bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developmental Expression of Two Spore Wall Proteins during Maturation of the Microsporidian
Encephalitozoon intestinalis
Authors: Hayman J. Russell , Hayes Stanley F. , Amon Joseph , Nash Theodore E. 
Published: July 2002

ABSTRACT

Microsporidia are intracellular eukaryotes that infect many animals and cause opportunistic infections in AIDS patients. The disease is transmitted via environmentally resistant spores. Two spore wall constituents from the microsporidian
Encephalitozoon intestinalis
were characterized. Spore wall protein 1 (SWP1), a 50-kDa glycoprotein recognized by monoclonal antibody (MAb) 11B2, was detected in developing sporonts and at low levels on the surfaces of mature spores. In contrast, SWP2, a 150-kDa glycoprotein recognized by MAb 7G7, was detected on fully formed sporonts and was more abundant on mature spores than SWP1. Nevertheless, the SWPs appeared to be complexed on the surfaces of mature spores. SWP1 and SWP2 are similar at the DNA and protein levels and have 10 conserved cysteines in the N-terminal domain, suggesting similar secondary structures. The C-terminal domain of SWP2 has a unique region containing 50 repeating 12- or 15-amino-acid units that lacks homology to known protein motifs. Antibodies from mice infected with
E. intestinalis
recognized SWP1 and SWP2. The characterization of two immunogenic SWPs from
E. intestinalis
will allow the study of exospore structure and function and may lead to the development of useful tools in the diagnosis and treatment of microsporidiosis.
DNA Vaccines Expressing a Fusion Product of Outer Surface Proteins A and C fromBorrelia burgdorferiInduce Protective Antibodies Suitable for Prophylaxis but Not for Resolution of Lyme Disease
Authors: Wallich Reinhard , Siebers Annette , Jahraus Oliver , Brenner Christiane , Stehle Thomas , Simon Markus M. 
Published: July 2002

ABSTRACTDNA vaccines encoding the outer surface protein A (OspA) ofBorrelia burgdorferihave been shown to induce protective humoral responses capable of preventing but not curing infection in mice. Subsequent studies showed that an established infection or disease could be resolved by passive transfer of antibodies to OspC. In the present study, DNA vaccines encoding either the OspC antigen alone or fused to OspA and under the transcriptional control of the human elongation factor 1α promoter were evaluated for their protective and/or curative potential. In contrast toospA-containing plasmids, none of the six constructs withospCalone were immunogenic in vivo, independent of whether they contained promoter or leader sequences fromospAand/orospC, or alternatively, the signal sequence of the human tissue plasminogen activator. Solely, a DNA vaccine encoding an OspA-OspC fusion product led to expression of the respective polypeptide chain in transfected cells in vitro and to the induction of OspA- and OspC-specific antibodies in vivo. Immune sera raised against the OspA-OspC fusion product conveyed full protection against subsequent infection, most probably via OspA-specific antibodies, but were unable to resolve infection.
Immunohistochemical Analysis of Cellular Infiltrate and Gamma Interferon, Interleukin-12, and Inducible Nitric Oxide Synthase Expression in Leprosy Type 1 (Reversal) Reactions before and during Prednisolone Treatment
Authors: Little David , Khanolkar-Young Saroj , Coulthart Anne , Suneetha Sujai , Lockwood Diana N. J. 
Published: July 2002

ABSTRACTThe effects of prednisolone treatment on the cellularity and cytokine (gamma interferon, interleukin-12, and inducible nitric oxide synthase) profiles of leprosy skin type 1 (reversal) reactions were studied using immunohistochemistry. Skin biopsies were taken from 15 patients with leprosy type 1 (reversal) reactions at days 0, 7, 28, and 180 after the start of steroid treatment. Prednisolone treatment had little effect at day 7, but by day 28 significant decreases were found in cytokine levels. Some patients maintained cytokine production at days 28 and 180. These results illustrate the strong Th1 profile of type 1 reactional lesions, the slow response to steroid therapy, and continuing activity at 180 days.
Calprotectin Expression Inhibits Bacterial Binding to Mucosal Epithelial Cells
Authors: Nisapakultorn Kanokwan , Ross Karen F. , Herzberg Mark C. 
Published: July 2002

ABSTRACTSquamous mucosal epithelial cells constitutively express calprotectin in the cytoplasm. To study how this antimicrobial protein complex confers epithelial resistance to invading bacteria, an epithelial cell line was stably transfected to express the calprotectin complex. Cells expressing calprotectin resist invasion byListeria monocytogenesandSalmonella entericaserovar Typhimurium. Calprotectin expression was accompanied by altered actin organization, increased α3 integrin expression, and spreading cell morphology. In this study, we assessed whether calprotectin expression affects bacterial binding and uptake. Threefold-fewerListeriaorganisms bound to the surfaces of calprotectin-expressing cells, and 10-fold fewer were localized intracellularly by immunofluorescence. Similarly, fewerSalmonellaorganisms bound to cells expressing calprotectin. Calprotectin-expressing and sham-transfected cells showed similar levels of expression of surface E-cadherin and intracellular adhesion molecule 1 (ICAM-1) by flow cytometry. Calprotectin-expressing transfectants expressed calprotectin on the cell surface as well as in the cytosol. In conclusion, two bacterial pathogens showed reduced binding to calprotectin-expressing epithelial cells. Calprotectin-expressing cells appeared to have internalized disproportionately fewerListeriaorganisms, suggesting that reduced binding and translocation supplemented direct antimicrobial effects in calprotectin-expressing cells.
Expression and Functional Properties of the
Streptococcus intermedius
Surface Protein Antigen I/II
Authors: Petersen F.C. , Pasco S. , Ogier J. , Klein J. P. , Assev S. , Scheie A. A. 
Published: July 2002

ABSTRACT

Streptococcus intermedius
is associated with deep-seated purulent infections. In this study, we investigated expression and functional activities of antigen I/II in
S. intermedius
. The
S. intermedius
antigen I/II appeared to be cell surface associated, with a molecular mass of approximately 160 kDa. Northern blotting indicated that the
S. intermedius
NCTC 11324 antigen I/II gene was transcribed as a monocistronic message. Maximum expression was seen during the early exponential phase. Insertional inactivation of the antigen I/II gene resulted in reduced hydrophobicity during early exponential phase, whereas no effect was detected during mid- and late exponential phases. Binding to human fibronectin and laminin was reduced in the isogenic mutant, whereas binding to human collagen types I and IV and to rat collagen type I was not significant for either the wild type or the mutant. Compared to the wild type, the capacity of the isogenic mutant to induce interleukin 8 (IL-8) release by THP-1 monocytic cells was significantly reduced. The results indicate that the
S. intermedius
antigen I/II is involved in adhesion to human receptors and in IL-8 induction.
Heterogeneity of WildLeishmania majorIsolates in Experimental Murine Pathogenicity and Specific Immune Response
Authors: Kébaı̈er C. , Louzir H. , Chenik M. , Salah A. Ben , Dellagi K. 
Published: July 2002

ABSTRACTVirulence variability was investigated by analyzing the experimental pathogenicity of 19Leishmania majorstrains in susceptible BALB/c mice. Twelve strains were isolated from Tunisian patients with zoonotic cutaneous leishmaniasis; seven strains were isolated in Syria (n= 1), Saudi Arabia (n= 2), Jordan (n= 2), or Israel (n= 2). BALB/c mice were injected in the hind footpad with 2 × 106amastigotes of the various isolates, and lesion progression was recorded weekly for 9 weeks. Interleukin-4 (IL-4) and gamma interferon (IFN-γ) production of lymph node mononuclear cells activated in vitro with parasite antigens were evaluated 5 weeks after infection. We show that disease progression induced by differentL. majorisolates was largely heterogeneous although reproducible results were obtained when using the same isolate. Interestingly, isolates from the Middle East induced a more severe disease than did the majority of Tunisian isolates. Strains with the highest virulence tend to generate more IL-4 and less IFN-γ in vitro at week 5 postinfection as well as higher levels of early IL-4 mRNA in the lymph node draining the inoculation site at 16 h postinfection. These results suggest thatL. majorisolates from the field may differ in virulence, which influences the course of the disease induced in mice and the type of immune response elicited by the infected host.
Salmonella enterica
Serovar Gallinarum Requires the
Salmonella
Pathogenicity Island 2 Type III Secretion System but Not the
Salmonella
Pathogenicity Island 1 Type III Secretion System for Virulence in Chickens
Authors: Jones Michael A. , Wigley Paul , Page Kerrie L. , Hulme Scott D. , Barrow Paul A. 
Published: July 2002

ABSTRACT

Salmonella enterica
serovar Gallinarum is a host-specific serotype that causes the severe systemic disease fowl typhoid in domestic poultry and a narrow range of other avian species but rarely causes disease in mammalian hosts. Specificity of the disease is primarily at the level of the reticuloendothelial system, but few virulence factors have been described other than the requirement for an 85-kb virulence plasmid. In this work, by making functional mutations in the type III secretion systems (TTSS) encoded by
Salmonella
pathogenicity island 1 (SPI-1) and SPI-2, we investigated the role of these pathogenicity islands in interactions between
Salmonella
serovar Gallinarum and avian cells in vitro and the role of these pathogenicity islands in virulence in chickens. The SPI-1 mutant showed decreased invasiveness into avian cells in vitro but was unaffected in its ability to persist within chicken macrophages. In contrast the SPI-2 mutant was fully invasive in nonphagocytic cells but failed to persist in macrophages. In chicken infections the SPI-2 mutant was attenuated while the SPI-1 mutant showed full virulence. In oral infections the SPI-2 mutant was not observed in the spleen or liver, and following intravenous inoculation it was cleared rapidly from these sites. SPI-2 function is required by
Salmonella
serovar Gallinarum for virulence, primarily through promoting survival within macrophages allowing multiplication within the reticuloendothelial system, but this does not preclude the involvement of SPI-2 in uptake from the gut to the spleen and liver. SPI-1 appears to have little effect on virulence and survival of
Salmonella
serovar Gallinarum in the host.
Hydrolysis of Interleukin-12 byPorphyromonas gingivalisMajor Cysteine Proteinases May Affect Local Gamma Interferon Accumulation and the Th1 or Th2 T-Cell Phenotype in Periodontitis
Authors: Yun Peter L. W. , Decarlo Arthur A. , Collyer Charles , Hunter Neil 
Published: July 2002

ABSTRACTPorphyromonas gingivaliscysteine proteinases (gingipains) have been associated with virulence in destructive periodontitis, a disease process variously considered to represent an unregulated stimulation of either T helper type 1 (Th1)- or Th2-type cells. Critical in maintaining Th1 activity is the response of T lymphocytes to environmental interleukin 12 (IL-12) in the form of up-regulation of gamma interferon (IFN-γ) production. Here we demonstrate that in the presence or absence of serum, gingipains were able to hydrolyze IL-12 and reduce the IL-12-induced IFN-γ production from CD4+T cells. However, the induction of IL-12 receptors on T cells by gingipains did not correlate with the enhancement of IFN-γ production. The gingipains cleaved IL-12 within the COOH-terminal region of the p40 and p35 subunit chains, which leads to IL-12 inactivity, whereas IL-2 in these assays was not affected. Inactivation of IL-12 by the gingipains could disrupt the cytokine balance or favor Th2 activities in the progression of periodontitis.
Regulation of
Staphylococcus aureus
Capsular Polysaccharide Expression by
agr
and
sarA
Authors: Luong Thanh , Sau Subrata , Gomez Marisa , Lee Jean C. , Lee Chia Y. 
Published: July 2002

ABSTRACT

This study addresses the regulation of
Staphylococcus aureus
type 8 capsular polysaccharide (CP8) expression by the global regulators
agr
and
sarA
. We analyzed CP8 production,
cap8
-specific mRNA synthesis, and
blaZ
reporter gene activities of the transcriptional and translational fusions in strain Becker and its
agr
,
sarA
, and
agr-sarA
isogenic mutants during different phases of bacterial growth. In the wild-type strain,
cap8
mRNA was undetectable until the mid-logarithmic phase of growth, whereas CP8 production was undetectable until 2 h later, at the onset of stationary phase. The delay most likely reflects the time needed for completing CP8 synthesis resulting from translation of
cap8
mRNA. The
agr
mutation caused drastic reductions in CP8 production and
cap8
gene transcription, suggesting that
agr
is a major positive regulator of CP8 expression. The results of gene fusion studies indicated that regulation by
agr
is exerted at the transcriptional level. In contrast, the
sarA
mutation caused only a slight reduction in
cap8
mRNA synthesis and reporter gene activities. By comparing CP8 production and
cap8
transcription, we observed that
sarA
affected CP8 production both trancriptionally and posttranslationally. We showed that
agr
was a major activator for
cap
gene expression not only in type 8 strain Becker but also in strains representing the four
agr
groups.
Expression of Indoleamine 2,3-Dioxygenase, Tryptophan Degradation, and Kynurenine Formation during In Vivo Infection withToxoplasma gondii: Induction by Endogenous Gamma Interferon and Requirement of Interferon Regulatory Factor 1
Authors: Silva Neide M. , Rodrigues Cibele V. , Santoro Marcelo M. , Reis Luiz F. L. , Alvarez-Leite Jacqueline I. , Gazzinelli Ricardo T. 
Published: July 2002

ABSTRACTThe induction of indoleamine 2,3-dioxygenase (INDO) expression and the tryptophan (Trp)-kynurenine (Kyn) metabolic pathway during in vivo infection withToxoplasma gondiiwas investigated. Decreased levels of Trp and increased formation of Kyn were observed in the lungs, brain, and serum from mice infected withT. gondii. Maximal INDO mRNA expression and enzyme activity were detected in the lungs at 10 to 20 days postinfection. Further, the induction of INDO mRNA expression, Trp degradation and Kyn formation were completely absent in tissues from mice deficient in IFN-γ (IFN-γ−/−) or IFN regulatory factor -1 (IRF-1−/−). These findings indicate the important role of endogenous IFN-γ and IRF-1 in the in vivo induction of the Trp-Kyn metabolic pathway during acute infection withT. gondii. In contrast, expression of INDO mRNA and its activity was preserved in the tissues of TNF-receptor p55- or inducible nitric oxide synthase-deficient mice infected withT. gondii. Together with the results showing the extreme susceptibility of the IFN-γ−/−and the IRF-1−/−mice to infection withT. gondii, our results indicate a possible involvement of INDO and Trp degradation in host resistance to early infection with this parasite.
Temporal Expression of the
Candida albicans
Genes
CHK1
and
CSSK1
, Adherence, and Morphogenesis in a Model of Reconstituted Human Esophageal Epithelial Candidiasis
Authors: Li Dongmei , Bernhardt Joern , Calderone Richard 
Published: July 2002

ABSTRACT

We previously demonstrated that genes encoding a putative two-component histidine kinase (
CHK1
) or a response regulator (
CSSK1
) are each required for virulence in a murine model of hematogenously disseminated candidiasis and that strains with each gene deleted are also defective in morphogenesis under certain growth conditions. In the present study, the role of these two genes in the adherence to and colonization of reconstituted human esophageal tissue (RHE) is described. We compared strains of
Candida albicans
with deletions of
chk1
(strain CHK21) and
cssk1
(strain CSSK21) to wild-type cells (CAF2), as well as strains with
CHK1
and
CSSK1
reconstituted (strains CHK23 and CSSK23, respectively). Adherence and colonization of RHE were evaluated in periodic acid-Schiff-stained sections, as well as by SEM. We observed that both deletion-containing strains colonized the RHE to a lesser extent than did CAF2 and that the percent germination by both strains was reduced in comparison to that of control strains at 1 h postinfection. Expression of
CHK1
or
CSSK1
was quantitated by reverse transcription (RT)-PCR from RHE tissues infected with wild-type
C. albicans
yeast cells. Expression of both
CHK1
and
CSSK1
increased over the 48-h period following infection of the tissue, although expression of
CHK1
was greater than that of
CSSK1
. By RT-PCR, we have also shown that expression of
CHK1
and
CSSK1
in the strains with
cssk1
and
chk1
deleted, respectively, was similar to that of CAF2, indicating that
CHK1
and
CSSK1
do not regulate each other but probably encode signal proteins of different pathways. Our observations indicate that
CHK1
and
CSSK1
are each partially required for colonization and conversion to filamentous growth on RHE tissue.
Entamoeba histolytica
-Induced Dephosphorylation in Host Cells
Authors: Teixeira José E. , Mann Barbara J. 
Published: July 2002

ABSTRACT

Activation of host cell protein tyrosine phosphatases (PTPases) and protein dephosphorylation is an important mechanism used by various microorganisms to deactivate or kill host defense cells. To determine whether protein tyrosine dephosphorylation played a role in signaling pathways affecting
Entamoeba histolytica
-mediated host cell killing, we investigated the involvement of PTPases during the attachment of
E. histolytica
to target cells. We observed a rapid decrease in cellular protein tyrosine levels in Jurkat cells, as measured with an antiphosphotyrosine monoclonal antibody, following adherence to
E. histolytica
. Ameba-induced protein dephosphorylation was contact dependent and required intact parasite, since blocking amebic adherence with galactose inhibited tyrosine dephosphorylation and amebic lysates had no effect on phosphotyrosine levels. Moreover, disruption of amebic adherence with galactose promoted recovery of phosphorylation in Jurkat cells, indicating that dephosphorylation precedes target cell death. The evidence suggests that ameba-induced dephosphorylation is mediated by host cell phosphatases. Prior treatment of Jurkat cells with phenylarsine oxide, a PTPase inhibitor, inhibited ameba-induced dephosphorylation. We also found proteolytic cleavage of the PTPase 1B (PTP1B) in Jurkat cells after contact with amebae. The calcium-dependent protease calpain is responsible for PTP1B cleavage and enzymatic activation. Pretreatment of Jurkat cells with calpeptin, a calpain inhibitor, blocked PTP1B cleavage and inhibited ameba-induced dephosphorylation. In addition, inhibition of Jurkat cell PTPases with phenylarsine oxide blocked Jurkat cell apoptosis induced by
E. histolytica
. These results suggest that
E. histolytica
-mediated host cell death occurs by a mechanism that involves PTPase activation.
Clonal Polymorphism of
Borrelia burgdorferi
Strain B31 MI: Implications for Mutagenesis in an Infectious Strain Background
Authors: Elias Abdallah F. , Stewart Philip E. , Grimm Dorothee , Caimano Melissa J. , Eggers Christian H. , Tilly Kit , Bono James L. , Akins Darrin R. , Radolf Justin D. , Schwan Tom G. , Rosa Patricia 
Published: July 2002

ABSTRACT

A major obstacle to studying the functions of particular gene products in the mouse-tick infectious cycle of
Borrelia burgdorferi
has been an inability to knock out genes in pathogenic strains. Here, we investigated conditions for site-directed mutagenesis in B31 MI, the low-passage-number, infectious
B. burgdorferi
strain whose genome was sequenced. We inactivated several plasmid and chromosomal genes in B31 MI and determined that clones carrying these mutations were not infectious for mice. However, we found extensive heterogeneity among clones and mutants derived from B31 MI based on colony phenotype, growth rate, plasmid content, protein profile, and transformability. Significantly, several B31 MI clones that were not subjected to mutagenesis but that lacked particular plasmids also exhibited defects at various stages in the infectious cycle. Therefore, the high degree of clonal polymorphism within B31 MI complicates the assessment of the contributions of individual genes to the observed phenotypes of the mutants. Our results indicate that B31 MI is not an appropriate strain background for genetic studies in infectious
B. burgdorferi
, and a well-defined isogenic clone is a prerequisite for targeted mutagenesis. To this end, we derived several wild-type clones from B31 MI that were infectious for mice, and gene inactivation was successful in one of these clones. Due to the instability of the genome with in vitro propagation, careful monitoring of plasmid content of derived mutants and complementation of inactivated genes will be crucial components of genetic studies with this pathogen.
Pseudomonas aeruginosa
ExoT Acts In Vivo as a GTPase-Activating Protein for RhoA, Rac1, and Cdc42
Authors: Kazmierczak B. I. , Engel J. N. 
Published: July 2002

ABSTRACT

The
Pseudomonas aeruginosa
protein ExoT is a bacterial GTPase-activating protein (GAP) that has in vitro activity toward Rho, Rac, and Cdc42 GTPases. Expression of ExoT both inhibits the internalization of strain PA103 by macrophages and epithelial cells and is associated with morphological changes (cell rounding and detachment) of infected cells. We find that expression of ExoT leads to the loss of GTP-bound RhoA, Rac1, and Cdc42 in transfected HeLa cells, demonstrating that ExoT has GAP activity in vivo toward all three GTPases. GAP activity is absolutely dependent on the presence of arginine at position 149 but is not affected by whether ExoT is expressed in the absence or presence of other
P. aeruginosa
type III secreted proteins. We also demonstrate that expression of ExoT in epithelial cells is sufficient to cause stress fiber disassembly by means of ExoT's GAP activity toward RhoA.
Membrane Localization Contributes to the In Vivo ADP-Ribosylation of Ras by
Pseudomonas aeruginosa
ExoS
Authors: Riese Matthew J. , Barbieri Joseph T. 
Published: July 2002

ABSTRACT

Type III-delivered exoenzyme S (ExoS) preferentially ADP-ribosylated membrane-associated His
6
HRas, relative to its cytosolic derivative His
6
HRasΔCAAX. This indicates that the subcellular protein distribution contributes to in vivo ADP-ribosylation by ExoS.