Spinal column was harvested from intranasal TK HSV-2 immunized mice 45 min after tail vein injection with 200 µl of 5 mg/ml Oregon Green 488-conjugated dextran (70kDa, D7173, Thermo Fisher Scientific, MA) in PBS. Spine was then fixed with 4% paraformaldehyde in PBS overnight, and cut frozen sections (8 µm in thickness) for immunohistochemical analysis30 (link).