Infection of Helicobacter pylori in rats and mice: A one year study

Abstract

AIM: To investigate the long term infection of H.pylori in the conventional laboratory rats and mice, and the serological responses of the infected-animals.

METHODS: Two strains of H.pylori (one vac positive and one vac negative) were separately isolated from two duodenal ulcer patients. The bacteria were considered as mouse-adapted strains after they have passaged through the mice 3 times serially. Groups of female BALB/c mice and Sprague-Dawley rats were separately inoculated with mouse-adapted vac⁺ or vac^-H.pylori. The animals were treated with omeprazole before and after the bacterial inoculation in order to increase the gastric pH. Then the animals were sacrificed 2 wk, 2, 6-7 or 12 mo after the bacterial inoculation. At sacrifice, blood was sampled for ELISA; mucosa from the corpus and the antrum were separately scraped off, and cultured in order to determine the colony forming units (CFUs).

RESULTS: H.pylori colonized the gastric mucosa in most of the bacteria-inoculated mice and rats, and the colonization was rather constant 2 to 12 mo after H.pylori inoculation. In the mice, CFUs were around 200/mg scraped mucosa in the antrum and were around 100/mg in the corpus. There were no differences of colonization between vac⁺ and vac^- strain s. Two mo after the bacterial inoculation, the serum level of H.pylori-specific Ig in the mice infected by vac⁺ -H.pylori was progressively and significantly increased up to 10-15 times higher than that in the uninfected controls, while was only slightly increased in the mice infected by vac^-H.pylori. In the rats, 2 to 12 mo after the bacterial inoculation, CFUs were around 1000/mg in the antrum, while only 2-52/ mg in the corpus. Serum levels of H.pylori-specific IgG2a were persistantly and significantly increased in the rats infected by vac⁺H.pylori in comparison with the uninfected controls (P < 0 .05 to < 0.001), while IgG1 in these H.pylori infected rats remained at control levels.

CONCLUSION: The conventional laboratory mice and rats can be infected by the mouse-adapted H.pylori strains. Serological response was significant in vac⁺H.pylori infected mice, but not in vac^-H.pylori-infected mice. The significantly increased serum H.pylori-specific IgG2a antibody in the rats infected by vac⁺H.pylori showed a strong predominance of an inflammatory Th1-type response.

Key Words: Helicobacter pylori; Helicobacter infection; Rats; Mice