Ex vivo generation of cytotoxic T lymphocytes specific for one or two distinct viruses for the prophylaxis of patients receiving an allogeneic bone marrow transplant

Human adenovirus (AdV) infection and EBV-lympho-proliferative disease (LPD) are serious complications following allogeneic stem cell transplantation. In the healthy individual these viruses cause minor, self-limiting diseases but in the immunocompromised patient they are responsible for significant morbidity and mortality. The limitations of anti-viral drugs and a better understanding of the cellular immune response to viral pathogens have prompted interest in developing adoptive immunotherapy for transplant patients. Ex vivo expanded cytotoxic T lymphocytes (CTLs) specific for EBV have been used effectively both as prophylaxis against EBV-LPD and as treatment of established EBV⁺ lymphoma. To generate CTLs specific for AdV, we infected immature dendritic cells with virus, in the presence of lipid, and subsequently used these cells to stimulate PBMNCs. Cytotoxicity assays showed that the resulting CTLs specifically lysed AdV-expressing targets and that this was mediated predominantly by CD4⁺ T cells. To generate CTLs specific for both AdV and EBV, we developed a CD40 ligand co-culture system to infect B-lymphoblastoid cell lines (LCLs) with high efficiency. PBMNCs from healthy AdV-seropositive donors were stimulated weekly with autologous AdV⁺-LCLs. Chromium release assays demonstrated that the resultant CTLs had specificity against both EBV and AdV and that this was mediated by both CD4⁺ and CD8⁺ T cells. Our findings have potential implications for post-transplant AdV and EBV immunotherapy in recipients of allogeneic stem cell transplants.