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Results for “Virulence profiling”

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At least 901 records · Page 50Linked to original sources
PubMed2006

SseL is a salmonella-specific translocated effector integrated into the SsrB-controlled salmonella pathogenicity island 2 type III secretion system.

Bacterial pathogens use horizontal gene transfer to acquire virulence factors that influence host colonization, alter virulence traits, and ultimately shape the outcome of disease following infection. One hallmark of the host-pathogen interaction is the prokaryotic type III secretion system that translocates virulence factors into host cells during infection. Salmonella enterica possesses two type III secretion systems that are utilized during host colonization and intracellular replication. Salmonella pathogenicity island 2 (SPI2) is a genomic island containing approximately 30 contiguous genes required to assemble a functional secretion system including the two-component regulatory system called SsrA-SsrB that positively regulates transcription of the secretion apparatus. We used transcriptional profiling with DNA microarrays to search for genes that coregulate with the SPI2 type III secretion machinery in an SsrB-dependent manner. Here we report the identification of a Salmonella-specific translocated effector called SseL that is required for full virulence during murine typhoid-like disease. Analysis of infected macrophages using fluorescence-activated cell sorting revealed that sseL is induced inside cells and requires SsrB for expression. SseL is retained predominantly in the cytoplasm of infected cells following translocation by the type III system encoded in SPI2. Animal infection experiments with sseL mutant bacteria indicate that integration of SseL into the SsrB response regulatory system contributes to systemic virulence of this pathogen.

Animals↗
PubMed2026

Functional characterization of SHC-like triterpene cyclase genes in azole response and virulence-related traits of Aspergillus fumigatus.

Aspergillus fumigatus is a major opportunistic fungal pathogen, and increasing azole resistance poses a challenge for aspergillosis treatment. Squalene is an upstream precursor of ergosterol biosynthesis and may also be utilized by SHC-like triterpene cyclases, suggesting a potential link between squalene-associated metabolism, membrane adaptation, and azole response. However, the roles of SHC-like triterpene cyclase genes in A. fumigatus remain unclear. Here, we characterized three candidates, shc1, shc2, and shc3, using comparative bioinformatic analysis, gene deletion, phenotypic assays, azole susceptibility testing, transcriptomics, and host-interaction models. Sequence, genomic-context, phylogenetic, and structural analyses suggested divergence among the three candidates. Individual shc deletion caused limited effects on vegetative growth, whereas loss of shc1 mildly reduced susceptibility to voriconazole and posaconazole, as reflected by twofold MIC increases and lower inhibition rates. Transcriptomic analysis revealed distinct remodeling patterns, with Δshc3 showing the broadest transcriptional changes despite no detectable MIC shift. Targeted metabolite profiling and PI uptake analysis further supported an association between shc deletion, sterol/hopane-type triterpenoid balance, and membrane-associated properties. shc deletion also altered epithelial cell interaction phenotypes, while Δshc1 showed reduced lethality in Galleria mellonella. In clinical isolates, elevated shc transcription was associated with azole-resistant backgrounds. These findings suggest functional diversification among SHC-like triterpene cyclase genes and indicate that shc1 may contribute to azole-associated adaptation and virulence-related traits in A. fumigatus.

Aspergillus fumigatus↗
PubMed2006

The YfgL lipoprotein is essential for type III secretion system expression and virulence of Salmonella enterica Serovar Enteritidis.

Salmonella enterica, like many gram-negative pathogens, uses type three secretion systems (TTSS) to infect its hosts. The three TTSS of Salmonella, namely, TTSS-1, TTSS-2, and flagella, play a major role in the virulence of this bacterium, allowing it to cross the intestinal barrier and to disseminate systemically. Previous data from our laboratory have demonstrated the involvement of the chromosomal region harboring the yfgL, engA, and yfgJ open reading frames in S. enterica serovar Enteritidis virulence. Using microarray analysis and real-time reverse transcription-PCR after growth of bacterial cultures favorable for either TTSS-1 or TTSS-2 expression, we show in this study that the deletion in S. enterica serovar Enteritidis of yfgL, encoding an outer membrane lipoprotein, led to the transcriptional down-regulation of most Salmonella pathogenicity island 1 (SPI-1), SPI-2, and flagellar genes encoding the TTSS structural proteins and effector proteins secreted by these TTSS. In line with these results, the virulence of the DeltayfgL mutant was greatly attenuated in mice. Moreover, even if YfgL is involved in the assembly of outer membrane proteins, the regulation of TTSS expression observed was not due to an inability of the Delta yfgL mutant to assemble TTSS in its membrane. Indeed, when we forced the transcription of SPI-1 genes by constitutively expressing HilA, the secretion of the TTSS-1 effector protein SipA was restored in the culture supernatant of the mutant. These results highlight the crucial role of the outer membrane lipoprotein YfgL in the expression of all Salmonella TTSS and, thus, in the virulence of Salmonella. Therefore, this outer membrane protein seems to be a privileged target for fighting Salmonella.

Animals↗
PubMed2004

Streptococcus pyogenes fibronectin-binding protein F2: expression profile, binding characteristics, and impact on eukaryotic cell interactions.

Some Streptococcus pyogenes (group A streptococci, GAS) strains have previously been shown to express the fibronectin-binding protein F2 instead of the functionally related but structurally dissimilar protein F1/SfbI. In this study, recombinant N-terminal and C-terminal portions and the two fibronectin-binding domains of protein F2 were used to assess affinity parameters of the interaction with fibronectin and its N-terminal 70-, 30-, and 45-kDa fragments. The association and dissociation equilibrium constants for both binding domains were in the nanomolar range, although the repeat domain of protein F2 exceeded the affinity of the unique domain by up to one order magnitude. Both domains primarily interacted with the 30-kDa fibronectin fragment. Using a prtF2 gene isogenic mutant of a serotype M49 GAS strain that does not harbor the protein F1/SfbI gene, the attachment values of whole bacteria to immobilized fibronectin and to HEp-2 epithelial cells were found to be 6- and 2-fold decreased, respectively. Reduction of prtF2 mutant internalization rates for eukaryotic cells exceeded the reduction of attachment rates, indicating an independent contribution of protein F2 to both processes. The prtF2 transcription and protein F2 expression profiles documented maximum expression at the transition to the stationary phase especially under aerobic growth condition. The protein F2 function as the major fibronectin-binding adhesin in a subset of GAS strains, its expression pattern, and highly specific interaction with fibronectin would be consistent with a status as an indispensable virulence factor for both earlier and later pathogenetic stages of GAS superficial infections.

Adhesins, Bacterial↗
PubMed2005

Iron and fur regulation in Vibrio cholerae and the role of fur in virulence.

Regulation of iron uptake and utilization is critical for bacterial growth and for prevention of iron toxicity. In many bacterial species, this regulation depends on the iron-responsive master regulator Fur. In this study we report the effects of iron and Fur on gene expression in Vibrio cholerae. We show that Fur has both positive and negative regulatory functions, and we demonstrate Fur-independent regulation of gene expression by iron. Nearly all of the known iron acquisition genes were repressed by Fur under iron-replete conditions. In addition, genes for two newly identified iron transport systems, Feo and Fbp, were found to be negatively regulated by iron and Fur. Other genes identified in this study as being induced in low iron and in the fur mutant include those encoding superoxide dismutase (sodA), fumarate dehydratase (fumC), bacterioferritin (bfr), bacterioferritin-associated ferredoxin (bfd), and multiple genes of unknown function. Several genes encoding iron-containing proteins were repressed in low iron and in the fur mutant, possibly reflecting the need to reserve available iron for the most critical functions. Also repressed in the fur mutant, but independently of iron, were genes located in the V. cholerae pathogenicity island, encoding the toxin-coregulated pilus (TCP), and genes within the V. cholerae mega-integron. The fur mutant exhibited very weak autoagglutination, indicating a possible defect in expression or assembly of the TCP, a major virulence factor of V. cholerae. Consistent with this observation, the fur mutant competed poorly with its wild-type parental strain for colonization of the infant mouse gut.

Bacterial Proteins↗
PubMed2006

Transcriptional and translational expression patterns associated with immobilized growth of Campylobacter jejuni.

Although Campylobacter jejuni is a leading cause of food-borne illness, little is known about the mechanisms by which this pathogen mediates prolonged environmental survival or host cell virulence. Although these behaviours represent distinct phenotypes, they share a common requirement of an immobilized state. In order to understand the cellular mechanisms that facilitate a surface-associated lifestyle, transcriptional and translational expression profiles were determined for sessile and planktonic C. jejuni. These investigations indicate that the immobilized bacteria undergo a shift in cellular priorities away from metabolic, motility and protein synthesis capabilities towards emphasis on iron uptake, oxidative stress defence and membrane transport. This pattern of expression partially overlaps those reported for Campylobacter during host colonization, as well as for other species of bacteria involved in biofilms, highlighting common adaptive responses to the conserved challenges within each of these phenotypes. The adaptation of Campylobacter to immobilized growth may represent a quasi-differentiated state that functions as a foundation for further specialization towards phenotypes such as biofilm formation or host cell virulence.

Bacterial Adhesion↗
PubMed1988

Marek's disease virus serotype-1 antigens A and B and their unglycosylated precursors detected by Western blot analysis of infected cells.

The antigenic profile of cell cultures infected with Marek's disease virus (MDV) was determined by the immunoblotting method using convalescent immune serum obtained from chickens that survived infection with MDV strain GA5. The MDV antigen profile in infected cell lysates could be accurately determined since this method has advantages over the immunoprecipitation method used in other studies. We studied six very virulent MDV isolates and the prototype of serotype 1 MDV, the GA5 strain. Immunoblots of NaDodSO4-polyacrylamide gel electrophoresis (PAGE) performed under reducing conditions revealed a main viral antigen (B) of 120-130 kD, which was present in all cell lysates infected with MDV isolates. Analysis of infected cell proteins by NaDodSO4-PAGE performed under nonreducing conditions, revealed a 205 kD major MDV antigen, which, under reducing conditions, was identical to the 130 kD major antigen. The unglycosylated precursors of the major MDV antigens were elucidated. Two polypeptides of 43 and 45 kD were found to be the unglycosylated precursors of MDV antigen A (the glycosylated form of which appears in 4 distinct bands). The unglycosylated precursors of the MDV major antigen B were found to be three polypeptides of 80, 110, and 125 kD.

Animals↗
PubMed2006

Expression of Plasmodium falciparum genes involved in erythrocyte invasion varies among isolates cultured directly from patients.

Plasmodium falciparum merozoites invade erythrocytes using a range of alternative ligands that includes erythrocyte binding antigenic proteins (EBAs) and reticulocyte binding protein homologues (Rh). Variation in the expression of some of these genes among culture-adapted parasite lines correlates with the use of different erythrocyte receptors. Here, expression profiles of four Rh genes and eba175 are analysed in a sample of 42 isolates cultured from malaria patients in Kenya. The profiles cluster into distinct groups, largely because of very strong negative correlations between the levels of expression of particular gene pairs (Rh1 versus Rh2b, eba175 versus Rh2b, and eba175 versus Rh4), previously associated with alternative invasion pathways in culture-adapted parasite lines. High levels of eba175 are seen in isolates in expression profile group I, and may be associated with sialic acid-dependent invasion. Groups II and III are, respectively, characterized by high levels of Rh2b and Rh4, and are more likely to be associated with sialic acid-independent invasion.

Animals↗
PubMed1998

Molecular characterization of Salmonella enterica subsp. enterica serovar Typhimurium DT009 isolates: differentiation of the live vaccine strain Zoosaloral from field isolates.

A total of 25 epidemiologically unrelated Salmonella enterica subsp. enterica (S.) serovar Typhimurium DT009 isolates from various human and animal sources, the original S. Typhimurium DT009 Zoosaloral live vaccine strain and two Zoosaloral strains reisolated from vaccinated chickens were investigated by various molecular typing methods (I) to determine the most suitable method or combination of methods for the differentiation of DT009 field isolates and (II) to investigate which molecular methods are suitable to differentiate the Zoosaloral live vaccine strain from field isolates of the same phage type. Based on the results of plasmid profile analysis, IS200 typing and macrorestriction analysis with XbaI, SpeI and BlnI, the 28 S. Typhimurium DT009 isolates were assigned to 16 different genomic groups, one of which was exclusively represented by the original and the reisolated Zoosaloral strains. IS200 typing was the most discriminatory single method for the differentiation of the DT009 isolates followed by plasmid profile analysis and BlnI-macrorestriction analysis. The Zoosaloral vaccine strain differed from the DT009 field isolates by its unique HindIII-fragment pattern of the virulence plasmid and by its unique SpeI-macrorestriction pattern.

Animals↗
PubMed2026

Typhoid Toxin of Salmonella enterica Induces ISG15 Responses Mediating Host Cell Survival and Counteracting Intracellular Infection.

The typhoid toxin is a secreted virulence factor of typhoidal serovars of the bacterial pathogen Salmonella enterica implicated in typhoid fever and chronic infections. The toxin causes a DNA damage response in human cells, characterised by cell-cycle arrest and cellular distension, resulting in cellular senescence and increased bacterial burden. To better understand host responses to typhoid toxin, we performed a transcriptomic analysis of intoxicated host cells and found that the toxin induced expression of genes relating to the type-I interferon response, including the ubiquitin-like protein ISG15. ISG15 was upregulated in a STING-dependent manner, reduced bacterial burden, and was found to be critical to host cell survival in response to the typhoid toxin and interferon. This highlights ISG15 as an important component of the host cell defence to the typhoid toxin.

Humans↗
PubMed1996

Virulence properties of Pseudomonas aeruginosa lacking the extreme-stress sigma factor AlgU (sigmaE).

A discerning feature of Pseudomonas aeruginosa strains causing chronic endobronchial infections in cystic fibrosis is their conversion into the mucoid, exopolysaccharide alginate-overproducing phenotype. This morphologically prominent change is caused by mutations which upregulate AlgU (sigma(E)), a novel extreme-stress sigma factor with functional equivalents in gram-negative organisms. In this work, we investigated the role of algU in P. aeruginosa sensitivity to reactive oxygen intermediates, killing by phagocytic cells, and systemic virulence of this bacterium. Inactivation of algU in P. aeruginosa PA01 increased its susceptibility to killing by chemically or enzymatically generated halogenated reactive oxygen intermediates and reduced its survival in bactericidal assays with J774 murine macrophages and human neutrophils. Surprisingly, inactivation of algU caused increased systemic virulence of P. aeruginosa in mouse models of acute infection. The increased lethality of the algU-deficient strain was also observed in the endotoxin-resistant C3H/HeJ mice. Only minor differences between algU+ and algU mutant cells in their sensitivity to human serum were observed, and no differences in their lipopolysaccharide profiles were detected. Intriguingly, while inactivation of algU downregulated five polypeptides it also upregulated the expression of seven polypeptides as determined by two-dimensional gel analyses, suggesting that algU plays both a positive and a negative role in gene expression in P. aeruginosa. While the observation that algU inactivation increases systemic virulence in P. aeruginosa requires further explanation, this phenomenon contrasts with the apparent selection for strains with upregulated AlgU during colonization of the cystic fibrosis lung and suggests opposing roles for this system in chronic and acute infections.

Animals↗
PubMedDate not supplied

SARS virus: the beginning of the unraveling of a new coronavirus.

Severe acute respiratory syndrome (SARS) virus caused a severe outbreak in several regions of the world in 2003. The virus is a novel coronavirus, which may have an origin in wild animals such as civet cats in southern China. Its genome structure, gene expression pattern and protein profiles are similar to those of other coronaviruses. However, distinct patterns of several open reading frames in the SARS virus genome may contribute to its severe virulence. The potential mutability of the coronavirus genome may pose problems in the control of future SARS outbreaks. The mechanism of SARS pathogenesis may involve both direct viral cytocidal effects on the target cells and immune-mediated mechanisms. The life cycle of the SARS virus is largely unknown; however, based on the analogy with other coronaviruses, several potential targets for antiviral development are identified. Vaccines offer an important preventive measure for possible future recurrences of SARS, but the prospect for their development is still unknown because of the uncertainty regarding the role of immune responses in SARS virus pathogenesis. The comparative studies of other coronaviruses offer insights into the understanding of SARS virus.

Chromosome Mapping↗
PubMed2005

Gene expression profiling and characterization under hemin limitation in Porphyromonas gingivalis.

Hemin is an important nutrient for Porphyromonas gingivalis growth and pathogenicity. We examined the gene expression profile of P. gingivalis, including genes involved in its pathogenicity, at various growth stages under hemin-standard and limited conditions by using a custom-made microarray. The transcription of many genes decreased after late-log and mid-log phases under hemin-standard and limited conditions, respectively. We focused on two groups of genes while comparing gene expression profiles under hemin-standard and limited conditions by gene tree analysis. Genes belonging to group A maintained high transcriptional levels, whereas genes in group B were expressed at low levels under standard hemin conditions. However, group B genes increased remarkably under hemin-limited conditions. Groups A and B contained genes involved in regulatory functions and protein fate, respectively. Genes related to energy metabolism, transport, and protein binding were present in both groups. Our results suggest that P. gingivalis experienced severe stress under hemin-limited conditions, and growth phase-dependent changes in transcription levels were observed for many genes. Moreover, increased expression of genes involved in energy metabolism suggests that hemin is related not only to pathogenicity, but also energy metabolism.

Bacterial Proteins↗
PubMedDate not supplied

[Experimental evaluation of interaction between Yersinia pestis and soil infusoria and possibility of prolonged preservation of bacteria in the protozoan oocysts].

The character and outcome of interactions between Y. pestis (vaccine strain and soil infusoria Tetrahymena pyriformis (axenic culture) were under experimental study. The parallel use of the bacteriological method and PCR test systems made it possible to follow the dynamics of Y. pestis cells (strain EV) with different plasmid profiles in their interaction with infusoria, as well as their passage into the protozoa cysts. The study revealed the complete utilization of Y. pestis cells lacking virulence factors by infusoria. The presence of plasmids of virulence influenced only the duration of complete bacterial phagocytosis. A drop in the temperature of cultivation to 2 degrees C induced the mass and rapid encystment of infusoria. In the PCR analysis specific DNA fragments of Y. pestis cells, preserved in the latent (uncultivable) state, were detected in the cysts of protozoa within the period of up to 14 months, while the results of bacteriological studies were negative. The data thus obtained are discussed with regard to the possible mechanisms of the existence and prolonged reservation of Y. pestis in the soils of natural foci with participation of protozoa.

Animals↗
PubMed1983

Cloning and biosynthetic studies of rat somatostatin.

The predicted amino acid sequence of rat preprosomatostatin has been obtained by cloning and subsequent DNA sequence analysis of a cDNA obtained from mRNA prepared from a rat medullary thyroid carcinoma (MTC). The predicted preprosomatostatin is 116 amino acid residues in length. Somatostatin-14 is located at the C-terminus of the preprohormone and the amino terminus contains a 'signal' peptide of 24 amino acids. A somatostatin amino terminal protein of 78 residues is found between the signal peptide and somatostatin-14. Both somatostatin-14 and somatostatin-28 are observed in the thyroid tumour C-cells. A comparison of the rat and human preprosomatostatin amino acid sequences shows only 4 substitutions observed in 116 amino acids. Patients with localized MTC often exhibit high serum calcitonin levels while patients showing cellular heterogeneity in the MTC appear to have lower calcitonin levels and a virulent neoplasia with a grave prognosis. Numerous rat MTCs have been examined by two dimensional gel electrophoresis. It is possible to distinguish characteristic differences in protein profiles of tumours producing high levels of calcitonin from those showing low calcitonin and high somatostatin levels. This analysis can be done with less than 1 mg of tissue and may represent a valuable prognostic tool in evaluating the clinical variability of MTC.

Amino Acid Sequence↗
PubMed2005

Overview and perspectives the transcriptome of Paracoccidioides brasiliensis.

Paracoccidioides brasiliensis is a dimorphic and thermo-regulated fungus which is the causative agent of paracoccidioidomycosis, an endemic disease widespread in Latin America that affects 10 million individuals. Pathogenicity is assumed to be a consequence of the dimorphic transition from mycelium to yeast cells during human infection. This review shows the results of the P. brasiliensis transcriptome project which generated 6,022 assembled groups from mycelium and yeast phases. Computer analysis using the tools of bioinformatics revealed several aspects from the transcriptome of this pathogen such as: general and differential metabolism in mycelium and yeast cells; cell cycle, DNA replication, repair and recombination; RNA biogenesis apparatus; translation and protein fate machineries; cell wall; hydrolytic enzymes; proteases; GPI-anchored proteins; molecular chaperones; insights into drug resistance and transporters; oxidative stress response and virulence. The present analysis has provided a more comprehensive view of some specific features considered relevant for the understanding of basic and applied knowledge of P. brasiliensis.

Cell Wall↗