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A newly identified immunodominant membrane protein (pMB67) involved in Mycoplasma bovis surface antigenic variation
A Behrens1, F Poumarat, D Le Grand
1Institut für Mikrobiologie und Tierseuchen, Tierärztliche Hochschule Hannover, Germany.
Abstract:
Mycoplasma bovis is a bovine pathogen able to cause systemic disease. It possesses a series of prominent, structurally related yet clearly distinguishable membrane lipoproteins on the cell surface. These variable surface proteins (Vsps) undergo highly dynamic and spontaneous changes in size and expression and are key immunogenic components. They may play a critical role as mediators of adherence to host cells and in escaping immune destruction. In this report, we define a novel, Vsp-unrelated membrane protein also associated with M. bovis surface antigenic variation. This protein has an apparent molecular mass of 67,000 Da in the type strain PG45 and was designated pMB67. Immunological and biochemical characterization of pMB67 demonstrated that it: (i) contains a specific epitope, (ii) is not modified by lipid but does contain cysteine, (iii) does not contain a Vsp-like repetitive periodic protein structure, (iv) is a predominant antigen recognized during M. bovis infections, (v) undergoes a high rate of phase variation in vitro and (vi) is size-variable. These results showed that M. bovis employs two types of specialized membrane proteins for surface diversification. The pMB67 protein may be useful in diagnostic assays and as a vaccine component.
Insights
Mycoplasma bovis utilizes two distinct membrane proteins for surface variation, including a newly identified protein, pMB67. This novel antigen is crucial for immune evasion and shows potential for diagnostics and vaccines.
Area of Science:
- Veterinary Microbiology
- Bacterial Pathogenesis
- Immunology
Background:
- Mycoplasma bovis is a significant bovine pathogen causing systemic infections.
- The bacterium exhibits surface antigenic variation mediated by prominent lipoproteins called variable surface proteins (Vsps).
- Vsps are crucial for host cell adherence and immune evasion.
Purpose of the Study:
- To identify and characterize novel M. bovis surface antigens involved in antigenic variation.
- To investigate a newly discovered membrane protein, pMB67, unrelated to Vsps.
- To assess the potential diagnostic and vaccine applications of pMB67.
Main Methods:
- Immunological characterization of pMB67.
- Biochemical analysis of pMB67 structure and modifications.
- In vitro phase variation assays.
- Molecular mass determination using SDS-PAGE.
Main Results:
- A novel M. bovis membrane protein, pMB67 (67 kDa), was identified and characterized.
- pMB67 possesses a unique epitope, contains cysteine, lacks lipid modification, and is not Vsp-like.
- pMB67 is a predominant antigen during M. bovis infections, exhibits high-rate phase variation, and is size-variable.
- M. bovis employs at least two distinct mechanisms for surface protein diversification.
Conclusions:
- M. bovis utilizes both Vsps and pMB67 for surface diversification and immune evasion.
- pMB67 represents a novel target for diagnostic assays.
- pMB67 shows promise as a component in future M. bovis vaccines.