Clinical grade generation of hexon-specific T cells for adoptive T-cell transfer as a treatment of adenovirus infection after allogeneic stem cell transplantation

Adenovirus infection after allogeneic hematopoietic stein cell transplantation is still causing significant morbidity and mortality, especially in children. It has been demonstrated that a sufficient host T-cell response is essential to clear the virus. Adoptive transfer of specific T-cell immunity from the donor to the recipient has become a new treatment option for patients with systemic adenoviral infection who lack specific T-cell responses. The adenoviral hexon protein was shown to be an immunodominant T-cell target. We describe here a Good Manufacturing Practice-compatible generation of hexon-specific T cells developed by isolating interferon-gamma-secreting T cells after stimulation of mononuclear cells ex vivo with hexon protein. Phenotypical and functional characterization of the generated, specific T-cell product resulted in a mixed population of CD4 and CD8-positive T cells with an intermediate effector memory phenotype. Isolated hexon-specific T cells showed high expansion potential in vitro and specific cytotoxicity. T-cell lines, directed against type 5 hexon protein showed good cross-reactivity against viral strains from other adenovirus species. The availability for isolation of hexon-specific T cells among 76 hematopoietic stem cell transplantation donors showed in > 72% a sufficient T-cell response (0.05% of T cells). In conclusion, Good Manufacturing Practice-grade selection of adenovirus-specific T cells for adoptive immunotherapy by hexon-induced secretion of interferon-gamma has been established. Adoptive T-cell transfer could potentially restore T-cell immunity against adenovirus after allogeneic stem cell transplantation.