bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role for Interleukin-1β inTrypanosoma cruzi-Induced Cardiomyocyte Hypertrophy
Authors: Petersen Christine A. , Burleigh Barbara A. 
Published: July 2003

ABSTRACTChagas' disease, the leading cause of heart failure in Latin America, results from infection with the intracellular protozoan parasiteTrypanosoma cruzi. Host cell responses elicited in the myocardium early in the infective process are thought to be critical for establishment of infection by this pathogen; however, these changes have not been well characterized. We report here that primary cardiomyocytes undergo hypertrophy as an early response toT. cruziinfection. TheT. cruzi-elicited hypertrophic response is characterized by increased expression of genes encoding the contractile proteins MyHCβ and MyHCα, followed by an approximately twofold increase in cell size. Hypertrophy was observed in both parasite-containing and noninfected cell populations represented inT. cruzi-infected cultures, indicating the involvement of a soluble mediator in this process. Conditioned medium harvested fromT. cruzi-infected cultures, which contained significant levels of interleukin-1β (IL-1β) but not endothelin-1 or tumor necrosis factor alpha, was sufficient to induce hypertrophy in isolated cardiomyocytes. Addition of a high-affinity receptor chimera, IL-1 trap, to cardiomyocyte cultures blocked the overall increase in cell size elicited byT. cruzi. These novel findings indicate that IL-1β, which is rapidly induced in response toT. cruzi, promotes cardiomyocyte hypertrophy early in the infective process and may contribute to maintenance of cardiomyocyte function during establishment ofT. cruziinfection in the heart.
Caspase 1 Involvement in Human Monocyte Lysis Induced by
Actinobacillus actinomycetemcomitans
Leukotoxin
Authors: Kelk P. , Johansson A. , Claesson R. , Hänström L. , Kalfas S. 
Published: July 2003

ABSTRACT

Actinobacillus actinomycetemcomitans
, an oral bacterium implicated in the etiology of periodontal diseases, produces a leukotoxin that selectively lyses primate neutrophils and monocytes, the major populations of defense cells in the periodontium. Though lysis requires expression of the receptor lymphocyte function-associated molecule 1 (LFA-1) on the cell surface, not all LFA-1-expressing leukocyte populations are equally susceptible to the toxin. In this study, the susceptibility of human leukocytes to leukotoxin-induced lysis is compared to their expression of LFA-1 and the activity of caspase 1. Cytolysis was determined by the activity of lactate dehydrogenase released from peripheral human leukocytes after 1-h exposure to leukotoxin. Monocytes were lysed at leukotoxin concentrations of ≥5 ng/ml, while the corresponding values for neutrophils and lymphocytes were approximately 10 times greater. Similar LFA-1 expression was found in all susceptible cell populations irrespective of their degree of sensitivity to the toxin. Exposure of monocytes to leukotoxin increased their caspase 1 activity about fivefold within 10 to 20 min. Presence of the caspase 1 inhibitor Ac-YVAD-CMK significantly blocked the leukotoxin-induced lysis of monocytes only. At sublytic concentrations, leukotoxin induced no apoptotic activity in monocytes, as revealed by the lack of caspase 3 activation and DNA fragmentation. Monocytes are the most lysis-sensitive leukocytes for
A. actinomycetemcomitans
leukotoxin. Their lysis by this toxin depends on caspase 1 activation and proceeds through a process that differs from classical apoptosis.
Toll-Like Receptor 2- and 6-Mediated Stimulation by Macrophage-Activating Lipopeptide 2 Induces Lipopolysaccharide (LPS) Cross Tolerance in Mice, Which Results in Protection from Tumor Necrosis Factor Alpha but in Only Partial Protection from Lethal LPS Doses
Authors: Deiters Ursula , Gumenscheimer Marina , Galanos Chris , Mühlradt Peter F. 
Published: July 2003

ABSTRACTPatients or experimental animals previously exposed to lipopolysaccharide (LPS) become tolerant to further LPS challenge. We investigated the potential of the macrophage-activating lipopeptide 2 (MALP-2) to induce in vivo cross tolerance to tumor necrosis factor alpha (TNF-α) and LPS. MALP-2-induced tolerance could be of practical interest, as MALP-2 proved much less pyrogenic in rabbits than LPS. Whereas LPS signals via Toll-like receptor 4 (TLR4), MALP-2 uses TLR2 and TLR6. LPS-mediated cytokine release was studied in mice pretreated with intraperitoneal injections of MALP-2. No biologically active TNF-α could be detected in the serum of MALP-2-treated animals when challenged with LPS 24 or 72 h later, whereas suppression of LPS-dependent interleukin (IL)-6 lasted for only 24 h. Protection from lethal TNF-α shock was studied in galactosamine-treated mice. Dose dependently, MALP-2 prevented death from lethal TNF-α doses in TLR4−/−but not in TLR2−/−mice, with protection lasting from 5 to 24 h. To assay protection from LPS, mice were pretreated with MALP-2 doses of up to 10 μg. Five and 24 h later, the animals were simultaneously sensitized and challenged by intravenous coinjection of galactosamine and a lethal dose of 50 ng of LPS. There was only limited protection (four of seven mice survived) when mice were challenged 5 h after MALP-2 pretreatment, and no protection when mice were challenged at later times. The high effectiveness of MALP-2 in suppressing TNF-α, the known ways of biological inactivation, and low pyrogenicity make MALP-2 a potential candidate for clinical use.
Identification of the
agr
Locus of
Listeria monocytogenes
: Role in Bacterial Virulence
Authors: Autret Nicolas , Raynaud Catherine , Dubail Iharilalao , Berche Patrick , Charbit Alain 
Published: July 2003

ABSTRACT

Listeria monocytogenes
is a gram-positive facultative intracellular food-borne pathogen that can cause severe infections in humans and animals. We have recently adapted signature-tagged transposon mutagenesis (STM) to identify genes involved in the virulence of
L. monocytogenes
. A new round of STM allowed us to identify a new locus encoding a protein homologous to AgrA, the well-studied response regulator of
Staphylococcus aureus
and part of a two-component system involved in bacterial virulence. The production of several secreted proteins was modified in the
agrA
mutant of
L. monocytogenes
grown in broth, indicating that the
agr
locus influenced protein secretion. Inactivation of
agrA
did not affect the ability of the pathogen to invade and multiply in cells in vitro. However, the virulence of the
agrA
mutant was attenuated in the mouse (a 10-fold increase in the 50% lethal dose by the intravenous route), demonstrating for the first time a role for the
agr
locus in the virulence of
L. monocytogenes
.
Stress-Dependent Expression of a Polymorphic, Charged Antigen in the Protozoan Parasite
Entamoeba histolytica
Authors: Satish S. , Bakre Abhijeet A. , Bhattacharya Sudha , Bhattacharya Alok 
Published: July 2003

ABSTRACT

We have identified a novel stress inducible gene, Ehssp1 in
Entamoeba histolytica
, the causative agent of amebiasis. Ehssp1 belongs to a polymorphic, multigene family and is present on multiple chromosomes. No homologue of this gene was found in the NCBI database. Sequence alignment of the multiple copies, and genomic PCR data restricted the polymorphism to the central region of the gene. This region contains a polypurine stretch that encodes a domain rich in acidic and basic amino acids. Under normal culture conditions only one copy of this multigene family is expressed, as observed by Northern blot and RT-PCR analysis. The size of this copy of the gene is 1,077 nucleotides, encoding a protein of 359 amino acids. The polymorphic domain in this copy is 64 nucleotides long. However, on exposure of cells to stress conditions such as heat shock or oxidative stress, multiple polymorphic copies of the gene are expressed, suggesting a possible role of this gene in adaptation of cells to stress conditions. The gene copy expressed under normal conditions, and the expression profile of cells under heat stress was identical in two different strains of
E. histolytica
tested. Interestingly, the extent of polymorphism in this gene was very less in
E. dispar
, a nonpathogenic sibling species of
E. histolytica
. Ehssp1 was found to be antigenic in invasive amebiasis patients.
TheMycobacterium tuberculosis19-Kilodalton Lipoprotein Inhibits Gamma Interferon-Regulated HLA-DR and FcγR1 on Human Macrophages through Toll-Like Receptor 2
Authors: Gehring Adam J. , Rojas Roxana E. , Canaday David H. , Lakey David L. , Harding Clifford V. , Boom W. Henry 
Published: July 2003

ABSTRACTMycobacterium tuberculosissurvives in macrophages in the face of acquired CD4+T-cell immunity, which controls but does not eliminate the organism. Gamma interferon (IFN-γ) has a central role in host defenses againstM. tuberculosisby activating macrophages and regulating major histocompatibility complex class II (MHC-II) antigen (Ag) processing.M. tuberculosisinterferes with IFN-γ receptor (IFN-γR) signaling in macrophages, but the molecules responsible for this inhibition are poorly defined. This study determined that the 19-kDa lipoprotein fromM. tuberculosisinhibits IFN-γ-regulated HLA-DR protein and mRNA expression in human macrophages. Inhibition of HLA-DR expression was associated with decreased processing and presentation of soluble protein Ags andM. tuberculosisbacilli to MHC-II-restricted T cells. Inhibition of HLA-DR required prolonged exposure to 19-kDa lipoprotein and was blocked with a monoclonal antibody specific for Toll-like receptor 2 (TLR-2). The 19-kDa lipoprotein also inhibited IFN-γ-induced expression of FcγRI. Thus,M. tuberculosis, through 19-kDa lipoprotein activation of TLR-2, inhibits IFN-γR signaling in human macrophages, resulting in decreased MHC-II Ag processing and recognition by MHC-II-restricted CD4 T cells. These findings provide a mechanism forM. tuberculosispersistence in macrophages.
Relative Roles of Genetic Background and Variation in PspA in the Ability of Antibodies to PspA To Protect against Capsular Type 3 and 4 Strains of
Streptococcus pneumoniae
Authors: Roche Hazeline , Ren Bing , McDaniel Larry S. , Håkansson Anders , Briles David E. 
Published: July 2003

ABSTRACT

Pneumococcal surface protein A (PspA) is able to elicit antibodies in mice and humans that can protect mice against fatal infection with
Streptococcus pneumoniae
. It has been observed that immunization with a single family 1 PspA can protect mice against infections with capsular type 3 or 6B strains expressing PspA family 1 or 2. However, several studies have shown that immunity to PspA is less efficacious against several capsular type 4 strains than against strains of capsular types 3, 6A, and 6B. To determine whether the greater difficulty in protecting against capsular type 4 strains resulted from differences in their PspAs or from differences in their genetic backgrounds, we performed protection experiments using four different challenge strains: a capsular type 3 strain expressing a family 1 PspA (WU2), a capsular type 4 strain expressing a family 2 PspA (TIGR4), and genetically engineered variants of WU2 and TIGR4 expressing each other's PspAs. Prior to infection, the mice were immunized with recombinant family 1 or family 2 PspA. The results revealed that much of the difficulty in protecting against capsular type 4 strains was eliminated when mice were immunized with a homologous PspA of the same PspA family. However, regardless of which PspA the strains expressed, those on the TIGR4 background were about twice as hard to protect against as WU2 strains expressing the same PspA based on the efficacy rates seen in our experiments. These results point out the importance of including more than one PspA in any PspA vaccines developed for human use.
Induction of Specific T-Cell Responses, Opsonizing Antibodies, and Protection againstPlasmodium chabaudi adamiInfection in Mice Vaccinated with Genomic Expression Libraries Expressed in Targeted and Secretory DNA Vectors
Authors: Rainczuk A. , Scorza T. , Smooker P. M. , Spithill T. W. 
Published: July 2003

ABSTRACTIt has been proposed that a multivalent malaria vaccine is necessary to mimic the naturally acquired resistance to this disease observed in humans. A major experimental challenge is to identify the optimal components to be used in such a multivalent vaccine. Expression library immunization (ELI) is a method for screening genomes of a pathogen to identify novel combinations of vaccine sequences. Here we describe immune responses associated with, and the protective efficacy of, genomicPlasmodium chabaudi adamiDS expression libraries constructed in VR1020 (secretory), monocyte chemotactic protein-3 (chemoattractant), and cytotoxic T lymphocyte antigen 4 (lymph node-targeting) DNA vaccine vectors. With splenocytes from vaccinated mice, specific T-cell responses, as well as gamma interferon and interleukin-4 production, were observed after stimulation withP. chabaudi adami-infected erythrocytes, demonstrating the specificity of genomic library vaccination for two of the three libraries constructed. Sera obtained from mice vaccinated with genomic libraries promoted the opsonization ofP. chabaudi adami-infected erythrocytes by murine macrophages in vitro, further demonstrating the induction of malaria-specific immune responses following ELI. Over three vaccine trials using biolistic delivery of the three libraries, protection after lethal challenge withP. chabaudi adamiDS ranged from 33 to 50%. These results show that protective epitopes or antigens are expressed within the libraries and that ELI induces responses specific toP. chabaudi adamimalaria. This study further demonstrates that ELI is a suitable approach for screening the malaria genome to identify the components of multivalent vaccines.
Characterization of the Novel Factor Paa Involved in the Early Steps of the Adhesion Mechanism of Attaching and Effacing
Escherichia coli
Authors: Batisson Isabelle , Guimond Marie-Pierre , Girard Francis , An Hongyan , Zhu Chengru , Oswald Eric , Fairbrother John M. , Jacques Mario , Harel Josée 
Published: July 2003

ABSTRACT

Nonenterotoxigenic porcine
Escherichia coli
strains belonging to the serogroup O45 have been associated with postweaning diarrhea in swine and adhere to intestinal epithelial cells in a characteristic attaching and effacing (A/E) pattern. O45 porcine enteropathogenic
E. coli
(PEPEC) strain 86-1390 induces typical A/E lesions in a pig ileal explant model. Using Tn
phoA
transposon insertion mutagenesis on strain 86-1390, we found a mutant that did not induce A/E lesions. The insertion was identified in a gene designated
paa
(porcine A/E-associated gene). Sequence analysis of
paa
revealed an open reading frame of 753 bp encoding a 27.6-kDa protein which displayed 100, 51.8, and 49% homology with Paa of enterohemorrhagic
E. coli
O157:H7 strains (EDL933 and Sakai), PEB3 of
Campylobacter jejuni
, and AcfC of
Vibrio cholerae
, respectively. Chromosomal localization studies indicated that the region containing
paa
was inserted between the
yciD
and
yciE
genes at about 28.3 min of the
E. coli
K-12 chromosome. The presence of
paa
and
eae
sequences in the porcine O45 strains is highly correlated with the A/E phenotype. However, the observation that three
eae
-positive but
paa
-negative PEPEC O45 strains were A/E negative provides further evidence for the importance of the
paa
gene in the A/E activity of O45 strains. As well, the complementation of the
paa
mutant restored the A/E activity of the 86-1390 strain, showing the involvement of Paa in PEPEC pathogenicity. These observations suggest that Paa contributes to the early stages of A/E
E. coli
virulence.
Legionella pneumophila
Catalase-Peroxidases Are Required for Proper Trafficking and Growth in Primary Macrophages
Authors: Bandyopadhyay Purnima , Byrne Brenda , Chan Yolande , Swanson Michele S. , Steinman Howard M. 
Published: July 2003

ABSTRACT

Legionella pneumophila
, a parasite of aquatic amoebae and pathogen of pulmonary macrophages, replicates intracellularly, utilizing a type IV secretion system to subvert the trafficking of
Legionella
-containing phagosomes. Defense against host-derived reactive oxygen species has been proposed as critical for intracellular replication. Virulence traits of null mutants in
katA
and
katB
, encoding the two
Legionella
catalase-peroxidases, were analyzed to evaluate the hypothesis that
L. pneumophila
must decompose hydrogen peroxide to establish a replication niche in macrophages. Phagosomes containing
katA
or
katB
mutant
Legionella
colocalize with LAMP-1, a late endosomal-lysosomal marker, at twice the frequency of those of wild-type strain JR32 and show a decreased frequency of bacterial replication, in similarity to phenotypes of mutants with mutations in
dotA
and
dotB
, encoding components of the Type IV secretion system. Quantitative similarity of the
katA
/
B
phenotypes indicates that each contributes to virulence traits largely independently of intracellular compartmentalization (KatA in the periplasm and KatB in the cytosol). These data support a model in which KatA and KatB maintain a critically low level of H
2
O
2
compatible with proper phagosome trafficking mediated by the type IV secretion apparatus. During these studies, we observed that
dotA
and
dotB
mutations in wild-type strain Lp02 had no effect on intracellular multiplication in the amoeba
Acanthamoeba castellanii
, indicating that certain
dotA
/
B
functions in Lp02 are dispensable in that experimental model. We also observed that wild-type JR32, unlike Lp02, shows minimal contact-dependent cytotoxicity, suggesting that cytotoxicity of JR32 is not a prerequisite for formation of replication-competent
Legionella
phagosomes in macrophages.
DNA Immunization with the Cysteine-Rich Interdomain Region 1 of the
Plasmodium falciparum
Variant Antigen Elicits Limited Cross-Reactive Antibody Responses
Authors: Baruch Dror I. , Gamain Benoit , Miller Louis H. 
Published: July 2003

ABSTRACT

The variant surface antigens of
Plasmodium falciparum
are an important component of naturally acquired immunity and an important vaccine target. However, these proteins appear to elicit primarily variant-specific antibodies. We tested if naked DNA immunization can elicit more cross-reactive antibody responses and allow simultaneous immunization with several variant constructs. Mice immunized with plasmid DNA expressing variant cysteine-rich interdomain region 1 (CIDR1) domains of the
P. falciparum
erythrocyte membrane protein 1 (PfEMP1) developed antibodies that were reactive to the corresponding PfEMP1s as measured by an enzyme-linked immunosorbent assay, flow cytometry, and agglutination of parasitized erythrocytes (PEs). We observed some cross-reactive immune responses; for example, sera from mice immunized with one domain agglutinated PEs of various lines and recognized heterologous domains expressed on the surface of Chinese hamster ovary (CHO) cells. We found no significant antigenic competition when animals were immunized with a mixture of plasmids or immunized sequentially with individual constructs. Moreover, mixed or sequential immunizations resulted in greater cross-reactive agglutination responses than immunization with a single domain. Recombinant protein (Sc y179) immunization after priming with DNA (prime-boost regimen) increased antibody titers to the homologous domain substantially but seemed to diminish the cross-reactive responses somewhat. The titer of agglutinating antibodies was previously shown to correlate with protection. Surprisingly, the agglutination titers of sera from DNA immunization were high, similar to those of pooled human hyperimmune sera. These sera also appeared to give limited low-titer variant transcending agglutination. Thus, DNA immunization appears to be a very useful tool for developing variant antigen vaccines.
Mycobacterium bovisBCG Scar Status and HLA Class II Alleles Influence Purified Protein Derivative-Specific T-Cell Receptor Vβ Expression in Pulmonary Tuberculosis Patients from Southern India
Authors: Shanmugalakshmi S. , Dheenadhayalan V. , Muthuveeralakshmi P. , Arivarignan G. , Pitchappan R.M. 
Published: July 2003

ABSTRACTPurified protein derivative (PPD) RT23-recalled T-cell receptor (TCR) Vβ expression was studied in the peripheral blood of 42 pulmonary tuberculosis patients and 44 healthy controls from southern India, a region where tuberculosis is endemic. Forty-eight-hour whole-blood cultures in the presence or absence of PPD-RT23 were set up, and at the end of the culture period total RNA was extracted and cDNA was synthesized. Expression of various TCR Vβ families was assessed by using family-specific primers. PPD-specific expression (usage) of TCR Vβ families 4, 6, 8 to 12, and 14 was found in more controls than patients. Among the responders (individuals who showed PPD-specific expression), endemic controls had significantly higher responses than the patients had for TCR Vβ families 2, 3, 7, 13, and 17. The majority of the patients did not show usage of most of the TCR Vβ families, and this was attributed to T-cell downregulation. A four-way nested classification analysis revealed that TCR Vβ family 1, 5, 9, 12, and 13 usage in the context of HLA class II high-risk alleles (DRB1*1501, DRB1*08, and DQB1*0601) andMycobacterium bovisBCG scar status were the determining factors in susceptibility and resistance to tuberculosis. The healthier status of controls was attributed to the wider usage of many TCR Vβ families readily recalled by PPD, while the disease status of the patients was attributed to TCR Vβ downregulation and the resultant T-cell (memory cell?) unresponsiveness. Host genetics (HLA status) and BCG vaccination (scar status) seem to play important roles in skewing the immune response in adult susceptibility to pulmonary tuberculosis through TCR Vβ usage.
Shiga Toxin 2-Converting Bacteriophages Associated with Clonal Variability in
Escherichia coli
O157:H7 Strains of Human Origin Isolated from a Single Outbreak
Authors: Muniesa Maite , de Simon Mercè , Prats Guillem , Ferrer Dolors , Pañella Helena , Jofre Juan 
Published: July 2003

ABSTRACT

Shiga toxin 2 (Stx2)-converting bacteriophages induced from 49 strains of
Escherichia coli
O157:H7 isolated during a recent outbreak of enterocolitis in Spain were examined in an attempt to identify the variability due to the
stx
2
-converting phages. The bacterial isolates were divided into low-, medium-, and high-phage-production groups on the basis of the number of phages released after mitomycin C induction. Low- and medium-phage-production isolates harbored two kinds of phages but released only one of them, whereas high-phage-production isolates harbored only one of the two phages. One of the phages, φSC370, which was detected only in the isolates with two phages, showed similarities with phage 933W. The second phage, φLC159, differed from φSC370 in morphology and DNA structure. When both phages were present in the same bacterial chromosome, as occurred in most of the isolates, only φSC370 was detected in the supernatants of the induced cultures. If φLC159 was released, its presence was masked by φSC370. When φSC370 was absent, large amounts of φLC159 were released, suggesting that there was some regulation of phage expression between the two phages. To our knowledge, this is the first description of clonal variability due to phage loss. The higher level of phage production was reflected in the larger amounts of Stx2 toxin produced by the cultures. Some relationship between phage production and the severity of symptoms was observed, and consequently these observations suggest that the virulence of the isolates studied could be related to the variability of the induced
stx
2
-converting phages.