Aluminum compounds have been used as adjuvants in practical vaccination for more than 60 years to induce an early, an efficient and a long lasting protective immunity. Nowadays they are the most widely used adjuvants in both veterinary and human vaccines. Unfortunately these adjuvants do not only cause undesirable side effects, but often induce T-helper type 2 (Th2)-biased responses. In this study we investigated the ability of the bacterial product CANTASTIM (CS) to augment the immune responses to a model antigen, tetanus toxoid (TT). Immunization of mice with TT+CS elicited higher anti-TT IgG antibody levels as compared to mice that received TT alone. Moreover, treatment with TT+CS resulted in a lower IgG1/IgG2a ratio and a stronger in vitro IFN-gamma synthesis by splenocytes and T cells cocultured with macrophages. These data suggest that CS can be used to enhance the magnitude of the immune response and to skew it towards the Th1 type.