Background <p><i>Trichinella spiralis</i> adult excretory-secretory antigen (<i>Ts</i>AES) has been proposed as a potential immunomodulator capable of promoting naïve T cell differentiation into peripheral regulatory T cells (pTregs). This study aims to investigate the effects of <i>Ts</i>AES on pTreg development and evaluate its role in alleviating dextran sulfate sodium (DSS)-induced acute colitis.</p> Methods <p>Colonic lamina propria mononuclear cells (LPMC) from Foxp3^eGFP mice were cultured with interleukin-2 (IL-2) and <i>Ts</i>AES for 3&#xa0;days. The frequency of CD4⁺CD25⁺Foxp3⁺ Treg cells was quantified by flow cytometry. Foxp3^eGFP mice subsequently received intraperitoneal injections of <i>Ts</i>AES (20&#xa0;µg/mouse) biweekly for a total of three doses. On day 8 post-model induction, mice were euthanized and colonic tissues collected for immunofluorescence and flow cytometric analysis to assess pTreg populations. Splenic CD4⁺ T cells and dendritic cells (DCs), isolated from Foxp3^eGFP mice using magnetic beads, were cultured with IL-2 in either <i>Ts</i>AES or phosphate buffered saline for 72&#xa0;h. The content of IL-10 in culture supernatant was measured by an enzyme-linked immunosorbent assay (ELISA), and CD4⁺Foxp3⁺ Treg cells were sorted and adoptively transferred (40,000 cells/mouse) via tail vein injection into C57BL/6&#xa0;J mice, followed by DSS administration to induce acute colitis. Body weight was monitored daily, and disease activity index (DAI) was calculated based on fecal characteristics. On day 8, mice were sacrificed, and colons were dissected and subjected to hematoxylin and eosin staining for histopathology study, and flow cytometry was performed to evaluate splenic Treg proportions.</p> Results <p>Flow cytometry analysis demonstrated that <i>Ts</i>AES stimulation promoted LPMC differentiation into Tregs, leading to a significant increase in pTregs within the colonic lamina propria of <i>Ts</i>AES-immunized Foxp3^eGFP mice. Although no significant differences in body weight were observed between Treg-infused and non-infused groups, the Treg-infused cohort exhibited a significantly lower DAI. Histological examination showed reduced inflammatory cell infiltration and better-preserved crypt architecture in the colons of Treg-treated mice. The ELISA results showed an elevated IL-10 level in <i>Ts</i>AES-treated splenocytes, and flow cytometric analysis confirmed the presence of Tregs in the spleens of recipient mice following adoptive transfer.</p> Conclusions <p><i>Ts</i>AES demonstrates tumor growth factor-beta-like activity, driving pTreg differentiation and suppressing DSS-induced colitis with IL-10 upregulation. These findings highlight a beneficial clinical effect of helminth-derived antigens on the immunomodulation and management of inflammatory bowel disease.</p> Graphical Abstract <p></p>