In vitro effects of monophosphoryl lipid A and Poly I:C combination on equine cells

ABSTRACT

Background@#Toll-like receptor (TLR) agonists have been used as adjuvants to modulate immune responses in both animals and humans. @*Objectives@#The objective of this study was to evaluate the combined effects of the TLR 4 agonist monophosphoryl lipid A (MPL) and the TLR 3 agonist polyinosinicpolycytidylic acid (Poly IC) on equine peripheral blood mononuclear cells (PBMCs), monocyte-derived dendritic cells (MoDCs), and bone marrow-derived mesenchymal stromal cells (BM-MSCs). @*Methods@#The PBMCs, MoDCs, and BM-MSCs collected from three mixed breed horses were treated with MPL, Poly IC, and their combination. The mRNA expression of interferon gamma (IFN-γ), interleukin (IL)-1β, IL-4, IL-6, IL-8, IL-12p40, tumor necrosis factor alpha (TNF-α), vascular endothelial growth factor (VEGF), and monocyte chemoattractant protein-1 (MCP-1) was determined using real-time polymerase chain reaction. @*Results@#The combination of MPL and Poly IC significantly upregulated immunomodulatory responses in equine cells/ without cytotoxicity. The combination induced greater mRNA expression of pro-inflammatory cytokines IFN-γ and IL-6 than MPL or Poly IC stimulation alone in PBMCs. In addition, the combination induced significantly higher mRNA expression of IL-1β, IL-6, and IL-12p40 in MoDCs, and IL-8, MCP-1, and VEGF in BM-MSCs compared to stimulation with a single TLR agonist. @*Conclusions@#The combination of MPL and Poly IC can be used as a potential adjuvant candidate for vaccines to aid in preventing infectious diseases in horses.