Double Antibody Sandwich - DAS ELISA - The wells are coated with antibody (or immunoglobulins = Ig) prepared from antisera. The test sample is then added to allow trapping of virus antigen by the coated antibody in the well. This is followed by the addition of enzyme labelled antivirus Ig, which will attach to the trapped antigen.

A substrate for the enzyme is now added for producing colour reaction. Peroxidase (00 450) or alkaline phosphatase (00 405) is used, which allow quantitative measurement through a spectrophotometric device (ELISA reader with. automated. photometer is often used.