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Antigenic characterization of dimorphic surface protein in Mycobacterium tuberculosis
Takashi Matsuba1, Umme Ruman Siddiqi2, Toshio Hattori2
1Division of Bacteriology, Department of Microbiology and Immunology, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago, Tottori 683-8503, Japan matsubat@med.tottori-u.ac.jp.
FEMS Microbiology Letters
|May 19, 2016
Summary
A single amino acid change in the Mycobacterium tuberculosis Rv0679c protein alters its antigenicity. This antigenic variation in Beijing genotype strains may impact immune responses and tuberculosis diagnostics.
Area of Science:
- Immunology
- Microbiology
- Molecular Biology
Background:
- The Mycobacterium tuberculosis Rv0679c protein is a surface protein involved in host cell invasion.
- A specific genetic mutation in the Beijing genotype family results in an asparagine to lysine substitution at codon 142 of Rv0679c.
Purpose of the Study:
- To investigate the immunological consequences of the asparagine to lysine substitution at codon 142 of the Mycobacterium tuberculosis Rv0679c protein.
- To determine the impact of this single amino acid change on antibody binding and epitope recognition.
Main Methods:
- Recombinant Rv0679c proteins (Asn142 and Lys142 variants) were expressed in Escherichia coli and Mycobacterium smegmatis.
- Antigenic characterization was performed using antisera and monoclonal antibodies (5D4-C2 and 8G10-H2) via ELISA and Western blot.
- Epitope mapping was conducted to identify linear and conformational epitopes.
Main Results:
- The Lys142-type Rv0679c protein exhibited significantly reduced antibody binding compared to the Asn142-type, particularly with the 8G10-H2 antibody.
- Western blot analysis showed a loss of signal for the 8G10-H2 antibody when using proteins expressed by recombinant mycobacteria.
- Epitope mapping revealed that the antibody recognizing the conformational epitope (8G10-H2) only bound to the Asn142-type protein.
Conclusions:
- A single amino acid substitution (Asn142Lys) in Mycobacterium tuberculosis Rv0679c can cause significant antigenic changes.
- These antigenic variations, particularly affecting conformational epitopes, may be relevant for Beijing genotype strains and influence immune recognition in tuberculosis.
