bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dietary Iron Content Mediates Hookworm Pathogenesis In Vivo
Authors: Held Melissa R. , Bungiro Richard D. , Harrison Lisa M. , Hamza Iqbal , Cappello Michael 
Published: December 2005

ABSTRACT

Hookworm infection is associated with growth delay and iron deficiency anemia in developing countries. A series of experiments were designed in order to test the hypothesis that host dietary iron restriction mediates susceptibility to hookworm infection using the hamster model of
Ancylostoma ceylanicum
. Animals were maintained on diets containing either 10 ppm iron (iron restricted) or 200 ppm iron (standard/high iron), followed by infection with
A. ceylanicum
third-stage larvae. Infected animals fed the standard diet exhibited statistically significant growth delay and reduced blood hemoglobin levels compared to uninfected controls on day 20 postinfection. In contrast, no statistically significant differences in weight or hemoglobin concentration were observed between infected and uninfected animals fed the iron-restricted diet. Moreover, iron-restricted animals were observed to have reduced intestinal worm burdens on day 10 and day 20 postinfection compared to those of animals maintained on the standard/high-iron diet. In a subsequent study, animals equilibrated on diets containing a range of iron levels (10 ppm, 40 ppm, 100 ppm, or 200 ppm) were infected with
A. ceylanicum
and followed for evidence of hookworm disease. Infected animals from the intermediate-dietary iron (40- and 100-ppm) groups exhibited greater weight loss and anemia than those in the low (10-ppm)- or high (200-ppm)-iron diet groups. Mortality was also significantly higher in the intermediate-dietary-iron groups. These data suggest that severe dietary iron restriction impairs hookworm development in vivo but that moderate iron restriction enhances host susceptibility to severe disease.
Immunogenicity and Protection of a Recombinant Human Adenovirus Serotype 35-Based Malaria Vaccine againstPlasmodium yoeliiin Mice
Authors: Ophorst O. J. A. E. , Radošević K. , Havenga M. J. E. , Pau M. G. , Holterman L. , Berkhout B. , Goudsmit J. , Tsuji M. 
Published: December 2005

ABSTRACTGiven the promise of recombinant adenovirus type 5 (rAd5) as a malaria vaccine carrier in preclinical models, we evaluated the potency of rAd35 coding forPlasmodium yoeliicircumsporozoite protein (rAd35PyCS). We chose rAd35 since a survey with serum samples from African subjects demonstrated that human Ad35 has a much lower seroprevalence of 20% and a much lower geometric mean neutralizing antibody titer (GMT) of 48 compared to Ad5 (seroprevalence, 85%; GMT, 1,261) in countries with a high malaria incidence. We also demonstrated that immunization with rAd35PyCS induced a dose-dependent and potent, CS-specific CD8+cellular and humoral immune response and conferred significant inhibition (92 to 94%) of liver infection upon high-dose sporozoite challenge. Furthermore, we showed that in mice carrying neutralizing antibody activity against Ad5, mimicking a human situation, CS-specific T- and B-cell responses were significantly dampened after rAd5PyCS vaccination, resulting in loss of inhibition of liver infection upon sporozoite challenge. In contrast, rAd35 vaccine was as potent in naive mice as in Ad5-preimmunized mice. Finally, we showed that heterologous rAd35-rAd5 prime-boost regimens were more potent than rAd35-rAd35 because of induction of anti-Ad35 antibodies after rAd35 priming. The latter data provide a further rationale for developing rAd prime-boost regimens but indicate that priming and boosting Ad vectors must be immunologically distinct and also should be distinct from Ad5. Collectively, the data presented warrant further development of rAd35-based vaccines against human malaria.
Identification of Differentially Expressed Genes in Virulent and NonvirulentEntamoebaSpecies: Potential Implications for Amebic Pathogenesis
Authors: MacFarlane Ryan C. , Singh Upinder 
Published: December 2005

ABSTRACTEntamoeba histolyticais a protozoan parasite that causes colitis and liver abscesses. SeveralEntamoebaspecies and strains with differing levels of virulence have been identified.E. histolyticaHM-1:IMSS is a virulent strain,E. histolyticaRahman is a nonvirulent strain, andEntamoeba disparis a nonvirulent species. We used anE. histolyticaDNA microarray consisting of 2,110 genes to assess the transcriptional differences between these species/strains with the goal of identifying genes whose expression correlated with a virulence phenotype. We found 415 genes expressed at lower levels inE. disparand 32 genes with lower expression inE. histolyticaRahman than inE. histolyticaHM-1:IMSS. Overall, 29 genes had decreased expression in both the nonvirulent species/strains than the virulentE. histolyticaHM-1:IMSS. Interestingly, a number of genes with potential roles in stress response and virulence had decreased expression in either one or both nonvirulentEntamoebaspecies/strains. These included genes encoding Fe hydrogenase (9.m00419), peroxiredoxin (176.m00112), type A flavoprotein (6.m00467), lysozyme (6.m00454), sphingomyelinase C (29.m00231), and a hypothetical protein with homology to both aPlasmodiumsporozoite threonine-asparagine-rich protein (STARP) and a streptococcal hemagglutinin (238.m00054). The function of these genes inEntamoebaand their specific roles in parasite virulence need to be determined. We also found that a number of the non-long-terminal-repeat retrotransposons (EhLINEs andEhSINEs), which have been shown to modulate gene expression and genomic evolution, had lower expression in the nonvirulent species/strains than inE. histolyticaHM-1:IMSS. Our results, identifying expression profiles and patterns indicative of a virulence phenotype, may be useful in characterizing the transcriptional framework of virulence.
Human Recombinant Antimannan Immunoglobulin G1 Antibody Confers Resistance to Hematogenously Disseminated Candidiasis in Mice
Authors: Zhang Mason X. , Bohlman M. Charlotte , Itatani Carol , Burton Dennis R. , Parren Paul W. H. I. , St. Jeor Stephen C. , Kozel Thomas R. 
Published: December 2005

ABSTRACT

Mannan is a major cell wall component found in
Candida
species. Natural antimannan antibody is present in sera from most normal adults, but its role in host resistance to hematogenously disseminated candidiasis is unknown. The purpose of this study was to develop recombinant human antimannan antibody and to study its protective function. A phage Fab display combinatorial library containing Fab genes from bone marrow lymphocytes was screened with
Candida albicans
yeast cells and chemically purified mannan. One antimannan Fab, termed M1, was converted to a full-length immunoglobulin G1 antibody, M1g1, and M1g1 was produced in CHO cells. The M1g1 epitope was found in
C. albicans
serotypes A and B,
Candida tropicalis
,
Candida guilliermondii
,
Candida glabrata
, and
Candida parapsilosis
. Its expression was active at both 23°C and 37°C and uniform over the cell surface. BALB/c mice passively immunized with M1g1 were more resistant than control mice to a lethal hematogenous infection by
C. albicans
, as evidenced by extension of survival in an M1g1 dose-dependent manner (
P
, 0.08 to <0.001) and by reduction in number of infection foci and their size in the kidney. In vitro studies found that M1g1 promoted phagocytosis and phagocytic killing of
C. albicans
yeast cells by mouse peritoneal macrophages and was required for activation of the mouse complement cascade. Thus, human antimannan antibody may have a protective role in host resistance to systemic candidiasis.
Glyceraldehyde-3-Phosphate Dehydrogenase ofParacoccidioides brasiliensisIs a Cell Surface Protein Involved in Fungal Adhesion to Extracellular Matrix Proteins and Interaction with Cells
Authors: Barbosa Mônica Santiago , Báo Sônia Nair , Andreotti Patrícia Ferrari , de Faria Fabrícia P. , Felipe Maria Sueli S. , dos Santos Feitosa Luciano , Mendes-Giannini Maria José Soares , de Almeida Soares Célia Maria 
Published: December 2005

ABSTRACTThe pathogenic fungusParacoccidioides brasiliensiscauses paracoccidioidomycosis, a pulmonary mycosis acquired by inhalation of fungal airborne propagules, which may disseminate to several organs and tissues, leading to a severe form of the disease. Adhesion to and invasion of host cells are essential steps involved in the infection and dissemination of pathogens. Furthermore, pathogens use their surface molecules to bind to host extracellular matrix components to establish infection. Here, we report the characterization of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) ofP. brasiliensisas an adhesin, which can be related to fungus adhesion and invasion. TheP. brasiliensisGAPDH was overexpressed inEscherichia coli, and polyclonal antibody against this protein was obtained. By immunoelectron microscopy and Western blot analysis, GAPDH was detected in the cytoplasm and the cell wall of the yeast phase ofP. brasiliensis. The recombinant GAPDH was found to bind to fibronectin, laminin, and type I collagen in ligand far-Western blot assays. Of special note, the treatment ofP. brasiliensisyeast cells with anti-GAPDH polyclonal antibody and the incubation of pneumocytes with the recombinant protein promoted inhibition of adherence and internalization ofP. brasiliensisto those in vitro-cultured cells. These observations indicate that the cell wall-associated form of the GAPDH inP. brasiliensiscould be involved in mediating binding of fungal cells to fibronectin, type I collagen, and laminin, thus contributing to the adhesion of the microorganism to host tissues and to the dissemination of infection.
Immunological Correlates for Protection against Intranasal Challenge of
Bacillus anthracis
Spores Conferred by a Protective Antigen-Based Vaccine in Rabbits
Authors: Weiss Shay , Kobiler David , Levy Haim , Marcus Hadar , Pass Avi , Rothschild Nili , Altboum Zeev 
Published: December 2005

ABSTRACT

Correlates between immunological parameters and protection against
Bacillus anthracis
infection in animals vaccinated with protective antigen (PA)-based vaccines could provide surrogate markers to evaluate the putative protective efficiency of immunization in humans. In previous studies we demonstrated that neutralizing antibody levels serve as correlates for protection in guinea pigs (S. Reuveny et al., Infect. Immun. 69:2888-2893, 2001; H. Marcus et al., Infect. Immun. 72:3471-3477, 2004). In this study we evaluated similar correlates for protection by active and passive immunization of New Zealand White rabbits. Full immunization and partial immunization were achieved by single and multiple injections of standard and diluted doses of a PA-based vaccine. Passive immunization was carried out by injection of immune sera from rabbits vaccinated with PA-based vaccine prior to challenge with
B. anthracis
spores. Immunized rabbits were challenged by intranasal spore instillation with one of two virulent strains (strains Vollum and ATCC 6605). The immune competence was estimated by measuring the level of total anti-PA antibodies, the neutralizing antibody titers, and the conferred protective immunity. The results indicate that total anti-PA antibody titers greater than 1 × 10
5
conferred protection, whereas lower titers (between 10
4
and 10
5
) provided partial protection but failed to predict protection. Neutralizing antibody titers between 500 and 800 provided partial protection, while titers higher than 1,000 conferred protection. In conclusion, this study emphasizes that regardless of the immunization regimen or the time of challenge, neutralizing antibody titers are better predictors of protection than total anti-PA titers.
Role of Hyaluronidase in Subcutaneous Spread and Growth of Group A Streptococcus
Authors: Rivera Starr Clarise , Engleberg N. Cary 
Published: December 2005

ABSTRACT

Group A streptococcus (GAS) depends on a hyaluronic acid (HA) capsule to evade phagocytosis and to interact with epithelial cells. Paradoxically, GAS also produces hyaluronidase (Hyl), an enzyme that cleaves HA. A common assumption is that Hyl digests structurally identical HA in human tissue to promote bacterial spread. We inactivated the gene encoding extracellular hyaluronidase,
hylA
, in a clinical Hyl
+
isolate. Hyl
+
and an isogenic Hyl
−
mutant were injected subcutaneously into mice with or without high-molecular-weight dextran blue. The Hyl
−
strain produced small lesions with dye concentrated in close proximity. The Hyl
+
strain produced identical lesions, but the dye diffused subcutaneously. However, Hyl
+
bacteria were not isolated from unaffected skin stained by dye diffusion. Thus, Hyl digests tissue HA and facilitates spread of large molecules but is not sufficient to cause subcutaneous diffusion of bacteria or to affect lesion size. GAS capsule expression was assayed periodically during broth culture and was reduced in Hyl
+
strains relative to Hyl
−
strains at the onset and the end of active capsule synthesis but not during peak synthesis in mid-exponential phase. Thus, Hyl is not sufficiently active to remove capsule during peak synthesis. To demonstrate a possible nutritional role for Hyl, GAS was shown to grow with N-acetylglucosamine but not
d
-glucuronic acid (both components of HA) as a sole carbon source. However, only Hyl
+
strains could grow utilizing HA as a sole carbon source, suggesting that Hyl may permit the organism to utilize host HA or its own capsule as an energy source.
DNA Adenine Methyltransferase Influences the Virulence of
Aeromonas hydrophila
Authors: Erova Tatiana E. , Pillai Lakshmi , Fadl Amin A. , Sha Jian , Wang Shaofei , Galindo Cristi L. , Chopra Ashok K. 
Published: December 2005

ABSTRACT

Among the various virulence factors produced by
Aeromonas hydrophila
, a type II secretion system (T2SS)-secreted cytotoxic enterotoxin (Act) and the T3SS are crucial in the pathogenesis of
Aeromonas
-associated infections. Our laboratory molecularly characterized both Act and the T3SS from a diarrheal isolate, SSU of
A. hydrophila
, and defined the role of some regulatory genes in modulating the biological effects of Act. In this study, we cloned, sequenced, and expressed the DNA adenine methyltransferase gene of
A. hydrophila
SSU (
dam
AhSSU
) in a T7 promoter-based vector system using
Escherichia coli
ER2566 as a host strain, which could alter the virulence potential of
A. hydrophila
. Recombinant Dam, designated as M.AhySSUDam, was produced as a histidine-tagged fusion protein and purified from an
E. coli
cell lysate using nickel affinity chromatography. The purified Dam had methyltransferase activity, based on its ability to transfer a methyl group from
S
-adenosyl-
l
-methionine to N
6
-methyladenine-free lambda DNA and to protect methylated lambda DNA from digestion with DpnII but not against the DpnI restriction enzyme. The
dam
gene was essential for the viability of the bacterium, and overproduction of Dam in
A. hydrophila
SSU, using an arabinose-inducible, P
BAD
promoter-based system, reduced the virulence of this pathogen. Specifically, overproduction of M.AhySSUDam decreased the motility of the bacterium by 58%. Likewise, the T3SS-associated cytotoxicity, as measured by the release of lactate dehydrogenase enzyme in murine macrophages infected with the Dam-overproducing strain, was diminished by 55% compared to that of a control
A. hydrophila
SSU strain harboring the pBAD vector alone. On the contrary, cytotoxic and hemolytic activities associated with Act as well as the protease activity in the culture supernatant of a Dam-overproducing strain were increased by 10-, 3-, and 2.4-fold, respectively, compared to those of the control
A. hydrophila
SSU strain. The Dam-overproducing strain was not lethal to mice (100% survival) when given by the intraperitoneal route at a dose twice that of the 50% lethal dose, which within 2 to 3 days killed 100% of the animals inoculated with the
A. hydrophila
control strain. Taken together, our data indicated alteration of
A. hydrophila
virulence by overproduction of Dam.
GroEL ofLactobacillus johnsoniiLa1 (NCC 533) Is Cell Surface Associated: Potential Role in Interactions with the Host and the Gastric PathogenHelicobacter pylori
Authors: Bergonzelli Gabriela E. , Granato Dominique , Pridmore Raymond D. , Marvin-Guy Laure F. , Donnicola Dominique , Corthésy-Theulaz Irène E. 
Published: December 2005

ABSTRACTHeat shock proteins of the GroEL or Hsp60 class are highly conserved proteins essential to all living organisms. Even though GroEL proteins are classically considered intracellular proteins, they have been found at the surface of several mucosal pathogens and have been implicated in cell attachment and immune modulation. The purpose of the present study was to investigate the GroEL protein of a gram-positive probiotic bacterium,Lactobacillus johnsoniiLa1 (NCC 533). Its presence at the bacterial surface was demonstrated using a whole-cell enzyme-linked immunosorbent assay and could be detected in bacterial spent culture medium by immunoblotting. To assess binding of La1 GroEL to mucins and intestinal epithelial cells, the La1 GroEL protein was expressed inEscherichia coli. We report here that La1 recombinant GroEL (rGroEL) binds to mucins and epithelial cells and that this binding is pH dependent. Immunomodulation studies showed that La1 rGroEL stimulates interleukin-8 secretion in macrophages and HT29 cells in a CD14-dependent mechanism. This property is common to rGroEL from other gram-positive bacteria but not to the rGroEL of the gastric pathogenHelicobacter pylori. In addition, La1 rGroEL mediates the aggregation ofH. pyloribut not that of other intestinal pathogens. Our in vitro results suggest that GroEL proteins from La1 and other lactic acid bacteria might play a role in gastrointestinal homeostasis due to their ability to bind to components of the gastrointestinal mucosa and to aggregateH. pylori.
Type IV Pili ofNeisseria gonorrhoeaeInfluence the Activation of Human CD4+T Cells
Authors: Plant Laura J. , Jonsson Ann-Beth 
Published: December 2005

ABSTRACTNeisseria gonorrhoeaeis the causative agent of the sexually transmitted disease gonorrhea, and infection with this organism is typically associated with an intense inflammatory response. In many individuals, however, the infection is asymptomatic and can progress to serious secondary complications. The type IV pili ofNeisseria gonorrhoeaemediate binding of the bacteria to host cells and are involved in cellular signal transduction. In these studies we have demonstrated that gonococcal pili influence human CD4+T cells by using isogenic strains ofN. gonorrhoeaewith piliated and nonpiliated phenotypes. To determine the impact of piliation on the cellular status, we examined the expression of activation markers, cellular proliferation, and the production of cytokines after infection. The activation marker CD69 showed significantly increased expression on cells infected with the piliated strain, and this expression was dependent on costimulation of the T-cell receptor. Infection with piliated gonococci also altered T-cell proliferation and influenced the production of the regulatory cytokine interleukin-10. PilC, the putative pilus adhesin, was also observed to influence cellular activation but had no impact on the proliferation of cells further indicating that pilus-mediated adhesion is important in gonococcal stimulation of CD4+T cells. These results show that the piliation status of gonococci influences CD4+T-cell activation and that the adhesion mediated by pilus components aids in the regulation of the T-cell response toN. gonorrhoeae.
Identification and Characterization of the Capsular Polysaccharide (K-Antigen) Locus of
Porphyromonas gingivalis
Authors: Aduse-Opoku Joseph , Slaney Jennifer M. , Hashim Ahmed , Gallagher Alexandra , Gallagher Robert P. , Rangarajan Minnie , Boutaga Khalil , Laine Marja L. , Van Winkelhoff Arie J. , Curtis Michael A. 
Published: December 2005

ABSTRACT

Capsular polysaccharides of gram-negative bacteria play an important role in maintaining the structural integrity of the cell in hostile environments and, because of their diversity within a given species, can act as useful taxonomic aids. In order to characterize the genetic locus for capsule biosynthesis in the oral gram-negative bacterium
Porphyromonas gingivalis
, we analyzed the genome of
P. gingivalis
W83 which revealed two candidate loci at PG0106
-
PG0120 and PG1135-PG1142 with sufficient coding capacity and appropriate gene functions based on comparisons with capsule-coding loci in other bacteria. Insertion and deletion mutants were prepared at PG0106-PG0120 in
P. gingivalis
W50—a K1 serotype. Deletion of PG0109-PG0118 and PG0116-PG0120 both yielded mutants which no longer reacted with antisera to K1 serotypes. Restriction fragment length polymorphism analysis of the locus in strains representing all six K-antigen serotypes and K
−
strains demonstrated significant variation between serotypes and limited conservation within serotypes. In contrast, PG1135-PG1142 was highly conserved in this collection of strains. Sequence analysis of the capsule locus in strain 381 (K
−
strain) demonstrated synteny with the W83 locus but also significant differences including replacement of PG0109-PG0110 with three unique open reading frames, deletion of PG0112-PG0114, and an internal termination codon within PG0106, each of which could contribute to the absence of capsule expression in this strain. Analysis of the Arg-gingipains in the capsule mutants of strain W50 revealed no significant changes to the glycan modifications of these enzymes, which indicates that the glycosylation apparatus in
P. gingivalis
is independent of the capsule biosynthetic machinery.
Role of theluxSQuorum-Sensing System in Biofilm Formation and Virulence ofStaphylococcus epidermidis
Authors: Xu Lin , Li Hualin , Vuong Cuong , Vadyvaloo Viveka , Wang Jianping , Yao Yufeng , Otto Michael , Gao Qian 
Published: December 2005

ABSTRACTNosocomial infections caused byStaphylococcus epidermidisare characterized by biofilm formation on implanted medical devices. Quorum-sensing regulation plays a major role in the biofilm development of many bacterial pathogens. Here, we describeluxS, a quorum-sensing system in staphylococci that has a significant impact on biofilm development and virulence. We constructed an isogenicΔluxSmutant strain of a biofilm-forming clinical isolate ofS. epidermidisand demonstrated thatluxSsignaling is functional inS. epidermidis. The mutant strain showed increased biofilm formation in vitro and enhanced virulence in a rat model of biofilm-associated infection. Genetic complementation and addition of autoinducer 2-containing culture filtrate restored the wild-type phenotype, demonstrating thatluxSrepressed biofilm formation through a cell-cell signaling mechanism based on autoinducer 2 secretion. Enhanced production of the biofilm exopolysaccharide polysaccharide intercellular adhesin in the mutant strain is presumably the major cause of the observed phenotype. Theagrquorum-sensing system has previously been shown to impact biofilm development and biofilm-associated infection in a way similar to that ofluxS, although by regulation of different factors. Our study indicates a general scheme of quorum-sensing regulation of biofilm development in staphylococci, which contrasts with that observed in many other bacterial pathogens.