Hexon Specific T-Cells for Adoptive T-Cell Transfer as a Treatment of Adenovirus Infection after Allogeneic Stem Cell Transplantation.

Adenovirus infection (ADV) after allogeneic hematopoietic stem cell transplantation (HSCT) is an emerging pathogen causing relevant morbidity and mortality, with preponderance in children. Since a sufficient host T-cell response has been shown essential to clear the virus, diagnostic procedures for detection of virus-specific T-cells have recently developed to asses the specific cellular immune response. Furthermore adoptive immunotherapy is a new treatment option for patients with absent specific T-cell response and present systemic adenoviral infection. The possibility of an adoptive T-cell transfer depends on the availability of GMP compatible protocols and reagents. The adenoviral hexon protein was shown a immunodominant T-cell target within the viral capsid. In the present study we investigate the presence of Hexon-specific T-cell responses in HSCT donors, i.e. the availability of donors for an adoptive T-cell transfer. Secondly, the emergence of Hexon-specific T-cells in recipients post HSCT was analyzed. Thirdly, a protocol was established under GMP-conditions for adoptive T-cell immunotherapy through isolation of IFN-γ secreting T-cells after ex-vivo stimulation with the adenoviral Hexon protein. This procedure resulted in a mixed population of CD4 and CD8 positive T-cells with an effector memory phenotype and Th1 cytokine pattern (n=8). Isolated Hexon-specific T-cells show a strong expansion potential in vitro as well as specific cytotoxic activity. The availability of a donor was evaluated in 76 HSCT donors. Only 17.1% of donors had no ADV-specific T-cell response and 72.4% of donors were eligible for an adoptive T-cell transfer using the presented approach. The Hexon protein was responsible for almost the complete response to ADV, since no significant difference was seen against ADV lysate and the Hexon protein. In 76% HSCT recipients Hexon directed T-cell responses were evaluated and were shown to be responsible for clearance of the viral infection. In conclusion feasibility of an adoptive T-cell transfer for the treatment of ADV infection post HSCT is shown in accordance to current GMP regulations.