CD8 T cell recognition of endogenously expressed epstein-barr virus nuclear antigen 1.
The Epstein-Barr virus (EBV) nuclear antigen (EBNA)1 contains a glycine-alanine repeat (GAr) domain that appears to protect the antigen from proteasomal breakdown and, as measured in cytotoxicity assays, from major histocompatibility complex (MHC) class I-restricted presentation to CD8+ T cells. This led to the concept of EBNA1 as an immunologically silent protein that although unique in being expressed in all EBV malignancies, could not be exploited as a CD8 target. Here, using CD8+ T cell clones to native EBNA1 epitopes upstream and downstream of the GAr domain and assaying recognition by interferon gamma release, we show that the EBNA1 naturally expressed in EBV-transformed lymphoblastoid cell lines (LCLs) is in fact presented to CD8+ T cells via a proteasome/peptide transporter-dependent pathway. Furthermore, LCL recognition by such CD8+ T cells, although slightly lower than seen with paired lines expressing a GAr-deleted EBNA1 protein, leads to strong and specific inhibition of LCL outgrowth in vitro. Endogenously expressed EBNA1 is therefore accessible to the MHC class I pathway despite GAr-mediated stabilization of the mature protein. We infer that EBNA1-specific CD8+ T cells do play a role in control of EBV infection in vivo and might be exploitable in the control of EBV+ malignancies.
Lee
Steven P
SP
Institute for Cancer Studies, University of Birmingham, Vincent Drive, Edgbaston, Birmingham B15 2TT, UK. s.p.lee@bham.ac.uk
Brooks
Jill M
JM
Al-Jarrah
Hatim
H
Thomas
Wendy A
WA
Haigh
Tracey A
TA
Taylor
Graham S
GS
Humme
Sibille
S
Schepers
Aloys
A
Hammerschmidt
Wolfgang
W
Yates
John L
JL
Rickinson
Alan B
AB
Blake
Neil W
NW
D000409:Alanine; D000595:Amino Acid Sequence; D002051:Burkitt Lymphoma; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D045744:Cell Line, Tumor; D020031:Epstein-Barr Virus Infections / Q000235:genetics / Q000276:immunology; D019309:Epstein-Barr Virus Nuclear Antigens / Q000235:genetics / Q000276:immunology*; D005998:Glycine; D004854:Herpesvirus 4, Human / Q000276:immunology; D006801:Humans; D008285:Major Histocompatibility Complex; D010446:Peptide Fragments / Q000276:immunology; D020449:Repetitive Sequences, Amino Acid
D019309:Epstein-Barr Virus Nuclear Antigens; D010446:Peptide Fragments; C417029:EBV-encoded nuclear antigen 1; D000409:Alanine; D005998:Glycine