Background: Adoptive transfer of virus-specific T cells may accelerate reconstitution of antigen-specific immunity and limit the morbidity and mortality of viral infections following allogeneic hematopoietic stem cell transplantation. The logistics of producing virus-specific T cells has, however, limited the application of cellular therapies, particularly following the introduction of more-recent regulatory stipulations.

Methods: We investigated the ability of cytomegalovirus-specific T cells, directly isolated from donor leucapheresates on the basis of interferon γ secretion, to restore antiviral immunity in a group of 25 patients following related-donor transplantation in a single-arm phase I-II study. Selected cells were administered early following transplantation, either after the detection of cytomegalovirus DNA by polymerase chain reaction-based surveillance or prophylactically between day 40 and day 50.

Results: Cell selection was successful in all cases, yielding a product biased towards CD4(+) over CD8(+) T cells. The target cell dose of 1 × 10(4) CD3(+) T cells/kg of recipient weight contained a median of 2840 cytomegalovirus-specific CD4(+) cells/kg and 630 cytomegalovirus-specific CD8(+) cells/kg, with a median purity of 43.9% interferon γ-secreting cells. Expansions of both CD4(+) and CD8(+) cytomegalovirus-specific T cells were observed in vivo within days of adoptive transfer. These cells were predominantly terminally differentiated effector-memory cells and showed the same T cell receptor variable β chain (TCRBV) -restriction as the infused cells. They offered protection from reinfection in the majority of patients.

Conclusions: These data indicate that application of cytomegalovirus-specific T cells generated by direct selection using γ-capture is both feasible and effective in a clinical environment. These simple in vitro methodologies should allow more widespread application of virus-specific T cell immunotherapies.