Reactions from rat gastric mucosa during one year of Helicobacter pylori infection.

The aim of the present study was to investigate responses from the gastric mucosa of rats during long-term H. pylori infection. Twenty-four Sprague-Dawley rats were inoculated with a mouse-adapted strain of human H. pylori (vacA+, cagA+), 16 uninfected rats served as controls. Three to six rats from each group were killed two weeks or two, six, or 12 months later. At sacrifice, blood was sampled and the gastric mucosa was taken for bacterial culture, histology, immunocytochemistry and in situ hybridization. H. pylori colonized the antrum in 23/24 inoculated rats; with time the density of bacteria increased. The inflammation in the antral mucosa was mild to moderate and was dominated by infiltration of lymphocytes and macrophages. Serum H. pylori-specific IgG2a was significantly increased in the infected rats. The frequency of epithelial cell apoptosis was significantly increased in the early months of infection. The mucosal expression of trefoil peptide mRNA remained unchanged. We conclude that after one year of H. pylori infection in rats, the mucosal responses were rather mild, indicating that the animals may adapt to the infection by mechanisms which remain to be identified.