The molecular mechanisms by which adjuvants enhance immune responses to pandemic influenza vaccines are poorly understood. We evaluated transcriptomic responses in human immune cells to H5N1 vaccine administered with or without Adjuvant System 03 (AS03).
Healthy subjects aged 18-49 years received two 3.75 mcg doses of subvirion inactivated influenza A/H5N1 virus vaccine with either AS03 (n=10) or saline (PBS; n=10). Blood samples were obtained on Days -28, -14, 0 (pre-vaccination), 1, 3, 7, and 28 relative to first vaccination for transcriptomic profiling of six immune cell types: neutrophils, B and T lymphocytes, monocytes, dendritic cells (DC), and natural killer cells (NK). 25 million, 50 BP, paired-end sequencing was performed on RNA from each cell type at each time point. Differentially-expressed (DE) genes between treatment groups were identified, with p-value adjustment for multiple comparisons. Genes with a false-discovery rate value ² 0.05 and fold change of ³1.5 (up or down) between treatments were considered DE.
Most variation was driven by cell type, with distinct clusters for lymphocytes/NK, DC/monocytes, and neutrophils (Figure 1). Monocytes, DC, and neutrophils showed many DE genes at Day 1 post-vaccination with 80 DE genes shared by all three cell types. B and T lymphocytes exhibited increased responses at Day 1 as well, albeit with fewer DE genes. With the exception of neutrophils at Day 3, few genes had significant differences in log fold-changes between treatments at Day 3, 7, or 28. NK demonstrated a distinct pattern with weak responses at Day 1 and moderate responses at Days 3 and 28. At Day 1, subjects tended to cluster by treatment group based on log fold changes of DE genes at any post-vaccination day (Figure 2). Except for NK, subject clustering by treatment became weaker over time, indicating that the effect of adjuvant on gene expression responses rapidly declined.
Transcriptional profiling of immune cells after vaccination reveals distinct signatures in the early immune response to AS03-adjuvanted compared to non-adjuvanted vaccine. Application of this approach may offer new insights into the mechanisms of immune responses to influenza vaccines and oil-in-water adjuvants.
* Howard, Hoek, and Goll contributed equally to this work.
J. Goll, None
P. Samir, None
A. Galassie, None
C. B. Creech, None
N. Prasad, None
T. Jensen, None
H. Hill, None
S. Joyce, None
K. Edwards, None
A. Link, None