Immunological analysis of a cell surface antigen by a monoclonal antibody SNH-3 in oral streptococci

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The expression of sialyl-Lewis^X (sLe^X ; Neu5Ac alpha2-3 Gal beta1-4 (Fuc alpha1-3) GlcNAc-R) on oral bacteria producing infective endocarditis was determined by a whole-cell enzyme linked immuno-sorbent assay and an immuno-electron microscopy using the well-characterized anti-sLe^X monoclonal antibody SNH-3 (MAb SNH-3 ; IgM class). mAb SNH-3 reacted strongly with whole cells of oral bacteria-Streptococcus sanguis, Streptococcus mutans, Streptococcus mitis, Streptococcus salivarius, Streptococcus intermedius, Streptococcus constellatus, Streptococcus anginosus, Streptococcus pyogenes, Actinobacillus actinomycetemcomitans, Eikenella corrodens and Porphyromonas gingivalis. The negatively stained immuno-electron micrograph of Streptococcus pyogenes showed many reactive gold particles on the cell surface. Our findings demonstrated the existence of immunologic mimicry between the sLe^X oligosaccharide and cell surface antigens of many species associated with infective endocarditis. We propose the hypothesis that if these bacteria escape their normal habitats, the surface components that mimic the sLe^X oligosaccharide might bind to host antigens of the selectin family which could promote binding to endothelial cells and, consequently, initiation of the events leading to infective endocarditis.