Crystal structure of suboptimal viral fragments of Epstein Barr Virus Rta peptide-HLA complex that stimulate CD8 T cell response

• Published in: Scientific reports Vol. 9; no. 1; pp. 16660 - 10
• Main Authors: Huan, Xuelu, Zhuo, Ziyi, Xiao, Ziwei, Ren, Ee Chee
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 13.11.2019; Nature Publishing Group UK
• Subjects: Amino acids; CD8 antigen; CD8-Positive T-Lymphocytes - immunology; Conformation; Crystal structure; Crystals; Epitopes; Epitopes, T-Lymphocyte - chemistry; Epitopes, T-Lymphocyte - immunology; Epstein-Barr virus; Epstein-Barr Virus Infections - immunology; Epstein-Barr Virus Infections - virology; Herpesvirus 4, Human - immunology; Histocompatibility antigen HLA; HLA-A Antigens - chemistry; HLA-A Antigens - immunology; Humans; Immediate-Early Proteins - chemistry; Immediate-Early Proteins - immunology; Immunodominance; Leukocytes (mononuclear); Leukocytes, Mononuclear - immunology; Leukocytes, Mononuclear - virology; Lymphocytes T; Major histocompatibility complex; Peptide Fragments - chemistry; Peptide Fragments - immunology; Peptides; Peripheral blood mononuclear cells; Proteasomes; Protein Conformation; T cell receptors; T-Lymphocytes, Cytotoxic - immunology; Trans-Activators - chemistry; Trans-Activators - immunology; β2 Microglobulin
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-53201-6

Peptides presented by Human leukocyte antigen (HLA) class-I molecules are generally 8-10 amino acids in length. However, the predominant pool of peptide fragments generated by proteasomes is less than 8 amino acids in length. Using the Epstein - Barr virus (EBV) Rta-epitope (ATIGTAMYK, residues 134-142) restricted by HLA-A*11:01 which generates a strong immunodominant response, we investigated the minimum length of a viral peptide that can constitute a viral epitope recognition by CD8 T cells. The results showed that Peripheral blood mononuclear cells (PBMCs) from healthy donors can be stimulated by a viral peptide fragment as short as 4-mer (AMYK), together with a 5-mer (ATIGT) to recapitulate the full length EBV Rta epitope. This was confirmed by generating crystals of the tetra-complex (2 peptides, HLA and β2-microglobulin). The solved crystal structure of HLA-A*11:01 in complex with these two short peptides revealed that they can bind in the same orientation similar to parental peptide (9-mer) and the free ends of two short peptides acquires a bulged conformation that is directed towards the T cell receptor. Our data shows that suboptimal length of 4-mer and 5-mer peptides can complement each other to form a stable peptide-MHC (pMHC) complex.