Assay for antibodies to group C and G streptococcal carbohydrate by enzyme-linked immunosorbent assay.

An enzyme-linked immunosorbent technique was established for the assay of serum antibodies to the group C and G streptococcal group-specific carbohydrates. The antigens consisted of formamide-extracted purified polysaccharides conjugated to poly-L-lysine. By use of hyperimmune rabbit antisera to the streptococcal group-specific polysaccharides A, C, and G, a high degree of specificity was encountered for each of the antigens tested. Antibody titers to these antigens were then measured in sera of 100 normal individuals varying in age from newborn to 20 years. The mean titer of these antibodies increased significantly between the ages of 5 and 15 years and leveled off thereafter. Assay of antibodies to the group A, C, and G carbohydrates on sera of patients with antecedent group A streptococcal infections or rheumatic fever and their matched normal controls revealed significantly elevated titers for the antibody to streptococcal group A carbohydrate only in the sera of these patients. These results support the specificity of these tests and suggest their potential usefulness for providing evidence for infection by the various streptococcal serogroups in humans.