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PorB3 outer membrane protein on Neisseria meningitidis is poorly accessible for antibody binding on live bacteria
T E Michaelsen1, A Aase, J Kolberg
1Department of Vaccinology, National Institute of Public Health, P.O. Box 4404 Torshov, 0403, Oslo, Norway. terje.michaelsen@folkehelsa.no
Abstract:
It is reported here that the PorB3 porin proteins of serotype 4 and 15 are poorly accessible for antibody binding on live Neisseria meningitidis bacteria, whereas the allelic PorB2 and the PorA outer membrane protein appear to be highly accessible. This was revealed by flow cytometry analysis using several mouse monoclonal antibodies (mAbs) as well as PorB3 specific antibodies isolated from post vaccination and patient sera. However, strong antibody binding to the PorB3 protein was observed after killing the bacteria with ethanol. The reason for the lack of epitope exposure could be a shielding effect of the carbohydrate chains of lipopolysaccharides (LPS) possibly combined with short extra-cellular loops in the PorB3 protein. The findings indicate that the PorB3 protein is not an optimal target for protective antibodies induced by vaccination.
Insights
Antibodies poorly bind Neisseria meningitidis PorB3 porin on live bacteria, unlike PorB2 and PorA. This suggests PorB3 is not an optimal target for vaccine-induced protective antibodies.
Area of Science:
- Microbiology
- Immunology
- Bacterial Outer Membrane Proteins
Background:
- Neisseria meningitidis is a leading cause of bacterial meningitis.
- Outer membrane proteins like PorA and PorB are key targets for vaccines.
- Accessibility of surface proteins affects immune responses.
Purpose of the Study:
- To investigate the antibody accessibility of PorB3 porin on live Neisseria meningitidis.
- To compare PorB3 accessibility with other outer membrane proteins (PorA, PorB2).
- To evaluate PorB3 as a potential target for protective antibodies.
Main Methods:
- Flow cytometry analysis of live and ethanol-killed Neisseria meningitidis.
- Utilized mouse monoclonal antibodies (mAbs) and patient/post-vaccination sera.
- Tested antibodies specific to PorB3, PorB2, and PorA proteins.
Main Results:
- PorB3 porins on live bacteria showed poor antibody accessibility.
- PorB2 and PorA outer membrane proteins exhibited high antibody accessibility.
- Strong antibody binding to PorB3 was observed only after bacterial killing.
Conclusions:
- Lipopolysaccharide (LPS) shielding and short extracellular loops likely limit PorB3 epitope exposure.
- PorB3 is not an optimal target for developing protective antibodies via vaccination.
- Understanding protein accessibility is crucial for effective vaccine design against Neisseria meningitidis.