Dendritic cell vaccination in an allogeneic stem cell recipient receiving a transplant from a human cytomegalovirus (HCMV)-seronegative donor: induction of a HCMV-specific Thelper cell response

Background aims. In the absence of a protective immune response, human cytomegalovirus (HCMV) infection remains a life-threatening complication after allogeneic stem cell transplantation (SCT), especially in recipients of grafts from HCMV-seronegative donors. After allogeneic SCT from a seronegative donor, prolonged and severe immune deficiency often leads to infectious complications. Vaccination with antigen-loaded dendritic cells (DC) has been shown to be a potent approach for the induction of antigen-specific cytotoxic T-cell responses in vivo. For protection from subsequent HCMV reactivation, a sustained immune response is necessary, including antigen-specific CD4(+) T cells. Methods. We report the case of an 18-year-old girl with high-risk acute lymphoblastic leukemia that received an allogeneic SCT in CR2. After an HCMV infection, the graft was rejected and she received a second transplant from an HLA-mismatched, HCMV-seronegative family donor. She was treated with pp65-pulsed monocyte-derived DC at day 200 post-SCT, using a recombinant pp65 protein. Until day 200 post-SCT, HCMV reactivated six times with emerging viral resistance to antiviral chemotherapy. Results. After vaccination with protein-pulsed DC, an induction and expansion of HCMV-specific T-helper cells and cytotoxic T lymphocytes was observed, associated with a sustained clearance of the HCMV viremia. Antiviral treatment could be tapered without recurrence of viremia within the first year post-SCT. Conclusions. pp65-pulsed DC could induce antigen-specific T-cell responses even after a SCT from an HCMV-seronegative donor. After vaccination with pp65-pulsed DC, a sustained antigen-specific T-cell response prevented concurrent HCMV viremia. Emergence of antigen-specific T-helper cells may be essential for a sustained, functional T-cell response post-SCT.