bluuebunny/crossref_metadata_2025_split huggingface dataset:
Macrophage Class A Scavenger Receptor-Mediated Phagocytosis ofEscherichia coli: Role of Cell Heterogeneity, Microbial Strain, and Culture Conditions In Vitro
Authors: Peiser Leanne , Gough Peter J. , Kodama Tatsuhiko , Gordon Siamon 
Published: July 2002

ABSTRACTMacrophage class A scavenger receptors (SR-AI and SR-AII) contribute to host defense by binding polyanionic ligands such as lipopolysaccharide and lipoteichoic acid. SR-A knockout (SR-A−/−) mice are more susceptible to endotoxic shock andListeria monocytogenesinfection in vivo, possibly due to decreased clearance of lipopolysaccharide and microorganisms, respectively. We have used flow cytometry to analyze the role of SR-A and other scavenger-like receptors in phagocytosis of bacteria in vitro. Chinese hamster ovary cells stably transfected with human SR-A boundEscherichia coliandStaphylococcus aureusbut ingested few organisms. Primary human monocyte-derived macrophages (Mφ) bound and ingestedE. colimore efficiently, and this was partially but selectively blocked by the general SR inhibitor, poly(I). A specific and selective role for SR-A was shown, since bone marrow culture-derived Mφ from SR-A−/−mice ingested fewerE. coliorganisms than did wild-type cells, while uptake of antibody-opsonizedE. coliwas unaffected. SR-A-dependent uptake ofE. colivaried with the bacterial strain; ingestion of DH5α and K1 by SR-A−/−Mφ was reduced by 30 to 60% and 70 to 75%, respectively. Phagocytosis and endocytosis via SR-A were markedly down-modulated when Mφ were plated on serum-coated tissue culture plastic compared to bacteriologic plastic, where cell adhesion is mediated by SR-A and CR3, respectively. This paper demonstrates that SR-A can bind and ingest bacteria directly, consistent with a role in host defense in vivo, and highlights the importance of the source of the Mφ, bacterial strain, and culture conditions on receptor function in vitro.
Human Immune Responses toSchistosoma mansoniVaccine Candidate Antigens
Authors: Ribeiro de Jesus Amélia , Araújo Ilma , Bacellar Olívia , Magalhães Andréa , Pearce Edward , Harn Donald , Strand Mette , Carvalho Edgar M. 
Published: July 2002

ABSTRACTTo determine the naturally occurring immunological responses to theSchistosoma mansoniantigens paramyosin, IrV-5, Sm-23 (MAP-3), and triose phosphate isomerase (MAP-4), a total of 119 subjects from an area of endemicity for schistosomiasis, including “resistant” subjects (n= 17) were evaluated. Specific immunoglobulin G1 (IgG1), IgG2, IgG3, IgG4, and IgA levels for each of the antigens and the cytokine profile in culture supernatants from antigen-stimulated peripheral blood mononuclear cells (PBMC) were determined. Although all the subjects had a high degree of contaminated water exposure, their infection levels were variable (0 to 1,128 eggs/g of stool). There were direct correlations between infection levels and levels of SWAP- and paramyosin-specific IgG1 and IgG4 (P< 0.05). However, an inverse correlation between infection levels and specific IgG2 to IrV-5 (P< 0.01) was observed. The evaluation of the cytokine profile (interleukin 5 [IL-5], IL-10, gamma interferon [IFN-γ], and tumor necrosis factor alpha) in response to these antigens showed inverse correlations between the degree of infection and IFN-γ levels in PBMC supernatants stimulated with paramyosin (P< 0.05) and IrV-5 (P< 0.01). Additionally, inverse correlations between the degree of infection and IL-5 levels in MAP-3- and MAP-4-stimulated PBMC supernatants (P< 0.01) were found. Logistic regression analysis was performed to adjust the results of cytokine profile by age. IL-5 production in MAP-3-stimulated PBMC supernatants was associated with lower infection levels (odds ratio = 11.2 [95% confidence interval, 2.7 to 45.8]).
CS22, a Novel Human Enterotoxigenic
Escherichia coli
Adhesin, Is Related to CS15
Authors: Pichel Mariana , Binsztein Norma , Viboud Gloria 
Published: July 2002

ABSTRACT

Enterotoxigenic
Escherichia coli
(ETEC) expresses a broad spectrum of O:H antigens. Serogroup O20 is one of the most prevalent among the ETEC strains lacking any of the defined colonization factors (CFs), in Argentina. An O20:H− strain, ARG-3, adhered to Caco-2 cells and exhibited a thermoregulated 15.7-kDa protein band upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). An antiserum against this protein inhibited ARG-3 adhesion to Caco-2 cells and bound to very thin fibrilla-like structures on the bacterial surface. A 15.7-kDa protein-defective mutant failed to adhere to Caco-2 cells and lacked immunogold-labeled surface structures. The N-terminal amino acid sequence of the structural subunit showed 95% homology to that of CS15 of ETEC (former antigen 8786) and 65% homology with fimbria SEF14 of
Salmonella enterica
serovar Enteritidis. Nevertheless, the molecular size of ARG-3 adhesin was different from that of CS15, as revealed by SDS-PAGE and mass spectrometry. Both proteins are immunologically related, yet not identical, since an antiserum against the 15.7-kDa protein reacted solely with ARG-3 after absorption with bacteria bearing CS15. Moreover, only under low stringency conditions could DNA from strain ARG-3 be amplified by PCR using primers derived from the
nfaA
sequence of CS15. Thus, from the DNA sequence obtained from the ARG-3 PCR product, it could be deduced that the subunit protein differed in 30 residues from that of CS15. ARG-3 adhesin was found in 60% of the O20:H- CF-negative ETEC strains from Argentina; however, it appeared restricted to this serotype. We propose the designation CS22 for the herein identified nonfimbrial adhesin of human ETEC.
Antibody Is Required for Protection against Virulent but Not AttenuatedSalmonella entericaSerovar Typhimurium
Authors: McSorley Stephen J. , Jenkins Marc K. 
Published: July 2002

ABSTRACTResolution of infection with attenuatedSalmonellais an active process that requires CD4+T cells. Here, we demonstrate that costimulation via the surface molecule CD28, but not antibody production by B cells, is required for clearance of attenuatedaroA Salmonella entericaserovartyphimurium. In contrast, specific antibody is critical for vaccine-induced protection against virulent bacteria. Therefore, CD28+CD4+T cells are sufficient for clearance of avirulentSalmonellain naive hosts, whereas CD4+T cells and specific antibodies are required for protection from virulentSalmonellain immune hosts.
Antibodies against Thrombospondin-Related Anonymous Protein Do Not InhibitPlasmodiumSporozoite Infectivity In Vivo
Authors: Gantt Soren , Persson Cathrine , Rose Keith , Birkett Ashley J. , Abagyan Ruben , Nussenzweig Victor 
Published: July 2002

ABSTRACTThrombospondin-related anonymous protein (TRAP), a candidate malaria vaccine antigen, is required forPlasmodiumsporozoite gliding motility and cell invasion. For the first time, the ability of antibodies against TRAP to inhibit sporozoite infectivity in vivo is evaluated in detail. TRAP contains an A-domain, a well-characterized adhesive motif found in integrins. We modeled here a three-dimensional structure of the TRAP A-domain ofPlasmodium yoeliiand located regions surrounding the MIDAS (metal ion-dependent adhesion site), the presumed business end of the domain. Mice were immunized with constructs containing these A-domain regions but were not protected from sporozoite challenge. Furthermore, monoclonal and rabbit polyclonal antibodies against the A-domain, the conserved N terminus, and the repeat region of TRAP had no effect on the gliding motility or sporozoite infectivity to mice. TRAP is located in micronemes, secretory organelles of apicomplexan parasites. Accordingly, the antibodies tested here stained cytoplasmic TRAP brightly by immunofluorescence. However, very little TRAP could be detected on the surface of sporozoites. In contrast, a dramatic relocalization of TRAP onto the parasite surface occurred when sporozoites were treated with calcium ionophore. This likely mimics the release of TRAP from micronemes when a sporozoite contacts its target cell in vivo. Contact with hepatoma cells in culture also appeared to induce the release of TRAP onto the surface of sporozoites. If large amounts of TRAP are released in close proximity to its cellular receptor(s), effective competitive inhibition by antibodies may be difficult to achieve.
Toxoplasma gondiiUses Sulfated Proteoglycans for Substrate and Host Cell Attachment
Authors: Carruthers Vern B. , Håkansson Sebastian , Giddings Olivia K. , Sibley L. David 
Published: July 2002

ABSTRACTToxoplasma gondiiis an obligate intracellular parasite that actively invades a wide variety of vertebrate cells, although the basis of this pervasive cell recognition is not understood. We demonstrate here that binding to the substratum and to host cells is partially mediated by interaction with sulfated glycosaminoglycans (GAGs). Addition of excess soluble GAGs blocked parasite attachment to serum-coated glass, thereby preventing gliding motility of extracellular parasites. Similarly, excess soluble GAGs decreased the attachment of parasites to human host cells from a variety of lineages, including monocytic, fibroblast, endothelial, epithelial, and macrophage cells. The inhibition of parasite attachment by GAGs was observed with heparin and heparan sulfate and also with chondroitin sulfates, indicating that the ligands for attachment are capable of recognizing a broad range of GAGs. The importance of sulfated proteoglycan recognition was further supported by the demonstration that GAG-deficient mutant host cells, and wild-type cells treated enzymatically to remove GAGs, were partially resistant to parasite invasion. Collectively, these studies reveal that sulfated proteoglycans are one determinant used for substrate and cell recognition byToxoplasma. The widespread distribution of these receptors may contribute to the broad host and tissue ranges of this highly successful intracellular parasite.
Plasmodium chabaudi
-Infected Erythrocytes Adhere to CD36 and Bind to Microvascular Endothelial Cells in an Organ-Specific Way
Authors: Mota Maria M. , Jarra William , Hirst Elizabeth , Patnaik Pradeep K. , Holder Anthony A. 
Published: July 2002

ABSTRACT

Adherence of erythrocytes infected with
Plasmodium falciparum
to microvascular endothelial cells (sequestration) is considered to play an important role in parasite virulence and pathogenesis. However, the real importance of sequestration for infection and disease has never been fully assessed. The absence of an appropriate in vivo model for sequestration has been a major barrier. We have examined the rodent malaria parasite
Plasmodium chabaudi chabaudi
AS in mice as a potential model. Erythrocytes infected with this parasite adhere in vitro to purified CD36, a critical endothelium receptor for binding
P. falciparum
-infected erythrocytes.
P. c. chabaudi
-infected erythrocytes adhere in vitro to endothelial cells in a gamma interferon-dependent manner, suggesting the involvement of additional adhesion molecules in the binding process, as is also the case with
P. falciparum
-infected cells. Furthermore, plasma or sera from infected and hyperimmune mice, respectively, have the ability to block binding of infected erythrocytes to endothelial cells. In vivo, erythrocytes containing mature
P. c. chabaudi
parasites are sequestered from the peripheral circulation. Sequestration is organ specific, occurring primarily in the liver, although intimate contact between infected erythrocytes and endothelial cells is also observed in the spleen and brain. The results are discussed in the context of the use of this model to study (i) the relationship between endothelial cell activation and the level of sequestration and (ii) the primary function of sequestration in malaria infection.
Ultrastructure of
Rickettsia rickettsii
Actin Tails and Localization of Cytoskeletal Proteins
Authors: Van Kirk Levi S. , Hayes Stanley F. , Heinzen Robert A. 
Published: July 2002

ABSTRACT

Actin-based motility (ABM) is a mechanism for intercellular spread that is utilized by vaccinia virus and the invasive bacteria within the genera
Rickettsia
,
Listeria
, and
Shigella
. Within the
Rickettsia
, ABM is confined to members of the spotted fever group (SFG), such as
Rickettsia rickettsii
, the agent of Rocky Mountain spotted fever. Infection by each agent induces the polymerization of host cell actin to form the typical F (filamentous)-actin comet tail. Assembly of the actin tail propels the pathogen through the host cytosol and into cell membrane protrusions that can be engulfed by neighboring cells, initiating a new infectious cycle. Little is known about the structure and morphogenesis of the
Rickettsia rickettsii
actin tail relative to
Shigella
and
Listeria
actin tails. In this study we examined the ultrastructure of the rickettsial actin tail by confocal, scanning electron, and transmission electron microscopy. Confocal microscopy of rhodamine phalloidin-stained infected Vero cells revealed the typhus group rickettsiae,
Rickettsia prowazekii
and
Rickettsia typhi
, to have no actin tails and short (∼1- to 3-μm) straight or hooked actin tails, respectively. The SFG rickettsia,
R. rickettsii
, displayed long actin tails (>10 μm) that were frequently comprised of multiple, distinct actin bundles, wrapping around each other in a helical fashion. Transmission electron microscopy, in conjunction with myosin S1 subfragment decoration, revealed that the individual actin filaments of
R. rickettsii
tails are >1 μm long, arranged roughly parallel to one another, and oriented with the fast-growing barbed end towards the rickettsial pole. Scanning electron microscopy of intracellular rickettsiae demonstrated
R. rickettsii
to have polar associations of cytoskeletal material and
R. prowazekii
to be devoid of cytoskeletal interactions. By indirect immunofluorescence, both
R. rickettsii
and
Listeria monocytogenes
actin tails were shown to contain the cytoskeletal proteins vasodilator-stimulated phosphoprotein profilin, vinculin, and filamin. However, rickettsial tails lacked ezrin, paxillin, and tropomyosin, proteins that were associated with actin tails of cytosolic or protrusion-bound
Listeria
. The unique ultrastructural and compositional characteristics of the
R. rickettsii
actin tail suggest that rickettsial ABM is mechanistically different from previously described microbial ABM systems.
Initial Characterization of CST1, a
Toxoplasma gondii
Cyst Wall Glycoprotein
Authors: Zhang Yi Wei , Halonen Sandra K. , Ma Yan Fen , Wittner Murray , Weiss Louis M. 
Published: July 2002

ABSTRACT

Toxoplasma gondii
is an important protozoan pathogen of humans that can cause encephalitis in immunocompromised individuals such as those with AIDS. This encephalitis is due to reactivation of latent infection in
T. gondii
-seropositive patients. Latent organisms survive within tissue cysts, which are specialized parasitophorous vacuoles containing bradyzoites. The cyst wall of this structure is produced by modification of the parasitophorous vacuole by the parasite and is important in cyst survival. The components of the cyst wall have been poorly characterized. By using immunofluorescence and immunoelectron microscopy, we have identified a monoclonal antibody (MAb 93.18) that reacts with the cyst wall. This antibody recognizes a 116-kDa glycoprotein, which we have termed CST1, containing sugar residues that bind
Dolichos biflorans
lectin (DBA). CST1 is distinct from
T. gondii
antigen labeled with succinyl
Triticum vulgare
lectin (S-WGA) and represents the major DBA-binding component in
T. gondii
. The carbohydrate components of the tissue cyst, such as CST1, are probably important in both providing stability and facilitating persistence in its host. As is seen in the carbohydrate capsules of fungi, glycoproteins in the
T. gondii
cyst wall may protect cysts from the immune response of the host. Further characterization of the formation of the cyst wall and its components should lead to insights into the mechanism of tissue cyst persistence and may suggest novel therapeutic approaches to eliminate tissue cysts of this organism.
Cytotoxic Necrotizing Factor Type 1-PositiveEscherichia coliCauses Increased Inflammation and Tissue Damage to the Prostate in a Rat Prostatitis Model
Authors: Rippere-Lampe Karen E. , Lang Michael , Ceri Howard , Olson Merle , Lockman Hank A. , O'Brien A. D. 
Published: July 2002

ABSTRACTInfection of rat prostates with cytotoxic necrotizing factor type 1 (CNF1)-positive uropathogenicEscherichia colicaused more inflammation-mediated morphological and histological tissue damage than did infection with isogenic CNF1-negative mutants. These striking differences occurred despite the finding that bacterial counts for the strain pairs were indistinguishable. We conclude that CNF1 contributes toE.colivirulence in a model of acute prostatitis. To our knowledge, the results of this study provide the first demonstration of a role for any uropathogenicE.colivirulence factor in acute prostatitis.
RecombinantYersiniaYopT Leads to Uncoupling of RhoA-Effector Interaction
Authors: Sorg Isabel , Goehring Udo-Michael , Aktories Klaus , Schmidt Gudula 
Published: July 2002

ABSTRACTYersinia enterocolitica, Yersinia pseudotuberculosis, andYersinia pestisdeliver different Yop (Yersiniaouter proteins) effector proteins into mammalian cells by a type III secretion mechanism. Recently, it was shown thatYersiniaproducing YopT leads to disruption of the actin cytoskeleton of HeLa cells (M. Iriarte and G. R. Cornelis, Mol. Microbiol. 29:915–929, 1998). To analyze the molecular mechanism of YopT, we cloned and expressed YopT as a glutathioneS-transferase fusion protein. Recombinant YopT caused rounding up of embryonic bovine lung cells and redistribution of the actin cytoskeleton rapidly after microinjection. TheEscherichia colicytotoxic necrotizing factor (CNF1), which constitutively activates Rho proteins, was not able to inhibit or revert YopT-induced cell rounding. YopT caused release of RhoA from embryonic bovine lung membranes and released recombinant isoprenylated RhoA from artificial PE or PE/PIP2 vesicles. Incubation of lysate or cytosol with YopT caused inhibition of the RhoA-rhotekin interaction but led to increased RhoA-RhoGDI interaction. It is suggested that inhibition of the interaction between RhoA and effectors is the underlying mechanism of the YopT action on the cytoskeleton.
Expression of Chemokine Genes in Human Dermal Microvascular Endothelial Cell Lines Infected withOrientia tsutsugamushi
Authors: Cho Nam-Hyuk , Seong Seung-Yong , Choi Myung-Sik , Kim Ik-Sang 
Published: July 2002

ABSTRACTScrub typhus, caused byOrientia tsutsugamushi, is characterized by local as well as systemic inflammatory manifestations. The main pathologic change is focal or disseminated multiorgan vasculitis, which is caused by the destruction of endothelial cells and perivascular infiltration of leukocytes. We investigated the regulation of chemokine induction in transformed human dermal microvascular endothelial cells (HMEC-1) in response toO. tsutsugamushiinfection. The monocyte chemoattractant protein-1 (MCP-1) and interleukin 8 (IL-8) mRNAs were induced, and their levels showed a transitory peak at 3 and 6 h, respectively. The RANTES transcript was detected at 6 h after infection, with increased levels evident by 48 h. The induction of the MCP-1 and IL-8 genes was not blocked by cycloheximide, suggesting that de novo protein synthesis of host cell proteins is not required for their transcriptional activation. Heat- or UV-inactivatedO. tsutsugamushiinduced a similar extent of MCP-1 and IL-8 responses. The induction of MCP-1 and IL-8 transcripts in the endothelial cells byO. tsutsugamushiwas not blocked by the inhibitors of NF-κB. Furthermore, the activation of NF-κB was not detected in HMEC-1 stimulated withO. tsutsugamushi. These results demonstrate that heat-stable molecules ofO. tsutsugamushiinduce the MCP-1 and IL-8 genes and the induction of the chemokine genes may be mediated by an NF-κB independent mechanism. We also showed that another major transcription factor, activator protein-1 (AP-1), was up-regulated in HMEC-1 afterO. tsutsugamushiinfection. This suggests the possible involvement of AP-1 in the chemokine gene expression.
Streptococcus parasanguis
Fimbria-Associated Adhesin Fap1 Is Required for Biofilm Formation
Authors: Froeliger Eunice H. , Fives-Taylor Paula 
Published: July 2002

ABSTRACT

The sanguis streptococci are primary colonizers of the tooth surface and thus form the foundation for the complex multiple species biofilm known as dental plaque. In addition, these bacteria can colonize native and prosthetic heart valves and are a common cause of endocarditis. Little is known about the molecular mechanisms governing multiple or single species biofilm development within this group of organisms. Using an in vitro assay for biofilm formation, we determined that (i)
Streptococcus parasanguis
FW213 can form biofilms on inert surfaces such as polystyrene and (ii) environmental and nutritional factors, such as glucose, affect
S. parasanguis
biofilm formation. Several isogenic mutants of FW213 were tested in the biofilm assay. Strains containing mutations in
fap1
, a gene encoding a protein required for assembly of fimbriae, were deficient in biofilm formation. Mutants defective in
recA
, PepO endopeptidase activity, or the production of a fimbriae-associated protein, FimA, were still capable of biofilm formation. Phase-contrast microscopy was used to follow biofilm development by wild-type and
fap1
mutant strains on plastic coverslips over time. Wild-type FW213 attached to the surface, formed aggregates of cells, and eventually formed a dense layer of cells that included microcolonies. In contrast, few
fap1
mutant cells were observed attached to the surface, and no cell aggregates or microcolonies were formed. These results suggest that the long peritrichous fimbriae of FW213 are critical for the formation of biofilms on solid surfaces.
Curli Fibers Mediate Internalization of
Escherichia coli
by Eukaryotic Cells
Authors: Gophna U. , Barlev M. , Seijffers R. , Oelschlager T. A. , Hacker J. , Ron E. Z. 
Published: July 2002

ABSTRACT

Curli fibers are adhesive surface fibers expressed by
Escherichia coli
and
Salmonella enterica
that bind several host extracellular matrix and contact phase proteins and were assumed to have a role in pathogenesis. The results presented here suggest that one such role is internalization into host cells. An
E. coli
K-12 strain transformed with a low-copy vector containing the gene cluster encoding curli fibers (
csg
operon) was internalized by several lines of eukaryotic cells. The internalization could be correlated with a high level of curli fiber expression and was abolished by disruption of the
csg
operon. The ability to be internalized by eukaryotic cells could be conferred even by the curli fiber gene cluster of a noninvasive K-12 strain, but the homologous
csg
cluster from a virulent septicemic
E. coli
isolate mediated a higher level of internalization. The finding that curli fibers promote bacterial internalization indicates a new role for curli fibers in pathogenesis.