Exploring the Trichuris antimicrobial peptidome as a source of novel antimicrobials and opportunities for Immune modulation potentials

Abstract

Soil-transmitted helminths are found to secrete bioactive molecules , such as antimicrobial peptides (AMPs),with functions that range from antimicrobial to immunomodulatory. These molecules are thought to contribute to parasite development and survival in the host gut. In this study, a total of 66 computationally predicted AMPs were evaluated for antimicrobial and immunoregulatory activities. Antimicrobial activity (MIC and MBC) was assessed by broth microdilution, while enzyme-linked immunosorbent assay (ELISA) was used to measure cytokine responses. All tested peptides were synthetic and derived from conserved regions of the whipworm (Trichuris), an intestinal parasite of medical and economic significance. The peptides were initially identified in a previous collaborative project at Queen’s University Belfast (QUB, unpublished data).Among the tested peptides, A9 and A10 displayed broad-spectrum antimicrobial activity, while G2, A13 and A14 inhibited Gram-negative bacteria selectively. The difference between broad-spectrum and selective inhibition is noteworthy, as it may show how AMPs act on bacterial membranes or how their structures influence their function. Scanning electron microscopy (SEM) was then used to visualise morphological alterations in inhibited bacteria following peptide treatment. Although the mode of action of AMPs was not covered in this study and SEM cannot confirm the mechanism, the observed morphological deformities provide evidence that membrane integrity is compromised and is consistent with AMP action.The immunomodulatory activity was assessed in PMA-differentiated U937 macrophages after peptide treatment. Cytokine responses were then measured with ELISA, including TNF-α, IL-6 and IL-1β as pro-inflammatory mediators, and IL-10 as a regulatory mediator.For TNF-α and IL-6, most peptides increased secretion, and A10 and B18 showed the most reproducible effect. Abi-7 and Abi-11 reduced IL-1β levels. IL-10 showed variation, with A10 and G2 lowering secretion, while Abi-6–8 and Abi-10–13 induced it. A10 behaved in both ways, as it raised TNF-α but reduced IL-10. This variation may be linked to AMP structure or to differences in the host gut environment. Immune modulation was present in both pro-inflammatory and regulatory cytokines, but the signals were not consistent and need additional testing.