NKG2A-Expressing Natural Killer Cells Dominate the Response to Autologous Lymphoblastoid Cells Infected with Epstein–Barr Virus

Abstract

Epstein–Barr virus (EBV) is a human γ-herpesvirus that establishes latency and lifelong infection in host B cells while achieving a balance with the host immune response. When the immune system is perturbed through immunosuppression or immunodeficiency, however, these latently infected B cells can give rise to aggressive B cell lymphomas. Natural killer (NK) cells are regarded as critical in the early immune response to viral infection, but their role in controlling expansion of infected B cells is not understood. Here, we report that NK cells from healthy human donors display increased killing of autologous B lymphoblastoid cell lines (LCLs) harboring latent EBV compared to primary B cells. Coculture of NK cells with autologous EBV+ LCL identifies an NK cell population that produces IFNγ and mobilizes the cytotoxic granule protein CD107a. Multi-parameter flow cytometry and Boolean analysis reveal that these functional cells are enriched for expression of the NK cell receptor NKG2A. Further, NKG2A+ NK cells more efficiently lyse autologous LCL than do NKG2A− NK cells. More specifically, NKG2A+2B4+CD16−CD57−NKG2C−NKG2D+ cells constitute the predominant NK cell population that responds to latently infected autologous EBV+ B cells. Thus, a subset of NK cells is enhanced for the ability to recognize and eliminate autologous, EBV-infected transformed cells, laying the groundwork for harnessing this subset for therapeutic use in EBV+ malignancies.

The Broad Spectrum of Human Natural Killer Cell Diversity

“…Consistent with this notion, CD56 bright cNK cells represent the predominant NK cell subset in SLTs, including LNs, where they reside in the parafollicular regions in close proximity to DCs and T cells and can reciprocally interact with and modulate the activity of these cell types (Cooper et al, 2004; Fehniger et al, 2003; Ferlazzo et al, 2004a; Ferlazzo et al, 2004b). CD56 bright cNK cells were also recently shown to specifically respond to and protect against infection by the Epstein-Barr virus (EBV) in SLTs (Hatton et al, 2016; Lunemann et al, 2013). …”

Diversification of human NK cells: Lessons from deep profiling

“…Notably, primary EBV infection induces a transient decrease in CD57 expression on NKG2A + NK cells, likely due to expansion of CD57 - NK cells which either contract or acquire CD57 over time [82]. Although CD57 expression is generally considered to correlate with greater functional capacity, a CD57 - NK cell subset was identified as the predominant population that degranulates and produces IFN-γ after co-culture with latent EBV-infected lymphoblastoid cell lines (LCLs) [109]. Additionally, loss of CD62L expression is characteristic of a CD56 bright subset of tonsilar NK cells that accumulates during chronic EBV infection and restricts EBV-induced B cell transformation [110].…”

“…Primary EBV infection expands a population of early-differentiated CD56 dim NKG2A + KIR - NK cells that do not contract and gradually gain CD57 expression and lose CD62L expression over time [82,83,109,144,145]. Accumulation of this subset inversely correlates with EBV DNA levels in peripheral blood mononuclear cells (PBMCs), and is endowed with increased IFN-γ production and cytotoxic degranulation against autologous LCLs [82,109]. EBV-induced NKG2A + expansions are not limited to CD56 dim NK cells, as a distinct CD56 bright IFN-γ hi NKG2A + NK cell subset accumulates in the tonsils of EBV seropositive individuals [110].…”

“…There is an increase in NKG2D + NK cell frequency in EBV seropositive individuals, and such an increase is apparent as soon as 10 days after first EBV exposure in an in vitro model of infection [109,143,148]. NKG2D, along with NKG2A, is one marker represented on the predominant NK cell subset that produces IFN-γ and degranulates in response to coculture with EBV-infected LCLs [109]. HCV, on the other hand, appears to have a more nuanced impact on NKG2D expression by NK cells.…”

The Immune Response to Epstein Barr Virus and Implications for Posttransplant Lymphoproliferative Disorder

“…Finally, the role of NK cells in the latent phase of EBV infection, as in the context of EBV+ B cell associated PTLD, is still to be determined. Recent studies indicate that an NKG2A+2B4+CD16-NKG2C-NKG2D+ NK cell subset can mediate cytotoxicity against latently-infected, autologous LCL suggesting this subset could be a population of interest for NK-based therapies against EBV+ PTLD (34). …”