Effects of TLR agonists on immune responses in Trichinella spiralis infected mice

Human trichinellosis is acquired by eating raw or undercooked meats carrying muscle larvae of Trichinella spp. Toll-like receptors (TLRs) are essential components of the innate immune system. However, little is known about the potential application of TLR agonists for immunotherapy against Trichinella spiralis (T. spiralis) infection. Here, we evaluated the effects of four TLR agonists (i.e., TLR3, TLR4, TLR8, and TLR9 agonists) on T. spiralis infection in mice. The reduction rate of worm burden showed that TLR3 agonist poly(I:C) significantly reduced T. spiralis infection rather than TLR4, TLR8, and TLR9 agonists (p < 0.05). Moreover, TLR3 showed a continuous high-level of expression during 6–35 days post infection (dpi). The levels of interferon-gamma (IFN-γ), interleukin (IL)-2, and IL-6 increased significantly in mice serum compared with control group after treatment with TLR3 agonist at 0, 3, 6, 9, 12, 15, 18, 21, 28, and 35 dpi (p < 0.05). A significant decreasing trend was also detected in levels of IL-10 and IL-4 after treatment with TLR3 agonist compared with control group at 0, 3, 6, 9, 12, 15, 18, 21, 28, and 35 dpi (p < 0.05). Overall, this study suggested that TLR3-targeted therapies might be effective on worm burden reduction by regulation of the cytokine levels in the mice infected with T. spiralis.