Cytomegalovirus (CMV) infection in patients receiving hematopoietic stem cell transplants (HSCT)is associated with morbidity and mortality. Adoptive T cell immunotherapy has been used to treat viral reactivation but is hardly feasible in high-risk constellations of CMV-positive HSCT patients and CMV-negative stem cell donors. We endowed human effector T cells with a chimeric immunoreceptor (cIR) directed against CMV glycoprotein B. These cIR-engineered primary T cells mediated antiviral effector functions such as cytokine production and cytolysis. This first description of cIR-redirected CMV-specific T cells opens up a new perspective for HLA-independent immunotherapy of CMV infection in high-risk patients.Primary infection by human cytomegalovirus (CMV) and reactivation of latent virus are major problems after hematopoietic stem cell transplantation (HSCT), resulting in inflammation of a wide range of organs, systemic disease, and an increased rate of graft-versus-host disease (GvHD) (3,5,21). Antiviral chemotherapy with nucleoside analogs is used prophylactically and preemptively in the early phase after transplantation, but long-term treatment is often associated with toxicity, selection of resistant virus variants, and the inability to prevent all CMV-associated complications (4,7,28). Sustained control of latent CMV infection depends on the restoration of a functional antiviral immune response (15,25).Adoptive T cell transfer has been used successfully to bridge the critical phase of delayed or insufficient antiviral response in patients with immune suppression. In CMV and Epstein-Barr virus (EBV) infection, the adoptive transfer of ex vivo-expanded, donor-derived, virus-specific T cells reduced virus titers in the recipient to levels similar to those in immunocompetent, healthy, seropositive controls (10,23,29,31). Ex vivo expansion of these cells can be carried out by different procedures (9). In naïve seronegative persons, however, virus-specific T cells occur at very low frequencies, generally insufficient for expansion.As an alternative, T cells can be grafted with defined specificities using recombinant immunoreceptors (11). The receptor specificity is determined by extracellular single-chain fragments of the variable region (scFv) that recognize predefined antigens and can easily be altered by selecting an appropriate scFv (16). Recombinant immunoreceptors have been successfully developed against a number of tumor antigens (16) but against only a few viral proteins from HIV and hepatitis B virus (6,20,22) and not against CMV.In human CMV infection, the analysis of the physiological cytotoxic T lymphocyte (CTL) response has been focused on a limited set of proteins, namely, the proteins pp65, IE1, and IE2; recent and more extensive studies have shown that glycoprotein B (gB) as well as other CMV glycoproteins is also able to evoke adaptive T cell responses (32, 34). Notably, the CMV gB is expressed at the cell surface during the early or delayed early phase of CMV replication, even in the presence of ...