GLA-SE, a synthetic toll-like receptor 4 agonist, enhances T-cell responses to influenza vaccine in older adults

Abstract

Background: The decline in influenza vaccine efficacy in older adults is associated with a limited ability of current split-virus vaccines (SVVs) to stimulate cytotoxic T lymphocyte (CTL) responses required for clinical protection against influenza.

Methods: The Toll-like receptor 4 agonist glucopyranosyl lipid adjuvant-stable emulsion (GLA-SE) was combined with SVV to stimulate peripheral blood mononuclear cells (PBMCs) in vitro to determine the cytokine response in dendritic cell subsets. Stimulated PBMCs were then challenged with live influenza virus to mimic the response to natural infection following vaccination, using previously identified T-cell correlates of protection.

Results: GLA-SE significantly increased the proportion of myeloid dendritic cells that produced tumor necrosis factor α, interleukin 6, and interleukin 12. When combined with SVV to stimulate PBMCs in vitro, this effect of GLA-SE was shown to regulate a T-helper 1 cell response upon challenge with live influenza virus; interleukin 10 production was suppressed, thus significantly increasing the interferon γ to interleukin 10 ratio and the cytolytic (granzyme B) response to influenza virus challenge, both of which have been shown to correlate with protection against influenza in older adults.

Conclusions: Our findings suggest that a novel adjuvant, GLA-SE, combined with standard SVV has the potential to significantly improve vaccine-mediated protection against influenza in older adults.

Figure 1.

Glucopyranosyl lipid adjuvant–stable emulsion (GLA-SE) increased the percentage of myeloid dendritic cells (mDCs) expressing interleukin 6 (IL-6; A), tumor necrosis factor α (TNFα; B), or interleukin 12 (IL-12; C). Peripheral blood mononuclear cells were treated for 6 hours with GLA-SE or polyinosinic:polycytidylic acid (poly I:C), with or without split-virus vaccine (SVV), and intracellular cytokine staining (ICS) was used to determine the proportion of mDCs expressing these cytokines. Mean proportions of ICS-positive mDCs are shown for each of the conditions (samples are from 6 young subjects and 6 older subjects). Box plots show median values and interquartile ranges, and error bars represent the range of values. P values indicate the levels of significance in nonparametric comparisons.

Figure 2.

Glucopyranosyl lipid adjuvant–stable emulsion (GLA-SE) enhanced the split-virus vaccine (SVV)–mediated increase in granzyme B (GrzB) activity in response to live influenza virus challenge. Peripheral blood mononuclear cells (PBMCs) were cultured with GLA-SE or polyinosinic:polycytidylic acid (poly I:C), with or without SVV, for 5 days, followed by challenge with live influenza virus for 20 hours. Mean levels of GrzB activity measured in PBMC lysates are shown (young subjects, n = 11; old subjects, n = 14). Error bars represent the standard error of the mean. P values indicate the levels of significance in nonparametric comparisons.

Figure 3.

Glucopyranosyl lipid adjuvant–stable emulsion (GLA-SE) significantly reduced the split-virus vaccine (SVV)–mediated increase in the interleukin 10 (IL-10) response to influenza virus challenge, increasing the ratio of interferon γ (IFN-γ) to IL-10. Peripheral blood mononuclear cells (PBMCs) were cultured with GLA-SE or poly I:C, with or without SVV, for 5 days, followed by challenge with live influenza virus for 20 hours. Mean IFN-γ (A) and IL-10 (B) levels and the IFN-γ:IL-10 ratio (C) in PBMC culture supernatants (young subjects, n = 11; old subjects, n = 14) are shown. Error bars represent the standard error of the mean. P values indicate the levels of significance in nonparametric comparisons.