Enzyme-linked immunosorbent assay for streptococcal M protein antibodies

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Abstract
The enzyme-linked immunosorbent assay (ELISA) which uses antigen-coated tubes and enzyme-labeled [goat] anti-immunoglobulin, was used for the detection of antibodies against streptococcal M protein. The antigen used in the assay was obtained by guanidine extraction of type M-12 streptococcal cell walls followed by hydroxyapatite chromatography. This antigen has the capacity to elicit bactericidal antibodies in rabbits. The ELISA is specific and highly sensitive for the detection of antibodies in rabbit and human antisera. When M-12 antigen is used, the antibodies detected by ELISA are apparently the same antibodies detected in the bactericidal test. There was a 96% agreement between bactericidal and ELISA results with rabbit sera and 97.5% agreement with human sera. All bactericidal antibody-positive sera tested thus far yielded positive ELISA results.