Young mice expel the tapeworm Hymenolepis diminuta and are protected from colitis by triggering a memory response with worm antigen.

Infection with helminth parasites reduces the severity of concomitant inflammatory disease in adult mice. There is an alarming increase of inflammatory bowel disease (IBD) in children. It is important to determine whether helminth therapy would be of value in pediatric IBD and whether triggering immunological memory to the worm would be anticolitic. Three-week-old (young) and eight-week-old (adult) Balb/c mice were infected with H. diminuta, and infectivity and T helper 2 (Th2) immunity were assessed. Other mice received H. diminuta with or without a crude worm extract ( HdE) 28-42 days postinfection (dpi) with or without dinitrobenzene sulphonic acid [DNBS, 1.5 mg (young) or 3 mg (adults), ir], and colitis was assessed 72 h later. Infected young mice developed Th2 immunity and expelled H. diminuta; expulsion was delayed by ~2 days compared with adult mice. Colitis, as gauged by macroscopic disease and histopathology scores, was less severe in young mice infected 10 days, but not 8 days, before DNBS. Protection against DNBS-induced colitis was accompanied by an increased capacity to make interleukin (IL)-4 and IL-10. Mice infected with H. diminuta were not protected from DNBS-colitis when challenged 28 days later; however, injection of these mice with HdE coincident with DNBS resulted in less disease and increased splenic IL-4 and IL-10. Using a boost (500 μg HdE, 28 dpi) and repeat HdE (100 μg, 42 dpi) regimen with infected mice suppressed DNBS-colitis, as did adoptive transfer of splenic CD4 ⁺ T cells from infected mice with low-dose HdE challenge. Should these data translate to IBD, then helminth therapy could be of value in pediatric-onset IBD, and defining the antigen(s) that elicit antihelminth immunological memory could serve as an anticolitic approach in previously infected individuals. NEW & NOTEWORTHY This study demonstrates that juvenile mice are protected from colitis by infection with the tapeworm Hymenolepis diminuta and that using worm antigen to trigger an immunological memory response in previously infected mice can be used to limit the severity of colitis.