IMMUNIZATION OF BALB C MICE AGAINST HELICOBACTER-FELIS INFECTION WITHHELICOBACTER-PYLORI UREASE/

Background/Aims: Because Helicobacter pylori is a potentially dangerou s human pathogen, the protective potential of oral immunization with H . pylori urease and its subunits was evaluated in an animal model. Met hods: Mice were orally immunized with H. pylori sonicate, urease, or r ecombinant 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 an imals (P = 0.031 vs. sham-immunized). Twelve days after challenge, ure ase B-immunized mice had a weaker colonization than sham-immunized con trols, whereas urease A had no effect. After 70 days, most urease A- a nd urease B-immunized mice had cleared the colonization (10/17: P = 0. 0019; 16/20: P = 0.00002 vs. sham-immunized). In urease B-immunized an imals, protection was often associated with corpus gastritis. Conclusi ons: Oral immunization with H. pylori urease protects mice against H. felis infection. Enzymatically inactive urease A and B subunits contai n protective epitopes. It is unclear whether protection depends on the development of a mononuclear inflammatory response in the gastric cor pus. Our observations should encourage the development of a human vacc ine.