Evaluating the immune responses of mice to subcutaneous immunization with Helicobacter pylori urease B subunit

Helicobacter pylori, a gram-negative bacterial pathogen that expresses a strong urease activity, is associated with the development of gastroduodenal disease. Urease B subunit, one of the two structural subunits of urease, was expressed in E. coli BL21 (DE3) strain. The objective of this study was to evaluate the effects of Helicobacter pylori urease B subunit on the immune responses in mice by subcutaneous immunization.

The mice were immunized and boosted with Helicobacter pylori urease B subunit antigen subcutaneously three times with 2-wk intervals between the immunizations and boosters. The mice in the control group were immunized with PBS. The adjuvant group received PBS containing complete/incomplete freund's adjuvant identical to antigen group without Helicobacter pylori urease B subunit antigen. Four weeks after the final booster, all the mice were sacrificed. Blood was collected on d 0, 14, 28 and 56 before immunization, booster and sacrifice, respectively. Immediately after sacrifice, gastric liquid and spleen were collected for antibody and cytokine analyses.

Urease B subunit increased the concentrations of serum and gastric anti-urease B antigen specific IgG, and the levels of interleukin-4 and interferon-γ in splenocytes of the mice (P < 0.05).

This study demonstrated that recombinant urease B subunit can induce systemic and local immune responses in mice by subcutaneous immunization, which might be used as the effective component of vaccine against Helicobacter pylori.