Protective antiviral cytotoxic T cell memory is most efficiently maintained by restimulation via dendritic cells

Dendritic cells (DC) play a key role in the initiation of T cell-mediated i mmune responses and may therefore be successfully used in antiviral and ant itumor vaccination strategies. Because both strength and duration of an imm une response determines the outcome of a vaccination protocol, we evaluated the life span of DC-induced antiviral CTL memory against systemic and peri pheral challenge infections with lymphocytic choriomeningitis virus (LCMV), We found that expansion and activation of CTL by DC was transient. Protect ion against systemic LCMV infection after DC immunization was relatively lo ng-lived (>60 days), whereas complete protection against peripheral infecti on via intracerebral infection or infection into the footpad with LCMV, whe re rapid recruitment of effector T cells to the site of infection and elimi nation of viral pathogen plays a major role, was short-lived (<30 days). Pr otective immunity was most efficiently restored by administration of antige nic peptides via DC, rather than in combination with IFA or in liposomes, T hese results suggest that Ag presentation by DC may be crucial for both ini tiation and maintenance of protective CTL-mediated immunity against viruses infecting solid organs or against peripheral mesenchymal or epithelial tum ors.