title: B- and T-cell immune responses to pneumococcal conjugate vaccines: divergence between carrier- and polysaccharide-specific immunogenicity.
abstract: Conjugation of various serotypes of pneumococcal polysaccharide (PnPS) to carrier protein enhances the magnitude of the polysaccharide-specific antibody response, presumably by eliciting T-cell help. However, variability in PnPS serotype-specific immunogenicity has been observed. CBA/J mice immunized with either 6B or 19F PnPS conjugated to the protein carrier Cross Reactive Material(197) (CRM(197)) produce a strong anti-PnPS antibody response; however, when mice are immunized with 23F PnPS conjugated to CRM(197), they fail to produce a significant anti-PnPS response. In order to determine whether this difference was related to alterations in antigen processing of the carrier protein and the subsequent T-cell responses, we studied proliferation of lymphocytes from CBA/J mice immunized with CRM(197) alone or conjugated to 6B, 19F, or 23F PnPS. T-cell proliferative responses to synthetic peptides demonstrated that lymph node cells elicited by the poorly immunogenic conjugate 23F-CRM(197) recognized many, but not all, of the epitopes recognized by lymph node cells elicited by 6B- and 19F-CRM(197) as well as additional epitopes. Despite marked differences in PnPS-specific immunogenicity, all mice made high titers of CRM(197) antibodies of the immunoglobulin G(1) isotype. Cells from mice immunized with any of the conjugates yielded vigorous T-cell responses to whole antigen. We conclude that the serotype of PnPS can alter the peptide specificities of T-cell responses, but even a poorly immunogenic PnPS conjugate can elicit a significant T-cell response. Thus, conjugation of PnPS to a carrier protein that elicits carrier-specific T- and B-cell responses does not necessarily enhance PnPS immunogenicity.
authors.affiliation: Department of Pediatrics, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA.
authors.forename: T L
authors.initials: TL
authors.lastname: McCool
authors.forename: C V
authors.initials: CV
authors.lastname: Harding
authors.forename: N S
authors.initials: NS
authors.lastname: Greenspan
authors.forename: J R
authors.initials: JR
authors.lastname: Schreiber
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D016667:Bacterial Capsules; D001426:Bacterial Proteins / Q000276:immunology*; D001428:Bacterial Vaccines / Q000276:immunology*; D002455:Cell Division; D018985:Epitopes, B-Lymphocyte / Q000276:immunology; D005260:Female; D008198:Lymph Nodes / Q000166:cytology; D051379:Mice; D008808:Mice, Inbred CBA; D011135:Polysaccharides, Bacterial / Q000276:immunology*; D013296:Streptococcus pneumoniae / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D014611:Vaccination; D018074:Vaccines, Conjugate / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D018985:Epitopes, B-Lymphocyte; D011135:Polysaccharides, Bacterial; D018074:Vaccines, Conjugate; C116177:capsular polysaccharide 19F; C028581:CRM197 (non-toxic variant of diphtheria toxin)