Functional Immunity to Cross-Reactive Serotype 6A Induced by Serotype 6B in Pneumococcal Polysaccharide Vaccine / 소아과

PURPOSE: Streptococcus pneumoniae serotype 6B and 6A are important pathogens in pneumococcal infections. It is commonly assumed that the 6B vaccines elicit antibodies cross-reacting with the 6A serotype and the cross-reactive antibodies protect against infections of 6A. To examine this assumption, we measured the opsonophagocytic capacity to serotype 6A and 6B in adults. METHODS: Twenty-four adults were immunized with pneumococcal PS vaccine that contains 6B PS. Their preimmune and postimmune sera were studied for the capacity to opsonize 6B and 6A serotypes with opsonophagocytic killing assay. RESULTS: Opsonization titers to 6B were significantly higher than those to 6A in preimmune and postimmune sera. Because significant increasesof opsonization titers were observed in adults with polysaccharide vaccines for 6A(cross-reactive) serotype as well as for 6B(vaccine) serotype, 6B PS in vaccine elicited cross-protective antibodies to 6A, but not in all cases. One adult did not have detectable levels of opsonization titers to 6A after immunization. CONCLUSION: Although 6B PS in pneumococcal PS vaccine elicits antibodies cross-reacting with 6A serotype in some adults, it may not occur always. This study should be extended to other age groups such as children and elderly people. The presence of the cross-protection should be directly determined in clinical trials of the pneumococcal vaccines as well as during the postlicensure monitoring surveys by serotyping the clinical isolates of pneumococci.

Functional Antibody Responses to Seven Serotypes in Pneumococcal Polysaccharide Vaccine in Children / 소아과

PURPOSE: Streptococcus pneumoniae is an important pathogen in children as well as in elderly people. The aim of this study was to assess the opsonization activity of pneumococal capsular antibody to seven serotypes in 23-valent pneumococcal polysaccharide vaccine before and after immunization in Korean children. METHODS: Nine children from 24 to 49 months of age were immunized with 23-valent polysaccha ride pneumococcal vaccine in Ewha Woman's University Tongdaemoon Hospital. From them, sera were collected before immunization as well as 1 month after immunization. Double-serotype opsono phagocytic killing assay was performed against seven serotypes(4, 6B, 9V, 14, 18C, 19F and 23F) of S. pneumoniae to get opsonization titer of these sera using dimethyl formamide differentiated HL-60 cells. RESULTS: After immunization, geometric mean opsonization titer of sera against serotype 18C(4,352) was the highest followed by serotype 9V(3,317), serotype 14(1,545), serotype 4(1,359). The opsonization titer against serotype 23F(342) was the lowest followed by serotype 19F(525), and serotype 6B (809). Fold increases of opsonization titer were higher against serotype 4(339.8), 9V(65.7), 19F(34.5), and 14(18.8) than those against serotype 23F(4.5), 6B(8.9), and 18C(9.9). CONCLUSION: The opsonization titers of postimmune sera against seven serotypes of S. pneumoniae were increased in many(not all) preschool children. But they showed variable values of opsonization titer in postimmune sera as well as in preimmune sera against different serotypes. The immune responses to pneumococcal polysaccharide in preschool children are not maturated sufficiently yet.

Evaluation of antibody responses to pneumococcal vaccines with ELISA and opsonophagocytic assay

Antibodies to a capsular polysaccharide (PS) provide protection against Streptococcus pneumoniae which express the homologous capsular serotype, and pneumococcal vaccines are designed to induce antibodies in the capsular PS. Levels and opsonophagocytic capacity of antibodies to the capsular PS of S. pneumoniae serotype 19F were determined by sera from adults immunized with 23-valent S. pneumoniae capsular PS vaccines. Geometric means of IgG anti-19F antibody level and specific opsonic titer rise significantly after immunization. The level of anticapsular PS antibodies for S. pneumoniae 19F serotype is fairly well correlated (r2=O.63) with the opsonophagocytic activities of sera. However, 3.7% (1/27) of serum samples display strikingly less opsonophagocytic activity than expected on the basis of their antibody level. Thus, antibody level may be of general use in predicting vaccine-induced protection among adults for 19F serotype. However, the opsonic activity data suggest that antibody levels are not always indicative of functional antibody.