Protective immunity against a eajority of viral infections is mediated by a combination of both humoral and cell-mediated immune responses. However, in the case of herpesvirus infections, where viral spread is largely cell-to-cell, cell-mediated immune mechanisms (which facilitate the clearance of virally infected cells) are particularly important (1-4). Moreover, cell-mediated immunity (CMI) has also been implicated in the establishment and/or reactivation of latent herpes simplex virus (HSV) infection (5,6). Thus, a major focus of herpesvirus immunology continues to be the identification of those herpesvirus antigens that serve as targets for CMI and the means by which protective responses can be optimally induced. Clearly this information is critical for the rational development of effective vaccine strategies.