Immunochemical analysis and localisation of a cell wall antigen of Streptococcus rattus with a specific monoclonal antibody

Abstract

A monoclonal antibody specific to a cell wall antigen of Streptococcus rattus (S. rattus) was prepared after cell fusion of mouse myeloma cells to the spleen cells of mice immunized with whole cells of strain FA1. The monoclonal antibody reacted with a crude and purified polysaccharide antigen of S. rattus in precipitin reactions as well as in a solid phase enzyme assay (EIA). It also reacted in the EIA with whole cells of S. rattus strains, but did not react with any other species of the mutans group or of other oral and streptococcal species. Moreover, among many haptenic sugars and their derivatives tested, D-galactosamine and D-glucosamine strongly inhibited the reaction in a competitive enzyme immunoassay using the purified antigen and whole cells, indicating that the type-specific antigenic determinant of the organism has a structure similar to the amino group of the sugar molecules. Furthermore, immunoelectron microscopy revealed that the antigen epitopes formed an irregular fibrous structure over the entire surface of individual cells.