Carbonic Anhydrate I Epitope Peptide Improves Inflammation in a Murine Model of Inflammatory Bowel Disease.

BACKGROUND: Carbonic anhydrase I (CA I), a major cecal bacterial antigen, improves inflammatory bowel disease (IBD) symptoms in a murine model. The aim of this study was to identify the responsible epitope region within the CA I protein and evaluate its effect on inflammation using a murine IBD model. METHODS: Candidate peptides within the CA I protein sequence that interact with major histocompatibility complex class II were chosen and their immune responses were evaluated using mesentery lymph nodes (MLNs) from a CD4CD25 T-cell transfer murine colitis model. Mice were treated with regulatory dendritic cells (Reg-DCs)-pulsed CA I peptide. We assessed their clinical signs, histopathology, induction of cytokines and transcription factors, and generation of CD103CD11c dendritic cells and regulatory T cells (Tregs). RESULTS: We identified 4 candidate epitope peptides of CA I. Among these, Reg-DCs pulsed with CA I 58-73 peptide (Reg-DCsCA I 58-73) alone ameliorated colitis. Reg-DCsCA I 58-73-treated mice showed higher mRNA expression levels of forkhead box protein 3, aldehyde dehydrogenase family 1a2, transforming growth factor-ß, and interleukin (Il)10, when compared with lower mRNA expression of retinoic acid-related orphan receptor gamma and Il17a in MLNs. Compared with control mice, these mice also showed higher numbers of Foxp3CD4CD25 Tregs and CD103CD11c dendritic cells in MLNs and colon. Administration of Reg-DCsCA I 58-73 induced antigen-specific Tregs in MLNs of colitic mice. CONCLUSIONS: CA I 58-73 peptide induces antigen-specific therapeutic effect in a murine IBD model using Reg-DCs, indicating that CA I 58-73 is a candidate epitope for IBD immunotherapy.

Regulatory dendritic cells pulsed with carbonic anhydrase I protect mice from colitis induced by CD4+CD25- T cells.

Inflammatory bowel disease (IBD), which is characterized by a dysregulated intestinal immune response, is postulated to be controlled by intestinal self-antigens and bacterial Ags. Fecal extracts called cecal bacterial Ag (CBA) have been implicated in the pathogenesis of IBD. In this study, we identified a major protein of CBA related to the pathogenesis of IBD and established a therapeutic approach using Ag-pulsed regulatory dendritic cells (Reg-DCs). Using two-dimensional gel electrophoresis and MALDI-TOF mass spectrometry, carbonic anhydrase I (CA I) was identified as a major protein of CBA. Next, we induced colitis by transfer of CD4(+)CD25(-) T cells obtained from BALB/c mice into SCID mice. Mice were treated with CBA- or CA I-pulsed Reg-DCs (Reg-DCs(CBA) or Reg-DCs(CA1)), which expressed CD200 receptor 3 and produced high levels of IL-10. Treatment with Reg-DCs(CBA) and Reg-DCs(CA1) ameliorated colitis. This effect was shown to be Ag-specific based on no clinical response of irrelevant Ag (keyhole limpet hemocyanin)-pulsed Reg-DCs. Foxp3 mRNA expression was higher but RORγt mRNA expression was lower in the mesenteric lymph nodes (MLNs) of the Reg-DCs(CA1)-treated mice compared with those in the MLNs of control mice. In the MLNs, Reg-DCs(CA1)-treated mice had higher mRNA expression of IL-10 and TGF-ß1 and lower IL-17 mRNA expression and protein production compared with those of control mice. In addition, Reg-DCs(CBA)-treated mice had higher Foxp3(+)CD4(+)CD25(+) and IL-10-producing regulatory T cell frequencies in MLNs. In conclusion, Reg-DCs(CA1) protected progression of colitis induced by CD4(+)CD25(-) T cell transfer in an Ag-specific manner by inducing the differentiation of regulatory T cells.