DOP083 Recombinant subcutaneous human beta-Defensin 2 (hBD2) ameliorates experimental colitis in different in vivo models

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Abstract

Background: In recent years, the significance of antimicrobial peptides for the maintenance of epithelial barriers has been recognized and various diseases have been associated with compromised antimicrobial barrier function. Of note, colonic Crohn's disease has been related to an attenuated induction of human beta defensin 2 (hBD2) in the colon. In addition to their antimicrobial activity, defensins also have important immune-modulatory functions. Here, we screened hBD2 for potency and toxicity and produced this peptide using a microbial expression system. Furthermore, we tested its preclinical efficacy using different in vivo models of colitis.

Methods: We established a cellular expression-system, Saccharomyces cerevisiae, to produce sufficient amounts of hBD2 for in vivo screening and determined its antimicrobial activity in vitro. Next, we tested hBD2 for cytotoxicity in human PBMCs and in murine fibroblasts and assessed its anti-inflammatory properties in human PBMCs stimulated with LPS. Finally, we tested hBD2 in different mouse models of colitis using subcutaneous (s.c.) application. We used DSS (dextran sulfate sodium, n=10), TNBS (Trinitrobenzenesulfonic acid, n=15) and T-cell transfer from wild-type into SCID mice to induce colitis (n=11). To test the protective effect of hBD2, animals were treated once a day by s.c. injection of a dose range of 0.1–3 mg/kg.

Results: We obtained a yield of >400 mg/L of hBD2 on a 10 L scale. HBD2 showed antimicrobial activity in radial diffusion assays while we did not find any cytotoxic effect against human PBMCs and murine fibroblasts. Treatment of LPS-activated human PBMCs with hBD2 decreased the release of pro-inflammatory TNFalpha, IL-1β and IL-23 while upregulating anti-inflammatory IL-10 and IL-24. In all colitis models tested s. c. application of hBD2 led to a remarkable improvement of disease at an optimal dose of 0.1 mg/kg (DSS and TNBS) and 1 mg/kg (transfer) on par with anti-TNFalpha (DSS), prednisolone (TNBS) and dexamethasone (transfer), respectively. In the DSS model hBD2 ameliorated loss of body weight (p<0.05), improved the disease activity index (p<0.001) as well as the histological score (p<0.001), significantly. In the TNBS model the histological score was significantly improved by hBD2 treatment (p<0.001) while in the T-cell-transfer model hBD2 again improved the disease activity index.

Conclusions: We were able to produce and purify hBD2 in relevant amounts. Since hBD2 showed no cytotoxicity, strong anti-inflammatory properties and protected mice from colitis our data provided evidence that hBD2 could be used as potential therapeutic agent in the treatment of inflammatory bowel diseases.

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