Abstract
Mycoplasma hyopneumoniae is an important respiratory pathogen that causes great economic losses to the pig industry worldwide. Although some putative virulence factors have been reported, pathogenesis remains poorly understood. Herein, we evaluated the relative abundance of proteins in virulent 168 (F107) and attenuated 168L (F380) M. hyopneumoniae strains to identify virulence-associated factors by two-dimensional electrophoresis (2-DE). Seven proteins were found to be ≥ 1.5-fold more abundant in 168, and protein–protein interaction network analysis revealed that all seven interact with putative virulence factors. Unexpectedly, six of these virulence-associated proteins are encoded by core rather than accessory genomic elements. The most differentially abundant of the seven, fructose-1,6-bisphosphate aldolase (FBA), was successfully cloned, expressed and purified. Flow cytometry demonstrated the surface localisation of FBA, recombinant FBA (rFBA) mediated adhesion to swine tracheal epithelial cells (STEC), and anti-rFBA sera decreased adherence to STEC. Surface plasmon resonance showed that rFBA bound to fibronectin with a moderately strong KD of 469 nM. The results demonstrate that core gene expression contributes to adhesion and virulence in M. hyopneumoniae, and FBA moonlights as an important adhesin, mediating binding to host cells via fibronectin.
Highlights
Mycoplasma hyopneumoniae is the etiological agent of porcine enzootic pneumonia, one of the most damaging respiratory diseases affecting pig farming
The results show that lung lesion levels indicated by the sum of seven pulmonary lobes in the group challenged with M. hyopneumoniae strain 168 were significantly higher than those in the group challenged with strain 168L (Figure 1)
The expression of special elements encoded in the accessory genome, especially unique genomic elements carried by pathogenic strains, is generally considered to be associated with virulence [38]
Summary
Mycoplasma hyopneumoniae is the etiological agent of porcine enzootic pneumonia, one of the most damaging respiratory diseases affecting pig farming. Several proteins are involved in adhesion, including P97, the first adhesin to be identified in this species, which binds to the cilia of respiratory epithelial cells via its C-terminal R1 domain [4] Other adhesion factors, such as P102 [5, 6], P159 [7], P146 [8], P216 [9], P116 [10], Mhp271 [11], Mhp683 [12], Mhp107 [13] and so on have since been reported. These adhesins, and multifunctional cytosolic proteins “moonlighting” at the cell surface contribute to M. hyopneumoniae adhesion [14]. They include the following: MHJ_0125, a glutamyl aminopeptidase that moonlights as an adhesin on the surface of M. hyopneumoniae [15]; MHJ_0461, a leucine aminopeptidase which binds to heparin, plasminogen and foreign DNA and functions as an accessory adhesin [16]; and l-lactate dehydrogenase, an immunogenic cytoplasmic protein involved in the glycolytic process and present at
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