title: Immune responses of infants vaccinated with serotype 6B pneumococcal polysaccharide conjugated with tetanus toxoid.
abstract: BACKGROUND
  Streptococcus pneumoniae is a major cause of meningitis, bacteremia, pneumonia and otitis media. Pneumococcal polysaccharides are not immunogenic in infants, but improved immunogenicity of polysaccharide-protein conjugates has been demonstrated. Antibiotic-resistant pneumococci have increased the need for an effective vaccine.
  
  
  OBJECTIVE
  To study the safety and immunogenicity of a pneumococcal type 6B polysaccharidetetanus toxoid conjugate (Pn6B-TT) in infants and to assess the function of antibodies.
  
  
  METHODS
  Healthy infants were injected, Group A at 3, 4 and 6 months (n = 21) and Group B at 7 and 9 months (n = 19). Booster injection was given at 18 months. Antibodies were measured by enzyme-linked immunosorbent assay and radioimmunoassay, and functional activity was measured by opsonization of radiolabeled pneumococci. Nasopharyngeal cultures were obtained.
  
  
  RESULTS
  No significant adverse reactions were observed. Pn6B-IgG (enzyme-linked immunosorbent assay) increased to a geometric mean of 0.62 microgram/ml (P = 0.367, compared with prevaccination titers) in Group A at 7 months and 1.22 micrograms/ml (P < 0.001) in Group B at 10 months. Total Pn6B antibodies (radioimmunoassay) were 44 ng of antibody N/ml (P < 0.053) in Group A and 211 ng of antibody N/ml (P < 0.001) in Group B. A smaller increase in IgM and IgA anti-Pn6B was observed. Reinjection at 18 months elicited booster responses in total and IgG anti-Pn6B; 62% of those in Group A and 79% of those in Group B had > 300 ng of antibody N/ml. Opsonic activity, after initial and booster vaccinations, correlated with Pn6B-antibody titers. Three infants with nasopharyngeal cultures repeatedly positive for serogroup 6 had poor serum IgG responses.
  
  
  CONCLUSIONS
  Our results demonstrate that Pn6B-TT is safe, elicits functional antibodies and memory responses in infants.
authors.affiliation: Department of Immunology, National University Hospital, Reykjavik, Iceland.
authors.forename: S T
authors.initials: ST
authors.lastname: Sigurdardottir
authors.forename: G
authors.initials: G
authors.lastname: Vidarsson
authors.forename: T
authors.initials: T
authors.lastname: Gudnason
authors.forename: S
authors.initials: S
authors.lastname: Kjartansson
authors.forename: K G
authors.initials: KG
authors.lastname: Kristinsson
authors.forename: S
authors.initials: S
authors.lastname: Jonsson
authors.forename: H
authors.initials: H
authors.lastname: Valdimarsson
authors.forename: G
authors.initials: G
authors.lastname: Schiffman
authors.forename: R
authors.initials: R
authors.lastname: Schneerson
authors.forename: I
authors.initials: I
authors.lastname: Jonsdottir
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood / Q000276:immunology; D005260:Female; D006801:Humans; D007071:Immunoglobulin A, Secretory / Q000032:analysis; D007223:Infant; D008297:Male; D009305:Nasopharynx / Q000382:microbiology; D010587:Phagocytosis; D011135:Polysaccharides, Bacterial / Q000009:adverse effects / Q000276:immunology*; D012463:Saliva / Q000276:immunology; D013296:Streptococcus pneumoniae / Q000302:isolation & purification; D013745:Tetanus Toxoid / Q000009:adverse effects / Q000276:immunology*; D014611:Vaccination; D018074:Vaccines, Conjugate / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D007071:Immunoglobulin A, Secretory; D011135:Polysaccharides, Bacterial; D013745:Tetanus Toxoid; D018074:Vaccines, Conjugate; C092872:streptococcal polysaccharide-tetanus toxoid conjugate vaccine