Lymphocyte reconstitution appears to play a crucial role in clearance of HAdV viremia and survival of the host, warranting further development of therapeutic interventions aimed at improving immune recovery.

A, B, and C). This cross-reactivity of Ad-specific T cells has relevance both for Ad-based gene therapy protocols, as well as for the feasibility of T-cell-mediated adoptive immunotherapy in recipients of an allogeneic stem cell transplantation.

The online version of this article has a Supplementary Appendix. BackgroundHuman adenovirus can cause morbidity and mortality in immunocompromised patients after allogeneic stem cell transplantation. Reconstitution of adenovirus-specific CD4 + T cells has been reported to be associated with sustained protection from adenovirus disease, but epitope specificity of these responses has not been characterized. Since mainly CD4 + T cells and no CD8 + T cells specific for adenovirus have been detected after allogeneic stem cell transplantation, the relative contribution of adenovirus-specific CD4 + and CD8 + T cells in protection from adenovirus disease remains to be elucidated. Design and MethodsThe presence of human adenovirus hexon-specific T cells was investigated in peripheral blood of pediatric and adult allogeneic stem cell transplant recipients, who showed spontaneous resolution of disseminated adenovirus infection. Subsequently, a clinical grade method was developed for rapid generation of adenovirus-specific T-cell lines for adoptive immunotherapy. ResultsClearance of human adenovirus viremia coincided with emergence of a coordinated CD8 + and CD4 + T-cell response against adenovirus hexon epitopes in patients after allogeneic stem cell transplantation. Activation of adenovirus hexon-specific CD8 + and CD4 + T cells with a hexon protein-spanning peptide pool followed by interferon-γ-based isolation allowed rapid expansion of highly specific T-cell lines from healthy adults, including donors with very low frequencies of adenovirus hexon-specific T cells. Adenovirus-specific T-cell lines recognized multiple MHC class I and II restricted epitopes, including known and novel epitopes, and efficiently lysed human adenovirus-infected target cells. ConclusionsThis study provides a rationale and strategy for the adoptive transfer of donor-derived human adenovirus hexon-specific CD8 + and CD4 + T cells for the treatment of disseminated adenovirus infection after allogeneic stem cell transplantation.Key words: allogeneic stem cell transplantation, adoptive immunotherapy, adenovirus infection, adenovirus-specific T cells.Citation: Zandvliet ML, Falkenburg JH, van Liempt E, Lankester AC, Kalpoe JS, Kester MG, van der Steen DM, van Tol MJ, Willemze R, Guchelaar HJ, Schilham MW, and Meij P. Combined CD8 + and CD4 + adenovirus hexon-specific T cells associated with viral clearance after stem cell transplantation as treatment for adenovirus infection. Haematologica 2010;95(11):1943-1951. doi:10.3324/haematol.2010

The immune response against human adenovirus (HAdV) has gained interest because of the application of HAdV-based vectors in gene therapy and the high incidence of infections in pediatric recipients of allogeneic stem cell grafts. Because antiviral medication is frequently ineffective, the option of adoptive transfer of HAdV-specific donor-derived T cells in these immunocompromised patients is investigated. To generate good manufacturing practice-compatible reagents, a panel of 63 long, overlapping, peptides of the hexon protein was screened for recognition by T cells. Five conserved peptides of 30 amino acids were identified that were recognized by the majority of adult donors. CD4 + T cells from long-term cultures of PBMC, stimulated with this set of five peptides, recognized cells infected with HAdV serotypes belonging to different species. These data demonstrate that adult human T cells preferentially recognize conserved sequences of amino acid residues from a structural protein of HAdV. In the context of gene therapy, this observation may limit the beneficial effect of switching to HAdV-based vectors derived from less common serotypes of HAdV in an attempt to circumvent pre-existing immunity. However, this cross-reactivity benefits the application of HAdV-specific T cells for adoptive immunotherapy in immunocompromised transplant recipients.

Summary:Human adenoviruses (HAdV) are a frequent cause of potentially fatal infections in patients after allogeneic stem cell transplantation, especially in children. Monitoring of serum/plasma by real-time quantitative PCR is a sensitive tool for the recognition of patients at risk of a potentially fatal infection and for the evaluation of the efficacy of treatment. Data from a retrospective study and from a prospective study demonstrate that recovery of immunity after transplantation is essential for the elimination of HAdV infection. The feasibility of several approaches for the manipulation of immunity in the immunocompromised host to prevent a fatal course of the infection is discussed. Bone Marrow Transplantation (2005) 35, S73-S76.