Detection of type-specific pneumococcal antigens by counterimmunoelectrophoresis. I. Methodology and immunologic properties of pneumococcal antigens.

Abstract

Abstract Optimal conditions were determined for detection of purified pneumococcal polysaccharides (PPP) by a rapid immunoprecipitin method, counterimmunoelectrophoresis (CIE). With commercially available pneumococcal antisera, as little as 0.05 μg per milliliter of PPP types 1, 3, 4, 8, 12, and 23 could be detected but the method was less sensitive for PPP types 7 and 14. PPP in urine could be concentrated 20-fold by ethanol precipitation and as little as 0.0025 μg per milliliter of antigen detected. Type specificity of PPP was readily determined by CIE and no cross-reactions were observed with human blood group substances or suspensions of a variety of bacteria (10 8 organisms per milliliter). Pneumococcal capsular antigen (PCA) in serum and pleural fluid from a case of pneumonia had the same reactivity in the CIE test as PPP and gave reactions of complete identity with PPP in double-diffusion tests. PCA in urine did not precipitate readily with low titered antisera during CIE but was detected as readily as PPP when high titered antisera were employed. Double-diffusion tests demonstrated partial identity between urine PCA and PPP indicating that the urine PCA was partially degraded.