# A162 INTERLEUKIN-4 SIGNALING IS NOT A PREREQUISITE FOR HELMINTH-THERAPY PROTECTION AGAINST COLITIS

## TL;DR

This study shows that mice lacking IL-4 signaling can still be protected from colitis by helminth infection, with protection depending on IL-10 and macrophages.

## Contribution

The study reveals that IL-4 signaling is not essential for helminth-induced protection against colitis, with IL-10 and macrophages playing key roles.

## Key findings

- Mice lacking IL-4 signaling (il-4ra-/-) are protected from DNBS-induced colitis after helminth infection.
- Protection in il-4ra-/- mice depends on IL-10 and macrophages, as neutralizing IL-10 or depleting macrophages abolishes protection.
- Helminth-induced anti-colitic effects are redundant, allowing compensation in the absence of IL-4 signaling.

## Abstract

Infection with helminth parasites drives Th2 immunity, characterized by the cytokines IL-4, -5, -13, and IL-10, and expansion of regulatory cells. These orchestrated immune responses promote an immunomodulatory/immunosuppressive environment, which can protect the host from concomitant inflammation. Mice infected with the tapeworm Hymenolepis diminuta display a strong Th2 immune response and they are protected from DNBS-induced colitis. Surprisingly, preliminary data indicated that il-4ra-/- mice (where the worm establishes) were protected from DNBS-induced colitis. Here we sought to confirm or refute the findings in il-4ra-/- and, if positive, investigate the role of IL-10 and macrophages in the anti-colitic effect.

To determine if IL-10 and macrophages play key roles in the protection against colitis in il-4ra-/- mice infected with H. diminuta.

BALB/c (WT) and il-4ra-/- mice (IL-4ra-/-) (n=4-15/group) were orally infected with 5 cysticercoids of H. diminuta and 8 days post-infection (dpi) were treated with 2.5 mg of dinitrobenzene sulfonic acid (DNBS) to induce colitis. In some experiments, mice were treated 3 times i.p. with neutralizing anti-IL10 antibody (100 mg/mouse) or clodronate-liposomes (100 ml/mouse) to deplete macrophages (5 days and 24h before and after DNBS). Mice were necropsied 72h post-DNBS and disease was assessed through macroscopic disease activity score (DAS), colon length, weight loss, colonic MPO activity, blood leucocyte profile and histopathological score. Cytokine production by antigen-specific (H.d. antigen 200mg/mL; 48h) stimulated splenocytes was measured by ELISA.

DNBS treatment induced colitis in WT and IL-4ra-/- and prior infection with H. diminuta was anti-colitic in both groups as shown by reduced DAS, weight loss, MPO activity, and histopathology. Compared to WT, il-4ra-/- mice had less blood eosinophilia, and il-5 and il-10 production by worm-antigen stimulated splenocytes, although il-10 production was increased compared to splenocytes from uninfected control mice. Immunoneutralization of il-10 and macrophage depletion abolished the protective effects of infection with H. diminuta, with the clondronate-treated mice displaying severe disease.

Despite harbouring a patient infection with H. diminuta, il-4ra-/- mice are protected from DNBS-induced colitis that is, at least in part dependent on IL-10 and likely a phenotype of regulatory macrophage. The data suggest redundancy in the anti-colitic effects of H. diminuta infection, such that absence of il-4ra is compensated for via other, yet to be determined, mechanisms.

CAG, CIHRTRIANGLE