Unraveling immunity to gamma-herpesviruses: a new model for understanding the role of immunity in chronic virus infection

Murine gamma-herpesvirus 68 (gamma HV68) infection is a new model for under standing how immunity and chronic gamma-herpesvirus infection inter-relate, gamma HV68 is closely related to the human Epstein-Barr virus and Kaposi's sarcoma herpesvirus and is associated with tumors, vasculitis of the great elastic arteries and splenic fibrosis. Advances in the past year have prov ided an even stronger foundation for believing that gamma HV68 infection of normal and mutant mice will become the pre-eminent animal model for unders tanding gamma-herpesvirus pathogenesis and immunity. gamma HV68 latency has been characterized employing new assays for quantitating cells carrying th e gamma HV68 genome and cells that reactivate gamma HV68 and for detecting the presence of preformed infectious virus in tissues. These advances have fostered the first steps towards a molecular definition of gamma HV68 laten cy. It appears that gamma HV68 shares latency programs with human gamma-her pesviruses - including the loci for gene 73, v-bcl-2 and the viral homolog of the G-protein coupled receptor This provides candidate antigens for anal ysis of the role of T and B cells in regulating latency. Multiple cellular reservoirs for gamma HV68 latency were uncovered with the demonstration tha t gamma HV68 latently infects macrophages in addition to B cells, A critica l role for B cells in regulating the nature of gamma HV68 latency was disco vered and the mechanism was shown to be via alteration of the efficiency of reactivation. Studies of the response of CD4(+) and CD8(+) cells during ac ute and chronic gamma HV68 were performed. These new studies provide key bu ilding blocks for further development of this novel and interesting model s ystem.