Considering increased mouse stomach mass when calculating prophylactic vaccine efficacy against Helicobacter pylori

Background: Calculating the level of protection follow vaccination against Helicobacter pylori in mice is conventionally performed based on stomach mass. However, prophylactic vaccination is associated with a post-immunisation gastritis which results in considerable thickening of the gastric mucosa. Results and Conclusions: Here, an analysis of nine experiments demonstrates that this post-immunisation gastritis can actually induce a significant increase in stomach mass. To determine whether this mass increase impacts upon the perceived level of protection, calculations were performed comparing colony-forming units (CFU) either per gram of tissue or per whole stomach. A trend was apparent towards increased stomach mass influencing the degree of protection if CFU were calculated per gram. However, as this effect was not significant, it appears valid to express CFU either per gram or per stomach (if age and gender matched mice are used).