Dot-enzyme linked immunosorbent assay for the detection of antibodies in bovine brucellosis.

A dot-enzyme linked immunosorbent assay (dot-ELISA) for the detection of antibodies in bovine brucellosis using soluble antigens extracted from Brucella abortus S-99 is described in which antigen was deposited on a nitrocellulose sheet (0.5 x 0.5 cm) bound to a plastic strip and the unsaturated sites blocked by a solution of spray-dried milk powder. Sera were tested at dilutions of 1:800 and 1:1600, using rabbit anti-bovine-immunoglobulin or protein-A coupled to peroxidase as conjugates and diamino-benzidine as substrate. A positive reaction was clearly indicated by a brown dot on the nitrocellulose sheet. Using antigen-coated, pre-blocked strips, the test could be completed within 45 minutes.