bluuebunny/crossref_metadata_2025_split huggingface dataset:
Requirement of Non-T Cells That Produce Gamma Interferon for Prevention of Reactivation ofToxoplasma gondiiInfection in the Brain
Authors: Kang Hoil , Suzuki Yasuhiro 
Published: July 2002

ABSTRACTWe examined the mechanism of resistance against reactivation of infection withToxoplasma gondiiin the brain. BALB/c-background gamma interferon (IFN-γ)-knockout (IFN-γ−/−) and control mice were infected and treated with sulfadiazine beginning 4 days after infection for 3 weeks. After discontinuation of treatment, IFN-γ−/−mice succumbed to toxoplasmic encephalitis (TE) and died, whereas control animals did not develop TE and survived. Adoptive transfer of immune spleen cells from infected control mice did not prevent development of TE or mortality in the IFN-γ−/−mice. To examine whether the failure of the cell transfer to protect against TE is unique to IFN-γ−/−mice, athymic nude and SCID mice that lack T cells were infected and injected with the immune spleen or T cells in the same manner as IFN-γ−/−mice. Whereas control nude and SCID mice that had not received the immune cells developed severe TE and died after discontinuation of sulfadiazine, those that had received the cells did not develop TE and survived. Before cell transfer, IFN-γ mRNA was detected in brains of infected nude and SCID but not in brains of IFN-γ−/−mice. IFN-γ mRNA was also detected in brains of infected SCID mice depleted of NK cells by treatment with anti-asialo GM1 antibody, and such animals did not develop TE after receiving immune T cells. Thus, IFN-γ production by non-T cells, in addition to T cells, is required for prevention of reactivation ofT. gondiiinfection in the brain. The IFN-γ-producing non-T cells do not appear to be NK cells.
Pathogenic YeastsCryptococcus neoformansandCandida albicansProduce Immunomodulatory Prostaglandins
Authors: Noverr Mairi C. , Phare Susan M. , Toews Galen B. , Coffey Michael J. , Huffnagle Gary B. 
Published: July 2002

ABSTRACTEnhanced prostaglandin production during fungal infection could be an important factor in promoting fungal colonization and chronic infection. Host cells are one source of prostaglandins; however, another potential source of prostaglandins is the fungal pathogen itself. Our objective was to determine if the pathogenic yeastsCryptococcus neoformansandCandida albicansproduce prostaglandins and, if so, to begin to define the role of these bioactive lipids in yeast biology and disease pathogenesis.C. neoformansandC. albicansboth secreted prostaglandins de novo or via conversion of exogenous arachidonic acid. Treatment with cyclooxygenase inhibitors dramatically reduced the viability of the yeast and the production of prostaglandins, suggesting that an essential cyclooxygenase like enzyme may be responsible for fungal prostaglandin production. A PGE series lipid was purified from bothC. albicansandC. neoformansand was biologically active on both fungal and mammalian cells. Fungal PGExand synthetic PGE2enhanced the yeast-to-hypha transition inC. albicans. Furthermore, in mammalian cells, fungal PGExdown-modulated chemokine production, tumor necrosis factor alpha production, and splenocyte proliferation while up-regulating interleukin 10 production. These are all activities previously documented for mammalian PGE2. Thus, eicosanoids are produced by pathogenic fungi, are critical for growth of the fungi, and can modulate host immune functions. The discovery that pathogenic fungi produce and respond to immunomodulatory eicosanoids reveals a virulence mechanism that has potentially great implications for understanding the mechanisms of chronic fungal infection, immune deviation, and fungi as disease cofactors.
Improved Immunogenicity and Protective Efficacy of a Tuberculosis DNA Vaccine Encoding Ag85 by Protein Boosting
Authors: Tanghe Audrey , D'Souza Sushila , Rosseels Valérie , Denis Olivier , Ottenhoff Thomas H. M. , Dalemans Wilfried , Wheeler Carl , Huygen Kris 
Published: July 2002

ABSTRACTC57BL/6 mice were vaccinated with plasmid DNA encoding Ag85 fromMycobacterium tuberculosis, with Ag85 protein in adjuvant, or with a combined DNA prime-protein boost regimen. While DNA immunization, as previously described, induced robust Th1-type cytokine responses, protein-in-adjuvant vaccination elicited very poor cytokine responses, which were 10-fold lower than those observed with DNA immunization alone. Injection of Ag85 DNA-primed mice with 30 to 100 μg of purified Ag85 protein in adjuvant increased the interleukin-2 and gamma interferon (IFN-γ) response in spleen two- to fourfold. Further, intracellular cytokine analysis by flow cytometry also showed an increase in IFN-γ-producing CD4+T cells in DNA-primed–protein-boosted animals, compared to those that received only the DNA vaccination. Moreover, these responses appeared to be better sustained over time. Antibodies were readily produced by all three methods of immunization but were exclusively of the immunoglobulin G1 (IgG1) isotype following protein immunization in adjuvant and preferentially of the IgG2a isotype following DNA and DNA prime-protein boost vaccination. Finally, protein boosting increased the protective efficacy of the DNA vaccine against an intravenousM. tuberculosisH37Rv challenge infection, as measured by CFU or relative light unit counts in lungs 1 and 2 months after infection. The capacity of exogenously given protein to boost the DNA-primed vaccination effect underlines the dominant role of Th1-type CD4+helper T cells in mediating protection.
ExtensiveMycobacterium bovisBCG Infection of Liver Parenchymal Cells in Immunocompromised Mice
Authors: Mills John W. , Ryan Lynn , LaCourse Ronald , North Robert J. 
Published: July 2002

ABSTRACTA histologic study was performed on the livers of wild-type (WT), severe combined immunodeficient (SCID), hydrocortisone acetate (HC)-treated WT, and HC-treated SCID mice infected intravenously with 105CFU ofMycobacterium bovisBCG. It was found that infection progressed faster in SCID mice than in WT mice and that HC treatment caused exacerbation of infection in both types of mice. In all cases infection in the liver was confined to granulomas that were populated predominantly by macrophages. Higher levels of infection in HC-treated SCID mice, but not HC-treated WT mice, were associated with extensive infection and destruction of parenchymal cells at the margins of granulomas. The results indicate that in the absence of T-cell-mediated immunity and of HC-sensitive T-cell-independent defense mechanisms, macrophages are incapable of restricting BCG growth and of confining infection to their cytoplasm. Consequently, BCG bacilli are released into the extracellular environment, where they are ingested by neighboring parenchymal cells.
Key Role of Teichoic Acid Net Charge in
Staphylococcus aureus
Colonization of Artificial Surfaces
Authors: Gross Matthias , Cramton Sarah E. , Götz Friedrich , Peschel Andreas 
Published: July 2002

ABSTRACT

Staphylococcus aureus
is responsible for a large percentage of infections associated with implanted biomedical devices. The molecular basis of primary adhesion to artificial surfaces is not yet understood. Here, we demonstrate that teichoic acids, highly charged cell wall polymers, play a key role in the first step of biofilm formation. An
S. aureus
mutant bearing a stronger negative surface charge due to the lack of
d
-alanine esters in its teichoic acids can no longer colonize polystyrene or glass. The mutation abrogates primary adhesion to plastic while production of the glucosamine-based polymer involved in later steps of biofilm formation is not affected. Our data suggest that repulsive electrostatic forces can lead to reduced staphylococcal biofilm formation, which could have considerable impact on the design of novel implanted materials.
Immunization with Recombinant Opc Outer Membrane Protein from
Neisseria meningitidis
: Influence of Sequence Variation and Levels of Expression on the Bactericidal Immune Response against Meningococci
Authors: Jolley Keith A. , Appleby Lynn , Wright J. Claire , Christodoulides Myron , Heckels John E. 
Published: July 2002

ABSTRACT

The
opc
gene from
Neisseria meningitidis
was cloned into the pRSETA vector, and recombinant protein was expressed at high levels in
Escherichia coli
. The protein was readily purified by affinity chromatography and used for immunization with conventional Al(OH)
3
adjuvant or after incorporation into liposomes and Zwittergent micelles. The resulting sera were analyzed for their ability to recognize purified recombinant protein and “native” protein in an enzyme immunoassay with outer membranes and by whole-cell immunofluorescence. Immunization with Al(OH)
3
induced high levels of antibodies which reacted with the purified protein but did not recognize whole cells. In contrast, liposomes and micelles induced antibodies which reacted with the native protein in whole cells. The addition of monophosphoryl lipid A (MPLA) to either liposomes or micelle preparations increased the magnitude of the immune response and induced a wider range of immunoglobulin subclasses. This was associated with the ability of the sera to induce complement-mediated killing of the homologous strain. The most effective bactericidal activity was observed with Opc protein incorporated into liposomes containing MPLA. The magnitude of the bactericidal effect was strongly influenced by the level of expression of the Opc protein and was abolished by limited variation in the sequence of the protein expressed by heterologous strains.
Deletion ofwboAEnhances Activation of the Lectin Pathway of Complement inBrucella abortusandBrucella melitensis
Authors: Fernandez-Prada Carmen M. , Nikolich Mikeljon , Vemulapalli Ramesh , Sriranganathan Nammalwar , Boyle Stephen M. , Schurig Gerhardt G. , Hadfield Ted L. , Hoover David L. 
Published: July 2002

ABSTRACTBrucellaspp. are gram-negative intracellular pathogens that survive and multiply within phagocytic cells of their hosts. Smooth organisms present O polysaccharides (OPS) on their surface. These OPS help the bacteria avoid the bactericidal action of serum. ThewboAgene, coding for the enzyme glycosyltransferase, is essential for the synthesis of O chain inBrucella. In this study, the sensitivity to serum of smooth, virulentBrucella melitensis16M andB. abortus2308, roughwboAmutants VTRM1, RA1, and WRR51 derived from these twoBrucellaspecies, and theB. abortusvaccine strain RB51 was assayed using normal nonimmune human serum (NHS). The deposition of complement components and mannose-binding lectin (MBL) on the bacterial surface was detected by flow cytometry. RoughB. abortusmutants were more sensitive to the bactericidal action of NHS than were roughB. melitensismutants. Complement components were deposited on smooth strains at a slower rate compared to rough strains. Deposition of iC3b and C5b-9 and bacterial killing occurred when bacteria were treated with C1q-depleted, but not with C2-depleted serum or NHS in the presence of Mg-EGTA. These results indicate that (i) OPS-deficient strains derived fromB. melitensis16M are more resistant to the bactericidal action of NHS than OPS-deficient strains derived fromB. abortus2308, (ii) both the classical and the MBL-mediated pathways are involved in complement deposition and complement-mediated killing ofBrucella, and (iii) the alternative pathway is not activated by smooth or rough brucellae.
Role of Gingipains in Growth of
Porphyromonas gingivalis
in the Presence of Human Serum Albumin
Authors: Grenier Daniel , Imbeault Sandra , Plamondon Pascale , Grenier Gilbert , Nakayama Koji , Mayrand Denis 
Published: July 2002

ABSTRACT

Porphyromonas gingivalis
, a bacterium associated with active chronic periodontitis lesions, produces several proteolytic enzymes that are thought to be involved in host colonization, perturbation of the immune system, and tissue destruction. The aim of the present study was to investigate the contribution of Arg- and Lys-gingipains produced by
P. gingivalis
to its growth. Although all of the proteins studied were degraded by
P. gingivalis
, only human serum albumin and transferrin supported growth during serial transfers in a chemically defined medium (CDM). Growth studies with site-directed gingipain-deficient mutants of
P. gingivalis
revealed that inactivation of both gingipains prevents growth, whereas inactivation of either Arg- or Lys-gingipain activity extended the doubling times to 33 or 13 h, respectively, compared to 9 h for the parent strain. Growth of the mutants and the parent strain was similar when the CDM was supplemented with a protein hydrolysate instead of human serum albumin. Incubation of resting
P. gingivalis
ATCC 33277 cells with fluorophore-labeled albumin indicated that the proteolytic fragments generated by the gingipains were internalized by the bacterial cells. Internalization of fluorophore-labeled albumin fragments was reduced or completely inhibited in the proteinase-deficient mutants. Interestingly, gingival crevicular fluid samples from diseased periodontal sites contained low-molecular-mass albumin fragments, whereas samples from healthy sites did not. The critical role of proteinases in the growth of
P. gingivalis
was further investigated using specific Arg- and Lys-gingipain inhibitors. Adding the inhibitors to CDM containing albumin revealed that leupeptin (Arg-gingipain A and B inhibitor) was more efficient at inhibiting growth than cathepsin B inhibitor II (Lys-gingipain inhibitor). Our study suggests that Arg-gingipains and, to a lesser extent, Lys-gingipain play an important role in the growth of
P. gingivalis
in a defined medium containing a human protein as the sole carbon and nitrogen source.
Comparative Sequence Analysis of the Plasmid-Encoded Regulator of Enteropathogenic
Escherichia coli
Strains
Authors: Okeke Iruka N. , Borneman Jade A. , Shin Sooan , Mellies Jay L. , Quinn Laura E. , Kaper James B. 
Published: July 2002

ABSTRACT

Enteropathogenic
Escherichia coli
(EPEC) strains that carry the EPEC adherence factor (EAF) plasmid were screened for the presence of different EAF sequences, including those of the plasmid-encoded regulator (
per
). Considerable variation in gene content of EAF plasmids from different strains was seen. However,
bfpA
, the gene encoding the structural subunit for the bundle-forming pilus, bundlin, and
per
genes were found in 96.8% of strains. Sequence analysis of the
per
operon and its promoter region from 15 representative strains revealed that it is highly conserved. Most of the variation occurs in the 5′ two-thirds of the
perA
gene. In contrast, the C-terminal portion of the predicted PerA protein that contains the DNA-binding helix-turn-helix motif is 100% conserved in all strains that possess a full-length gene. In a minority of strains including the O119:H2 and canine isolates and in a subset of O128:H2 and O142:H6 strains, frameshift mutations in
perA
leading to premature truncation and consequent inactivation of the gene were identified. Cloned
perA
, -
B
, and -
C
genes from these strains, unlike those from strains with a functional operon, failed to activate the
LEE1
operon and
bfpA
transcriptional fusions or to complement a
per
mutant in reference strain E2348/69. Furthermore, O119, O128, and canine strains that carry inactive
per
operons were deficient in virulence protein expression. The context in which the
perABC
operon occurs on the EAF plasmid varies. The sequence upstream of the
per
promoter region in EPEC reference strains E2348/69 and B171-8 was present in strains belonging to most serogroups. In a subset of O119:H2, O128:H2, and O142:H6 strains and in the canine isolate, this sequence was replaced by an IS
1294
-homologous sequence.
RS1 Element of
Vibrio cholerae
Can Propagate Horizontally as a Filamentous Phage Exploiting the Morphogenesis Genes of CTXΦ
Authors: Faruque Shah M. , Asadulghani  , Kamruzzaman M. , Nandi Ranjan K. , Ghosh A. N. , Nair G. Balakrish , Mekalanos John J. , Sack David A. 
Published: July 2002

ABSTRACT

In toxigenic
Vibrio cholerae
, cholera toxin is encoded by the CTX prophage, which consists of a core region carrying
ctxAB
genes and genes required for CTXΦ morphogenesis, and an RS2 region encoding regulation, replication, and integration functions. Integrated CTXΦ is often flanked by another genetic element known as RS1 which carries all open reading frames (ORFs) found in RS2 and an additional ORF designated
rstC
. We identified a single-stranded circularized form of the RS1 element, in addition to the CTXΦ genome, in nucleic acids extracted from phage preparations of 32 out of 83 (38.5%) RS1-positive toxigenic
V. cholerae
strains analyzed. Subsequently, the corresponding double-stranded replicative form (RF) of the RS1 element was isolated from a representative strain and marked with a kanamycin resistance (Km
r
) marker in an intergenic site to construct pRS1-Km. Restriction and PCR analysis of pRS1-Km and sequencing of a 300-bp region confirmed that this RF DNA was the excised RS1 element which formed a novel junction between
ig1
and
rstC
. Introduction of pRS1-Km into a
V. cholerae
O1 classical biotype strain, O395, led to the production of extracellular Km
r
transducing particles, which carried a single-stranded form of pRS1-Km, thus resembling the genome of a filamentous phage (RS1-KmΦ). Analysis of
V. cholerae
strains for susceptibility to RS1-KmΦ showed that classical biotype strains were more susceptible to the phage compared to El Tor and O139 strains. Nontoxigenic (CTX
−
) O1 and O139 strains which carried genes encoding the CTXΦ receptor toxin-coregulated pilus (TCP) were also more susceptible (>1,000-fold) to the phage compared to toxigenic El Tor or O139 strains. Like CTXΦ, the RS1Φ genome also integrated into the host chromosomes by using the
att
RS sequence. However, only transductants of RS1-KmΦ which also harbored the CTXΦ genome produced a detectable level of extracellular RS1-KmΦ. This suggested that the core genes of CTXΦ are also required for the morphogenesis of RS1Φ. The results of this study showed for the first time that RS1 element, which encodes a site-specific recombination system in
V. cholerae
, can propagate horizontally as a filamentous phage, exploiting the morphogenesis genes of CTXΦ.
Bacteriophage Therapy Rescues Mice Bacteremic from a Clinical Isolate of Vancomycin-Resistant
Enterococcus faecium
Authors: Biswas Biswajit , Adhya Sankar , Washart Paul , Paul Brian , Trostel Andrei N. , Powell Bradford , Carlton Richard , Merril Carl R. 
Published: July 2002

ABSTRACT

Colonization of the gastrointestinal tract with vancomycin-resistant
Enterococcus faecium
(VRE) has become endemic in many hospitals and nursing homes in the United States. Such colonization predisposes the individual to VRE bacteremia and/or endocarditis, and immunocompromised patients are at particular risk for these conditions. The emergence of antibiotic-resistant bacterial strains requires the exploration of alternative antibacterial therapies, which led our group to study the ability of bacterial viruses (bacteriophages, or phages) to rescue mice with VRE bacteremia. The phage strain used in this study has lytic activity against a wide range of clinical isolates of VRE. One of these VRE strains was used to induce bacteremia in mice by intraperitoneal (i.p.) injection of 10
9
CFU. The resulting bacteremia was fatal within 48 h. A single i.p. injection of 3 × 10
8
PFU of the phage strain, administered 45 min after the bacterial challenge, was sufficient to rescue 100% of the animals. Even when treatment was delayed to the point where all animals were moribund, approximately 50% of them were rescued by a single injection of this phage preparation. The ability of this phage to rescue bacteremic mice was demonstrated to be due to the functional capabilities of the phage and not to a nonspecific immune effect. The rescue of bacteremic mice could be effected only by phage strains able to grow in vitro on the bacterial host used to infect the animals, and when such strains are heat inactivated they lose their ability to rescue the infected mice.
In Vivo Rho GTPase-Activating Protein Activity of
Pseudomonas aeruginosa
Cytotoxin ExoS
Authors: Krall Rebecca , Sun Jianjun , Pederson Kristin J. , Barbieri Joseph T. 
Published: July 2002

ABSTRACT

ExoS is a bifunctional type III cytotoxin secreted by
Pseudomonas aeruginosa,
which comprises a C-terminal ADP ribosyltransferase domain and an N-terminal Rho GTPase-activating protein (GAP) domain. In vitro, ExoS is a Rho GAP for Rho, Rac, and Cdc42; however, the in vivo modulation of Rho GTPases has not been addressed. Using a transient transfection system and delivery by
P. aeruginosa
, interactions were examined between the Rho GAP domain of ExoS and Rho GTPases in CHO cells. Rho GTPases were expressed as green fluorescent protein (GFP) fusion proteins to facilitate quantitation. GFP fusions of wild-type and dominant active Rho, Rac, and Cdc42 localized to discrete regions of CHO cells and appeared functional based upon their modulation of the actin cytoskeleton. Coexpression of the Rho GAP domain of ExoS changed the intracellular distribution of GFP-Rac and GFP-Cdc42 from a predominately membrane location to a cytosolic location. Coexpression of the Rho GAP domain of ExoS did not change the distribution of GFP-Rho, which was primarily in the cytosol. Coexpression of dominant active Rac (DARac) and DACdc42 inhibited actin reorganization by the Rho GAP domain but did not maintain the formation of actin stress fibers, which indicated that Rho had been inactivated. Similar results were observed when ExoS was delivered into CHO cells by
P. aeruginosa
. These data indicate that in vivo the Rho GAP activity of ExoS stimulates the reorganization of the actin cytoskeleton by inhibition of Rac and Cdc42 and stimulates actin stress fiber formation by inhibition of Rho.
Yersinia enterocoliticaas a Vehicle for a Naked DNA Vaccine EncodingBrucella abortusBacterioferritin or P39 Antigen
Authors: Al-Mariri Ayman , Tibor Anne , Lestrate Pascal , Mertens Pascal , De Bolle Xavier , Letesson Jean-Jacques 
Published: July 2002

ABSTRACTBrucellais a facultative intracellular parasite that causes brucellosis in animals and humans. The protective immune response againstBrucellainvolves both humoral and cell-mediated immunity. In previous studies, we demonstrated that the T-dominantBrucellaantigens bacterioferritin (BFR) and P39 administered either as CpG adjuvant recombinant proteins or as naked-DNA plasmids induced a specific Th1-biased immune response in mice. In order to improve the protection conferred by the BFR and P39 vaccines and to evaluate the additive role of antilipopolysaccharide (anti-LPS) antibodies, we used live attenuatedYersinia enterocoliticaserotypes O:3 and O:9 as delivery vectors for naked-DNA plasmids encoding these BFR and P39 antigens. Following two intragastric immunizations in BALB/c mice, theYersiniavectors harboring a DNA vaccine encoding BFR or P39 induced antigen-specific serum immunoglobulin and Th1-type responses (both lymphocyte proliferation and gamma interferon production) among splenocytes. Moreover, as expected, antibodies recognizingBrucella abortus544 lipopolysaccharide were detected in O:9-immunized mice but not in O:3-treated animals. Animals immunized with O:9 organisms carrying pCI or with O:9 organisms alone were found to be significantly resistant to infection byB. abortus544. Our data demonstrated that pCI plasmids encoding BFR or P39 and delivered with live attenuated strains ofYersiniaO:3 or O:9 can trigger Th1-type responses. The fact than only O:9 vectors induced a highly significant protective immunity againstB. abortus544 infection pointed out the crucial role of anti-LPS antibodies in protection. The best protection was conferred by a serotype O:9 strain carrying pCIP39, confirming the importance of the P39 T-cell antigen in this mechanism.