A HCMV pp65 polypeptide promotes the expansion of CD4+ and CD8+ T cells across a wide range of HLA specificities

Abstract

Human Cytomegalovirus (HCMV) can cause life threatening disease in infected hosts. Immunization with HLA-restricted immunodominant synthetic peptides and adoptive transfer of epitope specific T cells have been envisaged to generate or boost HCMV specific cellular immunity, thereby preventing HCMV infection or reactivation. However, induction or expansion of T cells effective against HCMV are limited by the need of utilizing peptides with defined HLA restrictions. We took advantage of a combination of seven predictive algorithms to identify immunogenic peptides of potential use in the prevention or treatment of HCMV infection or reactivation. Here we describe a pp65 derived peptide (pp65(340-355), RQYDPVAALFFFDIDL: RQY16-mer), characterized by peculiar features. First, RQY-16mer is able to stimulate HCMV pp65 specific responses in both CD4+ and CD8+ T cells, restricted by a wide range of HLA class I and class II determinants. Second, RQY-16mer is able to induce an unusually wide range of effector functions in CD4+ T cells, including proliferation, killing of autologous HCMV infected target cells and cytokine production. Third, and most importantly, the RQY-16mer is able to stimulate CD4+ and CD8+ T cell responses in pharmacologically immunosuppressed patients. These data suggest that a single reagent might qualify as synthetic immunogen for potentially large populations exposed to HCMV infection or reactivation.