Evaluation of Therapeutic Efficacy of Adjuvant Helicobacter pylori Whole Cell Sonicate in Mice with Chronic H. pylori Infection

Successful prophylactic administration of Helicobacter pylori whole cell sonicate (WCS) plus complete Freund's adjuvant (CFA) or aluminum hydroxide (ALM) against subsequent H. pylori infection was reported recently. Here we tested the effect of WCS plus TiterMax® Gold (TMX) or ALM in mice with chronic H. pylori infection. Mice with chronic (18 weeks) H. pylori infection were injected intraperitoneally with H. pylori (Sydney strain) WCS plus ALM or TMX once weekly for three times. The number of colonizing H. pylori in the stomach, IgG1 and IgG2a levels, and local inflammatory status were determined after therapeutic immunization. H. pylori specific IgG1, but not IgG2a, was significantly induced in mice immunized with H. pylori WCS plus TMX or ALM. Immunization did not result in reduction of bacterial count or recruiting inflammatory cells to the stomach. Adjuvant H. pylori WCS resulted in induction of CD4⁺ Th2 cell-mediated immunity although it did not reduce bacterial density in mice with chronic H. pylori infection. Our results implied that CD4⁺ Th1 cell-mediated immunity, rather than Th2 cell dominant immunity, might play a role in reducing the number of bacteria in chronic H. pylori infection.