Summary
Objectives: Epidemiological surveys have shown that the incidence of inflammatory bowel disease (IBD) is relatively high in developed countries but relatively low in countries with poor sanitation and dense populations. Good hygiene and low parasitic infections increase the susceptibility of individuals to IBD. The goal of the present study was to assess the immune characteristics of hosts infected with Trichinella spiralis(T. spiralis ) and the relationship between intestinal worms and IBD. The ability of T. spiralis infection to ameliorate the effects ofCitrobacter rodentium(C. rodentium ) in a mouse IBD animal model was assessed, and the possible immunological mechanism associated with this prevention and treatment of IBD was evaluated.
Materials and Methods: In the present study, 36 male BALB/c mice aged 6-8 weeks were randomly divided into four groups: the control group (PBS), the T. spiralis infection group (TS), the C. rodentium -induced colon inflammation model group (CR) and the T. spiralis pre-infected and C. rodentium induced colitis group (TS+CR). The mice were sacrificed 7 and 14 days after the establishment of the model. The changes in various colitis indicators were used to investigate the effect of T. spiralis infection on the C. rodentium -induced mouse CD model.
Results: The results showed that the weight, DAI score, and macroscopic and microscopic colon damage in the TS+CR group was significantly decreased compared with that observed in the CR group. Flow cytometry results revealed that T. spiralis infection could reduce the expression of IFN-γ, IL-17 and IL-12 and increase that of IL-4 and IL-10 in colitis mice. Compared with that observed in the control group, the number of CD4+CD25+Foxp3+regulatory T cells (Tregs) in the spleens and mesenteric lymph nodes (MLNs) of mice in the TS group was increased (P <0.01). Compared with that observed in the TS group mice, the expression of CD4+CD25+Foxp3+Tregs in the spleens and MLNs of the TS+CR group mice was decreased (P <0.05). ELISA results revealed that compared with the control group, the TS group produced a strong IgG1 response (P <0.001) and low level of IgG2a response (P >0.05), while increased expression of IgG2a in serum was detected in the CR group mice (P <0.05).
Conclusion: The results of the present study demonstrated thatT. spiralis -infected mice induced balanced Th2 immune responses that balanced Th1 immune responses stimulated by C. rodentium to ameliorate intestinal inflammation.
Key words: Trichinella spiralis ; Citrobacter rodentium ; inflammatory bowel disease