Aminobisphosphonates Synergize with Human Cytomegalovirus To Activate the Antiviral Activity of Vγ9Vδ2 Cells

Human V gamma 9V delta 2 T cells are activated through their TCR by neighboring cells producing phosphoantigens. Zoledronate (ZOL) treatment induces intracellular accumulation of the phosphoantigens isopentenyl pyrophosphate and ApppI. Few attempts have been made to use immunomanipulation of V gamma 9V delta 2 lymphocytes in chronic viral infections. Although V gamma 9V delta 2 T cells seem to ignore human CMV (HCMV)-infected cells, we examined whether they can sense HCMV when a TCR stimulus is provided with ZOL. Fibroblasts treated with ZOL activate V gamma 9V delta 2 T cells to produce IFN-gamma but not TNF. Following the same treatment, HCMV-infected fibroblasts stimulate TNF secretion and an increased production of IFN-g, indicating that V gamma 9V delta 2 cells can sense HCMV infection. Increased lymphokine production was observed with most clinical isolates and laboratory HCMV strains, HCMV-permissive astrocytoma, or dendritic cells, as well as "naive" and activated V gamma 9V delta 2 cells. Quantification of intracellular isopentenyl pyrophosphate/ApppI following ZOL treatment showed that HCMV infection boosts their accumulation. This was explained by an increased capture of ZOL and by upregulation of HMG-CoA synthase and reductase transcription. Using an experimental setting where infected fibroblasts were cocultured with gamma delta cells in submicromolar concentrations of ZOL, we show that V gamma 9V delta 2 cells suppressed substantially the release of infectious particles while preserving uninfected cells. V gamma 9V delta 2 cytotoxicity was decreased by HCMV infection of targets whereas anti-IFN-gamma and anti-TNF Abs significantly blocked the antiviral effect. Our experiments indicate that cytokines produced by V gamma 9V delta 2 T cells have an antiviral potential in HCMVinfection. This should lead to in vivo studies to explore the possible antiviral effect of immunostimulation with ZOL in this context.