Bridge-heterologous chemiluminescence enzyme-linked immunosorbent assay of estriol 3-sulfate in pregnancy plasma.

A facile and sensitive chemiluminescence enzyme-linked immunosorbent assay (ELISA) of estriol 3-sulfate using a bridge-heterologous system was established. 6 alpha-Hydroxyestriol 3-sulfate 6-hemisuccinate was synthesized as a novel hapten. Antisera were raised in male guinea-pigs against 6 alpha-hydroxyestriol 3-sulfate 6-hemisuccinate-bovine serum albumin (BSA) and 6-oxoestriol 3-sulfate O-carboxymethyloxime-BSA conjugates. Both haptens were coupled to horseradish peroxidase as an enzyme-label reagent. For separation of free and estriol 3-sulfate bound to the antibody, the crude globulin fractions of these antisera were immobilized to CNBr-activated Sepharose-4B. The enzyme activity was measured by chemiluminescent reaction using amino-butylethylisoluminol and hydrogen peroxide as a substrate. The immobilized antibody raised against 6 alpha-hydroxyestriol 3-sulfate 6-hemisuccinate-BSA exhibited a high affinity and an excellent specificity for estriol 3-sulfate. The two bridge-heterologous ELISAs were more sensitive than the homologous systems. The specificity and sensitivity (10 pg) of the bridge-heterologous chemiluminescence ELISAs was comparable to those of the radioimmunoassays (RIAs). Results obtained by the ELISA and the RIA in pregnancy plasmas, showed excellent correlation between ELISA and RIA (r = 0.96).