bluuebunny/crossref_metadata_2025_split huggingface dataset:
A New Cruzipain-Mediated Pathway of Human Cell Invasion by
Trypanosoma cruzi
Requires Trypomastigote Membranes
Authors: Aparicio Isabela M. , Scharfstein Julio , Lima Ana Paula C. A. 
Published: September 2004

ABSTRACT

The intracellular protozoan
Trypanosoma cruzi
causes Chagas' disease, a chronic illness associated with cardiomyopathy and digestive disorders. This pathogen invades mammalian cells by signaling them through multiple transduction pathways. We previously showed that cruzipain, the main cysteine protease of
T. cruzi
, promotes host cell invasion by activating kinin receptors. Here, we report a cruzipain-mediated invasion route that is not blocked by kinin receptor antagonists. By testing different strains of
T. cruzi
, we observed a correlation between the level of cruzipain secreted by trypomastigotes and the capacity of the pathogen to invade host cells. Consistent with a role for cruzipain, the cysteine protease inhibitor
N
-methylpiperazine-urea-Phe-homophenylalanine-vinylsulfone-benzene impaired the invasion of human smooth muscle cells by strains Dm28c and X10/6 but not by the G isolate. Cruzipain-rich supernatants of Dm28c trypomastigotes enhanced the infectivity of isolate G parasites twofold, an effect which was abolished by the cysteine protease inhibitor
l
-
trans
-epoxysuccinyl-leucylamido-(4-guanidino)butane and by thapsigargin, a drug that induces depletion of the intracellular Ca
2+
stores. The enhancement due to Dm28 supernatants was abolished upon cruzipain immunodepletion, and the activity was restored by purified cruzipain. In contrast, supernatants from isolate G trypomastigotes (with low levels of cruzipain) or supernatants from Dm28c epimastigotes or purified cruzipain alone did not enhance parasite invasion, indicating that the protease is required but not sufficient to engage this invasion pathway. We provide evidence that activation of this pathway requires cruzipain-mediated processing of a trypomastigote molecule associated with parasite-shed membranes. Our results couple cruzipain to host cell invasion through a kinin-independent route and further suggest that high-level cruzipain expression may contribute to parasite infectivity.
Characterization of the Antigenic Lipopolysaccharide O Chain and the Capsular Polysaccharide Produced by
Actinobacillus pleuropneumoniae
Serotype 13
Authors: MacLean Leann L. , Perry Malcolm B. , Vinogradov Evguenii 
Published: September 2004

ABSTRACT

Serotyping
of
Actinobacillus pleuropneumoniae
, the etiologic agent of
porcine pleuropneumonia, is important for epidemiological studies and
for the development of homologous vaccine cell preparations. The
serology is based on the specific chemical structures of capsular
polysaccharides (CPSs) and lipopolysaccharide (LPS) antigenic
O-polysaccharide moieties (O-PSs), and knowledge of these structures is
required for a molecular-level understanding of their serological
specificities. The structures of
A. pleuropneumoniae
serotype
1 to 12 CPSs and O-PSs have been elucidated; however, the structures
associated with three newly proposed serotypes (serotypes 13, 14, and
15) have not been reported. Herein we described the structures of the
antigenic O-PS and CPS of
A. pleuropneumoniae
serotype 13. The
O-PS of the
A. pleuropneumoniae
serotype 13 LPS is a polymer
of branched tetrasaccharide repeating units composed of
l
-rhamnose, 2-acetamido-2-deoxy-
d
-galactose, and
d
-galactose residues (1:1:2). By use of hydrolysis,
methylation, and periodate oxidation chemical methods together with the
application of one- and two-dimensional
1
H and
13
C nuclear magnetic resonance spectroscopy and mass
spectrometry, the structures of the O chain and CPS were
determined. The CPS of
A. pleuropneumoniae
serotype 13 was characterized as a teichoic-acid type polymer. The LPS
O antigen was identical to the O-PS produced by
A.
pleuropneumoniae
serotype 7. The CPS has the unique structure of a
1,3-poly(glycerol phosphate) teichoic acid type I polymer and
constitutes the macromolecule defining the
A. pleuropneumoniae
serotype 13 antigenic
specificity.
Sm14 of
Schistosoma mansoni
in Fusion with Tetanus Toxin Fragment C Induces Immunoprotection against Tetanus and Schistosomiasis in Mice
Authors: Abreu Patrícia A. E. , Miyasato Patrícia A. , Vilar Mônica M. , Dias Waldely O. , Ho Paulo L. , Tendler Míriam , Nascimento Ana L. T. O. 
Published: September 2004

ABSTRACT

We have constructed vectors that permit the expression in
Escherichia coli
of
Schistosoma mansoni
fatty acid-binding protein 14 (Sm14) in fusion with the nontoxic, but highly immunogenic, tetanus toxin fragment C (TTFC). The recombinant six-His-tagged proteins were purified by nickel affinity chromatography and used in immunization and challenge assays. Animals inoculated with TTFC in fusion with or coadministered with Sm14 showed high levels of tetanus toxin antibodies, while animals inoculated with Sm14 in fusion with or coadministered with TTFC showed high levels of Sm14 antibodies. In both cases, there were no changes in the type of immune response (Th2) obtained with the fusion proteins compared to those obtained with the nonfused proteins. Mice immunized with the recombinant proteins (TTFC in fusion with or coadministered with Sm14) survived the challenge with tetanus toxin and did not show any symptoms of the disease. Control animals inoculated with either phosphate-buffered saline (PBS) or Sm14 died with severe symptoms of tetanus after 24 h. Mice immunized with the recombinant proteins (Sm14 in fusion with or coadministered with TTFC) showed a 50% reduction in worm burden when they were challenged with
S. mansoni
cercariae, while control animals inoculated with either PBS or TTFC were not protected. The results show that the expression of other antigens in fusion at the carboxy terminus of TTFC is feasible for the development of a multivalent recombinant vaccine.
Experimental Assessment of the Roles of Linear Plasmids lp25 and lp28-1 of
Borrelia burgdorferi
throughout the Infectious Cycle
Authors: Grimm Dorothee , Eggers Christian H. , Caimano Melissa J. , Tilly Kit , Stewart Philip E. , Elias Abdallah F. , Radolf Justin D. , Rosa Patricia A. 
Published: September 2004

ABSTRACT

Borrelia burgdorferi
, which causes Lyme disease in humans, has an unusual genome composed of a linear chromosome and up to 21 extrachromosomal elements. Experimental data suggest that two of these elements, linear plasmids lp25 and lp28-1, play essential roles for infectivity in mice. In this study, we prove the essential natures of these two plasmids by selectively displacing lp25 or lp28-1 in an infectious wild-type clone with incompatible shuttle vectors derived from the native plasmids, rendering the respective transformants noninfectious to mice. Conversely, restoration of plasmid lp25 or lp28-1 in noninfectious clones that naturally lack the corresponding plasmid reestablished infectivity in mice. This approach establishes the ability to manipulate the plasmid content of strains by eliminating or introducing entire plasmids in
B. burgdorferi
and will be valuable in assessing the roles of plasmids even in unsequenced
B. burgdorferi
strains.
Distribution of Surface Protein Variants among Hyperinvasive Meningococci: Implications for Vaccine Design
Authors: Urwin Rachel , Russell Joanne E. , Thompson Emily A. L. , Holmes Edward C. , Feavers Ian M. , Maiden Martin C. J. 
Published: September 2004

ABSTRACT

The bacterium
Neisseria meningitidis
is a major cause of meningitis and septicemia worldwide. Outer membrane proteins (OMPs) are candidates in the search for comprehensive meningococcal vaccines; however, the formulation of OMP vaccines is complicated by antigenic diversity, which is generated by high levels of genetic reassortment and strong positive selection in the meningococcal antigen genes. The genetic and antigenic diversity of three OMPs (FetA, PorA, and PorB) among a global collection of meningococcal isolates representative of the major hyperinvasive clonal complexes was determined. There was evidence for antigenic structuring among the three OMPs that could not be explained purely by descent. These observations violated the predictions of the clonal and epidemic clonal models of population structure but were in concordance with models of strain structure which propose that host immunity selects for nonoverlapping antigen combinations. The patterns of antigenic variant combinations suggested that an OMP-based vaccine with as few as six PorA and five FetA variant sequences could generate homologous immune responses against all 78 isolates examined.
Magnetic Resonance Imaging of Pulmonary Lesions in Guinea Pigs Infected withMycobacterium tuberculosis
Authors: Kraft Susan L. , Dailey Deanna , Kovach Matthew , Stasiak Karen L. , Bennett Jamie , McFarland Christine T. , McMurray David N. , Izzo Angelo A. , Orme Ian M. , Basaraba Randall J. 
Published: September 2004

ABSTRACTWe utilized magnetic resonance imaging to visualize lesions in the lungs of guinea pigs infected by low-dose aerosol exposure toMycobacterium tuberculosis. Lesions were prominent in such images, and colorized three-dimensional reconstructions of images revealed a very uniform distribution in the lungs. Lesion numbers after 1 month were approximately similar to the aerosol exposure algorithm, suggesting that each was established by a single bacterium. Numbers of lesions in unprotected and vaccinated animals were similar over the first month but increased thereafter in the control animals, indicating secondary lesion development. Whereas lesion sizes increased progressively in control guinea pigs, lesions remained small in BCG-vaccinated animals. A prominent feature of the disease pathology in unprotected animals was rapid and severe lymphadenopathy of the mediastinal lymph node cluster, which is paradoxical given the strong state of cellular immunity at this time. Further development of this technical approach could be very useful in tracking lesion size, number, and progression in the search for new tuberculosis vaccines.
Legionella pneumophilaDotU and IcmF Are Required for Stability of the Dot/Icm Complex
Authors: Sexton Jessica A. , Miller Jennifer L. , Yoneda Aki , Kehl-Fie Thomas E. , Vogel Joseph P. 
Published: September 2004

ABSTRACTLegionella pneumophilautilizes a type IV secretion system (T4SS) encoded by 26dot/icmgenes to replicate inside host cells and cause disease. In contrast to all otherL. pneumophila dot/icmgenes,dotUandicmFhave homologs in a wide variety of gram-negative bacteria, none of which possess a T4SS. Instead,dotUandicmForthologs are linked to a locus encoding a conserved cluster of proteins designated IcmF-associated homologous proteins, which has been proposed to constitute a novel cell surface structure. We show here thatdotUis partially required forL. pneumophilaintracellular growth, similar to the known requirement foricmF. In addition, we show thatdotUandicmFare necessary for optimal plasmid transfer and sodium sensitivity, two additional phenotypes associated with a functional Dot/Icm complex. We found that these effects are due to the destabilization of the T4SS at the transition into the stationary phase, the point at whichL. pneumophilabecomes virulent. Specifically, three Dot proteins (DotH, DotG, and DotF) exhibit decreased stability in a ΔdotUΔicmFstrain. Furthermore, overexpression of just one of these proteins, DotH, is sufficient to suppress the intracellular growth defect of the ΔdotUΔicmFmutant. This suggests a model where the DotU and IcmF proteins serve to prevent DotH degradation and therefore function to stabilize theL. pneumophilaT4SS. Due to their wide distribution among bacterial species and their genetic linkage to known or predicted cell surface structures, we propose that this function in complex stabilization may be broadly conserved.
The Pathogenicity Island-Associated K15 Capsule Determinant Exhibits a Novel Genetic Structure and Correlates with Virulence in Uropathogenic
Escherichia coli
Strain 536
Authors: Schneider György , Dobrindt Ulrich , Brüggemann Holger , Nagy Gábor , Janke Britta , Blum-Oehler Gabriele , Buchrieser Carmen , Gottschalk Gerhard , Emödy Levente , Hacker Jörg 
Published: September 2004

ABSTRACT

The K15 capsule determinant of uropathogenic
Escherichia coli
strain 536 (O6:K15:H31) is part of a novel 79.6-kb pathogenicity island (PAI) designated PAI V
536
that is absent from the genome of nonpathogenic
E. coli
K-12 strain MG1655. PAI V
536
shows typical characteristics of a composite PAI that is associated with the
pheV
tRNA gene and contains the
pix
fimbriae determinant as well as genes coding for a putative phosphoglycerate transport system, an autotransporter protein, and hypothetical open reading frames. A gene cluster coding for a putative general secretion pathway system, together with a
kps
K15
determinant, is localized downstream of a truncated
pheV
gene (
′pheV
) also present in this chromosomal region. The distribution of genes present on PAI V
536
was studied by PCR in different pathogenic and nonpathogenic
E. coli
isolates of various sources. Analysis of the 20-kb
kps
locus revealed a so far unknown genetic organization. Generally, the
kps
K15
gene cluster resembles that of group 2 and 3 capsules, where two conserved regions (regions 1 and 3) are located up- or downstream of a highly variable serotype-specific region (region 2). Interestingly, recombination of a group 2 and 3 determinant may have been involved in the evolution of the K15 capsule-encoding gene cluster. Expression of the K15 capsule is important for virulence in a murine model of ascending urinary tract infection but not for serum resistance of
E. coli
strain 536.
Enhanced Lung Injury and Delayed Clearance ofPneumocystis cariniiin Surfactant Protein A-Deficient Mice: Attenuation of Cytokine Responses and Reactive Oxygen-Nitrogen Species
Authors: Atochina Elena N. , Beck James M. , Preston Angela M. , Haczku Angela , Tomer Yaniv , Scanlon Seth T. , Fusaro Trevor , Casey John , Hawgood Samuel , Gow Andrew J. , Beers Michael F. 
Published: September 2004

ABSTRACTSurfactant protein A (SP-A), a member of the collectin family, selectively binds toPneumocystis cariniiand mediates interactions between pathogen and host alveolar macrophages in vitro. To test the hypothesis that mice lacking SP-A have delayed clearance ofPneumocystisorganisms and enhanced lung injury, wild-type C57BL/6 (WT) and SP-A-deficient mice (SP-A−/−) with or without selective CD4+-T-cell depletion were intratracheally inoculated withPneumocystisorganisms. Four weeks later, CD4-depleted SP-A-deficient mice had developed a more severePneumocystisinfection than CD4-depleted WT (P. cariniipneumonia [PCP] scores of 3 versus 2, respectively). Whereas all non-CD4-depleted WT mice were free of PCP, intact SP-A−/−mice also had evidence of increased organism burden.Pneumocystisinfection in SP-A-deficient mice was associated histologically with enhanced peribronchial and/or perivascular cellularity (score of 4 versus 2, SP-A−/−versus C57BL/6 mice, respectively) and a corresponding increase in bronchoalveolar lavage (BAL) cell counts. Increases in SP-D content, gamma interferon, interleukin-4, interleukin-5, and tumor necrosis factor alpha in BAL fluid occurred but were attenuated in PCP-infected SP-A−/−mice compared to WT mice. There were increases in total BAL NO levels in both infected groups, but nitrite levels were higher in SP-A−/−mice, indicating a reduction in production of higher oxides of nitrogen that was also reflected in lower levels of 3-nitrotyrosine staining in the SP-A−/−group. We conclude that despite increases in inflammatory cells, SP-A-deficient mice infected withP. cariniiexhibit an enhanced susceptibility to the organism and attenuated production of proinflammatory cytokines and reactive oxygen-nitrogen species. These data support the concept that SP-A is a local effector molecule in the lung host defense againstP. cariniiin vivo.
A
Vibrio cholerae
Classical TcpA Amino Acid Sequence Induces Protective Antibody That Binds an Area Hypothesized To Be Important for Toxin-Coregulated Pilus Structure
Authors: Taylor Ronald K. , Kirn Thomas J. , Meeks Michael D. , Wade Terri K. , Wade William F. 
Published: September 2004

ABSTRACT

Vibrio cholerae
is a gram-negative bacterium that has been associated with cholera pandemics since the early 1800s. Whole-cell, killed, and live-attenuated oral cholera vaccines are in use. We and others have focused on the development of a subunit cholera vaccine that features standardized epitopes from various
V. cholerae
macromolecules that are known to induce protective antibody responses. TcpA protein is assembled into toxin-coregulated pilus (TCP), a type IVb pilus required for
V. cholerae
colonization, and thus is a strong candidate for a cholera subunit vaccine. Polypeptides (24 to 26 amino acids) in TcpA that can induce protective antibody responses have been reported, but further characterization of their amino acid targets relative to tertiary or quaternary TCP structures has not been done. We report a refinement of the TcpA sequences that can induce protective antibody. One sequence, TcpA 15 (residues 170 to 183), induces antibodies that bind linear TcpA in a Western blot as well as weakly bind soluble TcpA in solution. These antibodies bind assembled pili at high density and provide 80 to 100% protection in the infant mouse protection assay. This is in sharp contrast to other anti-TcpA peptide sera (TcpA 11, TcpA 13, and TcpA 17) that bind very strongly in Western blot and solution assays yet do not provide protection or effectively bind TCP, as evidenced by immunoelectron microscopy. The sequences of TcpA 15 that induce protective antibody were localized on a model of assembled TCP. These sequences are centered on a site that is predicted to be important for TCP structure.
Cryptosporidium parvumat Different Developmental Stages Modulates Host Cell Apoptosis In Vitro
Authors: Mele Raffaella , Gomez Morales Maria Angeles , Tosini Fabio , Pozio Edoardo 
Published: September 2004

ABSTRACTWe studied apoptosis in a human ileocecal adenocarcinoma tumor cell line (HCT-8) infected withCryptosporidium parvum, from 2 to 72 h postinfection (h.p.i.). At 2 h.p.i., the percentage of annexin V-positive cells in the cell culture had increased to 10% compared to 2.5% in noninfected control culture; sorted infected cells expressed mRNA of FasL, the active form of caspase 3, and high caspase 3 activity, whereas the noninfected neighboring cells sorted from the same culture showed no signs of apoptosis. At 24 h.p.i., the percentages of early (annexin V positive) and late (DNA fragment) apoptotic cells were 13 and 2%, respectively, in the entire cell culture, and these percentages were not statistically significant in comparison with those from noninfected control cultures. At this time, sorted infected cells expressed the inactive form of caspase 3, a low caspase 3 activity, and the antiapoptotic protein Bcl-2. Noninfected cells sorted from the same culture showed expression of the active form of caspase 3, a moderate caspase 3 activity, and no Bcl-2 expression. At 48 h.p.i., the percentages of early and late apoptotic cells and caspase 3 activity had increased in the total cell culture, and both sorted infected and noninfected cells showed the active form of caspase 3. These results show thatC. parvum, depending on its developmental stage, can inhibit (at the trophozoite stage) or promote (at the sporozoite and merozoite stages) host cell apoptosis, suggesting that it is able to interact with and regulate the host-cell gene expression.
Expression Profiling Reveals Novel Innate and Inflammatory Responses in the Jejunal Epithelial Compartment during Infection withTrichinella spiralis
Authors: Knight Pamela A. , Pemberton Alan D. , Robertson Kevin A. , Roy Douglas J. , Wright Steven H. , Miller Hugh R. P. 
Published: September 2004

ABSTRACTInfection with intestinal nematodes induces profound pathological changes to the gut that are associated with eventual parasite expulsion. We have applied expression profiling as an initial screening process with oligonucleotide microarrays (Affymetrix MG-U74AV2 gene chips) and time course kinetics to investigate gene transcription triggered by the intraepithelial nematodeTrichinella spiralisin jejunal epithelium from BALB/c mice. Of the 4,114 genes detected, 2,617 were present in all uninfected andT. spiralis-infected replicates, 8% of which were notably upregulated, whereas 12% were downregulated at the time of worm expulsion (day 14 postinfection). Upregulation of goblet cell mucin gene transcripts intestinal mucin gene 3 (MUC3), calcium chloride channel 5 (CLCA5), and goblet cell gene 4 (GOB4) is consistent with enhanced production and alteration of mucus, whereas a 60- to 70-fold upregulation of transcripts for mast cell proteases 1 and 2 (MCPT-1 and -2) is consistent with intraepithelial mucosal mast cell recruitment. Importantly, there was novel expression of sialyltransferase 4C (SIAT4C), small proline-rich protein 2A (SPRR2A), and resistin-like molecule β (RELMβ) on day 14 postinfection. In contrast, DNase I and regenerating protein 3 (REG3) transcripts were substantially downregulated. Time course analyses revealed early (within 48 h of infection) induction of Siat4c, Sprr2A, and Relmβ and later (within 120 h) induction of Mcpt-1 and -2. The findings demonstrate early innate responses and later inflammatory changes within the epithelium. The early epithelial responses may be associated both with repair (Sprr2A) and with the development of innate immunity (Siat4c and Relmβ).
Correct Promoter Control Is Needed for Trafficking of the Ring-Infected Erythrocyte Surface Antigen to the Host Cytosol in Transfected Malaria Parasites
Authors: Rug Melanie , Wickham Mark E. , Foley Michael , Cowman Alan F. , Tilley Leann 
Published: September 2004

ABSTRACT

Following invasion of human erythrocytes, the malaria parasite,
Plasmodium falciparum
, exports proteins beyond the confines of its own plasma membrane to modify the properties of the host red cell membrane. These modifications are critical to the pathogenesis of malaria. Analysis of the
P. falciparum
genome sequence has identified a large number of molecules with putative atypical signal sequences. The signals remain poorly characterized; however, a number of molecules with these motifs localize to the host erythrocyte. To examine the role of these atypical signal sequences in the export of parasite proteins, we have generated transfected parasites expressing a chimeric protein comprising the N-terminal region of the
P. falciparum
ring-infected erythrocyte surface antigen (RESA) appended to green fluorescent protein (GFP). This N-terminal region contains a hydrophobic stretch of amino acids that is presumed to act as a noncanonical secretory signal sequence. Modulation of the timing of transgene expression demonstrates that trafficking of malaria proteins into the host erythrocyte is dependant on both the presence of an appropriate transport signal and the timing of expression. Transgene expression under the control of a trophozoite-specific promoter mistargets the chimeric molecule to the parasitophorous vacuole surrounding the parasite. However, expression of RESA-GFP in schizont stages, under the control of the
RESA
promoter, enables correct trafficking of a population of the chimeric protein to the host erythrocyte.