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 immune responses and may therefore be successfully used in antiviral and antitumor vaccination strategies. Because both strength and duration of an immune response determines the outcome of a vaccination protocol, we evaluated the life span of DC-induced antiviral CTL memory against systemic and peripheral challenge infections with lymphocytic choriomeningitis virus (LCMV). We found that expansion and activation of CTL by DC was transient. Protection against systemic LCMV infection after DC immunization was relatively long-lived (>60 days), whereas complete protection against peripheral infection via intracerebral infection or infection into the footpad with LCMV, where rapid recruitment of effector T cells to the site of infection and elimination of viral pathogen plays a major role, was short-lived (<30 days). Protective immunity was most efficiently restored by administration of antigenic peptides via DC, rather than in combination with IFA or in liposomes. These results suggest that Ag presentation by DC may be crucial for both initiation and maintenance of protective CTL-mediated immunity against viruses infecting solid organs or against peripheral mesenchymal or epithelial tumors.