Kooperativer Bibliotheksverbund

Berlin Brandenburg

and
and

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    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
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    In: Infection and Immunity, 2008, Vol. 76(4), p.1608
    Description: The ability to bind extracellular matrix proteins is a critical virulence determinant for skin pathogens. Haemophilus ducreyi, the etiological agent of the genital ulcer disease chancroid, binds extracellular matrix components, including fibronectin (FN). We investigated H. ducreyi FN binding and report several important findings about this interaction. First, FN binding by H. ducreyi was greatly increased in bacteria grown on heme and almost completely inhibited by hemoglobin. Second, wild-type strain 35000HP bound significantly more FN than did a dsrA mutant in two different FN binding assays. Third, the expression of dsrA in the dsrA mutant restored FN binding and conferred the ability to bind FN to a non-FN-binding Haemophilus influenzae strain. Fourth, an anti-DsrA monoclonal antibody partially blocked FN binding by H. ducreyi. The hemoglobin receptor, the collagen-binding protein, the H. ducreyi lectin, the fine-tangle pili, and the outer membrane protein OmpA2 were not involved in H. ducreyi FN binding, since single mutants bound FN as well as the parent strain did. However, the major outer membrane protein may have a minor role in FN binding by H. ducreyi, since a double dsrA momp mutant bound less FN than did the single dsrA mutant. Finally, despite major sequence differences, DsrA proteins from both class I and class II H. ducreyi strains mediated FN and vitronectin binding. We concluded that DsrA is the major factor involved in FN binding by both classes of H. ducreyi strains.
    Keywords: Medicine ; Biology;
    ISSN: 0019-9567
    ISSN: 00199567
    E-ISSN: 10985522
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    In: Infection and Immunity, 2007, Vol. 75(12), p.5678
    Description: Dendritic cells (DC) orchestrate innate and adaptive immune responses to bacteria. How Haemophilus ducreyi, which causes genital ulcers and regional lymphadenitis, interacts with DC is unknown. H. ducreyi evades uptake by polymorphonuclear leukocyte and macrophage-like cell lines by secreting LspA1 and LspA2. Many H. ducreyi strains express cytolethal distending toxin (CDT), and recombinant CDT causes apoptosis of DC in vitro. Here, we examined interactions between DC and H. ducreyi 35000HP, which produces LspA1, LspA2, and CDT. In human volunteers infected with 35000HP, the ratio of myeloid DC to plasmacytoid DC was 2.8:1 in lesions, compared to a ratio of 1:1 in peripheral blood. Using myeloid DC derived from monocytes as surrogates for lesional DC, we found that DC infected with 35000HP remained as viable as uninfected DC for up to 48 h. Gentamicin protection and confocal microscopy assays demonstrated that DC ingested and killed 35000HP, but killing was incomplete at 48 h. The expression of LspA1 and LspA2 did not inhibit the uptake of H. ducreyi, despite inactivating Src kinases. Infection of DC with live 35000HP caused less cell surface marker activation than infection with heat-killed 35000HP and lipopolysaccharide (LPS) and inhibited maturation by LPS. However, infection of DC with live bacteria caused the secretion of significantly higher levels of interleukin-6 and tumor necrosis factor alpha than infection with heat-killed bacteria and LPS. The survival of H. ducreyi in DC may provide a mechanism by which the organism traffics to lymph nodes. Partial activation of DC may abrogate the establishment of a full Th1 response and an environment that promotes phagocytosis.
    Keywords: Chancroid -- Immunology ; Dendritic Cells -- Immunology ; Haemophilus Ducreyi -- Immunology ; Myeloid Cells -- Immunology;
    ISSN: 0019-9567
    ISSN: 00199567
    E-ISSN: 10985522
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    In: Infection and Immunity, 2007, Vol. 75(12), p.5686
    Description: In experimentally infected human volunteers, the cutaneous immune response to Haemophilus ducreyi is orchestrated by serum, polymorphonuclear leukocytes, macrophages, T cells, and myeloid dendritic cells (DC). This response either leads to spontaneous resolution of infection or progresses to pustule formation, which is associated with the failure of phagocytes to ingest the organism and the presence of Th1 and regulatory T cells. In volunteers who are challenged twice, some subjects form at least one pustule twice (PP group), while others have all inoculated sites resolve twice (RR group). Here, we infected PP and RR subjects with H. ducreyi and used microarrays to profile gene expression in infected and wounded skin. The PP and RR groups shared a core response to H. ducreyi. Additional transcripts that signified effective immune function were differentially expressed in RR infected sites, while those that signified a hyperinflammatory, dysregulated response were differentially expressed in PP infected sites. To examine whether DC drove these responses, we profiled gene expression in H. ducreyi-infected and uninfected monocyte-derived DC. Both groups had a common response that was typical of a type 1 DC (DC1) response. RR DC exclusively expressed many additional transcripts indicative of DC1. PP DC exclusively expressed differentially regulated transcripts characteristic of DC1 and regulatory DC. The data suggest that DC from the PP and RR groups respond differentially to H. ducreyi. PP DC may promote a dysregulated T-cell response that contributes to phagocytic failure, while RR DC may promote a Th1 response that facilitates bacterial clearance.
    Keywords: Medicine ; Biology;
    ISSN: 0019-9567
    ISSN: 00199567
    E-ISSN: 10985522
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Language: English
    In: Infection and immunity IAI, 2006, Vol.74(5), pp.2651-2658
    Description: Haemophilus ducreyi, the etiologic agent of the sexually transmitted genital ulcer disease chancroid, has been shown to associate with dermal collagen fibers within infected skin lesions. Here we describe NcaA, a previously uncharacterized outer membrane protein that is important for H. ducreyi collagen binding and host colonization. An H. ducreyi strain lacking the ncaA gene was impaired in adherence to type I collagen but not fibronectin (plasma or cellular form) or heparin. The mutation had no effect on serum resistance or binding to HaCaT keratinocytes or human foreskin fibroblasts in vitro. Escherichia coli expressing H. ducreyi NcaA bound to type I collagen, demonstrating that NcaA is sufficient to confer collagen attachment. The importance of NcaA in H. ducreyi pathogenesis was assessed using both swine and human experimental models of chancroid. In the swine model, 20% of lesions from sites inoculated with the ncaA mutant were culture positive for H. ducreyi 7 days after inoculation, compared to 73% of wild-type-inoculated sites. The average number of CFU recovered from mutant-inoculated lesions was also significantly reduced compared to that recovered from wild-type-inoculated sites at both 2 and 7 days after inoculation. In the human challenge model, 8 of 30 sites inoculated with wild-type H. ducreyi progressed to the pustular stage, compared to 0 of 30 sites inoculated with the ncaA mutant. Together these results demonstrate that the collagen binding protein NcaA is required for H. ducreyi infection. ; Includes references ; p. 2651-2658.
    ISSN: 1098-5522
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. Further information can be found on the KOBV privacy pages