Characterization of the Structure and Immunogenicity of HN654-662 and Variant Peptides Bound to HLA-A2.1
Abstract
We propose to establish an approach by which tumor cells are eradicated through selective induction of CD8+ specific for a cellular protein that is expressed in many breast and ovarian cancers. Our model system is the class I MHC molecule HLA-A2. 1 and the HER-2/neu protein. HLA-A2. 1 is present in approximately 50% of Caucasians and African-Americans, and HER-2/neu is overexpressed in approximately 30% of adenocarcinomas including breast cancer. A peptide derived from HER-2/neu (HN654- 662) has been shown to bind HLA-A2. 1 and stimulate cytotoxic T lymphocytes (CTL) that lyse primary tumors from breast or ovarian cancer. The peptide has poor immunogenicity due to poor binding to HLA-A2.1 (Tm 36.6 C). We are trying to improve the binding affinity by making substitution in the peptide sequence to make it effective therapeutic agent. The crystallographic structure of HN654-662 co-crystallized with HLA-A2. 1 shows that the center of the peptide does not assume one specific conformation and does not make stabilizing contacts with the peptide binding cleft.. The altering of the primary anchor residues did not improve the binding significantly. Out of many variants, only V5L, is relatively more stable with higher Tm (Tm-45.8 C). The crystallographic studies of HLA-A2. 1 plus HN654-662 variant (12L/V5L/L9V) shows that substituted Leu at fifth position point away from the MHC molecule. It seem that substitution of anchor residues:makes Leu to point away. We expect that in V5L variant, the substituted Leu will make stabilizing contacts.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1999
- Accession Number
- ADA385908
Entities
People
- Ashwani K. Sharma
- Edward Collins
Organizations
- University of North Carolina at Chapel Hill