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Characterisation of an outer membrane protein of Moraxella catarrhalis
K E Mathers1, D Goldblatt, C Aebi
1Immunobiology Unit, Institute of Child Health, London, UK.
Abstract:
To elucidate potential vaccine antigens, Moraxella catarrhalis outer membrane proteins (OMPs) were studied. We have previously shown an OMP to be a target for human IgG and have now further characterised this OMP which appears to have a molecular mass of 84 kDa and to be distinct from the 81-kDa OMP, CopB. Human transferrin was shown to bind the 84-kDa OMP alone. N-terminal sequencing of this OMP and purified M. catarrhalis transferrin binding protein B (TbpB) revealed homology both with each other and with the TbpB of Haemophilus influenzae and Neisseria meningitidis. Adsorption of human anti-serum with purified TbpB from two M. catarrhalis strains abolished or reduced binding of IgG to the 84-kDa OMP from three M. catarrhalis isolates. IgG binding to CopB was unaffected. It is clear that the 84-kDa OMP is distinct from CopB and is a likely homologue of TbpB.
Insights
Researchers identified an 84 kDa outer membrane protein (OMP) in Moraxella catarrhalis as a potential vaccine antigen. This OMP is a homologue of transferrin binding protein B (TbpB) and distinct from CopB.
Area of Science:
- Microbiology
- Immunology
- Vaccine Development
Background:
- Moraxella catarrhalis is a significant human pathogen.
- Outer membrane proteins (OMPs) are key targets for vaccine development.
- Previous studies identified an OMP as a target for human IgG.
Purpose of the Study:
- To characterize a specific 84 kDa OMP from M. catarrhalis.
- To determine if this OMP is a homologue of transferrin binding protein B (TbpB).
- To assess its potential as a vaccine antigen.
Main Methods:
- Protein characterization including molecular mass determination.
- N-terminal sequencing of the 84 kDa OMP and M. catarrhalis TbpB.
- Analysis of human IgG binding to OMPs via antiserum adsorption assays.
Main Results:
- The 84 kDa OMP was found to bind human transferrin.
- N-terminal sequencing revealed homology between the 84 kDa OMP and TbpB from M. catarrhalis, H. influenzae, and N. meningitidis.
- Adsorption with TbpB reduced IgG binding to the 84 kDa OMP, confirming it as a TbpB homologue distinct from CopB.
Conclusions:
- The 84 kDa OMP is a likely homologue of M. catarrhalis TbpB.
- This TbpB homologue is a potential target for vaccine development against M. catarrhalis infections.