Relative Avidities of Human Immunoglobulin G Antibodies for Streptococcal Pyrogenic Exotoxins A and B

In this pilot study, we investigated the relative avidities for streptococcal pyrogenic exotoxin A (SPE-A) and SPE-B of antibodies in sera from patients with fatal streptococcal toxic shock-like syndrome and from healthy individuals and in intravenous immunoglobulin (IVIG) preparations. We observed a great variation in the relative avidities of patient, control, and IVIG immunoglobulin G (IgG) (values estimated to be between 10(−7) and 10(−11) M), with mean values for patient IgG about 10-fold lower than those of control IgG.