CHARACTERIZATION OF MONOCLONAL-ANTIBODIES FOR RAPID IDENTIFICATION OFACTINOMYCES-NAESLUNDII IN CLINICAL-SAMPLES

The purpose of this study was to generate highly specific serological reagents for the quantitative identification of Acrinomyces naeslundii in clinical samples, in particular dental plaque. Balb/c mice were im munized with pasteurized human A. naeslundii strains representing diff erent genospecies and serotypes. Ten hybrid cell lines secreting monoc lonal antibodies reactive with A. naeslundii were isolated and charact erized. Antibody specificity was determined by indirect immunofluoresc ence and enzyme-linked immunosorbent assay using strains from 59 speci es and by immunofluorescence analyses of supragingival plaque from IO gingivitis patients. Nine monoclonal antibodies reacted selectively wi th A. naeslundii, whereas one additionally bound to Actinomyces israel ii. They recognized at least nine different epitopes with characterist ic expression patterns among the test strains. Six clusters of antigen ically unique or closely related strains could be distinguished. Clust ers 1, 4, and 5 represented by 12, 18, and 5 strains, respectively, co mprised over 80% of the A. naeslundii strains tested. All reference st rains for genospecies 1 grouped with cluster 1. Strains associated wit h genospecies 2 fell into clusters 4 and 5. Tests with mutant strains indicated that three monoclonal antibodies recognize type 2 and one ty pe 1 fimbriae of genospecies 2. Only four isolates grouped with cluste rs 2 and 3 characterized by the expression of cluster-specific antigen s. Interestingly, duster 2 and 3 bacteria were markedly more abundant in vivo than indicated by their sparse representation in our strain co llection. Overall, all but one of the new monoclonal antibodies should prove of value for the serological classification and rapid quantitat ive determination of A. naeslundii in clinical samples.