bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heterologous Expression ofTrypanosoma cruzi trans-Sialidase inLeishmania majorEnhances Virulence
Authors: Belen Carrillo M. , Gao Wenda , Herrera Macario , Alroy Joseph , Moore Jeffrey B. , Beverley Stephen M. , Pereira Miercio A. 
Published: July 2002

ABSTRACTEarlier studies showed that mice primed for a few hours with thetrans-sialidase (TS) ofTrypanosoma cruzi, the agent of Chagas' disease, become highly susceptible to trypanosomal infection. These studies suggest that TS affects parasite virulence independent of antigenic stimulation. Potentially, TS could enhance or reduce the virulence of heterologous microbes depending on the mechanism of TS action and on the type of immune response elicited by the particular parasite. We tested this hypothesis by expressing heterologous TS inLeishmania major, a protozoan parasite that causes cutaneous leishmaniasis and lacks TS and the TS product α2-3-linked sialic acid.Leishmaniacells transfected with aT. cruziTS expression construct made high levels of active enzyme, which was present in the promastigotes and shed into the extracellular milieu. TS expression did not affectL. majorbinding to and entry into cultured macrophages or its tropism for macrophage infection in vivo. However, TS-expressingL. majorexhibited elevated virulence in BALB/c mice, as determined by lesion progression, parasite numbers, and macro- and microscopic examination of cutaneous lesions. Several genetic tests proved that the enhanced virulence was directly attributable to TS expression. The results are consistent with TS functioning to sabotage the mouse immune system to confer a growth advantage onT. cruziand transgenicL. major. These data suggest that heterologous expression ofT. cruzivirulence factors inLeishmaniamay provide a new approach for dissecting their function in vivo.
Detection of 23 Immunogenic Pneumococcal Proteins Using Convalescent-Phase Serum
Authors: Zysk Gregor , Bongaerts Roger J. M. , ten Thoren Elke , Bethe Gesina , Hakenbeck Regine , Heinz Hans-Peter 
Published: July 2002

ABSTRACT

A genomic expression library of
Streptococcus pneumoniae
was screened with a convalescent-phase serum for immunoreactive proteins. Six known and 17 unknown pneumococcal proteins were detected. Five of the known proteins were surface-located virulence factors, and eight of the unknown proteins were putative membrane proteins.
Requirement for NF-κB in Transcriptional Activation of Monocyte Chemotactic Protein 1 byChlamydia pneumoniaein Human Endothelial Cells
Authors: Molestina Robert E. , Miller Richard D. , Lentsch Alex B. , Ramirez Julio A. , Summersgill James T. 
Published: July 2002

ABSTRACTInfection withChlamydia pneumoniae, a causative agent of acute and chronic respiratory diseases, has recently been implicated as a potential risk factor in atherosclerosis. Atherosclerotic lesions are characterized by monocyte infiltration, which may be regulated by the chemokine monocyte chemotactic protein 1 (MCP-1). We have previously shown thatC. pneumoniaeinfection stimulates MCP-1 production in human endothelial cells, an event which may be specific to this species ofChlamydia, sinceChlamydia trachomatisinfection fails to induce this response. To examine the underlying mechanisms by whichC. pneumoniaeinfection induces MCP-1 production in endothelial cells, the present study investigated the role of transcription factor NF-κB in MCP-1 mRNA expression. Human umbilical vein endothelial cells (HUVEC) were infected with the coronary isolateC. pneumoniaeA-03 or withC. trachomatisL2, and MCP-1 mRNA expression was assessed after different periods of infection by reverse transcription-PCR. Expression of MCP-1 mRNA inC. pneumoniae-infected HUVEC was significantly elevated as early as 1 h postinfection and increased dramatically by 12 and 24 h compared to baseline controls. Nuclear translocation of NF-κB occurred by 30 min of infection, as determined by electrophoretic mobility shift assays and immunofluorescence staining. Treatment ofC. pneumoniae-infected HUVEC with parthenolide, a specific inhibitor of NF-κB activation, suppressed MCP-1 mRNA expression. In contrast, infection withC. trachomatisL2 did not induce MCP-1 mRNA in infected HUVEC and failed to activate NF-κB. Results from this study demonstrate a requirement for NF-κB activation in stimulation of MCP-1 gene expression byC. pneumoniaein human endothelial cells. Furthermore, the data suggest that, within the genusChlamydia, functionally distinct signaling pathways leading to NF-κB activation are utilized byC. pneumoniaein endothelial cells during infection.
Adaptive Immunity againstListeria monocytogenesin the Absence of Type I Tumor Necrosis Factor Receptor p55
Authors: White Douglas W. , Badovinac Vladimir P. , Fan Xin , Harty John T. 
Published: July 2002

ABSTRACTTumor necrosis factor (TNF) and the type I TNF receptor (TNFRI), p55, are critical for resistance against primary infections with the intracellular bacterial pathogenListeria monocytogenes. Importantly, however, susceptibility to primary listeriosis in cytokine-deficient mice does not preclude the development or expression of effective adaptive immunity against virulentL. monocytogenes. We used TNFRI−/−mice to study adaptive antilisterial immunity in the absence of interactions between TNF and TNFRI. Our experiments indicate that TNFRI−/−mice survive and clear high-dose challenges with an attenuated strain ofL. monocytogenesthat is incapable of cell-to-cell spread. Furthermore, TNFRI−/−mice immunized with attenuatedL. monocytogenesgo on to develop potent adaptive immunity to subsequent high-dose challenges with virulentL. monocytogenes. Interestingly, CD8+T-cell depletion in vivo inhibits immunity toL. monocytogenesin the spleen but not in the liver of TNFRI−/−mice. The adaptive immune response in these animals is characterized by activation of listeriolysin O-specific CD8+T cells, which are capable of transferring antilisterial immunity to naive wild-type C57BL/6 host mice. These experiments demonstrate the development and expression of potent CD8+T-cell-mediated antilisterial immunity in the absence of TNFRI.
Role of Monocytes in Experimental
Staphylococcus aureus
Endocarditis
Authors: Veltrop Marcel H. A. M. , Bancsi Maurice J. L. M. F. , Bertina Rogier M. , Thompson Jan 
Published: July 2002

ABSTRACT

In the pathogenesis of bacterial endocarditis (BE), the clotting system plays a cardinal role in the formation and maintenance of the endocardial vegetations. The extrinsic pathway is involved in the activation of the coagulation pathway with tissue factor (TF) as the key protein.
Staphylococcus aureus
is a frequently isolated bacterium from patients with BE. We therefore investigated whether
S. aureus
can induce TF activity (TFA) on fibrin-adherent monocytes, used as an in vitro model of BE. We also assessed in vivo in rabbits with catheter induced vegetations, the effect of
S. aureus
infection on vegetational TFA. In vitro experiments showed that adherent
S. aureus
induced TFA on fibrin-adherent monocytes which was optimal at a bacterium/monocyte ratio of 1 to 1. Monocyte damage occurred when this ratio exceeded 4 to 1 (visually) or 6 to 1 (propidium iodide influx) Consequently, TFA decreased. In vivo
S. aureus
led to very high bacterial numbers in the vegetations and a significant increase of their weight. However, TFA of infected vegetations was the same as of sterile ones. This may be due to the high bacteria to monocyte ratio as well as bacterium-induced monocyte damage. Teicoplanin treatment of infected rabbits reduced bacterial numbers in the blood and in the vegetations. Two-day treatment resulted in an increase of vegetational TFA, but after four-day treatment vegetational TFA dropped, most probably due to a suboptimal bacterium/monocyte ratio.
S. aureus
endocarditis in etoposide (Vepesid)-treated rabbits, leading to a selective monocytopenia, caused a rapid death of the animals. In these rabbits no vegetations were found at all. We conclude that, like
Streptococcus sanguis
and
Staphylococcus epidermidis
,
S. aureus
is able to induce TFA in fibrin-adherent blood monocytes. In addition, monocytes have a protective effect during the course of
S. aureus
endocarditis.
Surface-Expressed Mig Protein ProtectsStreptococcus dysgalactiaeagainst Phagocytosis by Bovine Neutrophils
Authors: Song Xin-Ming , Perez-Casal Jose , Bolton Alexandra , Potter Andrew A. 
Published: July 2002

ABSTRACTThemiggene ofStreptococcus dysgalactiae, a major bovine mastitis pathogen, encodes two plasma protein-binding receptors, α2-macroglobulin (α2-M) and immunoglobulin G (IgG). In this study, themiggene from oneS. dysgalactiaeisolate was cloned and expressed inEscherichia coli. The IgG receptor region encoded bymigwas conserved in 16S. dysgalactiaestrains. An isogenicmigmutant was constructed by allele replacement mutagenesis of the wild-type gene inS. dysgalactiae. The IgG-binding activity was lost in themigmutant strain, whereas the α2-M receptor activity was still expressed but was detected only in the culture supernatant. In flow cytometry phagocytosis and bacterial-colony-counting bactericidal assays, the wild-type strain was found to be significantly more resistant to phagocytosis and killing by bovine neutrophils (PMNs) than themigmutant strain when bacteria were preincubated with bovine serum. We therefore speculate that the Mig protein ofS. dysgalactiaeplays a role in virulence of the bacteria by binding to the plasma protein α2-M or IgG and thus preventing phagocytosis by bovine PMNs.
Susceptibilities ofCryptococcus neoformansStrains to Platelet Binding In Vivo and to the Fungicidal Activity of Thrombin-Induced Platelet Microbicidal Proteins In Vitro
Authors: Nail S. , Robert R. , Dromer F. , Marot-Leblond A. , Senet J. M. 
Published: July 2002

ABSTRACTIn this study we investigated the interactions between capsular and acapsular strains ofCryptococcus neoformansand blood platelets. In vivo microscopic observation of blood samples from mice inoculated withC. neoformansyeast cells demonstrated that encapsulated and nonencapsulated yeast cells disappeared quickly from the bloodstream and that platelets were attached solely to yeast cells of the nonencapsulated strains. In vitro we observed that only the acapsular strains were susceptible to the fungicidal activity of thrombin-induced platelet microbicidal proteins.
In Vitro Investigation of Host Resistance toToxoplasma gondiiInfection in Microglia of BALB/c and CBA/Ca Mice
Authors: Freund Yvonne R. , Zaveri Naunihal T. , Javitz Harold S. 
Published: July 2002

ABSTRACTToxoplasmic encephalitis (TE) is a life-threatening disease of immunocompromised individuals and has increased in prevalence as a consequence of AIDS. TE has been modeled in inbred mice, with CBA/Ca mice being susceptible and BALB/c mice resistant to the development of TE. To better understand the innate mechanisms in the brain that play a role in resistance to TE, nitric oxide (NO)-dependent and NO-independent mechanisms were examined in microglia from BALB/c and CBA/Ca mice and correlated with the ability of these cells to inhibitToxoplasma gondiireplication. These parameters were measured 48 h after stimulation with lipopolysaccharide (LPS) gamma interferon (IFN-γ), tumor necrosis factor alpha (TNF-α), or combinations of these inducers inT. gondii-infected microglia isolated from newborn mice. CBA/Ca microglia consistently produced less NO than did BALB/c microglia after stimulation with LPS or with IFN-γ plus TNF-α, and they inhibitedT. gondiireplication significantly less than did BALB/c microglia. Cells of both strains treated with IFN-γ alone significantly inhibited uracil incorporation byT. gondii, andNG-monomethyl-l-arginine (NMMA) treatment did not reverse this effect. In cells treated with IFN-γ in combination with other inducers, NMMA treatment resulted in only partial recovery ofT. gondiireplication. This IFN-γ-dependent inhibition of replication was not due to generation of reactive oxygen species or to increased tryptophan degradation. These data suggest that NO production and an IFN-γ-dependent mechanism contribute to the inhibition ofT. gondiireplication after in vitro stimulation with IFN-γ plus TNF-α or with LPS. Differences in NO production but not in IFN-γ-dependent inhibition ofT. gondiireplication were observed between CBA/Ca and BALB/c microglia.
Interference between Host Resistance toListeria monocytogenesInfection and Ovalbumin-Induced Allergic Responses in Mice
Authors: Mizuki Daisuke , Miura Tomisato , Sasaki Sanae , Mizuki Mayuko , Madarame Hiroo , Nakane Akio 
Published: July 2002

ABSTRACTListeria monocytogenespromotes the induction of the T-helper 1 (Th1) cell response, while ovalbumin (OVA) induces a Th2 cell response and allergic reactions, such as airway hyperreactivity and immunoglobulin E (IgE) production. When mice were immunized with OVA on day 7 afterL. monocytogenesinfection, eosinophilia in bronchoalveolar lavage and the production of total IgE, OVA-specific IgE, interleukin-4 (IL-4), and IL-5 in the circulation were markedly suppressed. Cytokine responses, including IL-4, IL-5, IL-10, IL-13, and gamma interferon, to OVA were decreased in the spleen cell cultures obtained from OVA-immunized mice that had been infected withL. monocytogenes. Conversely, when OVA-immunized mice were infected withL. monocytogenes, conversion from the nonlethal infection to the lethal infection occurred. Host resistance toL. monocytogenesinfection in OVA-immunized mice was enhanced by the administration of anti–IL-10 monoclonal antibody. The present study indicates that striking interference is observed between Th1-inducingL. monocytogenesinfection and Th2-driven OVA-induced airway hyperreactivity.
Regulation of Matrix Metalloproteinase Expression in Endothelial Cells by Heat-Inactivated
Streptococcus pneumoniae
Authors: Michel Uwe , Zobotke Rita , Mäder Michael , Nau Roland 
Published: July 2002

ABSTRACT

Matrix metalloproteinases (MMPs) may contribute to an impaired endothelial layer in several diseases. We examined the effect of heat-inactivated
Streptococcus pneumoniae
R6 on MMP-2 and MMP-9 release by cultured aortic and brain capillary endothelial cells. Treatment with heat-inactivated
S. pneumoniae
caused an increased release of MMP-2 by both cell types.
Transcriptional Regulation of Divergent Capsule Biosynthesis and Transport Operon Promoters in Serogroup B
Neisseria meningitidis
Authors: Tzeng Yih-Ling , Swartley John S. , Miller Yoon K. , Nisbet Rachel E. , Liu Li-Jun , Ahn Jay H. , Stephens David S. 
Published: July 2002

ABSTRACT

The clinically important serogroups B, C, Y, and W-135 of
Neisseria meningitidis
produce sialic acid capsules that are critical in pathogenesis. In each of these serogroups, the capsule transport (
ctrABCD
) and capsule biosynthesis (
synABCD
) operons are divergently transcribed from putative promoters located in a 134-bp intergenic region (J. S. Swartley, J. H. Ahn, L. J. Liu, C. M. Kahler, and D. S. Stephens, J. Bacteriol. 178:4052–4059, 1996). In this study we further assessed the role of the intergenic sequence in the transcriptional regulation of the sialic acid capsules of
N. meningitidis
. Insertional mutagenesis or deletions of the 134-bp sequence in the serogroup B meningococcal strain NMB resulted in a marked reduction or elimination of
ctrABCD
and
synABCD
transcription, with a concomitant loss of encapsulation. Chromosomal transcriptional
lacZ-ermC
reporter fusions of
syn
and
ctr
promoters were constructed through allelic exchange. Using these constructs, both operons were found to be constitutively transcribed in meningococci, the biosynthesis operon about fourfold higher than the transport operon. Both promoters showed increased activity during stationary-phase growth. In addition to the promoters, a 70-bp 5′ untranslated region (UTR) upstream of
synA
was found to have a direct repeat and an inverted repeat that overlapped three putative integration host factor binding sites. Mutation of this 70-bp UTR and of the direct repeat upregulated both
syn
and
ctr
transcription. Regulation through the
synA
UTR was absent in a K1
Escherichia coli
strain that produces identical capsular polysaccharide, implicating species-specific regulation. Meningococcal sialic acid capsule expression is initiated by divergent promoters in a 134-bp intergenic region, is repressed at the transcriptional level by the 5′ UTR of
synA
, is increased during stationary-phase growth, and shows species-specific regulation. Transcriptional regulation is another important control point for sialic capsule expression in
N. meningitidis
.
By Releasing ADP,Acanthamoeba castellaniiCauses an Increase in the Cytosolic Free Calcium Concentration and Apoptosis in Wish Cells
Authors: Mattana A. , Tozzi M. G. , Costa M. , Delogu G. , Fiori P. L. , Cappuccinelli P. 
Published: July 2002

ABSTRACTThe role played by soluble molecules that may participate in acanthamoebal cytopathogenicity has yet to be fully characterized. We demonstrate here thatAcanthamoeba castellaniitrophozoites constitutively release ADP in the medium. Cell-free supernatants prepared fromA. castellanii, by interaction with specific P2y2purinoceptors expressed on the Wish cell membrane, caused a biphasic rise in [Ca2+]i, extensive cell membrane blebbing, cytoskeletal disorganization, and the breakdown of nuclei. Cell damage induced by amoebic supernatants was blocked by the P2y2inhibitor Suramin. The same results were found in Wish cells exposed to purified ADP. These findings suggest that pathogenic free-livingA. castellaniimay have a cytopathic effect on human epithelial cells through ADP release, by a process that begins with a rise of cytosolic free-calcium concentration, and culminates in apoptosis.
Development of a Gene Inactivation System for
Bacteroides forsythus
: Construction and Characterization of a BspA Mutant
Authors: Honma Kiyonobu , Kuramitsu Howard K. , Genco Robert J. , Sharma Ashu 
Published: July 2002

ABSTRACT

Bacteroides forsythus
is a gram-negative anaerobic bacterium associated with periodontitis. The
bspA
gene encoding a cell surface associated leucine-rich repeat protein (BspA) involved in adhesion to fibronectin and fibrinogen was recently cloned from this bacterium in our laboratory. We now describe the construction of a BspA-defective mutant of
B. forsythus
. This is the first report describing the generation of a specific gene knockout mutant of
B. forsythus
, and this procedure should be useful in establishing the identity of virulence-associated factors in these organisms.
Mycoplasma pneumoniae
P1 Type 1- and Type 2-Specific Sequences within the P1 Cytadhesin Gene of Individual Strains
Authors: Dorigo-Zetsma J. Wendelien , Wilbrink Berry , Dankert Jacob , Zaat Sebastian A. J. 
Published: July 2002

ABSTRACT

Mycoplasma pneumoniae
strains traditionally are divided into two types, based on sequence variation in the P1 gene. Recently, however, we have identified 8 P1 subtypes by restriction fragment length polymorphism analysis. In the present study the P1 gene sequences of three P1 type 1 and two P1 type 2
M. pneumoniae
strains were analyzed. A new P1 gene sequence in a type 1 strain with partial similarity to a recently reported variable region in the P1 gene of an
M. pneumoniae
type 2 strain (T. Kenri, R. Taniguchi, Y. Sasaki, N. Okazaki, M. Narita, K. Izumikawa, M. Umetsu, and T.Sasaki, Infect. Immun. 67:4557–4562, 1999) was identified. In addition, the P1 gene of the type 1 strain contained another region with nucleotide polymorphisms identical to a stretch in the P1 gene of one of our type 2 strains. These findings indicate that recombination between sequences specific for P1 type 1 and type 2 had occurred and that P1 type 1 and type 2 hybrid sequences can be present within the P1 gene of an individual strain. Identical or nearly identical variable P1 gene sequences were present in several repetitive regions outside the P1 gene locus in the genome of
M. pneumoniae
strain M129, implying recombination as a mechanism for generation of the P1 gene variation. Additionally, in the P1 gene sequences of four of the five strains studied, single-nucleotide polymorphisms different from the previously reported P1 type 1 and 2 characteristic sequences were identified. The polymorphic sites are candidate targets for genotyping of
M. pneumoniae
by direct sequencing of amplicons from clinical specimens.
Distinct Proinflammatory Host Responses to
Neisseria gonorrhoeae
Infection in Immortalized Human Cervical and Vaginal Epithelial Cells
Authors: Fichorova Raina Nakova , Desai Pragnya Jasvantrai , Gibson Frank C. , Genco Caroline Attardo 
Published: July 2002

ABSTRACT

In this study we utilized immortalized morphologically and functionally distinct epithelial cell lines from normal human endocervix, ectocervix, and vagina to characterize gonococcal epithelial interactions pertinent to the lower female genital tract. Piliated, but not nonpiliated,
N. gonorrhoeae
strain F62 variants actively invaded these epithelial cell lines, as demonstrated by an antibiotic protection assay and confocal microscopy. Invasion of these cells by green fluorescent protein-expressing gonococci was characterized by colocalization of gonococci with F actin, which were initially detected 30 min postinfection. In all three cell lines, upregulation of interleukin 8 (IL-8) and IL-6, intercellular adhesion molecule 1 (CD54), and the nonspecific cross-reacting antigen (CD66c) were detected 4 h after infection with piliated and nonpiliated gonococci. Furthermore, stimulation of all three cell lines with gonococcal whole-cell lysates resulted in a similar upregulation of IL-6 and IL-8, confirming that bacterial uptake is not essential for this response. Increased levels of IL-1 were first detected 8 h after infection with gonococci, suggesting that the earlier IL-8 and IL-6 responses were not mediated through the IL-1 signaling pathway. The IL-1 response was limited to cultures infected with piliated gonococci and was more vigorous in the endocervical epithelial cells. The ability of gonococci to stimulate distinct proinflammatory host responses in these morphologically and functionally different compartments of the lower female genital tract may contribute directly to the inflammatory signs and symptoms characteristic of disease caused by
N. gonorrhoeae
.
Essential Role of Interleukin-12 (IL-12) and IL-18 for Gamma Interferon Production Induced by Listeriolysin O in Mouse Spleen Cells
Authors: Nomura Takamasa , Kawamura Ikuo , Tsuchiya Kohsuke , Kohda Chikara , Baba Hisashi , Ito Yutaka , Kimoto Terumi , Watanabe Isao , Mitsuyama Masao 
Published: July 2002

ABSTRACTThe mechanism of gamma interferon (IFN-γ) production induced by listeriolysin O (LLO), a cytolytic virulence factor ofListeria monocytogenes, was analyzed with special reference to the involvement of macrophage-derived cytokines in spleen cells of mice. LLO purified from the culture supernatant ofL. monocytogeneswas capable of inducing a high level of IFN-γ when its cytolytic activity was blocked by cholesterol treatment. The IFN-γ-inducing ability of LLO was not dependent on possibly contaminating lipopolysaccharide. Depletion of CD11b+cells resulted in a profound decrease in IFN-γ production in response to LLO stimulation. Negative selection also suggested the contribution of DX5+cells in IFN-γ production. Reverse transcription-PCR revealed that expression of interleukin-12 (IL-12) p35 and p40 was induced by LLO but that the IL-18 mRNA level in the CD11b+fraction of spleen cells was unchanged. There was no change in the expression of the IFN-γ-inducing cytokine genes in the CD11b−fraction. Neutralization of IL-12 and IL-18 in culture abolished the IFN-γ production almost completely. Spleen cells from IL-12- or IL-18-deficient mice never produced IFN-γ after stimulation with LLO. These results clearly indicated that LLO, a well-known virulence factor ofL. monocytogenes, is capable of inducing IFN-γ from NK cells through induction of IL-12 and IL-18 from macrophages. LLO appeared to play essential roles, not only as a bacterial virulence factor but also as a bacterial modulin in the immune response of the host.