Differential V gene expression detected in the immune response to Streptococcus pneumoniae capsular polysaccharide between elderly and young adults.

Streptococcus pneumoniae is one of the major causative agents of respiratory infections in the elderly population. The 23-valent pneumococcal polysaccharide vaccine is recommended for use in this age group. However, research has indicated that the protective efficacy of the vaccine declines with age. Although similar levels of antibody induction are seen in both young and elderly adults, following immunization with this vaccine, recent studies have indicated that the elderly possess antibodies with lower opsonophagocytic activity and avidity than young adults. We investigated whether a shift in VH gene usage may be responsible for this observation. To this end we utilized anti-idiotypic determinants to detect VH1 and VH3 gene usage by antibodies to pneumococcal capsular polysaccharides in both young and elderly subjects by enzyme-linked immunosorbent assay (ELISA). We found no significant difference in VH3 idiotypic expression in antibody responses to capsular polysaccharide from serotype 14 (PPS14). In r...