Glycolipid Receptors forAttachment ofMycoplasma hyopneumoniae toPorcine Respiratory Ciliated Cells

(GDla, GDlb,andGD3),trisialoganglioside (GTlb), cholesterol, cholesterol sulfate, palmitic acid, tripalmitin, orcholesteryl palmitate was detected. Total lipids extracted fromcilia oftheswinerespiratory epithelium, thenatural targets ofM.hyopneumoniae infection, were alsoseparated on TLC plates andoverlaid withmycoplasmas. M.hyopneumoniae bound specifically tothree ciliary glycolipids identified asLa,Lb,andLc.Binding toLcwas stronger thantoLaand Lb.Allthree lipids werebelieved tobesulfated glycolipids, asdetermined bylaminin binding andstaining with azureA.Lcwas identified asaputative sulfatide because ithadamobility similar tothatofauthentic sulfatide andcomigrated withsulfatide on TLCplates. Laminin boundtoLa,Lb,andLcandproduced dose-dependent inhibition ofadherence ofthemycoplasma tothethreeciliary receptors. Binding ofthemycoplasma to sulfatide, La,Lb,andLcwas partially inhibited bydextran sulfate, heparin, fucoidan, mucin, andchondroitin sulfate B.Thesesubstances blocked theadherence ofM.hyopneumoniae tocilia andciliated cells asshownin a previous study (Q.Zhang, T.F.Young, andR.F.Ross, Infect. Immun.62:1616-1622, 1994). Theseresults indicate thatLa,Lb,andLc arethemajornative receptors forM.hyopneunoniae adherence tociliated cells. Mycoplasmal pneumonia ofswine, causedbyMycoplasma hyopneumoniae, isaworldwide, economically important swine disease (28). Lackofknowledge aboutthepathogenic mech- anismsandvirulence factors involved inM.hyopneumoniae infection isa limiting factor inthedevelopment ofhighly effective vaccines forcontrol ofmycoplasmal pneumonia of swine. M.hyopneumoniae colonizes thesurface ofciliated cells inthetracheas, bronchi, andbronchioles ofpigs anddoesnot invade epithelial cells (1,28).Intimate attachment ofthis organism tocilia during infection hasbeenwelldocumented (2,23,32). Thisassociation leads toprogressive lossofcilia, desquamation oftheepithelium, anddevelopment ofpneumo- nia(28). Bothinvitro andinvivostudies haveshownthatM. hyopneumoniae adheres onlytocilia ofswinerespiratory ciliated cells butnotto nonciliated cells oftheporcine respiratory tract (2,23, 32, 34). Thesedataindicate thatcilia of theporcine respiratory epithelium may havereceptors forM. hyopneumoniae. Mucosal surfaces aretheportsofentryandmajorsites of many infectious agents. Manypathogens, including viruses (6, 22),bacteria (29), andbacterial toxins (8), bindtospecific carbohydrate moieties on themucosal surfaces, enabling col- onization andinfection andpotentially mediating atoxic effect on thehostcells. Thesecarbohydrate moieties may bepresent ineither glycoproteins orglycolipids. Although several invitro adherence modelsforM.hyopneumoniae havebeenestab- lished (31,33-35), theadhesin(s) ofthemycoplasma andits hostreceptors havenotbeenidentified. Ina previous study (33), several carbohydrates andglycoconjugates, including dextran sulfate, heparin, fucoidan, chondroitin sulfate, mucin, andlaminin, inhibited adherence ofthis mycoplasma topor-