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acanthamoeba castellanii rna polymerase ii transcription in vitro: accurate initiation at the adenovirus major late promoter.we have developed and characterized an efficient in vitro system from the protozoan, acanthamoeba castellanii, that accurately initiates transcription from the adenovirus-2 major late promoter (admlp). transcription by a. castellanii rna polymerase ii (pol ii) is initiated at the same nucleotide (nt) that is used by hela extracts and is dependent upon adenovirus sequences located between nt -51 and the region around the transcription start point (tsp). the results suggest that the a. castellanii ...19921398130
interaction of legionella pneumophila with acanthamoeba castellanii: uptake by coiling phagocytosis and inhibition of phagosome-lysosome fusion.legionella pneumophila is a facultative intracellular parasite able to survive within both human monocytes and amoebae. we have demonstrated that processing of l. pneumophila by the free-living amoeba acanthamoeba castellanii shows many similarities to the processing of l. pneumophila by monocytes. these similarities include uptake of l. pneumophila by coiling phagocytosis and the subsequent confinement of l. pneumophila in a ribosome-studded phagosome. in addition, as in monocytes, inhibition o ...19968550225
resuscitation of viable but nonculturable legionella pneumophila philadelphia jr32 by acanthamoeba castellanii.legionella pneumophila is an aquatic bacterium and is responsible for legionnaires' disease in humans. free-living amoebae are parasitized by legionellae and provide the intracellular environment required for the replication of this bacterium. in low-nutrient environments, however, l. pneumophila is able to enter a non-replicative viable but nonculturable (vbnc) state. in this study, l. pneumophila philadelphia i jr 32 was suspended in sterilized tap water at 10(4) cells/ml. the decreasing numbe ...19979143134
interaction of mycobacterium avium with environmental amoebae enhances virulence.environmental mycobacteria are a common cause of human infections. recently, contaminated domestic water supplies have been suggested as a potential environmental source of several mycobacterial diseases. since many of these mycobacterial species replicate best intracellularly, environmental hosts have been sought. in the present study, we examined the interaction of mycobacterium avium with a potential protozoan host, the water-borne amoeba acanthamoeba castellanii. we found that m. avium enter ...19979284149
homologs of mitochondrial transcription factor b, sparsely distributed within the eukaryotic radiation, are likely derived from the dimethyladenosine methyltransferase of the mitochondrial endosymbiont.mitochondrial transcription factor b (mttfb), an essential component in regulating the expression of mitochondrial dna-encoded genes in both yeast and humans, is a dimethyladenosine methyltransferase (dmt) that has acquired a secondary role in mitochondrial transcription. so far, mttfb has only been well studied in opisthokonta (metazoan animals and fungi). here we investigate the phylogenetic distribution of mttfb homologs throughout the domain eucarya, documenting the first examples of this pr ...200616533820
use of in vitro assays to determine effects of human serum on biological characteristics of acanthamoeba castellanii.normal human serum inhibits acanthamoeba (encephalitis isolate) binding to and cytotoxicity of human brain microvascular endothelial cells, which constitute the blood-brain barrier. zymographic assays revealed that serum inhibits extracellular protease activities of acanthamoebae. but it is most likely that inhibition of specific properties of acanthamoebae is a consequence of the initial amoebicidal-amoebistatic effects induced by serum. for example, serum exhibited amoebicidal effects; i.e., u ...200616825391
virulence strategies for infecting phagocytes deduced from the in vivo transcriptional program of legionella pneumophila.adaptation to the host environment and exploitation of host cell functions are critical to the success of intracellular pathogens. here, insight to these virulence mechanisms was obtained for the first time from the transcriptional program of the human pathogen legionella pneumophila during infection of its natural host, acanthamoeba castellanii. the biphasic life cycle of l. pneumophila was reflected by a major shift in gene expression from replicative to transmissive phase, concerning nearly h ...200616882028
coevolution between nonhomologous but functionally similar proteins and their conserved partners in the legionella pathogenesis system.legionella pneumophila, the causative agent of legionnaires' disease, and other pathogenic legionella species multiply inside protozoa and human macrophages by using the intracellular multiplication (icm)/defect in organelle trafficking (dot) type-iv secretion system. the icmq protein, which possesses pore-forming activity, and icmr, which regulates the icmq activity, are two essential components of this system. analysis of the region expected to contain these two genes from 29 legionella specie ...200516091472
legionella pneumophila philadelphia-1 tatb and tatc affect intracellular replication and biofilm formation.legionella pneumophila is a facultative intracellular human pathogen and an important cause of legionnaires' disease, a severe form of pneumonia. recently, we showed the presence of a putative twin-arginine translocation (tat) pathway in l. pneumophila philadelphia-1. this secretion pathway is used to transport completely folded proteins across the cytoplasmic membrane. the importance of the tat pathway in l. pneumophila was investigated by constructing a tatb and a tatc mutant. functionality of ...200515883032
significant role for ladc in initiation of legionella pneumophila infection.previously, we identified ladc in a cohort of genes that were present in legionella pneumophila but absent in other legionella species. here we constructed a ladc mutant of l. pneumophila and assessed its ability to replicate in mammalian cell lines and acanthamoeba castellanii. the ladc mutant was recovered in significantly lower numbers than wild-type l. pneumophila at early time points, which was reversed upon transcomplementation with ladc but not ladc(n430a/r434a), encoding a putative catal ...200818426879
molecular and functional characterization of type i signal peptidase from legionella pneumophila.legionella pneumophila is a facultative intracellular gram-negative rod-shaped bacterium that has become an important cause of both community-acquired and nosocomial pneumonia. numerous studies concerning the unravelling of the virulence mechanism of this important pathogen have been initiated. as evidence is now accumulating for the involvement of protein secretion systems in bacterial virulence in general, the type i signal peptidase (lepb) of l. pneumophila was of particular interest. this en ...200415133109
pathogenic acanthamoeba spp secrete a mannose-induced cytolytic protein that correlates with the ability to cause disease.the pathogenesis of acanthamoeba keratitis begins when acanthamoeba trophozoites bind specifically to mannosylated glycoproteins upregulated on the surfaces of traumatized corneal epithelial cells. when acanthamoeba castellanii trophozoites are grown in methyl-alpha-d-mannopyranoside, they are induced to secrete a novel 133-kda protein that is cytolytic to corneal epithelial cells. clinical isolates of acanthamoeba spp., and not the soil isolates, were proficient at producing a mannose-induced p ...200314573643
effects of mannose on acanthamoeba castellanii proliferation and cytolytic ability to corneal epithelial cells.acanthamoeba trophozoites express a mannose binding receptor that facilitates adhesion of trophozoites to mannosylated proteins on corneal epithelial cells. this study was undertaken to determine the role that mannose stimulation has in the amoeba's growth, secreted products, and ability to desquamate the corneal epithelium.200312882791
biochemical and functional analyses of the mip protein: influence of the n-terminal half and of peptidylprolyl isomerase activity on the virulence of legionella pneumophila.the virulence factor mip (macrophage infectivity potentiator) contributes to the intracellular survival of legionella pneumophila, the causative agent of legionnaires' disease. the protein consists of two domains that are connected via a very long alpha-helix (a. riboldi-tunnicliffe et al., nat. struct. biol. 8:779-783, 2001). the fold of the c-terminal domain (residues 100 to 213) is closely related to human fk506-binding protein (fkbp12), and like fkbp12, mip exhibits peptidylprolyl cis/trans ...200312874317
viability of listeria monocytogenes in co-culture with acanthamoeba spp.listeria monocytogenes is a human pathogen, ubiquitous in the environment, and can grow and survive under a wide range of environmental conditions. it contaminates foods via raw materials or food-processing environments. however, the current knowledge of its ecology and, in particular, the mode of environmental survival and transmission of this intracellular pathogen remains limited. research has shown that several intracellular pathogens are able to survive or replicate within free-living amoeb ...200919645820
characterization of a legionella pneumophila rela insertion mutant and toles of rela and rpos in virulence gene expression.to investigate the involvement of rela in the regulation of legionella pneumophila virulence, a deletion substitution was constructed in the rela gene. the rela knockout resulted in an undetectable level of ppgpp in the cells during the stationary phase, but the original level was restored when the rela gene product was supplied on a plasmid. the effect of the rela mutation was examined with two systems that are known to be expressed during the stationary phase in l. pneumophila. pigment product ...200211741845
acanthamoebae bind to rabbit corneal epithelium in vitro.selection of an appropriate animal model is crucial for the investigation of the pathogenesis of acanthamoeba keratitis. to this end, it has been reported that fluorescein isothiocyanate (fitc)-labeled acanthamoeba castellanii bind to human, pig, and hamster corneas, but not to rabbit corneas in organ culture. however, 35s-labeled a. polyphaga and a. culbertsoni have been found to bind to rabbit corneal epithelium grown in tissue culture. the purpose of the current study was to establish whether ...19979286276
infection of acanthamoeba castellanii by chlamydia pneumoniae.chlamydia pneumoniae is an intracellular respiratory pathogen, which, similar to legionella, might have developed mechanisms to escape the intracellular bactericidal activity of both human host cells and amoeba. we therefore investigated the intracellular growth and survival of c. pneumoniae in acanthamoeba castellanii by using cell culture, immunofluorescence microscopy, and electron microscopy. a castellanii was incubated with purified elementary bodies of c. pneumoniae tw 183 at a concentrati ...19979097437
cutaneous acanthamoeba infection in the acquired immunodeficiency syndrome: response to multidrug therapy.acanthamoeba, a free-living ameba of soil and water, produces the rare infections of granulomatous amebic encephalitis and amebic keratitis. we report a 38-year-old white man with the acquired immunodeficiency syndrome (aids) who experienced acanthamoeba infection that presented as multiple skin nodules without associated encephalitis. histologic examination revealed necrotizing granulomatous inflammation with numerous amebic organisms that were cultured and identified as acanthamoeba group 2, p ...19958565615
growth of legionella pneumophila in acanthamoeba castellanii enhances invasion.legionella pneumophila is considered to be a facultative intracellular parasite. therefore, the ability of these bacteria to enter, i.e., invade, eukaryotic cells is expected to be a key pathogenic determinant. we compared the invasive ability of bacteria grown under standard laboratory conditions with that of bacteria grown in acanthamoeba castellanii, one of the protozoan species that serves as a natural host for l. pneumophila in the environment. amoeba-grown l. pneumophila cells were found t ...19948039895
in vitro characterization of acanthamoeba castellanii cytopathic effect.this study examined the mechanism of the cytopathic effect (cpe) of acanthamoeba castellanii on human target cells. pathogenic acanthamoeba trophozoites were incubated with human ocular melanoma (ocm1) cells for 30 min, 1 hr, and 3 hr. the amoebae were treated with a calcium ionophore (a23187), phorbol myristate ester (pma), calcium channel blocker (bepridil), cytochalasin d, and l-leucyl-l-leucine methyl ester (leu-leu-ome). cytolysis was quantified using a spectrophotometric assay. cocultures ...19957623204
acanthamoebiasis and immunosuppression. case report.immunosuppression and debilitating illnesses are occasionally associated with multifocal brain lesions of acanthamoebiasis, an encephalitis distinct from the acute, water-sport related meningoencephalitis caused by naegleria fowler. a 38-year-old man with a renal transplant two and one-half years before his final illness developed pneumonia due to legionella micdadei. candida albicans was isolated from sputum and cytomegalovirus was found in lung and liver biopsies. he had continuous corticoster ...19827108568
purification of a high molecular weight actin filament gelation protein from acanthamoeba that shares antigenic determinants with vertebrate spectrins.i have purified a high molecular weight actin filament gelation protein (gp-260) from acanthamoeba castellanii, and found by immunological cross-reactivity that it is related to vertebrate spectrins, but not to two other high molecular weight actin-binding proteins, filamin or the microtubule-associated protein, map-2. gp-260 was purified by chromatography on deae-cellulose, selective precipitation with actin and myosin-ii, chromatography on hydroxylapatite in 0.6 m kl, and selective precipitati ...19846209283
pathogenic and free-living protozoa cultured from the nasopharyngeal and oral regions of dental patients: ii.protozoa of the nose, mouth, and pharynx of 30 randomly chosen male caries patients at an odontological clinic of the national autonomous university of mexico, in mexico city, were surveyed by culture from swabs. culture tubes from swabs were observed every other day for 5 weeks. pathogens found included entamoeba histolytica, naegleria fowleri, acanthamoeba castellanii, a. culbertsoni, a. polyphaga, and giardia lamblia. such isolations of pathogens suggest that patients may be healthy carriers ...19863956463
in vivo and in vitro collagenolytic activity of acanthamoeba castellanii.axenic cultures of acanthamoeba castellanii contained a collagenolytic enzyme that digested collagen shields and purified collagen in vitro. specificity of biologic activity was determined by the addition of selected enzyme inhibitors to the assays and revealed that the parasite-conditioned medium contained both collagenase and lower concentrations of other proteolytic enzymes. however, most of the collagenolytic and pathogenic activity was directly attributable to specific collagenase. intrastr ...19902173683
restriction enzyme analysis of mitochondrial dna of acanthamoeba strains in japan.eight isolates, identified as either acanthamoeba castellanii or a. polyphaga from human eye infections, contact lens containers, and soil in japan, were characterized by restriction fragment length polymorphisms (rflp) of mitochondrial dna (mtdna). mitochondrial dna was digested with either bgl ii, ecor i, hind iii, hpa i, sca i or xba i, electrophoresed in agarose gels, and stained with ethidium bromide. four distinct rflp phenotypes that refer to the collection of six fragment size patterns o ...19901982316
experimental acanthamoeba infections in mice pretreated with methylprednisolone or tetracycline.human infections due to free-living amebas of the genus acathamoeba have been reported sporadically, occasionally in individuals with underlying diseases. to determine if such infections may be considered opportunistic, groups of laboratory mice were pretreated with either methylprednisolone or tetracycline and inoculated intranasally with 1.075 times 10(4) acanthamoeba castellanii isolated from a natural fresh water well. results were compared with controls receiving either drug or amebas alone ...1978686155
evidence that hsp90 is involved in the altered interactions of acanthamoeba castellanii variants with bacteria.there are many similarities between the interactions of environmental protozoa with pathogenic bacterial species and those observed in mammalian macrophages. since single-celled protozoa predate mammalian hosts, it is likely that interactions in environmental biofilms have selected for many of the bacterial virulence mechanisms responsible for human disease. in order to better understand bacterial-phagocyte interactions, we developed a selection for acanthamoeba castellanii variants that are mor ...200415189979
intracellular multiplication of legionella species and the influence of amoebae on their intracellular growth in human monocytes: mono mac 6 cells and acanthamoeba castellanii as suitable in vitro models.legionellae are important etiological agents of pneumonia. legionella pneumophila (predominantly serogroup 1) is detected in most cases of legionellosis; other species only occasionally cause infections, predominantly in immunocompromized patients. aquiferous technical systems are the primary source of infection (air-conditioning systems, refrigerators, showers, whirlpools, springs, taps, moisturizing equipment, medical nebulizers, and swimming pools). legionellae are present in the water in the ...200415156026
influence of acanthamoeba castellanii on intracellular growth of different legionella species in human monocytes.previous studies using a murine model of coinhalation of legionella pneumophila and hartmannella vermiformis have shown a significantly enhanced intrapulmonary growth of l. pneumophila in comparison to inhalation of legionellae alone (j. brieland, m. mcclain, l. heath, c. chrisp, g. huffnagle, m. legendre, m. hurley, j. fantone, and c. engleberg, infect. immun. 64:2449-2456, 1996). in this study, we introduce an in vitro coculture model of legionellae, mono mac 6 cells (mm6) and acanthamoeba cas ...200010698751
acanthamoeba castellanii metabolites increase the intracellular calcium level and cause cytotoxicity in wish cells.previous studies have shown that trophozoites of the pathogenic free-living amoeba acanthamoeba castellanii rapidly lyse a variety of cells in vitro. however, the role played by cytolitic molecules that may participate in acanthamoebal cytopathogenicity has yet to be completely elucidated. the aim of this work was to study whether soluble molecules released by a. castellanii trophozoites could induce cytopathic effect in human epithelial cells in vitro. the results obtained indicate that a. cast ...19979245619
adherence of acanthamoeba castellanii cysts and trophozoites to unworn soft contact lenses.contact lens-related acanthamoeba keratitis has been associated with the use of soft contact lenses and homemade saline solutions. we studied the adherence of acanthamoeba to unworn extended-wear soft contact lenses on a human corneal isolate of acanthamoeba castellanii suspended in normal saline (cysts, 6.3 x 10(5)/ml; trophozoites, 3.6 x 10(5)/ml). unworn hydrogel contact lenses (polymacon, water content 38.6%; 50 lenses, 400 lens segments) were exposed to a. castellanii cysts or trophozoites ...19892596545
the legionella pneumophila f-box protein lpp2082 (ankb) modulates ubiquitination of the host protein parvin b and promotes intracellular replication.the environmental pathogen legionella pneumophila encodes three proteins containing f-box domains and additional protein-protein interaction domains, reminiscent of eukaryotic scf ubiquitin-protein ligases. here we show that the f-box proteins of l. pneumophila strain paris are dot/icm effectors involved in the accumulation of ubiquitinated proteins associated with the legionella-containing vacuole. single, double and triple mutants of the f-box protein encoding genes were impaired in infection ...201020345489
a case of keratitis due to acanthamoeba in new york, new york, and features of 10 cases.a man in new york, new york, contracted keratitis caused by acanthamoeba castellanii. the diagnosis was delayed because amoebae were not initially suspected as the infectious organism. the culture isolate and the amoebae in corneal sections were identified as a. castellanii by immunofluorescence using antiserum to plasma membranes of this species. with the rapid agar disk diffusion method, the amoebae were shown to e susceptible to pimaricin (0.5%) and resistant to greater than 1,000-micrograms/ ...19816972421
sel1 repeat protein lpne is a legionella pneumophila virulence determinant that influences vacuolar trafficking.the environmental pathogen legionella pneumophila possesses five proteins with sel1 repeats (slrs) from the tetratricopeptide repeat protein family. three of these proteins, lpne, enhc, and lidl, have been implicated in the ability of l. pneumophila to efficiently establish infection and/or manipulate host cell trafficking events. previously, we showed that lpne is important for l. pneumophila entry into macrophages and epithelial cells. in further virulence studies here, we show that lpne is al ...200717893138
in vitro activity of acanthamoeba castellanii on human platelets and erythrocytes.the effect of acanthamoeba on human platelets and erythrocytes has not been fully elucidated. this paper reports that cell-free supernatants prepared from a. castellanii can activate human platelets, causing both a significant increase in the cytosolic free-calcium concentration and platelet aggregation. in addition, we demonstrated that platelet activation depends on the activity of adp constitutively secreted into the medium by trophozoites. this study also showed that a. castellanii can affec ...200919015256
bdha-patd operon as a virulence determinant, revealed by a novel large-scale approach for identification of legionella pneumophila mutants defective for amoeba infection.legionella pneumophila, the causative agent of legionnaires' disease, is an intracellular parasite of eukaryotic cells. in the environment, it colonizes amoebae. after being inhaled into the human lung, the bacteria infect and damage alveolar cells in a way that is mechanistically similar to the amoeba infection. several l. pneumophila traits, among those the dot/icm type ivb protein secretion machinery, are essential for exploiting host cells. in our search for novel legionella virulence factor ...200919411431
balamuthia and acanthamoeba-binding antibodies in west african human sera.little is known about the prevalence of balamuthia mandrillaris amoebae and balamuthia amoebic encephalitis in africa. as an approach, relative concentrations of amoebae-binding serum antibodies (ab) were assessed by flow cytometry using formaldehyde-fixed b. mandrillaris, acanthamoeba lenticulata 72-2 and acanthamoeba castellanii 1bu amoebae for specific ab capture (b.m.-ab, a.l.-ab, a.c.-ab). one hundred and ninety-two sera from west african (côte d'ivoire) donors aged 11-95years (mean 38 a; 5 ...201019896940
identification of antigenic targets for immunodetection of balamuthia mandrillaris infection.the free-living amoeba balamuthia mandrillaris causes granulomatous amoebic encephalitis (gae) in humans. rapid identification of balamuthiasis is critical for effective therapeutic intervention and case management. in the present study we identified target antigens for the development of a serological assay for b. mandrillaris infection. we demonstrated by silver staining that protein profiles for all eight isolates of b. mandrillaris, independent of human or animal origin or geographic origin, ...201121653740
survey of pathogenic free-living amoebae and legionella spp. in mud spring recreation area.acanthamoeba, hartmannella, and naegleria are free-living amoebae, ubiquitous in aquatic environments. several species within these genera are recognized as potential human pathogens. these free-living amoebae may facilitate the proliferation of their parasitical bacteria, such as legionella. in this study, we identified acanthamoeba, hartmannella, naegleria, and legionella using various analytical procedures and investigated their occurrence at a mud spring recreation area in taiwan. we investi ...200919457534
proteomic characterization of the whole secretome of legionella pneumophila and functional analysis of outer membrane vesicles.secretion of effector molecules is one of the major mechanisms by which the intracellular human pathogen legionella pneumophila interacts with host cells during infection. specific secretion machineries which are responsible for the subfraction of secreted proteins (soluble supernatant proteins [ssps]) and the production of bacterial outer membrane vesicles (omvs) both contribute to the protein composition of the extracellular milieu of this lung pathogen. here we present comprehensive proteome ...200818250176
possible roles of phospholipase a(2) in the biological activities of acanthamoeba castellanii (t4 genotype).using phospholipases a(2)-specific spectrophotometric assays, it was shown thata. castellaniilysates and their conditioned medium exhibit phospholipase activities. the extracellular levels of pla(2)detected were significantly reduced compared with the cell-associated enzyme (p<0.05). sphinganine, a pla(2)inhibitor showed robust amoebistatic properties but had no effect on the viability ofa. castellanii. the potency of sphinganine was demonstrated effectively towards purified pla(2)derived from p ...201120650684
[prolactin as a modulator of antiparasitic immunity].prolactin (prl) is a polypeptide hormone of the pituitary origin, that expresses over 300 separate biological activities, including its involvement in the regulation of immune functions. the hormone's immune capacities are related, among others, to comitogenic activity, prevention of immune cell apoptosis, stimulation of interleukins and antibodies production. prolactin acts as a potent positive modulator of immunity to some protozoan parasites. it is well established that the hormone stimulates ...200718441871
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