PURIFICATION OF A GALACTOSYL-ALPHA-1-4-GALACTOSE-BINDING ADHESIN FROMTHE GRAM-POSITIVE MENINGITIS-ASSOCIATED BACTERIUM STREPTOCOCCUS-SUIS

Streptococcus suis causes meningitis, sepsis, and other serious infect ions in newborn and young pigs and in adult humans. The Gal alpha 1-4G al-binding adhesin of S. suis was purified to homogeneity by ultrasoni c treatment, fractional ammonium sulfate precipitation, and preparativ e polyacrylamide gel electrophoresis. Pigeon ovomucoid, a glycoprotein with Gal alpha 1-4Gal terminals, was used to detect the adhesin by bl otting. The purified adhesin appeared as single band of an apparent si ze of 18 kDa and of a pI of 6.4; no disulfide bridges were present. Th e amount of adhesin as revealed by pigeon ovomucoid binding correlated with the hemagglutination activity of different S. suis strains. The purified adhesin bound to latex particles induced hemagglutination whi ch was specifically inhibited with the same inhibitors as hemagglutina tion by the intact bacteria, thus demonstrating that the purified prot ein was the Gal alpha 1-4Gal-recognizing adhesin of S. suis. Two adhes in variants (P-N and P-O) with differing Gal alpha 1-4Gal binding spec ificity had the similar electrophoretic mobilities and the same N-term inal peptide sequences, indicating that they were closely related. Thi s represents the first isolation of an adhesin with well defined cell surface carbohydrate binding activity from Gram-positive bacteria asso ciated with meningitis.