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Adherence to various host cell lines of Mycoplasma bovis strains differing in pathogenic and cultural features
1Department of Infectious and Parasitic Diseases, Faculty of Veterinary Medicine, University of Liège, B43A, Sart Tilman, 4000, Liège, Belgium. athomas@ulg.ac.be
Abstract:
Mycoplasma bovis is known to be responsible for pneumonia and arthritis in calves, as well as mastitis in dairy cows. Despite clear evidence of its pathogenic potential, little is known about mechanisms of cytadherence and the molecular factors involved. The purpose of this work was to compare adherence rates of M. bovis field strains to different host cell lines and study the effects of cloning and sub-culturing M. bovis strains on their adherence properties. Eighteen metabolically labeled M. bovis strains isolated from different pathological backgrounds were examined in adherence trials using four different host cell lines, i.e. embryonic bovine lung (EBL), embryonic bovine trachea (EBTr), Madin Darby bovine kidney (MDBK) and rabbit kidney (RK) cells. Although large interstrain variations in adherence rates (3.4-19.1%) were measured they could not be correlated to the pathological background (pneumonia, arthritis or mastitis). Adherence rates to the fibroblast cell line (EBTr) were significantly lower than those to the three epithelial cell lines (EBL, MDBK and RK). The only non-pathogenic strain (221/89) exhibited lower adherence rates than three isolates from clinical mastitis. Interestingly, adherence rates were significantly reduced after in vitro passaging. In contrast, no effect of single cloning of strains on adherence was observed. There was no general correlation between expression of variable surface proteins (Vsps) as monitored by immunoblotting and adherence rates, although alterations in Vsp expression profiles were seen as a consequence of passaging. As there is probably a large number of adhesins, variable and non-variable, on the surface of M. bovis cells the issue is very complex, and the most active components have yet to be identified.
Insights
Mycoplasma bovis adherence varies between host cells and decreases with in vitro passaging, but not cloning. Molecular factors influencing cytadherence remain complex and unidentified.
Area of Science:
- Veterinary Microbiology
- Bacterial Pathogenesis
- Cell Adhesion
Background:
- Mycoplasma bovis causes significant diseases in cattle, including pneumonia, arthritis, and mastitis.
- The molecular mechanisms and factors governing M. bovis cytadherence to host cells are poorly understood.
- Understanding M. bovis adherence is crucial for developing effective control strategies.
Purpose of the Study:
- To compare the adherence rates of various M. bovis field strains to different host cell lines.
- To investigate the impact of in vitro cloning and sub-culturing on M. bovis adherence properties.
- To explore potential correlations between adherence, pathogenicity, and variable surface protein (Vsp) expression.
Main Methods:
- Eighteen M. bovis strains from diverse pathological origins were metabolically labeled.
- Adherence assays were performed using four distinct host cell lines: embryonic bovine lung (EBL), embryonic bovine trachea (EBTr), Madin Darby bovine kidney (MDBK), and rabbit kidney (RK).
- Variable surface protein (Vsp) expression was monitored using immunoblotting.
Main Results:
- Significant inter-strain variation in adherence rates (3.4-19.1%) was observed, but not correlated with the pathological source (pneumonia, arthritis, mastitis).
- M. bovis exhibited lower adherence to the fibroblast cell line (EBTr) compared to epithelial cell lines (EBL, MDBK, RK).
- In vitro passaging significantly reduced adherence rates, while single cloning had no observable effect. Vsp expression profiles changed with passaging, but no direct correlation with adherence was found.
Conclusions:
- M. bovis adherence is complex, influenced by host cell type and in vitro passage history.
- Passaging in vitro diminishes M. bovis adherence, suggesting adaptation or loss of adherence factors.
- The identification of specific adhesins involved in M. bovis cytadherence requires further investigation due to the complexity of surface proteins.