Cytomegaloviruses (CMV) are highly ubiquitous herpesviruses that are commonly acquired early in life. Acute infections are often asymptomatic; however, a state of latency is established such that CMV persists for the life of the host. This provides opportunities to reactivate and transmit virus to new, susceptible hosts. A variety of bodily fluids transmit acute and reactivated CMV, with saliva being a prominent source. Within epithelial cells of the salivary glands, CMV replication is protracted, such that transmission of infectious virus is prolonged for months. The murine model of CMV infection has demonstrated that a robust innate and adaptive immune response is elicited within these glands, consisting largely of activated, virus-specific CTL, as well as CD4+ T cells, NK cells, TCR/d T cells, and macrophages. Virus is, however, refractory to the CTL response and is eventually cleared weeks later by a CD4+ T cell-mediated mechanism. Strategies to hasten clearance of CMV from this site should therefore be targeted towards enhancing the CD4+ T cell-mediated response. This application aims to define the cellular effectors of a novel CD4+ T cell-mediated enhancement of antiviral immunity. This phenomenon involves immunization in the absence of peripheral CD8+ T cells. Priming in the absence of CD8+ T cells induces a """"""""super"""""""" CD4+ T cell that cooperates with an undefined innate effector cell to promote antiviral immunity. Defining the effector cell(s) and the molecular mediators that exert the antiviral functions are important for studying the regulation of this novel mechanism and for designing strategies to boost antiviral immunity to promote clearance of an otherwise chronic state of viral replication. It is our hypothesis that when primed in the absence of CD8+ T cells, """"""""super"""""""" CD4+ T cells are empowered to activate NK-like cells, TCR?/d T cells, or macrophages that serve as effectors in clearing the salivary glands of infectious murine CMV (MCMV).
In Aim 1, we will define the effector cell(s) that promotes clearance of MCMV from the submaxillary salivary gland when mice are infected in the absence of CD8+ T cells. This will be accomplished by selective depletion of candidate effector cells as well as adoptive transfer studies. We will then identify, in Aim 2, the signature molecules that distinguish maturation of dendritic cells, priming of CD4+ T cells, and activation of the effector cell in the absence of CD8+ T cells. Expression arrays for cytokines, chemokines, and other regulatory or effector molecules will provide the basis for this identification. These data will assist in the design of studies to decipher the mechanisms regulating this novel immune response and how it can be manipulated to promote clearance of a chronically-infected organ during a natural infection. Relevance: Human cytomegalovirus is a teratogenic virus that is highly transmissible, in part due to chronic excretion in saliva as a consequence of prolonged replication in salivary glands. Young children in day care settings secrete infectious virus in saliva for years following acute infection, and serve as a threat of infection to their pregnant mothers. Strategies designed to manipulate and immunologically enhance clearance of virus from this organ will assist in curtailing transmission of this ubiquitous human pathogen. ? ? ?
