A conventional beagle dog model for acute and chronic infection with Helicobacter pylori

Abstract

Helicobacter pylori has been widely recognized as an important human pathogen responsible for chronic gastritis, peptic ulcers, gastric cancer, and mucosa-associated lymphoid tissue (MALT) lymphoma. Little is known about the natural history of this infection since patients are usually recognized as having the infection only after years or decades of chronic disease. Several animal models of H. pylori infection, including those with different species of rodents, nonhuman primates, and germ-free animals, have been developed. Here we describe a new animal model in which the clinical, pathological, microbiological, and immunological aspects of human acute and chronic infection are mimicked and which allows us to monitor these aspects of infection within the same individuals. Conventional Beagle dogs were infected orally with a mouse-adapted strain of H. pylori and monitored for up to 24 weeks. Acute infection caused vomiting and diarrhea. The acute phase was followed by polymorphonuclear cell infiltration, interleukin 8 induction, mononuclear cell recruitment, and the appearance of a specific antibody response against H. pylori. The chronic phase was characterized by gastritis, epithelial alterations, superficial erosions, and the appearance of the typical macroscopic follicles that in humans are considered possible precursors of MALT lymphoma. In conclusion, infection in this model mimics closely human infection and allows us to study those phases that cannot be studied in humans. This new model can be a unique tool for learning more about the disease and for developing strategies for treatment and prevention.

FIG. 1

Histopathological findings with infected dogs. (A) HE stain of gastric mucosa at 1 week p.i. showing hyperemia and edema of the mucosal lamina propria (bar = 25 μm); (B) HE staining of antral mucosa at 1 week p.i. showing numerous polymorphonuclear granulocytes infiltrating the laminae propriae among the glands (bar = 25 μm); (C) HE stain of antral mucosa at 4 weeks p.i. showing vacuolar degeneration of the epithelium (bar = 25 μm); (D) evident epithelium damage in the antral mucosa at 4 weeks p.i. after toluidine blue staining of a semithin section (bar = 100 μm); (E) high-power magnification (bar = 12.5 μm) of the field in panel D showing some curved bacteria (arrows) close to epithelial cells which are heavily vacuolized and show loss of the apical secreting portion; (F) HE stain of a biopsy taken 8 weeks p.i. showing a characteristic lymphoplasmacytic follicle associated with chorion edema and displacement of glands (bar = 400 μm).

FIG. 2

TEM showing the ultrastructural aspect of antral mucosa 18 weeks p.i. Typical H. pylori bacteria are visible in a glandular lumen. Magnification, ×7,920.

FIG. 3

Detection of IL-8 expression by immunohistochemistry. (A and B) Representative fields of sections obtained from antral biopsies collected at 2 and 8 weeks p.i., respectively. Sections were stained with anti-IL-8 MAb and counterstained with hematoxylin. In panel A, IL-8-positive epithelial cells are indicated by arrows. Magnification, ×100.

FIG. 4

Detection of H. pylori in gastric biopsies and oropharyngeal swab specimens by PCR. (A) H. pylori DNA amplification of the cagA sequence showing the expected PCR product of 298 bp in gastric biopsies of dogs collected at 4 and 12 weeks p.i. but not in gastric samples collected before infection. (B) cagA amplification obtained in material extracted from oropharyngeal swab specimens of dogs taken at 0, 4, and 24 weeks. Lanes: M, markers; PC, positive controls; W, water.

FIG. 5

Anti-H. pylori antibody responses in infected dogs. (A) Serum IgG and IgG subclass antibody responses to H. pylori lysate. Each curve represents the mean titers at the different time points. (B) Salivary IgA and IgG antibody responses to H. pylori lysate. Each curve represents the mean titers at the different time points obtained with salivary samples diluted 1:20.