Serum antibody responses of weanling mice and two-year-old children to pneumococcal type 6A protein conjugate vaccines of differing saccharide chain lengths

Type 6A pneumococcal polysaccharide (PS) fractions having mean lengths 2, 7, or 14 repeat units were coupled to tetanus toroid, giving conjugates T-6A-2, T-6A-7 or T-6A-14. In weanling outbred mice, type-6A serum antibody responses were minimal to T-6A-7 bur significantly higher to T-6A-2 and T-6A-14 In contrast, two-year-old humans responded increasingly to T-6A-2, T-6A-7, and T-6A-14; type 6B antibody rose, but variably Upon challenge with 6B PS at age 3yr; conjugate-primed children made anamnestic responses. T-6A-14, containing the longest saccharide chains (and highest saccharide:protein mass ratio) excelled in priming as well as antibody induction, (C) 1997 Elsevier Science Ltd.