Epstein–Barr virus nuclear antigen 1‐specific CD4⁺ T cells directly kill Epstein–Barr virus‐carrying natural killer and T cells

Abstract

Epstein-Barr virus (EBV) nuclear antigen (EBNA)1 is expressed in every EBV-infected cell, regardless of the state of EBV infection. Although EBNA1 is thought to be a promising antigen for immunotherapy of all EBV-associated malignancies, it is less clear whether EBNA1-specific CD4+ T cells can act as direct effectors. Herein, we investigated the ability of CD4 + T-cell clones induced with overlapping peptides covering the C-terminal region of EBNA1, and identified minimal epitopes and their restricted major histocompatibility complex class II molecules. Of these, a novel epitope, EYHQEGGPD, was found to be presented by DRB1*0401, 0403 and 0406. (1) It is also related to natural killer (NK) and T lymphomas and causes chronic active EBV infection (CAEBV).(1,2) Only EBV nuclear antigen (EBNA)1 is expressed in most BL, referred to as latency I. In addition to EBNA1, latent membrane protein (LMP)1 and/ or 2 are expressed in HD, nasopharyngeal carcinomas, NK and T lymphomas, and CAEBV (latency II). All EBV latent antigens, EBNA1, 2, 3A, 3B, 3C and the leader protein, and LMP1 and 2 are expressed in post-transplant lymphoproliferative disorder (latency III). EBNA1 is expressed in common in all these diseases,and may be present diffusely bound to mitotic chromosomes.(4) EBV has a cis-acting element, termed OriP, that enables the persistence of episomes in EBV-infected cells. EBNA1 also binds to OriP, (5) and is essential for EBV episome maintenance.(6) Thus, the existence of EBV DNA is tightly associated with EBNA1 expression in EBV-infected cells.Evidence for the significance of EBV-specific T cells for control of EBV infection has been obtained from both in vitro and in vivo studies. (7,8) Human leukocyte antigen (HLA) class I-restricted CD8 + cytotoxic T lymphocytes (CTL) recognize latent and lytic EBV antigens, (8) and latent EBV antigen-specific CTL kill not only lymphoblastoid cell lines (LCL) expressing the full spectrum of latent viral proteins but also tumor cells with limited viral proteins.(9-11) EBV-specific CTL responses have been extensively studied, and CTL are thought to be the main effectors. EBNA1-specific CTL were long believed to be immunologically silent because EBNA1 contains an internal G-A repeat (GAr) domain which has an immune evasion function endowing resistance to proteasomal degradation in the antigen presentation pathway. (12,13) However, it has been reported that having GAr EBNA1 does not completely evade major histocompatibility complex (MHC) class I presentation. (10,(14)(15)(16) There are thus some EBNA1 antigen epitopes, though the importance of EBNA1-specific CTL for EBV-positive tumors remains unclear.Accumulating current evidence indicates that CD4 + T cells, as well as CTL, are required for effective antitumor immunity, (17)(18)(19) for example, playing an essential role in generation of CD8 + T memory cells. (20)(21)(22) In addition, there are reports of cytotoxic action of CD4 + T effector cells in vitro (23) and in vivo. (23,24) This has drawn attention to the possibility that E...

A novel latent membrane 2 transcript expressed in Epstein-Barr virus–positive NK- and T-cell lymphoproliferative disease encodes a target for cellular immunotherapy

“…Our results showed that these malignant T and NK cells had the machinery for antigen-processing and presentation, were recognized by polyclonal effectors containing LMP2-specific CTLs as minor populations, and more importantly, by LMP2-specific CD8 ϩ clones; efficiently recognizing multiple LMP2 epitopes across 3 different restriction elements. These data greatly strengthen the isolated reports describing killing of T and NK lines by EBNA1 41 or LMP1 42,43 clones by extending to the most immunogenic and clinically relevant of available targets, LMP2. Our data provide a rationale to pursue adoptive CTL immunotherapy for patients with ENKTL and CAEBV.…”

The interplay between Epstein-Barr virus and the immune system: a rationale for adoptive cell therapy of EBV-related disorders

“…The attention has been focused on cytotoxic CD4 + T cells, which proved to be effective, at least in vitro, not only against EBV LCL but also, more importantly, against infected NK or T cells, the natural target in NK/Tcell lymphoma and CAEBV. 86,87 Such observations differ from the previous reports related to these diseases [82][83][84][85] which only demonstrated the activity against LCL that express a larger pattern of viral antigen and costimulatory molecules than EBV-infected NK/T cells.…”

Identification of Promiscuous KIF20A Long Peptides Bearing Both CD4+ and CD8+ T-cell Epitopes: KIF20A-Specific CD4+ T-cell Immunity in Patients with Malignant Tumor

“…A human immunodeficiency virus (HIV) peptide that binds to HLA-A24 (HIV-A24) was used as a negative control SP (17). A WT1-derived LP presented by HLA-DR4 (WT1-peptide) and a promiscuous HIV-derived LP were used as negative control LPs (20,21). Peptides were dissolved in dimethylsulfoxide at 10 mg/mL.…”