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Antigenic heterogeneity and molecular analysis of CopB of Moraxella (Branhamella) catarrhalis
S Sethi1, J M Surface, T F Murphy
1Department of Medicine, State University of New York at Buffalo, and Department of Veterans Affairs WNY Healthcare System, 14215, USA.
Abstract:
Outer membrane protein (OMP) CopB, an iron-repressible 81-kDa major OMP of Moraxella (Branhamella) catarrhalis has been a major focus of investigation. To assess CopB as a potential vaccine antigen, we elucidated the degree of antigenic and sequence heterogeneity in this protein among strains of M. catarrhalis. Two monoclonal antibodies, 1F5 and 2.9F, which bind to surface-exposed epitopes on CopB recognized 60 and 70% of the strains, respectively. The degree of sequence heterogeneity in CopB was assessed by cloning and sequencing the CopB gene from two different strains of M. catarrhalis and comparing with the published sequence. There was 92 to 96% homology between the sequences at the nucleotide level and 90 to 95% homology at the amino acid level. The variability in the protein sequence is confined mainly to three moderately variable regions. Restriction fragment length polymorphism (RFLP) analysis of the CopB genes obtained from 20 diverse strains by PCR was performed. Ninety percent of the potential restriction sites in the constant regions and 47% of the potential restriction sites in the variable regions were present in the 20 strains, indicating that the pattern of variable and constant areas in the CopB gene is a general pattern among strains of M. catarrhalis. We conclude that the CopB gene is largely conserved among strains of M. catarrhalis and contains discrete regions which show moderate heterogeneity among strains.
Insights
Outer membrane protein CopB from Moraxella catarrhalis shows significant conservation across strains, with minor variations in specific regions. This suggests potential for developing CopB as a broadly effective vaccine antigen.
Area of Science:
- Microbiology and Immunology
- Vaccine Development
- Bacterial Pathogenesis
Background:
- Moraxella catarrhalis is a significant human pathogen.
- Outer membrane protein CopB is a major OMP and an iron-repressible protein.
- CopB is being investigated as a potential vaccine antigen due to its surface exposure.
Purpose of the Study:
- To evaluate the potential of CopB as a vaccine antigen.
- To determine the antigenic and sequence heterogeneity of CopB among M. catarrhalis strains.
Main Methods:
- Monoclonal antibody binding assays to assess antigenic variation.
- Gene cloning and sequencing to analyze sequence heterogeneity.
- Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis.
Main Results:
- Monoclonal antibodies recognized 60% and 70% of strains, indicating conserved epitopes.
- CopB gene sequences showed 92-96% nucleotide and 90-95% amino acid homology between strains.
- Variability was concentrated in three distinct regions, while other areas remained highly conserved.
- RFLP analysis confirmed conserved and variable regions across 20 diverse strains.
Conclusions:
- The CopB gene is largely conserved among M. catarrhalis strains.
- Discrete regions of moderate heterogeneity exist within the CopB protein.
- The conserved nature of CopB supports its potential as a vaccine candidate.