The present invention relates to the identification of a subunit vaccine to prevent or treat infection of Epstein Barr Virus. In particular, EBNA-1 was identified as a vaccine antigen. In a specific embodiment, a purified protein corresponding to EBNA-1 elicited a strong CD4⁺ T cell response. The responsive CD4⁺ T cell are primarily T_H1 in function. EBNA-1 is an attractive candidate for a protective vaccine against EBV, and for immunotherapy of EBV infection and neoplasms, particularly with dendritic cells charged with EBNA-1.