An influenza hemagglutinin A peptide assay based on the enzyme-multiplied immunoassay technique.

A practical approach for constructing enzyme-multiplied immunoassay technique (EMIT)-based protein/peptide assays is described. Normally used in small-molecule drug testing, EMIT is a homogeneous assay method that is attractive for its simplicity, sensitivity, and rapidity. The EMIT-based peptide/protein assay was developed by conjugating a cysteine-modified HA peptide (from influenza hemagglutinin A) to the reporter enzyme, glucose-6-phosphate dehydrogenase. The 13-min assay gave a free HA limit of detection of 10 nM and proved effective for detection of a high-molecular-weight model protein tagged with HA. Similar EMIT-based assay approaches may be developed for applications in biotoxin and infectious disease detection.