Inhibitory NKG2A+ and absent activating NKG2C+ NK cell responses are associated with the development of EBV+ lymphomas

Abstract

Epstein-Barr virus (EBV) is a ubiquitous herpesvirus, which infects over 90% of the adult human population worldwide. After primary infections, EBV is recurrently reactivating in most adult individuals. It is, however, unclear, why these EBV reactivations progress to EBV⁺ Hodgkin (EBV⁺HL) or non-Hodgkin lymphomas (EBV⁺nHL) only in a minority of EBV-infected individuals. The EBV LMP-1 protein encodes for a highly polymorphic peptide, which upregulates the immunomodulatory HLA-E in EBV-infected cells, thereby stimulating the inhibitory NKG2A-, but also the activating NKG2C-receptor on natural killer (NK) cells. Using a genetic-association approach and functional NK cell analyses, we now investigated, whether these HLA-E-restricted immune responses impact the development of EBV⁺HL and EBV⁺nHL. Therefore, we recruited a study cohort of 63 EBV⁺HL and EBV⁺nHL patients and 192 controls with confirmed EBV reactivations, but without lymphomas. Here, we demonstrate that in EBV⁺ lymphoma patients exclusively the high-affine LMP-1 GGDPHLPTL peptide variant-encoding EBV-strains reactivate. In EBV⁺HL and EBV⁺nHL patients, the high-expressing HLA-E*0103/0103 genetic variant was significantly overrepresented. Combined, the LMP-1 GGDPHLPTL and HLA-E*0103/0103 variants efficiently inhibited NKG2A+ NK cells, thereby facilitating the in vitro spread of EBV-infected tumor cells. In addition, EBV⁺HL and EBV⁺nHL patients, showed impaired pro-inflammatory NKG2C⁺ NK cell responses, which accelerated the in vitro EBV-infected tumor cells spread. In contrast, the blocking of NKG2A by monoclonal antibodies (Monalizumab) resulted in efficient control of EBV-infected tumor cell growth, especially by NKG2A⁺NKG2C⁺ NK cells. Thus, the HLA-E/LMP-1/NKG2A pathway and individual NKG2C⁺ NK cell responses are associated with the progression toward EBV⁺ lymphomas.

Keywords: EBV - Epstein-Barr virus; EBV+ lymphoma; HLA-E polymorphism; LMP-1; NK cells; NKG2A; NKG2C NK cells; immune evasion.