title: Low opsonic activity to the infecting serotype in pediatric patients with invasive pneumococcal disease.
abstract: Serotype-specific protective immunity in pediatric patients with invasive pneumococcal disease (IPD) has not been fully investigated. To determine the protective immunity to the infecting serotype, the serotype-specific immunoglobulin G (IgG) levels and opsonization indices (OIs) were examined in 24 Japanese pediatric patients whose serum was collected within one month of an IPD episode between May 2008 and June 2011. The median age (range) of IPD patients was 17 (10-108) months and 63% were boys. In all 17 patients tested, the levels of serotype-specific IgG to the infecting serotype were higher than 0.2 μg/ml, but the OIs to the infecting serotype were <8. The avidities of 19F- or 6B-specific IgG in patients with levels higher than 5.0 μg/ml, but with undetectable OIs, were confirmed to be lower than those in patients with high OIs. Our data demonstrated that although the levels of serotype-specific IgG to the infecting serotype were higher than 0.2 μg/ml in sera of pediatric patients with IPD, the OIs were low one month after the IPD episode. Low opsonic activities in these patients may, in part, be explained by the low avidity of serotype-specific IgG.
authors.affiliation: Department of Pediatrics, Niigata University Medical and Dental Hospital, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Oishi
authors.forename: Naruhiko
authors.initials: N
authors.lastname: Ishiwada
authors.forename: Kousaku
authors.initials: K
authors.lastname: Matsubara
authors.forename: Junichiro
authors.initials: J
authors.lastname: Nishi
authors.forename: Bin
authors.initials: B
authors.lastname: Chang
authors.forename: Kazuyo
authors.initials: K
authors.lastname: Tamura
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Akeda
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Ihara
authors.forename: Moon H
authors.initials: MH
authors.lastname: Nahm
authors.forename: Kazunori
authors.initials: K
authors.lastname: Oishi
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood*; D000915:Antibody Affinity; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007223:Infant; D008297:Male; D009895:Opsonin Proteins / Q000097:blood*; D011008:Pneumococcal Infections / Q000276:immunology*; D013296:Streptococcus pneumoniae / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D009895:Opsonin Proteins