Progression of armed CTL from draining lymph node to spleen shortly after localized infection with herpes simplex virus 1

We have examined the generation of CTL immunity immediately after localized footpad infection with herpes simplex virus 1 (HSV-1) using three coordinated in vivo T cell tracking methodologies. Tetrameric MHC class I containing the immunodominant peptide from HSV-1 glycoprotein B (gB) showed that after infection the proportion of Ag-specific T cells peaked at day 5 within draining popliteal lymph nodes and 2 days later in the spleen. Preferential expression of the activation marker CD25 by tetramer-positive cells in draining popliteal nodes but not spleen suggested that gB-specific T cells were initially activated within the lymph node. In vivo cytotoxicity assays showed that Ag-specific effector cells were present within the draining lymph nodes as early as day 2 after infection, with a further 2-day lag before detection in the spleen. Consistent with the very early arming of effector CTL in the draining lymph node, adoptive transfer of CFSE-labeled gB-specific transgenic T cells showed that they had undergone one to four rounds of cell division by day 2 after infection. In contrast, proliferating T cells were first detected in appreciable numbers in the spleen on day 4, at which time they had undergone extensive cell division. These data demonstrate that HSV-1-specific T cells are rapidly activated and armed within draining lymph nodes shortly after localized HSV-1 infection. This is followed by their dissemination to other compartments such as the spleen, where they further proliferate in an Ag-independent fashion.