Chitosan as an adjuvant for a Helicobacter pylori therapeutic vaccine

The aim of the present study was to delineate the therapeutic effect of a Helicobacter pylori vaccine with chitosan as an adjuvant, as well as to identify the potential mechanism against H. pylori infection when compared with an H. pylori vaccine, with cholera toxin (CT) as an adjuvant. Mice were first infected with H. pylori and, following the establishment of an effective infection model, were vaccinated using an H. pylori protein vaccine with chitosan as an adjuvant. Levels of H. pylori colonization, H. pylori‑specific antibodies and cytokines were determined by enzyme‑linked immunosorbent assay. The TLR4 and Foxp3 mRNA and protein levels were determined by reverse transcription polymerase chain reaction and immunohistochemistry, respectively. It was identified that the H. pylori elimination rate of the therapeutic vaccine with chitosan as an adjuvant (58.33%) was greater than the therapeutic vaccine with CT as an adjuvant (45.45%). The therapeutic H. pylori vaccine with chitosan as an adjuvant induced significantly greater antibody and cytokine levels when compared with the control groups. Notably, the IL‑10 and IL‑4 levels in the groups with chitosan as an adjuvant to the H. pylori vaccine were significantly greater than those in the groups with CT as an adjuvant. The mRNA expression levels of TLR4 and Foxp3 were significantly elevated in the mice that were vaccinated with chitosan as an adjuvant to the H. pylori vaccine, particularly in mice where the H. pylori infection had been eradicated. The H. pylori vaccine with chitosan as an adjuvant effectively increased the H. pylori elimination rate, the humoral immune response and the Th1/Th2 cell immune reaction; in addition, the therapeutic H. pylori vaccine regulated the Th1 and Th2 response. The significantly increased TLR4 expression and decreased CD4+CD25+Foxp3+Treg cell number contributed to the immune clearance of the H. pylori infection. Thus, the present findings demonstrate that in mice the H. pylori vaccine with chitosan as an adjuvant exerts an equivalent immunotherapeutic effect on H. pylori infection when compared with the H. pylori vaccine with CT as an adjuvant.