtA, CdtB, and CdtC coded on the
cdtA
,
cdtB
, and
cdtC
genes that are tandem on the chromosomal
cdt
locus.
A. actinomycetemcomitans
CdtA has the lipid binding consensus domain, the so-called “lipobox”, at the N-terminal signal sequence. Using
Escherichia coli
carrying plasmid pTK3022, we show that the 16th residue, cysteine, of CdtA bound [
3
H]palmitate or [
3
H]glycerol. Further, posttranslational processing of the signal peptide, CdtA, was inhibited using globomycin, an inhibitor of lipoprotein-specific signal peptidase II. Fractionation and immunoblotting show the lipid-modified CdtA is present in the outer membrane. Immunoprecipitation and the pull-down assay of the CDT complex from
E. coli
carrying a plasmid containing
cdtABC
demonstrated that the CDT complex in the periplasm is composed of CdtA, CdtB, and CdtC and that the CDT complex in culture supernatant is an N-terminally truncated (36 to 43 amino acids) form of CdtA (CdtA′), CdtB, and CdtC. This suggests that CDT is present as a complex both in the periplasm and the supernatant where CdtA undergoes posttranslation processing to CdtA′ in the process of biogenesis and secretion of CDT holotoxin into the culture supernatant. Site-directed mutagenesis of the 16th cysteine residue to glycine in CdtA altered localization of CdtA in the cell and reduced the amount of CDT activity in the culture supernatant. This suggests that CDT forms a complex inside the periplasm for lipid modification where posttranslational processing of CdtA plays an important role for the efficient production of CDT holotoxin into the culture supernatant.
Identification ofBurkholderia pseudomalleiGenes Required for the Intracellular Life Cycle and In Vivo Virulence
Authors: Pilatz Sabine , Breitbach Katrin , Hein Nadine , Fehlhaber Beate , Schulze Jessika , Brenneke Birgit , Eberl Leo , Steinmetz Ivo 
Published: May 2006

ABSTRACTThe bacterial pathogenBurkholderia pseudomalleiinvades host cells, escapes from endocytic vesicles, multiplies intracellularly, and induces the formation of actin tails and membrane protrusions, leading to direct cell-to-cell spreading. This study was aimed at the identification ofB. pseudomalleigenes responsible for the different steps of this intracellular life cycle.B. pseudomalleitransposon mutants were screened for a reduced ability to form plaques on PtK2 cell monolayers as a result of reduced intercellular spreading. Nine plaque assay mutants with insertions in different open reading frames were selected for further studies. One mutant defective in a hypothetical protein encoded within the Bsa type III secretion system gene cluster was found to be unable to escape from endocytic vesicles after invasion but still multiplied within the vacuoles. Another mutant with a defect in a putative exported protein reached the cytoplasm but exhibited impaired actin tail formation in addition to a severe intracellular growth defect. In four mutants, the transposon had inserted into genes involved in either purine, histidine, orp-aminobenzoate biosynthesis, suggesting that these pathways are essential for intracellular growth. Three mutants with reduced plaque formation were shown to have gene defects in a putative cytidyltransferase, a putative lipoate-protein ligase B, and a hypothetical protein. All nine mutants proved to be significantly attenuated in a murine model of infection, with some mutants being essentially avirulent. In conclusion, we have identified a number of novel majorB. pseudomalleivirulence genes which are essential for the intracellular life cycle of this pathogen.
Significance of Heat-Stable and Heat-Labile Enterotoxins in Porcine Colibacillosis in an Additive Model for Pathogenicity Studies
Authors: Zhang Weiping , Berberov Emil M. , Freeling Jessica , He D. , Moxley Rodney A. , Francis David H. 
Published: May 2006

ABSTRACTAlthough heat-stable (ST) and heat-labile (LT) enterotoxins produced by enterotoxigenicEscherichia coli(ETEC) have been documented as important factors associated with diarrheal diseases, investigations assessing the contributions of individual enterotoxins to the pathogenesis ofE. coliinfection have been limited. To address the individual roles of enterotoxins in the diarrheal disease caused by K88-positive ETEC in young pigs, enterotoxin-positive and -negative isogenicE. colistrains were constructed by using pBR322 to clone and express LT and STb. Four strains, K88+astA, K88+astA/pBR322, K88+astASTb+, and K88+astALT+, were constructed and subsequently included in gnotobiotic piglet challenge studies, and their pathogenesis was assessed. The results indicated that all K88+isogenic strains were able to colonize the small intestines of piglets exhibiting the K88 receptor. However, only LT- and STb-positive strains caused appreciable diarrhea. Piglets inoculated with the K88+astALT+strain became dehydrated within 18 h, while those inoculated with the K88+astASTb+strain did not, although diarrhea developed in several piglets. The changes in the blood packed-cell volume and plasma total protein of gnotobiotic piglets inoculated with the LT-positive strains were significantly greater than those of pigs inoculated with the K88astA/pBR322 strain (P= 0.012,P= 0.002). Immunochemistry image analysis also suggested that LT enhanced bacterial colonization in a gnotobiotic piglet model. This investigation suggested that LT is a major contributor to the virulence of K88+ETEC and that isogenic constructs are a useful tool for studying the pathogenesis of ETEC infection.
Salmonella enterica
Serovar Typhimurium Requires the Lpf, Pef, and Tafi Fimbriae for Biofilm Formation on HEp-2 Tissue Culture Cells and Chicken Intestinal Epithelium
Authors: Ledeboer Nathan A. , Frye Jonathan G. , McClelland Michael , Jones Bradley D. 
Published: May 2006

ABSTRACT

Recent work has demonstrated that
Salmonella enterica
serovar Typhimurium forms biofilms on HEp-2 tissue culture cells in a type 1 fimbria-dependent manner. To investigate how biofilm growth of HEp-2 tissue culture cells affects gene expression in
Salmonella
, we compared global gene expression during planktonic growth and biofilm growth. Microarray results indicated that the transcription of ∼100 genes was substantially altered by growth in a biofilm. These genes encode proteins with a wide range of functions, including antibiotic resistance, central metabolism, conjugation, intracellular survival, membrane transport, regulation, and fimbrial biosynthesis. The identification of five fimbrial gene clusters was of particular interest, as we have demonstrated that type 1 fimbriae are required for biofilm formation on HEp-2 cells and murine intestinal epithelium. Mutations in each of these fimbriae were constructed in
S. enterica
serovar Typhimurium strain BJ2710, and the mutants were found to have various biofilm phenotypes on plastic, HEp-2 cells, and chicken intestinal tissue. The
pef
and
csg
mutants were defective for biofilm formation on each of the three surfaces tested, while the
lpf
mutant exhibited a complete loss of the ability to form a biofilm on chicken intestinal tissue but only an intermediate loss of the ability to form a biofilm on tissue culture cells and plastic surfaces. The
bcf
mutant displayed increased biofilm formation on both HEp-2 cells and chicken intestinal epithelium, while the
sth
mutant had no detectable biofilm defects. In all instances, the mutants could be restored to a wild-type phenotype by a plasmid carrying the functional genes. This is the first work to identify the genomic responses of
Salmonella
to biofilm formation on host cells, and this work highlights the importance of fimbriae in adhering to and adapting to a eukaryotic cell surface. An understanding of these interactions is likely to provide new insights for intervention strategies in
Salmonella
colonization and infection.
Variation in the Presence of Neuraminidase Genes among
Streptococcus pneumoniae
Isolates with Identical Sequence Types
Authors: Pettigrew Melinda M. , Fennie Kristopher P. , York Matthew P. , Daniels Janeen , Ghaffar Faryal 
Published: May 2006

ABSTRACT

Streptococcus pneumoniae
frequently colonizes the upper respiratory tract of young children and is an important cause of otitis media and invasive disease. Carriage is more common than disease, yet the genetic factors that predispose a given clone for disease are not known. The relationship between capsule type, genetic background, and virulence is complex, and important questions remain regarding how pneumococcal clones differ in their ability to cause disease. Pneumococcal neuraminidase cleaves sialic acid-containing substrates and is thought to be important for pneumococcal virulence. We describe the distribution of multilocus sequence types (ST), capsule type, and neuraminidase genes among 342 carriage, middle ear, blood, and cerebrospinal fluid (CSF) pneumococcal strains from young children. We found 149 STs among our
S. pneumoniae
isolates.
nanA
was present in all strains, while
nanB
and
nanC
were present in 96% and 51% of isolates, respectively. The distribution of
nanC
varied among the strain collections from different tissue sources (
P
= 0.03). The prevalence of
nanC
was 1.41 (95% confidence interval, 1.11, 1.79) times higher among CSF isolates than among carriage isolates. We identified isolates of the same ST that differed in the presence of
nanB
and
nanC
. These studies demonstrate that virulence determinants, other than capsule loci, vary among strains of identical ST. Our studies suggest that the presence of
nanC
may be important for tissue-specific virulence. Studies that both incorporate MLST and take into account additional virulence determinants will provide a greater understanding of the pneumococcal virulence potential.