Monoclonal antibody-based enzyme-linked immunosorbent assay for C19-delta 16-steroids in sera of boar pigs

A monoclonal antibody was prepared against 5 alpha-androst-16-en-3-one, the major steroid compound responsible for the urine-like odor in the adipose tissue of uncastrated male pigs, and incorporated into a sensitive competitive indirect enzyme-linked immunosorbent assay (ELISA). The limit of detection for 5 alpha-androst-16-en-3-one in the ELISA was 0.05 ng/mL (2.5 pg/assay). Cross-reactivities in the ELISA, measured as concentration (ng/mL) required to inhibit 50% binding of antibody to a 5 alpha-androst-16-en-3-one-ovalbumin conjugate solid phase, were 3.2, 7.2, and 1.3 for 5 alpha-androst-16-en-3-one, 5 alpha-androst-16-en-3-alpha-ol, and 5 alpha-androst-16-en-30-ol, respectively. The latter two compounds, which also contribute to boar odor, thus exhibited 44% and 246% cross-reactivity relative to the parent compound. The assay was used directly for detection of the boar odor steroids in plasma and serum after appropriate dilutions without extraction. This rapid and sensitive monoclonal antibody-based ELISA should be readily applicable for the routine screening of pigs for boar odor on the assumption that a relationship exists between the concentration of the responsible odorous compounds in the blood and fatty tissues