Antibody response to pneumococcal capsular polysaccharides in children with acute otitis media.

BACKGROUND: To describe the antibody response to pneumococcal capsular polysaccharides in children <2 years of age with pneumococcal acute otitis media (AOM) caused by serotypes 6A, 6B, 11A, 14, 19F or 23F. These serotypes were commonly found in both nasopharyngeal carriage and AOM in children of the study population in Finland. METHODS: Serum antibody concentrations to pneumococcal capsular polysaccharides of types 6B, 11A, 14, 19F and 23F were measured by enzyme immunoassay in acute and convalescent sera from children with AOM. RESULTS: Responses (at least 2-fold increase of antibody concentration) were relatively infrequent and varied with both the age of the child and the serotype of the Streptococcus pneumoniae isolated from the middle ear fluid. Children older than 12 months were more likely to have antibody responses than were younger children. Responses were seen only infrequently to types 6A, 6B or 19F (1 of 14, 1 of 9 and 2 of 25, respectively), more often to types 11A and 14 (2 of 8 and 3 of 8) and relatively frequently to type 23F (8 of 18). However, the convalescent antibody concentrations to type 23F were low and usually declined after the infection, whereas responders to 14 AOM had antibodies that persisted at a high concentration through the follow-up. CONCLUSIONS: The results emphasize the differences between Streptococcus pneumoniae serotypes in their immunogenicity and quantitative and qualitative differences of antibodies produced after infection.

Immunogenicity and reactogenicity of 23-valent pneumococcal polysaccharide vaccine among pregnant Filipino women and placental transfer of antibodies.

This randomized, controlled study among pregnant women evaluated the prevaccination distribution of anti-pneumococcal (Pnc) antibodies (Ab), the immunogenicity and reactogenicity of Pnc polysaccharide vaccine, and transplacental transfer of Ab. The Pnc vaccine group (N=106) received Pnc PS vaccine, Hemophilus influenzae type b conjugate vaccine and tetanus toxoid; the control group (N=54) received tetanus toxoid only. Sera and cord blood were assayed for anti-pnc Ab using enzyme immunoassay. In the Pnc vaccine group, anti-Pnc Ab rose by 3- to 9-fold and was significantly higher in cord blood. In evaluating Pnc conjugate vaccines, the concentration of 0.35 microg/ml is suggested as the protective threshold against invasive disease. Around 90% of mothers had this level pre-vaccination. Considering the decay of passively acquired Ab and the growth of the infant, an Ab level in cord blood of at least 4.4 microg/ml is needed if infants are to be protected up to 4 months of age. Cord blood anti-Pnc Ab was above this level in 60% and 10% of the Pnc vaccine and control groups, respectively. Maternal immunization with Pnc polysaccharide vaccine can provide prolonged protection through passively acquired Ab.