Nonneutralizing antibody to erythrogenic toxin A alpha(NY5ETA) in human sera

A solid phase adsorption experiment was performed to detect anti-ETA alpha(NY5 strain ETA) nonneutralizing antibody. Toxin was applied to the Protein A-Sepharose column retaining IgG bound after pretreatment with test serum. Mitogenic activity recovered in the effluent and in the eluate containing the IgG was measured separately in rabbit lymphocyte culture. A significantly increased recovery in the eluate was found in combination with decreased recovery in the effluent of three sera from Kawasaki disease and one from Streptococcus pyogenes infection among 13 ELISA-positive, antimitogen assay (AMA)-negative sera tested. The nonneutralizing antibody may play an important role in the immune protection against ETA by binding to nonmitogenic epitope(s) on ETA and enabling to handle the toxin not as a superantigen but as a conventional peptide antigen.