A modified enzyme-linked immunosorbent assay for measuring type-specific anti-pneumococcal capsular polysaccharide antibodies

Association between Serotype-Specific Antibody Response and Serotype Characteristics in Patients with Pneumococcal Pneumonia, with Special Reference to Degree of Encapsulation and Invasive Potential

“…However, naturally acquired antibodies may lack in functionality, which might explain why such antibodies appear to lack in protection against disease (30). In the evaluations of the ELISA used in the present study (21,23), the median Ig titer (geometric mean [GM] Ig titer to serotypes 1, 4, 7F, 14, 18C, and 19F) in 15 healthy individuals prior to vaccination was 32 AU (range, 8 to 61 AU), and 4 weeks after vaccination with the PPV23, the median Ig titer was 63 AU (range, 20 to 113 AU). In the present study of patients with pneumococcal pneumonia, we observed a median acute Ig titer of 36 AU, similar to that of the nonvaccinated population in the evaluation study, and a median convalescent titer of 84 AU after 4 weeks ( Table 2).…”

“…In the present study of patients with pneumococcal pneumonia, we observed a median acute Ig titer of 36 AU, similar to that of the nonvaccinated population in the evaluation study, and a median convalescent titer of 84 AU after 4 weeks ( Table 2). The WHO Collaborating Center for Reference and Research on Pneumococci at the SSI (Copenhagen, Denmark) previously used this ELISA for an evaluation of vaccine effectiveness and as a guide for pneumococcal revaccination (21,23). Revaccination was recommended if the GM titer was Ͻ25 AU or Ͻ40 AU, with more than one of the six type-specific antibody levels being Ͻ25 AU.…”

“…At the time of this study, the World Health Organization (WHO) consensus guidance protocol for using the ELISA to test the immune response to pneumococcal CPS, measured in g/ml, was not yet established (20)(21)(22). Instead, we used the ELISA described and evaluated by Konradsen (21) and Konradsen, Sørensen, and Henrichsen (23). As in the WHO ELISA, the American Type Culture Collection (ATCC) polysaccharides were used for coating, and all sera were adsorbed by adding cell wall polysaccharides (CWPS) to inhibit nonspecific binding (23,24).…”

“…Instead, we used the ELISA described and evaluated by Konradsen (21) and Konradsen, Sørensen, and Henrichsen (23). As in the WHO ELISA, the American Type Culture Collection (ATCC) polysaccharides were used for coating, and all sera were adsorbed by adding cell wall polysaccharides (CWPS) to inhibit nonspecific binding (23,24). A pool of postvaccination serum samples from 43 healthy adults, who had been vaccinated with a 23-valent pneumococcal polysaccharide vaccine (Pneumovax 23 [PPV23]), was used as standard serum.…”

“…The optical densities at 490 nm were measured using an automatic ELISA reader (Sunrise; Tecan Schweiz AG, Switzerland). By comparing the optical density (OD) data from the dilution series of the patient serum with those of the standard serum, an antibody titer in arbitrary units (AU) was calculated for the patient serum (21,23). On each plate, the OD of the substrate was measured in blank wells, without antigen or serum, with OD ϫ1,000 values of Ͻ100 AU.…”