Immunohistochemical evaluation of interleukin-23 and cyclooxygenase-2 in the muscles of mice infected with Trichinella spiralis

The course of Trichinella (T.) spiralis infection includes intestinal and muscle phases. The aims of this work were to evaluate IL-23 and cyclooxygenase-2 (COX-2) by immunohistochemistry in the muscles of T. spiralis infected mice in a time-course study and to correlate their level with the serum levels of IL-23, IFN-γ, IL-4 and IL-10 cytokines. The mice were divided into an un-infected control group (UC) (10 mice) and 5 infected mouse groups (each 10 mice/group. Each mouse was infected with 200 T. spiralis larvae) and sacrificed on days 7, 14, 21, 28 and 35 post-infection (dpi). IL-23 showed weak expression (+1) on the 21st dpi, then it became moderately expressed (+2) on the 28th dpi and on day 35 pi, the immunoreactivity was strong (+3). COX-2 expressed weakly on 14 dpi, while the other mouse groups (21, 28 and 35) showed strong (+3) expression. IL-23 serum concentrations increased gradually in a significant pattern, in comparison to that of UC mice, from the 21st dpi to the end of the experiment. IFN-γ increased gradually and was significantly higher than those of UC mice from the 7th dpi, reached its maximum level on the 21st dpi, after which it decreased non-significantly. IL-4 up-regulated significantly in all infected groups in comparison to UC mice achieving its highest level on the 21st dpi and decreased after that. IL-10 increased significantly on the 7th dpi, but dropped at the 14th dpi, then reached its peak on the 21st dpi, and decreased again on the 28th and 35th dpi. In conclusion, T. spiralis infection caused increased expression of IL-23 and COX-2 in the muscle of infected mice, the effect being strongest on the 35th day. Also, the infection induced a mixed Th1/Th2 profile with a predominance of Th2 at the early muscle phase, after which the immune repose became mainly Th2.