Assay for superantigens

This chapter describes a quantitative assay for the streptococcal superantigen, streptococcal pyrogenic exotoxin A (SPEA), which can be used in broth, tissue-culture media, and certain sera. The protocol can be adapted to allow measurement of any bacterial superantigen or protein toxin, using different oligonucleotides to amplify the coding sequences from bacterial DNA. Previously, measurement of bacterial toxins such as SPEA was limited by poor test sensitivity and test samples could only be analyzed if concentrated. Techniques included Ouchterlony immunodiffusion or enzyme-linked immuno-sorbent assay (ELISA), although the lower limit of detection was 100-fold greater than that achievable in this system. (1-3) Recent methods described have achieved improved sensitivities, some using sandwich ELISA techniques, others using competitive ELISA techniques. (4-8).