Cytomegalovirus-Infected Primary Endothelial Cells Trigger NKG2C+ Natural Killer Cells.

Among innate cells, natural killer (NK) cells play a crucial role in the defense against cytomegalovirus (CMV). In some individuals, CMV infection induces the expansion of NKG2C+ NK cells that persist after control of the infection. We have previously shown that KIR2DL+ NK cells, in contrast to NKG2C+ NK cells, contribute to controlling CMV infection using a CMV-infected monocyte-derived dendritic cell (MDDC) model. However, the nature of CMV-infected cells contributing to the expansion of the NKG2C+ NK cell subset remains unclear. To gain more insight into this question, we investigated the contribution of NKG2C+ NK cell activation by CMV-infected primary human aortic endothelial cells (EC) isolated from kidney transplant donors, which constitutively express the human leukocyte antigen (HLA)-E molecule. Here, we show that, although classic HLA class I expression was drastically downregulated, nonclassic HLA-E expression was maintained in CMV-infected EC. By comparing HLA expression patterns in CMV-infected EC, fibroblasts and MDDC, we demonstrate a cell-dependent modulation of HLA-E expression by CMV infection. NKG2C+ NK cell degranulation was significantly triggered by CMV-infected EC regardless of the nature of the HLA-E allele product. EC, predominantly present in vessels, may constitute a privileged site for CMV infection that drives a 'memory' NKG2C+ NK cell subset.

Djaoud Z ，Riou R ，Gavlovsky PJ ，Mehlal S ，Bressollette C ，Gérard N ，Gagne K ，Charreau B ，Retière C ... -  《-》

Amplified NKG2C+ NK cells in cytomegalovirus (CMV) infection preferentially express killer cell Ig-like receptor 2DL: functional impact in controlling CMV-infected dendritic cells.

Djaoud Z ，David G ，Bressollette C ，Willem C ，Rettman P ，Gagne K ，Legrand N ，Mehlal S ，Cesbron A ，Imbert-Marcille BM ，Retière C ... -  《-》

Latent cytomegalovirus infection enhances anti-tumour cytotoxicity through accumulation of NKG2C+ NK cells in healthy humans.

Cytomegalovirus (CMV) infection markedly expands NKG2C+/NKG2A- NK cells, which are potent killers of infected cells expressing human leucocyte antigen (HLA)-E. As HLA-E is also over-expressed in several haematological malignancies and CMV has been linked to a reduced risk of leukaemic relapse, we determined the impact of latent CMV infection on NK cell cytotoxicity against four tumour target cell lines with varying levels of HLA-E expression. NK cell cytotoxicity against K562 (leukaemia origin) and U266 (multiple myeloma origin) target cells was strikingly greater in healthy CMV-seropositive donors than seronegative donors and was associated strongly with target cell HLA-E and NK cell NKG2C expression. NK cell cytotoxicity against HLA-E transfected lymphoma target cells (221.AEH) was ∼threefold higher with CMV, while NK cell cytotoxicity against non-transfected 721.221 cells was identical between the CMV groups. NK cell degranulation (CD107a(+) ) and interferon (IFN)-γ production to 221.AEH cells was localized almost exclusively to the NKG2C subset, and antibody blocking of NKG2C completely eliminated the effect of CMV on NK cell cytotoxicity against 221.AEH cells. Moreover, 221.AEH feeder cells and interleukin (IL)-15 were found to expand NKG2C(+) /NKG2A(-) NK cells preferentially from CMV-seronegative donors and increase NK cell cytotoxicity against HLA-E(+) tumour cell lines. We conclude that latent CMV infection enhances NK cell cytotoxicity through accumulation of NKG2C(+) NK cells, which may be beneficial in preventing the initiation and progression of haematological malignancies characterized by high HLA-E expression.

Bigley AB ，Rezvani K ，Shah N ，Sekine T ，Balneger N ，Pistillo M ，Agha N ，Kunz H ，O'Connor DP ，Bollard CM ，Simpson RJ ... -  《-》

Modulation of the natural killer cell KIR repertoire by cytomegalovirus infection.

Patients carrying activating killer cell immunoglobulin-like receptor (KIR) genes are significantly protected from CMV-associated complications after solid organ or hematopoietic stem cell transplantation. Whether previous infection with CMV affects NK-cell function in healthy donors is unknown. We studied the KIR repertoire and alterations of KIR expression after in vitro exposure to CMV in 54 healthy donors. The expression of neither activating nor inhibitory KIRs was different at baseline between 23 seropositive and 31 seronegative donors. However, after co-culture of NK cells with CMV-infected fibroblast cells, expression of the inhibitory receptors KIR2DL1 and KIR2DL3 and the activating receptor KIR3DS1 significantly increased in CMV-seropositive donors. In CMV-seronegative donors, changes were subtle and restricted to the subset of NK cells expressing NK-cell group antigen 2C (NKG2C). Expansion of inhibitory KIRs occurred exclusively in donors carrying the cognate HLA class I ligands, whereas the presence of the putative ligand HLA-Bw4 was not necessary for the expansion of KIR3DS1-expressing NK cells. Our data show that previous infection with CMV does not alter the resting NK-cell receptor repertoire, but appears to modify how NK cells respond to re-exposure to CMV in vitro.

Charoudeh HN ，Terszowski G ，Czaja K ，Gonzalez A ，Schmitter K ，Stern M ... -  《-》

Relationship of NKG2C Copy Number with the Distribution of Distinct Cytomegalovirus-Induced Adaptive NK Cell Subsets.

CD94/NKG2C and lack of FcεRγ (FcRγ) expression are considered markers of the adaptive NK cell response to human CMV (HCMV) infection. Despite the fact that FcRγ(-) and NKG2C(bright) NK cells share some phenotypic, epigenetic, and functional features, their relationship remains unclear. To address this issue, a systematic analysis of NKG2C(bright) and FcRγ expression was carried out in NK cells from a cohort of healthy young adults (n = 81) considering NKG2C copy number, previously related to the magnitude of NKG2C(+) NK cell expansion. NKG2C(bright) and FcRγ(-) NK cells coincided in a subgroup of HCMV(+) individuals, pointing to a common host-virus interaction pattern. Even though FcRγ loss was often confined to expanded NKG2C(bright) NK cells, both markers appeared occasionally dissociated, consistent with the existence of distinct adaptive NK cell subsets. Remarkably, FcRγ loss was mostly accumulated within the NKG2C(bright) subset in NKG2C(+/+) subjects, whereas NKG2C(-)FcRγ(-) NK cell subpopulations were more frequently detected in NKG2C(+/del) donors and also in NKG2C(del) (/del) individuals, independently of activating killer Ig-like receptor expression. The distribution of other NK receptors (i.e., killer Ig-like receptor, LILRB1, or CD57) supported a sequential differentiation from NKG2C(bright)FcRγ(+) to NKG2C(bright)FcRγ(-) NK cells. Noticeably, NKG2C(bright) NK cells produced more TNF-α in response to Ab-dependent activation, regardless of their FcRγ levels. Moreover, the TNF-α response of NKG2C(-)FcRγ(-) subpopulations was lower than that of concurrent NKG2C(bright)FcRγ(-) NK cells, further supporting that FcRγ levels and enhanced potential for cytokine production are uncoupled. Overall, our data extend the characterization of adaptive NK cell subsets that differentiate in response to HCMV, supporting a relationship between their distribution and NKG2C copy number.

Muntasell A ，Pupuleku A ，Cisneros E ，Vera A ，Moraru M ，Vilches C ，López-Botet M ... -  《-》