IDENTIFICATION AND CHARACTERIZATION OF A MYCOPLASMA-HYOPNEUMONIAE ADHESIN

An adhesin of Mycoplasma hyopneumoniae was identified and characterize d in this study. A monoclonal antibody (MAb), F2G5, and its F(ab')(2) fragments inhibited the adherence of M. hyopneumoniae tb porcine trach eal cilia, the natural targets to which the mycoplasma binds during in fection. MAb F2G5 detected multiple bands, but predominantly recognize d a 97-kDa (P97) protein of M. hyopneumoniae on immunoblots. Affinity chromatography, conducted with immobilized MAb F2G5, mainly purified P 97. The purified proteins were able to bind to cilia and blocked the a dherence of intact M. hyopneumoniae cells to cilia. Immunolabeling of mycoplasmas with MAb F2G5 under electron microscopy demonstrated that the proteins recognized by MAb F2G5 were located at the surface of the mycoplasma, predominantly on a surface fuzzy layer. These results ind icate that P97 functions as an adhesin of M. hyopneumnoniae. The N-ter minal amino acid sequence of P97 did not have significant homology wit h any known bacterial or mycoplasmal adhesins, suggesting that P97 is a novel protein. The predominant proteins detected by MAb F2G5 in diff erent strains varied in size, indicating that the antigen bearing the epitope for MAb F2G5 undergo intraspecies size variation. Antigenic va riation of adhesins maybe a pathogenic mechanism utilized by M. hyopne umoniae to evade the porcine immune system.