Using a baculovirus display library to identify MHC class I mimotopes

We have developed a baculovirus-based display system for identifying antigen mimotopes for MHC class I-specific T cells. The mouse MHC class I molecule, D-d, was displayed on baculovirus-infected insect cells with a library of 9- and 10-mer peptides tethered via a flexible linker to the N terminus of beta2 microglobulin. As a test case,the library was screened by flow cytometry by using a multimeric fluorescent alphabetaTCR from a mouse T cell specific for D-d plus an unknown self peptide. A mimotope was identified that, when bound to D-d, stimulated the T cell to secret IL-2. The sequence of the mimotope was used to identify a self peptide present in a mouse protein, Spin. The Spin peptide, when complexed with D-d, also activated the T cell. This technique should be generally useful in identifying and manipulating MHC class I peptide mimotopes and epitopes.