bluuebunny/crossref_metadata_2025_split huggingface dataset:
Humoral Responses to
Porphyromonas gingivalis
Gingipain Adhesin Domains in Subjects with Chronic Periodontitis
Authors: Nguyen Ky-Anh , DeCarlo Arthur A. , Paramaesvaran Mayuri , Collyer Charles A. , Langley David B. , Hunter Neil 
Published: February 2004

ABSTRACT

The gingipains have been implicated in the pathogenicity of
Porphyromonas gingivalis
, a major etiologic agent of chronic periodontitis. Mature gingipains often present as a membrane-bound glycosylated proteinase-adhesin complex comprising multiple adhesin domains (HA1 to -4) and a catalytic domain. Using recombinant adhesin domains, we were able to show that patients with chronic periodontitis produce significantly more immunoglobulin G reactive with gingipain domains than a corresponding group with healthy periodontium. Titers were predominantly directed toward the carbohydrate epitopes shared between the gingipains and the lipopolysaccharide of
P. gingivalis
with little recognition of the peptide backbone of the catalytic domains. Distribution of titers to peptide epitopes of the adhesin domains was as follows: HA4 ≈ HA1 > HA3 ≫ HA2. No correlation was observed between markers of disease severity and titers to individual adhesins within the disease group. Posttreatment titers showed no change or a decrease in titers for the majority of patients except for titers to the HA2 domain which showed marked increases in a few responding patients. Since the HA2 domain is important in hemoglobin binding and acquisition of essential porphyrin, boosting titers of antibodies to this domain may have the potential to control the growth of this organism.
Role of NK Cells and Gamma Interferon in Transplacental Passage ofToxoplasma gondiiin a Mouse Model of Primary Infection
Authors: Abou-Bacar Ahmed , Pfaff Alexander W. , Georges Sophie , Letscher-Bru Valérie , Filisetti Denis , Villard Odile , Antoni Elisabeth , Klein Jean-Paul , Candolfi Ermanno 
Published: February 2004

ABSTRACTProtective immunity in mice infected withToxoplasma gondiiis mainly mediated by NK cells, CD4 and CD8 T cells, and type 1 cytokines, such as gamma interferon (IFN-γ). To clarify the roles of NK cells and IFN-γ in protection against primary congenital toxoplasmosis, we used recombination activating gene 2 knockout (RAG-2−/−) mice, which lack T and B lymphocytes, in comparison with the wild-type BALB/c model. RAG-2−/−mice had a significantly lower risk of fetal toxoplasmosis than BALB/c mice (25 versus 63.9%;P= 0.003). This protection was associated with an increased number of maternal NK cells, IFN-γ secretion by spleen cells, and decreased parasitemia. In the RAG-2−/−mice, NK cell depletion increased both the rate of fetal infection, to 56.5% (P= 0.02), and the blood parasite burden. Conversely, in the BALB/c mice, this treatment did not modify maternofetal transmission or the blood parasite burden. Neutralization of IFN-γ in both infected RAG-2−/−and BALB/c mice decreased congenitalToxoplasmatransmission, contrasting with an exacerbation of maternal infection. These data suggest that a partially protective immunity against congenital toxoplasmosis is achieved due to the increased number of NK cells in RAG-2−/−mice. However, it seems that IFN-γ enhances, directly or indirectly, the transplacental transmission.
Survival of
Aspergillus fumigatus
in Serum Involves Removal of Iron from Transferrin: the Role of Siderophores
Authors: Hissen A. H. T. , Chow J. M. T. , Pinto L. J. , Moore M. M. 
Published: February 2004

ABSTRACT

Aspergillus fumigatus
is a filamentous fungus which can cause invasive disease in immunocompromised individuals.
A. fumigatus
can grow in medium containing up to 80% human serum, despite very low concentrations of free iron. The purpose of this study was to determine the mechanism by which
A. fumigatus
obtains iron from the serum iron-binding protein transferrin. In iron-depleted minimal essential medium (MEM),
A. fumigatus
growth was supported by the addition of holotransferrin (holoTf) or FeCl
3
but not by the addition of apotransferrin (apoTf). Proteolytic degradation of transferrin by
A. fumigatus
occurred in MEM-serum; however, transferrin degradation did not occur until late logarithmic phase. Moreover, transferrin was not degraded by
A. fumigatus
incubated in MEM-holoTf. Urea polyacrylamide gel electrophoresis showed that in MEM-holoTf, holoTf was completely converted to apoTf by
A. fumigatus
. In human serum, all of the monoferric transferrin was converted to apoTf within 8 h. Siderophores were secreted by
A. fumigatus
after 8 h of growth in MEM-serum and 12 h in MEM-holoTf. The involvement of small molecules in iron acquisition was confirmed by the fact that transferrin was deferrated by
A. fumigatus
even when physically separated by a 12-kDa-cutoff membrane. Five siderophores were purified from
A. fumigatus
culture medium, and the two major siderophores were identified as triacetylfusarinine C and ferricrocin. Both triacetylfusarinine C and ferricrocin removed iron from holoTf with an affinity comparable to that of ferrichrome. These data indicate that
A. fumigatus
survival in human serum in vitro involves siderophore-mediated removal of iron from transferrin. Proteolytic degradation of transferrin may play a secondary role in iron acquisition.
The
Klebsiella pneumoniae
O Antigen Contributes to Bacteremia and Lethality during Murine Pneumonia
Authors: Shankar-Sinha Sunita , Valencia Gabriel A. , Janes Brian K. , Rosenberg Jessica K. , Whitfield Chris , Bender Robert A. , Standiford Ted J. , Younger John G. 
Published: February 2004

ABSTRACT

Bacterial surface carbohydrates are important pathogenic factors in gram-negative pneumonia infections. Among these factors, O antigen has been reported to protect pathogens against complement-mediated killing. To examine further the role of O antigen, we insertionally inactivated the gene encoding a galactosyltransferase necessary for serotype O1 O-antigen synthesis (
wbbO
) from
Klebsiella pneumoniae
43816. Analysis of the mutant lipopolysaccharide by sodium dodecyl sulfate-polyacrylamide gel electrophoresis confirmed the absence of O antigen. In vitro, there were no detectable differences between wild-type
K. pneumoniae
and the O-antigen-deficient mutant in regard to avid binding by murine complement C3 or resistance to serum- or whole-blood-mediated killing. Nevertheless, the 72-h 50% lethal dose of the wild-type strain was 30-fold greater than that of the mutant (2 × 10
3
versus 6 × 10
4
CFU) after intratracheal injection in ICR strain mice. Despite being less lethal, the mutant organism exhibited comparable intrapulmonary proliferation at 24 h compared to the level of the wild type. Whole-lung chemokine expression (CCL3 and CXCL2) and bronchoalveolar inflammatory cell content were also similar between the two infections. However, whereas the wild-type organism produced bacteremia within 24 h of infection in every instance, bacteremia was not seen in mutant-infected mice. These results suggest that during murine pneumonia caused by
K. pneumoniae
, O antigen contributes to lethality by increasing the propensity for bacteremia and not by significantly changing the early course of intrapulmonary infection.
Bordetella pertussisInfection of Primary Human Monocytes Alters HLA-DR Expression
Authors: Shumilla Jennifer A. , Lacaille Vashti , Hornell Tara M. C. , Huang Jennifer , Narasimhan Supraja , Relman David A. , Mellins Elizabeth D. 
Published: February 2004

ABSTRACTBordetella pertussisis the causative agent of whooping cough, a potentially lethal respiratory disease in children. In immunocompetent individuals,B. pertussisinfection elicits an effective adaptive immune response driven by activated CD4+T cells. However, liveB. pertussispersists in the host for 3 to 4 weeks prior to clearance. Thus,B. pertussisappears to have evolved short-term mechanisms for immune system evasion. We investigated the effects ofB. pertussiswild-type strain BP338 on antigen presentation in primary human monocytes. BP338 infection reduced cell surface expression of HLA-DR and CD86 but not that of major histocompatibility complex class I proteins. This change in cell surface HLA-DR expression reflected intracellular redistribution of HLA-DR. The proportion of peptide-loaded molecules was unchanged in infected cells, suggesting that intracellular retention occurred after peptide loading. AlthoughB. pertussisinfection of monocytes induced rapid and robust expression of interleukin-10 (IL-10), HLA-DR redistribution did not appear to be explained by increased IL-10 levels. BP338-infected monocytes exhibited reduced synthesis of HLA-DR dimers. Interestingly, those HLA-DR proteins that were generated appeared to be longer-lived than HLA-DR in uninfected monocytes. BP338 infection also prevented gamma interferon (IFN-γ) induction of HLA-DR protein synthesis. Using mutant strains ofB. pertussis, we found that reduction in HLA-DR surface expression was due in part to the presence of pertussis toxin whereas the inhibition of IFN-γ induction of HLA-DR could not be linked to any of the virulence factors tested. These data demonstrate thatB. pertussisutilizes several mechanisms to modulate HLA-DR expression.
Cross-Species Surface Display of Functional Spirochetal Lipoproteins by Recombinant
Borrelia burgdorferi
Authors: Zückert Wolfram R. , Lloyd Jill E. , Stewart Philip E. , Rosa Patricia A. , Barbour Alan G. 
Published: February 2004

ABSTRACT

Surface-exposed lipoproteins of relapsing fever (RF) and Lyme borreliosis
Borrelia
spirochetes mediate certain interactions of the bacteria with their arthropod and vertebrate hosts. RF spirochetes such as
Borrelia hermsii
serially evade the host's antibody response by multiphasic antigenic variation of Vsp and Vlp proteins. Furthermore, the expression of Vsp1 and Vsp2 by
Borrelia turicatae
is associated with neurotropism and higher blood densities, respectively. In contrast to RF
Borrelia
species, the Lyme borreliosis spirochete
Borrelia burgdorferi
is amenable to genetic manipulation. To facilitate structure-function analyses of RF surface lipoproteins, we used recombinant plasmids to introduce full-length
vsp1
and
vsp2
as well as two representative
vlp
genes into
B. burgdorferi
cells. Recombinant
B. burgdorferi
cells constitutively expressed the proteins under the control of the
B. burgdorferi flaB
promoter. Antibody and protease accessibility assays indicated proper surface exposure and folding. Expression of Vsp1 and Vsp2 conferred glycosaminoglycan binding to recombinant
B. burgdorferi
cells that was similar to that observed with purified recombinant proteins and
B. turicatae
expressing native Vsp. These data demonstrate that the lipoprotein modification and export mechanisms in the genus
Borrelia
are conserved. They also validate the use of recombinant
B. burgdorferi
in studies of surface lipoprotein structure-function and the biogenesis of spirochete membranes.
Nutritional Effects on Host Response to Lung Infections with Mucoid
Pseudomonas aeruginosa
in Mice
Authors: van Heeckeren Anna M. , Schluchter Mark , Xue Lintong , Alvarez Juan , Freedman Steven , St. George Judith , Davis Pamela B. 
Published: February 2004

ABSTRACT

In cystic fibrosis, a recessive genetic disease caused by defects in the cystic fibrosis conductance regulator (CFTR), the main cause of death is lung infection and inflammation. Nutritional deficits have been proposed to contribute to the excessive host inflammatory response in both humans and
Cftr
-knockout mice.
Cftr
-knockout mice and gut-corrected
Cftr
-knockout mice expressing human CFTR primarily in the gut were challenged with
Pseudomonas aeruginosa
-laden agarose beads; they responded similarly with respect to bronchoalveolar lavage cell counts and levels of the acute-phase cytokines tumor necrosis factor alpha, interleukin-1β (IL-1β), and IL-6. Wild-type mice fed the liquid diet used to prevent intestinal obstruction in
Cftr
-knockout mice had inflammatory responses to
P. aeruginosa
-laden agarose beads similar to those of wild-type mice fed an enriched solid diet, so dietary effects are unlikely to account for differences between wild-type mice and mice with cystic fibrosis. Finally, since cystic fibrosis patients and
Cftr
-knockout mice have an imbalance in fatty acids (significantly lower-than-normal levels of docosahexaenoic acid), the effects of specific supplementation with docosahexaenoic acid of wild-type and
Cftr
-knockout mice on their inflammatory responses to
P. aeruginosa
-laden agarose beads were tested. There were no significant differences (
P
= 0.35) in cumulative survival rates between
Cftr
-knockout mice and wild-type mice provided with either the liquid diet Peptamen or Peptamen containing docosahexaenoic acid. In conclusion, diet and docosahexaenoic acid imbalances alone are unlikely to explain the differences in the host response to lung infections with mucoid
P. aeruginosa
between mice with cystic fibrosis and their wild-type counterparts.
Nod1 Is an Essential Signal Transducer in Intestinal Epithelial Cells Infected with Bacteria That Avoid Recognition by Toll-Like Receptors
Authors: Kim Jae Gyu , Lee Sung Joong , Kagnoff Martin F. 
Published: February 2004

ABSTRACTThe transcription factor NF-κB in human intestinal epithelial cells plays a central role in regulating genes that govern the onset of mucosal inflammatory responses following intestinal microbial infection. Nod1 is a cytosolic pattern recognition receptor in mammalian cells that senses components of microbial peptidoglycans and signals the activation of NF-κB. The aim of these studies was to assess the functional importance of Nod1 in activating NF-κB and NF-κB proinflammatory target genes in human intestinal epithelium. Human colon epithelial cells that constitutively express Nod1 were used as a model intestinal epithelium. These cells do not signal through Toll-like receptor 4 (TLR4) or respond to bacterial lipopolysaccharide, but they express functional TLR5 and interleukin 1 (IL-1) receptors that signal the activation of NF-κB in response to bacterial flagellin or IL-1 stimulation. Stable expression of dominant negative (DN) Nod1 in colon epithelial cells prevented IκB kinase and NF-κB activation in response to infection with enteroinvasiveEscherichia coli. In contrast, DN Nod1 did not eliminate IL-1 or flagellin-stimulated NF-κB activation. Inhibition of NF-κB was accompanied by inhibition of NF-κB target genes that provide signals for the mucosal influx of neutrophils during intestinal infection. We conclude that signaling through Nod1 is required for activating NF-κB in human intestinal epithelial cells infected with gram-negative enteric bacteria that can bypass TLR activation. Signaling through Nod1 provides the intestinal epithelium with a backup mechanism for rapidly activating innate immunity during infection with a group of highly invasive pathogenic gram-negative bacteria.
Evidence for a Hybrid Genomic Island in Verocytotoxin-Producing
Escherichia coli
CL3 (Serotype O113:H21) Containing Segments of EDL933 (Serotype O157:H7) O Islands 122 and 48
Authors: Shen Songhai , Mascarenhas Mariola , Rahn Kris , Kaper James B. , Karmal Mohamed A. 
Published: February 2004

ABSTRACT

Genomic O island 122 (OI-122) of the verocytotoxin-producing
Escherichia coli
(VTEC) strain EDL933 contains four putative virulence genes, Z4321, Z4326, Z4332, and Z4333. However, strain CL3 (serotype O113:H21) contains only Z4321, not the other three genes. To determine whether Z4321 is part of a different genomic island in CL3, a region of 27,293 bp up- and downstream of Z4321 was sequenced and found to contain elements of two different EDL933 genomic islands (OI-48 and OI-122) and a
Yersinia pestis
-like hemolysin/adhesin gene cluster. The region contained OI-48 genes Z1635, Z1636, and Z1637 at the left terminus and Z1641, Z1642, Z1643, and Z1644 at the right. The middle portion consisted of OI-48 gene Z1640, which was separated into three fragments by genomic segments including the
Y. pestis
cluster and EDL933 OI-122 genes Z4322, Z4321, and Z4318. In a PCR investigation of 36 VTEC strains of different serotypes, intact Z1640 was present in strains of serotypes O157:H7, O26:H11, O103:H2, O111:NM, and O145:NM, which are associated with hemolytic uremic syndrome and outbreaks. In contrast, fragmented Z1640 was seen in strains of nonepidemic serotypes, such as O91:H21 and O113:H21, and in animal serotypes that have not been associated with human disease, indicating that Z1640 might be a virulence gene.
Helicobacter pylori
and Complex Gangliosides
Authors: Roche Niamh , Ångström Jonas , Hurtig Marina , Larsson Thomas , Borén Thomas , Teneberg Susann 
Published: February 2004

ABSTRACT

Recognition of sialic acid-containing glycoconjugates by the human gastric pathogen
Helicobacter pylori
has been repeatedly demonstrated. To investigate the structural requirements for
H. pylori
binding to complex gangliosides, a large number of gangliosides were isolated and characterized by mass spectrometry and proton nuclear magnetic resonance. Ganglioside binding of sialic acid-recognizing
H. pylori
strains (strains J99 and CCUG 17874) and knockout mutant strains with the sialic acid binding adhesin SabA or the NeuAcα3Galβ4GlcNAcβ3Galβ4GlcNAcβ-binding neutrophil-activating protein HPNAP deleted was investigated using the thin-layer chromatogram binding assay. The wild-type bacteria bound to
N
-acetyllactosamine-based gangliosides with terminal α3-linked NeuAc, while gangliosides with terminal NeuGcα3, NeuAcα6, or NeuAcα8NeuAcα3 were not recognized. The factors affecting binding affinity were identified as (i) the length of the
N
-acetyllactosamine carbohydrate chain, (ii) the branches of the carbohydrate chain, and (iii) fucose substitution of the
N
-acetyllactosamine core chain. While the J99/NAP
−
mutant strain displayed a ganglioside binding pattern identical to that of the parent J99 wild-type strain, no ganglioside binding was obtained with the J99/SabA
−
mutant strain, demonstrating that the SabA adhesin is the sole factor responsible for the binding of
H. pylori
bacterial cells to gangliosides.
Adenylate Cyclase Toxin fromBordetella pertussisSynergizes with Lipopolysaccharide To Promote Innate Interleukin-10 Production and Enhances the Induction of Th2 and Regulatory T Cells
Authors: Ross Pádraig J. , Lavelle Ed C. , Mills Kingston H. G. , Boyd Aoife P. 
Published: February 2004

ABSTRACTAdenylate cyclase toxin (CyaA) fromBordetella pertussiscan subvert host immune responses allowing bacterial colonization. Here we have examined its adjuvant and immunomodulatory properties and the possible contribution of lipopolysaccharide (LPS), known to be present in purified CyaA preparations. CyaA enhanced antigen-specific interleukin-5 (IL-5) and IL-10 production and immunoglobulin G1 antibodies to coadministered antigen in vivo. Antigen-specific CD4+-T-cell clones generated from mice immunized with antigen and CyaA had cytokine profiles characteristic of Th2 or type 1 regulatory T (Tr1) cells. Since innate immune cells direct the induction of T-cell subtypes, we examined the influence of CyaA on activation of dendritic cells (DC) and macrophages. CyaA significantly augmented LPS-induced IL-6 and IL-10 and inhibited LPS-driven tumor necrosis factor alpha and IL-12p70 production from bone marrow-derived DC and macrophages. CyaA also enhanced cell surface expression of CD80, CD86, and major histocompatibility class II on immature DC. The stimulatory activity of our CyaA preparation for IL-10 production and CD80, CD86, and major histocompatibility complex class II expression was attenuated following the addition of polymyxin B or with the use of DC from Toll-like receptor (TLR) 4-defective mice. However, treatment of DC with LPS alone at the concentration present in the CyaA preparation (0.2 ng/ml) failed to activate DC in vitro. Our findings demonstrate that activation of innate cells in vitro by CyaA is dependent on a second signal through a TLR and that CyaA can promote Th2/Tr1-cell responses by inhibiting IL-12 and promoting IL-10 production by DC and macrophages.
Dissolved Oxygen Levels Alter Gene Expression and Antigen Profiles in
Borrelia burgdorferi
Authors: Seshu J. , Boylan Julie A. , Gherardini Frank C. , Skare Jonathan T. 
Published: February 2004

ABSTRACT

The Lyme disease spirochete,
Borrelia burgdorferi
, encounters many environmental signals as it cycles between the arthropod vector and mammalian hosts, including temperature, pH, and other host factors. To test the possibility that dissolved oxygen modulates gene expression in
B. burgdorferi
, spirochetes were exposed to differential levels of dissolved oxygen, and distinct alterations were observed at both the transcriptional and translational levels. Specifically NapA, a Dps/Dpr homologue involved in the oxidative stress response in other bacteria, was reduced when
B. burgdorferi
was grown under oxygen-limiting conditions. In contrast, several immunoreactive proteins were altered when tested with infection-derived sera from different hosts. Specifically, OspC, DbpA, and VlsE were synthesized at greater levels when cells were grown in limiting oxygen, whereas VraA was reduced. The levels of oxygen in the medium did not affect OspA production. Real-time reverse transcription-PCR analysis of RNA isolated from infectious isolates of strains B31 and cN40 indicated that the expression of
ospC
,
dbpA
, and
vlsE
increased while
napA
expression decreased under dissolved-oxygen-limiting conditions, whereas
flaB
was not affected. The reverse transcription-PCR results corroborated the immunoblot analyses and indicated that the increase in OspC, DbpA, and VlsE was due to regulation at the transcriptional level of the genes encoding these antigens. These results indicate that dissolved oxygen modulates gene expression in
B. burgdorferi
and imply that the redox environment may be an additional regulatory cue that spirochetes exploit to adapt to the disparate niches that they occupy in nature.
Role for Serine Protease HtrA (DegP) ofStreptococcus pyogenesin the Biogenesis of Virulence Factors SpeB and the Hemolysin Streptolysin S
Authors: Lyon William R. , Caparon Michael G. 
Published: February 2004

ABSTRACTThe serine protease HtrA is involved in the folding and maturation of secreted proteins, as well as in the degradation of proteins that misfold during secretion. Depletion of HtrA has been shown to affect the sensitivity of many organisms to thermal and environmental stresses, as well as being essential for virulence in many pathogens. In the present study, we compared the behaviors of several different HtrA mutants of the gram-positive pathogenStreptococcus pyogenes(group A streptococcus). Consistent with prior reports, insertional inactivation ofhtrA, the gene that encodes HtrA, resulted in a mutant that grew poorly at 37°C. However, an identical phenotype was observed when a similar polar insertion was placed immediately downstream ofhtrAin the streptococcal chromosome, suggesting that the growth defect of the insertion mutant was not a direct result of insertional inactivation ofhtrA. This conclusion was supported by the observation that a nonpolar deletion mutation ofhtrAdid not produce the growth defect. However, this mutation did affect the production of several secreted virulence factors whose biogenesis requires extensive processing. For the SpeB cysteine protease, the loss of HtrA was associated with a failure to proteolytically process the zymogen to an active protease. For the streptolysin S hemolysin, a dramatic increase in hemolytic activity resulted from the depletion of HtrA. Interestingly, HtrA-deficient mutants were not attenuated in a murine model of subcutaneous infection. These data add to the growing body of information that implies an important role for HtrA in the biogenesis of secreted proteins in gram-positive bacteria.