Identification of cytotoxic T cell epitopes within Epstein-Barr virus (EBV) oncogene latent membrane protein 1 (LMP1): evidence for HLA A2 supertype-restricted immune recognition of EBV-infected cells by LMP1-specific cytotoxic T lymphocytes

Abstract

Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA1) and latent membrane proteins (LMP) are the only antigens consistently expressed in malignancies such as nasopharyngeal carcinoma (NPC) and Hodgkin's disease (HD). Since EBNA1 is not recognized by EBV-specific cytotoxic T lymphocytes (CTL), there is increasing interest in the identification of the potential target epitopes within LMP1. Although LMP1-specific CTL have been isolated from seropositive individuals, earlier attempts to identify the peptide epitopes recognized by these T cells have been unsuccessful. In the present report we used a novel protocol to identify CTL epitopes within LMP1 which can be recognized by both polyclonal and clonal CTL. Firstly, a computer-based program was employed to identify the potential HLA-binding peptides within LMP1. Polyclonal CD8+ CTL were then isolated from seropositive donors that recognized the peptide epitopes YLLEMLWRL and YLQQNWWTL from LMP1 in association with HLA A2. Limiting dilution analysis of the memory CTL response revealed that the LMP1-specific CTL response constitutes a minor component of the CTL response in healthy virus carriers. Interestingly, analysis of YLLEMLWRL-specific CTL revealed that these CTL were able to lyse EBV-infected B cells expressing different HLA A2 supertype alleles including A*0201, A*0202, A*0203, A*0204, A*0206, A*6802 and A*6901. These data strongly support the notion that HLA class I supertype-restricted CTL may be of significant use in the development of peptide-based immunotherapeutics against EBV-associated malignancies in different ethnic populations.