bluuebunny/crossref_metadata_2025_split huggingface dataset:
Broad Degradation of Proapoptotic Proteins with the Conserved Bcl-2 Homology Domain 3 during Infection with
Chlamydia trachomatis
Authors: Ying Songmin , Seiffert Barbara M. , Häcker Georg , Fischer Silke F. 
Published: February 2005

ABSTRACT

Chlamydiae are obligate intracellular bacteria that can inhibit apoptosis of their host cell. As shown recently, this inhibition is in part explained by the proteolytic degradation of the proapoptotic Bcl-2 family members (BH3-only proteins) Bim, Puma, and Bad upon chlamydial infection. In this study, we further explore this antiapoptotic mechanism. In cells infected with a
Chlamydia trachomatis
L2 strain, Bim, Puma, and Bad were degraded with similar kinetics, and the degradation of all three was blocked by inhibition of the proteasome. Furthermore, the BH3-only proteins Bmf, Noxa, and tBid were also targeted by chlamydial infection. The constitutively expressed Bmf disappeared during infection. When Noxa was experimentally induced, the levels were also reduced by infection with
C. trachomatis
. In death-receptor-induced apoptosis, cleaved and activated tBid was degraded, and this destruction was also prevented by inhibition of the proteasome. These results show that chlamydial infection leads to a broad degradation of BH3-only proteins. This loss of proapoptotic factors can explain the almost general protection of infected cells against apoptotic stimuli.
A
Vibrio vulnificus
Type IV Pilin Contributes to Biofilm Formation, Adherence to Epithelial Cells, and Virulence
Authors: Paranjpye Rohinee N. , Strom Mark S. 
Published: February 2005

ABSTRACT

Vibrio vulnificus
expresses a multitude of cell-associated and secreted factors that potentially contribute to pathogenicity, although the specific roles of most of these factors have been difficult to define. Previously we have shown that a mutation in
pilD
(originally designated
vvpD
), which encodes a type IV prepilin peptidase/
N
-methyltransferase, abolishes expression of surface pili, suggesting that they belong to the type IV class. In addition, a
pilD
mutant exhibits reduced adherence to HEp-2 cells, a block in secretion of several exoenzymes that follow the type II secretion pathway, and decreased virulence. In this study, we have cloned and characterized a
V. vulnificus
type IV pilin (PilA) that shares extensive homology to group A type IV pilins expressed by many pathogens, including
Vibrio cholerae
(PilA),
Pseudomonas aeruginosa
(PilA), and
Aeromonas hydrophila
(TapA). The
V. vulnificus pilA
gene is part of an operon and is clustered with three other pilus biogenesis genes,
pilBCD
. Inactivation of
pilA
reduces the ability of
V. vulnificus
to form biofilms and significantly decreases adherence to HEp-2 cells and virulence in iron dextran-treated mice. Southern blot analysis demonstrates the widespread presence of both
pilA
and
pilD
in clinical as well as environmental strains of
V. vulnificus
.
Staphylococcus aureus
Capsular Polysaccharide Types 5 and 8 Reduce Killing by Bovine Neutrophils In Vitro
Authors: Kampen Annette H. , Tollersrud Tore , Lund Arve 
Published: February 2005

ABSTRACT

Isogenic variants of
Staphylococcus aureus
strain Reynolds expressing either no capsule or capsular polysaccharide (CP) type 5 (CP5) or type 8 (CP8) were used to assess the effect of CP on bacterial killing and the respiratory burst of bovine neutrophils. The effects of antisera specific for CP5 and CP8 were also evaluated. The killing of live bacteria by isolated neutrophils was quantified in a bactericidal assay, while the respiratory burst after stimulation with live bacteria in whole blood was measured by flow cytometry. The expression of a CP5 or CP8 capsule protected the bacteria from being killed by bovine neutrophils in vitro (
P
< 0.001), and the capsule-expressing variants did not stimulate respiratory burst activity in calf whole blood. The addition of serotype-specific antisera increased the killing of the capsule-expressing bacteria and enhanced their stimulating effect in the respiratory burst assay (
P
< 0.01). When the
S. aureus
variants were grown under conditions known not to promote capsule expression, there were no significant differences between them. The present study demonstrates that the expression of
S. aureus
CP5 or CP8 confers resistance to opsonophagocytic killing and prevents the bacteria from inducing respiratory burst of bovine neutrophils in vitro and that these effects can be reversed by the addition of serotype-specific antisera.
Bordetella pertussis-Infected Human Monocyte-Derived Dendritic Cells Undergo Maturation and Induce Th1 Polarization and Interleukin-23 Expression
Authors: Fedele Giorgio , Stefanelli Paola , Spensieri Fabiana , Fazio Cecilia , Mastrantonio Paola , Ausiello Clara M. 
Published: February 2005

ABSTRACTBordetella pertussis, the causative agent of whooping cough, is internalized by several cell types, including epithelial cells, monocytes, and neutrophils. Although its ability to survive intracellularly is still debated, it has been proven that cell-mediated immunity (CMI) plays a pivotal role in protection. In this study we aimed to clarify the interaction ofB. pertussiswith human monocyte-derived dendritic cells (MDDC), evaluating the ability of the bacterium to enter MDDC, to survive intracellularly, to interfere with the maturation process and functional activities, and to influence the host immune responses. The results obtained showed thatB. pertussishad a low capability to be internalized by—and to survive in—MDDC. Upon contact with the bacteria, immature MDDC were induced to undergo phenotypic maturation and acquired antigen-presenting-cell functions. Despite the high levels of interleukin-10 (IL-10) and the barely detectable levels of IL-12 induced byB. pertussis, the bacterium induced maturation of MDDC and T helper 1 (Th1) polarized effector cells. Gene expression analysis of the IL-12 cytokine family clearly demonstrated thatB. pertussisinduced high levels of the p40 and p19 subunits of IL-23 yet failed to induce the expression of the p35 subunit of IL-12. Overall our findings show thatB. pertussis, even if it survives only briefly in MDDC, promotes the synthesis of IL-23, a newly discovered Th1 polarizing cytokine. A Th1-oriented immune response is thus allowed, relevant in the induction of an adequate CMI response, and typical of protection induced by natural infection or vaccination with whole-cell vaccines.
Demonstration of Type IV Pilus Expression and a Twitching Phenotype by
Haemophilus influenzae
Authors: Bakaletz Lauren O. , Baker Beth D. , Jurcisek Joseph A. , Harrison Alistair , Novotny Laura A. , Bookwalter James E. , Mungur Rachna , Munson Robert S. 
Published: February 2005

ABSTRACT

Haemophilus influenzae
is considered a nonmotile organism that expresses neither flagella nor type IV pili, although
H. influenzae
strain Rd possesses a cryptic pilus locus. We demonstrate here that the homologous gene cluster
pilABCD
in an otitis media isolate of nontypeable
H. influenzae
strain 86-028NP encodes a surface appendage that is highly similar, structurally and functionally, to the well-characterized subgroup of bacterial pili known as type IV pili. This gene cluster includes a gene (
pilA
) that likely encodes the major subunit of the heretofore uncharacterized
H. influenzae
-expressed type IV pilus, a gene with homology to a type IV prepilin peptidase (
pilD
) as well as two additional uncharacterized genes (
pilB
and
pilC
). A second gene cluster (
comABCDEF
) was also identified by homology to other
pil
or type II secretion system genes. When grown in chemically defined medium at an alkaline pH, strain 86-028NP produces approximately 7-nm-diameter structures that are near polar in location. Importantly, these organisms exhibit twitching motility. A mutation in the
pilA
gene abolishes both expression of the pilus structure and the twitching phenotype, whereas a mutant lacking ComE, a
Pseudomonas
PilQ homologue, produced large appendages that appeared to be membrane bound and terminated in a slightly bulbous tip. These latter structures often showed a regular pattern of areas of constriction and expansion. The recognition that
H. influenzae
possesses a mechanism for twitching motility will likely profoundly influence our understanding of
H. influenzae
-induced diseases of the respiratory tract and their sequelae.
Comparison between
Candida albicans
Agglutinin-Like Sequence Gene Expression Patterns in Human Clinical Specimens and Models of Vaginal Candidiasis
Authors: Cheng Georgina , Wozniak Karen , Wallig Matthew A. , Fidel Paul L. , Trupin Suzanne R. , Hoyer Lois L. 
Published: February 2005

ABSTRACT

Expression of the eight genes in the
Candida albicans
agglutinin-like sequence (ALS) family was studied by reverse transcription-PCR of RNA isolated from clinical vaginal fluid specimens and vaginal candidiasis model systems. Although expression of all ALS genes was detected across the set of clinical specimens,
ALS1
,
ALS2
,
ALS3
, and
ALS9
transcripts were detected most frequently, and expression of
ALS4
and
ALS5
was detected least frequently. Laboratory strain 3153A and two
C. albicans
strains isolated from the clinical specimens were studied using two models of vaginal candidiasis to determine how closely these models mimicked the clinical specimens at the level of gene expression. ALS gene expression patterns in a murine vaginitis model were identical to those from the clinical specimens. Expression of more ALS genes was detected in specimens collected 7 days after infection compared to those collected at 4 days. Similar patterns of ALS gene expression were observed when the three
C. albicans
strains were tested in the reconstituted human vaginal epithelium model. In this model, expression of
ALS4
,
ALS5
,
ALS6
, and
ALS7
was least frequently detected. Negative or weakened signals for
ALS4
expression were observed at early time points, suggesting that
ALS4
expression, which was strong in the inoculum cells, was down-regulated upon contact of
C. albicans
with vaginal epithelial cells in this model. The data presented here support the conclusion of host-site-specific influences on ALS gene expression and validate the use of the experimental models for evaluating the phenotype of
als
/
als
mutant strains.
GastricHelicobacterInfection Induces a Th2 Phenotype but Does Not Elevate Serum Cholesterol in Mice Lacking Inducible Nitric Oxide Synthase
Authors: Ihrig Melanie , Whary Mark T. , Dangler Charles A. , Fox James G. 
Published: February 2005

ABSTRACTPersistentHelicobacter felisinfection in (C57BL/6 × 129SvEv)F1mice induces chronic gastritis. Expression of inducible nitric oxide synthase (iNOS) is upregulated in response toHelicobacterinfection. In this study, 20 10-week-old iNOS−/−mice and 20 wild-type [(C57BL/6 × 129SvEv)F1] mice were infected withH. felisby oral gavage and were assessed histologically and serologically at 32 weeks postinfection. Equal numbers of uninfected controls were sham inoculated. The mice were scored for severity of gastric inflammation, hyperplasia, glandular atrophy, and mucous metaplasia in the corpus and for the level of helicobacter colonization. The immunoglobulin G1 (IgG1), IgG2a, and IgG2c antibody responses toH. feliswere determined. As a secondary measure, serum cholesterol levels were assessed. iNOS−/−mice have a propensity for increased serum cholesterol, and although controversial, several human epidemiologic studies have demonstrated an association betweenHelicobacterinfection and several risk factors for cardiovascular disease, including elevated serum cholesterol. Nevertheless, no differences in serum cholesterol levels were observed between theH. felis-infected and -uninfected iNOS−/−mice in this study. The uninfected animals had minimal to no gastric pathology. The gastric pathology scores for the infected animals were reduced significantly in the iNOS-deficient mice relative to those for the wild-type mice (allP< 0.01).Helicobacter-infected iNOS−/−mice had chronic lymphoid infiltration and negligible to mild glandular atrophy and mucous metaplasia in the fundic mucosa, whileH. felis-infected wild-type mice had severe atrophic and metaplastic mucosal changes. The atrophic gastritis in the infected wild-type mice, particularly the female mice, was also accompanied by greater granulocytic infiltration, antral hyperplasia, and diminished antral colonization, unlike that in the infected iNOS−/−mice. iNOS−/−mice developed significantly lower Th1-associated IgG2c antibody responses toH. felis(P< 0.0003); the Th2-associated IgG1 responses were similar (P= 0.09), suggesting a greater effect of the iNOS defect on Th1 responses.H. feliscolonization was significantly greater in the iNOS-deficient mice. These findings are indicative of an impaired Th1 component of theH. felis-induced inflammatory response when the influence of iNOS is removed.
HosA, a Member of the SlyA Family, Regulates Motility in Enteropathogenic
Escherichia coli
Authors: Ferrándiz Maria-José , Bishop Keith , Williams Paul , Withers Helen 
Published: February 2005

ABSTRACT

In enteropathogenic and enterohemorraghic
Escherichia coli
(EPEC and EHEC), two members of the SlyA family of transcriptional regulators have been identified as SlyA. Western blot analysis of the wild type and the corresponding
hosA
and
slyA
deletion mutants indicated that SlyA and HosA are distinct proteins whose expression is not interdependent. Of 27 different
E. coli
strains (EPEC, EHEC, enteroinvasive, enteroaggregative, uropathogenic, and commensal) examined, 14 were positive for both genes and proteins. To investigate
hosA
expression, a
hosA
::
luxCDABE
reporter gene fusion was constructed.
hosA
expression was significantly reduced in the
hosA
but not the
slyA
mutant and was influenced by temperature, salt, and pH. In contrast to SlyA, HosA did not activate the cryptic
E. coli
K-12 hemolysin ClyA. Mutation of
hosA
did not influence type III secretion, the regulation of the LEE1 and LEE4 operons, or the ability of E2348/69 to form attaching-and-effacing lesions on intestinal epithelial cells. HosA is, however, involved in the temperature-dependent positive control of motility on swim plates and regulates
fliC
expression and FliC protein levels. In electrophoretic mobility shift assays, purified HosA protein bound specifically to the
fliC
promoter, indicating that HosA directly modulates flagellin expression. While direct examination of flagellar structure and the motile behavior of individual
hosA
cells grown in broth culture at 30°C did not reveal any obvious differences,
hosA
mutants, unlike the wild type, clumped together, forming nonmotile aggregates which could account for the markedly reduced motility of the
hosA
mutant on swim plates at 30°C. We conclude that SlyA and HosA are independent transcriptional regulators that respond to different physicochemical cues to facilitate the environmental adaptation of
E. coli
.
Activities of
Pseudomonas aeruginosa
Effectors Secreted by the Type III Secretion System In Vitro and during Infection
Authors: Lee Vincent T. , Smith Roger S. , Tümmler Burkhard , Lory Stephen 
Published: February 2005

ABSTRACT

Pseudomonas aeruginosa
utilizes a number of distinct pathways to secrete proteins that play various roles during infection. These include the type II secretion system, which is responsible for the secretion of the majority of exoproducts into the surrounding environment, including toxins and degradative enzymes. In contrast, the type III secretion system mediates the delivery of protein effectors directly into the cytoplasm of the host cell. Using tissue culture assays and a mouse acute-pneumonia model, we have determined the contribution of each of the type III effectors during infection. In strain PAK, ExoS is the major cytotoxin required for colonization and dissemination during infection. ExoT confers protection of tissue culture cells from type III-dependent lysis, while ExoY seemed to have little effect on cytotoxicity. ExoU is over 100-fold more cytotoxic than ExoS. The cytotoxicity of type II secretion was determined following deletion of the genes for the more toxic type III secretion system. The participation of these secretion systems during lifelong colonization of cystic fibrosis (CF) patients is unclear. By comparing clonal strains from the same patient isolated at the initial onset of
P. aeruginosa
infection and more than a decade later, after chronic colonization has been established, we show that initial strains are more cytotoxic than chronic strains that have evolved to reduce type III secretion. Constitutive expression of genes for the type III secretion system restored ExoS secretion but did not always reestablish cytotoxicity, suggesting that CF strains accumulate a number of mutations to reduce bacterial toxicity to the host.
Age Alterations in Extent and Severity of Experimental Intranasal Infection withChlamydophila pneumoniaein BALB/c Mice
Authors: Little C. Scott , Bowe Andrew , Lin Richard , Litsky Jason , Fogel Robert M. , Balin Brian J. , Fresa-Dillon Kerin L. 
Published: February 2005

ABSTRACTThe intracellular bacteriumChlamydophila(“Chlamydia”)pneumoniaeis a pathogen for several respiratory diseases and may be a factor in the pathogenesis of chronic diseases of aging including atherosclerosis and Alzheimer's disease. We assessed whether aging is coupled with increased burden of infection in BALB/c mice after intranasal infection byC. pneumoniae. Six- and twenty-month-old BALB/c mice were infected intranasally with 5 × 104inclusion forming units (IFU) or 5 × 105IFU ofC. pneumoniae. Lung, brain, and heart tissue were analyzed for infectiousC. pneumoniaeand forChlamydophilaantigen by immunohistochemistry. At both doses, aging was associated with a decreased proportion of animals that cleared infection from the lung and greater burden of infectious organism within the lung. We observed dose-dependent spread to the heart/ascending aorta in animals infected withC. pneumoniae. In mice given 5 × 104IFU, spread to the heart by day 14 was only observed in old mice. By day 28, all animals inoculated with 5 × 104IFU showed evidence of spread to the heart, although higherC. pneumoniaetiters were observed in the hearts from old mice. In mice inoculated with 5 × 105IFU, spread ofC. pneumoniaeto the heart was evident by day 14, with no discernible age effect.C. pneumoniaewas also recovered from the central nervous system (brain and olfactory bulb) of all mice by day 28 postinfection, with higherC. pneumoniaetiters in old animals than in young animals. Our results suggest that infection withC. pneumoniaemay be more severe in old animals.
Neutrophil Responses toMycobacterium tuberculosisInfection in Genetically Susceptible and Resistant Mice
Authors: Eruslanov Evgenyi B. , Lyadova Irina V. , Kondratieva Tatiana K. , Majorov Konstantin B. , Scheglov Ilya V. , Orlova Marianna O. , Apt Alexander S. 
Published: February 2005

ABSTRACTThe role of neutrophils in tuberculosis (TB) resistance and pathology is poorly understood. Neutrophil reactions are meant to target the offending pathogen but may lead to destruction of the host lung tissue, making the defending cells an enemy. Here, we show that mice of the I/St strain which are genetically susceptible to TB show an unusually high and prolonged neutrophil accumulation in their lungs after intratracheal infection. Compared to neutrophils from more resistant A/Sn mice, I/St neutrophils display an increased mobility and tissue influx, prolonged lifespan, low expression of the CD95 (Fas) apoptotic receptor, relative resistance to apoptosis, and an increased phagocytic capacity for mycobacteria. Segregation genetic analysis in (I/St × A/Sn)F2hybrids indicates that the alleles of I/St origin at the chromosome 3 and 17 quantitative trait loci which are involved in the control of TB severity also determine a high level of neutrophil influx. These features, along with the poor ability of neutrophils to restrict mycobacterial growth compared to that of lung macrophages, indicate that the prevalence of neutrophils in TB inflammation contributes to the development of pathology, rather than protection of the host, and that neutrophils may play the role of a “Trojan horse” for mycobacteria.
Colonization and Inflammation Deficiencies in Mongolian Gerbils Infected byHelicobacter pyloriChemotaxis Mutants
Authors: McGee David J. , Langford Melanie L. , Watson Emily L. , Carter J. Elliot , Chen Yu-Ting , Ottemann Karen M. 
Published: February 2005

ABSTRACTHelicobacter pyloricauses disease in the human stomach and in mouse and gerbil stomach models. Previous results have shown that motility is critical forH. pylorito colonize mice, gerbils, and other animal models. The role of chemotaxis, however, in colonization and disease is less well understood. Two genes in theH. pylorichemotaxis pathway,cheYandtlpB, which encode the chemotaxis response regulator and a methyl-accepting chemoreceptor, respectively, were disrupted. ThecheYmutation was complemented with a wild-type copy ofcheYinserted into the chromosomalrdxAgene. ThecheYmutant lost chemotaxis but retained motility, while all other strains were motile and chemotactic in vitro. These strains were inoculated into gerbils either alone or in combination with the wild-type strain, and colonization and inflammation were assessed. While thecheYmutant completely failed to colonize gerbil stomachs, thetlpBmutant colonized at levels similar to those of the wild type. With thetlpBmutant, there was a substantial decrease in inflammation in the gerbil stomach compared to that with the wild type. Furthermore, there were differences in the numbers of each immune cell in thetlpB-mutant-infected stomach: the ratio of lymphocytes to neutrophils was about 8 to 1 in the wild type but only about 1 to 1 in the mutant. These results suggest that the TlpB chemoreceptor plays an important role in the inflammatory response while the CheY chemotaxis regulator plays a critical role in initial colonization. Chemotaxis mutants may provide new insights into the steps involved inH. pyloripathogenesis.
Profile of
Candida albicans-
Secreted Aspartic Proteinase Elicited during Vaginal Infection
Authors: Taylor Brad N. , Staib Peter , Binder Ayfer , Biesemeier Antje , Sehnal Miriam , Röllinghoff Martin , Morschhäuser Joachim , Schröppel Klaus 
Published: February 2005

ABSTRACT

Vaginal infections caused by the opportunistic yeast
Candida albicans
are a significant problem in women of child-bearing age. Several factors are recognized as playing a crucial role in the pathogenesis of superficial candidiasis; these factors include hyphal formation, phenotypic switching, and the expression of virulence factors, including a 10-member family of secreted aspartic proteinases. In the present investigation, we analyzed the secreted aspartic proteinase gene (
SAP
) expression profile of
C. albicans
that is elicited in the course of vaginal infection in mice and how this in vivo expression profile is associated with hyphal formation. We utilized two different genetic reporter systems that allowed us to observe
SAP
expression on a single-cell basis, a recombination-based in vivo expression technology and green fluorescent protein-expressing
Candida
reporter strains. Of the six
SAP
genes that were analyzed (
SAP1
to
SAP6
), only
SAP4
and
SAP5
were detectably induced during infection in this model. Expression of both of these genes was associated with hyphal growth, although not all hyphal cells detectably expressed
SAP4
and
SAP5. SAP5
expression was induced soon after infection, whereas
SAP4
was expressed at later times and in fewer cells compared with
SAP5
. These findings point to a link between morphogenetic development and expression of virulence genes during
Candida
vaginitis in mice, where host signals induce both hyphal formation and expression of
SAP4
and
SAP5
, but temporal gene expression patterns are ultimately controlled by other factors.