HSV amplicon mediated augmentation of antitumor effects induced by tumor-specific T cells in the lymphopenic host

2559 Background: Adoptive transfer of T cells has been used in combination with chemotherapy or radiation in order to decrease tumor growth. The specific role of lymphopenia on adoptively transferred T cells in the setting of established tumors is not known. We studied the adoptive transfer of transgenic ovalbumin-specific OT-I T cells into irradiated immunocompetent mice or RAG-1 mice bearing LLC tumor expressing ovalbumin (LLC-ova). In addition, we evaluated the antitumor effects induced by intratumoral injection of HSV amplicons encoding beta-galactosidase (HSV-LacZ), or the combination of HSV-SLC and HSV-CD40L (HSV-S/C). Methods: C57BL/6 mice were injected with LLC-ova cells in the right flank and treated with 550 cGy when the tumor size reached approximately 5mm in diameter. Tumor implants were protected from direct irradiation by a 5 half-value layer lead shield. One day after irradiation, mice were injected intratumorally with PBS, HSV-LacZ, or HSV-S/C every 2 days times 4. RAG-1 mice were injected...