During infection with viruses that establish latency, the immune system needs to maintain lifelong control of the infectious agent in the presence of persistent Ag. By using a γ-herpesvirus (γHV) infection model, we demonstrate that a small number of virus-specific central-memory CD8+ T cells develop early during infection, and that virus-specific CD8+ T cells maintain functional and protective capacities during chronic infection despite low-level Ag persistence. During the primary immune response, we show generation of CD8+ memory T cell precursors expressing lymphoid homing molecules (CCR7, L-selectin) and homeostatic cytokine receptors (IL-7α, IL-2/IL-15β). During long-term persistent infection, central-memory cells constitute 20–50% of the virus-specific CD8+ T cell population and maintain the expression of L-selectin, CCR7, and IL-7R molecules. Functional analyses demonstrate that during viral persistence: 1) CD8+ T cells maintain TCR affinity for peptide/MHC complexes, 2) the functional avidity of CD8+ T cells measured as the capacity to produce IFN-γ is preserved intact, and 3) virus-specific CD8+ T cells have in vivo killing capacity. Next, we demonstrate that at 8 mo post-virus inoculation, long-term CD8+ T cells are capable of mediating a protective recall response against the establishment of γHV68 splenic latency. These observations provide evidence that functional CD8+ memory T cells can be generated and maintained during low-load γHV68 persistence.

The respiratory tract is a major mucosal site for microorganism entry into the body, and type I interferon (IFN) and dendritic cells constitute a first line of defense against viral infections. We have analyzed the interaction between a model DNA virus, plasmacytoid dendritic cells, and type I IFN during lung infection of mice. Our data show that murine gammaherpesvirus 68 (␥HV68) inhibits type I IFN secretion by dendritic cells and that plasmacytoid dendritic cells are necessary for conventional dendritic cell maturation in response to ␥HV68. Following ␥HV68 intranasal inoculation, the local and systemic IFN-␣/␤ response is below detectable levels, and plasmacytoid dendritic cells are activated and recruited into the lung with a tissue distribution that differs from that of conventional dendritic cells. Our results suggest that plasmacytoid dendritic cells and type I IFN have important but independent roles during the early response to a respiratory ␥HV68 infection. ␥HV68 infection inhibits type I IFN production by dendritic cells and is a poor inducer of IFN-␣/␤ in vivo, which may serve as an immune evasion strategy.Respiratory viral infections are the leading cause of acute illnesses worldwide, and several members of the herpesvirus family are responsible for severe pneumonia in neonates and immunocompromised patients (52). Herpes simplex virus, cytomegalovirus, varicella-zoster virus, Epstein-Barr virus, human herpesvirus 6, and Kaposi's sarcoma-associated herpesvirus (KSHV) have all been associated with respiratory diseases (7,10,30,33,42,46). Much of our understanding of immune responses to viral infection of the respiratory tract comes from experimental animal models. Murine gammaherpesvirus 68 (␥HV68) is structurally and biologically similar to the human gammaherpesviruses Epstein-Barr virus and KSHV (16,49,50), and it has become a useful in vivo model of herpesvirus infection. Intranasal infection of mice with ␥HV68 causes an acute respiratory infection that is rapidly resolved and followed by the establishment of splenic latency mainly in the B-cell compartment (16, 34). Analogous to KSHV (35,38,41), ␥HV68 also infects dendritic cells, a process that may act as a mechanism of immune evasion (18,20).Plasmacytoid dendritic cells are professional type I interferon (IFN)-producing cells that quickly respond to most viruses by secreting large amounts of type I IFNs (28). Type I IFN signaling is important for the control of acute ␥HV68 infection (17, 51). In addition, plasmacytoid dendritic cells secrete cytokines and interact with conventional dendritic cells and T cells (28) and are critical for the defense against parenteral and mucosal infections (1,13,25,29). Although plasmacytoid dendritic cells have been detected in the lungs (12,14) and have been shown to prevent the development of allergic asthma, we have limited information regarding their role in the antiviral response of the respiratory tract. This is of special importance because the lung is the largest epithelial surface in the body and constit...

It is still unknown whether a noninfectious gammaherpesvirus vaccine is able to prevent or reduce virus persistence. This led us to use dendritic cells loaded with tumor B cells as a vaccine approach for the murine gammaherpesvirus 68 (␥HV68) model of infection. Dendritic cells loaded with UV-irradiated latently infected tumor B cells induce broad, strong, and long-lasting immunity against ␥HV68. Dendritic cell vaccination prevents the enlargement of lymph nodes and severely limits acute infection and early latency but does not prevent ␥HV68 from establishing long-term latency. Our findings support the concept that attenuated viruses may be the best vaccine option for preventing gammaherpesvirus persistence.