Spontaneous T cell responses to Epstein-Barr virus-encoded BARF1 protein and derived peptides in patients with nasopharyngeal carcinoma: bases for improved immunotherapy.
Immunotherapy approaches targeting Epstein-Barr virus (EBV)-encoded antigens induce objective clinical responses only in a fraction of patients with undifferentiated nasopharyngeal carcinoma (UNPC). In the present study, we have characterized the immunogenicity of the EBV-encoded BARF1 oncogene with the aim to assess whether this protein could constitute a new target antigen for immunotherapy in this setting. Spontaneous CD4+ and CD8+ T cell responses specific for the recombinant p29 BARF1 protein were detected by IFNgamma-ELISPOT in both EBV-seropositive donors and UNPC patients, but not in EBV-seronegative individuals. Using immunoinformatic prediction tools, we have selected 5 different candidate BARF1 T cell epitopes presented by HLA-A*0201. Although only one of these peptides was able to bind HLA-A2 with low affinity in the T2 stabilization assay, all 5 BARF1 nonamers readily elicited specific CD8+ T cell responses in EBV-seropositive HLA-A*0201+ donors and UNPC patients. Notably, the magnitude of CD8+ T cell responses to the whole BARF1 protein and derived A*0201 peptides was significantly higher in UNPC patients than in healthy donors. Moreover, cytotoxic T lymphocytes specific for the p2-10, p23-31, or p49-57 BARF1 peptides were easily obtained from HLA-A*0201+ donors. These cultures were not only able to lyse autologous targets loaded with the antigenic peptide, but also recognized tumor cells endogenously expressing BARF1 in an antigen-specific and HLA-A2-restricted manner. These findings, indicate that BARF1 is a particularly attractive antigen with immunogenic properties in most UNPC patients and provide valuable information to develop new strategies to improve the efficacy of EBV-targeting immunotherapy of UNPC patients.
Martorelli
Debora
D
Cancer Bioimmunotherapy Unit, Centro di Riferimento Oncologico, IRCCS-National Cancer Institute, Aviano, PN, Italy.
Houali
Karim
K
Caggiari
Laura
L
Vaccher
Emanuela
E
Barzan
Luigi
L
Franchin
Giovanni
G
Gloghini
Annunziata
A
Pavan
Alessandro
A
Da Ponte
Alessandro
A
Tedeschi
Rosa Maria
RM
De Re
Valli
V
Carbone
Antonino
A
Ooka
Tadamasa
T
De Paoli
Paolo
P
Dolcetti
Riccardo
R
D002277:Carcinoma / Q000276:immunology* / Q000628:therapy; D000939:Epitopes; D006801:Humans; D007167:Immunotherapy / Q000379:methods*; D007558:Italy; D009303:Nasopharyngeal Neoplasms / Q000276:immunology* / Q000628:therapy; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*; D014764:Viral Proteins / Q000378:metabolism*
C086495:BARF1 protein, Human herpesvirus 4; D000939:Epitopes; D014764:Viral Proteins