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Updated: Jul 8, 2026
Assays for Studying the Role of Vitronectin in Bacterial Adhesion and Serum Resistance
Published on: October 16, 2018
Outer membrane protein DsrA is the major fibronectin-binding determinant of Haemophilus ducreyi
Isabelle Leduc1, C Dinitra White, Igor Nepluev
1Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7031, USA.
Abstract:
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.
Insights
DsrA is the primary factor enabling Haemophilus ducreyi to bind fibronectin (FN), a key virulence trait for this skin pathogen. This binding is influenced by heme and hemoglobin levels.
Area of Science:
- Microbiology
- Pathogenesis
- Molecular Biology
Background:
- Extracellular matrix protein binding is crucial for skin pathogen virulence.
- Haemophilus ducreyi, the cause of chancroid, binds fibronectin (FN).
Purpose of the Study:
- To investigate the mechanism of fibronectin (FN) binding by Haemophilus ducreyi.
- To identify the specific bacterial factors involved in this interaction.
Main Methods:
- Comparative analysis of FN binding in wild-type, dsrA mutant, and complemented H. ducreyi strains.
- Assessment of FN binding in various single and double mutants lacking specific outer membrane proteins.
- Functional assays using monoclonal antibodies against DsrA.
- Cross-species complementation experiments with Haemophilus influenzae.
Main Results:
- Heme availability significantly increased H. ducreyi FN binding, while hemoglobin inhibited it.
- The dsrA gene was identified as the major determinant of FN binding.
- Expression of dsrA restored FN binding in a mutant strain and conferred binding to H. influenzae.
- Other characterized proteins (hemoglobin receptor, collagen-binding protein, lectin, pili, OmpA2) were not essential for FN binding.
- A minor role for the major outer membrane protein (MOMP) was suggested in a dsrA mutant.
Conclusions:
- DsrA is the principal mediator of fibronectin (FN) binding in both Class I and Class II Haemophilus ducreyi strains.
- DsrA also mediates vitronectin binding, highlighting its broader role in matrix interactions.
- Understanding DsrA's function provides insights into H. ducreyi pathogenesis.
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