The repertoire of human antibodies to the carbohydrate capsule of Streptococcus pneumoniae 6B.

Antibodies to Streptococcus pneumoniae 6B capsular polysaccharide (PS) induced with a 23-valent PS vaccine among 25 adults were examined. The magnitude of antibody responses among different subjects was highly correlated with the amount of anti-6B antibodies expressing IgG (r = 0.98) and lambda (r = 0.93) isotypes. Most individuals produced one or two dominant IgG antibody clones as identified by their isoelectric points. Two antibody clones with unique amino acid sequences could be readily purified, and the sequences of their light chains match those of A1/A17 V kappa and hslv2046 V lambda genes. Anti-6B antibodies isolated from different subjects used various VL genes and differed in their cross-reactivity with 6A PS. An isoelectric focusing study suggests that some IgG antibodies induced with 6B PS bind 6A PS with lower avidity.