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  • Hemophilus Infections
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  • 1
    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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  • 2
    Language: English
    In: Journal of Bacteriology, 2013, Vol.195(15-16), p.3486(17)
    Description: Haemophilus ducreyi causes chancroid, a genital ulcer disease that facilitates the transmission of human immunodeficiency virus type 1. In humans, H. ducreyi is surrounded by phagocytes and must adapt to a hostile environment to survive. To sense and respond to environmental cues, bacteria frequently use two-component signal transduction (2CST) systems. The only obvious 2CST system in H. ducreyi is CpxRA; CpxR is a response regulator, and CpxA is a sensor kinase. Previous studies by Hansen and coworkers showed that CpxR directly represses the expression of dsrA, the lspB-lspA2 operon, and the flp operon, which are required for virulence in humans. They further showed that CpxA functions predominantly as a phosphatase in vitro to maintain the expression of virulence determinants. Since a cpxA mutant is avirulent while a cpxR mutant is fully virulent in humans, CpxA also likely functions predominantly as a phosphatase in vivo. To better understand the role of H. ducreyi CpxRA in controlling virulence determinants, here we defined genes potentially regulated by CpxRA by using RNA-Seq. Activation of CpxR by deletion of cpxA repressed nearly 70% of its targets, including seven established virulence determinants. Inactivation of CpxR by deletion of cpxR differentially regulated few genes and increased the expression of one virulence determinant. We identified a CpxR binding motif that was enriched in downregulated but not upregulated targets. These data reinforce the hypothesis that CpxA phosphatase activity plays a critical role in controlling H. ducreyi virulence in vivo. Characterization of the downregulated genes may offer new insights into pathogenesis.
    Keywords: Chancroid – Causes of ; Gene Expression – Research ; Hemophilus Infections – Research ; Virulence (Microbiology) – Research
    ISSN: 0021-9193
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: The Journal of infectious diseases, 15 June 2011, Vol.203(12), pp.1859-65
    Description: Haemophilus ducreyi 35000HP contains a homolog of the CpxRA 2-component signal transduction system, which controls the cell envelope stress response system in other gram-negative bacteria and regulates some important H. ducreyi virulence factors. A H. ducreyi cpxR mutant was compared with its parent for virulence in the human challenge model of experimental chancroid. The pustule formation rate in 5 volunteers was 33% (95% confidence interval [CI], 1.3%-65.3%) at 15 parent sites and 40% (95% CI, 18.1%-61.9%) at 15 mutant sites (P = .35). Thus, the cpxR mutant was not attenuated for virulence. Inactivation of the H. ducreyi cpxR gene did not reduce the ability of this mutant to express certain proven virulence factors, including the DsrA serum resistance protein and the LspA2 protein, which inhibits phagocytosis. These results expand our understanding of the involvement of the CpxRA system in regulating virulence expression in H. ducreyi.
    Keywords: Bacterial Proteins -- Genetics ; Chancroid -- Microbiology ; Haemophilus Ducreyi -- Genetics
    ISSN: 00221899
    E-ISSN: 1537-6613
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  • 4
    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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  • 5
    Language: English
    In: Journal of Infectious Diseases, 2016, Vol.214(3), pp.489-495
    Keywords: Haemophilus Ducreyi ; Chancroid ; Skin Ulcers ; Immunogenetics ; Humans ; Innate Immunity
    ISSN: 0022-1899
    ISSN: 1537-6613
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  • 6
    Language: English
    In: Journal of bacteriology, December 2014, Vol.196(23), pp.4012-25
    Description: Haemophilus ducreyi causes the sexually transmitted disease chancroid and a chronic limb ulceration syndrome in children. In humans, H. ducreyi is found in an abscess and overcomes a hostile environment to establish infection. To sense and respond to membrane stress, bacteria utilize two-component systems (TCSs) and extracytoplasmic function (ECF) sigma factors. We previously showed that activation of CpxRA, the only intact TCS in H. ducreyi, does not regulate homologues of envelope protein folding factors but does downregulate genes encoding envelope-localized proteins, including many virulence determinants. H. ducreyi also harbors a homologue of RpoE, which is the only ECF sigma factor in the organism. To potentially understand how H. ducreyi responds to membrane stress, here we defined RpoE-dependent genes using transcriptome sequencing (RNA-Seq). We identified 180 RpoE-dependent genes, of which 98% were upregulated; a major set of these genes encodes homologues of envelope maintenance and repair factors. We also identified and validated a putative RpoE promoter consensus sequence, which was enriched in the majority of RpoE-dependent targets. Comparison of RpoE-dependent genes to those controlled by CpxR showed that each transcription factor regulated a distinct set of genes. Given that RpoE activated a large number of genes encoding envelope maintenance and repair factors and that CpxRA represses genes encoding envelope-localized proteins, these data suggest that RpoE and CpxRA appear to play distinct yet complementary roles in regulating envelope homeostasis in H. ducreyi.
    Keywords: Gene Expression Regulation, Bacterial ; Stress, Physiological ; Bacterial Proteins -- Metabolism ; Cell Membrane -- Physiology ; Haemophilus Ducreyi -- Physiology ; Protein Kinases -- Metabolism ; Sigma Factor -- Metabolism
    ISSN: 00219193
    E-ISSN: 1098-5530
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  • 7
    Language: English
    In: PLoS ONE, 01 January 2015, 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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  • 8
    Language: English
    In: The Journal of infectious diseases, 01 June 2009, Vol.199(11), pp.1671-9
    Description: Haemophilus ducreyi causes chancroid, which facilitates transmission of human immunodeficiency virus type 1. To better understand the biology of H. ducreyi, we developed a human inoculation model. In the present article, we describe clinical outcomes for 267 volunteers who were infected with H. ducreyi. There was a relationship between papule formation and estimated delivered dose. The outcome (either pustule formation or resolution) of infected sites for a given subject was not independent; the most important determinants of pustule formation were sex and host effects. When 41 subjects were infected a second time, their outcomes segregated toward their initial outcome, confirming the host effect. Subjects with pustules developed local symptoms that required withdrawal from the study after a mean of 8.6 days. There were 191 volunteers who had tissue biopsy performed, 173 of whom were available for follow-up analysis; 28 (16.2%) of these developed hypertrophic scars, but the model was otherwise safe. Mutant-parent trials confirmed key features in H. ducreyi pathogenesis, and the model has provided an opportunity to study differential human susceptibility to a bacterial infection.
    Keywords: Chancroid -- Microbiology ; Haemophilus Ducreyi -- Pathogenicity
    ISSN: 0022-1899
    E-ISSN: 15376613
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  • 9
    Language: English
    In: The Journal of infectious diseases, 15 August 2009, Vol.200(4), pp.590-8
    Description: The role of natural killer (NK) cells in the host response to Haemophilus ducreyi infection is unclear. In pustules obtained from infected human volunteers, there was an enrichment of CD56bright NK cells bearing the activation markers CD69 and HLA-DR, compared with peripheral blood. To study the mechanism by which H. ducreyi activated NK cells, we used peripheral blood mononuclear cells from uninfected volunteers. H. ducreyi activated NK cells only in the presence of antigen-presenting cells. H. ducreyi-infected monocytes and monocyte-derived macrophages activated NK cells in a contact- and interleukin-18 (IL-18)-dependent manner, whereas monocyte-derived dendritic cells induced NK activation through soluble IL-12. More lesional NK cells than peripheral blood NK cells produced IFN-gamma in response to IL-12 and IL-18. We conclude that NK cells are recruited to experimental lesions and likely are activated by infected macrophages and dendritic cells. IFN-gamma produced by lesional NK cells may facilitate phagocytosis of H. ducreyi.
    Keywords: Haemophilus Ducreyi ; Chancroid -- Immunology ; Killer Cells, Natural -- Physiology ; Lymphocyte Activation -- Physiology
    ISSN: 0022-1899
    E-ISSN: 15376613
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  • 10
    In: Journal of Bacteriology, Feb, 1996, Vol.178(3-4), p.808(9)
    Description: A study was conducted to determine the role of the pili expressed by Haemophilus ducreyi in the pathogenesis of the genital ulcer disease chancroid. A gene encoding the 24K protein of fine, tangled pili, termed ftpA, was isolated and examined by molecular techniques. The results showed that the FtpA protein lacked homology with other pilins, but shared homoloy with proteins that polymerize ordered rings in Escherichia coli and Treponema pallidum.
    Keywords: Hemophilus Infections -- Genetic Aspects
    ISSN: 0021-9193
    E-ISSN: 10985530
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