FIMBRIAE AND THE HEMAGGLUTINATING ADHESIN HA-AG2 MEDIATE ADHESION OF PORPHYROMONAS-GINGIVALIS TO EPITHELIAL-CELLS

The mechanisms by which Porphyromonas gingivalis, a gram-negative anae robic bacterium, is pathogenic for the periodontium remain largely hyp othetical, Invasion of host tissues by P. gingivalis is believed to re quire adhesion of the bacterium to host cells, The aim of this study w as to use monoclonal antibodies (MAbs) to characterize the bacterial c ell surface component(s) acting as a ligand binding to a receptor on e pithelial cells, Surface antigens of P. gingivalis ATCC 33277 were obt ained as a glass bead-EDTA extract (GEE), and antiserum against the GE E was produced in rabbits. Epithelial cell membrane proteins (ECMP) we re prepared from a homogenate of the SK-MES-1 cell line with Triton X- 100, The antigen/ligand profile of GEE was resolved by crossed immunoa ffinity electrophoresis by using ECMP in the first-dimension gel, The migration of one immunoprecipitate (IF) was retarded, indicating a lig and-receptor interaction between a surface antigen of P. gingivalis an d a complementary binding site on the epithelial cell membrane, The co rresponding IP in the GBE/anti-GBE immunoelectrophoresis profile was e xcised from replicate gels to immunize mice for production of MAbs spe cific for the bacterial ligand. Five MAbs were obtained and tested for reactivity with GEE in immunoblots and for inhibition of the interact ion between GEE and ECMP, Immunoblots revealed polypeptides at 28, 42, 43, and 49 kDa. Inhibition tests were positive for all five MAbs, The se results are conclusive evidence that the MAbs recognize functional epitopes involved in the adherence of P. gingivalis to epithelial cell s and that the adhesins are likely associated with fimbriae and the he magglutinating adhesin HA-Ag2.