title: Impact of IgM Antibodies on Cross-Protection against Pneumococcal Serogroups 6 and 19 after Immunization with 7-Valent Pneumococcal Conjugate Vaccine in Children.
abstract: Although it is well known that pneumococcal conjugate vaccines provide cross-protection against some vaccine-related serotypes, these mechanisms are still unclear. This study was performed to investigate the role of cross-protective IgM antibodies against vaccine-related serotypes 6A, 6C, and 19A induced in children aged 12-23 months after immunization with 7-valent pneumococcal conjugate vaccine (PCV7). We obtained serum samples from 18 Korean children aged 12-23 months after a PCV7 booster immunization. The serum IgG and IgM concentrations of serotypes 6B and 19F were measured by enzyme-linked immunosorbent assay (ELISA) in serum. The opsonic indices (OIs) against vaccine serotypes 6B and 19F and vaccine-related serotypes 6A, 6C, and 19A were determined by an opsonophagocytic killing assay (OPA) in IgM-depleted and control serum. Both IgG and IgM antibodies in ELISA and opsonic indices in OPA against serotypes 6B and 19F were demonstrated in the immune serum. IgM depletion decreased the OIs against vaccine serotypes 6B (geometric means of OIs (GMIs) of 3,009 vs. 1,396, 38% reduction) and 19F (1,117 vs. 750, 36% reduction). In addition, IgM depletion markedly decreased the OIs against vaccine-related serotypes 6A (GMIs of 961 vs. 329, 70% reduction), 6C (432 vs. 185, 72% reduction), and 19A (301 vs. 166, 58% reduction). The booster immunization PCV7 induced protective antibodies in the form of both IgG and IgM isotypes. IgM antibodies contributed to eliciting cross-protection against vaccine-related serotypes as well as against vaccine serotypes.
authors.affiliation: Center for Vaccine Evaluation and Study, Medical Research Institute, Ewha Womans University School of Medicine, Seoul, Korea.; Department of Pediatrics, Graduate School of Medicine, Gachon University, Incheon, Korea.
authors.forename: Hye-Kyung
authors.identifier: 0000-0003-0990-1350
authors.initials: HK
authors.lastname: Cho
authors.affiliation: Center for Vaccine Evaluation and Study, Medical Research Institute, Ewha Womans University School of Medicine, Seoul, Korea .
authors.forename: In Ho
authors.identifier: 0000-0003-2190-5469
authors.initials: IH
authors.lastname: Park
authors.affiliation: Departments of Pathology and Microbiology, University of Alabama at Birmingham, Birmingham, AL, USA .
authors.forename: Robert L
authors.initials: RL
authors.lastname: Burton
authors.affiliation: Center for Vaccine Evaluation and Study, Medical Research Institute, Ewha Womans University School of Medicine, Seoul, Korea.; Department of Pediatrics, Ewha Womans University School of Medicine, Seoul, Korea.
authors.forename: Kyung-Hyo
authors.identifier: 0000-0002-0333-6808
authors.initials: KH
authors.lastname: Kim
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood; D057134:Antibodies, Neutralizing / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay; D000069443:Heptavalent Pneumococcal Conjugate Vaccine / Q000276:immunology*; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood*; D007223:Infant; D011008:Pneumococcal Infections / Q000517:prevention & control*; D022242:Pneumococcal Vaccines / Q000276:immunology*; D065288:Serogroup; D013296:Streptococcus pneumoniae / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D057134:Antibodies, Neutralizing; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D007075:Immunoglobulin M; D022242:Pneumococcal Vaccines
keywords: Heptavalent Pneumococcal Conjugate Vaccine; Immunoglobulin M; Pneumococcal Polysaccharide Type 19; Pneumococcal Polysaccharide Type 6; Streptococcus pneumoniae