Detection of antibodies to muramyl dipeptide, the adjuvant moiety of streptococcal cell wall, in patients with rheumatic fever.

The presence of antibodies to muramyl dipeptide (MDP), an adjuvant structure of streptococcal peptidoglycan, was investigated in patients with acute rheumatic fever (ARF). The detection of these antibodies was done by an enzyme-linked immunosorbent assay with a synthetic multivalent MDP conjugate as an antigen. Sera from 33 of 54 children with ARF had detectable levels of antibodies to MDP at the time of diagnosis. Such antibodies could only be detected in sera from two of 52 healthy children and one of 21 children with acute poststreptococcal glomerulonephritis. The specificity of the antibodies to MDP was demonstrated by inhibition, with free MDP, of binding of the sera to the MDP conjugate. The possible use of these antibodies in the diagnosis of ARF and in screening for safe synthetic muramyl peptides in immunization of humans is discussed.