title: Functional differences in IgG anti-polysaccharide antibodies elicited by immunization of mice with C3d versus ovalbumin conjugates of pneumococcal serotype 14 capsular polysaccharide.
abstract: We previously have shown that conjugation of C3d to pneumococcal serotype type 14 capsular polysaccharide (PPS14) significantly enhances anti-PPS14 antibody production to a degree similar to that found when the T-dependent protein carrier ovalbumin (OVA) is coupled to PPS14. However, the anti-PPS14 antibody response to PPS14-C3d conjugates is characterized by less switching from IgM to IgG and lower serum concentrations of anti-PPS14 IgG after secondary immunization. To determine if these quantitative differences in anti-PPS14 IgG are accompanied by qualitative differences in the IgG anti-PPS14 antibodies, we performed several functional assays on serum IgG anti-PPS14 antibodies from mice immunized with PPS14-C3d or PPS14-OVA. Compared with antibodies elicited by immunization with PPS14-C3d, IgG anti-PPS14 antibodies produced after immunization with PPS14-OVA were found to have higher avidity and enhanced function as opsonins. Comparisons of avidity for IgG from serum samples obtained after primary and secondary immunization demonstrated a higher degree of avidity maturation after immunization with PPS14-OVA than with PPS14-C3d. These results suggest that PPS14-C3d conjugates are unlikely to be more efficacious than PPS14 conjugate vaccines incorporating T-dependent protein carriers.
authors.affiliation: Children's Hospital Oakland Research Institute, 5700 Martin Luther King, Jr. Way, Oakland, CA 94609-1673, USA.
authors.forename: Yong
authors.initials: Y
authors.lastname: Hu
authors.forename: Samuel T
authors.initials: ST
authors.lastname: Test
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D016667:Bacterial Capsules / Q000008:administration & dosage / Q000276:immunology*; D015933:Complement C3d / Q000008:administration & dosage* / Q000276:immunology; D007074:Immunoglobulin G / Q000096:biosynthesis* / Q000097:blood; D051379:Mice; D008807:Mice, Inbred BALB C; D010047:Ovalbumin / Q000008:administration & dosage / Q000276:immunology; D018074:Vaccines, Conjugate / Q000008:administration & dosage / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D018074:Vaccines, Conjugate; C056696:pneumococcal polysaccharide, type 14; D015933:Complement C3d; D010047:Ovalbumin