While Helicobacter pylori is accepted as the dominant human gastric bacterial pathogen, a small percentage of human
infections have been associated with another organism, commonly referred to as 'Helicobacter heilmannii', which is more prevalent in a range of animal species. This latter bacterium has been seen in association with the full spectrum of human
gastric diseases including
gastritis, peptic ulceration, and gastric
carcinomas, including gastric B-cell mucosa-associated lymphoid tissue (
MALT) lymphoma. This study describes an analysis of the pathogenic potential of a number of 'H heilmannii' isolates in an animal model of gastric
MALT lymphoma. BALB/c mice were infected with ten different 'H heilmannii' isolates originating from both human and animal hosts. The animals were examined at various time points for up to 28 months after
infection. The infected animals initially developed a chronic inflammatory response within 6 months. This histological response increased in severity with the length of
infection, with the development of overt
lymphoma in some animals 18 months after
infection.
MALT lymphomas were detected in up to 25% of the infected animals. The prevalence of
lymphoma was dependent on the length of
infection and the origin of the infecting isolates. A range of other histological features accompanied the lymphocytic infiltration, including invaginations of the gastric epithelium and associated hyperplastic tissue, mucus
metaplasia, and a small number of diffuse large
B-cell lymphomas. The ability to manipulate experientially the presence of the bacterium in the animal model will allow further studies examining the role of
antigen drive in the development of Helicobacter-associated
MALT lymphoma.