Immunization of aged mice with a pneumococcal conjugate vaccine combined with an unmethylated CpG-containing oligodeoxynucleotide restores defective immunoglobulin G antipolysaccharide responses and specific CD4+-T-cell priming to young adult levels.
Polysaccharide (PS)-protein conjugate vaccines, in contrast to purified PS vaccines, recruit CD4+-T-cell help and restore defective PS-specific humoral immunity in the immature host. Surprisingly, in the immunocompromised, aged host, anti-PS responses to conjugate vaccines are typically no better than those elicited by purified PS vaccines. Although aging leads to defects in multiple immune cell types, diminished CD4+-T-cell helper function has recently been shown to play a dominant role. We show that in response to immunization with purified pneumococcal capsular PS serotype 14 (PPS14) in saline, the T-cell-independent immunoglobulin G (IgG) anti-PPS14 response in aged mice was comparable to that in young mice. In contrast, the T-cell-dependent IgG anti-PPS14 response to a soluble conjugate of PPS14 and pneumococcal surface protein A (PspA) (PPS14-PspA) in saline was markedly defective. This was associated with defective priming of PspA-specific CD4+ T cells. In contrast, immunization of aged mice with PPS14-PspA combined with an unmethylated CpG-containing oligodeoxynucleotide (CpG-ODN) restored IgG anti-PPS14 responses to young adult levels, which were substantially higher than those observed using purified PPS14. This was associated with enhanced PspA-specific CD4+-T-cell priming. Similarly, intact Streptococcus pneumoniae capsular type 14, which contains Toll-like receptor (TLR) ligands, also induced substantial, though modestly reduced, T-cell-dependent (TD) IgG ant-PPS14 responses in aged mice. Spleen and peritoneal cells from aged and young adult mice made comparable levels of proinflammatory cytokines in response to CpG-ODN, although cells from aged mice secreted higher levels of interleukin-10. Collectively, these data suggest that inclusion of a TLR ligand, as an adjuvant, with a conjugate vaccine can correct defective TD IgG anti-PS responses in elderly patients by augmenting CD4+-T-cell help.
Sen
Goutam
G
Department of Pathology, Uniformed Services University, 4301 Jones Bridge Road, Bethesda, MD 20814, USA.
Chen
Quanyi
Q
Snapper
Clifford M
CM
D000276:Adjuvants, Immunologic / Q000008:administration & dosage; D000375:Aging / Q000276:immunology*; D000818:Animals; D001426:Bacterial Proteins / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D018899:CpG Islands / Q000276:immunology*; D016207:Cytokines / Q000378:metabolism; D019175:DNA Methylation; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D005260:Female; D007074:Immunoglobulin G / Q000096:biosynthesis; D007075:Immunoglobulin M / Q000096:biosynthesis; D016753:Interleukin-10 / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D009838:Oligodeoxyribonucleotides / Q000008:administration & dosage / Q000276:immunology*; D022242:Pneumococcal Vaccines / Q000008:administration & dosage / Q000276:immunology*; D011134:Polysaccharides / Q000276:immunology*; D013154:Spleen / Q000166:cytology / Q000378:metabolism; D018074:Vaccines, Conjugate / Q000008:administration & dosage / Q000276:immunology; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000276:immunology*
D000276:Adjuvants, Immunologic; D001426:Bacterial Proteins; C408982:CPG-oligonucleotide; D016207:Cytokines; D018984:Epitopes, T-Lymphocyte; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D009838:Oligodeoxyribonucleotides; D022242:Pneumococcal Vaccines; D011134:Polysaccharides; D018074:Vaccines, Conjugate; D019444:Vaccines, DNA; C051592:pneumococcal surface protein A; D016753:Interleukin-10