IMMUNOGENICITY OF STREPTOCOCCUS-PNEUMONIAE TYPE-6B AND TYPE-14 POLYSACCHARIDE-TETANUS TOXOID CONJUGATES AND THE EFFECT OF UNCOUPLED POLYSACCHARIDE ON THE ANTIGEN-SPECIFIC IMMUNE-RESPONSE

The immunogenicity of two types of Streptococcus pneumoniae capsular p olysaccharide-tetanus toroid conjugates (PS6BTT and PS14TT) was evalua ted in mice. Both conjugates induced high titres of high avidity type- specific anti-PS Igc, which include all IgG isotypes except IgG2a, Rep ented immunization resulted in booster responses in both cases. The an tibodies induced exhibited opsonic activity, as measured in an in vitr o opsonophagocytosis assay, using the mouse macrophage cell line RAW-2 64, Furthermore, the influence of spiking PS6BTT with free PS6B of eit her 1000 kDa (native) or 37kDa was investigated The results indicate t hat not only the amount but also the molecular weight of the free PS6B present in the conjugate vaccine affect the anti-PS6B immune response , Lar ge amounts of free PS6B of both molecular weights decrease each anti-PS6B IgG isotype response, However; unlike admixture of the low m olecular weight PS6B, addition of the high molecular weight PS6B leads to a rather persistent state of unresponsiveness. (C) 1998 Elsevier S cience Ltd, All rights reserved.