Targeting Antigens to Dec-205 on Dendritic Cells Induces Immune Protection in Experimental Colitis in Mice

Abstract

The endocytotic c-type lectin receptor DEC-205 is highly expressed on immature dendritic cells. In previous studies, it was shown that antigen-targeting to DEC-205 is a useful tool for the induction of antigen-specific Foxp3(+) regulatory T cells and thereby can prevent inflammatory processes. However, whether this approach is sufficient to mediate tolerance in mucosal tissues like the gut is unknown. In this study, we established a new mouse model in which the adoptive transfer of naive hemagglutinin (HA)-specific CD4(+)Foxp3(-) T cells into VILLIN-HA transgenic mice leads to severe colitis. To analyze if antigen-targeting to DEC-205 could protect against inflammation of the gut, VILLIN-HA transgenic mice were injected with an antibody-antigen complex consisting of the immunogenic HA110-120 peptide coupled to an α-DEC-205 antibody (DEC-HA) before adoptive T cell transfer. DEC-HA-treated mice showed significantly less signs of intestinal inflammation as was demonstrated by reduced loss of body weight and histopathology in the gut. Strikingly, abrogated intestinal inflammation was mediated via the conversion of naive HA-specific CD4(+)Foxp3(-) T cells into HA-specific CD4(+)Foxp3(+) regulatory T cells. In this study, we provide evidence that antigen-targeting to DEC-205 can be utilized for the induction of tolerance in mucosal organs that are confronted with large numbers of exogenous antigens.

Keywords: DEC-205; antigen-targeting; experimental colitis; inflammatory bowel disease; regulatory T cells.

Fig. 1.

Adoptive transfer of HA-specific CD4⁺Foxp3^– T cells into VILLIN-HA transgenic mice leads to severe intestinal inflammation. HA-specific CD4⁺Foxp3^– T cells were FACS-sorted from spleens of TCR-HA/Foxp3-GFP mice (a) and were adoptively transferred into VILLIN-HA transgenic mice or nontransgenic littermates. Mice were monitored daily for signs of sickness, i.e., body weight (b). On day 6 post cell transfer, histopathological analysis of colonic sections was performed (c). Scale bars represent 50 μm. Representative data from one out of three independent experiments with similar results are shown as means ± SEM. Statistical analysis was performed using Student’s t test (^***p < 0.001)

Fig. 2.

Antigen-targeting to DEC-205 leads to less severe histopathology in the colon of VILLIN-HA transgenic mice. VILLIN-HA transgenic mice were injected i.p. twice with DEC-HA, GL117-HA, or PBS, followed by adoptive transfer of HA-specific CD4⁺Foxp3^– T cells (a). Mice were monitored for 6 days for body weight (b) and clinical signs of sickness. On day 6 post cell transfer, histopathological analysis of the colons was performed (c). Scale bars represent 50 μm. Data from three independent experiments are shown as means ± SEM. Statistical analysis was performed using one-way ANOVA (^***p < 0.001)

Fig. 3.

IFN-γ and TNF-α expression in the colon of VILLIN-HA transgenic mice is significantly reduced after DEC-HA treatment. HA-specific CD4⁺Foxp3^– T cells were adoptively transferred into DEC-HA-, GL117-HA- or PBS-treated VILLIN-HA transgenic mice. On day 6 post cell transfer, quantitative real-time PCR analysis for IFN-γ and TNF-α was performed of colon biopsies and normalized to the expression of the house keeping gene RPS-9. Data from three independent experiments are shown as means ± SEM. Statistical analysis was performed using one-way ANOVA (*p < 0.05; **p < 0.01, ***p < 0.001)

Fig. 4.

DEC-HA treatment leads to the de novo generation of Foxp3⁺ Treg in VILLIN-HA transgenic mice. HA-specific CD4⁺Foxp3^– T cells were adoptively transferred into DEC-HA-, GL117-HA-, or PBS-treated VILLIN-HA transgenic mice. On day 6 posttransfer, spleens, MLN, and cells of the colonic lamina propria (LP) were analyzed by flow cytometry for the expression of the transgenic TCR and intracellular Foxp3. Data from three independent experiments are shown as means ± SEM. Statistical analysis was performed using one-way ANOVA (^**p < 0.01; ^***p < 0.001)