Functional differences in IgG anti-polysaccharide antibodies elicited by immunization of mice with C3d versus ovalbumin conjugates of pneumococcal serotype 14 capsular polysaccharide.
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.
Hu
Yong
Y
Children's Hospital Oakland Research Institute, 5700 Martin Luther King, Jr. Way, Oakland, CA 94609-1673, USA.
Test
Samuel T
ST
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*
D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D018074:Vaccines, Conjugate; C056696:pneumococcal polysaccharide, type 14; D015933:Complement C3d; D010047:Ovalbumin