P64k meningococcal protein as immunological carrier for weak immunogens

Previously, the P64k meningococcal protein, an antigen of 64 kDa expressed in Escherichia coli, has been extensively characterized. We have successful ly conjugated several synthetic peptides and meningococcal group C polysacc haride to P64k. In three out of four model peptides, the murine humoral imm une response against the homologous peptide, evaluated after three doses of conjugate, was higher in the animals immunized with the coupled peptide th an in those that received free peptide. The fourth and largest was immunoge nic by itself. Similarly, the antigroup C polysaccharide levels reached by conjugated polysaccharide were significantly higher than those produced aga inst unconjugated polysaccharide. As a carrier for one of the peptides, P64 k was compared with bovine serum albumin (BSA) and tetanus toxoid (TT), bei ng able to induce slightly higher or similar antipeptide antibody levels th an these well-establish protein carriers. Our results suggest that recombin ant P64k protein could be a readily available immunological carrier, as eff icient as other commonly used large carrier molecules.