GASTRITIS IN UREASE-IMMUNIZED MICE AFTER HELICOBACTER-FELIS CHALLENGEMAY BE DUE TO RESIDUAL BACTERIA

Background & Aims: Oral immunization with recombinant Helicobacter pyl ori urease (rUre) coadministered with a mucosal adjuvant protects mice against challenge with Helicobacter foils, In this study, the duratio n of protection and gastritis after challenge were characterized at se quential time intervals up to 1 year, Methods: Outbred Swiss-Webster m ice were orally immunized with rUre plus adjuvant and examined for the presence of H. foils infection and leukocyte infiltration into the ga stric: mucosa, Results: When defined by gastric urease activity, 70%-9 5% of rUre-immunized mice were protected for between 2 and 57 weeks. C hallenge with H. felis increased the inflammatory response Tn the gast ric mucosa of rUre-immunized mice, which also had elevated CD4(+) and CD8(+) T cells. The CD8(+) cells represented a population of gastric i ntraepithelial cells, which expressed the mucosal alpha(E)-integrin, E pithelial changes consisting of parietal cell loss and hyperplasia of the epithelium occurred in approximately 20% of the mice. Antimicrobia l triple therapy significantly decreased the degree of gastritis and e pithelial alteration in the stomach, Conclusions: These results indica te that oral immunization of mice with rUre produces a long-lasting in hibition of H. felis infection but that residual bacteria may produce a persistent lymphocytic infiltration under these experimental conditi ons.