• Parasites, Hosts and Diseases
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• v.60 no.5
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• pp.317-325
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• 2022

Hypoxia-inducible factor-1 alpha (HIF-1α) is one of the master regulators of immune and metabolic cellular functions. HIF-1α, a transcriptional factor whose activity is closely related to oxygen levels, is a target for understanding infectious disease control. Several studies have demonstrated that HIF-1α plays an important role during the infectious process, while its role in relation to parasite virulence has not been addressed. In this work, we studied the expression levels of HIF-1α and related angiogenic vascular endothelial growth factor A (VEGF-A) in human macrophages infected with promastigotes of hypo- or hyper-virulent Leishmania major human isolates. L. major parasites readily subverted host macrophage functions for their survival and induced local oxygen consumption at the site of infection. In contrast to hypo-virulent parasites that induce high HIF-1α expression levels, hyper-virulent L. major reduced HIF-1α expression in macrophages under normoxic or hypoxic conditions, and consequently impeded the expression of VEGF-A mRNA. HIF-1α may play a key role during control of disease chronicity, severity, or outcome.

• Microbiology and Biotechnology Letters
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• v.44 no.2
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• pp.218-226
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• 2016

Helicobacter pylori primarily colonizes the human stomach. Infection by this bacterium is associated with various gastric diseases, including inflammation, peptic ulcer, and gastric cancer. Although there are antibiotic regimens for the eradication of H. pylori, the resistance of this species against antibiotics has been continuously increasing. The natural compound plumbagin has been reported as an antimicrobial and anticancer molecule. In this study, we analyzed the inhibitory effect of plumbagin on H. pylori strain ATCC 49503 as well as the expression of various molecules associated with H. pylori growth or virulence by immunoblotting and reverse transcription polymerase chain reaction (RT-PCR) analyses. We demonstrated the minimal inhibitory concentration of plumbagin on H. pylori through the agar dilution and broth dilution methods. Furthermore, we investigated the effect of plumbagin treatment on the expression of the RNA polymerase subunits and various virulence factors of H. pylori. Plumbagin treatment decreased the expression of RNA polymerase subunit alpha (rpoA), which is closely associated with bacterial survival. Moreover, the mRNA and protein levels of the major CagA and VacA toxins were decreased in plumbagintreated H. pylori cells. Likewise, the expression levels of urease subunit alpha (ureA) and an adhesin (alpA) were decreased by plumbagin treatment. Collectively, these results suggest that plumbagin may inhibit the growth, colonization, and pathogenesis of H. pylori by the mechanism demonstrated in this study.

• Molecules and Cells
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• v.20 no.3
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• pp.409-415
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• 2005

Infection of Drosophila melanogaster adults with 6 Vibrio species revealed that V. cholerae was lethal (100% mortality) within 20 h as a result of systemic infection. Avirulent infection by V. vulnificus restricted the subsequent virulent infection by V. cholerae. The immediate transcription of antimicrobial peptides (AMPs), most notably Attacin A, was delayed in V. cholerae infection compared to V. vulnificus infection. Ectopic expression of Attacin A and Metchnikowin enhanced the survival of D. melanogaster upon V. cholerae infection. These results suggest that AMPs are important in the response to infections by Vibrio species and that the signaling pathways governing their expression may be targeted by V. cholerae virulence factors to elude the innate immunity of Drosophila.

• Journal of Plant Biotechnology
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• v.31 no.3
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• pp.185-190
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• 2004

We established a transient gene expression system in chili pepper leaves based on Agrobacterium-mediated transformation of GUS gene. For the best GUS transient expression, two step culture system was adopted. When the Agrobacterium tumefaciens cell density of pre-culture was $A_{600nm}$ 0.3, the cells were harvested and diluted to $A_{600nm}$ 0.8 with virulence induction medium after cell harvested. The addition of acetosyringone (200 $\mu$M) in virulence induction step was a key factor for successful transient expression. Additionally, Younger leaves showed more effective transient expression than older leaves. Temporally, the strongest intensity of GUS expression was detected at 2 days after infiltration. These results demonstrate that Agrobacterium-mediated transient expression can be used for a simple in vivo assays of plant promoters, transcription factors and furthermore provide efficient protocol for chili pepper transformation.

• Journal of Microbiology and Biotechnology
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• v.13 no.6
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• pp.1021-1026
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• 2003

Numerous secreted and cell-associated virulence factors have been proposed to account for the fulminating and destructive nature of Vibrio vulnificus infections. Among the putative virulence factors are an elastase, elastolytic protease, and a cytolytic hemolysin. Effects of the elastase on the hemolysin were assessed by evaluating changes of hemolytic activities either in the presence or absence of the protease. Although hemolytic activity in the culture supernatant was lowered by the purified elastase added in vitro, the cellular level of hemolytic activity was unaffected by the mutation of vvpE encoding the elastase. Growth kinetic studies revealed that hemolysin reached its maximum level in the exponential phase of growth, and the elastase appeared at the onset of the stationary phase. These results have provided insight into the regulation of virulence factors: temporally coordinate regulation of virulence factors is essential for the overall success of the pathogen during pathogenesis.

• Biomedical Science Letters
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• v.21 no.4
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• pp.233-240
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• 2015

Some virulence proteins of Helicobacter pylori, such as vacuolating cytotoxic protein A (VacA) and cytotoxin-associated gene protein A (CagA) have been reported to be causative agents of various gastric diseases including chronic gastritis, gastric ulcer or gastric adenocarcinoma. The expression level of these virulence proteins can be regulated when H. pylori is exposed to the antibacterial agent, cyanidin 3-O-glucoside (C3G) as previously reported. In this study, we analyzed the quantitative change of various virulence proteins including CagA and VacA by C3G treatment. We used 2-dimensional electrophoresis (2-DE) to analyze the quantitative change of representative ten proteome components of H. pylori 60190 ($VacA^+/CagA^+$; standard strain of Eastern type). After 2-DE analysis, spot intensities were analyzed using ImageMaster$^{TM}$ 2-DE Platinum software then each spot was identified using matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) or peptide sequencing using Finnigan LCQ ion trap mass spectrometer (LC-MS/MS). Next, we selected major virulence proteins of H. pylori among quantitatively meaningful ten spots and confirmed the 2-DE results by Western blot analysis. These results suggest that cyanidin 3-O-glucoside can modulate a variety of H. pylori pathogenic determinants.

• Journal of Microbiology and Biotechnology
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• v.18 no.7
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• pp.1227-1234
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• 2008

Pseudomonas aeruginosa is an opportunistic human pathogen that produces and secretes exopolysaccharides (EPS), in which cells are embedded to form a highly organized community structure called biofilm. Here, we characterized the role of cyclic diguanylate (c-di-GMP) and EPS (PEL) overproduction in the wspF mutant phenotypes of P. aeruginosa PA14 (wrinkly appearance, hyperadherence, impaired motilities, and reduced virulence in acute infections). We confirmed that the elevated c-di-GMP level plays a key role in all the wspF mutant phenotypes listed above, as assessed by ectopic expression of a c-di-GMP-degrading phophodiesterase (PvrR) in the wspF mutant. In contrast, PEL EPS, which is overproduced in the wspF mutant, was necessary for wrinkly appearance and hyperadherence, but not for the impaired flagellar motilities and the attenuated virulence of the wspF mutant. These results suggest that c-di-GMP affects flagellar motility and virulence, independently of EPS production and surface adherence of this bacterium.

• Korean Journal of Veterinary Research
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• v.55 no.3
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• pp.191-197
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• 2015

Escherichia (E.) coli is commensal bacteria found in the intestine; however, some pathogenic strains cause diseases in animals and humans. Although E. coli does not typically produce hydrogen sulfide ($H_2S$), $H_2S$-producing strains of E. coli have been identified worldwide. The relationship between virulence and $H_2S$ production has not yet been determined. Therefore, characteristics of $H_2S$-producing isolates obtained from swine feces were evaluated including antibiotic resistance patterns, virulence gene expression, and genetic relatedness. Rates of antibiotic resistance of the $H_2S$-producing E. coli varied according to antibiotic. Only the EAST1 gene was detected as a virulence gene in five $H_2S$-producing E. coli strains. Genes conferring $H_2S$ production were not transmissible although the sseA gene encoding 3-mercaptopyruvate sulfurtransferase was detected in all $H_2S$-producing E. coli strains. Sequences of the sseA gene motif CGSVTA around Cys238 were also identical in all $H_2S$- producing E. coli strains. Diverse genetic relatedness among the isolates was observed by pulsed-field gel electrophoresis analysis. These results suggested that $H_2S$-producing E. coli strains were not derived from a specific clone and $H_2S$ production in E. coli is not associated with virulence genes.

• Korean Journal of Veterinary Research
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• v.51 no.1
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• pp.15-20
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• 2011

In this study, we isolated 12 of Brucella (B.) spp. from cattle, which have been positive in Rose Bangal test and tube agglutination test in Gyeongbuk province in 2009. According to AMOS PCR analysis, isolated 12 strains were identified as B. abortus. Murine derived macrophage, RAW 264.7 cells, were infected with isolated 12 strains or reference strain (B. abortus 544), and bacterial internalization were characterized. According to these results, we divided the isolated strains into the following three groups: class I, lower internalization than that of B. abortus 544; class II, similar internalization to that of that of B. abortus 544; class III, higher internalization than that of B. abortus 544 within RAW 264.7 cells. Furthermore, intracellular growth, bacterial adherent assay, LAMP-1 colocalization, virulence in mice and surface protein pattern were characterized. From these results, representative strains of class III showed lower LAMP-1 colocalization, higher adherent efficiency, higher virulence in mice than those of B. abortus 544, and showed different pattern of surface proteins. These results suggest that B. abortus field strains, isolated from cattle in Korea, possess various virulence properties and higher internalization ability of field strain may have an important role for its virulence expression.

• Korean Journal of Microbiology
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• v.26 no.3
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• pp.262-269
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• 1988

In order to investigate the virulence of Y. enterocolitica isolated in Korea, all necessary experiments were done including several virulence determinating tests-autoagglutination test, calcium-dependency test, HeLa cell invasion test, Sereny test, crystal violet binding test, and electrophoresis for plasmid pattern. The obtained results are as follows: The virulent strains of Y. enterocolitica revealed positive reactions on autoagglutination test, cacium-dependency test, and drystal violet binding test, while the avirulent strains did not. A positive reaction was observed only at $37^{\circ}C$ implying that the expression of virulence is temperature-dependent. In Sereny test, the standard reference virulent strain (serotype 0:8) showed positive reactions while the virylent experimental strains (serotype 1:3, 0:9) revealed negative results, which indicates that the virulence of Y. enterocolitica in experimental animals varied according to their serotypes. Most of the virulent strains contained 36-38Mdal plasmids, but the avirulent strains did not. In addition, it was noted that autoagglutination, calcium-dependency, and crystal violet binding were related to the presence of plasmids.