IMMUNOCHEMICAL PROPERTIES OF OLIGOSACCHARIDE-PROTEIN CONJUGATES WITH KLEBSIELLA-K2 SPECIFICITY .1. SPECIFICITY AND CROSS-REACTIVITY OF ANTI-CONJUGATE VERSUS ANTI-BACTERIAL ANTIBODIES

A series of repeating unit oligomers {Mathematical expression} was prepared by depolymerization of Klebsiella pneumoniae B5055 (01:K2) capsular polysaccharide (K2-PS) as catalyzed by a bacteriophage-associated glycanase. The monomeric repeating unit [tetrasaccharide, (TS)] and its di- and trimer [octa- and dodecasaccharide (OS and DS)] were conjugated to edestin via reductive aminophenylation and azo coupling at the reducing sugar end group. Rabbit anti-conjugate and anti-bacterial antibodies raised in rabbits were compared with respect to specificity and crossreactivity towards the oligomers of the various molecular sizes, towards parent PS, and towards whole bacteria. Antibodies able to bind specifically to the PS and the bacteria were elicited by all three conjugates. However, the anti-TS conjugate antibodies, in contrast to those obtained with OS and DS conjugate, proved to be practically unable to effect bacterial agglutination. Correspondingly, the TS played an exceptional role in binding to anti-bacterial antibodies. In contrast to the OS and DS it could not fully inhibit precipitation of these antibodies with the bacterial PS. Moreover, the inhibition of the binding of the PS to antibacterial antibodies produced by TS was about 50-fold weaker than that produced by OS, DS, and higher members of the series, all of which were about equally potent inhibitors (on a molar basis). The results show that two repeating units are the minimum requirement for a substantial representation of the PS's serologic specificity. The exceptional behavior of the TS correlates with its lack of the β-Glc-(1-4)-Man linkage present in all higher members of the series. © 1979 Springer-Verlag.