Modulation of the Th1/Th2 bias by lipopeptide and saponin adjuvants in orally immunized mice

We compared the adjuvanticity of the synthetic lipopeptide P3CSK4 of bacterial origin and the plant-derived adjuvant saponin using the wheat storage protein gliadin as antigen. Gluten sensitive BALB/c mice were orally immunized with gliadin in a mixture with either lipopeptide or saponin. The gliadin-specific serum IgG response was markedly enhanced by the saponin adjuvant. The lipopeptide adjuvant enhanced the IgG2a response, but reduced IgG1 production. In contrast, the saponin adjuvant enhanced both IgG2a and IgG1, and the sera showed elevated specific IgE concentrations. Enhanced specific IgA levels were detected in sera and in faeces especially after immunizations with gliadin in combination with P3CSK4 Enhanced specific IgG and IgA levels could also be detected in supernatants of cell cultures prepared from mesenteric lymph nodes and Peyer's patches of immunized mice. Our data suggest that both adjuvants enhance the mucosal as well as the systemic immune response; P3CSK4 predominantly elicits the activation of the Th1 subset, whereas saponin activates both the Th1 and Th2 subser. Our findings are of importance for the improvement of mucosal immunizations, and might be a tool for the immunotheraphy of food allergies.