title: Ex vivo stimulation of B cells latently infected with gammaherpesvirus 68 triggers reactivation from latency.
abstract: Murine gammaherpesvirus 68 (gammaHV68) infection of mice results in the establishment of a chronic infection, which is largely maintained through latent infection of B lymphocytes. Acute virus replication is almost entirely cleared by 2 weeks postinfection. Spontaneous reactivation of gammaHV68 from latently infected splenocytes upon ex vivo culture can readily be detected at the early stages of infection (e.g., day 16). However, by 6 weeks postinfection, very little spontaneous reactivation is detected upon explant into tissue culture. Here we report that stimulation of latently infected splenic B cells harvested at late times postinfection with cross-linking surface immunoglobulin (Ig), in conjunction with anti-CD40 antibody treatment, triggers virus reactivation. As expected, this treatment resulted in B-cell activation, as assessed by upregulation of CD69 on B cells, and ultimately B-cell proliferation. Since anti-Ig/anti-CD40 stimulation resulted in splenic B-cell proliferation, we assessed whether this reactivation stimulus could overcome the previously characterized defect in virus reactivation of a v-cyclin null gammaHV68 mutant. This analysis demonstrated that anti-Ig/anti-CD40 stimulation could drive reactivation of the v-cyclin null mutant virus in latently infected splenocytes, but not to the levels observed with wild-type gammaHV68. Thus, there appears to be a role for the v-cyclin in B cells following anti-Ig/anti-CD40 stimulation independent of the induction of the cell cycle. Finally, to assess signals that are not mediated through the B-cell receptor, we demonstrate that addition of lipopolysaccharide to explanted splenocyte cultures also enhanced virus reactivation. These studies complement and extend previous analyses of Epstein-Barr virus and Kaposi's sarcoma-associated virus reactivation from latently infected cell lines by investigating reactivation of gammaHV68 from latently infected primary B cells recovered from infected hosts.
authors.affiliation: Center for Emerging Infectious Diseases, Yerkes National Primate Research Center, Emory University School of Medicine, 954 Gatewood Rd., NE, Atlanta, GA 30329, USA.
authors.forename: Janice M
authors.initials: JM
authors.lastname: Moser
authors.forename: Jason W
authors.initials: JW
authors.lastname: Upton
authors.forename: Kathleen S
authors.initials: KS
authors.lastname: Gray
authors.forename: Samuel H
authors.initials: SH
authors.lastname: Speck
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000821:virology*; D019013:CD40 Antigens / Q000276:immunology; D018142:Gammaherpesvirinae / Q000502:physiology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation; D051379:Mice; D013154:Spleen / Q000821:virology; D014775:Virus Activation / Q000502:physiology*; D017735:Virus Latency / Q000502:physiology*
chemical_list: D019013:CD40 Antigens; D008070:Lipopolysaccharides