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Berlin Brandenburg

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  • 1
    Language: English
    In: The Journal of infectious diseases, November 2012, Vol.206(9), pp.1407-14
    Description: Haemophilus ducreyi encounters several classes of antimicrobial peptides (APs) in vivo and utilizes the sensitive-to-antimicrobial-peptides (Sap) transporter as one mechanism of AP resistance. A mutant lacking the periplasmic solute-binding component, SapA, was somewhat more sensitive to the cathelicidin LL-37 than the parent strain and was partially attenuated for virulence. The partial attenuation led us to question whether the transporter is fully abrogated in the sapA mutant. We generated a nonpolar sapBC mutant, which lacks both inner membrane permeases of the Sap transporter, and tested the mutant for virulence in human volunteers. In vitro, we compared LL-37 resistance phenotypes of the sapBC and sapA mutants. Unlike the sapA mutant, the sapBC mutant was fully attenuated for virulence in human volunteers. In vitro, the sapBC mutant exhibited significantly greater sensitivity than the sapA mutant to killing by LL-37. Similar to the sapA mutant, the sapBC mutant did not affect H. ducreyi's resistance to human defensins. Compared with the sapA mutant, the sapBC mutant exhibited greater attenuation in vivo, which directly correlated with increased sensitivity to LL-37 in vitro. These results strongly suggest that the SapBC channel retains activity when SapA is removed.
    Keywords: Drug Resistance, Bacterial ; Antimicrobial Cationic Peptides -- Pharmacology ; Haemophilus Ducreyi -- Enzymology ; Membrane Transport Proteins -- Metabolism ; Virulence Factors -- Metabolism
    ISSN: 00221899
    E-ISSN: 1537-6613
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  • 2
    In: The Journal of Infectious Diseases, 2016, Vol. 214(3), pp.489-495
    Description: Background.  In humans inoculated with Haemophilus ducreyi , there are host effects on the possible clinical outcomes—pustule formation versus spontaneous resolution of infection. However, the immunogenetic factors that influence these outcomes are unknown. Here we examined the role of 14 single-nucleotide polymorphisms (SNPs) in 7 selected pathogen-recognition pathways and cytokine genes on the gradated outcomes of experimental infection. Methods.  DNAs from 105 volunteers infected with H. ducreyi at 3 sites were genotyped for SNPs, using real-time polymerase chain reaction. The participants were classified into 2 cohorts, by race, and into 4 groups, based on whether they formed 0, 1, 2, or 3 pustules. χ 2 tests for trend and logistic regression analyses were performed on the data. Results.  In European Americans, the most significant findings were a protective association of the TLR9 +2848 GG genotype and a risk-enhancing association of the TLR9 TA haplotype with pustule formation; logistic regression showed a trend toward protection for the TLR9 +2848 GG genotype. In African Americans, logistic regression showed a protective effect for the IL10 – 2849 AA genotype and a risk-enhancing effect for the IL10 AAC haplotype. Conclusions.  Variations in TLR9 and IL10 are associated with the outcome of H. ducreyi infection.
    Keywords: 〈Kwd〉〈Italic Toggle="Yes"〉Haemophilus Ducreyi〈/Italic〉〈/Kwd〉 ; Chancroid ; Skin Ulcers ; Immunogenetics ; Humans ; Innate Immunity
    ISSN: 0022-1899
    E-ISSN: 1537-6613
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  • 3
    Language: English
    In: Infection and immunity, December 2012, Vol.80(12), pp.4426-34
    Description: During microbial infection, macrophages are polarized to classically activated (M1) or alternatively activated (M2) cells in response to microbial components and host immune mediators. Proper polarization of macrophages is critical for bacterial clearance. To study the role of macrophage polarization during Haemophilus ducreyi infection, we analyzed a panel of macrophage surface markers in skin biopsy specimens of pustules obtained from experimentally infected volunteers. Lesional macrophages expressed markers characteristic of both M1 and M2 polarization. Monocyte-derived macrophages (MDM) also expressed a mixed M1 and M2 profile of surface markers and cytokines/chemokines upon infection with H. ducreyi in vitro. Endogenous interleukin 10 (IL-10) produced by infected MDM downregulated and enhanced expression of several M1 and M2 markers, respectively. Bacterial uptake, mediated mainly by class A scavenger receptors, and activation of mitogen-activated protein kinase and phosphoinositide 3-kinase signaling pathways were required for H. ducreyi-induced IL-10 production in MDM. Compared to M1 cells, IL-10-polarized M2 cells displayed enhanced phagocytic activity against H. ducreyi and similar bacterial killing. Thus, IL-10-modulated macrophage polarization may contribute to H. ducreyi clearance during human infection.
    Keywords: Chancroid -- Immunology ; Haemophilus Ducreyi -- Immunology ; Interleukin-10 -- Immunology ; Macrophage Activation -- Immunology ; Macrophages -- Classification
    E-ISSN: 1098-5522
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  • 4
    Language: English
    In: Infection and immunity, August 2011, Vol.79(8), pp.3338-47
    Description: Haemophilus ducreyi causes chancroid, a genital ulcer disease. In human inoculation experiments, most volunteers fail to clear the bacteria despite the infiltration of innate and adaptive immune cells to the infected sites. The immunosuppressive protein indoleamine 2,3-dioxygenase (IDO) is a rate-limiting enzyme in the L-tryptophan-kynurenine metabolic pathway. Tryptophan depletion and tryptophan metabolites contribute to pathogen persistence by inhibiting T cell proliferation, inducing T cell apoptosis, and promoting the expansion of FOXP3(+) regulatory T (Treg) cells. We previously found that FOXP3(+) Treg cells are enriched in experimental lesions and that H. ducreyi induced IDO transcription in dendritic cells (DC) derived from blood of infected volunteers who developed pustules. Here, we showed that enzymatically active IDO was induced in DC by H. ducreyi. Neutralizing antibodies against interferon alpha/beta receptor 2 chain (IFNAR2) and tumor necrosis factor alpha (TNF-α) inhibited IDO induction. Inhibitors of the mitogen-activated protein kinase (MAPK) p38 and nuclear factor-κB (NF-κB) also inhibited IDO expression. Neither bacterial contact with nor uptake by DC was required for IDO activation. H. ducreyi culture supernatant and H. ducreyi lipooligosaccharides (LOS) induced IDO expression, which required type I interferons, TNF-α, and the three MAPK (p38, c-Jun N-terminal kinase, and extracellular signal regulated kinase) and NF-κB pathways. In addition, LOS-induced IFN-β activated the JAK-STAT pathway. Blocking the LOS/Toll-like receptor 4 (TLR4) signaling pathway greatly reduced H. ducreyi-induced IDO production. These findings indicate that H. ducreyi-induced IDO expression in DC is largely mediated by LOS via type I interferon- and TNF-α-dependent mechanisms and the MAPK, NF-κB, and JAK-STAT pathways.
    Keywords: Immune Tolerance ; Dendritic Cells -- Immunology ; Haemophilus Ducreyi -- Immunology ; Indoleamine-Pyrrole 2,3,-Dioxygenase -- Biosynthesis ; Interferon Type I -- Metabolism ; Lipopolysaccharides -- Immunology ; Tumor Necrosis Factor-Alpha -- Metabolism
    ISSN: 00199567
    E-ISSN: 1098-5522
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  • 5
    Language: English
    In: The Journal of infectious diseases, 15 June 2010, Vol.201(12), pp.1839-48
    Description: Haemophilus ducreyi causes chancroid, a genital ulcer disease. Among human volunteers, the majority of experimentally infected individuals fail to clear the infection and form pustules. Here, we investigated the role played by CD4(+)FOXP3(+) regulatory T (T(reg)) cells in the formation of pustules. In pustules, there was a significant enrichment of CD4(+)FOXP3(+) T cells, compared with that in peripheral blood. The majority of lesional FOXP3(+) T cells were CD4(+), CD25(+), CD127(lo/-), and CTLA-4(+). FOXP3(+) T cells were found throughout pustules but were most abundant at their base. Significantly fewer lesional CD4(+)FOXP3(+) T cells expressed interferon gamma, compared with lesional CD4(+)FOXP3(-) effector T cells. Depletion of CD4(+)CD25(+) T cells from the peripheral blood of infected and uninfected volunteers significantly enhanced proliferation of H. ducreyi-reactive CD4(+) T cells. Our results indicate that the population of CD4(+)CD25(+)CD127(lo/-)FOXP3(+) T(reg) cells are expanded at H. ducreyi-infected sites and that these cells may play a role in suppressing the host immune response to the bacterium.
    Keywords: Immune Tolerance ; Cd4-Positive T-Lymphocytes -- Immunology ; Forkhead Transcription Factors -- Analysis ; Haemophilus Infections -- Immunology ; Haemophilus Ducreyi -- Immunology ; T-Lymphocytes, Regulatory -- Immunology
    ISSN: 00221899
    E-ISSN: 1537-6613
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  • 6
    Language: English
    In: Infection and immunity, February 2013, Vol.81(2), pp.608-17
    Description: The carbon storage regulator A (CsrA) controls a wide variety of bacterial processes, including metabolism, adherence, stress responses, and virulence. Haemophilus ducreyi, the causative agent of chancroid, harbors a homolog of csrA. Here, we generated an unmarked, in-frame deletion mutant of csrA to assess its contribution to H. ducreyi pathogenesis. In human inoculation experiments, the csrA mutant was partially attenuated for pustule formation compared to its parent. Deletion of csrA resulted in decreased adherence of H. ducreyi to human foreskin fibroblasts (HFF); Flp1 and Flp2, the determinants of H. ducreyi adherence to HFF cells, were downregulated in the csrA mutant. Compared to its parent, the csrA mutant had a significantly reduced ability to tolerate oxidative stress and heat shock. The enhanced sensitivity of the mutant to oxidative stress was more pronounced in bacteria grown to stationary phase compared to that in bacteria grown to mid-log phase. The csrA mutant also had a significant survival defect within human macrophages when the bacteria were grown to stationary phase but not to mid-log phase. Complementation in trans partially or fully restored the mutant phenotypes. These data suggest that CsrA contributes to virulence by multiple mechanisms and that these contributions may be more profound in bacterial cell populations that are not rapidly dividing in the human host.
    Keywords: Bacterial Proteins -- Metabolism ; Carbon -- Metabolism ; Chancroid -- Metabolism ; Haemophilus Ducreyi -- Metabolism
    ISSN: 00199567
    E-ISSN: 1098-5522
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  • 7
    Language: English
    In: Infection and Immunity, 2012, Vol. 80(2), p.679
    Description: Sialylated glycoconjugates on the surfaces of mammalian cells play important roles in intercellular communication and self-recognition. The sialic acid preferentially expressed in human tissues is N-acetylneuraminic acid (Neu5Ac). In a process called molecular mimicry, many bacterial pathogens decorate their cell surface glycolipids with Neu5Ac. Incorporation of Neu5Ac into bacterial glycolipids promotes bacterial interactions with host cell receptors called Siglecs. These interactions affect bacterial adherence, resistance to serum killing and phagocytosis, and innate immune responses. Haemophilus ducreyi, the etiologic agent of chancroid, expresses lipooligosaccharides (LOS) that are highly sialylated. However, an H. ducreyi sialyltransferase (lst) mutant, whose LOS contain reduced levels of Neu5Ac, is fully virulent in human volunteers. Recently, a second sialyltransferase gene (Hd0053) was discovered in H. ducreyi, raising the possibility that Hd0053 compensated for the loss of lst during human infection. CMP-Neu5Ac is the obligate nucleotide sugar donor for all bacterial sialyltransferases; LOS derived from an H. ducreyi CMP-Neu5Ac synthetase (neuA) mutant has no detectable Neu5Ac. Here, we compared an H. ducreyi neuA mutant to its wild-type parent in several models of pathogenesis. In human inoculation experiments, the neuA mutant formed papules and pustules at rates that were no different than those of its parent. When grown in media with and without Neu5Ac supplementation, the neuA mutant and its parent had similar phenotypes in bactericidal, macrophage uptake, and dendritic cell activation assays. Although we cannot preclude a contribution of LOS sialylation to ulcerative disease, these data strongly suggest that sialylation of LOS is dispensable for H. ducreyi pathogenesis in humans.
    Keywords: Bacterial Proteins -- Metabolism ; Chancroid -- Microbiology ; Haemophilus Ducreyi -- Metabolism ; Lipopolysaccharides -- Metabolism ; N-Acetylneuraminic Acid -- Metabolism;
    ISSN: 1098-5522
    ISSN: 10985522
    ISSN: 00199567
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  • 8
    Language: English
    In: PLoS ONE, Vol.10(4), p.e0124373
    Description: Haemophilus ducreyi resists the cytotoxic effects of human antimicrobial peptides (APs), including α-defensins, β-defensins, and the cathelicidin LL-37. Resistance to LL-37, mediated by the sensitive to antimicrobial peptide (Sap) transporter, is required for H. ducreyi virulence in humans. Cationic APs are attracted to the negatively charged bacterial cell surface. In other gram-negative bacteria, modification of lipopolysaccharide or lipooligosaccharide (LOS) by the addition of positively charged moieties, such as phosphoethanolamine (PEA), confers AP resistance by means of electrostatic repulsion. H. ducreyi LOS has PEA modifications at two sites, and we identified three genes (lptA, ptdA, and ptdB) in H. ducreyi with homology to a family of bacterial PEA transferases. We generated non-polar, unmarked mutants with deletions in one, two, or all three putative PEA transferase genes. The triple mutant was significantly more susceptible to both α- and β-defensins; complementation of all three genes restored parental levels of AP resistance. Deletion of all three PEA transferase genes also resulted in a significant increase in the negativity of the mutant cell surface. Mass spectrometric analysis revealed that LptA was required for PEA modification of lipid A; PtdA and PtdB did not affect PEA modification of LOS. In human inoculation experiments, the triple mutant was as virulent as its parent strain. While this is the first identified mechanism of resistance to α-defensins in H. ducreyi, our in vivo data suggest that resistance to cathelicidin LL-37 may be more important than defensin resistance to H. ducreyi pathogenesis.
    Keywords: Sciences (General)
    E-ISSN: 1932-6203
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  • 9
    Language: English
    In: Infection and immunity, September 2010, Vol.78(9), pp.3898-904
    Description: Haemophilus ducreyi must adapt to the environment of the human host to establish and maintain infection in the skin. Bacteria generally utilize stress response systems, such as the CpxRA two-component system, to adapt to hostile environments. CpxRA is the only obvious two-component system contained in the H. ducreyi genome and negatively regulates the lspB-lspA2 operon, which encodes proteins that enable the organism to resist phagocytosis. We constructed an unmarked, in-frame H. ducreyi cpxA deletion mutant, 35000HPDeltacpxA. In human inoculation experiments, 35000HPDeltacpxA formed papules at a rate and size that were significantly less than its parent and was unable to form pustules compared to the parent. CpxA usually has kinase and phosphatase activities for CpxR, and the deletion of CpxA leads to the accumulation of activated CpxR due to the loss of phosphatase activity and the ability of CpxR to accept phosphate groups from other donors. Using a reporter construct, the lspB-lspA2 promoter was downregulated in 35000HPDeltacpxA, confirming that CpxR was activated. Deletion of cpxA downregulated DsrA, the major determinant of serum resistance in the organism, causing the mutant to become serum susceptible. Complementation in trans restored parental phenotypes. 35000HPDeltacpxA is the first H. ducreyi mutant that is impaired in its ability to form both papules and pustules in humans. Since a major function of CpxRA is to control the flow of protein traffic across the periplasm, uncontrolled activation of this system likely causes dysregulated expression of multiple virulence determinants and cripples the ability of the organism to adapt to the host.
    Keywords: Bacterial Proteins -- Physiology ; Haemophilus Ducreyi -- Pathogenicity ; Protein Kinases -- Physiology
    ISSN: 00199567
    E-ISSN: 1098-5522
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  • 10
    In: Infection and Immunity, 2010, Vol. 78(3), p.1176
    Description: Haemophilus ducreyi is an extracellular pathogen of human epithelial surfaces that resists human antimicrobial peptides (APs). The organism's genome contains homologs of genes sensitive to antimicrobial peptides (sap operon) in nontypeable Haemophilus influenzae. In this study, we characterized the sap-containing loci of H. ducreyi 35000HP and demonstrated that sapA is expressed in broth cultures and H. ducreyi-infected tissue; sapA is also conserved among both class I and class II H. ducreyi strains. We constructed a nonpolar sapA mutant of H. ducreyi 35000HP, designated 35000HPsapA, and compared the percent survival of wild-type 35000HP and 35000HPsapA exposed to several human APs, including alpha-defensins, beta-defensins, and the cathelicidin LL-37. Unlike an H. influenzae sapA mutant, strain 35000HPsapA was not more susceptible to defensins than strain 35000HP was. However, we observed a significant decrease in the survival of strain 35000HPsapA after exposure to LL-37, which was complemented by introducing sapA in trans. Thus, the Sap transporter plays a role in resistance of H. ducreyi to LL-37. We next compared mutant strain 35000HPsapA with strain 35000HP for their ability to cause disease in human volunteers. Although both strains caused papules to form at similar rates, the pustule formation rate at sites inoculated with 35000HPsapA was significantly lower than that of sites inoculated with 35000HP (33.3% versus 66.7%; P = 0.007). Together, these data establish that SapA acts as a virulence factor and as one mechanism for H. ducreyi to resist killing by antimicrobial peptides. To our knowledge, this is the first demonstration that an antimicrobial peptide resistance mechanism contributes to bacterial virulence in humans.
    Keywords: Medicine ; Biology;
    ISSN: 0019-9567
    ISSN: 00199567
    E-ISSN: 10985522
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