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 V(H) gene usage may be responsible for this observation. To this end we utilized anti-idiotypic determinants to detect V(H)1 and V(H)3 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 V(H)3 idiotypic expression in antibody responses to capsular polysaccharide from serotype 14 (PPS14). In response to PPS14 a significant higher level of V(H)1 idiotypic expressing antibodies was detected in the elderly as compared with young adults. V(H)1 idiotypic expression in response to capsular polysaccharide from serotype 4 (PPS4) was identical in young and elderly individuals. V(H)3 idiotypic expression in the elderly response to PPS4 was significantly lower than that seen in young individuals. These patterns of idiotypic expression are discussed in relation to recent studies of functional activity of pneumococcal reactive antibodies from young and aged humans.