Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus associated with many malignant and nonmalignant human diseases. Life-long latent EBV persistence occurs in blood-borne B lymphocytes, while EBV intermittently productively replicates in mucosal epithelia. Although several models have previously been proposed, the mechanism of EBV transition between these two reservoirs of infection has not been determined. In this study, we present the first evidence demonstrating that EBV latently infects a unique subset of blood-borne mononuclear cells that are direct precursors to Langerhans cells and that EBV both latently and productively infects oral epithelium-resident cells that are likely Langerhans cells. These data form the basis of a proposed new model of EBV transition from blood to oral epithelium in which EBV-infected Langerhans cell precursors serve to transport EBV to the oral epithelium as they migrate and differentiate into oral Langerhans cells. This new model contributes fresh insight into the natural history of EBV infection and the pathogenesis of EBV-associated epithelial disease. Epstein-Barr virus (EBV) is a human herpesvirus that ultimately infects 95% of adults worldwide. EBV is transmitted via mucosal fluids and establishes life-long persistent infection.Although persistent infection is asymptomatic in most people, EBV is associated with benign syndromes, including infectious mononucleosis and oral hairy leukoplakia, and a wide variety of both lymphoid and mucosal epithelial malignancies. Persistent latent EBV infection occurs in memory B lymphocytes that circulate in blood (22). While latent EBV infection also occurs in some epithelial malignancies (29), EBV infection of epithelial cells typically results in productive replication, as demonstrated in oral hairy leukoplakia (9) and in normal oral epithelium (8,10,48).Three different models have previously been proposed to explain the transition of EBV from the latent reservoir of infection in blood-borne B lymphocytes to sites of productive replication in oral epithelium. Model 1 proposes that B lymphocytes carrying latent EBV infection migrate from the blood to the epithelium, where the EBV reactivates and infects adjacent epithelial cells (12), but evidence of intraepithelial B lymphocytes in normal oral epithelium or in oral hairy leukoplakia is lacking (30, 33). Model 2 proposes that EBV virions produced by B lymphocytes in the oral submucosa bind submucosal EBV-specific dimeric immunoglobulin A (IgA) and enter basal oral epithelial cells by endocytosis via the polymeric Ig receptor (37), but the polymeric Ig receptor is not expressed in oral epithelium (23). Model 3 proposes that EBV virions produced by B lymphocytes in oral lymphoid tissues (26) gain access to and infect middle-and upper-layer oral epithelial cells as a result of microscopic traumatic epithelial injury, such as that which occurs during mastication. However, this model is contradicted by evidence that EBV transitions into oral epithelium as cell-associated latent infecti...

This prospective study examined the persistence and transition of Epstein-Barr virus (EBV) in human immunodeficiency virus (HIV)-seropositive subjects with and without oral hairy leukoplakia, a replicative EBV-associated epithelial disease. The intrahost molecular epidemiology of EBV infection was characterized in subjects treated with valacyclovir to suppress EBV replication. Tongue epithelial tissues of HIV-seropositive subjects were found to support not only EBV replication but also persistent, nonproductive EBV infection. EBV appeared to enter the tongue from the blood reservoir of infection and, possibly, from exogenous sources as well. EBV transition from the blood to the tongue appeared to occur even during valacyclovir-mediated suppression of EBV replication, suggesting EBV entry into tongue epithelial tissue as a cell-associated latent infection. In conclusion, these results describe the persistence and transition of EBV as a dynamic interaction between the blood and epithelial reservoirs of EBV infection and suggest a role for entry, persistence, and reactivation of oral epithelial EBV in the pathogenesis of oral hairy leukoplakia.