Identification of polyclonal serum specificities with phage-display libraries.

A random hexapeptide fusion-phage library was screened to isolate phage that bound antibodies in a serum induced by hepatitis B virus surface antigen (HBsAg). Analysis of the isolated phage and comparison of their displayed peptide sequences with the primary sequence of HBsAg revealed areas where three and four amino acid matches accumulated. Differential binding studies of individual phage clones with immune and pre-immune sera identified phage carrying sequences that matched with region 117-122 of HBsAg which may represent a linear epitope or part of a larger antigenic determinant. Synthetic hexapeptides representing this region competed for binding with the matching phage clones.