INHIBITION OF ADHERENCE OF ACTINOMYCES-NAESLUNDII (ACTINOMYCES-VISCOSUS) T14V-J1 TO SALIVA-TREATED HYDROXYAPATITE BY A MONOCLONAL-ANTIBODY TO TYPE-1 FIMBRIAE

A monoclonal antibody to Actinomyces naeslundii (A. viscosus) T14V-J1 type 1 fimbriae, capable of inhibiting the adherence of this bacterium to salivary proline-rich protein-treated hydroxyapatite, was generate d by immunization of SWR mice with A. naeslundii 55-19, a strain deriv ed from T14V-J1 that possesses only type 1 fimbriae. Supernatants of h ybridomas were screened for reactivity with purified type 1 fimbriae. An IgG monoclonal antibody, 86-49E, blocked the adsorption of the pare nt strain to proline-rich protein-treated hydroxyapatite by 77% with 1 .0 mu g/ml of the monoclonal antibody; the Fab fragment derived from t his monoclonal antibody inhibited adherence by 38% at the same concent ration. Similarly, the adherence of strain 55-19 was inhibited by 100% and 64% to proline-rich protein-treated hydroxyapatite with 1.0 mu g/ ml of Ige and Fab fragments respectively. Control monoclonal antibody to the subunit of type 1 fimbriae, as well as to Actinobacillus actino mycetemcomitans caused only minimal adherence inhibition. Monoclonal a ntibody 86-49E also agglutinated both type 1 fimbriae-bearing strains of A. naeslundii T14V-J1 and 55-19 but not strains 59-51 and 147, whic h lack type 1 fimbriae. Further confirmation of the specificity of mon oclonal antibody 86-49E was obtained using these fimbria-deficient mut ant strains in an enzyme-linked immunosorbent assay, with the monoclon al antibody binding only to strains possessing type 1 fimbriae. Immuno gold labeling in conjunction with electron microscopy suggested bindin g of monoclonal antibody 86-49E occurring near the distal end of the f imbriae. In contrast, when a monoclonal antibody specific for the type 1 fimbrial subunit but not capable of adherence inhibition was used t ogether with 86-49E in double-labeling experiments, extensive labeling of the fimbriae by the subunit antibody was noted. These data suggest that a monoclonal antibody specific for the type 1 fimbriae of A. nae slundii that is capable of binding to a discrete site on the fimbriae has the capacity to inhibit the adsorption of this organism to saliva- treated hydroxyapatite.