Adenoviral Penton and Hexon Proteins Are Equivalent Immunogenic Targets of Virus-Specific T Cells after Hematopoietic Stem Cell Transplantation in Children.

Human adenovirus (HAdV) infection is a serious complication that can lead to significant morbidity and mortality, especially in immunocompromised pediatric patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT). Control and elimination of HAdV requires the presence of the respective antiviral T cells, and adoptive transfer of virus-specific T cells has become an important new treatment option for patients refractory to antiviral treatment. Although the adenoviral capsid protein hexon is known to be a major immunodominant T cell target across HAdV species, up to 30% of HAdV-seropositive donors show no T cell responses to the overlapping peptide pool spanning the entire protein. Our group recently verified the capsid protein penton as a second immunodominant target in HAdV infection. Here we aimed to investigate the prevalence of both penton-specific and hexon-specific HAdV T cells and their impact in virus control after HSCT. We analyzed the prevalence and characteristics of HAdV-specific T cells in 33 consecutive pediatric patients with HAdV reactivation following allogeneic HSCT and correlated them with viral load analysis. Our study demonstrates that penton is an important immunodominant target antigen of HAdV reactivation/ infection after HSCT in most patients. We demonstrate that in the majority of patients, both penton- and hexon-specific T cells appear at similar time intervals after transplantation. Despite the prevalence for either hexon-specific or penton-specific T cells in individual patients, we were unable to attribute the predominance to specific HLA types or HAdV serotypes. The occurrence of HAdV-specific T cells was closely linked to viral control, arguing for immune monitoring strategies to tailor antiviral treatment and adoptive T cell therapy.