bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of Internalization and Viability of
Porphyromonas gingivalis
in KB Epithelial Cells by Confocal Microscopy
Authors: Houalet-Jeanne S. , Pellen-Mussi P. , Tricot-Doleux S. , Apiou J. , Bonnaure-Mallet M. 
Published: July 2002

ABSTRACT

Porphyromonas gingivalis (P. gingivalis)
is considered to be one of the main periodontal pathogens. The goal of this work was to confirm the ability of
P. gingivalis
to invade host cells. We detected
P. gingivalis
inside KB cells by confocal microscopy and analyzed the various aspects of the adherence and internalization process. Lysates of
P. gingivalis
-infected KB cells were also examined using anaerobic growth techniques. The results showed the viability and ability to replicate, inside the host cells, of the internalized pathogen. The production of vesicles was also tracked for the first time. Confocal microscopy revealed
P. gingivalis
in a perinuclear position.
Staphylococcus caprae
Strains Carry Determinants Known To Be Involved in Pathogenicity: a Gene Encoding an Autolysin-Binding Fibronectin and the
ica
Operon Involved in Biofilm Formation
Authors: Allignet Jeanine , Aubert Sylvie , Dyke Keith G. H. , El Solh Nevine 
Published: July 2002

ABSTRACT

The
atlC
gene (1,485 bp), encoding an autolysin which binds fibronectin, and the
ica
operon, involved in biofilm formation, were isolated from the chromosome of an infectious isolate of
Staphylococcus caprae
and sequenced. AtlC (155 kDa) is similar to the staphylococcal autolysins Atl, AtlE, Aas (48 to 72% amino acid identity) and contains a putative signal peptide of 29 amino acids and two enzymatic centers (
N
-acetylmuramoyl-
l
-alanine amidase and endo-β-
N
-acetylglucosaminidase) interconnected by three imperfect fibronectin-binding repeats. The glycine-tryptophan (GW) motif found in the central and end part of each repeat may serve for cell surface anchoring of AtlC as they do in
Listeria monocytogenes
. The
S. caprae ica
operon contains four genes closely related to
S. epidermidis
and
S. aureus icaA
,
icaB
,
icaC
, and
icaD
genes (≥ 68% similarity) and is preceded by a gene similar to
icaR
(≥70% similarity). The polypeptides deduced from the
S. caprae ica
genes exhibit 67 to 88% amino acid identity to those of
S. epidermidis
and
S. aureus ica
genes. The
ica
operon and
icaR
gene were analyzed in 14
S. caprae
strains from human specimens or goats' milk. Some of the strains produced biofilm, and others did not. All strains carry the
ica
operon and
icaR
of the same sizes and in the same relative positions, suggesting that the absence of biofilm formation is not related to the insertion of a mobile element such as an insertion sequence or a transposon.
Immunochemical and Biological Characterization of Three Capsular Polysaccharides from a Single
Bacteroides fragilis
Strain
Authors: Kalka-Moll Wiltrud M. , Wang Ying , Comstock L. E. , Gonzalez Sylvia E. , Tzianabos Arthur O. , Kasper Dennis L. 
Published: July 2002

ABSTRACT

Although
Bacteroides fragilis
accounts for only 0.5% of the normal human colonic flora, it is the anaerobic species most frequently isolated from intra-abdominal and other infections with an intestinal source. The capsular polysaccharides of
B. fragilis
are part of a complex of surface polysaccharides and are the organism's most important virulence factors in the formation of intra-abdominal abscesses. Two capsular polysaccharides from strain NCTC 9343, PS A1 and PS B1, have been characterized structurally. Their most striking feature is a zwitterionic charge motif consisting of both positively and negatively charged substituent groups on each repeating unit. This zwitterionic motif is essential for abscess formation. In this study, we sought to elucidate structural features of the capsular polysaccharide complex of a commonly studied
B. fragilis
strain, 638R, that is distinct from strain 9343. We sought a more general picture of the species to establish basic structure-activity and structure-biosynthesis relationships among abscess-inducing polysaccharides. Strain 638R was found to have a capsular polysaccharide complex from which three distinct carbohydrates could be isolated by a complex purification procedure. Compositional and immunochemical studies demonstrated a zwitterionic charge motif common to all of the capsular polysaccharides that correlated with their ability to induce experimental intra-abdominal abscesses. Of interest is the range of net charges of the isolated polysaccharides—from positive (PS C2) to balanced (PS A2) to negative (PS 3). Relationships among structural components of the zwitterionic polysaccharides and their molecular biosynthesis loci were identified.
In Vivo Dynamics of Type 1 Fimbria Regulation in Uropathogenic
Escherichia coli
during Experimental Urinary Tract Infection
Authors: Gunther Nereus W. , Lockatell Virginia , Johnson David E. , Mobley Harry L. T. 
Published: July 2002

ABSTRACT

Escherichia coli
is the primary cause of uncomplicated infections of the urinary tract including cystitis. More serious infections, characterized as acute pyelonephritis, can also develop. Type 1 fimbriae of
E. coli
contribute to virulence in the urinary tract; however, only recently has the expression of the type 1 fimbriae been investigated in vivo using molecular techniques. Transcription of type 1 fimbrial genes is controlled by a promoter that resides on a 314-bp invertible element capable of two orientations. One places the promoter in the ON orientation, allowing for transcription; the other places the promoter in the OFF orientation, preventing transcription. A PCR-based assay was developed to measure the orientation of the invertible element during an experimental urinary tract infection in mice. Using this assay, it was found that the percentage of the population ON in urine samples correlated with the respective CFU per gram of bladder (
P
= 0.0006) but not with CFU per gram of kidney (
P
> 0.069). Cystitis isolates present in the urine of mice during the course of infection had a higher percentage of their invertible elements in the ON orientation than did pyelonephritis isolates (85 and 34%, respectively, at 24 h;
P
< 0.0001). In general, cystitis isolates, unlike pyelonephritis isolates, were more likely to maintain their invertible elements in the ON orientation for the entire period of infection.
E. coli
cells expressing type 1 fimbriae, expelled in urine, were shown by scanning electron microscopy to be densely packed on the surface of uroepithelial cells. These results suggest that expression of type 1 fimbriae is more critical for cystitis strains than for pyelonephritis strains in the early stages of an infection during bladder colonization.
Gamma Interferon Is Not Required for Arthritis Resistance in the Murine Lyme Disease Model
Authors: Glickstein Lisa , Edelstein Meg , Dong Jay Zengjun 
Published: July 2002

ABSTRACTLyme arthritis is the most common complication following infection of human individuals withBorrelia burgdorferisensu stricto. In mice,B. burgdorferiinfection leads to arthritis of the tibiotarsal joints. Arthritis severity in mice is under host genetic control, as BALB/c mice developed mild arthritis but C3H/He mice developed severe disease followingB. burgdorferiinfection. To study the role of gamma interferon (IFN-γ) in arthritogenesis, targeted mutant mice lacking the IFN-γ receptor (IFN-γR) were infected by inoculation withB. burgdorferi. IFN-γR−/−and parental 129/SvEv mice developed mild arthritis of similar severity, as determined both by weekly tibiotarsal joint measurements and histopathology at 2 and 5 weeks postinfection. Both strains of mice had the same spirochetal burden in the joints, suggesting that the IFN-γR−/−mice were not impaired in controlling spirochetal expansion in vivo. The wild-type mice mounted a Th1 response, with a predominance of CD4+IFN-γ+T cells observed by flow cytometry. In contrast, the IFN-γR−/−mice mounted a Th2 response, with a predominance of CD4+IL-4+T cells. As expected given their cytokine profile, the IFN-γR−/−mice produced fewer CD8+IFN-γ+and MAC-1+IL-12+cells and less immunoglobulin G2a (IgG2a) than their wild-type counterparts. These results strongly suggest that IFN-γ is not required for arthritis resistance or as part of an effective immune response againstB. burgdorferi.
Mapping the Ligand-Binding Region of
Borrelia burgdorferi
Fibronectin-Binding Protein BBK32
Authors: Probert William S. , Kim Jung Hwa , Höök Magnus , Johnson Barbara J. B. 
Published: July 2002

ABSTRACT

The cellular attachment and entry of pathogenic microorganisms can be facilitated by the expression of microbial adhesins that bind fibronectin. We have previously described a
Borrelia burgdorferi
gene,
bbk32
, that encodes a 47-kDa fibronectin-binding protein. In this study, the ligand-binding region of BBK32 from
B. burgdorferi
isolate B31 was localized to 32 amino acids. The
bbk32
gene was cloned and sequenced from three additional
B. burgdorferi
isolates representing different genospecies of
B. burgdorferi
sensu lato. All four
bbk32
genes encoded proteins having fibronectin-binding activity when expressed in
Escherichia coli
, and the deduced proteins shared 81 to 91% amino acid sequence identity within the ligand-binding domain. In addition, the ligand-binding region of BBK32 was found to share sequence homology with a fibronectin-binding peptide defined for protein F1 of
Streptococcus pyogenes
. The structural and functional similarity between the ligand-binding region of BBK32 and the UR region of protein F1 suggests a common mechanism of cellular adhesion and entry for
B. burgdorferi
and
S. pyogenes
.
Establishing a Direct Role for the
Bartonella bacilliformis
Invasion-Associated Locus B (IalB) Protein in Human Erythrocyte Parasitism
Authors: Coleman Sherry A. , Minnick Michael F. 
Published: July 2002

ABSTRACT

The invasion-associated locus A and B genes (
ialAB
) of
Bartonella bacilliformis
were previously shown to confer an erythrocyte-invasive phenotype upon
Escherichia coli
, indirectly implicating their role in virulence. We report the first direct demonstration of a role for
ialB
as a virulence factor in
B. bacilliformis
. The presence of a secretory signal sequence and amino acid sequence similarity to two known outer membrane proteins involved in virulence suggested that IalB was an outer membrane protein. To develop an antiserum for protein localization, the
ialB
gene was cloned in frame into an expression vector with a six-histidine tag and under control of the
lacZ
promoter. The IalB fusion protein was purified by nickel affinity chromatography and used to raise polyclonal antibodies. IalB was initially localized to the bacterial membrane fraction. To further localize IalB,
B. bacilliformis
inner and outer membranes were fractionated by sucrose density gradient centrifugation and identified by appearance, buoyant density (ρ), and cytochrome
b
content. Inner and outer membrane proteins were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and IalB was positively identified by Western blot. Contrary to expectations, IalB was localized to the inner membrane of the pathogen. To directly demonstrate a role for IalB in erythrocyte parasitism, the
B. bacilliformis ialB
gene was disrupted by insertional mutagenesis. The resulting
ialB
mutant strain was complemented in
trans
with a replicative plasmid encoding the full-length
ialB
gene. PCR and high-stringency DNA hybridization confirmed mutagenesis and transcomplementation events. Abrogation and restoration of
ialB
expression was verified by SDS-PAGE and immunoblotting. In vitro virulence assays showed that mutagenesis of
ialB
decreased bacterial association and invasion of human erythrocytes by 47 to 53% relative to controls. Transcomplementation of
ialB
restored erythrocyte association and invasion rates to levels observed in the parental strain. These data provide direct evidence for IalB's role in erythrocyte parasitism and represent the first demonstration of molecular Koch's postulates for a
Bartonella
species.
Effect of Low-Dose Antigen Exposure on Development of Immunity to
Helicobacter pylori
Infection in Mice
Authors: Radcliff Fiona J. , Ferrero Richard L. 
Published: July 2002

ABSTRACT

The effect of low-dose antigen exposure on the development of immunity to
Helicobacter pylori
infection was studied in outbred mice. Animals that were primed with a subinfectious number of
H. pylori
bacteria exhibited significantly lower bacterial loads after challenge with an infectious dose of pathogen (versus controls,
P
< 0.05).
Toxin Levels in Serum Correlate with the Development of Staphylococcal Scalded Skin Syndrome in a Murine Model
Authors: Plano Lisa R. W. , Adkins Becky , Woischnik Markus , Ewing Ruth , Collins Carleen M. 
Published: July 2002

ABSTRACTStaphylococcal scalded skin syndrome (SSSS) is an exfoliative dermatitis that results from infection with exfoliative toxin-producingStaphylococcus aureus. SSSS is seen primarily in infants and children. Here we ask if there is a specific maturation process that protects healthy adults from this syndrome. For these studies, an active recombinant exfoliative toxin A (rETA) was used in a neonatal mouse model. A time course generated on the susceptibility to the toxin as a function of mouse age indicated that BALB/c mice developed the characteristic symptoms of SSSS until day 7 of life. Between day 7 and day 8 of life there was a dramatic decrease in susceptibility, such that mice at day 9 of life were resistant to the effects of the toxin. This time course corresponds approximately to the time needed for maturation of the adaptive immune response, and SSSS in adults is often identified with immunocompromised states. Therefore, mice deficient in this response were examined. Adult mice thymectomized at birth and adult SCID mice did not develop the symptoms of SSSS after injection with the toxin, indicating that the adaptive immune response is not responsible for the lack of susceptibility observed in the older mice. SSSS in adults is also associated with renal disorders, suggesting that levels of toxin in serum are important in the development of the disease. rETA was not cleared as efficiently from the serum of 1-day-old mice compared to clearance from 10-day-old mice. Ten-day-old mice were given repeated injections of toxin so that the maximal level of toxin was maintained for a sustained period of time, and exfoliation occurred in these mice. Thus, whereas the adaptive immune response is not needed for protection of adult mice from SSSS, efficient clearance of the toxin from the bloodstream is a critical factor.
Characterization of the Secreted MPT53 Antigen of
Mycobacterium tuberculosis
Authors: Johnson Sadie , Brusasca PierNatale , Lyashchenko Konstantin , Spencer John S. , Wiker Harald G. , Bifani Pablo , Shashkina Elena , Kreiswirth Barry , Harboe Morten , Schluger Neil , Gomez Manuel , Gennaro Maria Laura 
Published: July 2002

ABSTRACT

MPT53 is a secreted protein of
Mycobacterium tuberculosis
. Southern transfer and hybridization showed
mpt53
to be conserved in the
M. tuberculosis
complex and to have homology with DNA from
Mycobacterium avium
and other nontuberculous mycobacteria. However, anti-MPT53 polyclonal antibodies detected no antigen in the culture filtrates of
M. avium
and other nontuberculous mycobacteria. MPT53 of
M. tuberculosis
induced strong, tuberculosis-specific antibody responses in guinea pigs but induced no delayed-type hypersensitivity. Involvement in immune responses during human tuberculosis was very modest.
Primary Role for CD4+T Lymphocytes in Recovery from Oropharyngeal Candidiasis
Authors: Farah C. S. , Elahi S. , Drysdale K. , Pang G. , Gotjamanos T. , Seymour G. J. , Clancy R. L. , Ashman R. B. 
Published: July 2002

ABSTRACTOropharyngeal candidiasis is associated with defects in cell-mediated immunity and is commonly seen in human immunodeficiency virus positive individuals and AIDS patients. A model for oral candidiasis in T-cell-deficient BALB/c and CBA/CaHnu/numice was established. After inoculation with 108Candida albicansyeasts, these mice displayed increased levels of oral colonization compared to euthymic control mice and developed a chronic oropharyngeal infection. Histopathological examination ofnu/nuoral tissues revealed extensive hyphae penetrating the epithelium, with polymorphonuclear leukocyte microabscess formation. Adoptive transfer of either naive or immune lymphocytes into immunodeficient mice resulted in the recovery of these animals from the oral infection. Reconstitution of immunodeficient mice with naive CD4+but not CD8+T cells significantly decreased oral colonization compared to controls. Interleukin-12 and gamma interferon were detected in the draining lymph nodes of immunodeficient mice following reconstitution with naive lymphocytes. This study demonstrates the direct requirement for T lymphocytes in recovery from oral candidiasis and suggests that this is associated with the production of cytokines by CD4+T helper cells.
Immunogenicity of a 26-Valent Group A Streptococcal Vaccine
Authors: Hu Mary C. , Walls Michael A. , Stroop Steven D. , Reddish Mark A. , Beall Bernard , Dale James B. 
Published: July 2002

ABSTRACTA multivalent vaccine containing amino-terminal M protein fragments from 26 different serotypes of group A streptococci was constructed by recombinant techniques. The vaccine consisted of four different recombinant proteins that were formulated with alum to contain 400 μg of protein per dose. Rabbits were immunized via the intramuscular route at 0, 4, and 16 weeks. Immune sera were assayed for the presence of type-specific antibodies against the individual recombinant M peptides by enzyme-linked immunosorbent assay and for opsonic antibodies by in vitro opsonization tests and indirect bactericidal tests. The 26-valent vaccine was highly immunogenic and elicited fourfold or greater increases in antibody levels against 25 of the 26 serotypes represented in the vaccine. The immune sera were broadly opsonic and were bactericidal against the majority of the 26 different serotypes. Importantly, none of the immune sera cross-reacted with human tissues. Our results indicate that type-specific, protective M protein epitopes can be incorporated into complex, multivalent vaccines designed to elicit broadly protective opsonic antibodies in the absence of tissue-cross-reactive antibodies.
Alpha/Beta Interferon Impairs the Ability of Human Macrophages To Control Growth ofMycobacterium bovisBCG
Authors: Bouchonnet Francine , Boechat Neio , Bonay Marcel , Hance Allan J. 
Published: July 2002

ABSTRACTAdministration of alpha/beta interferon (IFN-α/β) to mice infected withMycobacterium tuberculosishas been shown to increase mycobacterial growth. Because IFN-α/β has direct pleiotropic effects on the differentiation and functional activities of macrophages, we evaluated the effect of IFN-α/β on mycobacterial growth in human monocytes/macrophages in vitro. Monocytes cultured at optimal cell density could control the growth ofM. bovisBCG, as assessed both by measurement of luciferase activity expressed by a mycobacterial reporter strain and by counting of CFU. In contrast, unrestrained mycobacterial growth was observed when monocytes were treated with alpha interferon (IFN-α) 3 days prior to or concomitant with infection. This striking loss of mycobacteriostatic activity was observed with IFN-α and IFN-β and was induced in both freshly isolated monocytes and culture-derived macrophages. Pretreatment of monocytes with IFN-α modified cellular morphology and reduced viability following culture, but neither was observed for culture-derived macrophages, indicating that the effects of IFN-α on mycobacteriostatic activity and cell differentiation and death could be dissociated. These results are compatible with the possibility that the secretion of IFN-α/β could directly promote mycobacterial growth in patients harboring these organisms.
Plasmodium vivaxPromiscuous T-Helper Epitopes Defined and Evaluated as Linear Peptide Chimera Immunogens
Authors: Caro-Aguilar Ivette , Rodríguez Alexandra , Calvo-Calle J. Mauricio , Guzmán Fanny , De la Vega Patricia , Elkin Patarroyo Manuel , Galinski Mary R. , Moreno Alberto 
Published: July 2002

ABSTRACTClinical trials of malaria vaccines have confirmed that parasite-derived T-cell epitopes are required to elicit consistent and long-lasting immune responses. We report here the identification and functional characterization of six T-cell epitopes that are present in the merozoite surface protein-1 ofPlasmodium vivax(PvMSP-1) and bind promiscuously to four different HLA-DRB1∗ alleles. Each of these peptides induced lymphoproliferative responses in cells from individuals with previousP. vivaxinfections. Furthermore, linear-peptide chimeras containing the promiscuous PvMSP-1 T-cell epitopes, synthesized in tandem with thePlasmodium falciparumimmunodominant circumsporozoite protein (CSP) B-cell epitope, induced high specific antibody titers, cytokine production, long-lasting immune responses, and immunoglobulin G isotype class switching in BALB/c mice. A linear-peptide chimera containing an allele-restrictedP. falciparumT-cell epitope with the CSP B-cell epitope was not effective. Two out of the six promiscuous T-cell epitopes exhibiting the highest anti-peptide response also contain B-cell epitopes. Antisera generated against these B-cell epitopes recognizeP. vivaxmerozoites in immunofluorescence assays. Importantly, the anti-peptide antibodies generated to the CSP B-cell epitope inhibited the invasion ofP. falciparumsporozoites into human hepatocytes. These data and the simplicity of design of the chimeric constructs highlight the potential of multimeric, multistage, and multispecies linear-peptide chimeras containing parasite promiscuous T-cell epitopes for malaria vaccine development.
Purified Malaria Pigment (Hemozoin) Enhances Dendritic Cell Maturation and Modulates the Isotype of Antibodies Induced by a DNA Vaccine
Authors: Coban Cevayir , Ishii Ken J. , Sullivan David J. , Kumar Nirbhay 
Published: July 2002

ABSTRACTHemozoin (malaria pigment) has been implicated in the modulation of immune responses during malaria infection. This study was designed to evaluate the effect of purified hemozoin on the in vitro activation of myeloid dendritic cells. Our study also revealed that in addition to enhancing the maturation of dendritic cells, hemozoin also greatly promotes immunoglobulin G2a antibody responses when coadministered with a DNA vaccine plasmid encoding Pfs25, aPlasmodium falciparumtransmission-blocking antigen.
In
Saccharomyces cerevisiae
, Expression of Arginine Catabolic Genes
CAR1
and
CAR2
in Response to Exogenous Nitrogen Availability Is Mediated by the Ume6 (CargRI)-Sin3 (CargRII)-Rpd3 (CargRIII) Complex
Authors: Messenguy Francine , Vierendeels Fabienne , Scherens Bart , Dubois Evelyne 
Published: July 2002

ABSTRACT

The products of three genes named
CARGRI
,
CARGRII
, and
CARGRIII
were shown to repress the expression of
CAR1
and
CAR2
genes, involved in arginine catabolism.
CARGRI
is identical to
UME6
and encodes a regulator of early meiotic genes. In this work we identify
CARGRII
as
SIN3
and
CARGRIII
as
RPD3
. The associated gene products are components of a high-molecular-weight complex with histone deacetylase activity and are recruited by Ume6 to promoters containing a URS1 sequence. Sap30, another component of this complex, is also required to repress
CAR1
expression. This histone deacetylase complex prevents the synthesis of the two arginine catabolic enzymes, arginase (
CAR1
) and ornithine transaminase (
CAR2
), as long as exogenous nitrogen is available. Upon nitrogen depletion, repression at URS1 is released and Ume6 interacts with ArgRI and ArgRII, two proteins involved in arginine-dependent activation of
CAR1
and
CAR2
, leading to high levels of the two catabolic enzymes despite a low cytosolic arginine pool. Our data also show that the deletion of the
UME6
gene impairs cell growth more strongly than the deletion of the
SIN3
or
RPD3
gene, especially in the Σ1278b background.