Ebola virus protein VP40 stimulates IL-12– and IL-18–dependent activation of human natural killer cells
Hung Le, Paul Spearman, Stephen N. Waggoner, Karnail Singh
Hung Le, Paul Spearman, Stephen N. Waggoner, Karnail Singh
View: Text | PDF
Research Article Immunology Infectious disease

Ebola virus protein VP40 stimulates IL-12– and IL-18–dependent activation of human natural killer cells

Abstract

Accumulation of activated natural killer (NK) cells in tissues during Ebola virus infection contributes to Ebola virus disease (EVD) pathogenesis. Yet, immunization with Ebola virus-like particles (VLPs) comprising glycoprotein and matrix protein VP40 provides rapid, NK cell–mediated protection against Ebola challenge. We used Ebola VLPs as the viral surrogates to elucidate the molecular mechanism by which Ebola virus triggers heightened NK cell activity. Incubation of human peripheral blood mononuclear cells with Ebola VLPs or VP40 protein led to increased expression of IFN-γ, TNF-α, granzyme B, and perforin by CD3–CD56+ NK cells, along with increases in degranulation and cytotoxic activity of these cells. Optimal activation required accessory cells like CD14+ myeloid and CD14– cells and triggered increased secretion of numerous inflammatory cytokines. VP40-induced IFN-γ and TNF-α secretion by NK cells was dependent on IL-12 and IL-18 and suppressed by IL-10. In contrast, their increased degranulation was dependent on IL-12 with little influence of IL-18 or IL-10. These results demonstrate that Ebola VP40 stimulates NK cell functions in an IL-12– and IL-18–dependent manner that involves CD14+ and CD14– accessory cells. These potentially novel findings may help in designing improved intervention strategies required to control viral transmission during Ebola outbreaks.

Authors

Hung Le, Paul Spearman, Stephen N. Waggoner, Karnail Singh

×

Figure 3

Degranulation and cytotoxic function of NK cells are enhanced by exposure to Ebola VLPs.

Options: View larger image (or click on image) Download as PowerPoint
Degranulation and cytotoxic function of NK cells are enhanced by exposur...
PBMCs were stimulated with or without Ebola VLPs as in Figure 2. Cells were stained for the surface and cytotoxicity markers and data acquired and analyzed as described in Methods. Only single and live CD3–CD56+ NK cells were included in the analysis. Representative dot blots (A) and the corresponding summary data from 11 independent experiments performed with PBMCs from 11 (24 and 48 hours) or 5 (6, 72, and 96 hours) independent donors (B) showing NK cells’ degranulation (CD107a surface expression) are shown. (C–F) Representative histograms for intracellular granzyme B (C) and perforin (E) expression in gated CD3–CD56+ NK cells from PBMC cultures stimulated with Ebola VLPs (black) for 48 hours are shown. NK cells from PBMCs left unstimulated are shown in gray. Dotted histograms represent corresponding isotype controls. D (granzyme B) and F (perforin) show corresponding summary data from 8 independent experiments performed with PBMCs from 8 independent donors. (G) ADCC killing of target cells mediated by either unexposed (gray circles) or Ebola VLP exposed (black circles) PBMCs. PBMCs exposed to Ebola VLPs for 48 hours were analyzed for their cytotoxic potential by mixing them with the target cells expressing EBOV GP and in the presence of anti-EBOV GP plasma. Combined data from 5 independent experiments with PBMCs from 5 donors are shown. Results are shown as mean ± SEM. **P < 0.01, ***P < 0.001, as calculated by 2-tailed paired Student’s t test.