Single cell transcriptomes from HCMV +donors reveal a unique NKG2C Highsubset that represents true memory NK cells

Abstract

Abstract Infection with human cytomegalovirus (HCMV) can result in severe morbidity and mortality to the developing fetus and immunocompromised individuals. Natural killer (NK) cells are cytotoxic lymphocytes that are required to manage and control HCMV infections. The NKG2C receptor expressed by NK cells recognizes and responds to infected cells expressing HLA-E loaded with HCMV UL40-derived peptide. These responding NKG2C +NK cells have been referred to as ‘adaptive NK’ because they possess features of adaptive immunity and are found at greater percentages in HCMV seropositive individuals. The molecular mechanisms by which adaptive NK cells are generated and their transcriptomic signatures remain unknown. To investigate this, we obtained healthy adult spleens from four HCMV +and four HCMV −donors and their NK cells were sorted and captured for single-cell RNA-sequencing (scRNA-seq). Donor median age was 59 [IQR 48.5–56.5], 50% (n=4) were female, 50% (n=2) of females were HCMV seropositive and 50% (n=2) of females were HCMV seronegative. Using scRNA-seq, we observed elevated expression and cell numbers of NKG2C in HCMV +donors when compared to HCMV-donors. We identified a distinct population of NKG2C +adaptive NK cells displaying elevated levels of CD52, B3GAT1, FCGR3A, CD3E, and IL7R. In addition, our developmental trajectory analysis of adaptive NKG2C +NK cells revealed a unique branchpoint of true memory NK cells expressing elevated levels of NKG2C and IL7R. Here, we demonstrate that HCMV infection can induce the formation of adaptive NKG2C +NK cells that display a unique transcriptional and developmental profile. These findings have the potential to influence the future application of adaptive NK cells in cellular immunotherapies. This work is supported by the National Center for Advancing Translational Sciences, National Institutes of Health, through grant number TL1TR001437