Direct detection of peptide-dependent HLA variability by surface plasmon resonance

Cytotoxic T lymphocytes (CTL) recognize antigens as peptides associated with molecules of the major histocompatibility complex (MHC). The accurate characterization of antigenic peptides requires knowledge of how peptides bind to MHC molecules, and hence the conformational changes they can induce. Several reports have indicated that the conformation of the MHC class I molecule plays a role in T cell recognition. We therefore studied the interaction of a series of viral epitopes with HLA-A2, -A3, -B7 and -B8 molecules to determine how peptides could induce conformational changes in HLA molecules. This was done either directly with class I heavy chains in lysates of peptide-loading deficient T2 cells, or with purified material from B-EBV transformed cell lines. The peptide-induced HLA conformations were assessed using monoclonal anti-HLA antibodies (mAbs) and detected by surface plasmon resonance (SPR). Antigenic peptides specifically bound to the HLA molecule, even when assembly occurred in a mixed solution of HLA molecules. Distinct patterns of reactivity to a given peptide-bound class I molecule were obtained with monomorphic and allele-specific anti-HLA mAbs.