Varicella-Zoster-Virus-Specific CD4+ Cytotoxic T Cells as Tumor-Specific Effector Cells in Cancer Immunotherapy.

Abstract

Adoptive transfer of gene-engineered T cells expressing tumor antigen-specific chimeric receptors (chRec) is a promising tool in cancer immunotherapy. A major limitation is the failure of chRec to induce proliferative T cell responses, resulting in a rapid loss of function. To provide a strategy for reexpansion of tumor-reactive T cells in vivo, we generated dual-specific T cells that respond to varicella zoster virus while also possessing chRec-mediated tumor reactivity. We expanded VZV-specific cytotoxic T cell lines (VZV-CTL) from four seropositive donors by culturing peripheral blood-derived T cells with lysates extracted from VZV-infected fibroblasts. Repeated stimulation with VZV lysates resulted in efficient and continued expansion for 10–12 weeks. >1x109 T cells were routinely obtained from a starting number of 1x106 peripheral blood T cells. The T cells displayed a mainly CD3+CD4+ (90±5%) phenotype. ELISPOT assays showed specific, MHC class II-restricted IFN-γ release in response to CD40-activated B cells expressing the viral glycoproteins gE and IE62. VZV-CTL belong to a non-regulatory effector T cell subset, shown by their failure to exert antiproliferative effects against cocultured autologous T cells and lack of Foxp3 expression. Retroviral transduction with chRec recognizing the tumor ganglioside antigen GD2 (14.G2a-ζ) and the B cell lineage antigen CD19 (CD19-ζ) resulted in receptor surface expression on 29–74% and 39–45% of cells, respectively. Gene-modified VZV-CTL efficiently recognized antigen-expressing tumor targets in an MHC-independent manner, as demonstrated by antigen-specific secretion of IFN-γ in response to coincubation with GD2-expressing tumor targets. Furthermore, chRec-transduced VZV-CTL performed potent and antigen-specific tumor cytolysis. Antibody blocking experiments revealed that tumor cells were lysed in a granulysin-dependent manner. ChRec-transduced CD3+CD4+ cytolytic VZV-CTL may provide a source of highly potent tumor-reactive cells for adoptive immunotherapy cancer. Endogenous viral reactivations or administration of booster doses of varicella vaccine may lead to survival of these tumor-reactive T cells for prolonged periods of time in vivo.