THE GALACTOSYL-(ALPHA-1-4)-GALACTOSE-BINDING ADHESIN OF STREPTOCOCCUS-SUIS - OCCURRENCE IN STRAINS OF DIFFERENT HEMAGGLUTINATION ACTIVITIESAND INDUCTION OF OPSONIC ANTIBODIES

The occurrence of the galactose-(alpha 1-4)-galactose-specific adhesin in Streptococcus suis, a pig and human pathogen causing sepsis, menin gitis, and other serious infections, was studied. Poly- and monoclonal antibodies to the purified adhesin, as well as pigeon ovomucoid, a sp ecific probe for the adhesin activity, detected one single protein ban d in extracts of S. suis, The adhesin was detected in all 23 strains s tudied, representing pathogenic serotypes (1, 2, 4, 5, 7, 8, and nonty peable) and including several weakly hemagglutinating or nonhemaggluti nating strains and phase variants. The amount of adhesin detected was not correlated with the hemagglutination activity of the intact bacter ia. Extraction of cells showing no binding of pigeon ovomucoid by ultr asonic treatment resulted in extracts with pigeon ovomucoid binding ac tivity, suggesting that the adhesin was not accessible to the probe on the intact cells, Analysis of the amount of capsular polysaccharide r evealed an inverse relationship between the hemagglutination activity and expression of capsular polysaccharide, thus suggesting a factor in fluencing adhesin accessibility, The purified adhesin was highly immun ogenic and induced in preliminary experiments bactericidal activity in mice. Thus, the adhesin, with its specific binding mechanism to host cells and a proposed pathogenic role, is widely expressed among strain s of different serotypes and therefore appears to represent a novel pr omising candidate for the development of a vaccine against S. suis.