bluuebunny/crossref_metadata_2025_split huggingface dataset:
p47 GTPases RegulateToxoplasma gondiiSurvival in Activated Macrophages
Authors: Butcher Barbara A. , Greene Robert I. , Henry Stanley C. , Annecharico Kimberly L. , Weinberg J. Brice , Denkers Eric Y. , Sher Alan , Taylor Gregory A. 
Published: May 2005

ABSTRACTThe cytokine gamma interferon (IFN-γ) is critical for resistance toToxoplasma gondii. IFN-γ strongly activates macrophages and nonphagocytic host cells to limit intracellular growth ofT. gondii; however, the cellular factors that are required for this effect are largely unknown. We have shown previously that IGTP and LRG-47, members of the IFN-γ-regulated family of p47 GTPases, are required for resistance to acuteT. gondiiinfections in vivo. In contrast, IRG-47, another member of this family, is not required. In the present work, we addressed whether these GTPases are required for IFN-γ-induced suppression ofT. gondiigrowth in macrophages in vitro. Bone marrow macrophages that lacked IGTP or LRG-47 displayed greatly attenuated IFN-γ-induced inhibition ofT. gondiigrowth, while macrophages that lacked IRG-47 displayed normal inhibition. Thus, the ability of the p47 GTPases to limit acute infection in vivo correlated with their ability to suppress intracellular growth in macrophages in vitro. Using confocal microscopy and sucrose density fractionation, we demonstrated that IGTP largely colocalizes with endoplasmic reticulum markers, while LRG-47 was mainly restricted to the Golgi. Although both IGTP and LRG-47 localized to vacuoles containing latex beads, neither protein localized to vacuoles containing liveT. gondii. These results suggest that IGTP and LRG-47 are able to regulate host resistance to acuteT. gondiiinfections through their ability to inhibit parasite growth within the macrophage.
Immunohistological Characterization of Macrophage Migration Inhibitory Factor Expression inPlasmodium falciparum-Infected Placentas
Authors: Chaisavaneeyakorn Sujittra , Lucchi Naomi , Abramowsky Carlos , Othoro Caroline , Chaiyaroj Sansanee C. , Shi Ya Ping , Nahlen Bernard L. , Peterson David S. , Moore Julie M. , Udhayakumar Venkatachalam 
Published: May 2005

ABSTRACTPreviously, we have shown that macrophage migration inhibitory factor (MIF) was highly elevated in the placental intervillous blood (IVB) ofPlasmodium falciparum-infected women. Here, we compared the expression of MIF in placental tissues obtained fromP. falciparum-infected and -uninfected women. Immunoperoxidase staining showed a consistent pattern of MIF expression in syncytiotrophoblasts, extravillous trophoblasts, IVB mononuclear cells, and amniotic epithelial cells, irrespective of their malaria infection status. Cytotrophoblast, villous stroma, and Hofbauer cells showed focal staining. Only amniotic epithelial and IVB mononuclear cells fromP. falciparum-infected placentas exhibited significantly higher level of MIF expression than uninfected placentas. Stimulation of syncytilized human trophoblast BeWo cells withP. falciparum-infected erythrocytes that were selected to bind these cells resulted in significant increases in MIF secretion, whereas control erythrocytes, lipopolysaccharides, and synthetic β-hematin had minimal effect. These findings suggest that placental malaria modulates MIF expression in different placental compartments.
An RNA Vaccine Based on Recombinant Semliki Forest Virus Particles Expressing the Cu,Zn Superoxide Dismutase Protein of
Brucella abortus
Induces Protective Immunity in BALB/c Mice
Authors: Oñate Angel A. , Donoso Gabriel , Moraga-Cid Gustavo , Folch Hugo , Céspedes Sandra , Andrews Edilia 
Published: May 2005

ABSTRACT

We constructed infectious but replication-deficient Semliki Forest virus (SFV) particles carrying recombinant RNA encoding
Brucella abortus
Cu,Zn superoxide dismutase (SOD). The recombinant SFV particles (SFV-SOD particles) were then evaluated for their ability to induce a T-cell immune response and to protect BALB/c mice against a challenge with
B. abortus
2308. Intraperitoneal injection of mice with recombinant SFV-SOD particles did not lead to the induction of SOD-specific antibodies, at least until week 6 after immunization (the end of the experiment). In vitro stimulation of splenocytes from the vaccinated mice with either recombinant Cu,Zn SOD (rSOD) or crude
Brucella
protein resulted in a T-cell proliferative response and the induction of gamma interferon secretion but not interleukin-4. In addition, the splenocytes exhibited significant levels of cytotoxic T-lymphocyte activity against
Brucella
-infected cells. The SFV-SOD particles, but not the control virus particles, induced a significant level of protection in BALB/c mice against challenge with
B. abortus
virulent strain 2308. These findings indicated that an SFV-based vector carrying the SOD gene has potential for use as a vaccine to induce resistance against
B. abortus
infections.
Skin Test Performed with Highly PurifiedMycobacterium tuberculosisRecombinant Protein Triggers Tuberculin Shock in Infected Guinea Pigs
Authors: Reece Stephen T. , Stride Nicole , Ovendale Pamela , Reed Steven G. , Campos-Neto Antonio 
Published: May 2005

ABSTRACTTuberculin shock due to inoculation ofMycobacterium tuberculosisantigens in patients with tuberculosis is a serious syndrome originally described over 100 years ago by Robert Koch. Here, we present experimental evidence that a singleM. tuberculosisrecombinant protein, CFP-10, triggers this syndrome. Intradermal inoculation of CFP-10 elicits inM. tuberculosis-infected mice high levels of serum tumor necrosis factor alpha and causes tuberculin shock in infected guinea pigs characterized by hypothermia and death within 6 to 48 h after the antigen inoculation. Autopsies of these animals revealed intense polycythemia and hemorrhagic patches in the lung parenchyma, a pathological observation consistent with tuberculin shock. These results point to the possible occurrence of tuberculin shock in sensitive individuals inoculated with highly purifiedM. tuberculosisrecombinant proteins as vaccine candidates or skin test reagents.
A Newly Discovered Mycobacterial Pathogen Isolated from Laboratory Colonies of
Xenopus
Species with Lethal Infections Produces a Novel Form of Mycolactone, the
Mycobacterium ulcerans
Macrolide Toxin
Authors: Mve-Obiang Armand , Lee Richard E. , Umstot Edward S. , Trott Kristin A. , Grammer Timothy C. , Parker John M. , Ranger Brian S. , Grainger Robert , Mahrous Engu A. , Small P. L. C. 
Published: May 2005

ABSTRACT

Mycobacterium ulcerans
, the causative agent of Buruli ulcer, produces a macrolide toxin, mycolactone A/B, which is thought to play a major role in virulence. A disease similar to Buruli ulcer recently appeared in United States frog colonies following importation of the West African frog,
Xenopus tropicalis
. The taxonomic position of the frog pathogen has not been fully elucidated, but this organism, tentatively designated
Mycobacterium liflandii
, is closely related to
M. ulcerans
and
Mycobacterium marinum
, and as further evidence is gathered, it will most likely be considered a subspecies of one of these species. In this paper we show that
M. liflandii
produces a novel plasmid-encoded mycolactone, mycolactone E.
M. liflandii
contains all of the genes in the mycolactone cluster with the exception of that encoding CYP140A2, a putative p450 monooxygenase. Although the core lactone structure is conserved in mycolactone E, the fatty acid side chain differs from that of mycolactone A/B in the number of hydroxyl groups and double bonds. The cytopathic phenotype of mycolactone E is identical to that of mycolactone A/B, although it is less potent. To further characterize the relationship between
M. liflandii
and
M. ulcerans
, strains were analyzed for the presence of the RD1 region genes,
esxA
(ESAT-6) and
esxB
(CFP-10). The
M. ulcerans
genome strain has a deletion in RD1 and lacks these genes. The results of these studies show that
M. liflandii
contains both
esxA
and
esxB
.
Immunoglobulin-Regulated Expression ofBorrelia burgdorferiOuter Surface Protein A In Vivo
Authors: Hodzic Emir , Tunev Stefan , Feng Sunlian , Freet Kim J. , Barthold Stephen W. 
Published: May 2005

ABSTRACTBorrelia burgdorferi, the agent of Lyme disease, down-regulates outer surface protein A (OspA), which is abundantly expressed in ticks, during infection of the mammalian host. In this study we examined the signals that may be responsible for maintaining the OspA-negative state of spirochetes during infection. Transcription ofospAmRNA was found in tissues of C3H-severe combined immunodeficient (C3H-scid) mice, but not immunocompetent C3H mice, inoculated with culturedB. burgdorferi, tick-borne spirochetes, and host-adapted spirochetes. Transcription was more frequent at 4 weeks than at 1 week. Transcription was present at the host-tick interface as early as 24 h after tick attachment but declined at 48 and 72 h. Thus,ospAmRNA transcription in distant tissues and at later times in C3H-scidmice is probably due to up-regulation during infection. Adoptive lymphocyte transfer from naïve C3H mice to infected C3H-scidmice resulted in OspA seroconversion, confirming OspA expression in the host. Passive transfer of normal mouse serum, immunoglobulin M (IgM) from normal mouse serum, or IgG from normal mouse serum into infected C3H-scidmice resulted in down-regulation ofospA, but transfer of normal mouse serum depleted of immunoglobulin did not influenceospAmRNA transcription. Collectively, our results indicate thatospAmRNA transcription in the host is regulated by nonspecific immunoglobulin, which may be a natural antibody.
Nitric Oxide Detoxification Systems Enhance Survival of
Neisseria meningitidis
in Human Macrophages and in Nasopharyngeal Mucosa
Authors: Stevanin TÂnia M. , Moir James W. B. , Read Robert C. 
Published: May 2005

ABSTRACT

Nitric oxide (NO) contributes to mammalian host defense by direct microbicidal activity and as a signaling molecule of innate immune responses. Macrophages produce NO via the inducible NO synthase (iNOS). The genome of
Neisseria meningitidis
includes two genes,
norB
(encoding nitric oxide reductase) and
cycP
(encoding cytochrome
c′
), both of which detoxify NO in pure cultures of
N. meningitidis
. We show here that
norB
, and to a lesser extent
cycP
, enhance survival of
N. meningitidis
within primary human macrophages. Furthermore, accumulation of lysosome-associated membrane protein 1 (LAMP-1) is modified in phagosomes containing an isogenic
norB
mutant of
N. meningitidis
compared to the wild type. The survival enhancement conferred by
norB
and
cycP
is ablated by pretreatment of macrophages with the nitric oxide synthase inhibitor
N
(G)-monomethyl-
l
-arginine (L-NMMA). Despite this evidence that NO detoxification confers advantage, we find, using a highly sensitive chemiluminescence technique, that human macrophage-associated [NO] is low even after activation by lipopolysaccharide and interferon alpha. Furthermore, wild-type
N. meningitidis
further depletes cell-associated NO during phagocytosis by an active mechanism and survives relatively poorly in the presence of L-NMMA, suggesting that the wild-type organism may utilize NO for optimal survival during intracellular life. The natural habitat of
N. meningitidis
is the human nasopharynx. Using a nasopharyngeal mucosa organ culture system, we show that mutants lacking
norB
and
cycP
also survive poorly in nasopharyngeal tissue compared to wild-type
N. meningitidis
. These findings indicate that the meningococcus requires active NO detoxification systems for optimal survival during experimental nasopharyngeal colonization and processing by human phagocytic cells.
Common and Unique Gene Expression Signatures of Human Macrophages in Response to Four Strains ofMycobacterium aviumThat Differ in Their Growth and Persistence Characteristics
Authors: Blumenthal Antje , Lauber Jörg , Hoffmann Reinhard , Ernst Martin , Keller Christine , Buer Jan , Ehlers Stefan , Reiling Norbert 
Published: May 2005

ABSTRACTClassification of pathogenic species according to the distinct host transcriptional responses that they elicit may become a relevant tool for microarray-based diagnosis of infection. Individual strains ofMycobacterium avium, an opportunistic pathogen in humans, have previously been shown to differ in terms of growth and persistence. In order to cover a wide spectrum of virulence, we selected fourM. aviumisolates (2151SmO, 2151SmT, SE01, TMC724) that have distinct intramacrophage replication characteristics and cause differential activation in human macrophages. Following infection with each of these strains, the expression of 12,558 genes in human macrophages was systematically analyzed by microarray technology. Fifty genes (including genes encoding proinflammatory cytokines, chemokines, signaling, and adhesion molecules) were differentially expressed more than twofold in response to all of theM. aviumisolates investigated and therefore constitute a common macrophage signature in response toM. avium. The magnitude of regulation of most of these genes was directly correlated with the host cell-activating capacity of the particularM. aviumstrain. The regulation of a number of genes not previously associated with mycobacterial infections was apparent; these genes included genes encoding lymphocyte antigen 64 and myosin X. In addition, individual response patterns typical for someM. aviumisolates could be defined by the pronounced upregulation of interleukin-12p40 (IL-12p40) (in the case of 2151SmO) or the specific upregulation of SOCS-1 and IL-10 (in the case of SE01) in macrophages. TMC724, a strain of avian origin, could not be classified by any one of these schemes, possibly indicating the limits of pathogen categorization solely by immune response signatures.
The SrtA Sortase of
Streptococcus agalactiae
Is Required for Cell Wall Anchoring of Proteins Containing the LPXTG Motif, for Adhesion to Epithelial Cells, and for Colonization of the Mouse Intestine
Authors: Lalioui Lila , Pellegrini Elisabeth , Dramsi Shaynoor , Baptista Marina , Bourgeois Nadege , Doucet-Populaire Florence , Rusniok Christophe , Zouine Mohamed , Glaser Philippe , Kunst Frank , Poyart Claire , Trieu-Cuot Patrick 
Published: May 2005

ABSTRACT

Streptococcus agalactiae
(group B streptococcus [GBS]) is the leading cause of neonatal pneumonia, sepsis, and meningitis. An in silico genome analysis indicated that GBS strain NEM316 encodes 35 proteins containing an LPXTG motif which are thought to be covalently linked to the peptidoglycan by an enzyme called sortase. The role of these cell wall-anchored proteins in GBS pathogenesis was evaluated on a global level by inactivating the
srtA
gene. This gene encodes the major sortase SrtA that anchors most of the LPXTG-containing proteins. We chose the C5a peptidase (ScpB) and Alp2, an abundant immunogenic protein, as prototypical LPXTG-containing proteins. As expected, the SrtA knockout mutant was unable to anchor the C5a peptidase (ScpB) and Alp2 to the cell wall. Complementation with plasmid-borne
srtA
inserted into the chromosome restored the correct surface localization of both ScpB and Alp2. Interestingly, the SrtA mutant was impaired for binding to the major extracellular matrix components fibronectin and fibrinogen and displayed a significant reduction in adherence to human (A549, HeLa, and Caco-2) and murine (L2) epithelial cells compared to the parental wild-type strain. Surprisingly, the inactivation of
srtA
had no effect on the virulence of the type III strain of GBS in a neonatal rat model (measured by the 50% lethal dose and lung colonization) but strongly impaired the capacity of the strain to colonize the intestines of gnotobiotic mice in a competition assay. These results demonstrate that LPXTG-containing proteins are involved in cell adhesion and GBS persistence in vivo.
Inactivation of
Streptococcus
gordonii
SspAB Alters Expression of Multiple Adhesin Genes
Authors: Zhang Yongshu , Lei Yu , Nobbs Angela , Khammanivong Ali , Herzberg Mark C. 
Published: May 2005

ABSTRACT

SspA and SspB (antigen I/II family proteins) can bind
Streptococcus
gordonii
to other oral bacteria and also to salivary agglutinin glycoprotein, a constituent of the salivary film or pellicle that coats the tooth. To learn if SspA and SspB are essential for adhesion and initial biofilm formation on teeth,
S. gordonii
DL1 was incubated with saliva-coated hydroxyapatite (sHA) for 2 h in Todd-Hewitt broth with 20% saliva to develop initial biofilms. Sessile cells attached to sHA, surrounding planktonic cells, and free-growing cells were recovered separately. Free-growing cells expressed more
sspA
-specific mRNA and
sspB
-specific mRNA than sessile cells. Free-growing cells expressed the same levels of
sspA
and
sspB
as planktonic cells. Surprisingly, an SspA
−
SspB
−
mutant strain showed 2.2-fold greater biofilm formation on sHA than wild-type
S. gordonii
DL1. To explain this observation, we tested the hypothesis that inactivation of
sspA
and
sspB
genes altered the expression of other adhesin genes during initial biofilm formation in vitro. When compared to wild-type cells, expression of
scaA
and
abpB
was significantly up-regulated in the SspA
−
SspB
−
strain in sessile, planktonic, and free-growing cells. Consistent with this finding, ScaA antigen was also overexpressed in planktonic and free-growing SspA
−
SspB
−
cells compared to the wild type. SspA/B adhesins, therefore, were strongly suggested to be involved in the regulation of multiple adhesin genes.
The
Salmonella enterica
Serotype Typhimurium
lpf
,
bcf
,
stb
,
stc
,
std
, and
sth
Fimbrial Operons Are Required for Intestinal Persistence in Mice
Authors: Weening Eric H. , Barker Jared D. , Laarakker Marijke C. , Humphries Andrea D. , Tsolis Renée M. , Bäumler Andreas J. 
Published: May 2005

ABSTRACT

Salmonella enterica
serotype Typhimurium causes human infections that can frequently be traced back through the food chain to healthy livestock whose intestine is colonized by the pathogen. Little is known about the genes important for intestinal carriage of
S. enterica
serotype Typhimurium in vertebrate animals. Here we characterized the role of 10 fimbrial operons,
agf
,
fim
,
lpf
,
pef
,
bcf
,
stb
,
stc
,
std
,
stf
, and
sth
, using competitive infection experiments performed in genetically susceptible (BALB/c) and resistant (CBA) mice. Deletion of
agfAB
,
fimAICDHF
,
lpfABCDE
,
pefABCDI
,
bcfABCDEFG
,
stbABCD
,
stcABCD
,
stdAB
,
stfACDEFG
, or
sthABCDE
did not reduce the ability of
S. enterica
serotype Typhimurium to colonize the spleen and cecum of BALB/c mice 5 days after infection. Similarly, deletion of
agfAB
,
fimAICDHF
,
pefABCDI
, and
stfACDEFG
did not result in reduced recovery of
S. enterica
serotype Typhimurium from fecal samples collected from infected CBA mice over a 30-day time period. However,
S. enterica
serotype Typhimurium strains carrying deletions in
lpfABCDE
,
bcfABCDEFG
,
stbABCD
,
stcABCD
,
stdAB
, or
sthABCDE
were recovered at significantly reduced numbers from the feces of CBA mice. There was a good correlation (
R
2
= 0.9626) between competitive indices in the cecum and fecal samples of CBA mice at 30 days after infection, suggesting that the recovery of
S. enterica
serotype Typhimurium from fecal samples closely reflected its ability to colonize the cecum. Collectively, these data show that six fimbrial operons (
lpf
,
bcf
,
stb
,
stc
,
std
, and
sth
) contribute to long-term intestinal carriage of
S. enterica
serotype Typhimurium in genetically resistant mice.
The Vi Capsular Antigen ofSalmonella entericaSerotype Typhi Reduces Toll-Like Receptor-Dependent Interleukin-8 Expression in the Intestinal Mucosa
Authors: Raffatellu Manuela , Chessa Daniela , Wilson R. Paul , Dusold Richard , Rubino Salvatore , Bäumler Andreas J. 
Published: May 2005

ABSTRACTHuman infections with nontyphoidalSalmonellaserotypes, such asS. entericaserotype Typhimurium, are characterized by a massive neutrophil influx in the colon and terminal ileum. In contrast, neutrophils are scarce in intestinal infiltrates of typhoid fever patients. Here, we show that inS. entericaserotype Typhi, the causative agent of typhoid fever, expression of the Vi capsular antigen reduced expression of the neutrophil chemoattractant interleukin-8 (IL-8) in host cells. Capsulated bacteria elicited IL-8 expression in polarized human epithelial cells (T84) and human macrophage-like cells (THP-1) in vitro at significantly reduced levels compared to noncapsulated bacteria. Experiments with a human cell line (HEK293) transfected with human Toll-like receptors (TLRs) demonstrated that in the presence of TLR5 or TLR4/MD2/CD14, a noncapsulated serotype Typhi mutant was able to induce the expression of IL-8, while this host response was significantly reduced when cells were infected with the capsulated serotype Typhi wild type. The relevance of these in vitro observations for the interaction of serotype Typhi with its human host was further studied ex vivo using human colonic tissue explants. Expression of IL-8 was detected in human colonic tissue explants infected with serotype Typhimurium or a noncapsulated serotype Typhi mutant. In contrast, infection with the serotype Typhi wild type did not elicit IL-8 expression in colonic tissue explants. Collectively, these data suggest that the scarcity of neutrophils in intestinal infiltrates of typhoid fever patients is due to a capsule-mediated reduction of TLR-dependent IL-8 production in the intestinal mucosa.
Increased Sensitivity to Staphylococcal Enterotoxin B following Adenoviral Infection
Authors: Yarovinsky Timur O. , Mohning Michael P. , Bradford Mary A. , Monick Martha M. , Hunninghake Gary W. 
Published: May 2005

ABSTRACTStaphylococcal enterotoxin B induces toxic shock and is a major virulence factor of staphylococcal diseases. We examined the effects of systemic adenoviral infection on responses to staphylococcal enterotoxin B in a murine model. We found that adenoviral infection markedly increases the severity of liver injury following exposure to staphylococcal enterotoxin B withoutd-galactosamine sensitization. In adenovirus-infected mice, staphylococcal enterotoxin B triggered a more profound hypothermia and increased apoptosis in the liver. Consistent with these observations, we also found that adenoviral infection primed for an increased production of gamma interferon in vivo and in vitro following stimulation with staphylococcal enterotoxin B. Gamma-interferon-knockout mice did not show increased sensitivity to staphylococcal enterotoxin B following adenoviral infection. These data suggest that a preexisting viral infection primes mice for subsequent staphylococcal enterotoxin B exposure, possibly via a gamma-interferon-mediated mechanism.