Antibodies against the Ag2 fimbriae of Actinomyces viscosus T14V inhibit lactose-sensitive bacterial adherence.

Monospecific antisera against the Ag1 and Ag2 fimbrial components of Actinomyces viscosus T14V were produced by immunizing rabbits with immune precipitates of each antigen harvested from crossed-immunoelectrophoresis plates. The Fab fragments prepared from these sera were used as specific reagents in immunoelectron microscopy to identify each fimbrial component on the bacterial surface and also were assayed for their abilities to prevent the coaggregation of A. viscosus T14V with Streptococcus sanguis 34, an interaction that is lactose sensitive. Each Fab preparation appeared to react with different fibrillar structures present on the actinomycete, and only the Ag2-specific Fabs blocked coaggregation. These results provide strong support for the presence of distinct types of fimbriae on A. viscosus T14V and indicate the exclusive involvement of Ag2 fimbriae in lactose-sensitive adherence.