Intestinal inflammation induced by DNFB/DNS exacerbates the allergic response to ovalbumin in mice

P UTRILLA1,3, M CUETO-SOLA1, E BAILON1, N GARRIDO-MESA1, F ALGHIERI1, J RODRIGUEZ-RUIZ2, ME RODRIGUEZ-CABEZAS1,3, A ZARZUELO1,3, J XAUS2, J GÁLVEZ1,3, M COMALADA2. 1University of Granada, Department of Pharmacology, Spain, 2Institute for Research in Biomedicine (IRB), Barcelona., Macrophage Biology Group, Spain, 3University of Granada, CIBERehd, Spain

Background: Cow’s milk protein allergy (CMPA) is one of the major causes of food hypersensitivity in children. Approximately 2 to 6% of infant exhibit CMPA in the first year of life. Moreover, the infants and children with CMPA may also develop additional atopic diseases such as other food allergies, rhinitis, asthma and early atopic dermatitis. In addition, several studies suggest that CMPA during infancy could be a risk factor for the later development of inflammatory bowel disease (IBD). However, to our knowledge, there are no studies analyzing the effect of IBD on the prevalence and severity of food allergy, despite it seems clear that IBD could increase intestinal permeability to food antigens and also to generate an immune-reactive milieu in the gut.

Aims: The objective of this work is to evaluate the allergic immune response generated to an internalized food antigen (Ovalbumin; OVA) in mice which suffer an active intestinal inflammatory response.

Methods: We compare the allergic response to OVA in mice suffering an active colitis induced by the administration of DNFB/DNS (dinitrofluorobenzene/dinitrosulfonic acid) at the moment of OVA challenge. OVA sensitization in Balb/c mice was induced intragastrically with OVA (0.1 mg/ml) plus Al(OH)3 (20 mg/ml) as adjuvant (day 0). The DNFB/DNS model of intestinal inflammation was induced by sensitization in the skin with DNFB application (day 5), followed by an intrarectal challenge with DNS (day 10). 14 days after OVA sensitization, mice were challenged intraperitoneally with a 1 mg/mouse dose of OVA plus adjuvant. Allergic symptoms and inflammatory markers were evaluated in plasma, spleen and intestine. Splenocyte proliferation was evaluated by thymidine incorporation assay, and immunoglobulin (Ig) and cytokine production by ELISA. Statistical analyses were carried out with Statgraphics 5.0, with statistical significance set at p<0.05.

Results: The results obtained showed that no important differences were observed in plasmatic IgG2a or concavalin A-induced cytokine expression in splenocytes between allergic groups, independently of their colitis affectation; however, significant differences were observed in comparison to healthy non-allergic control animals. However, the concomitant colitis leads to an increased specific immune response to OVA antigen in the allergic animals. This was evidenced when measured the splenocyte proliferative index, total IgG1 and OVA-specific IgG1 levels (Table 1). Similarly, Th2 cytokine (IL-4, IL-5 and IL-10) levels both in plasma and secreted by spleen cells after induction with OVA were also increased in allergic animals suffering also an active colitis (not shown).

Table 1. Comparison of allergy parameters in colitic (OVA-DNS) and non-colitic (OVA) animals

Data are expressed as mean ± SEM. *p<0.05 vs. healthy group. # p<0.05 vs. OVA group

Conclusion: An exacerbated immune response to internalized OVA antigen is seen in animals suffering an active colitis. A fact that should be taken in consideration for potential pharmacological treatment in those subjects where both pathologies could be co-diagnosed.