Gammaherpesviruses include the human pathogens Epstein-Barr virus (EBV/HHV-4) and Kaposi's sarcoma-associated herpesvirus (KSHV/HHV-8) [8] , the etiologic agents of some of the most common AIDS-associated cancers, such as Burkitt's lymphoma, nasopharyngeal carcinoma, and primary effusion lymphoma. The related murine gammaherpesvirus 68 (MHV68) is often used as a model for human gammaherpesviruses because, unlike KSHV and EBV, it is genetically tractable, readily replicates in tissue culture without the use of chemicals or overexpression to overcome latency, and infects small rodents including laboratory mice [9, 10, 11] . MHV68 has therefore been instrumental in the identification of factors that contribute to in vivo replication and pathogenesis of the gammaherpesviruses.