Serum and salivary anti-capsular antibodies in infants and children immunized with the heptavalent pneumococcal conjugate vaccine

Aim. To study the ability of seven-valent experimental pneumococcal polysac charide CRM,,, protein conjugate vaccine (PncCRM) to induce antibodies in s erum and saliva of infants. Methods. Sixty Finnish infants received PncCRM vaccine at 2, 4 and 6 months of age and were boosted with PncCRM (n = 30) or pneumococcal polysaccharid e (PncPS) (n = 29) vaccine at the age of 15 months. Serum IgG antibody conc entrations to vaccine serotypes 4, 6B, 9V, 14, 18C, 19F and 23F were measur ed by enzyme immunoassay at 2, 4, 6, 7, 15, 16 and 24 months of age. Saliva ry IgA, IgG and secretory Ig antibody titers at 7 and 16 months of ages wer e analyzed by enzyme immunoassay against the same serotypes, except 23F. Results. PncCRM induced systemic immune responses and immunologic memory. A t 7 months of age 69 to 100% of children, depending on the serotype, had se rum IgG antibody concentrations exceeding the value of 1.0 mug/ml. At 15 mo nths the titers were still higher than before the vaccinations. Booster dos es of either PncPS or PncCRM induced an increase in antibody concentrations . The titers were still elevated at 24 months of age. Salivary IgA and IgG antibodies were found rarely at 7 months of age, but in up to 80% of sample s taken at 16 months of age, depending on the serotype and nature of the bo oster vaccine. Salivary IgG correlated with IgG in serum, supporting the th eory that salivary IgG is derived from serum. Salivary IgA and secretory Ig correlated positively, which indicates that IgA was locally produced. Conclusions. PncCRM induces both systemic and mucosal immune responses in i nfants.