Comparing tandem repeats and multiple antigenic peptides as the antigens to detect antibodies by enzyme immunoassay.

Short synthetic peptides are useful alternatives to whole lysate or recombinant proteins as the antigens used for serodiagnosis of bacterial or viral infections. However, certain known antigenic peptides displayed low seroreactivities in direct enzyme immunoassay. This was believed to be due to the low coating efficiency, a constrained orientation, or loss of flexibility required for optimal antibody binding. Using a model peptide system derived from the V3-loop of HIV-1 gp120, we demonstrated that low antigenicity could be overcome by using either tandem repeats (TR) or multiple antigenic peptides (MAPs) which contained the same amino acid sequence as the monomeric peptide. In our model system, a four-branch MAP was a better choice compared to the tandem repeats because of the MAP's slightly higher sensitivity and lower cost of production.