Adoptively transferred tumor-specific T cells stimulated Ex vivo using herpes simplex virus amplicons encoding 4-1BBL persist in the host and show antitumor activity In vivo

4-IBB is a T-cell costimulatory receptor which binds its ligand 4-IBBL, resulting in prolonged T cell survival. We studied the antitumor effects of adoptively transferred tumor-specific T cells expanded ex vivo using tumors transduced with herpes simplex virus (HSV) amplicons expressing 4-IBBL as a direct source of antigen and costimulation. We constructed HSV amplicons encoding either the 4-IBBL, (HSV.4-IBBL) or B7.1 (HSV.B7.1) costimulatory ligands. Lewis lung carcinoma cells expressing ovalbumin (LLC/OVA) were transduced with HSV.4-IBBL, HSV.B7.1, or control HSV amplicons and used to stimulate GFP(+) OVA-specific CD8(+) T cells (OT-1/GFP) ex vivo. Naive or ex vivo stimulated OT-1/GFP cells were adoptively transferred into LLC/OVA tumor-bearing mice. Higher percentages of OT-1/ GFP cells were seen in the peripheral blood, spleen, and tumor bed of the HSV.4-IBBL-stimulated OT-1/GFP group compared with all other experimental groups. OT-1 cells identified within the tumor bed and draining lymph nodes of theHSV.4-IBBLstimulated OT-1 group showed enhanced bromodeoxyuridine (BrdUrd) incorporation, suggesting ongoing expansion in vivo. Mice receiving HSV.4-IBBL-stimulated OT-I/GFP had significantly decreased tumor volumes compared with untreated mice (P < 0.001) or to mice receiving naive OT-I/GFP (P < 0.001). Transfer of HSV.B7.1-stimulated OT-I/GFP did not protect mice from tumor. Mice that received HSV.4-IBBL-stimulated OT-1/ GFP exhibited increased cytolytic activity against LLC/OVA and higher percentages of Ly-6C(+) OT-I/GFP in the spleen and tumor bed compared with controls. Tumor-specificTcells stimulated ex vivo using tumor transduced with HSV.4-IBBL expand in vivo following adoptive transfer, resulting in tumor eradication and the generation of tumor-specific CD44(+)Ly-6C(+)CD62L(-) effector memory T cells. [Cancer Res 2007;67(20):10027-37]