Detection of alpha S1-casein in vomit from bottle-fed babies by enzyme-linked immunosorbent assay

This study describes a sensitive enzyme-linked immunosorbent assay (ELISA) using rabbit anti-bovine alpha S1-casein antibody for the detection of commercial milk and milk-containing vomit. The antibody does not react with other human body fluids such as breast milk. The stability of alpha S1-casein antigenic activity was examined after storage at different temperatures and enzyme digestion. There was no decrease after storage for one year at room temperature but 40% of the activity was lost after 6 months at 37 degrees C. Enzyme digestion (6 hours, 37 degrees C) resulted in 65 approximately 70% loss of activity but the antibody reacted with the peptide fragments of alpha S1-casein. Vomit samples from 3 normal infants were tested by ELISA, and alpha S1-casein could be detected in 1 cm2 stain.