Rapid dose-dependent Natural Killer (NK) cell modulation and cytokine responses following human rVSV-ZEBOV Ebolavirus vaccination

Abstract

The rVSV-ZEBOV Ebolavirus vaccine confers protection within days after immunization, suggesting the contribution of innate immune responses. We report modulation of rVSV-ZEBOV vaccinee blood CD56⁺ NK cell numbers, NKG2D or NKp30 surface receptor expression, Killer Immunoglobulin-like Receptor (KIR)⁺ cell percentages and NK-cell-related genes on day 1 post immunization. Inverse correlations existed between the concentration of several plasma cytokines and inhibitory KIR⁺ CD56^dim or cytokine-responsive CD56^bright NK cells. Thus, NK cells may contribute to the early protective efficacy of rVSV-ZEBOV in humans.

Keywords: Innate immunity; Live attenuated vaccines; Vaccines.

Fig. 1. rVSV-ZEBOV modulation of CD56⁺ lymphocyte subsets.

a Study summary of volunteers injected with high (HD) or low dose (LD) of rVSV-ZEBOV, or placebo (P). b Dot plots depict representative HD vaccinee PBMCs at baseline, gate values indicate cohort-wide % of pre-gated singlet, non-debris, leukocytes ± SD, followed by positive selection of either total leukocytes (dark blue gate), or non-granulocyte “lymphocyte”-like (light blue gate) followed by CD56^bright or CD56^dim NK cell selection. c−e Absolute number of c total NK cells (combined CD56^bright and CD56^dim NK cells), d CD56^bright NK and e CD56^dim NK cells. Violin plot symbols (open circles) show the intra-vaccinee net ratio compared to the baseline values (dashed lines), as well as median (thick red line), and interquartile (thin red line) values, shaded vaccine doses; (black squares) HD, (gray squares) LD, (open squares) placebo, and enclosed shaded horizontal width indicates the probability of obtaining the corresponding y-axis value. A one sample t test compared days 1, 3, or 7 to baseline ratio values with an expected value of 1. f Targeted sequencing was used to determine the average day 1, 3, and 7 to baseline fold change for genes in BTM LI.M61.0 “enriched in NK cells (II)” in HD vaccinees, indicated by the color scale, and compared using the edgeR glmtreat command with Benjamini−Hochberg multiple testing corrections. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.

Fig. 2. Modulation of NK cell-related surface markers and soluble proteins within the first week of rVSV-ZEBOV vaccination.

a Cytometry contour plots of the indicated cell subsets, colored as indicated, from a representative HD vaccinee at baseline showing vaccine-modulated surface markers after gating as described in Fig. 1a. The indicated KIR⁺ subset gates are shown as open rectangles with values of cohort-wide % of total NK cells ± SD, and control cells represent total leukocytes from unstained samples. b−e Fold change analysis of CD56^dim NK cells compared to the baseline, depicted and compared with statistics as described for the violin plots in Fig. 1, using the geometric MFI of surface markers b NKG2D, c NKp30, or percentages of d KIR2DL1⁺ or e KIR3DL1/S1⁺ cells within the CD56^dim NK cell gate. f Two-tailed Pearson analysis comparing the indicated NK cell phenotypic parameters with plasma cytokine concentrations from matched vaccinees, all on day 1 post vaccination. Pearson r values were calculated using a 95% CI. *P < 0.05, **P < 0.01, ***P < 0.001.