Activated human γδ T cells as stimulators of specific CD8⁺ T-cell responses to subdominant Epstein Barr virus epitopes: Potential for immunotherapy of cancer.
The efficacy of current cancer vaccines is limited by the functional heterogeneity and poor availability and expansion of professional antigen-presenting cells (APCs). Besides their potent innate effector properties, gamma delta T cells have been suggested to be involved in the initiation and maintenance of adaptive immune responses. Here, we investigated the capacity of human 76 T cells to induce expansion of virus-specific T cells to Epstein Barr vu-LIS (EBV) antigens. Aminobisphosphonate-stimulated human peripheral blood-derived gamma delta T cells (V gamma 2+V delta 2+) acquired a dual phenotype characteristic for both APCs and effector memory T cells. Coincubation of activated gamma delta T cells Pulsed with human leukocyte antigen-restricted epitopes of either the highly stimulatory EBV lytic cycle antigen Bam H1 Z fragment leftward open reading frame or the tumor-associated latent EBV antigen latent membrane protein 2a (LMP2a) with autologous peripheral blood lymphocytes induced selective expansion of peptide-specific. fully functional CD3(+) CD8(+) cytolytic effector memory T cells. Furthermore, gamma delta T APCs efficiently processed and presented endogenous antigen, as demonstrated by the capacity of LMP2a gene-transduced 16 T cells to induce expansion of T cells with broad specificity for various LMP2a peptides. The capacity of autologous gamma delta T cells to induce LMP2a-specific autologous cytotoxic T lymphocytes was confirmed in 2 patients with Hodgkin lymphoma. In summary, bisphosphonate-activated human gamma delta T Cells stimulate expansion of cytotoxic effector T cells specific for both subdominant and dominant viral epitopes and thus show promise as a novel source of efficient APCs for immunotherapy of viral and malignant disease.