THE BETA-CONFIGURATION OF THE RHAMNOSIDIC LINKAGE IN SALMONELLA SEROGROUPS C2 AND C3 LIPOPOLYSACCHARIDE IS IMPORTANT FOR THE IMMUNOCHEMISTRY OF THE O-ANTIGEN-8

Pairs of synthetic di- and trisaccharide-polyacrylamide (PAA) conjugat es, isomers in configuration of the rhamnose residue and related to th e sequence abequosyl-(alpha 1-3)-rhamnosyl-(beta 1-2)-mannose (ARM), f ound in Salmonella serogroUP C2 (O-antigens 6,8) and C3 (O-antigens 8, 20) lipopolysaccharides, have been used as coating antigens and inhibi tors in enzyme immunoassay to evaluate the immunochemical importance o f the beta-rhamnosidic linkage in the O-antigen 8. In each pair, the r eaction with the factor O:6,8 serum was more pronounced for the synthe tic antigen with the beta-rhamnosidic linkage. The ARM-PAA conjugate w ith the beta-rhamnosidic linkage was found to be 2000 fold more effici ent as inhibitor of binding of the factor O: 6,8 serum to the ARbetaM- PAA conjugate as compared to the alpha-linked analogue. The discrepanc y in immunochemical behaviour of the alpha and beta-rhamnose containin g ARM oligosaccharides can be explained by conformational differences of the oligosaccharides. A slight cross-reactivity observed in the int eraction of antiserum against abequosyl-(alpha 1-3)-mannose, represent ative of Salmonella O-antigen 4, coupled to BSA, with Salmonella O-fac tor 8 specific abequosyl-(alpha 1-3)-rhamnose containing conjugates is due to the common terminal immunodominant sugar, abequose.