Gastric Helicobacter infection inhibits development of oral tolerance to food antigens in mice

Abstract

The increase in the transcellular passage of intact antigens across the digestive epithelium infected with Helicobacter pylori may interfere with the regulation of mucosal immune responses. The aim of this work was to study the capacity of Helicobacter infection to inhibit the development of oral tolerance or to promote allergic sensitization and the capacity of a gastro-protective agent, rebamipide, to interfere with these processes in mice. Oral tolerance to ovalbumin (OVA) was studied in 48 C3H/He 4-week-old mice divided into four groups: (i) OVA-sensitized mice; (ii) OVA-"tolerized" mice (that is, mice that were rendered immunologically tolerant); (iii) H. felis-infected, OVA-tolerized mice; (iv) and H. felis-infected, OVA-tolerized, rebamipide-treated mice. Oral sensitization to hen egg lysozyme (HEL) was studied in 48 mice divided into four groups: (i) controls; (ii) HEL-sensitized mice; (iii) H. felis-infected, HEL-sensitized mice; and (iv) H. felis-infected, HEL-sensitized, rebamipide-treated mice. Specific anti-OVA or anti-HEL immunoglobulin E (IgE) and IgG1/IgG2a serum titers were measured by enzyme-linked immunosorbent assay. Additionally, the capacity of rebamipide to interfere with antigen presentation and T-cell activation in vitro, as well as absorption of rebamipide across the epithelial monolayer, was tested. H. felis infection led to the inhibition of oral tolerance to OVA, but rebamipide prevented this inhibitive effect of H. felis. H. felis infection did not enhance the sensitization to HEL, but rebamipide inhibited the development of this sensitization. Moreover, rebamipide inhibited in a dose-dependent manner antigen presentation and T-cell activation in vitro and was shown to be able to cross the epithelium at a concentration capable of inducing this inhibitory effect. We conclude that H. felis can inhibit the development of oral tolerance to OVA in mice and that this inhibition is prevented by rebamipide.

FIG. 1.

Specific anti-OVA serum IgE (A) and IgG (B) titers (mean ± SD [error bars]). OVA-sensitized mice present significantly higher IgE and IgG titers than OVA-tolerized mice and mice treated with rebamipide. H. felis-infected OVA-tolerized mice present significantly higher IgE titers than OVA-tolerized mice, reflecting the inhibition of the development of oral tolerance by H. felis. Symbols: *, significantly different from groups II (P < 0.03) and IV (P < 0.04); §, significantly different from groups II (P < 0.01) and IV (P < 0.05); n, number of mice studied.

FIG. 2.

Specific anti-OVA serum IgG1 (A) and IgG2a (B) titers (mean + SD [error bars]). OVA-sensitized mice present significantly higher IgG1 titers than OVA-tolerized mice or mice treated with rebamipide. H. felis-infected and OVA-tolerized mice present nonsignificantly different IgG1 titers from those presented by noninfected OVA-tolerized mice. No significant differences are found in IgG2a titers among the groups. *, significantly different from groups II (P < 0.01) and IV (P < 0.002); n, number of mice studied.

FIG. 3.

Specific anti-HEL IgE (A) and IgG (B) titers (mean + SD [error bars]) in sera from mice. (A) Symbols: *, significantly different from groups I (P < 0.004) and IV (P < 0.002); §, significantly different from groups I (P < 0.04) and IV (P < 0.04). (B) Symbols and abbreviations: *, significantly different from group I (P < 0.03); §, significantly different from group I (P < 0.004); n, number of mice studied.

FIG. 4.

Dose-dependent inhibitory effect of rebamipide on T-cell activation (IL-2 secretion) in an in vitro model of antigen presentation (mean + SD [error bars]; n = 8). Symbols and abbreviations: * and §, significantly different from controls (*, P < 0001; §, P < 0.004); NS, nonsignificant difference; n, number of experiments for each set of conditions (concentration).

FIG. 5.

Apical-to-basal rebamipide fluxes (JReb) across HT29-19A intestinal monolayers mounted in Ussing chambers (mean + SD [error bars]). n = number of measurements for each time point.