Human herpesvirus 6B immediate-early I protein contains functional HLA-A*02, HLA-A*03, and HLA-B*07 class I restricted CD8⁺ T-cell epitopes

Human herpesvirus 6B (HHV-6B) is a ubiquitous pathogen with frequent reactivation observed in immunocompromised patients such as BMtransplant (BMT) recipients. Adoptive immunotherapy is a promising therapeutic avenue for the treatment of opportunistic infections, including herpesviruses. While T-cell immunotherapy can successfully control CMV and EBV reactivations in BMT recipients, such therapy is not available for HHV-6 infections, in part due to a lack of identified protective CD8⁺ T-cell epitopes. Our goal was to identify CD8⁺ T-cell viral epitopes derived from the HHV-6B immediate-early protein I and presented by common human leukocyte Ag (HLA) class I alleles including HLA-A*02, HLA-A*03, and HLA-B*07. These epitopes were functionally tested for their ability to induce CD8⁺ T-cell expansion and kill HHV-6-infected autologous cells. Cross-reactivity of specific HHV-6B-expanded T cells against HHV-6A-infected cells was also confirmed for a conserved epitope presented by HLA-A*02 molecule. Our findings will help push forward the field of adoptive immunotherapy for the treatment and/or the prevention of HHV-6 reactivation in BMT recipients.