Peripheral blood-derived, γ9δ2 t cell-enriched cell lines from glioblastoma multiforme patients exert anti-tumoral effects in vitro.

The goal of this work was to assess the potential of T cells expressing Vγ9Vδ2+ T cell receptors (TCR, γ9δ2T cells) present in peripheral blood (PB) m ononuclear cells (MC, PBMC) of glioblastoma multiforme (GBM) patients to act as anti-tumoral agents. We found that γ9δ2T cell levels were decreased in patients' PB relative to a cohort of healthy donors (HD) (respectively 0.52±0.55%, n=16, vs 1.12±0.6%, n=14, p=0.008) but did not significantly correlate with postoperative survival (R=0.6, p=0.063). Importantly, however, the γ9δ2T cells could be expanded in vitro to consist 51±23% of the cultured lymphocytes (98% CD3+). This was achieved after 14 days of culture in medium containing the amino-bisphosphonate (ABP) Zoledronate (Zol) and interleukin (IL)-2, resulting in γ9δ2T cell-enriched lines (gdTCEL) similar to those of HD derived gdTCEL (54±19%). Moreover, gdTCEL from patients and HD mediated cytotoxicity to GBM-derived cell lines (GBMDCL), which was abrogated by immune-magnetic removal of the γ9δ2T cells. Furthermore, low level interferon (IFN) γ secretion was induced by gdTCEL briefly co-cultured with GBMDCL or autologous - tumor-derived cells, which was greatly amplified in the presence of Zol. Importantly, IFNγ secretion was inhibited by mevastatin but enhanced by cross-linking of butyrophilin 3A1 (CD277) on a CD277+ GBMDCL (U251MG) or by pretreatment of GBMDCL with temozolomide (TMZ). Taken together, these data suggest that γ9δ2T cells in PB of GBM patients can give rise to gdTCEL that mediate anti-tumoral activities.

γδT cells elicited by CMV reactivation after allo-SCT cross-recognize CMV and leukemia.

Human cytomegalovirus (CMV) infections and relapse of disease remain major problems after allogeneic stem cell transplantation (allo-SCT), in particular in combination with CMV-negative donors or cordblood transplantations. Recent data suggest a paradoxical association between CMV reactivation after allo-SCT and reduced leukemic relapse. Given the potential of Vδ2-negative γδT cells to recognize CMV-infected cells and tumor cells, the molecular biology of distinct γδT-cell subsets expanding during CMV reactivation after allo-SCT was investigated. Vδ2(neg) γδT-cell expansions after CMV reactivation were observed not only with conventional but also cordblood donors. Expanded γδT cells were capable of recognizing both CMV-infected cells and primary leukemic blasts. CMV and leukemia reactivity were restricted to the same clonal population, whereas other Vδ2(neg) T cells interact with dendritic cells (DCs). Cloned Vδ1 T-cell receptors (TCRs) mediated leukemia reactivity and DC interactions, but surprisingly not CMV reactivity. Interestingly, CD8αα expression appeared to be a signature of γδT cells after CMV exposure. However, functionally, CD8αα was primarily important in combination with selected leukemia-reactive Vδ1 TCRs, demonstrating for the first time a co-stimulatory role of CD8αα for distinct γδTCRs. Based on these observations, we advocate the exploration of adoptive transfer of unmodified Vδ2(neg) γδT cells after allo-SCT to tackle CMV reactivation and residual leukemic blasts, as well as application of leukemia-reactive Vδ1 TCR-engineered T cells as alternative therapeutic tools.