Trichinella spiralis - induced modulation of IFN-γ and TGF-β shapes host immunity to support chronic infection

Trichinella spiralis is a widely prevalent foodborne helminth that establishes chronic infection through modulation of host immunity. This study investigated the temporal dynamics of interferon-γ (IFN-γ), transforming growth factor-β (TGF-β), and intestinal TGF-β receptor II expression during experimental infection and examined their relationship to parasite burden and tissue pathology. Forty Swiss albino mice were orally infected with 250-300 larvae and sacrificed at 3, 7, 14, and 28 days post-infection. Adult worms and muscle larvae were quantified, serum cytokines measured by ELISA, and intestinal TGF-β receptor II expression evaluated immunohistochemically. Adult worm burden peaked at 7 dpi and declined sharply thereafter, with clearance by 28 dpi. Muscle larvae accumulated progressively, reaching ~1 × 10⁴ larvae/mouse at 28 dpi. IFN-γ peaked at 7 dpi then declined, while TGF-β increased steadily and remained elevated during the muscle phase. A significant negative correlation was observed between IFN-γ and TGF-β (r = -0.42, p=0.012). TGF-β receptor II expression was up-regulated at 3-14 dpi and declined by 28 dpi. Histopathology revealed pronounced intestinal inflammation at 7-14 dpi with restoration by 28 dpi, while skeletal muscle displayed nurse cell-larva complexes. Findings demonstrate a coordinated shift from early IFN-γ-mediated inflammation to sustained TGF-β-driven regulation, supporting parasite persistence and limiting tissue injury.