Reversal of experimental colitis disease activity in mice following administration of an adenoviral IL-10 vector

Abstract

Genetic deficiency in the expression of interleukin-10 (IL-10) is associated with the onset and progression of experimental inflammatory bowel disease (IBD). The clinical significance of IL-10 expression is supported by studies showing that immune-augmentation of IL-10 prevents inflammation and mucosal damage in animal models of colitis and in human colitis. Interleukin-10 (IL-10), an endogenous anti-inflammatory and immunomodulating cytokine, has been shown to prevent some inflammation and injury in animal and clinical studies, but the efficacy of IL-10 treatment remains unsatisfactory. We found that intra-peritoneal administration of adenoviral IL-10 to mice significantly reversed colitis induced by administration of 3% DSS (dextran sulfate), a common model of colitis. Adenoviral IL-10 (Ad-IL10) transfected mice developed high levels of IL-10 (394 +/- 136 pg/ml) within the peritoneal cavity where the adenovirus was expressed. Importantly, when given on day 4 (after the induction of colitis w/DSS), Ad-IL10 significantly reduced disease activity and weight loss and completely prevented histopathologic injury to the colon at day 10. Mechanistically, compared to Ad-null and DSS treated mice, Ad-IL10 and DSS-treated mice were able to suppress the expression of MAdCAM-1, an endothelial adhesion molecule associated with IBD. Our results suggest that Ad-IL10 (adenoviral IL-10) gene therapy of the intestine or peritoneum may be useful in the clinical treatment of IBD, since we demonstrated that this vector can reverse the course of an existing gut inflammation and markers of inflammation.

Figure 1

IL-10 concentration in lavage fluids from the transfected peritoneum. ELISA measurement of IL-10 in peritoneal lavage fluids from control shows a very high level of expression of IL-10 at approximately 400 pg/ml. No IL-10 was detected in lavage fluids of control or adeno-null mice (n = 5).

Figure 2

Disease activity in mice with experimental colitis given adenoviral IL-10 gene. Disease activity in mice in which experimental colitis was induced by feeding 3% DSS was significantly attenuated at days 7–10 when adenoviral administration of IL-10 was given on day 6. Disease activity in control mice continued at the same level as the adeno-null mice on DSS. Disease activity was slightly higher in adeno-null mice which was significant at day 8, suggesting that adenoviral infection produces some inflammation. This is important to note since Ad-IL-10 still promotes protection despite the tendency towards higher inflammation.

Figure 3

Body weight of mice in DSS colitis. Adeno-IL-10 mice did not lose any body weight over the course of DSS colitis, but adeno-null mice lost significantly more weight than adeno-IL-10 transfected mice (n = 5).

Figure 4

Adeno-IL-10 blocks colon shortening induced by DSS colitis. Adenoviral IL-10 adminstration significantly reduced the colon shortening produced by 3% DSS colitis (n = 5).

Figure 5

Colon histology for adenoviral transfected mice given DSS colitis. Figure 5A shows control colons with normal histopathology, 5B shows extensive regional leukocytic infiltration of the colon; see inset. This leukocyte infiltration is completely absent in adenoviral IL-10 treated mice which show normal or even improved morphology.

Figure 6

Analysis of histopathology in adenoviral transfected DSS colitis model. Compared to control mice, adeno-null treated mice exhibited significantly worse histopathology; whereas adeno-IL-10 treated mice had completely normal histology.

Figure 7

Adenoviral IL-10 reduces MAdCAM-1 expression in experimental colitis. Figure 7A (control) shows only sporadic and weak staining for MAdCAM-1. Figure 7B shows intense MAdCAM-1 staining in adeno-null + DSS-treated colon sections, unlike Adeno-IL10 + DSS-treated sections (Figure 7C) which lack strong MAdCAM staining, and much more closely resemble controls.