Surface parasitism by Mycoplasma pneumoniae of respiratory epithelium.

Abstract

The mechanisms by which virulent microorganisms mediate host cell injury in respiratory tissue are unclear. To better understand the cellular and subcellular events which accompany these infections requires the establishment of experimental models which permit monitoring of the infectious process under experimentally controlled conditions. During the past several years we have examined the capacity of virulent Mycoplasma pneumoniae organisms, human pathogens of the respiratory tract, to parasitize and produce cell injury in the respiratory epithelium (1-4). Tracheal organ culture served as the highly sensitive host indicator system and its feasibility for other models is recognized (5-9). Based upon our earlier studies we outlined a two step parasitism: (a) the specific attachment of virulent M. pneumoniae via their tip-like organelle to a sialic acid-associated receptor region on the respiratory epithelium and (b) early abnormal host cell function at the transcriptional or translational levels with subsequent tissue cytopathology resulting from the colonization, multiplication, and continued metabolic activity of attached virulent mycoplasmas. The success of this parasitism appeared initially and critically dependent upon the intimate physical association between the membranes ofM. pneumoniae and respiratory epithelial cells. However, the chemical nature of M. pneumoniae surfaces responsible for attachment was unknown.Limited information is available concerning external membrane components of M. pneumoniae. Razin et al. (10,11) extracted from M. pneumoniae a glycolipid which reacts with complement-fixing and metabolic-and growth-inhibiting antibodies raised against intact organisms suggesting a possible surface location of the glycolipid moiety. Additional nonprotein haptens have been demonstrated in other mycoplasma species (12, 13). Boatman and Kenny (14) reported that spherules of M. pneumoniae organisms which form during growth can be disaggregated into individual and viable mycoplasmas by treatment with crude lipase. This observation implied that a lipid moiety on the surface of M. pneumoniae might be responsible for their "stickiness." Other studies with Mycoplasma hominis indicated that membrane proteins exist as receptors for the adsorption of HeLa cells (15) and for indirect hemagglutination activity (16). In this report we examine the unique interaction between virulent M. pneumo-

Mycoplasma adhesion

“…Electrophoretic analysis of the treated mycoplasmas indicated the digestion of two membrane proteins. The protein with the higher molecular mass, estimated at 170-190 kDa, was named P1 (Hu et al, 1977). Subsequent studies established that protein PI is the major adhesin of M. pneumoniae (Hu et al, 1982;Baseman et al, 1982;Feldner et al, 1982).…”

“…The first indication of the protein nature of M. pneumoniae adhesins came from observations that mild trypsin treatment of M. pneumoniae cells abolished their ability to adhere to tracheal epithelium and erythrocytes (Hu et al, 1977;Gorski & Bredt, 1977). Electrophoretic analysis of the treated mycoplasmas indicated the digestion of two membrane proteins.…”

The proline-rich P65 protein of Mycoplasma pneumoniae is a component of the Triton X-100-insoluble fraction and exhibits size polymorphism in the strains M129 and FH

“…A critical step in bacterial colonization of the host cells is the specific adhesion to host cell receptors, mediated by bacterial adhesins. In M. pneumoniae, the P1 adhesin (3,17,25,26) and the adhesin-related 30-kDa protein (4, 10) have been identified. Both proteins are located mainly in a tip structure that functions as the attachment organelle of the bacterium.…”

“…Mycoplasma pneumoniae is an extracellular pathogen of the human respiratory tract (26,46) causing histopathological changes of lung epithelial cells, usually in older children and young adults (18). A critical step in bacterial colonization of the host cells is the specific adhesion to host cell receptors, mediated by bacterial adhesins.…”

Adherence of Mycoplasma gallisepticum to Glass

“…The nature of the binding sites on the mycoplasma surface is less clear, although recently a membrane protein has been implicated as the binding site of M . pneumoniae responsible for its attachment to tracheal epithelial cells (Hu et al, 1977).…”