Specific binding of Streptococcus pneumoniae to two receptor saccharide structures

Specific binding of Streptococcus pneumoniae to two proposed receptor structures was studied in a solid-phase assay. The assay was based on immunodetection of the pneumococci adhering to the receptors coated to microtiter plates. Non-specific binding owing to hydrophobic forces to uncoated wells could be abolished by treatment of the plates with a blocking buffer. Binding of the pneumococcal cells was demonstrated with the glycolipid asialo-GM1 as receptor with a previously suggested specificity for the disaccharide GalNAc beta 1-4Gal. A non-capsulated mutant bound with high efficiency to this receptor. Two capsulated strains also bound well, but with lower efficiency. Binding of the non-capsulated strain was also demonstrated with lactotriaosylceramide as receptor with a suggested specificity for the disaccharide GlcNAc beta 1-3Gal. The binding assay enables the comparison of the adherence of different strains to purified receptor molecules.