Immunization of BALB/c mice against Helicobacter felis infection with Helicobacter pylori urease

Background/Aims: Because Helicobacter pylori is a potentially dangerous human pathogen, the protective potential of oral immunization with H. pylori urease and its subunits was evaluated in an animal model. Methods: Mice were orally immunized with H. pylori sonicate, urease, or recombinant enzymatically inactive urease subunits and then challenged with Helicobacter felis . Control mice were sham-immunized. Results: H. felis colonization was present 5 days after challenge in 9 of 10 sham-immunized, 6 of 9 sonicate-immunized, and 3 of 10 urease-immunized animals ( P = 0.031 vs. sham-immunized). Twelve days after challenge, urease B-immunized mice had a weaker colonization than sham-immunized controls, whereas urease A had no effect. After 70 days, most urease A- and urease B-immunized mice had cleared the colonization (1017: P=0.0019; 1620: P=0.00002 vs. sham-immunized). In urease B-immunized animals, protection was often associated with corpus gastritis. Conclusions: Oral immunization with H. pylori urease protects mice against H. felis infection. Enzymatically inactive urease A and B subunits contain protective epitopes. It is unclear whether protection depends on the development of a mononuclear inflammatory response in the gastric corpus. Our observations should encourage the development of a human vaccine.