Proposed second class of <b><i>Haemophilus ducreyi</i></b> strains show altered protein and lipooligosaccharide profiles

Post, Deborah M. B.; Gibson, Bradford W.

doi:10.1002/pmic.200600830

Cited by 23 publications

(16 citation statements)

References 52 publications

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“…It should also be noted that all of the experiments in the present study utilized H. ducreyi 35000HP, a prototypic class I strain of the pathogen (64). Two clonal H. ducreyi populations (i.e., class I and class II) have been described as differing in the expression of certain surface-exposed proteins and lipooligosaccharide (45). Whether gene expression in class II strains of H. ducreyi may differ with regard to regulation by CpxR was not investigated in this study and would need to be addressed in the future.…”

Section: Discussionmentioning

confidence: 99%

Characterization of the CpxRA Regulon in Haemophilus ducreyi

Labandeira-Rey¹,

Brautigam

Hansen³

2010

Infect Immun

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The Haemophilus ducreyi 35000HP genome encodes a homolog of the CpxRA two-component cell envelope stress response system originally characterized in Escherichia coli. CpxR, the cytoplasmic response regulator, was shown previously to be involved in repression of the expression of the lspB-lspA2 operon (M. LabandeiraRey, J. R. Mock, and E. J. Hansen, Infect. Immun. 77:3402-3411, 2009). In the present study, the H. ducreyi CpxR and CpxA proteins were shown to closely resemble those of other well-studied bacterial species. A cpxA deletion mutant and a CpxR-overexpressing strain were used to explore the extent of the CpxRA regulon. DNA microarray and real-time reverse transcriptase (RT) PCR analyses indicated several potential regulatory targets for the H. ducreyi CpxRA two-component regulatory system. Electrophoretic mobility shift assays (EMSAs) were used to prove that H. ducreyi CpxR interacted with the promoter regions of genes encoding both known and putative virulence factors of H. ducreyi, including the lspB-lspA2 operon, the flp operon, and dsrA. Interestingly, the use of EMSAs also indicated that H. ducreyi CpxR did not bind to the promoter regions of several genes predicted to encode factors involved in the cell envelope stress response. Taken together, these data suggest that the CpxRA system in H. ducreyi, in contrast to that in E. coli, may be involved primarily in controlling expression of genes not involved in the cell envelope stress response.

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Section: Discussionmentioning

confidence: 99%

Characterization of the CpxRA Regulon in Haemophilus ducreyi

Labandeira-Rey¹,

Brautigam

Hansen³

2010

Infect Immun

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“…H. ducreyi strains are grouped into classes, termed class I and class II, according to the expression of variant outer membrane determinants and the structure of LOS (33,34,36,48). Although the amino acid sequences of some H. ducreyi surface determinants, such as DsrA and NcaA, differ widely between H. ducreyi strains belonging to different classes, the HgbA protein is highly conserved, with more than 95% identity between HgbA proteins in the two strain classes (26,48).…”

Section: Discussionmentioning

confidence: 99%

Passive Immunization with a Polyclonal Antiserum to the Hemoglobin Receptor of Haemophilus ducreyi Confers Protection against a Homologous Challenge in the Experimental Swine Model of Chancroid

et al. 2011

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Haemophilus ducreyi, the etiologic agent of chancroid, has an obligate requirement for heme. Heme is acquired by H. ducreyi from its human host via TonB-dependent transporters expressed at its bacterial surface. Of 3 TonB-dependent transporters encoded in the genome of H. ducreyi, only the hemoglobin receptor, HgbA, is required to establish infection during the early stages of the experimental human model of chancroid. Active immunization with a native preparation of HgbA (nHgbA) confers complete protection in the experimental swine model of chancroid, using either Freund's or monophosphoryl lipid A as adjuvants. To determine if transfer of anti-nHgbA serum is sufficient to confer protection, a passive immunization experiment using pooled nHgbA antiserum was conducted in the experimental swine model of chancroid. Pigs receiving this pooled nHgbA antiserum were protected from a homologous, but not a heterologous, challenge. Passively transferred polyclonal antibodies elicited to nHgbA bound the surface of H. ducreyi and partially blocked hemoglobin binding by nHgbA, but were not bactericidal. Taken together, these data suggest that the humoral immune response to the HgbA vaccine is protective against an H. ducreyi infection, possibly by preventing acquisition of the essential nutrient heme.

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“…Initial studies of the clonal structure of H. ducreyi showed limited diversity in specific outer membrane components, including DsrA, DltA, NcaA, Hlp, MOMP/OmpA2, and lipooligosaccharide (45). The DNA sequences and immunoreactivity suggested that H. ducreyi formed two potentially clonal populations, termed class I and class II, a division supported by proteomic studies (33). However, the relationships between the two classes are entirely unclear, as genetic differences were assessed only at loci encoding surface-exposed antigens.…”

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confidence: 95%

Rapid Divergence of Two Classes of Haemophilus ducreyi

et al. 2011

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Haemophilus ducreyi, the etiologic agent of chancroid, expresses variants of several key virulence factors. While previous reports suggested that H. ducreyi strains formed two clonal populations, the differences between, and diversity within, these populations were unclear. To assess their variability, we examined sequence diversity at 11 H. ducreyi loci, including virulence and housekeeping genes, augmenting published data sets with PCR-amplified genes to acquire data for at least 10 strains at each locus. While sequences from all 11 loci place strains into two distinct groups, there was very little variation within each group. The difference between alleles of the two groups was variable and large at 3 loci encoding surface-exposed proteins (0.4 < K S < 1.3, where K S is divergence at synonymous sites) but consistently small at genes encoding cytoplasmic or periplasmic proteins (K S < 0.09). The data suggest that the two classes have recently diverged, that recombination has introduced variant alleles into at least 3 distinct loci, and that these alleles have been confined to one of the two classes. In addition, recombination is evident among alleles within, but not between, classes. Rather than clones of the same species, these properties indicate that the two classes may form distinct species.Haemophilus ducreyi is a Gram-negative coccobacillus in the family Pasteurellaceae (2) and the causative agent of chancroid, a sexually transmitted, genital ulcer disease which facilitates transmission of 14,23,44). While H. ducreyi was placed in the polyphyletic genus Haemophilus due to its requirement for hemin, Haemophilus species do not form a cohesive group within the Pasteurellaceae (6, 20). The species that are most closely related to H. ducreyi include Actinobacter pleuropneumoniae and Nicoletella semolina (see Fig. S1 in the supplemental material) (16).Previous attempts to examine the diversity within the species H. ducreyi using immunotyping (36) and outer membrane profiling (32) showed very few differences among strains. Molecular analyses showed some differences, e.g., ribotyping of strains from two outbreaks yielded multiple restriction fragment length polymorphism (RFLP) patterns (19), but designations based on these differences have not been widely adopted or used for epidemiologic studies, in part due to the difficulty in culturing this fastidious organism. The lack of a standard typing system makes epidemiologic studies more difficult, and epidemiologic data for chancroid are therefore limited.One way to study diversity in H. ducreyi is to assess its population structure. Whereas the lack of recombination in some bacterial species generates stable clones (5), others recombine sufficiently rapidly to obscure clonal relationships (10, 11). While many Haemophilus species are naturally competent, H. ducreyi is considered nontransformable due to defects in the DNA uptake apparatus (16,34). This would likely decrease rates of recombination and generate stable clones. Initial studies of the clonal structure of...

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Proposed second class of Haemophilus ducreyi strains show altered protein and lipooligosaccharide profiles

Cited by 23 publications

References 52 publications

Characterization of the CpxRA Regulon in Haemophilus ducreyi

Characterization of the CpxRA Regulon in Haemophilus ducreyi

Passive Immunization with a Polyclonal Antiserum to the Hemoglobin Receptor of Haemophilus ducreyi Confers Protection against a Homologous Challenge in the Experimental Swine Model of Chancroid

Rapid Divergence of Two Classes of Haemophilus ducreyi

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