Prevention of Viral Infections after T Cell Depleted Allogeneic Stem Cell Transplantation By Infusion of Multi-Antigen Specific T Cell Products

Opportunistic viral infections and relapse are major complications in patients after T cell depleted allogeneic stem cell transplantation (TCD alloSCT). Since the application of unmodified donor lymphocyte infusion (DLI) early after alloSCT results in a high risk of graft versus host disease (GVHD), infusion of selected populations of virus-specific donor T cells can be an effective approach to safely restore anti-viral immunity early after alloSCT. As part of the EU FP7 consortium T Control, in this phase I/II study the feasibility and safety of the generation and administration of selected populations of donor-derived T cells targeting multiple antigens (Ag) is assessed. The multi Ag-specific T cell products contained T cells targeting cytomegalovirus (CMV), Epstein Bar virus (EBV) and adenovirus (AdV) as well as T cells targeting tumor associated Ag (TAA) and minor histocompatibility Ag (MiHA) to boost the graft versus leukemia (GVL) reactivity. To assess efficacy, in-vivo appearance or expansion of Ag-specific T cells, and the effect on viral reactivations and/or disease relapse was evaluated for 20 weeks after infusion until regular DLI was applied.

HLA-A*02⁺ patients treated for a hematological malignancy with an HLA-matched TCD alloSCT from a CMV and/or EBV seropositive donor were included in this study. 6-8 weeks after alloSCT, T-cells directed against HLA-A*02-restricted peptides of CMV, EBV and AdV, and the TAA NY-eso, WT-1, RHAMM, PRAME and proteinase 3 were isolated using the reversible streptamer-nanobead technology (Juno) by cliniMACS selection out of the naïve and/or memory T cell compartment from 2*10^9 donor PBMC. Depending on the HLA-typing of the patient/donor additional streptamers targeting viral peptides in A*01, A*24, B*07 or B*08 were added to the selection procedure. In case of patient/donor MiHA disparity in the GvL direction, the HLA-A*0201/HA-1h streptamer was also added. This procedure allows purification of T cells under GMP conditions in 1 day.

20 multi Ag-specific T cell products were generated of which 19 met the release criteria. These products consisted of 0.5-12*10^6 cells containing purities of 46,0-94,3% target Ag-specific CD8+ T cells within the T cell compartment. In all products CMV and/or EBVas well as AdV virus-specific memory T cells were isolated comprising 99% of the target Ag-specific CD8+ T cells, while the other 1% included the TAA and MiHA specificities or CMV specific T cells from seronegative donors. 17 products were administered without infusion-related complications or GVHD; 2 patients experienced GVHD before infusion and did not receive their product.

Of the 14 patients evaluated at this stage, 13 completed the follow-up period until DLI and 1 patient died during follow-up. No product-related adverse events were reported. In all 5 CMV^- patients and in 3/9 CMV⁺ patients no CMV reactivation and no expansion of CMV-specific T cells was observed. The other 6 CMV⁺ patients experienced CMV reactivations. In 2/6 patients who received the product from a CMV⁺ donor CMV-specific T cells were detected with tetramer analysis and CMV was cleared. From the other 4 reactivating patients with CMV^- donors 3 had circulating CMV-specific T cells already at the moment of infusion, whereas in 1 patient CMV-specific T cells clearly expanded after infusion, resulting in viral clearance in all 4 patients.

All 14 donors were EBV⁺. In 7 patients EBV reactivations were observed, which coincided in 2/7 patients with the appearance of EBV-specific T cells and subsequent clearance of the virus. In 4/7 patients EBV reactivation was cleared without clear expansion of EBV-specific T cells. However, 1 patient required treatment for an EBV-PTLD, although ultimately EBV-specific T cells appeared and EBV was cleared.

In none of the patients AdV DNA loads were detected in the follow-up period, while in 1 patient expansion of AdV-specific T cells was observed.

Expansion of TAA and MiHA-specific T cells could not be demonstrated in-vivo using tetramer staining. More sensitive techniques will be required to visualize these cells. 2 patients showed relapse of their malignancy before DLI infusion.

In this clinical study, we have shown that the reversible streptamer technology based generation and adoptive transfer of donor-derived multi Ag-specific T cell products is feasible and safe and can be used as a strategy to prevent viral infections in the interval between TCD alloSCT and DLI.