Abstract
The major histocompatibility complex class I‐restricted CD8^+^ cytotoxic T‐lymphocyte (CTL) effector arm of the adaptive immune response can specifically recognize and destroy tumor cells expressing peptide antigens. Although adoptive T‐cell therapy has been successfully used for the treatment of viral and malignant diseases, little is known of the trafficking and fate of adoptively transferred antigen‐specific T cells. In the present study, splenocytes derived from mice that rejected their tumors (CT26 or CT26‐clone 25 tumors) in response to direct intratumor injection of disabled infectious single‐cycle herpes simplex virus (DISC‐HSV) encoding murine GM‐CSF were restimulated with peptide in vitro. CTLs specific for the AH‐1 and β‐gal peptides expressed by CT26 and CT26‐clone 25 tumor cells, respectively, were generated and used for adoptive cellular therapy and trafficking studies. Intravenous administration of AH‐1‐specific CTLs 3 days following i.v. injection of CT26 cells resulted in significant tumor growth inhibition, whereas administration of control CTLs generated against a bacterial β‐gal peptide did not inhibit the growth of tumors. Trafficking of AH‐1‐specific lymphocytes and their interaction with the CT26 tumor microcirculation was analyzed using real‐time in vivo microscopy (IVM). AH‐1‐specific but not β‐gal‐specific CTLs adhered and localized in the CT26 tumor microvasculature, but neither population adhered to the endothelium of the normal microcirculation. This study provides direct visual evidence suggesting that AH‐1‐specific CTLs that mediate a therapeutic response traffic to and localize within the tumor microenvironment. © 2004 Wiley‐Liss, Inc.