Activated Human γδ T Cells as Stimulators of Specific CD8+ T-cell Responses to Subdominant Epstein Barr Virus Epitopes

Abstract

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, gammadelta T cells have been suggested to be involved in the initiation and maintenance of adaptive immune responses. Here, we investigated the capacity of human gammadelta T cells to induce expansion of virus-specific T cells to Epstein Barr virus (EBV) antigens. Aminobisphosphonate-stimulated human peripheral blood-derived gammadelta T cells (Vgamma2+Vdelta2+) acquired a dual phenotype characteristic for both APCs and effector memory T cells. Coincubation of activated gammadelta 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 CD3CD8 cytolytic effector memory T cells. Furthermore, gammadelta T APCs efficiently processed and presented endogenous antigen, as demonstrated by the capacity of LMP2a gene-transduced gammadelta T cells to induce expansion of T cells with broad specificity for various LMP2a peptides. The capacity of autologous gammadelta T cells to induce LMP2a-specific autologous cytotoxic T lymphocytes was confirmed in 2 patients with Hodgkin lymphoma. In summary, bisphosphonate-activated human gammadelta 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.