Mouse Models for Assessing the Protective Efficacy of Lactobacillus gasseri SBT2055 against Helicobacter suis Infection Associated with the Development of Gastric Mucosa-Associated Lymphoid Tissue Lymphoma

Background: Helicobacter suis strain TKY infection has been strongly associated with the development of gastric mucosa-associated lymphoid tissue (MALT) lymphoma in a C57BL/6J mouse model. Materials and Methods: 1. C57BL/6J mice were intragastrically administered Lactobacillus strains once daily with 10⁸-10⁹ colony-forming units (CFU), starting 2 days before intragastric infection with H. suis TKY (approximately 1 × 10⁴ copies of 16S rRNA genes) or H. pylori Sydney strain 1 (SS1; 3 × 10⁸ CFU) and continuing for 14 days after infection. 2. C57BL/6J mice were given powdered feed mixed with lyophilized L. gasseri SBT2055 (LG2055) cells (5 × 10⁸ CFU/g), starting 2 weeks before intragastric infection with H. suis TKY and continuing 12 months after infection. Results: 1. Among the 5 Lactobacillus strains that we examined, only LG2055 exhibited significantly preventive efficacy against both H. suis TKY and H. pylori SS1 at day 15 after infection. 2. Dietary supplementation with LG2055 protected mice from the formation of round protrusive lesions in the gastric fundus 12 months after infection with H. suis TKY, whereas such lesions had developed in the gastric fundus of nonsupplemented mice 12 months after infection. In addition, the formation of lymphoid follicles in gastric mucus layers was suppressed by dietary LG2055 at 3 months after infection. Conclusions: LG2055 administration is effective for suppressing the progression of gastric MALT lymphoma by reducing H. suis colonization.